Temporal Epidemics and Management of Ascochyta Blight (Ascochyta rabiei) on Chickpea (Cicer arietinum L.) in Central Rift Valley, Ethiopia

doi:10.21203/rs.3.rs-3123002/v1

The production of chickpea, an important legume that is grown all over the world for its nutritious fibers and minerals, is severely constrained by ascochyta blight, which can cause up to a 100% yield loss under ideal conditions. The most reliable, economical, and effective management techniques for this disease are fungicide treatments and host plant resistance. The objectives of the present study were to evaluate chickpea varieties and fungicide application intervals against chickpea ascochyta blight epidemics; identify the most effective fungicide application time interval; and determine the association of ascochyta blight incidence and severity with yield and yield component of chickpea. The study was carried out in two hotspot regions (Dhera and Dugda) during the main growing seasons of 2020 and 2021. Three chickpea varieties (Dhera, Habru, and Mariye) and four fungicide spray schedules (Mancozeb 80% WP at a rate of 2.5 a.i. kg/ha) were utilized as treatments, and they were treated up until the crop reached full physiological maturity. Twelve treatments were set up in a factorial arrangement with three replications using a randomized complete block design (RCBD). Both the Gompertz model and the logistic model were used to assess dependent variables under various treatments. For the disease progression rate under various treatments, the slope of the regression line was determined. The results of the data analysis revealed considerable variations between the treatments. Fungicide application time scheduled, varieties, and their interactions had substantial effects on ascochyta blight. The Mariye variety noted the highest occurrence (100%) and severity (70.68%) of ascochyta blight, with 100% yield loss seen from untreated plots, whereas the Dhera variety experienced the lowest incidence (6.35%) and severity (11.01%) following fungicide management on the 7th day of the interval. The analysis of the means revealed that applying fungicide at intervals of 7 and 14 days was an effective strategy for reducing the severity, incidence, and AUDPC of ascochyta blight. This strategy led to the highest yield of seeds per pod, pods per plant, and grain yield when compared to the untreated plot and the plot treated at a 21-day interval. To handle polycyclic outbreaks of the disease successfully, both the logistic and Gompertz models were used. The study's extent of variety resistance was enough to control the disease in two cropping seasons and locations. This investigation led us to the conclusion that a program to control the ascochyta blight of chickpea in Ethiopia may include the integration of fungicide and resistant varieties. Additionally, methods for integrated management of the Ethiopian ascochyta blight on chickpeas must be devised.

Chickpea

Disease incidence

percent severity index

Fungicide

Relative yield loss

The chickpea (Cicer arietinum L.), one of the most major food legumes and animal feed crops produced worldwide, is listed by Millan et al. (2006). It is a good source of carbohydrates and a high source of protein (28.9%), oil (3%), carbohydrate (60%) and minerals (magnesium, phosphorus, calcium, and iron). It is grown in more than 50 nations, with 90% of the growth being for human consumption (Joshi et al., 2001). Following India (65%) and Myanmar (14%), Ethiopia is the largest producer of chickpeas (FAOSTAT, 2018), contributing 4% to global output overall (FAO, 2019). With a national average yield of 2.14 t ha-1 (FAOSTAT, 2018), chickpea ranks third among all legume crops in Ethiopia in terms of volume of production, considerably behind its potential output of more than 5.0 t ha-1 (Zewdie, 2018). Furthermore, it can fix nitrogen into the soil, increase soil fertility, and stop the disease cycles of significant cereal pathogens (Pande et al., 2011). As a result, it is commonly planted in succession with cereals like tef (Eragrostis tef (Zucc.) Trotter) and wheat (Triticum aestivum) (Geletu and Yadeta, 1994).

The low productivity of chickpea in Ethiopia is primarily caused due to its susceptibility to a number of biotic and abiotic constraints. Among the biotic constraints, ascochyta blight, caused by Didymella rabiei, is one among the major diseases of chickpea worldwide. All of the chickpea plant's shoots are affected, resulting in lesions, shoot breakage, and the development of necrotic lesions that quickly cause tissue and plant collapse (Pande et al., 2005). When climatic factors (RH > 60%, temperature of 10–20 oC, and increased wind speed) support the epidemic's growth, it can cause up to 100% yield loss and can lower the quality of the crop on untreated and susceptible varieties (Aslam et al., 2014). Conidia may be splash-dispersed for up to 10 m from their initial foci when rain and high wind are present, which is a crucial element in the development of this disease (Trapero-Casas and Kaiser; 1992; Kimber et al. 2007). The most efficient and cost-effective way to control this disease is to use resistant cultivars, but in many countries, the level of resistance present in cultivated chickpea cultivars is insufficient to withstand high disease pressure when the environment is right for epidemic development (Akem, 1999). Fungicides must be used in a timely manner, ideally before a rain shower, to effectively control the spread of disease (Shtienberg et al., 2006). Although foliar sprays have typically been proven to be ineffectual during major outbreaks, the rate with which the disease develops when conditions are favorable can make it very difficult to implement a fungicide treatment for susceptible types (Shtienberg et al. 2000). Only in dry circumstances may fungicide treatments be decreased (Chongo et al. 2003), and even in moderate epidemics susceptible varieties may need four to six times sprays to limit the disease amount (Nene, 1982).

Therefore, the greatest long-term strategy for controlling ascochyta blight is host plant resistance (Pande et al. 2005). The national chickpea modification program of BARC (Bishoftu Agricultural Research Center) has so far issued two moderately resistant chickpea varieties (Eshete and Asnake) to the producers in Ethiopia. The implementation of ecologically based integrated disease management strategies is one of the objectives of plant disease epidemiology and management. However, only partial resistance is insufficient to manage ascochyta blight (Chongo et al. 2003), especially in nations like Ethiopia where the production of chickpeas is mostly done using a rain-fed method. In addition, there is always a chance that new pathotypes will appear and end up defeating the developing variety' resistance (Bayaa et al. 2004). In order to manage the disease, extra measures like fungicide treatments must be modified.

According to Reddy and Singh (1984) and Ahmad et al. (2006), foliar application of fungicides along with host plant resistance can control the ascochyta blight. There is a greater need to develop alternative or additional technologies which will allow a rational use of fungicides and provide adequate crop protection for sustainable chickpea production in the future (Pandey et al., 2005). Although the benefits from the use of fungicides to prevent chickpea yield losses caused by the disease cannot be overlooked. Ascochyta blight is a disease that has completely infected commercial varieties of the majority of the chickpea cultivars planted in Ethiopia.

On a variety of pulse crops, mancozeb has been successfully used to combat ascochyta blight (Shtienberg et al. 2006). Currently, Ethiopian farmers are having a difficult time increasing productivity and production of chickpeas in a sustainable manner due to the ascochyta blight. Therefore, it is essential to apply fungicide repeatedly and ascochyta blight resistant chickpea varieties. Such an integrated disease management strategy is a cheap and simple approach to manage the disease. Therefore, the objectives of the current study were to: (1) evaluate chickpea varieties and fungicide application intervals against chickpea ascochyta blight epidemics; (2) pinpoint the optimal time for fungicide application; and (3) identify the relationship between ascochyta blight incidence and severity with chickpea yield and yield component.

