The Pathogens And Infection Machinism Of Black Point Of Wheat In Xinjiang

The black point disease of wheat occurred in most grain-growing areas of the world, causing considerablefinancial losses, and there are different in the frequencies of fungi isolated among years and areas . Thedisease severity and fungal identification were determined from the 119 samples of 31 counties in Xinjiang.According to the Koch's postulates,Alternaria tenuis C.G. Nees. was the main pathogen in allgrain-growing areas of Xinjiang, the isolated frequency and the re-inoculating isolated frequency were73.98% and 86.67% respectively; Biplaris sorokiniana (Sacc.) Shoem. was the second important pathogenmainly occurred in Altar, Boler and Qitai areas, the isolated frequency and the re-inoculating isolatedfrequency were 9.48% and 96.97% respectively. The pathogenicity of Biplaris sorokiniana (Sacc.) Shoem.was stronger than that of Alternaria tenuis C.G. Nees.; Exserohilum rostratum (Drech.) Leo.& Sug wasisolated from Turpan area only. It was the first report in Xinjiang, the re-inoculating isolated frequencyreached at 75% indicated that its pathogenicity was strong as well. Although Stemphylium consortiale(Thüm.) Goves & Skolko could cause the black point disease symptom, its pathogenicity was weaker thanothers. The infection of the black point disease of wheat resulted severe problems in seed germinating, therelativity between the disease severity, as well as the isolated frequency of Alternaria tenuis C.G. Nees. andthe germinating frequency were bally negative and significant Meanwhile Biplaris sorokiniana (Sacc.)Shoem. was the main pathogen to cause seedling disease on wheat.The period of infection was from the period of the heading date to middle filling of wheat, and the period oflast phase of flowering and early filling of wheat was the fittest period of infection. The pathogens caninvade wheat seed from the part of rachilla, lemma and glume. The indoor biology study suggested that themost suitable temperature for the development of Alternaria tenuis C.G. Nees. and Biplaris sorokiniana(Sacc.) Shoem. were 25~28℃and 25℃respectively, the suitable temperature for spore geminatingwere28℃and 25℃respectively . There were different in spore geminating and infesting between the twopathogens. Alternaria tenuis C.G. Nees. produced appressoria firstly, then invade plant organism bypenetration peg. Biplaris sorokiniana (Sacc.) Shoem could geminate from one end or both ends toproduce mycelium invading plant organism directly.The suppressive effects with nine pesticides againstAlternaria tenuis C.G. Nees. and Biplaris sorokiniana (Sacc.) Shoem. showed that Difenoconazole andDifenoconazole Propiconazole were more effective pesticides than the others.