Varietal traits limiting the grain yield of tropical maize IV. Plant traits and productivity of tropical varieties

At Tlaltizapan, Mexico, 26 maize varieties with a wide range of various contrasting traits were grown at three plant densities (25, 000, 50, 000, and 100, 000 plants per ha) to clarify the factors currently limiting grain yield. The following results were obtained.

1. Long-duration varieties compared to short-duration varletles tended to be taller and to produce a larger number of leaves, larger LAl, larger TDW, and higher grain yield. No evidence was obtained to indicate that plant type was important for high-yielding varieties.

2. High grain yield was attributable mainly to the larger number of kernels per unit field area. The sink size is possibly the dominant factor controlllng the grain yield, indicating the importance of studies on the yield components.

For obtaining high-yielding varieties, it would be important to improve a strain so that a single ear became larger and more tolerant to barrenness at a high plant density.