Varietal traits limiting the grain yield of tropical maize II. The growth and yield of tall and short varieties

Four isogenic varieties with different heights, derived from the Tuxpeño population, were grown in the tropics to evaluate their potential productivity. Short varieties were developed by two means: incorporation of the brachytic-2 gene and current selections of shorter plants.

The tallest, original Tuxpeño produced the highest yield, next was the short-plant selection, while the brachytic varieties yielded least. Yield differences between the original and the short-plant selections were derived from the kernel size and the differences between those and the brachytic varieties, from the number of kernels.

Incorporation of the brachytic gene is unlikely to improve the productivity of varieties because it results in low efficiency of leaves in dry matter production during ripening, caused by the limited sink size and the compact distribution of wide leaves.