Biology and epidemiology of downy mildew [Sclerospora graminicola] of pearl millet [a review article]
1987
Shetty, H.S.
Sclerospora graminicola is an important pathogen on pearl millet in the semi-arid tropics. The primary inoculum source is seed or soil, but the secondary spread is by airborne sporangia. Sexually produced oospores can survive under dry conditions for more than 5 years. Asexual propagules are ephemeral and fragile. Their production, liberation, deposition, and germination are greatly influenced by environmental factors, as are penetration, infection, a2010nd disease development. Epidemiological studies indicate that dew formation is the most important factor that governs disease development. In addition, disease incidence positively correlates with relative humidity and maximum temperature. The fungus was cultured in association with its host tissue callus (dual culture) and the life cycle was completed successfully in vitro. Inoculated seeds and systematically infected shoot tips of the host are good source materials to establish the dual culture on a semi-synthetic medium. The dual culture technique can be utilized to screen host cultivars against downy mildew reaction. Vegetative mycelium of S. graminicola is coenocytic. During sporogenesis nuclei migrate to sporangiophores and sporangia to form multinucleate structures. Zoospores formed from sporangia are uninucleated. There is no nuclear division in the zoospores, sporangia, and sporangiophores. However, nuclear divisions are common in the germ tubes of zoospores during germina
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