Short periods of high temperature during meiosis prevent normal meiotic progression and reduce grain number in hexaploid wheat (Triticum aestivum L.)

Abstract

Key message Exposure of wheat to high temperatures during male meiosis prevents normal meiotic progression and reduces grain number. We define a temperature-sensitive period and link heat tolerance to chromosome 5D. AbstractThis study assesses the effects of heat on meiotic progression and grain number in hexaploid wheat (Triticum aestivum L. var. Chinese Spring), defines a heat-sensitive stage and evaluates the role of chromosome 5D in heat tolerance. Plants were exposed to high temperatures (30 or 35 °C) in a controlled environment room for 20-h periods during meiosis and the premeiotic interphase just prior to meiosis. Examination of pollen mother cells (PMCs) from immature anthers immediately before and after heat treatment enabled precise identification of the developmental phases being exposed to heat. A temperature-sensitive period was defined, lasting from premeiotic interphase to late leptotene, during which heat can prevent PMCs from progressing through meiosis. PMCs exposed to 35 °C were less likely to progress than those exposed to 30 °C. Grain number per spike was reduced at 30 °C, and reduced even further at 35 °C. Chinese Spring nullisomic 5D-tetrasomic 5B (N5DT5B) plants, which lack chromosome 5D, were more susceptible to heat during premeiosis–leptotene than Chinese Spring plants with the normal (euploid) chromosome complement. The proportion of plants with PMCs progressing through meiosis after heat treatment was lower for N5DT5B plants than for euploids, but the difference was not significant. However, following exposure to 30 °C, in euploid plants grain number was reduced (though not significantly), whereas in N5DT5B plants the reduction was highly significant. After exposure to 35 °C, the reduction in grain number was highly significant for both genotypes. Implications of these findings for the breeding of thermotolerant wheat are discussed.

Dmc1is a candidate for temperature tolerance during wheat meiosis

“…This is also the case for low temperatures, with meiosis I identified as the most sensitive stage (Thakur et al 2010). High temperatures during reproductive development can have a negative impact on grain yield (Fischer and Maurer 1976;Fischer 1985;Wardlaw et al 1989), and even short periods of a moderately high temperature (20-24 hours at 30°C) during meiosis can reduce grain number (Saini and Aspinall 1982;Draeger and Moore 2017). Grain yield is also reduced when low temperatures occur during the booting stage (Ji et al 2017), which broadly corresponds to meiosis (Barber et al 2015).…”

“…However, this suggestion was based on the scoring of only a few cells because exposure of the plants to high temperatures for three days made the chromosomes too sticky to score accurately. Grain number is also reduced much more in N5DT5B plants than in the wild type after exposure to 30°C during premeiosis and leptotene (Draeger and Moore 2017).…”

Heat Tolerance of Durum Wheat (Tritcum durum Desf.) Elite Germplasm Tested along the Senegal River

“…In addition, when heat occurs at the time of flowering it can reduce the vitality of the pollen and fertilization during pollen formation (Barlow et al, 2015;Draeger & Moore, 2017). Instead, during the grain filling period, heat stress reduces grain size and its weight (Dias & Lidon, 2009).…”

Temperature-induced changes in wheat phosphoproteome reveal temperature-regulated interconversion of phosphoforms

“…Here, we exposed 7 days old wheat seedlings (Fielder) grown at 24°C for a short-term treatment of 34°C and harvested whole shoots at different incubation times ( Figure 1A ). Recent evidence in cereal crop plants has demonstrated a link between high temperature sensitivity at booting stage and seed yield (Hedhly et al , 2009; Draeger and Moore, 2017). Hence, we used booting wheat plants (Cadenza) grown at 21°C and exposed to increased ambient temperature (34°C), after which we harvested spikelets at different incubation times ( Figure 1B ).…”

“…During wheat vegetative development, traits affected by high temperature include plant height, specific leaf weight, leaf width, relative water content, chlorophyll content and secondary metabolites (Akter and Rafiqul Islam, 2017). Furthermore, generative wheat growth and development are also very susceptible to increased temperatures (Bennett et al , 1971; Sainiab et al , 1983; Saini et al , 1984; Draeger and Moore, 2017). Specifically, when wheat flowers are exposed to heat stress (10°C above the optimum condition) at the stage between ear initiation and anthesis (when anther development goes through meiosis) this causes abnormal development of the pollen grains in the anther and subsequently results in grain yield reduction (Sainiab et al , 1983; Saini et al , 1984; Fischer, 1985; Wardlaw et al , 1989).…”