Root rot pathogens in field soil, roots and seeds in relation to common bean (Phaseolus vulgaris), disease and seed production

The interrelationships among bean productivity, prevalence of pathogens in roots, seeds and soil, and root rot disease were described at the pod maturity stage in 13 commercial fields. The soil population and frequency of pathogens isolated from seeds varied by pathogen species and field location. Fusarium solani was the most prevalent fungus isolated from bean seeds and field soil compared to Rhizoctonia solani, Macrophomina phaseolina and F. oxysporum. Principal component analysis revealed that the first component explaining 32% of the total variance was correlated with the root rot index. PC1 was more strongly linked to root and seed infections in comparison with soil populations of pathogens. Based on a correlation between PC2 (accounting for 23% of the total variance) and the number of seeds per bean plant, charcoal, Fusarium and Rhizoctonia root rots were recognized as more important determinants of seed losses to root rot disease. There were correlations among the major pathogens infecting either roots or seeds of beans. These findings provide useful information for future experimental plans to optimize management strategies for bean root rots.