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Path Coefficient Analysis of Effects of Rhizoctonia solani on Growth and Development of Dry Beans. Ariena H. C. van Bruggen, Former graduate research assistant, Department of Plant Pathology, Cornell University, Ithaca, NY 14853, Present address: Department of Plant Pathology, University of California, Davis 95616; P. A. Arneson, associate professor, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. Phytopathology 76:874-878. Accepted for publication 22 January 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-874.

A path coefficient analysis is presented for the data of two field experiments in which the effects of eight inoculum levels of Rhizoctonia solani on growth, development, and yield of dry beans were assessed. The analysis indicated that all three measures of disease (number of plants infected, number of lesions, and lesion area) were equally important in reducing and delaying emergence in the first year, whereas only number of plants infected determined these effects in the second year. Of the yield components, pods per plant exerted the largest influence on yield per unit area. Plants per row was the second most important yield component, but its correlation with yield was not significant or only weakly so, because of a negative correlation between plants per row and pods per plant. The most important path of influence of infection on yield was via numbers of plants infected, numbers of plants established (at flowering) and final numbers of plants per row (at harvest) in both years, and via numbers of lesions, shoot dry weight (at flowering), and number of pods per plant in the first year. Of the yield components only the number of plants per row was significantly reduced by inoculum level, but because of compensation by the other yield components, R. solani did not affect overall yield.

Additional keywords: correlation coefficients, Phaseolus vulgaris, yield components.