Giovanni Melandri, Hamada AbdElgawad, Kristýna Floková, Diaan C Jamar, Han Asard, Gerrit T S Beemster , Carolien Ruyter-Spira, Harro J Bouwmeester

Planta 2021 Jun 25;254(1):13.  doi: 10.1007/s00425-021-03659-4.

Abstract

Sugar-mediated osmotic acclimation and a strong antioxidative response reduce drought-induced biomass loss at the vegetative stage in rice. A clear understanding of the physiological and biochemical adaptations to water limitation in upland and aerobic rice can help to identify the mechanisms underlying their tolerance to low water availability. In this study, three indica rice varieties-IR64 (lowland), Apo (aerobic), and UPL Ri-7 (upland)-, that are characterized by contrasting levels of drought tolerance, were exposed to drought at the vegetative stage. Drought-induced changes in biomass, leaf metabolites and oxidative stress markers/enzyme activities were analyzed in each variety at multiple time points. The two drought-tolerant varieties, Apo and UPL Ri-7 displayed a reduced water use in contrast to the susceptible variety IR64 that displayed high water consumption and consequent strong leaf dehydration upon drought treatment. A sugar-mediated osmotic acclimation in UPL Ri-7 and a strong antioxidative response in Apo were both effective in limiting the drought-induced biomass loss in these two varieties, while biomass loss was high in IR64, also after recovery. A qualitative comparison of these results with the ones of a similar experiment conducted in the field at the reproductive stage showed that only Apo, which also in this stage showed the highest antioxidant power, was able to maintain a stable grain yield under stress. Our results show that different metabolic and antioxidant adaptations confer drought tolerance to aerobic and upland rice varieties in the vegetative stage. The effectiveness of these adaptations differs between developmental stages. Unraveling the genetic control of these mechanisms might be exploited in breeding for new rice varieties adapted to water-limited environments.

See https://pubmed.ncbi.nlm.nih.gov/34173050/

Figure 1: Evolution of soil water content in the three rice varieties. Each data point represents the mean value of soil moisture content (%) of 12 different plants (± SE) per variety. The first time point (TP1, early-mild drought) was selected 4 days after water withholding for all varieties. The second time point (TP2) was selected targeting a same specific soil moisture content (~ 40% of maximum soil moisture content) between the varieties (6 days after water withholding in IR64 and 7 days in Apo and Ri-7). The third time point (TP3) was selected 10 days after water withholding for all varieties.