Yield and agronomic traits relations with plant color of sorghum hybrids

Sorghum plant color refers to the pigmentation in the place where plant tis sue is wounded. In sorghum the three main plant colors are: red, tan, and p urple. Tan plant character is critical for producing food grain quality sor ghum and it has been associated with foliar disease resistance. These effec ts have been determined by evaluating genotypes with different genetic back ground. In this study, five pairs of near-isolines (three pairs of maintain er and two pairs of restorer) for red (R) and tan (T) plant color were used to produce 24 sorghum hybrids (six RxR, six RxT, six TxR and six TxT). Tho se hybrids were grown during the spring seasons of 1989, 1991 and 1992 at 1 0 locations under dryland conditions and two locations under irrigation in Northern Tamaulipas, Mexico. A randomized complete block design with three replications was used for each experiment. Grain yield, days to flowering p lant height, panicle length, panicle exsertion and grain moisture were reco rded. A combined analysis of variance was performed and orthogonal contrast s were used to compare each group of hybrids. Results indicated that RxR hy brid group yielded significatively more then TxT hybrids in both dryland an d irrigated conditions. In dryland, hybrid groups with at least one patent carrying the red plant trait (RxR, RxT and TxR) yielded more than TxT hybri ds. Furthermore, yield differences between tan and red hybrids were signifi cantly higher under this condition. This suggested that TxT hybrids may be more susceptible to drought. TxR hybrids was the highest yielding group. Su periority of the TxR hybrids may be due to some heterotic effects associate d with this combination, which enhanced their performance under dryland con dition. Regarding to other characters, some significant differences among s orghum hybrids were detected but, they were not related to plant pigmentati on.