2.1 Description of the experimental sites

Field experiments were conducted at Dhera and Dugda, Ethiopia during 2020 and 2021 cropping seasons. Both the locations belong to Oromia regional State, which is 120 and 125 km East and South of Addis Ababa, respectively. These sites are characterized by weather conducive for ascochyta blight epidemics. Dhera is located at latitude 8^o 19’10’’ N, longitude 38^O 19’13’’ E, altitude of 1650 m.a.s.l. with average total annual rainfall of about 620 mm, minimum and maximum average annual temperatures of 14.0 and 27.8 ^OC, and the soil type is light silty-loam (KARC, 2019). Dugda is located at latitude 8^o18’24.4’’ N, longitude 38^o57’05.3’’E, altitude 1700 m.a.s.l. that receives an average annual rainfall of about 728 mm, and average annual temperature ranges from 13-27 ^OC, whereas the soil type is light black sandy loam with pH 6.4 (DZARC, 2018). The weather data while conducting experiment (August to December) in both the cropping season were also recorded and found to be ranged from 9.4 to 30.7 ^OC and 11.2 to 32.6 ^OC (Figure 1) for the sites Dhera and Dugda, respectively, which is favorable for ascochyta blight germination and epidemic development.

2.2 Planting materials and experimental design

Three chickpea varieties—Dhera, Habru, and Mariye—released by the Bishoftu Agricultural Research Center (BARC), Ethiopia, were used in the experiments. These varieties grow well at elevations between 1500 and 2600 meters above sea level with an average annual rainfall of 700 to 1300 millimeters (BARC unpublished data). In the study conducted earlier at BARC during 2016-2019 chickpea growing seasons, Mariye (Kabuli type; pedigree: FLIP 8842c) was characterized as susceptible variety whereas Habru (Desi type; pedigree: K-850-3/27x F378) and Dhera (Kabuli type; pedigree: X98TH30FLIP-93-55C XS-96231) was found to be moderately resistant and resistant, respectively (Unpublished data).

Planting of all three chickpea varieties at both the experimental sites were performed by hand seeding at the rate of 125 to 140 kg ha⁻¹ in early August (5^th to 9^th day) of 2020 and 2021 cropping seasons. The plot used for each experiment was of 1.2 m x 3 m (3.6 m²) size with 4 seeding rows. Spacing used between block, plots, rows (inter-row), and plants (intra-row) were of 1m, 0.5m, 0.4m, and 0.1m, respectively. As the experimental field plots were free of chickpea production for two years, no fertilizer was applied during chickpea cultivation of this study. Weeding was performed twice, 20- and 35-days post emergence, and all recommended agronomic practices were followed uniformly for all the plots.

2.3 Fungicide treatments for ascochyta blight management

The fungicide treatments were applied in a factorial arrangement using a randomized complete block design (RCBD), with three replications for each treatment. The study included a total of 12 treatments, including an unsprayed control, three variety of chickpea, and three different fungicide spraying intervals. Mancozeb 80% WP was sprayed at a rate of 2.5 kg/ha (active ingredient) three times, at intervals of 7, 14, and 21 days, with an unsprayed plot serving as the reference plot. Until the crop reached full physiological maturity, spraying was continued at the predetermined intervals. Plastic sheet was placed between the spraying plot and the surrounding plots to keep them apart and avoid inter-plot interference from spray drift. Starting at the seedling stage 30 days after planting and continuing through the podding stage, the plots were routinely checked for disease progression. Based on the Pande et al., (2011) scale, the symptoms and their severity were noted.

2.4 Data collection

2.4.1 Ascochyta blight incidence and severity assessment

According to Pande et al. (2010), Ascochyta blight causes tiny, circular lesions that are brown and oval lesions that are brown on the leaves and stem of affected plants. Similar symptoms were seen on the plants during the experimental trials conducted in 2020 and 2021, across the regions and seasons, which were taken into account for assessing disease incidence. Ascochyta blight incidence was initially scored as soon as the usual symptoms started to develop on the plants in the experimental plots. Scoring was then repeated every week until disease severity ceased changing and signs of normal aging became hidden. Thereafter, the percent incidence of disease (DI) was calculated using simple mathematical formula;

DI = No. of plants diseased / Total no. of plants available in the plots x 100.

Using 12 randomly chosen and pre-tagged plants per plot at intervals of 7 days, from the time the first disease signs appeared until the crop reached full physiological maturity, the severity of the disease was evaluated three to nine times. Pande et al. (2011) used the score of the selected and tagged chickpea plants to evaluate the disease severity of each variety in both the seasons and locations since ascochyta blight affects all of the plant's aerial parts, where 1, no visible symptoms; 2, minute lesions prominent on the apical stems; 3, lesions up to 5‒10 mm in size and slight drooping of apical stems; 4, lesions obvious on all plant parts and clear drooping of apical stems; 5, lesions on all plants parts, defoliation initiated, breaking and drying of branches slight to moderate; 6, lesions as in 5, defoliation, broken, dry branches common, some plants killed; 7, lesions as in 5, defoliation, broken, dry branches very common, up to 25 % of plants killed; 8, symptoms as in 7 but up to 50 % of the plants killed and 9, symptoms as in 7 but up to 100 % of the plants killed . The disease severity scores were converted to severity index (SI) for analysis using the formula of Wheeler (1969):

Further, the area under disease progress curve (AUDPC) for each plot was also calculated using the formula of Shanner and Finney (1977):

Where, Xi = the SI of disease at the i^th assessment/observation; ti = is the time of the i^thassessment in days from the first assessment date; and n = total number of disease assessments.

2.4.2 Chickpea growth, yield, and yield components

During both seasons, data pertaining to growth, yield, and yield components were gathered from each plot at each site. From 10 pre-tagged plants at each plot, the average plant height (cm) was estimated by measuring the height of the mature plant from the base to the tip. Each plot's data from the initial days to 50% flowering and 95% physiological maturity was recorded. The average number of pods from 10 randomly selected pre-tagged plants from the two center rows was used to calculate the average number of pods per plant. The average number of seeds in 10 randomly chosen pods from pre-tagged plants was used to calculate the average number of seeds per pod. Weighing the collected seeds from the two centre rows (pre-tagged plants) of each experimental plot at 14% moisture content allowed us to compute the grain yield (kg/ha). The weight of a hundred seeds was measured in grams and was taken as a representative sample of the total number of seeds gathered from each experimental plot.

2.4.3 Yield loss estimation

Using the following method from Madden et al. (2007), the relative percentage of yield and yield component losses were determined independently for each treatment:

Where, RYL (%) = percentage of relative yield loss (reduction of yield or yield components),

Y1 = mean yield of the most protected plot;

Y2 = mean yield of the unsprayed plots or sprayed plots with varying level of disease.

2.5 Data analysis

Data was evaluated and the mean disease responses for each plot's 12 plants were determined. When F values revealed significant differences, the data were submitted to analysis of variance, and Duncan's multiple-range test was applied at a 5% level of probability. ANOVA was used to examine the disease incidence, SI, AUDPC, and chickpea growth, yield, and yield components data. Using logistic (y (1-y) and Gompertzy y [-ln(y)] growth models, disease progression rate was calculated. The disease progression rate under different treatments was estimated using the slope of the regression line. The LSD was used to calculate the mean separation at the 5% confidence level.

3.1 Disease incidence and severity

During two consecutive evaluation years (2020 and 2021), the severity of ascochyta blight epidemics differed significantly (P 0.05) across chickpea varieties, and it was discovered that severe epidemics developed in both seasons. The disease was initially noticed on the Mariye variety 30 Days after Planting (DAP), then spread to the other varieties in the next plot. The varieties and fungicide spray intervals showed significant differences (Tables 1 and 3). Four to five weeks after the first signs of the disease in the unsprayed plots appeared at both locations, the disease severity in the highly susceptible varieties reached 90% (Table 3). Disease development in moderately susceptible variety was slower, but the final disease severity within the unsprayed experimental plots surpassed the 50% level. Although the final disease severity of untreated experimental plots was significant, disease development in highly resistant varieties had never exceeded 20% (Table 3).

