AbstractDifferences in maturation time and daily grain yield were sought among cultivars and hybrids of sorghum (Sorghum bicolor (L.) Moench) grown in the tropics. Seven lines were used as males in crosses with three cytoplasmic-genetic male-sterile lines to produce 21 hybrids. Formation of the black layer (SL) was used as criterion for physiologic maturity. The male-parental lines and their hybrids were evaluated for grain yield/day from planting to midbfoom (GYMS), from planting to SL formation (GYSL), and from midbloom (MS) to SL formation (GYMS-SL), and for total grain yield at SL formation (GY). When results for the hybrids of each female line were averaged over the seven male-parental lines, hybrids of the female "Redlan' were first to reach MS and BL formation, and they produced the largest GYMS and GYSL. When results for the hybrids of each male-parental line were averaged over the three female lines, hybrids of the males 6, 9, and 10 were among the first to reach MS and SL formation, and were highest in GYMS, GYSL, GYMS-SL, and GY. For individual hybrids, differences in both maturation time and GY contributed to differences in daily grain yield, but the greater influence appeared to be that of GY. However, in five of the seven sets of hybrids having a given male parent (e.g ., A4, S4, and C4), the hybrid (with Redlan in each case) that was first to reach MS produced a GYMS equal to or higher than those of the hybrids that were slower to reach MS. Also in four of the seven sets of hybrids, the hybrid (with Redlan in three cases) that was first to reach SL formation had a GYSL higher than those of the later maturing hybrids. When the male-parental lines were selfed, lines 6, 9, and 10 produced the highest GY, GYMS, GYSL, and GYMS-SL. These lines were among the five earliest. In the tropics high yield/day and rapid maturation rate may be very desirable characteristics, and the current research identified hybrids with these characteristics. Redlan seems promising as a female parent for such desirable hybrids. Males 6, 9, and 10 seem promising as parent for GY, but they have some undesirable agronomic or quality characteristics.
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