Identification and characterization of Sorghum (sorghum bicolor (l.) Moench) landraces and improvement of on-farm seed production in Eastern Kenya
Muui, Catherine W.
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Sorghum (Sorghum bicolor (L.) Moench) is an under-utilized crop that is tolerant to drought, flooding, saline-alkaline, infertile soils and high temperature. Farmers maintain landraces through preference selection and obtain seed from different sources. Local germplasm provides greater genetic variability and may provide useful traits to broaden the genetic base. Decline in use may erode the genetic base, preventing use of distinctive traits in crop adaptation and improvement which may result in their disappearance. There is also lack of information on on-farm seed production strategies leading to lack of quality seeds, information on use and improved cultural management. The objectives of this research were to identify and determine the key sorghum landraces grown in lower eastern Kenya, establish their diversity, quality levels for seed used by farmers, come up with pre and post harvest handling methods that could be used by farmers to improve on-farm seed quality. A baseline survey was conducted and landraces collected in various agro-ecological zones of lower eastern Kenya. Morphological and molecular characterization, varietal assessment in different ecozones and seed quality tests were done. Two varieties were used to test the effect of location of seed on different panicle sections, storage containers, and seed drying at different times of the day for different duration on seed quality. Results showed that farmers maintain a diversity of landraces unique in adaptation, food quality, grain yield, quality of harvested products and biotic stress resistance. They obtain seed for planting from informal systems of which 36% recorded low viability and 38% low vigor with 85% of seed samples contaminated with either Fusarium sp., Penicillium sp., Rhizorpus sp., Aspergillus niger and Aspergillus flavurs. The landraces recorded low heterozygosity indicating high level of stability in the population. Landraces clustering based on geographical locations was distinct with some overlaps across the locations. Variations were observed for leaf and mid rib colour, panicle compactness, awns and seed colour. A wide range of quantitative characters was observed between the accessions. The lower third part of the panicle recorded the highest seed viability and vigor indicating deterioration had not occurred compared to other panicle parts. The highest seed viability and vigor was realized in seed stored in the gourds and the seed stored for four weeks. Significant differences (P=0.05) were observed in leaf area, leaf, shoot and root length, and in dry matter accumulation among the seeds sampled after one month, two months and three months after storage. The seed viability and vigor decreased with increase in time the seed was sun dried but had no negative effect on seed dried in the seed drier. Farmers maintain a diversity of landraces, and since the region has a high agricultural potential, productivity for better food security could be improved by use of locally available germplasm adapted to this particular environment. Sorghum production may be effectively increased by use of improved production technologies and teaching farmers the importance of the crop to increase the production area. Seeds used by farmers to plant their crop are of poor quality in relation to germination, vigor and pathogen infestations