Evaluation of Seed Quality Attributes of Sorghum Germplasm Accessions from Eastern, Coastal and Nyanza Regions, Kenya

Sorghum (Sorghum bicolor L.) is an important cereal crop in Kenya. Despite the crops importance, the yields attained by farmers in Eastern, Coastal and Nyanza regions of Kenya remain low. Access to good quality seeds of sorghum is one of the constraints facing the subsistence farmers. Good quality seed is important for increasing yield to attain food security. The aim of this study was to evaluate quality attributes of the seed used by farmers. A total of 108 germplasm accessions were obtained from 76 farmers. The seeds were tested for time and percentage of germination, seed vigour index, shoot and root dry weight. Data collected was subjected to analysis of variance. Means were separated using Fisher’s Least Significance Difference test at p ≤ 0.05. Seed samples of 26 accessions attained germination percentage below stipulated standards by Seeds and Plant Varieties Act CAP 326. Majority of seeds showed longer mean germination time with only nine accessions germinating in less than ten days. Seed vigour index was relatively high in most of the accessions, while biomass accumulation varied from high to very low among accessions. Though most of the seeds attained a high germination percentage, about 92% of seeds showed longer mean germination time. The environmental conditions in the fields, pre and post harvest handling practices impact on the seed quality hence the wide variability in germination percentage, germination time, seed vigour index and dry matter accumulation. Therefore the need to improve quality of seeds used by subsistence farmers by providing extension services on best pre and post harvest handling practices. Increasing production of sorghum in these regions will contribute significantly towards realizing food security. Further analysis could be carried out on genetic and sanitary quality aspects of the seeds planted by farmers in Eastern, Nyanza and Coastal regions.

and farmer-to-farmer seed exchange networks (Ochieng et al., 2011;Muui et al., 2013Muui et al., , 2019. Where formal seed is available, the farmers cannot afford due to high seed prices. The informal seed supply system consists of farmer-managed seed production activities and is based on indigenous knowledge and local diffusion mechanisms. Maintaining crop production in terms of yield and quality grains which give the farmer maximum return requires good seed which carries the genetic, physiological, and physical quality aspects (Muasya et al., 2008;Ahmed et al., 2009). Good seed requires constant care to prevent loss of quality and to ensure high yield for farmers. Seed deterioration usually commences at physiological maturity and continues during harvest, processing and storage and is governed by the genetic constitution, environmental factors during seed development and storage conditions (McDonald, 1999;Muasya et al., 2008).
Seed quality is considered as an important factor for increasing yield unit area to attain food security (Badigannavar et al., 2016). Quality seeds have the ability for efficient utilization of available inputs such as fertilizers and moisture eventually maximizing yields (Jisha et al., 2013). Use of poor quality seed is one of the constraints to sorghum production in Kenya where majority of the farmers rely on the informal seed supply sources resulting to low yields (Ochieng et al., 2011). Poor seed quality at farm level is caused by poor drying of harvested grains, threshing practices, storage conditions (Harrison and Perry, 1976;Songa et al., 1995). Also, many subsistence farmers in Sub-Saharan Africa do not apply fertilizers to their farms (Jama et al., 1998;Ochieng et al., 2011;Muui et al., 2019). This is attributed to the fact that sorghum is often grown under marginal rainfall conditions and fertilizer prices are unfavourably high in relation to sorghum grain price. This practice of using little or no fertilizer affects both seed quality and yield of the crop negatively (Swinkels et al., 1997).
Sorghum landraces germplasm provides a great genetic variability with high preferences based on unique characteristics (Ng'uni et al., 2012). Sorghum being a food crop with the potential of alleviating the problem of food insecurity, there is need for using quality seeds for sustainable production by the subsistence farmers (Mwadalu and Mwangi, 2013). This study aimed at assessing the quality of on farm saved sorghum seeds used by farmers at eastern, coastal and nyanza regions of Kenya. A total of 108 germplasm accessions were collected from farmers to determine germination percentage, germination time, seed vigour index, seedling shoot and root dry weight.

Description of experimental Site
The experiment was carried out in Kenyatta University situated in Nairobi County about 20 Km from Nairobi city along Nairobi-Thika road between August and October 2018. The county is characterized by a warm climate with temperatures varying between 12°C and 18.7°C. The rainfall aggregate for the county is 1,000 mm per year. Its geographical coordinates are 1° 10' 0" S, 36° 50' 0" E with an elevation of 1,720m above sea level (ASL). The area has a bimodal rainfall pattern with an average of 1,000 mm per annum. The long rains occur between March and May while the short rains set in between October and December. The soils are acrisols, alisols, lixisols and luvisols (Shisanya et al., 2006).

Experimental Layout and Data Collection
The experiment was carried out in the laboratory and in a greenhouse. The two experiments were arranged in a Complete Randomised Design. A total of 108 sorghum germplasm accessions obtained from farmers comprising of 41 accessions from Eastern, 25 from Nyanza and 42 from Coastal regions of Kenya were used. The sorghum germplasm was collected from farmers in 2018 while conducting a baseline survey to assess the production systems for sorghum in the three regions (Muui et al., 2019).

