Concept
Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of ascomycete fungi in the order Erysiphales. Powdery mildew is one of the easier plant diseases to identify, as its symptoms are quite distinctive. Infected plants display white powdery spots on the leaves and stems. The lower leaves are the most affected, but the mildew can appear on any above-ground part of the plant. As the disease progresses, the spots get larger and denser as large numbers of asexual spores are formed, and the mildew may spread up and down the length of the plant. Powdery mildew grows well in environments with high humidity and moderate temperatures. Greenhouses provide an ideal moist, temperate environment for the spread of the disease. This causes harm to agricultural and horticultural practices where powdery mildew may thrive in a greenhouse setting. In an agricultural or horticultural setting, the pathogen can be controlled using chemical methods, bio-organic methods, and genetic resistance. It is important to be aware of powdery mildew and its management as the resulting disease can significantly reduce important crop yields. Powdery mildew fungi reproduce both sexually and asexually. Sexual reproduction occurs via chasmothecia (formerly cleistothecium), a type of ascocarp in which genetic recombination takes place. Within each ascocarp are several asci. Powdery mildew fungi must be adapted to their host for successful infection. Under optimal conditions, ascospores mature and are released to initiate new infections. Conditions necessary for spore maturation differ among species. In asexual reproduction, the mother fungi and offspring are genetically identical. Asexual reproduction is the predominant form of reproduction and dispersal in powdery mildew infections of wheat and barley species, as compard to sexual reproduction Yet sexual reproduction results in durable and resistant overwintering spores, produced in chasmothecia.
