3.1 Effect of variety and IBA concentration on crop transplant survival and growth parameters
3.1.1 Percentage of transplants' survival
Both the main effects of variety and IBA concentrations significantly (P < 0.01) influenced the percentage of survival of rooted shoot tip cuttings. The analysis of variance also revealed that the interaction between the two had a significant (P < 0.05) effect on the percentage of survival of transplanted rooted shoot tip cutting. The interaction between variety and IBA concentration in the rooted shoot tip cuttings revealed that varieties Jaline untreated with IBA concentration, Gussa and Dagim treated with 3000 ppm IBA concentration, and Ater Abeba treated with 6000 ppm IBA concentration achieved a high percentage of transplants that survived (100%), but except Belete, Gudane, Shankola and Dagim not treated, Gudane, Shankola treated with 3000 ppm and Jalene treated with 6000 ppm IBA all other treatments had non-significant differences. On the other hand, a low percentage of transplants that survived was recorded in the IBA untreated Gudine variety (70.79%) (Table 2). Among the cultivars, Ater Abeba had a high percentage of transplants that survived (98.67%). This differences could be due to variation among varieties with respect to environmental sensitivity, and that IBA promotes vigorous root production in the nursery. This vigorous root growth provides nutrients and moisture for shoot development. Because of the continuous supply of water and nutrients through the xylem, the development of a vigorous root system via rooted shoot tip cutting resulted in an increased percentage of transplant survival rooted cuttings in the field. In general, the percentage of transplants that survived increased from 0 ppm IBA to 6000 ppm IBA treatments, then declined at the concentration of 9000 ppm.
This result is in line with Çelık & Çetın (2021) report which stated that IBA treatment increased the percentage of transplant survival and variations among cultivars in transplant survival. Similarly, Yousry et al. (2018) found that increasing IBA concentrations up to 6000 ppm enhanced the root quantity and root length of potato stem cuttings, promoting the survival of rooted cuttings in the field. The present study is in agreement with the finding of Çelık & Çetın (2021), who reported that the interaction effect of cultivar and IBA affected the percentage of transplants that survived. Mumtaz et al. (2022) have also found that the application of different concentrations of IBA had varying responses among the varieties for survival of transplants in the field.
Table 2
The interaction effect of variety and IBA concentration on the percentage of transplants' survival
Variety
|
IBA concentration (ppm)
|
0
|
3000
|
6000
|
9000
|
Belete
|
75.57fg
|
92.38abc
|
94.15abc
|
93.32abc
|
Gudenie
|
70.79g
|
86.04cdef
|
94.50abc
|
91.31abcd
|
Jalenie
|
100a
|
98.95a
|
98.92a
|
88.26bcde
|
Shonkolla
|
81.22defg
|
86.11cde
|
90.77abcd
|
94.78abc
|
Gusa
|
89.68abcd
|
100.00a
|
95.83abc
|
93.68abc
|
Gera
|
91.81abc
|
94.64abc
|
95.45abc
|
93.47abc
|
Dagim
|
79.01efg
|
100.00a
|
97.76ab
|
93.93abc
|
Ater Ababa
|
98.85a
|
97.91ab
|
100.00a
|
97.91ab
|
CV (%)
|
6.9
|
LSD (5%)
|
10.47
|
|
|
|
Level of significance
|
*
|
|
|
|
*Significant at P < 0.05; Means with followed by the same letter(s) in rows and columns are not significantly different at 5% level of significance.
3.1.2. Tuber initiation
The main effect of variety and the interaction effect of variety and IBA concentrations were highly significant influences (P < 0.01) on tuber initiation of rooted shoot tip cuttings. However, the main effect of IBA concentration did not have a significant influence on tuber initiation of rooted shoot tip cuttings. The interaction between potato variety and IBA concentrations in rooted shoot tip cutting revealed earlier tuber initiation (43 days) in Gera at all IBA concentrations levels and in Shenkola at IBA concentrations of 0 ppm and 6000 ppm; however, there was a non-significant difference with Guassa at 6000 ppm, Shenkola at 3000 ppm and 9000 ppm, and Ater Abeba at 0 ppm, 6000 ppm, and 9000 ppm. On the contrary, late tuber initiation (50.33 days) was observed in varieties Gudine, Jaline, and Dagim with no treatment of IBA (Table 3). The variations in tuber initiation among varieties and IBA treatments could be attributed to the genetic differences in earlier and faster sucrose production along with a better response to IBA treatment (Oli & Devi, 2022). Short day length, phytochrome, high light, high sucrose, low temperature, and low nitrogen levels are the six key factors that promote tuber formation, according to Zierer et al. (2021). Similar to this, Gul (2022) observed that the application of IBA improved the root quantity and root length of potato stem cuttings; thus, roots absorb water and minerals as a result of the well-established plant; additionally, good photosynthesis results in more sucrose, which encourages the early tuber initiation of rooted cuttings. The present study is in agreement with the finding of Azad et al. (2023), who reported that the interaction effect of variety and IBA affected tuber initiation. Sani et al. (2022) also found that the variety and IBA significantly influenced the tuber initiation of potato plants in stem cutting.
Table 3
The interaction effect of variety and IBA concentration on tuber initiation
Variety
|
IBA concentration (ppm)
|
0
|
3000
|
6000
|
9000
|
Belete
|
46.00bc
|
45.33bcd
|
46.00bc
|
46.00bc
|
Gudenie
|
50.33a
|
45.00bcde
|
46.66b
|
45.33abc
|
Jalenie
|
50.33a
|
49.66a
|
50.00a
|
50.00a
|
Shonkolla
|
43.00f
|
43.33ef
|
43.00f
|
43.66def
|
Gusa
|
45.00bcde
|
50.00a
|
44.66cdef
|
45.00bcde
|
Gera
|
43.00f
|
43.00f
|
43.00f
|
43.00f
|
Dagim
|
50.33a
|
50.00a
|
50.00a
|
50.00a
|
Ater Ababa
|
43.33ef
|
45.00bcde
|
44.66cdef
|
44.00def
|
CV (%)
|
2.57
|
LSD (5%)
|
1.94
|
Level of significance
|
**
|
** Highly significant at P < 0.01; Means with followed by the same letter(s) in rows and columns are not significantly different at 5% level of significance.
