Inuence of Storage Conditions on the Quality of Cotton Seeds in Benin Republic

Background The availability of good quality seeds is synonymous with improved farming, especially cash crops such as cotton. However, serious problems with seed germination have been reported recently by cotton farmers in Benin Republic. The assumptions formulated at the base with regard to this situation remain to be veried technically. Thus, this study aims to evaluate the inuence of storage conditions on the quality of cotton seeds in Northern Benin. Temperature and relative humidity were assessed followed by a seed sampling sequence in seven (07) cotton seeds stores according to three main periods, ranging from the establishment in conservation to the following seasonal production. Germination tests were then carried out on each sample followed by data analysis using R and Minitab17 software. Results There is a large variation in the germination rate of cotton seed during their storage period. The probabilities values (Pvalue1 = 0.023, Pvalue2 = 0.001 and Pvalue3 = 0.038) respectively associated with the three samples and the various coecient of variation (CV) between stores (CV1 = 2.42%, CV2 = 7.1% and CV3 = 8.88%) explain a signicant difference not only between the stores but also from one sample to another with regard to sampling periods. There is a strong progressive decrease in seed germination (Germination rate 1 > Germination rate2 > Germination rate3), which is responsible for the failure observed by the growers during sowing. Thus, seeds lose an average of 15% of their initial germination capacity already at one month of storage. This is generally negative due to all the storage conditions and system in the stores. in stores view quality Benin.

in the stores.
Conclusions The excessive increase in temperature and the considerable decrease in relative humidity in stores are the main factors of signi cant loss of germination capacity of cotton seeds. In view of this situation, it is desirable that technical measures be taken in this direction in order to better preserve the quality of the seeds made available to producers for an optimization of the cotton sector in Benin.
Background The farmer's success depends on the quality and quantity of seeds for intensive production [1]. For a long time, several studies have particularly aimed at improving the quality of seeds of the main food crops in Africa and worldwide [2]. Nowadays, the economic importance attached to the cash crops among which the cotton plant is made, makes think of possible programs of selection or improvement of their respective sectors. Varieties with high agronomic performance have therefore been created and popularized [2,3]. In most African Franc Zone (AZF) countries including Benin, Burkina Faso, Mali, Chad and Togo, cotton is at the root of development and contributes signi cantly to the employment and income of the population in rural areas [4]. Its production is exported to more than 95% and the group of AZF countries account for nearly 14% of world exports [5].
In Benin, cotton plays a very important role in economic growth, with a contribution of more than 32% to gross domestic product, representing 90% of export earnings, 45% of tax revenue excluding customs duties and 60% of the industrial fabric [6; 7]. The revenue from the cultivation of cotton contributes to the creation of numerous socio-community infrastructures [7] and the sector therefore bene ts from signi cant support [4]. Since it was considered to be the most important economical crop in Benin, several breeding programs were devoted to cotton seeds quality improvement [8]. Despite of efforts supplied, farmers are still reporting serious germination issues with unknown sources. Therefore, seeds are very well tested with high germination rate before their distribution to the producers' districts for storage [9; 10]. This problem, becoming more and more alarming in recent growing seasons, it is therefore necessary for the scienti c community to intervene in order to identify the main reasons for the considerable loss of germination power of the seeds distributed to producers. Regarding its importance in agriculture, seed sector must be an area under high public control [1; 11]. An improvement in seed management is necessary so as to limit the production costs of cotton seeds and increase the national production [1]. To particularly solve this problem related to the quality of seeds, the diagnosis of the devices involved in the production of seed cotton is essential.
This study aims to evaluate the seed germination rate during the storage period in the different villages of Cotton Producers' Cooperatives (CVPC) stores until the start of seedlings. This will allow us to appreciate the in uence of storage infrastructures on the quality of cotton seeds in order to make proposals that will allow a rational use of seeds. Speci cally we will have to analyze the storage infrastructures of cotton seeds in the N'dali and Sinendé districts (i); to evaluate the germination capacity of cotton seeds during storage period in central stores (ii) and to propose approaches of solutions to the likely constraints of storing cotton seeds (iii).

