No abstract

Soybean seeds loss viability very rapidly during ambient storage in the tropical and sub-tropical environments. In this study, interrelationship between seed coat permeability and viability over periods of ambient storage was assessed using a set of 217 recombinant inbred lines (RIL) developed from an inter-specific cross between wild type (Glycine soja) accession DC2008-1 and cultivated (G. max) variety DS9712. G. soja seeds were tiny, black, impermeable and highly viable while G. max seeds were large, yellow, permeable and poorly viable during ambient storage. Seed coat permeability and viability of the fresh, one-year and two-year-stored seeds (stored in room temperature, av. 25±2°C and 65±5% RH) were tested as per standard protocols in completely randomized design with two replications. Significant variation was found among genotypes for the seed viability, permeability, periods of storage and their interactions. Permeability of the seed coat increased with the period of storage. In the fresh, one-year and two-yearstored seeds, the seed coat permeability was 62.87, 75.17 and 90.52%, respectively. Viability of the seeds was negatively correlated with period of storage and seed size. In the fresh, one-year and two-year-stored seeds, average viability was 90.7, 75.6 and 54.1%, respectively. Scanning electron microscopy (SEM) indicated presence of intact hilum, strong hourglass cells and non-cracked seed coat in the highly viable seeds. A set of 24 RILs were found that maintained higher viability (>80%) with varying degree of permeability after two years of storage. Among the highly viable RILs, more were black seeded. RIL Nos. 7-12-3, 7-24- 1, 13-2-2, 13-31-4 found to maintain both viability and permeability in higher order during storage and would pave the way for development of soybean genotypes with high viability and permeability.

Soybean seed loses viability rapidly during ambient storage in tropical and sub-tropical climate. Understanding genetic mechanisms would enable enhancing storage life of seeds through breeding approach. In this study, attempt was made to identify quantitative trait loci (QTL) controlling viability of seeds using an inter-specific recombinant inbred line (RIL) population and SSR markers. Significant variation was observed among the RILs for seed viability after one and two years of ambient storage. RILs with more than 90% seed viability after two years of storage were identified. Genetic polymorphism among the RILs was very high (52.9%). Two QTLs viz., qSv2.1 and qSv14.1 were mapped on Chromosomes, 2 and 14 after one year of storage that explained 10.65% and 5.35% of the phenotypic variation, respectively. Two more QTLs viz., qSv2-1 and qSv14-1 were mapped for seed viability after two years of storage of which qSv2.1 (PVE=6.0%) was consistent and the qSv14.1 (PVE=8%) was novel. QTL and linked markers identified in the study would be useful in soybean breeding for enhancing seed viability during ambient storage.

Seed coat impermeability (SCI) in soybean is associated with seed viability under storage and quality of processed products. Understanding genetics and identification of linked molecular markers would facilitate need-based utilization of seed coat impermeability. Two impermeable wild type (G. soja Sieb. and Zucc.) accessions viz. PI 424079 and PI 136620 were crossed with a permeable cultivated (G. max) variety JS335 to generate the mapping populations. Genetic analysis of the F 1:2 and F 2:3 seeds of the crosses indicated that SCI is controlled by a single gene/major QTL, and impermeability is dominant over permeability. Presence of seeds with intermediate permeability indicated role of some minor genes/QTLs. A set of 204 inter-specific recombinant inbred line (RILs) (F 7 ) was used to map SCI with 207 SSR markers. Phenotyping through rapid imbibition approach (seed imbibition for 6 h), seven QTLs were mapped on chromosomes (Chrs.) 2, 5, 12, 13 and 16 in the seeds stored for 1-3 years, while through slow imbibition method (seed imbibition for 7 days), five QTLs were mapped on Chrs. 2, 9, 10 and 20. Phenotypic variation explained (PVE) by the QTLs ranged from 5.96 to 39.67%. Two major and stable QTLs viz., qScI-h2-1 and qScI-h2-2 that mapped in tandem on Chr.2 jointly explained 43.09-62.92% of the variations in impermeability. Seven minor QTLs identified here were novel and two (qScI-h5, and qScI-h16) were consistent. It is the first report of mapping impermeability using two imbibition approaches together in 200 plus interspecific RILs in soybean. The study will pave the way for developing genotypes with restricted permeability, enhanced seed viability, and improved seeds quality.