Crop Management and Data Collection
Germination percentage and mean germination time experiments were carried out in the laboratory while seed vigour index, shoot and root dry weight was done in the greenhouse.

Germination Percentage
From each of the 108 sorghum germplasm accessions, a sample of 400 seeds was selected at random from the 1,000-seed weight lot and grouped into four replicates of 100 seeds (ISTA, 2012). Each of the four replicates was placed in a germination tray with sterilized filter papers moistened with distilled water as a growth medium. The trays were illuminated with light during the whole period and temperatures maintained at 25±5 0 C. Distilled water was added as necessary to maintain the correct moisture content. Germination count was done at the end of the fourth day and seedling evaluation at the end of the tenth day. Germination percentage was calculated as follows: Germination percentage (%) = (Number of seeds germinated/Number of seeds sown) x100

Mean Germination Time (Days)
The seeds used for testing germination percentage were also used in the determination of mean germination time. Emerged seedlings in each container were counted daily at an interval of 24 hours from the first day to the day no more germination occured. The mean germination time was calculated using the method described by Khan et al. (2010) as follows: Mean germination time = (No. of germinated seedlings/Total no. of seeds sown) x Days after sowing

Seed Vigour Index
From the 108 sorghum germplasm accessions, a sample of 200 seeds was selected at random from 1,000-seed weight lot (same seed lot used for germination) and grouped into four replicates of 50 seeds. The fifty seeds were placed in plastic containers (pots) with sterilized forest soil as a growth medium for 21 days. Number of germinated seeds was recorded every 24 hours. Watering was done on daily basis and pots kept weed free throughout the experimental period. After 21 days, the seedlings were uprooted, soils washed off and a ruler used to measure the seedling height. Seed vigour index determination was done using the equation cited by Zhu et al., (2010) as follows: Seeed vigour index (SVI) = Seedling height ×∑ (number of germinated seedlings by end of test period/days after sowing)

Shoot and Root Dry Weight (Grams)
Seedlings used for seed vigour index were also used for dry weight measurement. A random sample of twenty five seedlings was taken and separated into shoot and root, dried in a forced-air oven at 72 0 C for 48 hours. The samples were fully dried such that no significant changes occurred before the tests were done. The dried shoots and roots were weighed using an electronic balance (model 6354) and recorded in grammes.

Data Analysis
The data collected on germination percentage, germination time, seed vigour index, shoot and root dry weight were managed in the Ms excel spreadsheet and subjected to one-way analysis of variance (ANOVA) using Statistical Analysis Software (SAS) version 9.1. Means were separated using Fisher's Least Significance Difference (LSD) test at p≤0.05.

Germination Percentage
There were statistical differences (p≤0.05) in the germination percentage of the germplasm accessions evaluated across the three regions of Kenya; Eastern (41), Nyanza (25) and coast (42). In the Eastern region, thirty-eight of the tested accessions had more than 70% while three accessions had less than 70% with local102 having the lowest germination (18.67%) ( Table 1). On the other hand, 29 of the tested accessions from coastal region had 70% germination whereas 13 accessions showed less than 70% germination with the lowest, 18%, from local accession gaddamssp38. In Nyanza, 15 of the tested accessions had 70% germination. A relatively lower than 70% germination percentage was observed in ten germplasm accessions, but Ngware spp2 recorded the lowest germination percentage of 18.0%.

Seed Vigour Index (SVI)
Different germplasm accessions exhibited significant differences (p≤0.05) in seed vigour index (SVI) in Eastern, Nyanza and Coastal regions (Table 3). Local103 accession was superior with an SV1 0f 3499.3 from Eastern region, while local102 had the lowest SVI of 322.3. At Coastal region, SVI superiority was exhibited by accession localvariety41 that recorded 4392.0 followed by the localvariety42 with 4044.3, while Gadam spp38 had the lowest SVI of 507.5. At Nyanza, Nyakabala spp9 and Ochuti spp15 were the superior accessions with a high SVI of 4080.9 and 4060.0 respectively, while Serodo Spp24 had the least SVI of 2119.8.

Shoot Dry Weight (SDW)
There was a significant difference (p≤0.05) in shoot dry weight among various germplasm accessions from Eastern, Nyanza and Coastal regions (Table 4). In Eastern, Ciumbichi91 accession had the highest shoot dry weight of 0.046g, mixed30 accession from Coastal region was the leading in shoot dry weight of 0.073g while, at Nyanza, Ochuti15 was superior, recording 0.075g. Germplasm accessions with the least shoot dry weight were Gadam spp27 (0.0137g) and Seredo spp24 (0.0180g) from Coastal and Nyanza regions respectively.

