INHERITANCE OF KERNEL WEIGHT IN 2 MAIZE-TEOSINTE HYBRID POPULATIONS - IMPLICATIONS FOR CROP EVOLUTION

A QTL-mapping strategy was employed to determine the number of quantitative trait loci (QTLs) that control the difference in kernel weight between maize (Zea mays L. ssp. mays) and its probable progenitor, teosinte [Z. mays ssp. parviglumis Iltis and Doebley, or ssp. mexicana (Schrader) Iltis]. Two maize-teosinte F-2 populations were analyzed. In the first population, we detected six QTLs, each controlling 4%-34% of the phenotypic variance and, in the second, four QTLs, each controlling 9%-31% of the phenotypic variance. The QTL of largest effect, which maps to chromosome 3 in both populations, adds more than 30 mg to the average kernel weight, nearly doubling the weight of a teosinte kernel. This QTL may represent a major step in the early evolution of maize. The relatively small number of QTLs detected and the large magnitude of some of their effects suggest that the difference in kernel weight between maize and teosinte is more aptly described as oligogenic rather than polygenic. The inferred role of genes of large effect in the evolution of kernel weight in maize implies that there may have been evolutionary periods during which the fixation of these genes brought about relatively rapid change in a reasonably short period of time.