Abstract:

Three species of Ascochyta infect peas: Ascochyta pisi Lib. causing leaf and pod spot; Ascochyta pinodes Jones, causing blight; Ascochyta pinodella Jones, causing foot rot. Ascochyta pisi, which has no known teliomorph, tissues (leaves, stems, flowers, pods and seeds), (teliomorph Mycosphaerella pinodes (Berk. & Blox.) Didymella pinodes (Berk. & Blox.) Petrak) attacks all aerial parts and also causes a foot rot. attacks only aerial Ascochyta pinodes Vestergr.; synon. Ascochyta pinodella (now usually referred to as Phoma medicaginis var pinodella (Jones) Boerema) causes a foot rot but is less conspicuous on aerial parts; like Ascochyta pisi no teliomorph is known (Dixon, 1981; Lawyer, 1984). Distinguishing between the three species in the field is not easy since the disease syndrome incited by M. pinodes embraces the symptoms induced by A pisi and P. medicaginis var pinodella (Dixon. 1981). In culture, however, they are more easily differentiated. P. medicaginis var pinodella. unlike the other two species, produces pycinidospores which are predominantly non- sepate; the bi-celled pycnidiospores of A pisi are slightly larger than those of A pinodes (14 x 4.2^m compared to 12.3 x 4.5 gm) and the spore masses (cirrhi) are carrot red rather than buff. Both M. pinodes and Phoma medicaginis var pinodella produce chlamydospores in the hyphae while A pisi does not. (Noble 1971). A pinodes produces perithecia (pseudothecia) readily in culture and provides a clear distinction from the other species (Lawyer. 1984).