Regarding their relative responses to the disease, Mancozeb 80% WP spray times were significantly varied regardless of fungicide treatment intervals (P 0.05). Additionally, plots demonstrated significantly different ascochyta blight severity levels (P 0.05) at all assessment dates (30, 37, 44, 51, 58, 65, 72, 79, and 86 DAP) (Table 3). The lowest average severity level of ascochyta blight was noted on the 7th day of interval fungicide treatment (from the start of ascochyta blight evaluation). Moreover, the maximum (100%) and minimum (24.54%) severity were recorded on susceptible variety (Table 3).

Although there was no statistically significant difference between the crop seasons, the minimum disease incidence and severity of 15.1% at Dhera and 11.2% at Dugda, respectively, were recorded from moderate and resistant varieties in the 7th day's interval application. Furthermore, in Dugda during the 2020 crop season, susceptible variety in untreated plots had the highest ascochyta blight incidence and severity of 99.60% and 70.7%, respectively (Tables 1 and 2). Similar to the susceptible variety, the ascochyta blight intensity was high on the 21^st day after application (Table 3); 74.1% at Dhera and 66.7% at Dugda). This suggests that compared to the Mariye variety, the Dhera and Habru varieties are more resistant to ascochyta blight.

According to the mean value of two seasons and two locations; the minimum disease incidence of 15. 1% at Dhera was recorded from resistant varieties and 7^th day’s interval application of the fungicide, while the maximum disease incidence of 91.07% at Dugda and 86.19% at Dhera was recorded from susceptible variety on unsprayed plots (Table 1). Genotype resistance had a lower disease incidence than genotype susceptibility, according to Kanouni et al. (2010), who also provided confirmation of this finding. In this investigation, the same outcomes were seen for the ascochyta blight severity index (SI) (Table 2).

Moreover, there was significant (P < 0.05) ascochyta blight incidence difference between a combinations of plots treated with 7^th, 14^th, 21^thday’s intervals and no spray of Mancozeb WP 80 % and varieties viz; Dhera, Habru and Mariye until the 9^th date of disease assessment under two seasons and locations (Table 3). For each variety, the difference in disease incidence levels was statistically (P 0.05) non-significant on the 7^th (30 DAP) day of disease assessment. Comparing the sprayed and unsprayed plots, the treated plot had considerably decreased disease incidence. For the last eight assessment dates, the unsprayed plot continuously had the highest disease incidence values. In all sites throughout seasons, fungicide-treated plots had significantly lower ascochyta blight severity indices than untreated plots at all stages of crop growth (P 0.05) (Table 2).

For both the fungicide and the varieties at the two sites during the seasons, with the exception of a few rare cases, the severity in the >3 times planned spray was much lower than the control. With means across year and location, the fungicide produced the largest reduction in severity vs control for each variety (Table 2). The mean temperature at each of the site-seasons under study ranged from 9.2 to 32.6 OC, and more than 580 mm of rain fall throughout that time (Figure 1). When temperatures are low (15–25 OC) and there is a lot of rain (>150 mm) throughout the growth season, Ascochyta blight is more severe and may completely kill susceptible varieties of plants (Nene, 1982). The current findings are also reported and confirmed by Pande et al. (2005).

3.2 Area under disease progress curve (AUDPC)

The study found that chickpea varieties, fungicide application interval (FAI), and interaction effects all significantly affected AUDPC at P 0.05. However, locations and cropping seasons were not significantly affected by the study (Figure 2). According to (Bellido Lopez, 2008), AUDPC is a very useful summary of plant disease epidemics that takes into account starting intensity, the rate parameter, and the duration of the epidemic, which affects ultimate disease intensity. The AUDPC levels in untreated plots of susceptible genotype were utilized throughout the trial as a measure of how favorable the environment was to the disease. The more favorable the weather was for the pathogen, the higher the AUDPC levels. The environment's ability to support the pathogen was significantly (P 0.05) correlated with the effectiveness of chemical control in susceptible varieties. When weather supported minor epidemics and increased the mancozeb WP 80% spray schedule, ascochyta blight suppression was effectively suppressed, but insufficiently when weather supported severe epidemics and lowered the spray schedule (Figure 2).

Based on the average AUDPC value for the two years and locations, the Dhera variety had the lowest AUDPC values at Dugda and Dhera, respectively, and the Habru variety had the highest AUDPC values at 136% and 141.76 % for the 2020 and 2021 cropping seasons, respectively (Figure 2). Mariye variety had the highest AUDPC values at 561.72% and 491.76% for the two years, respectively (Figure 2). This demonstrated that the Dhera and Habru types are more resistant to the occurrence of the Ascochyta blight than the Mariye variety. These findings have been supported and agreed upon by several writers throughout the course of time (Aslam et al., 2014). Additionally, Mancozeb WP 80% management had a highly significant (P 0.05) impact on AUDPC reduction when compared to untreated plot at the 7th, 14th, and 21st days (Figure 2).

The disease progressed more quickly in untreated plots compared to the plots received fungicide treatments over seasons and locations (Figure 2). The comparison of treatments/varieties by their values of AUDPC indicated that the value of AUDPC is directly proportional to the AB disease incidence, severity and epidemic levels.

3.3 Disease progress rate

Between the main effects of variety and FAI as well as their interaction, the disease progression rate showed a significant difference at P 0.05 (Figure 3). Ascochyta blight disease infection spread more quickly on susceptible varieties in both location and seasons than on resistant varieties in Dhera and Habru, where slower disease progression rates were seen throughout the crop seasons of 2020 and 2021 (Figure 3). Zewdie reported similar findings in 2018, stating that genotypes have a significant impact on the disease progression rate, which is higher for susceptible and lower for resistant varieties. Additionally, the untreated plot had a greater disease progression rate, but the 7th FAI recorded a reduced infection rate during the duration of the 2020 and 2021 growing seasons, and the 7th FADI once more recorded an infection digression rate (-0.01) (Figure 3).

Separate analysis of the Logistic and Gompertz models were conducted. R2, coefficient residue, standard error, and other metrics were used to calculate the model's fitness. The varieties Dhera (7, 14 and 21 days of fungicide treatment), Habru (14 days of fungicide application), and Mariye (7 and 21 days of fungicide application) were fitted with the Gompertz model, while the others were fitted with the Logistic Model, based on the comparison of the R2 values (Table 4). The Gomportez model, an alternative for the logistic model, is based on the disease's gradual progression over time and is directly related to both its level (y) and its negative natural logarithm (-Lny). Additionally, in the logistic model, the proportion of healthy plant tissue (1-y) to the degree of disease present (y) determines how gradually the disease progresses over time. This combination of exponential and monomolecular characteristics gives basis for description of polycyclic disease by logistic model (Fininsa C. 2022).

However, we use both "r" and AUDPC values for comparison. In general, Gompertz model fits using data for each fungicide application day's analysis of all treatments. The rate shows how far the illness has progressed each day, but the AUDPC values produce an extensive amount of data from the time the disease first appeared until the last recording date at plant maturity. Based on these results, the best variety was determined to be Dhera (7, 14 and 21 days of fungicide application), followed by Habru (7, 14 and 21 days of fungicide application), while Mariye was determined to be a susceptible variety. Because the AUDPC computed values are the same for both models, the only aspect of the logistic model from which it differs is the value of Rate(r). However, the AUDPC and rate values are often connected with each other using the Gompertz model's logistic function.

