Abstract
Drought impairs growth and spike development, and is therefore a major cause of yield losses in the temperate cereals barley and wheat. Here, we show that the photoperiod response gene PHOTOPERIOD-H1 (Ppd-H1) interacts with drought stress signals to modulate spike development. We tested the effects of a continuous mild and a transient severe drought stress on developmental timing and spike development in spring barley cultivars with a natural mutation in ppd-H1 and derived introgression lines carrying the wild-type Ppd-H1 allele from wild barley. Mild drought reduced the spikelet number and delayed floral development in spring cultivars but not in the introgression lines with a wild-type Ppd-H1 allele. Similarly, drought-triggered reductions in plant height, and tiller and spike number were more pronounced in the parental lines compared with the introgression lines. Transient severe stress halted growth and floral development; upon rewatering, introgression lines, but not the spring cultivars, accelerated development so that control and stressed plants flowered almost simultaneously. These genetic differences in development were correlated with a differential down-regulation of the flowering promotors FLOWERING LOCUS T1 and the BARLEY MADS-box genes BM3 and BM8. Our findings therefore demonstrate that Ppd-H1 affects developmental plasticity in response to drought in barley.
Highlights
Global warming increases the frequency and intensity of severe water scarcity events, which negatively affect the yield of rain-fed crops such as barley (Hordeum vulgare L.)and wheat (Triticum aestivum L.) (Xie et al, 2018; Kahiluoto et al, 2019)
We show that variation at Ppd-H1 interacts with drought to control flowering time, grain yield, as well as the expression of FLOWERING LOCUS T1 (FT1) and the downstream MADS-box genes BM3 and BM8
We quantified the effects of drought on developmental timing, growth and inflorescence morphology in the spring barley genotypes Scarlett, Golden Promise and Bowman with a natural mutation in the CCT domain of Ppd-H1 and in the derived introgression lines S42-IL107 (Scarlett), GP-fast (Golden Promise), and BW281 (Bowman) that carry wild-type Ppd-H1 alleles introgressed from wild barley
Summary
Global warming increases the frequency and intensity of severe water scarcity events, which negatively affect the yield of rain-fed crops such as barley (Hordeum vulgare L.)and wheat (Triticum aestivum L.) (Xie et al, 2018; Kahiluoto et al, 2019). Drought during reproductive development impairs spike development and floret fertility and is a major cause of yield losses in these temperate cereals (Gol et al, 2017). Strategies to breed cereal varieties with improved yield under drought are limited due to a lack of knowledge on the genetic factors that control inflorescence and flower development under drought conditions. Understanding the plasticity and genetic control of stress-induced changes in reproductive development will be crucial to ensure future yield stability of temperate cereals. The model plant Arabidopsis thaliana accelerates reproductive development under drought, a response that has been termed drought escape. In Arabidopsis drought escape is triggered under inductive long day (LD) conditions and is controlled by components of the circadian clock and the photoperiod response pathway (Riboni et al, 2013, 2016).
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