Influence of Brown Stem Rot on Agronomic Performance of Soybeans
1966
Weber, C. R. | Dunleavy, J. M. | Fehr, W. R.
AbstactThe performance of six soybean varieties was evaluated on brown stem rot (Cephalosporium gregatum) infested and noninfested soils for 3 years at Ames and 2 years at Cresco, Iowa. Three varieties, corresponding to early, midseason, and late maturity, were used at each location. The use of corn yields as an index of soil productivity level appeared to be a useful technique for measuring effects of the disease where infested and noninfested areas were near, but not adjacent to one another. Soybeans grown on infested soils at the two locations averaged 1 inch taller, 2 days earlier in maturity, 8% less susceptible to lodging, 0.1 gram per 100 seeds smaller in seed size, 10.4% lower in seed number, and 2.0 cwt per acre (11.0%) lower in yield than soybeans grown on noninfested soil. Largest seed yield reduction from brown stem rot occurred in later maturing varieties and may be the result of the length of time plants are diseased and of increased disease severity. About 94% of the yield loss was from seed number reduction, with 6% attributable to seed size reduction. Since there is no appreciable resistance to brown stem rot, evaluation of soybean varieties should be conducted on noninfested soil to permit maximum expression of their genetic potential.
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