Emergence Comparisons Between Opaque and Normal Segregates in Two Maize Synthetics1

Abstract

Maize (Zea mays L.) inbred lines and populations with the opaque‐2 gene has several serious agronomic liabilities compared with normal maize counterparts among which are reduced yield, increased ear rot, reduced and slower seedling emergence, and reduced seedling vigor. The objectives of our study were to (1) compare emergence percentages in opaque‐2 and normal segregates from two synthetic populations; (2) determine whether emergence traits were correlated with protein traits; (3) estimate the genetic variances and heritabilities of emergence traits in the two synthetics. In Experiment I, kernels from 118 S1 segregating ears of BSAA+/o2 were germinated in sandbenches in a greenhouse; 93.5% of the normal kernels emerged compared with 82.0% of the opaque kernels. Mean squares for families, endosperm types, and the interaction of families X endosperm type were highly significant for percentage seedling emergence. Emergence percentage was negatively correlated (significant at the 0.01 level of probability) with lysine and protein concentration, and lysine (g/100 g protein). Genetic variances and heritability estimates for seedling emergence were higher in the opaque‐2 class than in the normal. In Experiment II, opaque and normal kernels from 80 segregating 1 ears of BSBB+/o2 were germinated and grown in flats in a growth chamber maintained at 12°C for 13 days and were then transferred to a greenhouse; 88% of the normal and 60.7% of the opaque kernels emerged. The average rate of emergence for normal kernels was slightly faster than for opaque kernels. Mean dry weight of seedlings was higher for normal kernels than for opaque. Genetic variances and heritabilities for these traits usually were larger in the opaque class. The correlations between seedling emergence and protein quality traits were frequently negative or close to zero. We concluded that it should be possible to select for improved seedling emergence in normal and opaque‐2 maize.