Inter- and Intra-row Inter-genotypic Competition Influences Selection for Avoidance of White Mold Disease in Dry Edible Beans

Abstract

Abstract Two field experiments were conducted to explore possible causes of inefficient selection for architectural avoidance of white mold disease reported in dry beans (Phaseolus vulgaris L.). Near-isogenic breeding lines for maturity and plant growth habit were blended in 4 paired combinations (with 5 mixture levels/blend) to investigate their intrarow competitive influence on disease severity. Results from regressing the disease severity for each blend component on the mixture level showed the disease severity of an individual plant to be dependent upon its own maturity, as well as on the maturity of its neighbors. An increase in the proportion of late plants in the blend led to a significant and linear increase in their disease severity. A comparable decrease in disease severity was observed as the proportion of early plants in the blend was increased. Disease severity was not influenced by the proportion of indeterminate or determinate plants in the blend, regardless of maturity. The determinate growth habit, however, as well as early maturity, resulted in greater disease avoidance than the indeterminate growth habit or late maturity when grown in pure stands. In a 2nd experiment, 4 dry bean cultivars possessing different architectures were used to study the interrow influence of plant architecture on disease severity, incidence, and seed yield. Significant differences in disease severity and incidence observed between plots bordered by an upright genotype or a dense, prostrate genotype indicated that the level of disease in the test row was determined to a large extent by the architecture of adjacent rows. The failure to obtain an accurate assessment of a genotype's performance may account partially for the difficulty in selecting for architectural avoidance.