Agronomic Implications of Kernel Weight and Protein Content of Kansas Wheat

Abstract

An apparent decline in kernel weight of some new wheat cultivars may affect segments of the Kansas wheat industry. The objective of this report is to review the literature relating to the problem and to discuss the implications of declining kernel weight to the agronomic aspects of the wheat industry. High grain yield of recent wheat cultivars apparently was achieved by setting more kernels per spike, which is partially countered by lower mean kernel weight. Comparisons of large and small seed sources usually show that small seeds produce less vigorous seedlings that yield less grain. Other evidence suggests that the low total protein content of small seeds, not their small size per se, is the important factor. Wheat breeders might well emphasize higher kernel weight to reverse the apparently adverse trend of this important yield component. Testing programs may need to consider uniformity of seed sources to ensure fairness of cultivar comparisons. Wheat growers might need to adjust seeding rates of small-seeded cultivars when recommended rates are based on seed weight or volume. Wheat kernel weight has implications for all segments of the wheat industry. New cultivars achieve greater productivity by setting more kernels per spike under favorable conditions; they set three or more kernels per spikelet, whereas older cultivars generally set only two. Because yield components tend to compensate, greater seed set is accompanied by smaller kernels or by variation among the kernels in the spikelet. The purpose of this paper is to review the literature on agronomic importance of wheat kernel size, investigate the trend of kernel weight of new wheat cultivars in Kansas, and explore implications of changes in wheat kernel weight in the state.