Identification of Rhizobacteria That Increase Yield and Plant Tolerance To Angular Leaf Spot Disease in Cucumber

Abstract

The biological control of angular leaf spot disease (ALS) of cucumbers (Cucumis sativus), caused by Pseudomonas syringae pv. lachrymans (Psl), using promising rhizobacteria (RB) and to compare RB efficacy to that of acibenzolar-S-methyl (ASM) was investigated. Effects of ASM and RB isolate Pseudomonas putida AA11/1 that was isolated from the healthy cucumber root surface on disease severity and plant growth were evaluated using ALS-susceptible and tolerant cucumber cultivars in a growth chamber and a soilless growing system. ASM and AA11/1 significantly reduced average disease severity of ALS by 69 and 34% in the susceptible cultivar and 92 and 21% in the tolerant cultivar, respectively. ASM treatment significantly reduced Psl populations, but AA11/1 did not inhibit Psl growth in either cultivar. In the soilless system, disease severity was limited by either ASM or AA11/1, whereas only AA11/1 treatments significantly increased cucumber yield by 68 and 33% in the susceptible and tolerant cultivar, respectively.