RELATIVE SUSCEPTIBILITY OF PEACH AND PLUM GERMPLASM TO ARMILLARIA ROOT-ROT

Nearly 5000 seedling trees representing more than 100 peach [Prunus pe rsica (L.) Batsch,] and plum (Prunus spp.) lines were planted at a 4 x 0.6-m spacing in Jan. 1983, on a site with a known history of peach t ree short life (PTSL) and Armillaria root rot (ARR). Trees were arrang ed in a randomized complete-block with eight replicates of six trees e ach, Beginning in Spring 1984 and each year thereafter the cause of tr ee death was determined. At the end of 9 years, 50 % of the trees had succumbed to PTSL and 35 % had been killed by ARR apparently caused by Armillaria tabescens. Analysis of the data for trees killed by ARR sh owed a wide range in mortality, some peach lines appeared significantl y more tolerant to ARR than others. Plum lines derived from native Nor th American species also appeared to be a potential source of improved tolerance. We did not establish whether ARR tolerance is affected by PTSL.