Stage-Specific Characterization of Physiological Response to Heat Stress in the Wheat Cultivar Norin 61

Abstract

Bread wheat (Triticum aestivum) is less adaptable to high temperatures than other major cereals. Previous studies of the effects of high temperature on wheat focused on the reproductive stage. There are few reports on yield after high temperatures at other growth stages. Understanding growth-stage-specific responses to heat stress will contribute to the development of tolerant lines suited to high temperatures at various stages. We exposed wheat cultivar “Norin 61” to high temperature at three growth stages: seedling–tillering (GS1), tillering–flowering (GS2), and flowering–maturity (GS3). We compared each condition based on agronomical traits, seed maturity, and photosynthesis results. Heat at GS2 reduced plant height and number of grains, and heat at GS3 reduced the grain formation period and grain weight. However, heat at GS1 reduced senescence and prolonged grain formation, increasing grain weight without reducing yield. These data provide fundamental insights into the biochemical and molecular adaptations of bread wheat to high-temperature stresses and have implications for the development of wheat lines that can respond to high temperatures at various times of the year.

Metabolome Profiling of Heat Priming Effects, Senescence, and Acclimation of Bread Wheat Induced by High Temperatures at Different Growth Stages

“…The changes in metabolite concentrations described in the previous sections were correlated with the values of the agronomic traits obtained in our previous study ( Figure 6 , Tables S4 and S5 ) [ 12 ]. Matsunaga et al [ 12 ] divided agronomic traits into three clusters based on the response to high-temperature treatment: in agronomical cluster 1, traits were positively affected by heat during GS1; in agronomical cluster 2, traits were negatively affected by heat during all stages; and in agronomical cluster 3, traits were affected negatively by heat during GS1 but positively during GS3.…”

“…Previous studies suggested that high temperature during certain growth stages affects the senescence rate during seed formation [ 12 ]. Therefore, to explore the metabolic changes during the seed formation period under each temperature condition ( Figure 1 ), we quantified the stably detected metabolites (amino acids, organic acids, nucleic acids, and hormones) in the most recent flag leaves at 7 days post-anthesis (DPA) ( Table S1 ).…”

“…Matsunaga et al [ 12 ] reported that control plants grown under standard conditions showed the onset of leaf senescence at 14 DPA and that the plants treated with high temperature during GS3 showed apparent leaf senescence by 14 DPA after losing carbon assimilation capacity. On the other hand, plants treated with a high temperature during all growth stages (GS1–3) were able to maintain high photosynthetic activity even at 14 DPA.…”

“…Generally, purines and pyrimidines are either regenerated into nucleic acids through salvage and phosphorylation, or are degraded into amino acids, urea, ribose, NH 4 + , and CO 2 under nitrogen starvation and during leaf senescence. Matsunaga et al [ 12 ] measured that the rate of carbon assimilation at 14 DPA by photosynthesis measurement and found decrease in the order GS3 > GS1–3 > GS2 > control > GS1. In the present study, we found that the accumulation of beta-alanine at 7 DPA showed the same trend ( Figure 7 A).…”

“…In our previous study, we exposed the bread wheat cultivar ‘Norin 61’ to high temperatures (38 °C), which is the temperature in Wad Medani, Sudan, the world hottest area for wheat production, during different growth stages, and analyzed the morphological and physiological stress responses [ 12 ]. Additionally, previous research reported 50% decrease in rubisco activity at temperatures near 38 degrees Celsius [ 13 ].…”