INHERITANCE OF TOLERANCE TO SOIL ACIDITY IN TROPICAL MAIZE

Soil acidity reduces maize (Zea mays L.) yields on approximate to 8 mi llion hectares of tropical soils. Maize cultivars with tolerance to so il acidity can alleviate this problem in developing countries. We used a North Carolina Design I mating system to study the inheritance of t olerance to soil acidity in a tropical maize population, SA-3, in orde r to efficiently develop maize cultivars tolerant to acidic soils. We studied 256 full-sib progenies, involving 64 males and four females wi thin each male, that were grouped in eight sets and field planted usin g two replications under one normal and three acidic soil environments during 1990-1991 in Colombia. Across acidic soils, additive genetic v ariance (V-A) was similar to dominance variance (V-D) for grain yield (0.15 vs. 0.13) greater than V-D for plant height (47.97 vs. 6.83) and ears per plant (0.01 vs. 0.00), and less than V-D for days to silk (1 .26 vs. 2.98). Heritability, estimated using half-sib family means, av eraged 36.3 +/- 19.9% for yield, 30.9 +/- 19.8% for days to silk, 51.5 +/- 19.3% for plant height, and 40.5 +/- 19.8% for ears per plant. Ad ditive x environment interaction was the more important component of g enetic variance for all traits studied. Although grain yield showed a positive additive genetic correlation (r(A) = 0.84*) with ears per pl ant, direct selection for yield was more effective for improving yield under acidic soils. The magnitudes of additive and additive x environ mental variances and of r(A)s among the environments suggest that recu rrent selection, based on multilocation testing, would be effective in improving grain yield, days to silk, plant height, and ears per plant under acidic soils.