Abstract
Drought escape (DE) is a classical adaptive mechanism which involves rapid plant development to enable the completion of the full life-cycle prior to a coming drought event. This strategy is widely used in populations of native plants, and is also applicable to cereal crops such as wheat. Early flowering time and a shorter vegetative phase can be very important for wheat production in conditions of terminal drought since this can minimize exposure to dehydration during the sensitive flowering and post-anthesis grain filling periods. A gradual shift toward early flowering has been observed over the last century of wheat breeding in countries with a Mediterranean-type climate and frequent terminal drought. This trend is predicted to continue for wheat production in the coming years in response to global climate warming. The advantage of early flowering wheat is apparent under conditions of impending terminal drought, and modern varieties are significantly more productive due to minimization of the risk associated with drought stress. Under favorable conditions, a short vegetative phase can result in reduced plant biomass due to the reduction in time available for photosynthetic production and seed nutrient accumulation. However, high yield potential has been reported for the development of both shallow and deep roots, representing plasticity in response to drought in combination with the early flowering trait. Wheat productivity can be high both in well-watered and drought-affected field trials, where an efficient strategy of DE was associated with quick growth, yield potential and water use efficiency. Therefore, early flowering provides a promising strategy for the production of advanced drought-adapted wheat cultivars.
Highlights
Yuri Shavrukov1,2*, Akhylbek Kurishbayev3, Satyvaldy Jatayev3, Vladimir Shvidchenko3, Lyudmila Zotova3, Francois Koekemoer4, Stephan de Groot4, Kathleen Soole1 and Peter Langridge2
Flowering time and a shorter vegetative phase can be very important for wheat production in conditions of terminal drought since this can minimize exposure to dehydration during the sensitive flowering and post-anthesis grain filling periods
The advantage of early flowering wheat is apparent under conditions of impending terminal drought, and modern varieties are significantly more productive due to minimization of the risk associated with drought stress
Summary
Drought escape is one of many strategies employed by plants under conditions where water limitation late in the growing season is likely, and it ensures that the plants can complete their life-cycle quickly during the brief period of favorable conditions. In India and Pakistan, significantly higher grain yields in adapted EM wheat cultivars and mutant lines, respectively, were reported under conditions of terminal drought compared to non-EM controls (Nagarajan et al, 2008; Sial et al, 2008) These varieties were characterized as having a longer ‘time to heading’ and moderate grain filling duration, but with high grain filling rates enabling early maturation (Laxman et al, 2014). A potential negative effect of EFT wheat with SVP in this region of Asia was not recorded in modeling, with possible limits on biomass accumulation found to be “more than counterbalanced by more favorable growth conditions” (Sommer et al, 2013) One such scenario was proven in ‘openair facilities’ in Northern China and Tibet, where wheat plants grown in artificially warmed fields (0.5–1◦C higher than that of non-warmed fields) produced more green leaf area, spikes and biomass, and increased yield by 8.4– 11.4%, in association with both EFT and SVP of 5–9 and. Without HYP, the traits of EFT/EM have a positive effect on commercial wheat production only when limited by terminal drought conditions
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