Changes in Water Status, Membrane Stability and Antioxidant Capacity of Wheat Seedlings Carrying Different Rht‐B1 Dwarfing Alleles under Drought Stress

Abstract

Water deficiency is a major constraint to wheat productivity in drought prone regions. The wheat DELLA‐encoding height‐reducing genes (Rht) are associated with significant increase in grain yield. However, the knowledge of their benefit in dry environments is insufficient. The objective of the study was to examine the effect of induced drought on leaf water content, level of oxidative stress, cell membrane stability, accumulation of osmoprotectants and activity of some antioxidant enzymes in wheat near‐isogenic lines carrying the alleles Rht‐B1b (semidwarfing) and Rht‐B1c (dwarfing) in comparison with the tall control Rht‐B1a. Six‐day‐long water deprivation was imposed at seedling stage. Plants carrying Rht‐B1c and, to a lesser extent, those carrying Rht‐B1b performed better under stress compared with Rht‐B1a in terms of more sustained membrane integrity, enhanced osmoregulation and better antioxidant defence. These differential responses could reflect pleiotropic effects of the Rht‐B1 gene associated with the accumulation of the mutant gene product, that is, altered DELLA proteins, or might be related to allelic variations at neighbouring loci carrying candidate genes for proteins with a major role in plant water regulations and stress adaptation. These findings might be of importance to breeders when introducing Rht‐B1 alleles into wheat cultivars designed to be grown in drought liable regions.

Wheat Rht‐B1 Dwarfs Exhibit Better Photosynthetic Response to Water Deficit at Seedling Stage Compared to the Wild Type

“…The lack of increased non‐photochemical quenching in Rht‐B1c was not due to broken energy dissipation by down regulation, as supposed by Sperdouli and Moustakas (), because earlier we demonstrated that it was the line with the lowest lipid peroxidation and injury index under drought (Kocheva et al. ). Rht‐B1c plants had lower necessity for photoprotection because they had to cope with less excessive light due to both more preserved part of excitation energy directed for photochemical utilization, and to lower light absorption, due to higher surface reflectance of more pubescent leaves (Demmig‐Adams and Adams , ).…”

“…One possible explanation for this could be sought in the pleiotropic effect of the Rht genes not only on stem elongation but also on leaf structure and on some metabolic reactions (Gent and Kiyomoto , Kocheva et al. ). The changes in leaf anatomy and gas exchange parameters of control plants, found in this study, are in consonance with previous findin g s of other authors (LeCain et al.…”

“…Recently, we demonstrated that three of these lines differing in size reduction owing to the presence of Rht‐B1 alleles diverged in their reactions to water stress in terms of membrane integrity, osmoregulation and antioxidant defence (Kocheva et al. ). In this study, the reaction to soil drought of these lines was investigated with an emphasis on the photosynthetic performance, grounded on its importance for crop yield and its great sensitivity to drought.…”

Relationships between leaf morpho‐anatomy, water status and cell membrane stability in leaves of wheat seedlings subjected to severe soil drought

“…The Rht genes affect leaf size with a resultant decrease in leaf area of the whole plant (King, Gale, & Quarrie, ). In our earlier study on wheat Rht ‐near‐isogenic lines, we showed that compared to plants with the wild allele, the dwarf mutant Rht‐B1c plants had thicker leaves, less leaf area and higher density of stomata and trichome, and under induced drought stress exhibited greater tolerance evidenced by better preserved leaf water balance, more sustained membrane integrity, mobilized antioxidant defence and osmoregulation, and less affected photosynthetic activity (Kocheva et al., ; Nenova et al., ). Another semi‐dwarfing gene— Rht8, which is mostly distributed in warmer and drier environments (Chebotar, Korzun, & Sivolap, ; Ganeva, Korzun, Landjeva, Tsenov, & Atanasova, ) also leads to reduced cell elongation and reduced organs size, possibly, due to lower sensitivity to brassinosteroids (Gasperini et al., ).…”

Effects of dwarfing genes on water use efficiency of bread wheat

“…However, Rht-B1b plants have an intermediate character between wild type and Rht-B1c lines that often does not significantly differ from that of the Rht-B1a plants examined in the study. Rht-B1c seedling plants maintain a lower injury index and less malondialdehyde content under osmotic stress [79,80] . These results suggest that Rht-B1c seedlings can better modulate antioxidant defense systems to sustain membrane integrity and higher levels of photosynthesis.…”