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Procedures for Field and Greenhouse Screening of Prunus Genotypes for Resistance and Tolerance to Root Lesion Nematode


Procedures were developed for screening Prunus spp. and related genotypes for resistance/tolerance to the root lesion nematode Pratylenchus vulnus Allen and Jansen in the field and greenhouse. Inoculum rates tested were 150 and 1500 nematodes per 375-cm3 pot in the greenhouse and 300 and 3000 nematodes per planting site in the field. Nematodes per gram of root was a reliable indication of the relative resistance of a genotype to initial invasion and establishment of P. vulnus at 122 days after treatment (DAT). At 122 DAT, more distinct differences between genotypes were seen at the low inoculum rate than at the high rate. The most sensitive growth measurement in the field appeared to be the relative diameter increase at 175 DAT. Significant reductions in Ca++ and Mg++ in new rootlets were also a reliable indication of nematode effects on a genotype in both the field and the greenhouse. Using these criteria, Pistacia atlantica Desf. was classified as resistant, ‘Nemaguard’ peach [Prunus persica (L.) Batsch] as susceptible, and P. besseyi Bailey, ‘Royal’ apricot (P. armeniaca L.), and ‘Myrobalan 29C’ plum (P. cerasifera Ehrh) as tolerant in decreasing order of tolerance.