Genetic correlation between corn performance in organic and conventional production systems

Cultivars bred under conventional production systems may not be optimum for organic production systems. Our objective was to determine if, on the basis of quantitative genetic parameters, separate corn (Zea mays L.) breeding programs are needed for organic and conventional production systems. Testcrosses of 119 intermated 873 x Mo17 recombinant inbreds were evaluated in organic and conventional systems in both Waseca and Lamberton, MN, in 2006. Differences in trait means between the two production systems were significant for grain moisture, plant height, and ear height but not significant for grain yield, root lodging, stalk lodging, and stay green. The organic system led to a smaller testcross genetic variance for grain yield and higher testcross genetic variances for all other traits. The organic system led to a lower heritability for grain yield and a higher heritability for root lodging, stay green, and ear height. Genetic correlations for performance in the two production systems were 0.84 for grain yield; greater than 0.90 for grain moisture, plant height, and ear height; and about 0.50 for root lodging and stay green. The predicted ratio between the correlated response and direct response to selection in the organic system was near 1.0 for grain yield and moisture and considerably less than 1.0 for other traits. These results suggest that high-yielding cultivars for organic systems can be developed largely by screening conventional inbreds and hybrids for their performance under organic systems.