Morphological and virulence variation among isolates of Mycosphaerella pinodes the causal agent of pea leaf blight

Mycosphaerella blight caused by Mycosphaerella pinodes (Berk. and Blox.) Vestergr. is an important disease, causing severe damage in peas. Variability of 20 Algerian isolates of M. pinodes representative of four agro climatic regions were investigated on the basis of cultural, morphological and pathogenicity. Culture and morphology showed variations in colony color, radial growth pattern and production of pycnidia and pycnidiospores. Significant differences (P < 0.05) in both pycnidia and pycnidiospores size among isolates were observed. Hence, the size of pycnidia and pycnidiospores of M. pinodes varied from 145 * 143 µm to 280 * 265 µm and from 11.5 * 2.3 µm to 22.5 * 6.3 µm respectively. Using the factor analysis, this revealed that the first principal component (pc) was more related to the growth and sporulation aspect, hence, the colony growth and both the pycnidia and pycnidiospore density were more related to the first pc, while the second pc contributed for the pycnidiospores size.