Evaluation of genetic integrity of tomato seeds during ageing by microsatellite markers

The objective of this project was to evaluate ageing-induced genetic changes during storage of tomato seeds. Seeds of 10 accessions of tomatoes were thus subjected to artificial ageing in chambers conditioned to 55 °C and 72 ± 2% RH for 72 h. Seed survival data were used to estimate probit parameters. Genetic changes during the seed ageing course were evaluated by microsatellite (SSR) analysis using a Direct PCR™ kit., The SSR primer sequences (except SGN-14430) optimized the gene markers for the tomato accessions and are thus recommended for detecting genetic changes during seed storage. Genetic distances were calculated using PAST™ software and percentage genetic integrity was estimated from the genetic distance matrices. Probit analysis showed that P₅₀ estimates was least in accession LOO169 (7 days) and highest in accession 09/044 (64.4 days). Seeds having lower P₅₀ estimates showed lower estimates of genetic integrity. Lowest estimate of average genetic integrity was 99.21% when estimates of genetic distances were compared between 0 and 72 h of artificial ageing. The results showed ageing-induced genetic deterioration during artificial ageing thus suggests possibility of losses in genetic integrity of seeds in storage at a specific physiological (germinability) benchmark. For tomatoes, this study shows that seed germinability benchmark for genetic changes during ageing was approximately 42%. Comparison of tomato seeds stored in the NACGRAB gene bank for 2 years and freshly harvested seeds, validated the artificial seed ageing result and the estimated germination benchmark for declining genetic integrity in tomato seeds.