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Downy Mildew Klein


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Downy Mildew Klein

  1. 1. Jamie Klein FINAL VERSION—READY TO EDIT Process Brief Revision 3 April 12, 2010 Sorghum Downy Mildew Small white downy splotches or light and dark streaks of green on sorghum leaves are disconcerting to farmers and scientists because they point to sorghum downy mildew, an infectious disease that reduces the amount of grain produced by a field of sorghum. Growing sorghum that resists downy mildew is a goal the International Sorghum and Millet Collaborative Research Support Program (INTSORMIL) hopes to achieve through its worldwide research efforts. Sorghum is internationally grown, and according to INTSORMIL reports, is an African dietary staple. Farmers in Africa grow sorghum to feed their families and livestock, so downy mildew’s ability to reduce the crop’s yield is a major concern, said Gary Odvody, an associate professor with Texas A&M Research and Extension Center who also works with INTSORMIL. The fungus is borne in soil and, if sorghum plants aren’t around to be infected, remains in the ground between farming seasons, Odvody said. When a susceptible sorghum plant is nearby, spores from the fungus infect sorghum plant roots and grow with the plant. Sorghum sprouts out of the ground about a week after it is planted, he added. Symptoms of downy mildew, including multi-colored leaves with fuzzy white spots underneath, are noticeable three or four weeks after the sorghum is planted, Odvody said. “We look at it as a mosaic pattern of light-colored cells and green cells of the host,” he said.
  2. 2. The leaves may also have alternating parallel stripes of green and yellowish-green to white tissue; and leaves with the lighter stripes eventually die, according to a University of Nebraska-Lincoln Department of Plant Pathology Web site. Infected plants probably die without producing any grain, Odvody added. INTSORMIL sorghum breeders are growing sorghum from various genetic backgrounds and testing them for downy-mildew resistance, Odvody said. If sorghum breeders can identify which types of sorghum are resistant then it’s possible to create resistant hybrids for farmers to use around the world. And for that reason, Odvody said sorghum downy mildew is an “internationally important disease.” ###