3.1.3. Days to physiological maturity
The main effect of variety and IBA concentration significantly influenced (p < 0.01) days to physiological maturity. However, the interaction of variety and IBA concentration did not significantly influence the days to physiological maturity. Variety Jaline had the shortest days to physiological maturity (82.91 days) after transplanting, followed by variety Gussa (87.58 days), and the longest days to physiological maturity was for variety Gudine (96.16 days) (Table 4). Early physiological maturity of the crop may be due to genetic differences in plant tissue that have a low nitrogen content, a high sucrose content, and a high endogenous auxin (Kim & Lee, 2019).
On the other hand, increased application of IBA from 0 (control) to 9000 ppm treatment significantly reduced days to physiological maturity from 91.7 to 89.08 (Table 4). This might be due to the role of IBA in hastening the physiological maturity of potatoes associated with well-established quality roots. The current findings were supported by previous studies in which IBA was linked to potato maturity shortening(Gul, 2022; Zierer et al., 2021).
Table 4
Effects of variety and IBA concentration on days to physiological maturity
Variety
|
Days to physiological maturity
|
Belete
|
92.58b
|
Gudenie
|
96.16a
|
Jalenie
|
82.91e
|
Shonkolla
|
91.25bc
|
Gusa
|
87.58d
|
Gera
|
89.33cd
|
Dagim
|
91.41bc
|
Ater ababa
|
89.75cd
|
Siginificance
|
**
|
LSD (5%)
|
2.22
|
IBA conc. ppm
|
|
0
|
91.70a
|
3000
|
90.45ab
|
6000
|
89.25b
|
9000
|
89.08b
|
Significance
|
**
|
LSD (5%)
|
1.57
|
CV
|
3.03
|
** Highly significant; Means followed by same letters within a column in a given treatments are not significantly different at P < 0.05 |
3.1.4. Plant height
Variety had a significant (P < 0.01) influence on plant height, but neither IBA concentration nor the interaction between cultivars and IBA concentration significantly affected plant height. The highest plant height (81.35 cm) was recorded in the rooted shoot tip cutting of variety Shenkolla, followed by the plant height of variety Gera (78.43 cm). In contrast, the lowest plant height (62.92 cm) was recorded in rooted shoot tip cuttings of the variety Ater Abeba. Shenkola and Gera, which didn’t significantly differ among themselves (Table 5). The significant differences in plant height observed among the varieties may be attributed to genetic differences. This result agrees with those of Solomon et al. (2019) and Lemma et al. (2019), who reported that plant height varied with potato varietal differences. This suggestion is also consistent with that of Colasuonno et al. (2019), who reported that plant height is a quantitative trait influenced by environmental factors.
Table 5
Effects of variety and IBA concentration on plant height
Varieties
|
Plant height
|
Belete
|
67.68b
|
Gudenie
|
68.77b
|
Jalenie
|
63.62c
|
Shonkolla
|
81.35a
|
Gusa
|
68.93b
|
Gera
|
78.43a
|
Dagim
|
62.97c
|
Ater ababa
|
62.92c
|
Siginificance
|
**
|
LSD (5%)
|
3.83
|
IBA conc. PPM
|
|
0
|
69.05
|
3000
|
68.32
|
6000
|
70.54
|
9000
|
69.42
|
Significance
|
Ns
|
LSD (5%)
|
2.71
|
CV
|
6.77
|
** Highly significant; Means followed by same letters within a column in a given treatments are not significantly different at P < 0.05 |
3.1.5. Leaf area index
Variety had a significant (P < 0.01) influence on the leaf area index, but neither IBA concentration nor the interaction between variety and IBA concentration significantly affected the leaf area index. In this study, the highest leaf area index (3.60) was recorded in the rooted shoot tip cutting of variety Gera, followed by the leaf area index of variety Belete (3.35). In contrast, the lowest leaf area index (2.10) was recorded in rooted shoot tip cuttings of the variety Dagim (Table 6). Gera is not significantly different from Belete but significantly different from the other varieties. Significant differences in leaf area index observed in this study among varieties may be attributed to genetic differences that have a higher survival rate in the field, varieties that have more leaves and longer leaves per plant, and varieties more resistant to late blight diseases. This result agrees with those of Zeleke et al. ( 2021), who reported that leaf area index varied with potato varietal differences. This suggestion is also consistent with that of Franceschini et al. (2019), who mentioned that the leaf area index is a quantitative trait influenced by environmental factors, which is why an increase in the severity of potatoes due to late blight decreases the leaf area index.
