Terminal drought-tolerant pearl millet [Pennisetum glaucum (L.) R. Br.] have high leaf ABA and limit transpiration at high vapour pressure deficit
Abstract
Pearl millet genotypes carrying a terminal drought tolerance QTL have a lower transpiration rate (Tr) under well-watered conditions than sensitive lines. Here experiments were carried out to test whether this relates to leaf ABA at high VPD, and whether that leads to transpiration efficiency differences.
Most genotypic differences were found under well-watered conditions. ABA levels under these conditions were higher in tolerant genotypes, including NIL-QTLs, and ABA did not increase under water stress.
Well-watered Tr was lower in tolerant genotypes at all VPD levels. It is concluded that two water-saving mechanisms may operate under well-watered conditions in tolerant pearl millet: a low Tr even at low VPD, which may relate to leaf ABA; and a sensitivity to higher VPD that further restricts Tr, suggesting the involvement of hydraulic signals.
Both traits could contribute to absolute water saving. This deserves consideration in the breeding of terminal drought-tolerant lines.