Bacterial antagonists and their cell-free cultures efficiently suppress canker disease in citrus lime

Abstract

Proliferation of citrus canker disease caused by Xanthomonas citri subsp. citri (Xcc) has increasingly become a serious threat and has resulted in a significant loss in citrus production worldwide. This research aimed to identify efficient antagonistic bacteria for the biological control of canker disease in Citrus aurantifolia cultivar Pan (Pan-lime) and their antagonistic characteristics by experimental analysis. With the dual culture method, twenty isolates inhibited Xcc. Eight out of over fifty isolates showed clear inhibition zones and were further analyzed for plant growth-promoting characteristics. After the screening process, Bacillus velezensis isolate SWUA08 and Pseudomonas aeruginosa isolate SWUC02 were selected for further analysis of bacterial canker resistance in Pan-lime seedlings and trees. Experimental results show that both antagonists increased canker disease resistance. Furthermore, their cell-free cultures reduced canker disease severity index in Pan-lime tree. Our experimental results demonstrating that the antagonists offer an alternative perspective to evaluate a method of canker disease inhibition.