ASSESSING CHANGES IN THE GENETIC DIVERSITY OF POTATO GENE BANKS .1. EFFECTS OF SEED INCREASE

Effects of gene bank seed-increases on the genetic integrity of potato germ plasm is a major concern of gene bank managers. Thus the Associa tion of Potato Inter-gene-bank Collaborators (APIC), a consortium of w orld potato gene bank leaders, initiated this joint research project u sing RAPD markers to determine genetic relationships between increased generations within accessions. Solanum jamesii (2n = 2x = 24) and S. fendleri (2n = 4x = 48), two wild potato species native to North Ameri ca, were used as plant material. These species represented two major b reeding systems found among Solanum species: outcrossing diploids and inbreeding disomic tetraploids, respectively. Comparisons were made be tween populations one generation apart and between sister populations generated from a common source. Fourteen such comparisons within S. ja mesii accessions had an average similarity of 96.3%, and 21 such compa risons within S. fendleri accessions had an average similarity of 96.0 %. No pairs of populations were significantly different, despite the f act that RAPD markers easily separated all of these very similar acces sions within their respective species. Only one of six S. jamesii acce ssions analyzed showed a significant change in gene frequencies among generations. These findings indicate that there has been minimal loss or change of genetic diversity in ex situ germplasm using the gene ban k techniques standard at NRSP-6 and other world potato gene banks.