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Relationships among charcoal rot infection, yield, and stability estimates in soybean blends

Bowen, C.R., Schapaugh, W.T. Jr.
Crop science 1989 v.29 no.1 pp. 42-46
Glycine max, cultivars, lines, Macrophomina phaseolina, plant density, infection, cultural control, agronomic traits, disease resistance, crop yield, Kansas
Charcoal rot [Macrophomina phaseolina (Tassi) Goid] of soybean [Glycine max (L.) Merr.] commonly affects plants grown in the western midwest of the USA. No control measures have been reported. This study measured the effects of cultivar blends and rates of planting on charcoal rot infection and agronomic traits to determine if blends provide a greater protection against the disease and broader adaptation to environments. Six blends and four pure lines in maturity groups III and IV were tested in replicated plots across eight locations. Measurements taken on each plot included seed yield, height, lodging, plant population, and amount of charcoal rot infection. The relationship of these traits with stability estimates were considered. Reducing planting rate from 30 seeds m-1 (387 500 seeds ha-1) to 20 seeds m-1 (258 000 seeds ha-1) significantly lowered infection levels without reducing yield. Stage of reproductive growth was associated linearly with infection level. There was no significant genotype effect for infection when stage of reproductive growth was used as a covariate. Infection levels were correlated with response (bi), relative performance over environments. Response and biological estimates of stability were significantly correlated with one another. Deviations from response, r2, and ecovalance were also significantly correlated. The positive association of growth stage and infection suggests planting full-season cultivars as a method of reducing charcoal rot. There was no benefit in blending pure lines either in increased yield or decreased charcoal rot infection.