3.4 Chickpea growth

In both the 2020 and 2021 cropping seasons, an analysis of variance showed that treatments significantly affected the number of pods per plant, the number of seeds per plant, the number of seeds per pod, the days to 50% flowering, and the 95% physiological maturity. For each variety, the interval fungicide application on the 7^th day produced the longest days to 50% flowering and 95% physiological maturity (Table 5). This shows that the ascochyta blight affects and shortens the period of flowering and physiological maturity, which causes a decrease in yield by interfering with each variety's optimum physiological and flowering maturity. The findings also showed that the ascochyta blight intensity level accelerated chickpea senescence, which had a detrimental influence on the amount of grain produced. Ascochyta blight was seen to rapidly re-infect the plants, although rejuvenates were also seen on the susceptible variety at the 21st-day time period of fungicide treatment.

When comparing the Mariye variety to Habru and Dhera, the frequency of fungicide treatments had a highly significant impact on the number of pods per plant and the number of seeds per pod in both the seasons and the locations (Table 6). In comparison to untreated plants, the number of pods per plant and the number of seeds per pod increased after fungicide treatments (Table 6). These results are in agreement with Bellido Lopez's (2008) findings, which indicated that agronomic parameters such as pods per plant, seeds per pod, hundred seed weight, days to flowering, and days to maturity play a significant effect in the severity of ascochyta blight in chickpea. This proves that the ascochyta blight affects every aerial portion of the chickpea plant and has a significant impact on plant development. Despite greater disease on individual plants (Chang et al., 2007), the improved seed production with large plant population is due to the development of more pods and seeds per unit area (Regan et al., 2003). Similar to this, Shamsi et al. (2010)'s findings demonstrated that varietal variations are more closely related to plants' pods and are utilized as standards for choosing the best materials. The frequency of scheduled fungicide treatments also significantly affected the plant height of all kinds in the current investigation, according to analysis of variance (Table 5). The plants in treatments that received fungicide application at 7- and 14-day intervals were slightly taller than the plants in treatments that received treatment at 21-day intervals or received no treatment (Table 5).

Analysis of variance results for seed yield showed that the Mariye variety was significantly affected by the treatments relative to the season and location. As a result, the results showed that yield in both years and locations was significantly affected by the frequency of Mancozeb 80% WP treatments. In 2020 and 2021, the mean grain yield of treatments with fungicide applications at 7th and 14th day intervals was significantly higher than that of treatments with 21st and untreated. On the Dhera variety, treatments with 7^th day interval fungicide applications had mean yields of 3484.60 kg ha-1 over years and locations, and 3497.00 kg ha-1 over locations, respectively. These values were significantly higher than at treatments with no fungicide application (Table 7). According to a previous investigation by Sagir et al. (2004), the yield per plant has a significant correlation with the quantity of pods per plant. Although in this instance, fewer pods per plant probably led to a lower yield per plant. According to Sadeghipour and Aghaei (2012), the production of grain yields may be affected by varietal differences. The findings showed that the grain yield was significantly affected by severe ascochyta blight on susceptible variety with untreated plots, and 100% yield loss was reported (Table 8). Ascochyta blight can result in the completely death of plants, which would result in a 100% yield loss, according to other writers who also agreed with this statement (Islam et al., 2017). According to Chongo et al. (2003), chickpea fungicide treatments have a significant influence on the production of grain. Furthermore, Amin and Fufa (2014) proved that the Mancozeb 80% WP fungicide treatment for ascochyta blight in Ethiopia results in the maximum yield of chickpea.

Depending on the quantity and distribution of the initial inoculum and the disease's increase of growth over time, integrating host resistance and applying fungicides are the main strategies for managing polycyclic diseases (Fininsa C. 2022). The current study was done on integrated management strategies in locations that have been identified nationally as disease hotspots and are characterized by climate variables that favor the spread of ascochyta blight epidemics. Contrary to the earlier report by Amin Mohammed and Fufa Melkamu (2014), which stated that the disease was first discovered 54 days after planting in Ethiopia, chickpea ascochyta blight was first detected in the current study at 30 days post-planting across seasons and locations. However, the Ascochyta blight start time has been shown to vary from year to year and to be influenced by environmental factors as well (Shtienberg et al., 2005). In this study, the disease's incidence and severity were found to be greater at both locations. This finding may be related to the fact that both study locations were at low altitudes with high temperatures and/or humidity, which supports the pathogen's quick development and dissemination in the study regions (Fig. 1). This result is consistent with that of Pande et al. (2005), who also highlighted that ascochyta blight outbreaks are more likely to emerge in most regions of the world where the crop is often produced in cold, wet conditions. In addition, Trapero-Casas and Kaiser (1992) pointed out that the disease's severity increased with increasing relative humidity, cloudiness, and extended wet weather, which promotes the quick onset and spread of AB disease.

Ascochyta blight continues to remain an important challenge to Ethiopia's potential to produce chickpeas, despite the recent development and widespread usage of partly resistant cultivars. Partial resistance alone did not adequately reduce ascochyta blight in study regions with moderate to high inoculum pressure and weather conducive to disease development, as seen in 2016, 2017, 2018, and 2019. The study also revealed a significant negative relationship between yield loss and ascochyta blight intensity (Tables 3 and 8). This indicates that severe ascochyta blight caused large production losses, although the connection between the disease and yield losses varied among varieties via Dhera, Habru, and Mariye. The most effective strategy to reduce losses in yield brought on by chickpea ascochyta blight is to employ resistant genetic resources. The absence of sources of high levels of resistance in the main gene pool and the high pathogenic diversity of the fungus pose obstacles to breeding for resistance to ascochyta blight in chickpea, according to Khan et al. (1999) and other research that verified and confirmed these findings. In order to boost the levels and/or persistence of the resistance, it is therefore necessary to diversify the genetic material responsible for ascochyta blight resistance in the highest chickpea germplasm. This is especially important in light of changes in the virulence of the Didymella rabiei pathotype.

Didymella rabiei aggressive isolates severely affect some chickpea cultivars that are resistant to less aggressive isolates under the same conditions because of the high level of variation in aggressiveness within the Didymella rabiei population (Chongo et al., 2004) and similar level of variation in resistance among chickpea cultivars. Therefore, differences in ascochyta blight-associated yield loss severity between resistant, moderately resistant, and susceptible varieties, as well as between the moderate and resistant varieties, were found when overall ascochyta blight severity was low. This showed that variety selection is an essential aspect of an integrated ascochyta blight management strategy for chickpea. According to Fininsa C. (2022), resistant varieties of plants may minimize or delay the growth of the pathogen population that causes epidemics of plant diseases. Chemical protectants may also delay the pathogen population's rate of expansion. The study found a favorable link between disease incidence and severity at both low and high ascochyta blight scoring from each variety. Contrarily, at low levels of disease, incidence and severity frequently have a linear connection; hence, measuring incidence is adequate (Madden et al., 2007). However, there is frequently a complex inconsistent link between incidence and severity at high disease levels.

The disease developed similarly in all kinds during the experiment, although at varying intensities; Mariye variety had the highest intensity, compared to Dhera and Habru. Ascochyta blight pre-infection processes such spore germination, appressorium production, and germ tube penetration are all comparable in both resistant and susceptible variants, according to several research that have supported this hypothesis. However, throughout the development of the disease, resistant and susceptible varieties differ from one another (Ilarslan and Dolar, 2002). Additionally, as the plants progress toward the stage of flowering and podding phases, resistance decreases (Chongo and Gossen, 2003). The two resistant and moderately resistant chickpea varieties in this study also demonstrated resistance at the seedling and early vegetative phases but were susceptible at the flowering and podding stages.

