Rickettsia-like Bacteria in Peach Roots Preceded Development of Visual Symptoms of Phony Peach Disease and Changes in Leaf Elemental Concentrations1,2

Abstract

Abstract Rickettsia-like bacteria (RLB) are the presumptive cause of phony peach disease and are most numerous in peach (Prunus persica (L.) Batsch) roots. Of apparently healthy peach trees in a heavily infected orchard, 54% had RLB in root samples evaluated by 400 × phase contrast microscopy. Removing all peach trees with visible symptoms of phony peach disease would minimize the number of trees in the orchard infected with RLB. Of trees visibly infected with phony peach disease, 8% had root samples free of RLB on both sampling dates. Leaf concentrations of Mg and B varied significantly (P < 0.7%) with RLB levels in peach roots on 3 of 4 sampling dates. No element tested (P = 5%) separated roots free of RLB on two sampling dates from roots averaging 1 to 9 RLB per microscope field on one date and free of RLB on another date. RLB in peach roots preceded development of visible symptoms of phony peach and changes in leaf elemental concentrations. Soil analysis did not identify RLB infected tree roots (P = 5%).