Heat Tolerance in Winter Wheat: II. Membrane Thermostability and Field Performance
High-temperature stress during the grain-fill period of wheat is one of the major constraints to increased production. The objective of this work was to determine the relationship between membrane thermostability (MT) and other agronomic traits of winter wheat (Triticum aestivum L .). Hardened seedlings of 137 F5 genotypes (derived from crosses of heat-tolerant and sensitive parents) and seven cultivars were evaluated for MT and the results expresseds relative injury (RI). The same 144 genotypes were grown at three field sites in eastern Colorado and evaluated for maturity (days to anthesis), grain yield, grain volume weight, and yield components. Relative injury varied significantly (P ≤ 0.01) among the 144 genotypes, with arange of 31 to 78%. Based on RI values, the genotypes were separated in to three groups: heat-tolerant (HT), intermediate (I), and heat-sensitive (HS). Accordingly, 27 genotypes were classified as HT, 71 as I, and 46 as HS. There were no differences in maturity among the three groups, indicating no association between maturity and RI. At one site, the HT group produced 9 and 19% more yield than the I and HS groups, respectively, and the trend in yield among the three groups was similar at the other two sites. Additionally, grain volume weight and kernel weight were greater for the HT vs. I or HS group at all three sites. Thus, heat tolerance, as evaluated by the MT test, was associated with grain yield and quality. These results suggest that the MT test would be a suitable procedure for selecting heat-tolerant winter wheat genotype in a breeding program.
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