Though this differed across the two sites, varieties with better ascochyta blight resistance often also had higher grain yields. This was in agreement with Kimurto et al. (2013) who indicated that the high disease incidence, which damaged vegetative plant parts and killed some plants, was the reason of the poor yield in the arid highlands of the Rift Valley. With regard to grain yield measurements such final plant stand, number of pods, biomass, and hundred seed weight, disease severity and AUDPC showed a negative association. Kimurto et al. (2013) made comparable observations. Additionally, there was an adverse correlation between grain yield performance and the severity of the disease. Therefore, it is of the utmost importance to control Ascochyta blight disease, particularly through the application of host plant resistance, in order to increase chickpea grain yield performance.

Any management technique or crop production method that lowers the incidence and severity of diseases during the development of the epidemic from the beginning minimizes the rate of disease increase (Fininsa C. 2022). With the method of treatment chosen or put into effect throughout the study, the progressive and digressive curve of the disease and the epidemic rate of the disease (the rate of growth of the epidemic) have been established (Fig. 3). Depending on the type of disease, according to Fininsa C. (2022), dy/dt (the absolute rate of change in y at t) might signify the absolute rate of disease decrease. This suggests that the primary biotic challenge to the main cropping season chickpea agriculture in the Ethiopian area is the ascochyta blight. However, fungicide management significantly reduces the AUDPC of chickpea ascochyta blight in comparison to untreated control. Applications of protective fungicides often reduce the chance of infection of deposited spores, depending on when the fungicide is used (Fininsa C. 2022). This is true for both epidemiological and ecological grounds of plant disease management. Therefore, the creation of integrated disease management (IDM) tools to combat this threat may make it possible for chickpea to be sown during the main season in areas where it is currently impossible and reduce pathogen-related losses in regions where main cropping season is currently used. According to Fininsa C. (2022), diseases offer serious challenges to agricultural yields and product quality, hence the development of efficient disease management techniques is crucial to plant productivity and profitability. IDM is also crucial to sustainability. With the integration of Mancozeb 80% WP during the trial, adequate disease suppression was accomplished even in environments that were extremely permissive to the pathogen when the degree of resistance was high, as in the case of the Dhera variety. Akem (1999) further proved that genotype resistance is the main technique used to control Didymella rabiei.

The Mancozeb fungicide, which is extensively used and consistently effective against ascochyta blight on a variety of pulse crops, was also confirmed and published by Chongo et al. in 2003 and Gan et al., 2006. Similar to this, Bretag et al. (2006) found that ascochyta blight-prone chickpea varieties may be cultivated successfully by strategically spraying foliar mancozeb fungicide multiple times throughout the growing season. Additionally, according to Kaiser and Hannan (1988), fungicide-sprayed treatments can significantly aid in reducing the initial inoculum level and limit the spread of the disease or races into new regions.

The high disease incidence that might have attacked vegetative plant parts and died nearly all plants, minimizing production in especially for those untreated plots and except during the extended fungicide application period, is the reason of the poor yield in both the experimental season and location. In comparison to unsprayed plots, fungicide-sprayed plots produced higher yields. While the seed yield recorded from treated plots was higher than that from untreated plots (906.2 kg ha-1), the seed yield on sprayed plots varied from 3526 to 122 kg ha-1 with a mean value of 2506.9 kg ha-1. Ascochyta blight resistance and minimal disease incidence were observed in the Habru and Dhera varieties in contrast to the Mariye variety, which had a lower yield (0.00–1968 kg/ha). Therefore, it is advised to grow both of these varieties at various Mancozeb 80% WP treatment periods that are less conducive to ascochyta blight epidemics. According to earlier research (Ahmed et al., 2006), cultivars with compound leaves are less susceptible to disease than unifoliate lines.

High temperatures (9.4–32.6 OC) and high relative humidity (97.3%) were reported during the growth seasons, which enhanced disease severity at both research regions, during the major rainy season, when the study was done. It took 4–5 days to detect the disease's pycnidia, and it may have taken 7–10 days for them to manifest due to favorable environmental conditions. Ascochyta blight infection and its development occur between 5 and 25 OC, with an ideal temperature of 16 to 20 OC, as noticed and validated by Pande et al. (2005). Additionally, Trapero-Casas and Kaiser (1992) pointed out that increased relative humidity, cloudiness, and prolonged wet weather all contribute to a disease's tendency to grow and spread quickly. Due to favorable meteorological circumstances that encouraged rapid pathogen development and transmission due to cold, damp conditions in these locations, the ascochyta blight infection was significant at both Dhera and Dugda (Fig. 1). In order to create a strong integrated disease management strategy, it is essential to comprehend the crucial environmental factors, such as temperature, relative humidity, and rainfall, that encourage infection, disease development, dissemination, survival of primary inoculum, and disease development (Fininsa C. 2022). With the incorporation of fungicide sprays, the two varieties in the current study that had stronger resistance to ascochyta blight also had higher grain production (Table 7).

Similar to this, Pande et al. (2005) verified that in most locations of the world where the chickpea crop is often produced, cold and rainy weather encourages the development of disease outbreaks. According to Tekeoglu et al. (2000), ascochyta blight hinders chickpea production all over the world. Disease treatment based on a single gene resistance is unlikely to provide long-term control due to the genetic diversity of the disease's pathogen population (Chongo et al. 2004). This study showed that ascochyta blight can cause substantial yield losses in susceptible varieties, including complete crop failure (Table 8), in the conditions where Ethiopian chickpeas are grown. While the influence of chickpea genotype and fungicide treatment time accounted for most of the variance in both years, this study also looked at the effect of chickpea variety, fungicide application time, location, and season on the presence and intensity of ascochyta blight. However, the effects of cropping season and location on disease levels were minimal.

These tests investigated the importance of applying fungicides at key points during the chickpea growth season in addition to assessing fungicide effectiveness. The majority of the new varieties in Ethiopia are far more disease resistant than the ones that were previously available, and only sometimes need to be treated with fungicides. The best outcomes will be seen in cases where fungicide is used with the more potent mancozeb 80% WP before the disease is discovered or at extremely low infection levels. In order to enhance protection against disease transmission by rain splash, protectant fungicides—regardless of variety—are most effective when managed before rain (Shtienberg et al. 2006). Only in the most extreme situations were fungicide treatments necessary during the research period for the more resistant varieties. Therefore, Fininsa C. (2022) suggested that integrated disease management is the most effective and cost-effective when all pertinent information about the crop is available, including information about the various pathogens known to cause economically significant diseases on the crop, the history of the diseases in previous seasons and years, varietal resistance to the diseases, the environmental conditions anticipated to prevail during the current season, and practicable diseases management technologies. There is always a chance that new pathotypes could exceed the resistance of the various chickpea varieties, according to Pande et al. (2005). The results revealed that combining a fungicide's first two treatments (7th and 14th ) with the Dhera and Habru varieties had the most influence on disease. This could be as a result of the Mancozeb WP 80% fungicide spray being able to control the spread of ascochyta blight secondary inoculum inside and between adjacent plants while also having the potential to minimize ongoing primary infection. Nevertheless, given the genotype's susceptibility, continued spraying is essential for the rest of the growing season to keep severe outbreaks under control and reduce production losses. This was observed at two hot spots for ascochyta blight throughout growing seasons, where ascochyta blight infection during pod filling resulted in considerable output losses. To prevent pods from ascochyta blight infection, Chongo and Gossen (2001) established that fungicide use during podding is advised for all varieties. Additionally, this guarantees the production of disease-free seed that is kept in the nation for planting. The trial locations in Dhera and Dugda had the greatest areas under progression of disease curves, respectively (Fig. 2). Variety Mariye was found to be more prone to ascochyta blight disease in the two experimental sites where it was studied. Varieties with larger area under the disease progress curve also had higher disease severity. It is obvious that an important integrated management component of controlling ascochyta blight in chickpea for its economic viability is applying fungicide sprays early in the season and integrating with resistance chickpea varieties to delay the rapid development of the epidemic during this period. According to Fininsa C. (2022), the objective of integrated disease management will therefore assure its economic viability, boost productivity and productivity, ensure human and environmental health, and preserve production and biodiversity.

