The seed is the only component of the host plant infected by G. temulenta (Wilson et al. 1945). Infected caryopses appear shriveled, rough on the surface, and rusty brown or pinkish in color (Gemmell 1940, Calvert and Muskett 1945, Hyde 1945, Noble and Gray 1945, Wilson et al. 1945, Blair 1947). Conidia accumulate on the seed surface in a spore secretion (slime), which may be waxy and clear or pale pink in color (Hyde 1938a) or may appear as a reddish-brown crust (Calvert and Muskett 1945, Hyde 1945). Healthy caryopses normally appear golden brown, plump, and smooth (Calvert and Muskett 1945). However, infected seeds covered by the lemma and palea are difficult to discern from normal seeds (Gemmell 1940, Neill and Hyde 1942, Hyde 1945).
A consequence of blind seed infection is reduced germination, and the correlation between percentage of infected seed and percentage germination in ryegrass is well established (Hyde 1932; Gemmell 1940; Greenall 1943; Calvert and Muskett 1944, 1945; Hyde 1945; Lafferty 1948; Chestnutt 1958; Hardison 1963; de Tempe 1966; Matthews 1980). Germination of infected seed is rarely greater than 10 percent (Gemmell 1940, Lafferty 1948).
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Original posting: October 2001.