THE ORGANIZATION OF GROWTH-REGULATING GENES IN MAIZE .2. QUANTITATIVE TRAIT LOCI

We have presumed that in maize (Zea mays L.), the genes that control plant growth and development are associated in functionally significant clusters, 10 to 30 cM long, unevenly distributed along ten chromosomes. To test this model by independent evidence, we have compiled the currently published mapping data for quantitative trait loci (QTLs) related to maize plant architecture, growth pattern, growth rate, both in vitro and in vivo, and yield as the integer of growth, and for loci related to abscisic acid accumulation and effects. The majority of these QTLs were found to map within the already delineated 16 clusters. Several more clusters can be predicted that combine the mapping positions for single naked eye polymorphisms (NEPs) and for numerous molecular probes, co-segregating with various growth-related QTLs. At least two map segments comprising widely different growth QTLs and devoid of known NEPs for growth and development are of particular interest as additional prospective clusters. The most dense associations of genes and QTLs with wide arrays of growth manifestations are given particular attention as the presumable locations of key genes acting as master switches in development.