This study demonstrated that the integration of fungicide treatment time schedules and varieties, as compared with cropping seasons and locations, had an impact on chickpea ascochyta blight. The results of the current investigation showed that the disease may cause damage a plant at any stage of growth by creating lesions on any part of it. As a result, if the disease is left untreated, yield loss could be catastrophic and reach over 90%. Reducing the losses brought on by the disease depends on resistant varieties and the application of Mancozeb 80% WP, but repeated applications at set intervals up to four times are typically effective and cost-effective.

By complementing with genetic resistance, Mancozeb 80% WP consumption in ascochyta blight of chickpea can be decreased while minimizing production costs and environmental consequences of fungicides. For the ascochyta blight of chickpea to be economically and effectively controlled, integrated disease management strategies must be adopted. We obtain the conclusion from this study that the main cropping season of chickpea is achievable in Ethiopia when the ascochyta blight is sufficiently suppressed. Variety resistance is therefore the main strategy for disease management, with Mancozeb 80% WP control being used as a supplementary strategy if needed. Therefore, it was demonstrated that timing the application of the fungicide Mancozeb 80% WP after the crop started to senesce was ineffective. A fungicide application to protect the crop against the disease, however, would probably not be profitable if the outbreak is more severe and develops during podding.

Four fungicide treatments are often necessary to manage ascochyta blight during the growing season in an area with significant rainfall. The integration of high yielding varieties with 2.5 kg a.i / ha Mancozeb 80% WP is lastly advised for additional investigation and potential introduction in Ethiopia's chickpea belt area. When the disease severity level is high during the main growing season, the most susceptible variety could not be suited for production. In breeding initiatives aiming at creating resistant varieties of chickpea, varieties that are only partially resistant to ascochyta blight can be employed. For continued breeding to maintain its genetic potential and grain output with 14 to 21 application interval periods, the resistant and high yielding variety Dhera is especially advised.

Acknowledgement

This study was supported by a PhD grant from the Modernizing Ethiopian Research on Crop Improvement (MERCI) initiative and the Ethiopian Institute of Agricultural Research (EIAR). We appreciate the financial assistance from the MERC and EIAR.

Conflict of interest

An article titled "Temporal Epidemics and Management of Ascochyta Blight (Ascochyta rabiei) on Chickpea (Cicer arietinum L.) in Central Rift Valley, Ethiopia" has been enclosed and submitted to the European Plant Pathology journal for consideration for publication. We neither engage in nor have any financial affiliation with any of the organizations or entities mentioned in this book. Additionally, we have no competing interests to disclose.

I'm sending and I would like to have the manuscript considered for publication in the European Plant pathology journal. This is a declaration that the manuscript titled " Temporal Epidemics and Management of Ascochyta Blight (Ascochyta rabiei) on Chickpea (Cicer arietinum L.) in Central Rift Valley, Ethiopia" is my original work and not published earlier and I have not submitted this manuscript for publication elsewhere. I have cited a number of authors whose published materials are used in the manuscript.

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Table 1. Fungicide application interval (FAI) and chickpea variety interactions exhibited a two-way effect on the prevalence of chickpea ascochyta blight at Dhera and Dugda in Ethiopia during the crop seasons of 2020 and 2021.

Variety	FAI (days)	Incidence (%)				Mean incidence over seasons (%)
		2020		2021
		Dhera	Dugda	Dhera	Dugda	Dhera	Dugda
Mariye	7	53.4^g-j	51.9^hij	48.0^i-l	45.3^i-m	50.7^de	48.6^def
	14	55.6^fi	76.2^cde	55.5^fi	50.3^ijk	55.6cd	63.2^bc
	21	65.5^e-h	72.1^cde	66.4^efg	68.5^def	65.9^b	70.3^b
	Unsprayed	91.2^ab	99.6^a	81.2^bcd	82.5^bc	86.2^a	91.1^a
Habru	7	17.7^s-w	24.3^p-w	12.5^w	16.2^t-w	15.1^lm	20.2^klm
	14	26.5^o-v	29.4^n-t	21.2^r-w	22.3^q-w	23.8^jkl	25.9^ijk
	21	40.0^j-o	41.2^j-n	30.4^n-s	30.5^n-s	35.2^ghi	35.8^gh
	Unsprayed	37.3^k-p	49.9^ijk	32.2^m-r	35.2^l-q	34.8^e	42.6^efg
Dhera	7	14.7^uvw	12.8^vw	12.8^vw	13.9^vw	13.7^lm	13.4m
	14	30.5^n-s	20.3^r-w	18.7^r-w	15.2^uvw	24.6^jkl	17.7^klm
	21	40.4^j-n	27.8^n-u	24.2^p-w	21.6^q-w	32.3^ghi	24.7^jkl
	Unsprayed	48.6^i-l	48.4^i-l	37.7^k-p	30.9^n-s	43.1^efg	39.6^fgh
LSD(0.05)	13.74					9.72
CV (%)	20.88

According to Fisher's protected LSD test, means in the column with different lettered are significantly different at P 0.05.

Table 2. Chickpea varieties and fungicide application interval (FAI) had a two-way interaction effect on the severity index of chickpea ascochyta blight at Dhera and Dugda, Ethiopia, during the 2020 and 2021 growing seasons.

Variety	FAI (days)	Severity index (%)				Mean of severity index (%)
		2020		2021		Mean of severity index (%)
		Dhera	Dugda	Dhera	Dugda	Dhera	Dugda
Mariye	7	20.3^j-m	20.2^j-n	18.4^k-o	16.7^l-q	19.3^f	18.5^fg
	14	29.2^efg	31.4^de	21.5^i-l	23.6^h-k	25.3^de	27.5^cde
	21	64.5^bc	60.9^c	30.8^ef	36.6^d	47.6^b	48.8^b
	Unsprayed	67.8^b	70.7^a	66.3^ab	64.3^cd	67.1^a	67.5^a
Habru	7	11.4^r	11.3^r	11.7^pqr	11.1^r	11.5^ij	11.2^j
	14	15.5^m-r	17.0^l-p	15.0^n-r	12.5^pqr	15.2^ghi	14.8^g-i
	21	17.6^l-p	16.8^l-q	15.4^m-r	17.7^l-p	16.5^fgh	17.3^fgh
	Unsprayed	29.5^efg	30.3^ef	28.9^e-h	26.8^e-i	29.2^c	28.6^cd
Dhera	7	11.4^r	11.3^r	11.6^qr	11.1^r	11.5^ij	11.2^j
	14	15.3^m-r	16.0^m-r	15.8^m-r	12.5^pqr	15.6^gh	14.2^hij
	21	14.7^o-r	13.7^o-r	15.0^n-r	14.4^o-r	14.8^g-j	14.0^hij
	Unsprayed	25.6^f-i	24.2^g-j	26.3^e-i	24.2g^-j	26.0^cde	24.2^e
LSD(0.05)	5.29					3.74
CV (%)	13.1

Means in the column followed by different letter are significantly different at P <0.05 according to Fisher’s protected LSD test.

Table 3. The average effect of the combination of chickpea varieties and fungicide application intervals (FAI) evaluation on the ascochyta blight severity index at various time intervals in Dhera and Dugda during the 2020 and 2021 crop years.

