Xanthomonas phaseoli . [Descriptions of Fungi and Bacteria

Abstract

Abstract A description is provided for Xanthomonas phaseoli . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Phaseolus vulgaris and other species of Phaseolus and Lablab niger [Lablab purpureus] . DISEASE: Common blight. A disease affecting leaves, stems, seed and pods, mainly confined to the parenchyma but which may invade the vascular system and cause a wilt. Symptoms are very similar to halo blight and the two diseases often occur together. An association with common bean mosaic virus is also found. The leaf symptoms are enhanced synergistically in mixed infections (38: 437; 24: 47), but after serial passage the virus becomes dominant. GEOGRAPHICAL DISTRIBUTION: As with Pseudomonas phascolicola , the pathogen is probably found in most countries where beans are grown (CMI Map 441, 1965). TRANSMISSION: The pathogen is seed-borne and is harboured beneath the seed coat where it may remain viable for several years. Dissemination in the field is by wind-driven rain, insects, infected plant debris or wind blown soil (37: 128). The pathogen enters through the stomata or wounds Overhead sprinkler irrigation may be a means of spread, but not furrow irrigation (34: 339). Unlike the halo blight pathogen, X. phaseoli can overwinter on infected stems and leaves, and be perpetuated on hosts other than species of Phaseolus . Soaking bean seeds in suspensions of the root nodule bacterium for inoculation purposes may inadvertently result in a great increase in infection where the original incidence was slight.