Fig. 1.

Comparison of effects of 5AQ on morphological and domestication-related traits of hexaploid wheat cv. CS spikes. (A) Presence of 5AQ confers a square-shaped spike (Left), and the absence of 5AQ (in the deletion mutant CS del143) (Right) results in a speltoid spike characterized by a much longer and spear-shaped spike compared with the spike of CS primarily due to the elongation of rachis segments. (B) Seed of CS with 5AQ (Left) is free threshing because the seed is loosely held and abscission occurs at the base of the glumes, leaving the rachis intact. CS lacking the 5AQ gene (Right) is not free threshing because the glumes hold the seed more tightly and abscission occurs within the rachis, causing disarticulation of the entire spikelet with a portion of the rachis left attached to the base of the spikelet. (C) Detailed illustration of a single spikelet of CS when 5AQ is present (Left) and absent (Right). Both spikelets have three fertile florets (first, second, and third) and each spikelet has a pair of glumes (1). Each floret has a lemma (2), seed (3), and palea (4). Note the looseness of the seeds due to the difference in the position of the glumes in 5AQ compared with the mutant lacking 5AQ. The abscission zones are indicated by the blue arrows (the lower spikelet in the 5AQ mutant was removed so that the abscission zone could be observed).