Varieties	FAI (days)	Locations	Severity index (%) at days after planting (DAP)
Varieties	FAI (days)	Locations	30	37	44	51	58	65	72	79	86
Mariye	Unsprayed	Dhera	22.7^a	25.9^a	40.7^ab	61.1^a	81.5^a	95.8^a	95.4^a	100^a	100^a
	Unsprayed	Dugda	19.9^ab	24.0^a	37.5^b	53.7^b	75.5^a	83.3^a	89.4^a	94.0^a	84.7^ab
	7	Dhera	19.5^ab	13.0^f-i	13.9^de	14.4^fg	19.0^c-f	18.1^d-g	19.0^efg	24.1^e-i	28.2^f-i
	7	Dugda	14.4^c	12.5^f-i	12.0^e	14.8^fg	16.2^def	18.5^d-g	22.7^d-g	28.2^d-h	24.5^ghi
	14	Dhera	19.0^b	25.9^a	16.2^cde	21.3^def	25.0^cde	30.1^cd	24.5^c-g	36.1^c-f	35.6^efg
	14	Dugda	14.4^c	17.1^bcd	20.4^cd	25.5^d	31.5^c	32.9^c	32.4^cde	34.7^c-g	29.6^e-h
	21	Dhera	13.9^c	20.4^b	44.4^a	38.0^c	47.2^b	65.3^b	52.8^b	71.3^b	74.1^bc
	21	Dugda	13.0^c	18.5^ab	35.2^b	38.9^c	53.2^b	65.3^b	62.0^b	66.7^b	60.2^cd
Habru	Unsprayed	Dhera	13.0^c	14.8^d-h	15.7^cde	17.1^efg	21.8^c-f	29.6^cd	33.8^cd	37.0^cde	47.7^de
	Unsprayed	Dugda	13.4^c	12.0^ghi	12.5^e	16.2^efg	20.4^c-f	25.9^cde	31.0^c-f	40.3^cde	44.5^def
	7	Dhera	12.9^c	11.1ⁱ	11.1^e	11.1^g	13.0^ef	11.1^g	11.1^g	11.1ⁱ	11.1^hi
	7	Dugda	12.5^c	11.1ⁱ	11.1^e	11.1^g	11.1^f	11.1^g	11.6^g	11.1ⁱ	9.72ⁱ
	14	Dhera	13.9^c	15.7^c-f	13.9^de	12.0^g	11.1^f	15.7^efg	13.0^g	19.4^f-i	15.7^hi
	14	Dugda	13.0^c	12.0^ghi	12.5^e	11.1^g	12.5^ef	13.0^efg	16.2^g	16.7^hi	17.1^ghi
	21	Dhera	12.0	11.1ⁱ	20.3^cd	13.9^g	14.8^def	25.9^cde	13.0^g	13.9^hi	14.8^hi
	21	Dugda	13.4^c	11.1ⁱ	11.1^e	11.6^g	12.5^ef	15.3^efg	15.7^g	15.7^hi	16.8^ghi
Dhera	Unsprayed	Dhera	14.4^c	13.4^e-i	15.3^cde	22.7^de	27.8^cd	32.9^c	38.4^c	47.7^c	57.0^cd
	Unsprayed	Dugda	12.5^c	13.4^e-i	15.3^cde	17.6^efg	21.3^c-f	25.5^c-f	33.3^cd	41.2^cd	44.9^def
	7	Dhera	12.5^c	11.1ⁱ	11.1^e	11.1^g	11.1^f	11.1^g	11.1^g	11.1ⁱ	11.1^hi
	7	Dugda	12.5^c	11.1ⁱ	11.1^e	11.1^g	11.1^f	11.1^g	11.1^g	11.1ⁱ	9.72ⁱ
	14	Dhera	14.8^c	16.7^cde	13.4^e	13.4^g	12.5^ef	14.8^efg	18.1^fg	18.5^ghi	19.9^ghi
	14	Dugda	13.0^c	11.6^hi	12.0^e	11.6^g	12.5^ef	13.9^efg	16.8^g	18.0^ghi	19.9^ghi
	21	Dhera	12.5^c	15.3^c-g	21.3^c	11.6^g	12.0^ef	14.8^efg	13.9^g	14.4^hi	19.5^ghi
	21	Dugda	13.4^c	12.0^ghi	12.0^e	11.1^g	12.0^ef	12.5^fg	15.7^g	16.2^hi	17.6^ghi
LSD (0.05)			3.55	3.29	6.85	7.26	13.5	13.4	14.0	17.0	19.1
CV (%)			10.1	8.94	15.3	14.8	22.6	19.0	19.5	20.9	23.0
Grand mean			14.5	15.1	18.3	20.1	24.4	28.9	29.2	33.3	33.9
SE			1.45	1.35	2.80	2.97	5.53	5.48	5.71	6.94	7.79

The means in the column with distinct lettering are significantly different at P 0.05, according to Fisher's protected LSD test.

Table 4. Summary table for FAI and chickpea types of Ascochyta blight model fitness

Variety	FAI	Gompotez model (r)	Logistic Model (r)	Gompertz Model(R²)	Logistic Model (R²)	Model Fitness
Dhera	Untreated	0.487443	0.487443	98.80%	99.80%	Logistic Model
	7	-0.02349	-0.02349	95.40%	97.40%	Gompertz Model
	14	0.02536	0.02536	95.25%	88.00%	Gompertz Model
	21	0.011728	0.011728	89.21%	92.21%	Gompertz Model
Habru	Untreated	0.523738	0.523738	100%	98.6%	Gompertz Model
	7	-0.02141	-0.02141	99.50%	99.50%	Logistic Model
	14	0.054956	0.054956	97.23%	98.23%	Gompertz Model
	21	0.059959	0.059959	96.00%	99.00%	Logistic Model
Mariye	Untreated	1.433875	1.433875	99.30%	99.80%	Logistic Model
	7	0.163692	0.163692	98.14%	96.14%	Gompertz Model
	14	0.336442	0.336442	99.20%	100.00%	Logistic Model
	21	0.889417	0.889417	99.90%	99.12%	Gompertz Model

Table 5. Evaluation of fungicide application intervals (FAI) and chickpea variety effects on ascochyta blight throughout the 2020 and 2021 growing seasons in Dhera and Dugda, Ethiopia.

Variety

FAI (days)

Phenology and growth parameters

Days to 50% flowering

Days to 95% physiological maturity

Plant height (cm)