Table 6
Effects of Variety and IBA concentration on leaf area index
Varieties
|
Leaf area index
|
Belete
|
3.35ab
|
Gudenie
|
2.86c
|
Jalenie
|
3.29abc
|
Shonkolla
|
3.05bc
|
Gusa
|
3.15bc
|
Gera
|
3.60a
|
Dagim
|
2.10d
|
Ater ababa
|
3.13bc
|
Siginificance
|
**
|
LSD (5%)
|
0.45
|
IBA conc. PPM
|
|
0
|
2.91
|
3000
|
3.19
|
6000
|
3.20
|
9000
|
2.97
|
Significance
|
Ns
|
LSD (5%)
|
0.32
|
CV
|
18.05
|
** Highly significant; Means followed by same letters within a column in a given treatments are not significantly different at P < 0.05 |
3.2. Effect of variety and IBA concentration on Potato Yield and Yield Components parameters
3.2.1. Number of tubers per plant
The number of tubers per plant obtained by the rooted shoot tip cutting of potato was significantly affected by variety and the interaction between potato variety and IBA concentration (P < 0.01). However, the main effects of IBA concentrations were not significantly affected. The interaction between potato variety and IBA concentration in rooted shoot tip cutting revealed that more tubers per plant (8.6) were produced from variety Belete treated at 6000 ppm IBA concentration; however, there were non-significant differences from Belete and Gudnie untreated, Jaline and Gera at 3000 ppm, and Ater Abeba at 0 ppm, 6000 ppm, and 9000 ppm IBA concentration whereas fewer tubers per plant (1.7) were produced from Dagim treated at a concentration of 3000 ppm IBA (Table 7). This variation could be due to the difference in genetic potential among potato varieties, and the increase in tuber numbers may be attributed to an increase in s the number of stolons per stem, which is related to the amount of assimilates available for belowground tubers. There is also a close relationship between tuber number and leaf area index, which is associated with IBA which was responsible for better plant establishment (Naghdi et al., 2022).
Stolen and tuberization processes are affected by genetic makeup and environmental factors (Naghdi et al., 2022). According to Das et al (2021), sufficient growth (leaf area index) had a positive contribution to the tuber number. Similarly, the number of stolons per stem increases with increasing leaf area index due to the relationship caused by the amount of assimilates available for below ground growth (Oliveira et al., 2021).
Table 7
The interaction effect of variety and IBA concentration on number of tubers per plant
Variety
|
IBA concentration (ppm)
|
0
|
3000
|
6000
|
9000
|
Belete
|
7.4ab
|
5.7efg
|
8.6a
|
6.5bcde
|
Gudenie
|
7.3abc
|
4.9fghi
|
4.3ghij
|
5.6efgh
|
Jalenie
|
6.5bcde
|
8.5a
|
6.7bcde
|
6.6bcde
|
Shonkolla
|
3.5ijkl
|
5.4efgh
|
4.2hijk
|
4.8fghi
|
Gusa
|
4.1hijkl
|
5.3efgh
|
5.6efgh
|
4.1hijkl
|
Gera
|
6.8bcde
|
7.3abc
|
5.8def
|
6.6bcde
|
Dagim
|
2.8klm
|
1.7m
|
2.7lm
|
2.9jklm
|
Ater Ababa
|
7.4ab
|
5.9cdef
|
8.0ab
|
7.5ab
|
CV (%)
|
16.06
|
LSD (5%)
|
1.49
|
|
|
|
Level of significance
|
**
|
|
|
|
** Highly significant at P < 0.01; Means with followed by the same letter(s) in rows and columns are not significantly different at 5% level of significance.
3.2.2. Proportion of tubers in each size category
i. Very small (< 25 g) and small 25–39 g tubers
The main effects of variety and IBA concentration as well as the interactive effect significantly (P < 0.01) influenced the production of very small tubers (< 25 g). The interaction between potato variety and IBA concentrations in rooted shoot tip cutting revealed that the largest very small tubers of potato (47.01%) produced Ater Abeba treated at 6000 ppm IBA concentration, which was a non-significant difference from Ater Abeba and Dagim treated at a concentration of 3000 ppm, while fewer very small tubers of potato (6.61%) produced by Gera treated at a concentration of 6000 ppm IBA (Table 8). Among the varieties, Ater Abeba, and from the IBA concentration, 9000 ppm were recorded more very small tubers from the main effect.
Table 8
The interaction effect of variety and IBA concentration on very small tubers (< 25 g) number (%)
Variety
|
IBA concentration (ppm)
|
|
0
|
3000
|
6000
|
9000
|
|
Belete
|
15.66efghij
|
17.97def
|
14.91efghijk
|
13.50fghijk
|
Gudenie
|
17.23defgh
|
12.80ghijk
|
10.97jklmn
|
16.13efghi
|
Jalenie
|
11.55ijklm
|
12.97ghijk
|
11.54jklmn
|
12.56hijkl
|
Shonkolla
|
10.21klmn
|
12.35ijkl
|
17.40defg
|
24.50c
|
Gusa
|
7.84lmn
|
19.87abcdefg
|
13.57fghijk
|
12.90ghijk
|
Gera
|
10.51klmn
|
17.05fghi
|
6.61n
|
14.62efghijk
|
Dagim
|
25.39c
|
23.42abc
|
13.80fghijk
|
21.68cd
|
Ater Ababa
|
36.21b
|
22.46abcd
|
47.01a
|
39.31b
|
CV (%)
|
17.07
|
|
LSD (5%)
|
4.79
|
|
Level of significance
|
**
|
|
** Highly significant at P < 0.01; Means with followed by the same letter(s) in rows and columns are not significantly different at 5% level of significance.
Similarly, the main effects of variety and IBA concentration as well as the interactive effect significantly (P < 0.01) influenced the production of small-size tubers (25–39 g). Dagim treated at 9000 ppm IBA concentration produced the most small-size tubers (24.22%); however, there was a non-significant difference from Belete at 0 ppm, 3000 ppm, and 6000 ppm; Dagim at 0 ppm and 3000 ppm; and Ater Abeba at 3000 ppm and 6000 ppm, whereas Gera treated at a concentration of 9000 ppm IBA produced fewer small-size tubers (6.32%) (Table 9).
