Analysis of the genetic integrity of rice ( Oryza sativa L.) and bean ( Phaseolus vulgaris L.) accessions stored in gene banks

The conservation of seed germplasm is one of the most important ways to maintain the genetic variability of genetic resources, such as rice ( Oryza sativa L.) and bean ( Phaseolus vulgaris L.). These two species are fundamental for the food security and agribusiness of many countries, including Brazil. The efficient use of germplasm depends on the maintenance of the germination potential and the genetic integrity of conserved accessions. The objective of the present study was to analyze the genetic integrity of rice and bean accessions that have been maintained in long term conservation conditions. Six and four samples of two rice and bean accessions, respectively, were analyzed. Each sample was added to the collection in different years. First count, germination and germination speed index tests were carried out to evaluate the physiological quality of the seeds samples. Cytogenetic tests and comet assay were performed to evaluate the genetic integrity of the different samples. Significant differences were not observed among the samples of the two species in the cytogenetic tests. Eight of the 10 samples analyzed maintained high physiological quality after prolonged storage and presented acceptable levels of DNA damage (> 20%) in the comet assay. Evidences of DNA repair were detected in one sample. Data showed comet assay has potential to evaluate genetic integrity and DNA repair system in long term conserved seeds.