Genetic integrity of rice seeds during ageing and gene bank storage by SSR analysis

Genetic alterations during ageing of rice seeds were analyzed using SSR markers. In the first experiment, seeds of 10 accessions of rice were subjected to artificial ageing in chambers conditioned to 55°C and 72±2%RH for 72 hours. In the second experiment, seeds of 4 accessions of rice stored in the NACGRAB gene bank, Nigeria in 2011 at 5± 4°C were compared with seeds of the same accessions freshly harvested in 2013. The objectives of this project were to evaluate ageing induced genetic changes and to establish physiological thresholds for loss of genetic integrity for rice seeds. Data were collected on seed germination and a seed vigour index was estimated. Genetic changes during the ageing course were evaluated by SSR markers using a Direct™ PCR kit. Genetic drifts and distances were estimated using PAST™ software and percentage genetic integrity was estimated from the genetic distance matrices. At 72 hours of ageing, seed germination percentage declined to 54.2% and vigour index 1.38 coinciding with the lowest estimate of genetic integrity (99.5%). Probability of genetic drift during ageing as revealed by primer RG178 was significant (P<0.005) for CG-14, IR-64 NERICA-1 and NERICA-L-34 and WITA-4. Differences in genetic distances were highest and estimate of genetic integrity was least in NERICA-1. Germination of seeds in gene bank after one and two years storage was above 99% and there were no significant genetic drifts for all accessions. The implications of result for gene bank activities will be discussed.