Temperature affects the mesocotyl and coleoptile length of grain sorghum genotypes

Abstract

The effect of seven temperatures ranging from 15 to 45�C on the germination and seedling length (mesocotyl +coleoptile) of eight grain sorghum genotypes (QL10, QL27, B35, R9247, BTx2761, BKS4, RTx7078 and 1790E) was determined. There was significant variation in germination (25-100%) and seedling length (6-182 mm) across temperatures and among genotypes, and significant temperature X genotype interactions occurred. Emergence problems due to poor germination and inadequate seedling length are likely in certain genotypes at high (>30�C) and low (<20�C) seedbed temperatures, particularly when deep sowing is necessary to reach moist soil. The optimum temperature for coleoptile elongation was 15-20�C, while the optimum for mesocotyl elongation varied from 15-30�C. Generally, the coleoptile comprised only a small proportion of the total seedling length, but the proportion increased at high and low temperatures (range: 6-53% of seedling length). The mesocotyl lengths of five genotypes selected at ICRISAT for their long mesocotyls were not outstanding compared with a locally derived hybrid B35 X R9247, which had not been selected for long mesocotyls. It is recommended that commercial hybrids be screened for germination and seedling elongation at the temperatures that occur in the seedbed at sowing.