Results
Variability of thermal and water conditions inside storage structures.
The highlighting of the thermal and hydrous variants of the seeds during the conservation period, allowed us to realize the graph below. It emerges that there is a thermal variability in the stores which would act signi cantly on the moisture content of seeds in storage. The thermal gradient and that of moisture of the seeds evolve in opposite directions. So the hotter the store is, the lower is the moisture content of the seeds. This thermal variation would be due to the alternation of diversi ed periods of sunshine of the environment during the period of storage. This is all the more true since this conservation period generally coincides with the dry season during which high temperaturees are often recorded. The second sampling, which coincides with the sowing period, is characterized by a higher temperature (31.59 ° C) with a relative humidity of 20.16%. This analysis shows that the temperatures and moisture levels of cottonseed stored vary from one store to another and between districts (Fig. 1). Variation in germination rate of seeds at the beginning of conservation. Table 1 below summarizes the probabilities derived from analysis of variance (ANOVA) on seed germination rates from different storage locations. Indeed, it appears that there is a signi cant difference at the 5% threshold between the seed germination rate (Pvalue = 0.02). Moreover, the Student-Newman-Keuls comparison test reveals a homogeneity of seed germination rate at the threshold of 5%. The average seed germination rate of Fo_Boure, the Municipal Agricultural Development Sectors (SCDA) of N'dali, Sonnoumon and Soka stores are virtually identical. The slight difference is therefore observed only at the level of seeds taken from SCDA Sinendé, Sekere and Yarra stores with a low coe cient of variation (2.42%). Thus, the highest rates are those of Sonnoumon seeds (73.25%) while the lowest are recorded in SEKERE (69.75%). This translates that at the beginning of conservation, the seeds always keep their initial germination rates and know no disturbance of the environment. Temporal evolution of seed germination rate Analysis of the variance showed a signi cant difference at the 5% threshold for the tests (Pr (F) = 0.001), this con rms that the average seed germination rate varies according to the stores. So, seed storage conditions usually vary from one store to another and over time. The seeds are preserved for this purpose in a diversi ed way. This re ects a likely and speci c in uence at each store according to the conditions imposed on the seeds. The associated comparison test stipulates a strong heterogeneity within the stores. The lowest germination rates are recorded in the third sample. The in uence of storage conditions varies from one store to another and becomes more and more critical as time increases.  Comparative analysis of the three samplings with regard to estimated germination rate

Discussion
The linking of the information collected as well by the direct observations made in each targeted store and the germination tests carried out, enables us to con rm or invalidate the results of several research projects carried out on organic seeds. Thus, the high variability of the temperature and aridity index observed in all the stores is only a standard phenomenon con rmed by the work of several authors [7,8,11]. The increase in temperature is not only related to storage structure but also to the faculty of seed cotyledons to prolong the evapotranspiration of the fresh material usually sip [12,13]. This naturally creates a gradual increase in temperature that tends to warm the environment, thus contributing to a signi cant drop in the aridity index [8]. In addition, the in uence of storage conditions, in particular the quality of the roof of the storage device and the importance of spacing created between seed lots, must be noted. According to several scienti c studies, direct disposal of bags containing seed cotton on a plastered oor is a practice to avoid to ensure good conservation of seeds [7,14]. It is therefore very essential to nd an alternative, usually that involving strong and resistant supports on which the bags of seeds will be placed in order to facilitate a good ventilation through. These same approaches have already been proposed to seed producers of several other speculations such as rice, maize and cowpea (15).
Admittedly, at the beginning of storage, the non-signi cance of the variation in the germination capacity of the seeds taken from each store is all the more justi ed, because the time remains too limited to notice any in uence of the storage device. The seeds then behave as treated under the same conditions and until now have not undergone any unusual pressure that may impair their germination [16,17]. These notions remain standard to most agricultural speculations. In 2004, during their research work on the contribution to the analysis of quality problems in the cotton sector in Benin, especially the seed subsystem, Sekloka et al. (2008) deduced that the dormancy of seed cotton is positively correlated with their shelf life [8]. The gradual fall in germination capacity of seeds is then justi ed after a month or more. The variations observed between the stores can be justi ed on the one hand because of the diversi ed sources of seed and on the other hand the quality of the storage device. Thus, in Benin, the quality of seed cotton varies according to the localities, especially the four agroecological zones [18]. The seeds being of a certain exigency and of a thermal sensitivity, the variabilities of the ambient temperatures of the stores would thus be the main cause of the variations observed on their germination rate.
Seed management requires some care at the store during the storage period. Taking responsibility for proper store maintenance was not effective in all structures visited in this study. Thus, the more the global humidity temperature conditions of the stores become critical the more the seeds are negatively affected.

