Dissertation Topic:
Genetic Studies In Soybean (Glycine max (L) Merill ) Varieties Based On Response To Some Storage Stress Factors
Name: OKUNLOLA, Gbemisola Oluseun [View Profile]
Matric Number: PG/14/0785
Programme: Crop Improvement and Seed Enterprise Development
Degree Awarded: M.AgSE
Date of Defence: July 15, 2017
ABSTRACT
Soybean (Glycine max (L) Merill is one of the most important legume in the world, providing protein and oils for both food and feed industries. It’s production is constrained by the seed’s poor resistance to storage stress especially relative humidity and temperature. Seeds of fifteen soybean varieties were subjected to accelerated ageing and molecular analysis to assess their storage stress resistance ability, categorise them based on their storage tolerance using Simple Sequence Repeat (SSR) primers. Preliminary assessment of the seed germination and seedling vigour characters of the varieties was conducted in the seed testing laboratory using International Seed Testing Association (ISTA) approach after which the seeds were subjected to accelerated ageing (AA) for 6, 12, and 24 hours at the temperature of 42°C and 100% relative humidity. Another set of seed samples of same varieties were stored for 6 months under ambient environment of average relative humidity (RH) of 65±5% and temperature of 25±2°C and aged seeds were assessed to determine loss in the seed germination and seedling vigour parameters. Nineteen SSR primers were also used to evaluate the soybean varieties in order to determine there suitability for detection of gene associated with storage stress resistance. DNA was extracted from the soybean varieties and Polymerase Chain Reaction (PCR) was carried out using 47oC and 56oC anealing temperature. The amplified products were separated on 6.0% polyacrylamide gel. Data collected on seed germination and seedling vigour traits from AA and six months ambient storage were subjected to Analysis of Variance (ANOVA), means were separated at 5% probability level using Duncan Multiple Range Test (DMRT) and principal component analysis (PCA) was conducted to determine the variation pattern in the varieties. The PCR amplicons were analysed using PowerMarker v3.0 software. ANOVA revealed significant differences in the reaction of the soybean varieties to AA test and six months storage. There were also significant differences in the reaction of the soybean varieties to different ageing periods. The PCA showed that germination rate index (GRI) and germination index (GI) were the major indices responsible for the significant variation in the seedling vigour characters measured. Polymorphism detected by the 19 SSR markers was 94.74% and the polymorphic markers produced seventy-two alleles, fifty-nine were polymorphic while nineteen were monomorphic. Both AA and SSR analysis grouped the fifteen varieties based on their storage stress tolerance level into two major clusters with four and five sub-clusters respectively. Genetic similarity coefficients categorized the varieties into highly tolerant, moderately tolerant and susceptible varieties.Varieties TGX1835-10E and TGX1448-2E were distinguished as varieties with good storage ability and therefore recommended for storage improvement in soybean breeding programme. SSR markers Satt565, Satt175, Satt281, Satt600, Satt160 and Satt281 produced specific allelic bands associated with soybean storability, making them candidate markers for linkage with soybean stress tolerance