A RAPID PROTOCOL FOR EVALUATING PRUNUS GERMPLASM FOR TOMATO RINGSPOT VIRUS-RESISTANCE

Rooted cuttings of 'Halford' and 'Redhaven' peaches [Prunus persica (L .) Batsch] and 'Stanley' (Prunus domestica L.) and 'Marianna 2624' (P. cerasifera x P. munsoniana) plums were planted in soil containing alm ost-equal-to 38 tomato ringspot virus- (TomRSV) infested nematodes (Xi phinema americanum sensu lato Cobb) per 100 cc. Test- and control-plan t sap extracts were made from root and leaf tissues after 10, 22, and 34 weeks. Aliquots of these samples were assayed by mechanical inocula tion to Chenopodium quinoa Willd. Total nucleic-acid extracts prepared from the remainder of each sample were analyzed by dot biot hybridiza tion using a cRNA probe for TomRSV. The bioassay identified one 'Stanl ey' and two 'Redhaven' infected plants. Hybridization results indicate d that two of two 'Stanley', three of three 'Halford', five of five 'R edhaven', and zero of six 'Marianna 2624' were infected. Our results d emonstrate the sensitivity of molecular hybridization for TomRSV detec tion in Prunus and substantiate the TomRSV resistance of 'Marianna 262 4'.