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Disease Note. First Report of Take-All of Wheat in Texas. D. Marshall, Texas Agricultural Experiment Station, Texas A&M University Research and Extension Center, Dallas 75252. Plant Dis. 71:850. Accepted for publication 26 June 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0850B. The take-all fungus, Gaeumannomyces graminis (Sacc.) von Arx & Olivier var. tritici Walker, was isolated from stem bases of dead plants of wheat (Triticum aestivum L.) cultivars Triumph 64 in Deaf Smith County, Texas, and TAM 105 in Wilbarger County in May 1986. The wheat in both fields was grown under overhead irrigation. Plants with sterile white heads were found in nearly circular patches 0.3-3.7 m in diameter. Dead plants were easily removed from the soil and had darkened roots and blackened stem bases. Sparse perithecia, 188-345 Mm in diameter and 130-215 Mm long, were found in leaf sheaths. Asci were 95-135 X 10-15 µm, and ascospores were eight per ascus, slightly curved with rounded ends, and 75-110 µm X 3-4 µm. G. graminis var. tritici was isolated from stem sections on SM-GGT3 medium (1). Koch's postulates were fulfilled on 25 single plants of TAM 105 grown in test tubes and inoculated with agar disks of G. graminis var. tritici. Similar symptoms were observed in numerous wheat fields in west and north, but not central or south, Texas. |