Breeding and evaluation of sorghum bicolor (L.) moench hybrids for adaptation using base metabolic temperature (BMT) as a selection tool

Abstract

Performance and adaptation measurements were obtained for 88 F(,1) sorghum hybrids which were produced by selection from the cross (RT x 7000 x 77CS2), 22 low and 22 high base metabolic temperature (BMT) males and then crossing to 2 female cultivars, one low and one high BMT. Replicated trials were grown near Halfway, Texas (1980), College Station, Texas (1981) and Tampico, Mexico (1980). Mean yields of 5537, 5968 and 7251 kg/ha were obtained at Halfway, College Station and Tampico. Temperature and growing degree days (GDD) from planting to pre-anthesis appeared to affect rate of growth, days to anthesis and hence the length of the growing season. Grain yield of the low x low (L x L) and low x high (L x H) BMT hybrids increased in more tropical locations. The lowest BMT combination (L x L) resulted in the highest mean yield in Tampico, the most tropical location. BMT was negatively associated with grain yield.Hybrid combinations L x L and L x H produced greater numbers of seed per panicle, were 5 to 6 cm taller and had longer panicles, superior leafiness ratings, better plant desirability ratings, and greater panicle weights than H x H and H x L combinations at all locations. H x H and H x L hybrids had greater 1000 seed weights and superior test weights. The H x H and H x L combinations required 3 to 4 more days to reach 50% anthesis at Halfway than L x L or L x H combinations. Plantings at College Station and Tampico gave opposite results than obtained at Halfway. In general, H x H and H x L hybrids flowered earliest in lower latitude while L x L and L x H were latest. In addition, H x H and H x L hybrids had higher threshing percentages at Halfway while at Tampico the L x L and L x H hybrids were highest. Plant height, plant desirability rating, panicle weight, 1000 seed weight and number of seeds per panicle were highly correlated and should be considered by the plant breeder in developing high yielding sorghums. The following characteristics were correlated with BMT: plant height, plant desirability rating, panicle length and panicle weight. The regression of BMT versus grain yield showed a negative association indicating low BMT genotypes produced highest yields. This association may be an additional tool in early testing procedures to predict high yielding combinations. BMT of male parents was positively transmitted to F(,1) hybrids.