Analysis of diversity in populations of Helminthosporium sativum Pammel, King and Bakke, the causal pathogen of leaf spot of wheat.
1992
Pascual C.B.
Significant differences among the 47 isolates of Helminthosporium sativum were observed in all the parameters considered (lesion length, lesion number, incubation period, spore size, number of septa, colony size, toxin production, and protein banding pattern). Isolates differed also in growth characteristics and showed four types of growth. I Sub 40 which was collected from MMSU [Mariano Marcos State University], Dingras, Ilocos Norte [Philippines], consistently exhibited the biggest spore size, the highest number of septation, the longest lesion, shortest incubation period and strikingly produced the biggest lesion when inoculated with the toxin extracted from this fungus. Based on lesion length, I Sub 40 was considered the most virulent isolate. I Sub 18 which was collected from Batac, Ilocos Norte and showed a unique characteristic growth, produced the smallest spore size, least virulent isolate. Among the six wheat cultivars inoculated with 20 isolate using detached leaf method, C512 showed some degree of resistance to most of the isolates. Principal components analysis showed that the first component, which accounted for almost half of the total variance, was dominated by number of septa, spore size, lesion length, and toxin production. Average linkage cluster analysis, using these four parameters, revealed three main clusters of isolates. Significant correlation coefficients, involving several parameters, were observed.
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