Variations in small and very small size tubers of potato among varieties and varied responses of varieties to IBA treatments could be due to the inherent characteristics of the variety used, and the increase in small and very small tubers of potatoes may be attributed to the competition of tubers for assimilation. Varieties affected by late blight during the growth stage may produce small tubers, and IBA application above and below the optimum application rate may contribute to the small number of tubers due to poor root establishment, which delayed maturity, and the increase in the number of tubers per plant may be attributed to competition among tubers (Hajjar et al., 2022)
In agreement with this study, Stark et al. (2020) and Workayehu et al. (2021) reported that tuber size distribution varied with varieties. According to Asnake et al. (2023) and (Mijena et al., 2022) ,both inherent characteristics and environmental factors have an impact on tuber size. Also, according to Mijena et al. (2022), the increased number of tubers was responsible for the maximum production of small-sized tubers. On the other hand, Weselek et al. (2021) found that fewer small tubers result from delayed plant emergence and reduced plant growth because there are fewer assimilates available for tubers with delayed maturity.
Table 9
The interaction effect of cultivars and IBA concentration on small-sized tubers (25–39 g) percentage
Variety
|
IBA concentration (ppm)
|
|
0
|
3000
|
6000
|
9000
|
|
Belete
|
20.34abcdef
|
20.74abcdef
|
20.45abcdef
|
12.20jkl
|
Gudenie
|
19.47bcdefg
|
18.75defg
|
18.74defg
|
18.49defg
|
Jalenie
|
12.67hijkl
|
10.94 l
|
12.60ijkl
|
13.58hijkl
|
Shonkolla
|
16.47fghijk
|
15.33ghijkl
|
13.88hijkl
|
18.93cdefg
|
Gusa
|
13.16hijkl
|
19.87abcdefg
|
16.92fghi
|
12.02 kl
|
Gera
|
16.31fghijk
|
17.05fghi
|
16.66fghij
|
6.32m
|
Dagim
|
23.59ab
|
23.42abc
|
12.72hijkl
|
24.22a
|
Ater Ababa
|
17.22efgh
|
22.46abcd
|
21.77abcde
|
13.93hijkl
|
CV (%)
|
16.51
|
|
LSD (5%)
|
4.55
|
|
Level of significance
|
**
|
|
** Highly significant at P < 0.01; Means with followed by the same letter(s) in rows and columns are not significantly different at 5% level of significance.
ii. Medium-sized tubers (39–75 g)
The main effect of variety and the interaction effect of variety and IBA concentrations significantly influenced (P < 0.01) the number of medium-sized tubers. The analysis of variance revealed that more medium-sized tubers (39.42%) were produced by Jalenie treated at 3000 ppm IBA concentration, followed by medium-sized tubers produced by Jaline untreated IBA (33.58%), while fewer medium-sized tubers (12.90%) were produced by Ater Abeba treated at a concentration of 6000 ppm IBA (Table 10). Variations in medium-sized tubers of potato among varieties and varied responses of varieties to IBA treatments indicate that this variation could be due to the inherent characteristics of the varieties used, and the competition of tubers for the assimilates of sucrose at optimum IBA treatment levels.
Tuber sizes are affected by genetic makeup and environmental factors (Asnake et al., 2023; Dagne et al, 2019; Ullah et al., 2019). The present finding is supported by the result of Workayehu et al.(2021), which indicated that medium-sized tubers ranged from 26.8 to 81.08%. On the other hand, the good rooting of cuttings due to IBA has contributed to the development of medium-sized tubers due to the rapid plant emergence and better plant growth that results in a higher number of medium-sized tubers(Hajjar et al., 2022).
Table 10
The interaction of variety and IBA concentration on medium-sized tubers (40–75 g) percentage.
Variety
|
IBA concentration (ppm)
|
|
0
|
3000
|
6000
|
9000
|
|
Belete
|
28.07cdef
|
16.93lm
|
29.84bcd
|
22.52hijk
|
Gudenie
|
24.01fghijk
|
31.16bc
|
29.30bcde
|
27.54cdefgh
|
Jalenie
|
33.58b
|
39.42a
|
29.32bcde
|
25.09defghijk
|
Shonkolla
|
30.91bc
|
22.73ghijk
|
24.83defghijk
|
20.15kl
|
Gusa
|
25.11defghijk
|
25.22defghi
|
21.36jkl
|
26.46cdefghi
|
Gera
|
27.10cdefgh
|
25.11defghijk
|
22.78ghijk
|
22.53hijk
|
|
Dagim
|
24.32efghijk
|
23.58fghijk
|
29.32bcde
|
27.74cdefg
|
|
Ater Ababa
|
20.97jkl
|
24.15fghijk
|
12.90m
|
21.68ijkl
|
|
CV (%)
|
12.15
|
|
LSD (5%)
|
5.05
|
|
Level of significance
|
**
|
|
** Highly significant at P < 0.01; Means with followed by the same letter(s) in rows and columns are not significantly different at 5% level of significance.
iii. Large-sized tubers (> 75 g)
The interaction between potato cultivars and IBA concentrations in rooted shoot tip cuttings revealed that more large tubers (56.51%) were produced by Gera treated at 9000 ppm IBA concentration. However, this was a non-significant difference from Belete at 9000 ppm, Shonkola at 3000 ppm, Gussa untreated, and Gera treated at 6000 ppm IBA concentration. On the other hand, fewer large-sized tubers (18.31%) were produced by Ater Abeba treated at a concentration of 6000 ppm IBA (Table 11). Variations in large-sized tubers of potato among varieties and varied responses of varieties to IBA treatments for large-sized tubers of potato could be due to inherent characteristics of the varieties, fewer tubers per plant as a result of decreased competition among tubers for sucrose assimilation, and the absence of late blight disease(Mijena et al., 2022).
According to Workayehu et al. (2021), the proportion of large tubers ranged from 0.6 to 55.67%, and the maximum mean percentage was noted from progenies of Gera and Shenkola. Similarly, Bekele & Ebrahim ( 2020) and Stark et al. (2020) reported that the maximum size of large tubers is due to a lower number of tubers per plant, which is varietal character and effect of environmental factors.
