Heat Tolerance in Winter Wheat: I. Hardening and Genetic Effects on Membrane Thermostability
Identification of heat-tolerant winter wheat (Triticum aestivum L.) genotypes for the central and southern Great Plains of the USA as well as other areas of the world is desirable. In this study, the suitability of using the membrane thermostability (MT) test for ascertaining heat tolerance of winter wheat was determined. The MT test was conducted on seven cultivars using seedlings exposed to 0, 6, 12,18, 24, and 48 h of hardening (34 °C) and flag leaf material from the same cultivars grown to anthesis and exposed to 0, 48, and 120 h of hardening (34 °C), with the results expressed as relative injury (RI). Additionally, the MT test was conducted on 90 F5 genotypes derived from two crosses (45 genotypes per cross) involving one heattolerant and two heat-sensitive parents (parents were a subset of seven previous cultivars). Plant material for the MT test was sampled at seedling (hardened for 48 h at 34 °C) and anthesis (hardened for 120 h at 34 °C) stages of growth. Large differences in RI were observed among the seven cultivars at both growth stages, ranging from 37 to 80% RI for seedlings and 31 to 69% RI at anthesis. The treatment protocols involving hardening for 48 and 120 h at seedling and anthesis stages, respectively, provided the greatest sensitivity in detecting genotypic differences in RI. The correlation of RI assessment for seedlings vs. that at anthesis for the 90 F5 genotypes was 0.79 (P ≤ 0.01), indicating that RI determined at the two developmental stages was highly associated.
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