Temporally and Genetically Discrete Periods of Wheat Sensitivity to High Temperature

Abstract

Successive single day transfers of pot-grown wheat to high temperature (35/30°C day/night) replicated controlled environments, from the second node detectable to the milky-ripe growth stages, provides the strongest available evidence that the fertility of wheat can be highly vulnerable to heat stress during two discrete peak periods of susceptibility: early booting [decimal growth stage (GS) 41–45] and early anthesis (GS 61–65). A double Gaussian fitted simultaneously to grain number and weight data from two contrasting elite lines (Renesansa, listed in Serbia, Ppd-D1a, Rht8; Savannah, listed in UK, Ppd-D1b, Rht-D1b) identified peak periods of main stem susceptibility centered on 3 (s.e. = 0.82) and 18 (s.e. = 0.55) days (mean daily temperature = 14.3°C) pre-GS 65 for both cultivars. Severity of effect depended on genotype, growth stage and their interaction: grain set relative to that achieved at 20/15°C dropped below 80% for Savannah at booting and Renesansa at anthesis. Savannah was relatively tolerant to heat stress at anthesis. A further experiment including 62 lines of the mapping, doubled-haploid progeny of Renesansa × Savannah found tolerance at anthesis to be associated with Ppd-D1b, Rht-D1b, and a QTL from Renesansa on chromosome 2A. None of the relevant markers were associated with tolerance during booting. Rht8 was never associated with heat stress tolerance, a lack of effect confirmed in a further experiment where Rht8 was included in a comparison of near isogenic lines in a cv. Paragon background. Some compensatory increases in mean grain weight were observed, but only when stress was applied during booting and only where Ppd-D1a was absent.

Quantifying the Impact of Heat Stress on Pollen Germination, Seed Set, and Grain Filling in Spring Wheat

“…Similarly, ?50% reduction in seed weight among synthetic wheat was recorded when exposed to heat stress (35°C for 10 d) after anthesis (Yang et al, 2002). In our study, heat stress during flowering for 10 d recorded negative impact on both seed number (spike −1 ) and seed weight (spike −1 ), whereas the impact of heat stress during grain filling was more severe on seed weight, which supports earlier observations in wheat (Saini and Aspinall, 1982;Liu et al, 2016;Barber et al, 2017). The reduction in seed weight (spike −1 ) with stress during flowering was a mere reflection of the significant decline in seed number than weight per seed.…”

Durum Wheat Landraces from East and West Regions of the Mediterranean Basin Are Genetically Distinct for Yield Components and Phenology

“…The fact that eastern landraces had larger numbers of spikes per unit area than those from the west Mediterranean countries, may be interpreted as an evolutionary adaptive mechanism to compensate for the negative effect of water scarcity on the formation of spikes. Similarly, the larger number of grains per unit area, whose potential is determined before booting (Isidro et al, 2011 ), may be a means to compensate for the degeneration of florets occurring from booting to flowering (Isidro et al, 2011 ) and the subsequent reduction in grain setting caused by heat and drought stress (Barber et al, 2017 ). The high frequency of alleles conferring a high number of spikes and grains in landraces collected in the four eastern countries (93% in both cases) may be biologically interpreted as a mechanism for achieving higher grain yield.…”

Non-destructive, high-content analysis of wheat grain traits using X-ray micro computed tomography

“…We found that temperature differentially affects grain formation along the spike with the middle of the spike being more sensitive to the stresses. Recent studies have shown that there are two discrete developmental stages where the spike is more sensitive to temperature: early booting when meiosis is occurring and anthesis [ 8 – 10 ]. Floret development along the spike is asynchronous [ 12 ] it is thus tempting to speculate that the florets in the middle were at a temperature-sensitive stage when the stress was applied.…”

“…Drought also has a significant impact on wheat yield particularly when applied during the reproductive phase [ 11 ]. The effect on yield has mainly been attributed to reduced grain number although, for some varieties and at specific growth stages, grain size could increase to compensate for this [ 9 , 10 ].…”