2020

2021

2020

2021

2020

2021

Dhera

Dugda

Dhera

Dugda

Dhera

Dugda

Dhera

Dugda

Dhera

Dugda

Dhera

Dugda

Mariye

Habru

Dhera

7

52.7^ab

49.3^ab

53.0^ab

54.3^ab

83.3^c-g

78.7^d-h

109^a-e

111^a-e

40.0^pqr

38.1^r

45.7^i-m

45.0^k-p

14

53.0^ab

50.3^ab

53.0^ab

58.7^a

86.0^c-g

82.3^c-h

111^a-d

112^a-d

42.0^m-r

40.3^o-r

45.4^j-n

45.7^i-m

21

36.3^bc

57.3^a

52.3^ab

66.0^f-i

64.7^g-i

116^a-d

14.0^u

30.3^s

46.3^h-m

43.9^l-q

Unsprayed

22.3^c

22.0^c

0.00^d

21.0^c

37.3^ij

36.0^ij

0.00^j

42^hi

14.1^u

23.1^t

17.8^u

15.3^u

7

50.7^ab

49.7^ab

51.0^ab

56.7^a

84.3^c-g

82.0^ch

102^a-g

70.1^e-i

48.0^f-l

49.5^e-k

52.3^b-g

52.1^c-g

14

50.3^ab

53.0^ab

50.3^ab

55.7^a

85.3^c-g

83.0^ch

101^a-g

70.1^e-i

47.9^f-l

47.5^g-l

54.3^a-e

52.8^a-f

21

53.7^ab

51.0^ab

51.7^ab

57.3^a

88.7^b-g

81.7^ch

104^a-g

109^a-e

43.9^l-q

48.4^f-l

51.4^c-h

50.5^d-i

Unsprayed

60.0^a

61.7^a

60.3^a

62.0^a

106^a-f

104.7^a-g

139^a

81^c-h

37.3^r

39.4^qr

45.3^j-o

39.2^qr

7

50.7^ab

51.0^ab

59.0^a

84.3^c-g

83.3^c-g

108^a-e

111^a-d

51.9^c-g

49.2^f-k

57.7^a

55.6^abc

14

52.0^ab

50.0^ab

51.7^ab

54.7^a

85.0^c-g

84.0^c-g

112^a-d

51.1^c-h

50.3^d-i

57.2^ab

55.2^a-d

21

51.7^ab

56.7^a

49.3^ab

53.3^ab

87.0^b-g

86.0^c-g

107^a-e

110^a-e

48.6^f-l

50.9^c-h

55.9^abc

55.1^a-d

Unsprayed

60.7^a

59.0^a

58.0^a

63.0^a

104^a-g

96.7^b-g

121^a-bc

128^a-b

40.3^n-r

45.4^i-m

47.3^g-l

38.9^qr

Grand Mean

50.7

90.9

44.1

LSD (0.05)

18.2

Ns

41.0

5.10

CV

22.1

Note: means in the column followed by the same letter are not significantly different at p = 0.05 according to Fisher’s protected LSD test

Table 6. Effect of chickpea variety and Mancozeb WP 80% spray intervals on the varieties yield components during 2020 and 2021cropping seasons at Dhera and Dugda, Ethiopia.

Variety	FAI (days)	Number of seeds per pod				Number of pods per plant
		2020		2021		2020		2021
		Dhera	Dugda	Dhera	Dugda	Dhera	Dugda	Dhera	Dugda
Mariye	7	1.40^f-n	1.44^d-n	1.36^h-n	1.31^k-n	20.5^l-o	29.2^e-j	21.4^k-o	19.7^mno
	14	1.40^f-n	1.32^j-n	1.28^lmn	1.33^j-n	15.8^o-p	17.7^o-p	17.9^op	15.9^op
	21	0.32^o	0.11^pq	1.26^mn	1.25ⁿ	13.8^p-q	1.22^r	1.75^r	9.89^q
	Unsprayed	0.21^op	0.00^q	0.00^q	0.14^opq	0.58^r	0.00^r	0.00^r	1.61^r
Habru	7	1.57^a-f	1.64^abc	1.62^a-d	1.50^a-k	34.7^b-e	39.0^ab	30.8^dh	32.1^c-g
	14	1.66^ab	1.68^a	1.63^a-d	1.47^b-l	31.1^c-h	35.8^a-d	29.2^eh	27.0^g-k
	21	1.55^a-h	1.56^a-i	1.51^a-j	1.44^a-n	28.2^f-j	29.1^e-j	29.0^f-j	23.8^j-n
	Unsprayed	1.56^a-h	1.57^a-f	1.37g-n	1.42^e-n	25.0^i-m	23.9^j-n	19.6^mno	18.7^nop
Dhera	7	1.63^a-d	1.56^a-g	1.60^a-d	1.69^a	34.8^b-e	40.9^a	31.7^c-g	31.3^c-h
	14	1.58^a-f	1.64^abc	1.61^a-e	1.61^a-e	33.2^c-f	36.8^abc	31.3^ch	28.9^f-j
	21	1.59^a-f	1.63^a-d	1.44^d-n	1.50^a-k	30.3^d-i	32.0^c-g	25.7^h-l	26.9^g-k
	Unsprayed	1.45^c-m	1.55^a-h	1.32^j-n	1.35^i-n	19.2^nop	23.7^j-n	18.2^nop	17.1^o-p
Grand Mean		1.33				23.0
LSD (0.05)		0.19
CV		8.90				15.3

Table 7. Effect of fungicide application interval (FAI) and chickpea variety on yield and crop hundred seed weight during the 2020 and 2021 growing seasons in Dhera and Dugda, Ethiopia.

Variety	FAI (days)	Yield per hectare (Kg^-1)					Hundred seed weight (g)
		2020		2021		2020			2021
		Dhera	Dugda	Dhera	Dugda	Dhera		Dugda	Dhera	Dugda
Mariye	7	1950^c	1968^c	1545^cd	767^fgh	22.8^a-h		17.2^g-j	23.9^a-h	23.5^a-h
	14	1531^cde	1613^cd	744^fgh	770^fgh	23.2^a-h		17.7^f-i	22.9^a-h	21.5^b-i
	21	617^f-i	816^e-h	136^hi	122^hi	12.0^h-k		6.75^jk	19.8^e-i	20.9^d-i
	Unsprayed	442^ghi	0.00ⁱ	0.00ⁱ	0.00ⁱ	6.00^jk		0.00^k	0.00^k	0.00^k
Habru	7	3418^ab	3287^ab	3425^ab	3314^ab	32.9^abc		23.1^a-h	33.5^a	32.7^a-d
	14	3162^ab	3066^ab	3431^ab	3144^ab	31.1^a-e		23.0^a-h	33.5^ab	30.9^a-e
	21	2779^b	2991^ab	3228^ab	3042^ab	33.4^ab		33.7^a	33.6^a	30.3^a-e
	Unsprayed	1649^cd	1632^cd	720^f-i	1098^d-g	23.1^a-h		23.1^a-h	24.6^a-g	24.1^a-g
Dhera	7	3471^ab	3526^a	3498^ab	3467^ab	33.1^ab		23.0^a-h	31.2^a-e	31.2^a-e
	14	3203^ab	3298^ab	3412^ab	2948^ab	31.5^a-e		22.3^a-h	32.3^a-d	32.4^a-d
	21	3177^ab	3076^ab	3287^ab	3019^ab	30.0^a-e		21.0^c-i	28.7^a-g	29.2^a-f
	Unsprayed	1949^c	1953^c	1282^c-f	149^hi	25.8^a-g		28.0^a-g	27.8^a-g	27.0^a-g
Grand Mean		2107				23.77 12.0
LSD (0.05)		726				23.77 12.0
CV		21.3				31.0

Note: means in columns followed by the same letter are not significantly different at p = 0.05 according to Fisher’s protected LSD test.

Table 8. Effect of chickpea varieties and fungicide application interval (FAI) on relative yield loss at Dhera and Dugda, Ethiopia, during the 2020 and 2021 growing seasons.

Varieties	Relative yield loss (Kg)
	2020		2021
	Dhera	Dugda	Dhera	Dugda
Mariye	100^a	100^a	100^a	100^a
Habru	45.2^bc	56.0^b	52.7^bc	55.3^bc
Dhera	45.2^bc	56.0^b	52.7^bc	55.3^bc
LSD (0.05)	14.0
CV	31.0

Note: means in columns followed by the same letter are not significantly different at p = 0.05 according to Fisher’s protected LSD test

Temporal Epidemics and Management of Ascochyta Blight (Ascochyta rabiei) on Chickpea (Cicer arietinum L.) in Central Rift Valley, Ethiopia

Status:

Journal Publication

Version 1

Abstract

Figures

1. Introduction

2. Materials and Methods

3. Results

4. Discussion

5. Conclusions

Declarations

References

Tables

Status:

Journal Publication

Version 1