Onion Leaf Blight Caused by Xanthomonas campestris: Alternative Hosts and Resistant Onion Genotypes

Tomato (Lycopersicon esculentum), pepper (Capsicum annuum), corn (Zea mays), French bean (Phaseolus vulgaris), soybean (Glycine max), winged bean (Psophocarpus tetragonolobus), lima bean (Phaseolus lunatus), field pea (Pisum sativum), moth bean (Phaseolus aconitifolins), and heliconia (Heliconia bihai) were evaluated as alternative hosts of Xanthomonas campestris, the causal agent of a leaf blight of onion (Allium cepa). On legumes, bacterial growth occurred in planta, and visible disease symptoms developed. From 19 commercial onion genotypes screened for leaf blight resistance, two cultivars, H-942 and H-508, were generally free of symptoms and had restricted bacterial growth in planta. These are the first known reports on alternative hosts of the bacterium and on resistance in onion to leaf blight.