Masters Dissertations

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Browsing Masters Dissertations by Subject "Bean Anthracnose"

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    Studies on Bean Anthrracnose in the Southern Highlands of Tanzania
    (University of Dar es Salam., 1980) Shayo, Frederica Mlebio
    Anthracnose, incited by Colletotrichum lindemuthianum, is an important disease of Phaseolus beans in Tanzania. A study was carried out to determine the pathogenicity and virulence of five isolates of the pathogen on twenty bean lines and the reactions of the lines to the isolates. The isolates were obtained from infected bean pods and leaves which were collected from several bean growing areas in the Southern Highlands of Tanzania and differentiated on the basis of cultural characteristics. Field and greenhouse experiments were conducted at Uyole, Mbeya during the 1979/80 growing season. A split-plot design with four replications was used for both experiments with the isolates in main plots and the bean lines in the sub-plots. The field experiment was laid out on a loamy to clay loam soil. The results of the field and greenhouse tests showed that all isolates were pathogenic, and showed highly significant differences in virulence on the tested bean lines. Two of the isolates, U2 and U3 were significantly more virulent than others. Five of the bean lines, UAC 57, UAC 79, P-304, P-618 and P-774 were found to be resistant to anthracnose. Lines UAC 41, EA1 2989, EA1 4110, P-2, P-360 and P-504 moderately resistant and one line, P-260, was immune to the disease. The rest of the bean lines were susceptible. Another field experiment was conducted to determine the effect of anthrocnose on bean yield. Three bean cultivars with varying reactions to anthracnose were planted in a split-plot experiment with the cultivars in main plots and disease in the sub-plots in four replications. Differences in disease in each cultivar were generated by spraying one of the sub-plots with benomyl while the other sub-plot was left unsprayed. Highly significant differences in the severity of anthracnose were found between the sprayed and unsprayed plots of the highly and moderately susceptible bean cultivars. The differences in disease severity between the sprayed and unsprayed plots were not significant differences in yield between the sprayed and unsprayed plots in the highly and moderately susceptible bean cultivars. The greatest yield reduction of 86% was recorded in the highly susceptible cultivar, T8 followed by a reduction of 27% in the moderately susceptible cultivar, Mexican 142, and 4% in the cultivar T3, which was highly resistant. The yield reduction in T3, which was highly resistant. The yield reduction I T3 was not statistically significant. It was estimated that bean anthracnose was causing a monetary loss of about 84.3 million Tanzanian shillings, approximately equivalent to 10 million U.S. dollars per season in the Southern Highlands, based on the estimated area under beans and the current local market price for dry beans of T.Shs. 3.50 per kilograms.