Conclusion
The general objective of this study was to determine the in uence of storage conditions on the quality of cotton seeds. The methodological approach adopted really allowed us to highlight the effect of conservation conditions on the germination of seeds. The results obtained made it possible to draw a certain number of conclusions thus answering this scienti c curiosity. In sum, it has been found that conservation conditions affect the quality (germination capacity) of seeds. The main factors are thermal uctuations, which have a signi cant effect on the humidity of seeds in storage, thus affecting their germination capacity. In addition, it has been reported that the longer the storage time, the lower the germination capacity of seeds becomes.
Given the results of this study, we recommend that the likely measures to correct this weakness be strongly oriented towards development of a general technical sheet on the standards required for seed conservation, the constant watch of the managers of the cotton sector in the storage structures in order to correct the failures over time before they are too critical.

Methods
Presentation of the study environment.
The studies were conducted in the Department of Borgou and more precisely in the communes of N'Dali and Sinendé. The commune of N'Dali is limited to the North by the communes of Bembèrèkè and Sinendé, to the South by the communes of Parakou and Tchaourou, to the East by the municipalities of Nikki and Pèrèrè and to the West by the communes of Djougou and Péhunco. It covers an area of 3748 km2 representing 14.50% of the area of the department and 3.27% of the total area of Benin. By contrast, Sinendé commune is located in the north-west of the Borgou department and covers an area of 2,289 km2. It is bounded on the north by the commune of Gogounou, on the south by that of N'Dali, on the east by Bembèrèkè and on the west by the communes of Ouassa-Péhunco and Djougou. It is 623 km from Cotonou (economic capital of Benin) and about 150 km from Parakou, capital of the department.

Plant material, choice and brief description of identi ed stores
The cotton seeds constituting the plant material used within the framework of this study are those of the variety OKP 768 cultivated in the department of Borgou, more precisely in the districts of Sinendé and N'dali. The samples were taken free of charge from seven (7) conservation stores under the authorization and supervision of municipal o cials and those of the seed cotton sector of the two target municipalities. It should also be noted that these stores are public, where several scienti c researches are currently taking place helping to resolve the germination problems reported by producers. So any particular authorization is needed. In N'dali, two stores are visited (the Municipal Agricultural Development Sectors "SCDA" of N'dali stores and the Sonnoumou village store) while ve (5) stores are sampled in Sinendé (SCDA of Sinendé, villages of Fo Bouré, Sekere, Soka and Yarra). A general inspection of the stores was carried out at the beginning of the seed storage for the description of storage tools and system used (Table 4). At each sampling and 15 days later, the temperature and relative humidity were respectively taken according to the o cial method described by Pierrot Michaël (2016) in each of the stores concerned and more precisely in the seed bags randomly selected and marked throughout the study period.
The germination tests were carried out in germination tanks at the Municipal Agricultural Development Sectors (SCDA) of each commune. A sample of 100 g of seed was made in ten (10) different bags of 40 kg randomly selected by visited store. These nal samples collected were then subjected to germination tests in order to evaluate their germination capacity. This operation was repeated over three (3) major periods in order to highlight the spatio-temporal interactions in uencing seed germination. The rst test carried out just at the beginning of the storage period was followed by the two others, which intervened respectively within 30 days. Stripping ten (10) days after sowing allowed the data to be collected and analyzed using appropriated statistical software.

Data analysis.
The collected data has been entered into the Excel spreadsheet, gures and tables are also done. R software [19] was used for analysis of the variance (ANOVA) was done in order to highlight the signi cance of the variation of the germination rate between the storage magazines on the one hand and the other between the different samples. The Student-Newman-Keuls comparison test and boxplots were also performed using R software to compare the average germination rates of the seeds collected in each of the targeted stores for categorization.  Figure 1 Evolution of temperature and aridity index (Source: eld data, 2019)