Abstract
A description is provided for Diaporthe phaseolorum. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Phaseolus, Phaseolus lunatus, Ipomoea, Glycine, Allium, Arachis, Capsicum, Hibiscus esculentus, Lupinus, Lespedeza, Strophostyles and Vigna. DISEASE: Stem canker, pod and stem blight of soyabean (Glycine max) and other legumes; dry rot of sweet potato (Ipomoea batatas); and pod blight of Lima bean (Phaseolus lunatus). The most serious diseases are those on soyabean. Infected seedlings may be weak and stunted. In older plants lesions form on the petiole and stem, where they may become girdling cankers (characteristically red-brown in Diaporthe phaseolorum var. caulivora in the early stages). Infected seed is discoloured and reduced in size. In the field perithecia predominate in var. caulivora and pycnidia likewise in var. sojae. On Lima bean leaf lesions are up to 3 cm diam. with concentrically arranged pycnidia. Shot-holing may occur and infection of young pods leads to destruction of the seed. In sweet potato, tubers shrink and become mummified in storage; dry rot and necrosis of sprouts occur in the plant bed; pycnidia form on tubers and sprouts. GEOGRAPHICAL DISTRIBUTION: Probably widespread in the form frequently referred to as var. sojae. Reported from: Brazil, Canada, China, Colombia, Cuba, Egypt, Guyana, India, Israel, Japan, Korea, Malawi, Nigeria, Sierra Leone, South Africa, Tanzania, USA; var. batatisis is probably more widespread than has been reported (New Zealand, USA, Zaire Republic); var. phaseolorum has been reported from Cuba, Bermuda, South Africa, Tanzania, USA. The severest form of the disease (var. caulivora) appears to be restricted to N. America (CMI Map 360, ed. 1, 1958). TRANSMISSION: Through seed, tubers, crop debris and probably soil (34: 425; 42: 352, 353, 425; 44, 2003). Viable in soyabean seed for 2 yr.