Table 11
The interaction effect of variety and IBA concentration on Large-sized tubers (> 75 g) percentage
Variety
|
IBA concentration (ppm)
|
|
0
|
3000
|
6000
|
9000
|
|
Belete
|
35.91kl
|
44.33defghi
|
34.79lm
|
51.77abc
|
Gudenie
|
39.26hijkl
|
37.27jkl
|
40.98fghijkl
|
37.82ijkl
|
Jalenie
|
42.19efghijk
|
36.65kl
|
46.97bcdefg
|
48.75bcde
|
Shonkolla
|
42.39efghijk
|
49.56abcd
|
43.87defghij
|
36.39kl
|
Gusa
|
53.86ab
|
47.34bcdef
|
48.12bcde
|
48.61bcde
|
Gera
|
46.05cdefgh
|
40.26ghijkl
|
53.93ab
|
56.51a
|
Dagim
|
26.67n
|
33.98lm
|
44.16defghij
|
26.35n
|
Ater Ababa
|
25.58n
|
28.18mn
|
18.31o
|
25.06no
|
CV (%)
|
10.65
|
|
LSD (5%)
|
7.02
|
|
Level of significance
|
**
|
|
** Highly significant at P < 0.01; Means with followed by the same letter(s) in rows and columns are not significantly different at 5% level of significance.
3.2.3. Average tuber weight
Average tuber weight of potato tubers was highly significantly (P < 0.01) influenced by the main effect of variety and the interaction effect of variety and IBA concentration but not by the main effect of IBA concentration. The highest average tuber weight (136.08 g) was produced by Shenkolla not treated with IBA. However, there was a non-significant difference from Shenkola treated at 3000 ppm and 6000 ppm and Gera treated at 6000 ppm IBA concentration, while the lowest weight (40.18 g) was produced by Ater Abeba treated at a concentration of 9000 ppm IBA (Table 12). Variations in average tuber weight of potato could be due to inherent characteristics of the cultivars as well as the effect of IBA on plant establishment that created differences in competition among tubers for sucrose.
In agreement with the result of the present study, Kassaw et al. (2021) reported that there were significant differences between varieties for average tuber weight of potato, especially in their late blight resistance. Mekashaw et al. (2020) also suggested that the variety with a higher average tuber weight and a lower number of tubers per plant could be due to differences in dry matter partitioning efficiency to tubers and further untreated IBA led to the production of a higher average tuber weight due to less computation among the plant because of less survival (Getaneh & Laekemariam, 2021).
Table 12
The interaction effect of variety and IBA concentration on tuber weight (g/tuber)
Variety
|
IBA concentration (ppm)
|
0
|
3000
|
6000
|
9000
|
Belete
|
63.02jklmnop
|
92.52cdefghi
|
67.98ijklmno
|
106.11bcde
|
Gudenie
|
57.84klmnop
|
82.62efghijk
|
84.19defghij
|
78.51fghijkl
|
Jalenie
|
72.06hijklmn
|
64.08jklmnop
|
78.58fghijkl
|
71.90hijklmn
|
Shonkolla
|
136.08a
|
115.92abc
|
112.18abc
|
109.07bcd
|
Gusa
|
103.80bcdef
|
93.75cdefgh
|
98.72cdefg
|
107.98bcd
|
Gera
|
98.28cdefg
|
91.40cdefghi
|
125.00ab
|
110.35bc
|
Dagim
|
76.12ghijklm
|
101.81bcdef
|
49.44nop
|
50.88mnop
|
Ater Ababa
|
42.59p
|
54.61lmnop
|
43.57op
|
40.18p
|
CV (%)
|
18.53
|
LSD (5%)
|
25.34
|
Level of significance
|
**
|
** Highly significant at P < 0.01; Means with followed by the same letter(s) in rows and columns are not significantly different at 5% level of significance.
3.2.4. Tuber weight per plant
Variety had a significant (P < 0.01) influence on tuber weight per plant, but neither IBA concentration nor the interaction between variety and IBA concentration significantly affected tuber weight per plant. The highest tuber weight per plant (691.52 g) was recorded in the rooted shoot tip cutting of variety Gera, followed by the tuber weight per plant (565 g) noted in variety Belete, whereas the lowest tuber weight per plant (163.50 g) was recorded in variety Dagim (Table 13). Significant differences in tuber weight per plant observed in this study among varieties may be attributed to genetic differences in photosynthesis that resulted in more food material accumulation and ultimately higher tuber weight per plant.
In agreement with the result of the present study, Solomon et al. (2019) reported that there were significant differences between varieties for tuber weight per plant of potato. Kassaw et al. (2021) also suggested that varieties with higher tuber weight per plant in addition to their resistance to late blight might also be more efficient in dry matter partitioning to tubers than varieties with lower average tuber weight due to more photosynthesis.
