Heritability of Nitrate Reductase and Cyanide Levels in Seedlings of Grain Sorghum Cultivars¹

Abstract

Abstract Seedlings of 41 cultivars of grain sorghum [ Sorghum bicolor (L.) Moench] including 30 hybrids and all but two of their parents were grown in a growth chamber; harvested 10, 14, and 18 days after planting; and assayed for hydrolizable cyanide and in vitro and in vivo nitrate reductase activity (NRA). The genotype X age variance component was essentially equal to the genetic variance for each character, which suggest that genotype X environment interactions are major components of the phenotypic variance. Cyanide level was highest in 10‐day‐old plants and dropped sharply in 14‐day‐old plants. Broadsense heritability of hydrolizable cyanide was high (0.89 to 0.95) for all three ages of plants. Narrow‐sense heritability indicated the cyanide content of 10‐day‐old plants could be changed 0.76 units for each unit change in the midparental value, but expected progress decreased markedly for 18‐day‐old plants. Broad‐sense heritability of in vitro NRA was high at all ages, and narrow‐sense heritability was moderate to low. Thus, significant genetic advance could be expected from selection among pure lines and hybrids, but nonadditive genetic variance would reduce progress in hybrids based on selection of their parents to a moderate level. In vivo NRA was only 20% of in vitro activity. Heritabilities, in general, also were lower for in vivo than for in vitro NRA.