IDENTIFICATION OF GENOMIC REGIONS AFFECTING PLANT HEIGHT IN SORGHUM AND MAIZE

The objective of this study was to use restriction fragment length pol ymorphisms (RFLPs) to determine the genetic location and effects of ge nomic regions controlling plant height in sorghum. F-2 plants (152) fr om the cross CK60 x PI229828 were used. Genomic and cDNA clones (106) identified 111 loci distributed among ten linkage groups covering 1299 cM. Interval mapping identified four regions, each in a separate link age group. These regions may correspond to loci (dw) previously identi fied by alleles with qualitative effects. Also, these regions identifi ed in sorghum may be orthologous to those previously reported for plan t height in maize. Gene effects and gene action varied among genomic r egions. In each region, PI229828 alleles resulted in increased plant h eight. Each region accounted for 9.2-28.7% of the phenotypic variation . Positive, additive effects ranged from 15 to 32 cm. Tallness was dom inant or overdominant and conferred by alleles from PI229828 for three quantitative trait loci (QTL). At the fourth QTL, PI229828 contribute d to increased plant height, but short stature was partially dominant. One digenic interaction was significant. The presence of a PI229828 a llele at one region diminished the effects of the other region. A mult iple model indicated that these four regions collectively accounted fo r 63.4% of the total phenotypic variation. The utility of this informa tion for germplasm conversion through backcross breeding is discussed.