Root Dry Weight (RDW) (Grams)
Root dry weight exhibited significant differences (p≤0.05) among germplasm accessions from Eastern, Coastal and Nyanza regions (Table 5). Vaasya92 (0.0152g), Nyakabala spp9 (0.0188g) and local variety45 (0.039g) from Eastern, Nyanza and Coastal regions respectively had more root dry weight. Kilala74 in Eastern recorded the least root dry weight of 0.0020g while in Nyanza Seredo spp 24 had the least weight of 0.0036g.

Discussions
In this study, there was a high variability in the germination percentages for the sorghum seeds obtained from Eastern, Coastal and Nyanza regions of Kenya. A majority of the seeds exhibited a high germination percentage of 70% which is within the set standards by the Seeds and Plant Varieties Act of CAP 326 of the Kenyan constitution for sorghum varieties. However, part of the germplasm had low germination percentages indicating presence of low quality seeds used by farmers. Previous studies have reported that farmers obtain sorghum seeds from previously saved seeds, local markets, borrow from neighbors (Ochieng et al., 2011;Catherine et al., 2013;Kange et al., 2014;Muui et al., 2019). Majority of subsistence farmers in semi arid areas produce crops without fertilizers (Jama et al., 1998;Muui et al., 2013). Results of a baseline survey assessing production systems at coastal, Nyanza and eastern regions revealed that most farmers do not use fertilizers (Muui et al., 2019). This results to low yields and poor quality seeds since most soil nutrients have already been depleted (Songa et al., 1994;Craine et al., 2018). High humidity under elevated temperatures in these regions may have contributed to rapid deterioration of the seeds. There is evidence that elongated exposure to high temperatures and moisture would significantly reduce seed germination potential in many crops (Nagel et al., 2016). Besides, post-harvest seed handling and packaging also influence the rate of seed deterioration and hence has a direct impact on seed germination potential (Kange et al., 2014). Studies conducted in eastern, coast and Nyanza reported that most farmers have low education and therefore do not understand the best agronomic and post harvest handling practices which could help increase the quality of seed (Muui et al., 2013;. The mean time of germination for a seed indicates the time taken by a seed to develop critical structures crucial for germination success, survival, and for faster and uniform establishment. In this study, the mean germination time observed ranged from short, moderate to long. The shorter the mean germination time, the greater the seed vigour. A prolonged MGT may be an indication of deteriorated seed quality as a result of exposure of the seeds to harsh or unfavourable conditions in the field and after harvesting (Bewley and Black, 2012). Such conditions slows the rate of emergence and growth of the seedlings (Amirmoradi and Feizi, 2017); and eventually limits the seedlings from taking advantage of the available nutrients and resources for maximum yield within a short time (Bradford, 2002).
The seed vigour index variation in this study could be attributed to the diverse conditions during production, source of seeds and post harvest handling practices. Increased seedling vigour is an indication of effective germination, seedling emergence early seedling growth and improved grain yield (Lamichhane et al., 2018). Harsh conditions during the late stage of seed development might have also contributed to hormonal imbalance within the seeds which promotes physiological seed dormancy (Cotado and Munné -Bosch, 2020). Longer storage is associated with deterioration of seed stored microRNAs and other important proteins that have a role in the maintenance of high seed viability (Sahu et al., 2017;Sano and Rajjou, 2020).
The shoot biomass of seedlings varied from high to low attributed to pre and post harvest handling practices. A high shoot biomass is an indicator of increased seed vigour and subsequent crop growth cycles (Maucieri et al., 2016). Rapid development of the shoot is associated with the development of more leaves, which is important for the interception of photosynthetic active radiation that enhances rates of photosynthesis resulting in high biomass accumulation (Ceotto et al., 2013). Furthermore, genotypes with higher shoot dry matter have the capability of withstanding drought due to improved water and nutrient use efficiency (Verma et al., 2018). Majority of the germplasm displayed moderate to low root dry matter. Low root biomass has been reported to be as a result of reduced root growth in germplasm consisting of low quality seeds (Joshi et al., 2017). According to Blaha and Pazderu (2013), high seed quality leads to development of seedling with roots of greater biomass an indication of ability to withstand stress condition and also facilitate formation of high quality grains for the subsequent generations.

Conclusion and Recommendations
The ability of sorghum to perform well in semi arid areas makes it an important cereal crop to achieve food security. Farmers in Eastern, Nyanza and Coastal regions plant sorghum seeds obtained from diverse informal sources. The environmental conditions in the field and, pre and post harvest handling practices impact on the seed quality hence the wide variability in germination percentage, germination time, seed vigour index and dry matter accumulation in seedlings. This shows the need to improve and monitor the quality of seeds used by subsistence farmers. The quality of sorghum seeds could be improved by providing extension services on best pre and post harvest handling practices. Increasing production of sorghum in these regions will contribute significantly towards realizing food security. Further analysis could be carried out on genetic and sanitary quality aspects of the seeds planted by farmers in Eastern, Nyanza and Coastal regions.