Recurrent Selection for Reduced Plant Height in Lowland Tropical Maize

Reduced plant height is considered a desirable attribute in most maize (Zea mays L.) breeding programs. This study was conducted to evaluate direct and correlated responses to selection for reduced plant height in tropical maize. Fifteen cycles of visual, full-sib recurrent selection for reduced plant height were conducted in one lowland tropical maize population, ‘Tuxpeño Crema I’. Cycles 0, 6, 9,12, and 15 were evaluated for correlated responses in plant morphology, grain yield, dry matter production and distribution, leaf area index, and duration and rate of kernel growth at three plant densities at two or three locations in Mexico over a period of 2 yrs. Selection resulted in a linear reduction in plant height, from 282 to 179 cm (2.4% per cycle). The estimate of broad-sense heritability for plant height was 0.84. Optimum plant density for yield increased from 48 000 to 64 000 plants ha⁻¹, an increase of 2.1% per cycle. As height was reduced, yield, when determined at the optimum plant density for yield for each generation, increased by 4.4% per cycle. Later cycles showed reduced total lodging, reduced barrenness, earlier flowering, and fewer leaves per plant. When grown at or near their optimum densities for grain yield, leaf area index, and total dry matter per unit area at harvest for selected cycles were similar. Yield improvement was associated with a linear increase in harvest index from 0.30 to 0.45 from the original to the 15th cycle. At 50% silking, total aboveground dry weight and its proportion as stem were reduced; kernel number per unit area at harvest increased from 1592 to 2667 kernels m ⁻² when grown at or near optimum density, and there was an increase in crop dry weight production from anthesis to black layer formation. Selection for reduced plant height had little effect on the effective filling period or kernel weight.