Table 13
Effects of variety and IBA concentration on tuber weight per plant
Varieties
|
Tuber weight per plant
|
Belete
|
565.00b
|
Gudenie
|
405.28d
|
Jalenie
|
506.12bc
|
Shonkolla
|
520.60bc
|
Gusa
|
481.29c
|
Gera
|
691.52a
|
Dagim
|
163.50f
|
Ater ababa
|
324.62e
|
Siginificance
|
**
|
LSD (5%)
|
64.64
|
IBA conc. PPM
|
|
0
|
428.01
|
3000
|
465.96
|
6000
|
466.77
|
9000
|
468.25
|
Significance
|
Ns
|
LSD (5%)
|
45.70
|
CV
|
17.32
|
** Highly significant; Means followed by same letters within a column in a given treatments are not significantly different at P < 0.05 |
3.2.5. Yield in tuber size category
i. Yield of very small-sized tuber (< 25 g)
The yield of a very small tuber of potato was highly significantly (P < 0.01) influenced by the main effect of variety and the interaction effect of variety and IBA concentration, but not by the main effect of IBA concentration. The interaction between potato cultivars and IBA concentrations in rooted shoot tip cuttings revealed that the highest yield of very small tubers (1.55 ton ha-1) was produced by Ater Abeba at a concentration of 6000 ppm IBA, followed by the highest yield of very small-sized tubers (1.16 ton ha-1) produced by Ater Abeba treated at 9000 ppm IBA concentration and the lowest (0.11 ton ha-1) produced by Shenkola with untreated IBA (Table 14). Variations in the highest yield of very small tubers could be due to the inherent characteristics of the cultivars used, and the increase in the yield of the very small tubers of potatoes may be attributed to competition among plants due to increased IBA up to 6000 ppm, increases in transplant survival, and an increase in the very small tuber size proportion per plant.
According to Bekele & Ebrahim (2020) and Stark et al. (2020) the effects of variety and establishment significantly increased the very small size of the potato tuber. An increased survival rate due to the responsibility of IBA for rooting has evidently contributed to the development of very small tubers due to the scarcity of photo assimilates for tuber enlargement and bulking (Hajjar et al., 2022).
Table 14
The interaction effect of variety and IBA concentration on Yield of very small-sized tuber (t ha-1)
Variety
|
IBA concentration (ppm)
|
0
|
3000
|
6000
|
9000
|
Belete
|
0.30fghijk
|
0.37efghi
|
0.48defg
|
0.33efghijk
|
Gudenie
|
0.36efghij
|
0.24ghijk
|
0.16hijk
|
0.40efgh
|
Jalenie
|
0.40efgh
|
0.55cde
|
0.37efghi
|
0.36efghij
|
Shonkolla
|
0.11k
|
0.18hijk
|
0.21hijk
|
0.35efghijk
|
Gusa
|
0.15ijk
|
0.21hijk
|
0.38efghi
|
0.28fghijk
|
Gera
|
0.36efghij
|
0.73c
|
0.23hijk
|
0.51cdef
|
Dagim
|
0.18hijk
|
0.12jk
|
0.15ijk
|
0.22hijk
|
Ater Ababa
|
1.09b
|
0.65cd
|
1.55a
|
1.16b
|
CV (%)
|
36.16
|
LSD (5%)
|
0.24
|
Level of significance
|
**
|
** Highly significant at P < 0.01; Means with followed by the same letter(s) in rows and columns are not significantly different at 5% level of significance.
ii. Yield of small-sized tuber ( 25–39 g)
The main effects of cultivars and IBA concentration as well as the interactive effect significantly (P < 0.01) influenced the yield of small-sized tubers (25–39 g) (ton ha-1). The interaction between potato cultivars and IBA concentrations in rooted shoot tip cuttings revealed that the highest yield of small-sized tubers (2.18 t ha-1) was produced by Ater Abeba at a concentration of 6000 ppm IBA, followed by the highest yield of small-sized tubers (2.01 t ha-1) produced by Belete treated at 6000 ppm IBA concentration; however, there was a non-significant difference between them. Whereas the lowest (0.34 ton ha-1) was produced by Dadim at a concentration of 6000 ppm IBA treated (Table 15). Variations in the highest yield of the small-sized tuber of potato among varieties and varied responses of varieties to IBA treatments in the highest yield of the small-sized tuber of potato could be due to the inherent characteristics of the cultivars used, and the increase in yield of the small-sized tuber of potato may be attributed to competition among plants due to increased IBA up to 6000 ppm increases in transplant survival, a greater number of tubers per plant, and a smaller tuber size proportion per plant.
In agreement with this study, Stark et al. (2020) and Workayehu et al. (2021) reported that small-sized tuber yields varied with varieties. An increased plant population rate due to the responsibility of the IBA for rooting has evidently contributed to the development of very small tubers due to the competition among plants (Hajjar et al., 2022).
Table 15
The interaction effect of variety and IBA concentration on yield of small-sized tuber (ton ha-1)
Variety
|
IBA concentration (ppm)
|
0
|
3000
|
6000
|
9000
|
Belete
|
1.18defgh
|
1.30cdefg
|
2.01ab
|
0.89fghijk
|
Gudenie
|
0.93efghij
|
0.87ghijk
|
0.83ghijkl
|
1.15defghi
|
Jalenie
|
1.16defghi
|
1.30cdefg
|
1.21cdefgh
|
1.01efghij
|
Shonkolla
|
0.60jkl
|
0.76hijkl
|
0.67ijkl
|
0.98efghijk
|
Gusa
|
0.68ijkl
|
1.37cdef
|
1.13defghi
|
0.59jkl
|
Gera
|
1.18defgh
|
1.43cde
|
1.23cdefgh
|
0.51kl
|
Dagim
|
0.55jkl
|
0.57jkl
|
0.34l
|
0.81hijkl
|
Ater Ababa
|
1.66bc
|
1.56bcd
|
2.18a
|
1.22cdefgh
|
CV (%)
|
27.82
|
LSD (5%)
|
0.48
|
Level of significance
|
**
|
** Highly significant at P < 0.01; Means with followed by the same letter(s) in rows and columns are not significantly different at 5% level of significance.
iii. Yield of medium-sized tuber ( 40–75 g)
The main effects of variety and the interactive effects of variety and IBA concentration significantly (P < 0.01) influenced the yield of medium-sized tubers (ton ha-1). The analysis of variance also revealed that the main effects of IBA concentration had a significant (P < 0.05) effect on the yield of medium-sized tubers (ton ha-1). The interaction between potato cultivars and IBA concentrations in rooted shoot tip cuttings revealed that the highest yield of medium-sized tubers (7.89 tons ha-1) was produced by Jaline at a concentration of 3000 ppm IBA, followed by the highest yield of medium-sized tubers (5.38 tons ha-1) produced by Belete treated at a 6000 ppm IBA concentration, and the lowest (1.06 tons ha-1) produced by Dagim at a concentration of 3000 ppm IBA treated (Table 16) Variations in the highest yield of the medium-sized tuber of potato among varieties and varied responses of varieties to IBA treatments in the highest yield of the medium-sized tuber of potato could be due to the inherent characteristics of the cultivars used, and the increase in yield of the medium-sized tuber of potato may be attributed to increases in transplant survival, a greater number of tubers per plant, and a larger medium-sized tuber size proportion per plant.
