Seed vigor of Katepwa Wheat: Interaction of kernel water content and threshing cylinder speed

Abstract

An important goal in seed production is the maintenance of seed vigor. Breakage of wheat seed (Triticum aestivum L.) during threshing can be reduced by threshing at relatively high kernel water content (KWC) and low cylinder speed. The purpose of this study was to investigate the interacting effects of KWC and threshing cylinder speed on seed vigor and field emergence of Katepwa wheat. Wheat plants were harvested at approximately 250 g kg−1 (dry basis) KWC and allowed to dry for varying lengths of time, then were threshed at cylinder speeds of 450, 850, and 1250 rpm using a Vogel thresher. At threshing, KWC averaged 89, 121, 156 and 231 g kg−1. Significant KWC × cylinder speed interactions occurred for seed yield per plot and various seed vigor indicators. Threshing at 850 rpm gave the highest yield of uncracked seeds regardless of KWC. Threshing at 450 rpm was incomplete, especially at high KWC, while threshing at 1250 rpm caused high levels of external seed damage, especially at low KWC. Vigor of uncracked seed was measured by cold germination tests. Increasing cylinder speed reduced cold germination, especially at high KWC. The incidence of abnormal seedlings and leachate conductivity increased with cylinder speed but increased only slightly as KWC decreased. Field emergence decreased with increasing cylinder speed, but was not affected by KWC at threshing. The number of abnormal seedlings in cold germination tests and leachate conductivity were the best indicators of field emergence. Threshing cylinder speed had a greater influence than KWC on seed damage, vigor, and field emergence. The results of this study are of greatest direct interest to plant breeders who use Vogel threshers regularly. Key words: Seed quality, seed vigor, seed damage, threshing, wheat, plant breeding, Triticum aestivum L.