Reproductive Characteristics of Winter Wheat Cultivars Subjected to Postanthesis Shading

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Abstract
High temperatures during reproductive development of soft red winter wheat [Triticum aestivum (L.) em Thell] reduce the length of the available grain filling period and may make cultivars grown in such environments more sensitive to short‐term reductions in light intensity. Therefore, short‐duration, postanthesis shading (63%) was applied to the cultivars Caldwell, Hart, and Wheeler (about 30, 38, and 45 mg kernel−1, respectively) to assess the impact of light intensity on kernel growth rate [(KGR) mg kernel−1 d−1 and other reproductive characteristics. Early shading [(ES) 1‐6 or 1‐8 after anthesis (DAA)] or midshading [(MS) 14‐21 or 15‐22 DAAI were used with Hart in 1986 to 1988 and the other cultivars in 1987 to 1988. Cultivars differed in relative response to shading with KGR of 1.55, 1.42, and 1.31 (Caldwell); 1.78, 1.75, and 1.59 (Hart); and 2.00, 1.89, and 1.79 (Wheeler) for control, ES, and MS, respectively. Yield reductions due to ES (8.6%) were related to depressed floret fertility (all coltivars) and kernels spike−1 (Hart only), while those due to MS (5.6%) resulted from lower KGR and kernel weight. Data from MS may support the conclusion that wheat yields are sourcelimited in some postanthesis environments, in contrast to a number of previous reports. A shortened reproductive period may be responsible for this observation.