This finding is consistent with the findings of Dagne et al. (2019) and Ullah et al. (2019), who found a higher number of tubers per plant and a higher proportion of medium-sized tubers per plant, as well as varietal character. Increase the number of plants due to increased transplant survival, which increases the total number of tubers per area(Hajjar et al., 2022) .
Table 16
The interaction effect of variety and IBA concentration on yield of medium-sized tuber (ton ha-1)
Variety
|
IBA concentration (ppm)
|
0
|
3000
|
6000
|
9000
|
Belete
|
3.01defghi
|
2.20hijk
|
5.38b
|
3.33defgh
|
Gudenie
|
2.12ijkl
|
3.30defgh
|
2.66fghij
|
3.81de
|
Jalenie
|
5.80b
|
7.89a
|
5.01bc
|
3.42defg
|
Shonkolla
|
2.46ghik
|
2.90defghi
|
3.07defghi
|
2.57fghik
|
Gusa
|
2.73efghij
|
3.83de
|
3.22defghi
|
2.95defghi
|
Gera
|
3.63def
|
3.99cd
|
3.61def
|
3.81de
|
Dagim
|
1.12kl
|
1.06l
|
1.32kl
|
1.65jkl
|
Ater Ababa
|
3.32defgh
|
3.40defg
|
3.02defghi
|
3.20defghi
|
CV (%)
|
21.26
|
LSD (5%)
|
1.14
|
Level of significance
|
**
|
** Highly significant at P < 0.01; Means with followed by the same letter(s) in rows and columns are not significantly different at 5% level of significance.
iv. Yield of large-sized tuber (> 75 g)
Both the main effects of variety and IBA concentration significantly (P < 0.01) influenced the yield of large tubers (ton ha-1). The analysis of variance also revealed that the interaction between the two had a significant (P < 0.05) effect on the yield of large tubers. The interaction between potato variety and IBA concentrations in rooted shoot tip cuttings revealed that the highest yield of large-sized tubers (24.17 tons ha-1) was produced by Gera at a concentration of 9000 ppm IBA; however, this was non-significantly different from Gera-treated at 6000 ppm IBA concentration and Belete treated at 9000 ppm IBA concentration, whereas the lowest yield (3.47 tons ha-1) was produced by Dagim at a concentration of 9000 ppm IBA treated (Table 17). Variations in the highest yield of the large-sized tuber of potato among varieties and varied responses of varieties to IBA treatments in the highest yield of the large-sized tuber of potato could be due to the inherent characteristics of the cultivars used, and the increase in yield of the large-sized tuber of potatoes may be attributed to more tubers per plant with a larger tuber size proportion.
Workayehu et al. (2021) reported that a larger tuber size proportion was found in the progeny of Gera and Shenkola due to an inherent characteristic, which supports the current findings. Plants free from late blight disease produced large tuber sizes due to having healthy leaves, a high leaf area index, which produces more photo assimilates for tuber enlargement, and more tubers per plant (Mijena et al., 2022; Oliveira et al., 2021).
Table 17
The interaction effect of variety and IBA concentration on yield of large-sized tuber (ton ha-1)
Variety
|
IBA concentration (ppm)
|
0
|
3000
|
6000
|
9000
|
Belete
|
8.22ijk
|
15.14def
|
15.33def
|
21.34abc
|
Gudenie
|
7.16ijk
|
8.99hij
|
9.65ghi
|
10.47fghi
|
Jalenie
|
13.76defgh
|
15.86de
|
18.25bcd
|
14.49defg
|
Shonkolla
|
11.56efghi
|
16.79cd
|
15.40de
|
14.61def
|
Gusa
|
14.17defg
|
16.92cd
|
18.30bcd
|
14.11defg
|
Gera
|
16.78cd
|
17.63cd
|
23.15ab
|
24.17a
|
Dagim
|
4.59jk
|
3.66k
|
3.77k
|
3.47k
|
Ater Ababa
|
8.22ijk
|
7.73ijk
|
8.98hij
|
7.83ijk
|
CV (%)
|
23.49
|
LSD (5%)
|
4.92
|
Level of significance
|
*
|
*Significant at P < 0.05; Means with followed by the same letter(s) in rows and columns are not significantly different at 5% level of significance.
3.2.6. Total tuber yield
The main effect of variety and IBA concentration was highly significant (P < 0.01), but the interaction between variety and IBA concentration did not show a significant difference in total tuber yield..
The main effects of variety and IBA concentration on total tuber yield are given in Table 18. Variety Gera had the highest total tuber yield (25.74 tons ha− 1), followed by variety Jaline (22.71 tons ha− 1), and the lowest total tuber yield variety Dagim (5.90 tons ha− 1). Significant differences in total tuber productivity among the varieties may be attributed to genetic differences. This suggestion is in accord with that of Postma et al. (2021),who reported significance with optimum canopy coverage because more light is intercepted at optimum LAI due to that more photosynthesis.
