Molecular evidence of genetic diversity changes in pea (Pisum sativum L.) germplasm after long-term maintenance

Maintaining germplasm genetic integrity is a key objective of long-term ex situ conservation. Periodic regeneration, performed on limited plots with small number of individuals, increases the risk of genetic drift and genetic diversity changes. In this study, six accessions of white flowered, dry seed pea varieties (Pisum sativum L. subsp. sativum var. sativum): BohatA1/2r, KlatovskA1/2 zelenA1/2, Hanak, MoravskA1/2 hrotovickA1/2 krajovA1/2, Raman and Viktoria-75 and four accessions of colour flowered, fodder pea (P. sativum subsp. sativum var. arvense (L.) Poiret: Arvika, eskA1/2 banan, Moravska krajova and Nik,, representing Czechoslovak varieties and landraces, bred over the last 40-80 years, were analyzed using ten microsatellite locus specific markers. Each accession was represented by 20 individual seeds of two temporally different samples, spanning the period of 20 or 40 years. Together with intra-accession variation (except of cv. Hanak), evidence of genetic changes, e.g. differences in allele frequencies as well as genetic composition of sample, was detected in six out of ten accessions (Arvika, BohatA1/2r, eskA1/2 banan, MoravskA1/2 hrotovickA1/2 krajovA1/2, Moravska krajova and Raman). Evidence of genetic erosion was found in three accessions (eskA1/2 banan, MoravskA1/2 hrotovickA1/2 krajovA1/2 and Raman), while in another three (Arvika, BohatA1/2r and Moravska krajova) the level of diversity was found to have increased. Moreover in three samples of BohatA1/2r (2004) and KlatovskA1/2 zelenA1/2 (1963 and 2004), low levels of heterozygosity was detected. These results demonstrate that in pea, a self-pollinating and highly homozygous plant, the danger of the loss of genetic integrity exists. These findings are significant for long-term ex situ germplasm management.