Visual Markers of Maximum Grain Dry Weight Accumulation in Winter Wheat

Visual indicators that coincide with the time of maximum grain dry weight accumulation ( t max ) in hard red winter wheat ( Triticum aestivum L.) have not been confirmed. Our objective was to evaluate various potential visual markers of t max for a range of cultivars in typical Great Plains environments. Spikes of uniform maturity from five hard red winter and one soft white winter wheat cultivars were harvested throughout grain filling and divided into upper, middle, and bottom portions to determine grain dry weights. For each cultivar‐year combination, t max values for each spike portion and the entire spike were calculated using polynomial models derived from splined regression analysis. These values were compared with various visual traits observed at each harvest. There was no significant variation in t max among the three spike portions. Complete loss of green color from the flag leaf blade and sheath preceded t max by several days in all cultivars; green color in the node below the peduncle persisted 2 to 6 d beyond t max . Complete loss of green color from the rachis, glumes, and the crease of kernels occurred within 1 d of t max in all cases. The same was true for loss of awn color, except for the soft white winter cultivar, in which green color loss from awns occurred 2 d before t max . Thus, color loss from most portions of the spike should serve as accurate indicators of t max for hard red winter wheat in central Great Plains environments.