The increased application of IBA from 0 (control) to 6000 ppm treatment significantly increased total tuber yield from 14.95 to 19.16 tons ha− 1, with a significant difference of 4.21 tons ha− 1. However, further increasing IBA beyond 6000 ppm IBA decreased total tuber yield (Table 18). This might be due to the role of IBA in the transplant survival with the quality roots. This suggestion is consistent with that of Yousry et al. (2018), who reported that quality roots resulted in a significantly higher total tuber yield from the optimum application of IBA. The increased yield at higher transplant survival may be due to the higher LAI tuber using more assimilation.
Yield per unit area is the end product of components of several yield-contributing characteristics, which are highly influenced by genetic and environmental factors (Alam et al., 2020). The observed simple linear correlation analysis indicated that total tuber yield was positively and highly significantly correlated with total tuber number (r = 1), positively and significantly correlated with tuber weight per plant (r = 0.92), large tuber size (r = 0.56), LAI (r = 0.54), average tuber weight (r = 0.46), plant height (r = 0.36), and transplant survival (r = 0.27). However, the number of affected tubers by late blight was highly significant and negatively correlated with total tuber yield (r = − 0.60).
Table 18
Effects of variety and IBA concentration on Total tuber yield (ton ha-1).
Variety
|
Total tuber yield (ton ha-1).
|
Belete
|
20.21bc
|
Gudenie
|
13.30d
|
Jalenie
|
22.71b
|
Shonkolla
|
18.31c
|
Gusa
|
20.27bc
|
Gera
|
25.74a
|
Dagim
|
5.90e
|
Ater ababa
|
14.19d
|
Siginificance
|
**
|
LSD (5%)
|
2.86
|
IBA conc. Ppm
|
|
0
|
14.95b
|
3000
|
17.95a
|
6000
|
19.16a
|
9000
|
18.25a
|
Significance
|
**
|
LSD (5%)
|
2.02
|
CV
|
19.96
|
** Highly significant; Means followed by same letters within a column in a given treatments are not significantly different at P < 0.05 |
3.2.7. Tubers infected by the late blight disease
The main effects of variety and IBA concentration, as well as the interactive effect, significantly influenced (P < 0.01) the percentage of tubers infected by the late blight disease. The highest infection by late blight disease (18.33%) was observed on Dagim treated at 3000 ppm IBA, followed by Dagim not treated by IBA (11.95%), and the lowest (0%) was on varieties Jaline, Gusa, and Gera at all IBA concentrations, Gudine at 3000 ppm and 6000 ppm, Shonkola at 6000 ppm, and AterAbeba at 3000 ppm. Except for the variety Dagim at all IBA concentrations, the other treatments did not differ significantly (Table 19). Variations in tuber infection percentage by late blight disease may be due to inherent characteristics of the cultivars, and the IBA effect on transplant survival, which indicates that a more dense plant favors condensation of moisture that facilitates the infection by late blight on plants (Kassaw et al., 2021; Pacilly et al., 2019).
Table 19
The interaction effect of variety and IBA concentration on tuber infection percent by late blight disease.
Variety
|
IBA concentration (ppm)
|
0
|
3000
|
6000
|
9000
|
Belete
|
1.41d
|
0.68d
|
0.35d
|
0d
|
Gudenie
|
0.49d
|
0d
|
0d
|
0.61d
|
Jalenie
|
0d
|
0d
|
0d
|
0d
|
Shonkolla
|
0.72d
|
1.13d
|
0d
|
0d
|
Gusa
|
0d
|
0d
|
0d
|
0d
|
Gera
|
0d
|
0d
|
0d
|
0d
|
Dagim
|
11.95b
|
18.33a
|
11.24b
|
9.32c
|
Ater Ababa
|
0.98d
|
0d
|
0.38d
|
1.05d
|
CV (%)
|
49.29
|
LSD (5%)
|
1.47
|
Level of significance
|
**
|
** Highly significant at P < 0.01; Means with followed by the same letter(s) in rows and columns are not significantly different at 5% level of significance.
3.2.8. Deformed tubers
The interaction between variety and IBA concentration significantly (P < 0.01) influenced percentage of deformed tubers. The highest deformed tuber (9.04%) was observed from Ater Abeba treated at 3000 ppm IBA; however, there was a non-significant difference from Dagim untreated and treated at 6000 ppm IBA. whereas the lowest (0%) deformed tubers were recorded for Jaline at all IBA concentrations, Gudine at 3000 ppm and 6000 ppm, Shonkola except untreated IBA, Gussa at all levels of IBA (Table 20). This variations may be due to inherent characteristics of the cultivars, and the IBA effect on transplant survival and late blight incidences.
Significant variations in the deformed shape of tubers among varieties were reported by Afanasenko et al. (2022). Furthermore, Getachew et al. (2019)noted that the deformed-shaped tubers increased in association with late blight disease.
Table 20
The interaction effect of cultivars and IBA concentration on deformed tubers percentage
Variety
|
IBA concentration (ppm)
|
0
|
3000
|
6000
|
9000
|
Belete
|
2.94defg
|
3.96def
|
0.35i
|
1.50fghi
|
Gudenie
|
0.99hi
|
0i
|
0i
|
1.23ghi
|
Jalenie
|
0i
|
0i
|
0i
|
0i
|
Shonkolla
|
3.05def
|
0i
|
0i
|
0i
|
Gusa
|
0i
|
0i
|
2.31efgh
|
4.03d
|
Gera
|
0.52i
|
0.74hi
|
0i
|
0i
|
Dagim
|
8.26ab
|
6.69bc
|
7.49abc
|
3.63de
|
Ater Ababa
|
5.78c
|
9.04a
|
5.88c
|
3.53de
|
CV (%)
|
47.45
|
LSD (5%)
|
1.72
|
Level of significance
|
**
|
** Highly significant at P < 0.01; Means with followed by the same letter(s) in rows and columns are not significantly different at 5% level of significance.