Description

Commonly known as Ergot, lives most of its life as an endophyte inside the cells of graminaceous plants, particularly rye. This fungus infects rye through the stigma of its flower and produces a mycelial mat that replaces the plant’s ovarian tissues. This mycelial mat develops into conspicuous brownish-black sclerotia that can be found growing from the inflorescence of the plants. Sclerotia are elongated, 1.5-3.5cm long, cylindrical, rounded at the ends, and firm. They are often curved and have slight longitudinal grooves. Usually dark brown to black on the outside and a lighter grayish-white on the inside. One to several sclerotia may be found growing from a single grass inflorescence (Image 1 & Image 2). When Spring comes, small, mushroom-like stromata emerge from sclerotia that have fallen to the ground. A short stalk elevates a globose head that is approximately 2mm in diameter. Along the head perithecia form. Inside these structures, needle-like sexually formed ascospores develop in elongated asci. Each ascus contains 8 ascospores. The hyaline ascospores are approximately 65-100um x 0.5-1um. The tips of the asci turn blue in Melzer’s reagent. The ascospores are forcibly ejected through a long neck-like ostiole. (Image 3 & Image 4). The ascospores are wind disseminated and germinate when they land on the flowers of rye (or other susceptible plants in bloom). Germ tubes infect the ovary, destroying tissue and replacing it with mycelium. Short conidiophores bearing tiny oval conidia form. Insects visiting the flower can transfer these asexually produced conidia to uninfected flowers and transfer the fungus.