Physiological approach to decipher the drought tolerance of a soybean genotype from Brazilian savana

• Published in: Plant physiology and biochemistry 2020-06, Vol.151, p.132-143
• Main Authors: Mesquita, Rosilene Oliveira, Coutinho, Flaviane Silva, Vital, Camilo Elber, Nepomuceno, Alexandre Lima, Rhys Williams, Thomas Christopher, Josué de Oliveira Ramos, Humberto, Loureiro, Marcelo Ehlers
• Format: Article
• Language: English
• Subjects: Brazil; Droughts; Genotype; Glycine max - physiology; Photosynthesis; Plant breeding; Plant Leaves - physiology; Plant physiology; Plant Roots - physiology; Stress, Physiological; Tolerance mechanism; Water - physiology; Water-use efficiency
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2020.03.004

Drought is one of the major constraints for soybean production in Brazil. In this study we investigated the physiological traits of two soybean parental genotypes under progressive soil drying and rewetting. The plants were evaluated under full irrigation (control) conditions and under water deficit imposed by suspending irrigation until the plants reached predawn leaf water potentials (Ψam) of −1.0 MPa (moderate) and −1.5 MPa (severe). Physiological analyses showed that these genotypes exhibit different responses to water deficit. The Embrapa 48 genotype reached moderate and severe water potential two days after the BR16 genotype and was able to maintain higher levels of A, ETR and ΦPSII even under deficit conditions. This result was not related to changes in gs, 13C isotopic composition and presence of a more efficient antioxidant system. In addition, Fv/Fm values did not decrease in Embrapa 48 genotype in relation to irrigated condition showing that stress was not causing photochemical inhibition of photosynthesis. The greater reduction in the relative growth of the shoots, with concomitant greater growth of the root system under drought, indicates that the tolerant genotype is able to preferentially allocated carbon to the roots, presenting less damage to photosynthesis. Therefore, the physiological responses revealed that the tolerant genotype postponed leaf dehydration by a mechanism involving a more efficient use and translocation of water from root to shoot to maintain cell homeostasis and photosynthetic metabolism under stress. •Drought soybean postpones dehydration by two days compared to parental genotype.•Maintains higher CO2 assimilation, electron transport rate and photochemical efficiency even under deficit conditions.•More efficient use and translocation of water from root to the shoot to maintain cell homeostasis under stress.•Integrative molecular physiology needed to decipher drought tolerance mechanisms.