Identification and fungicide sensitivity of Brunneomyces pennisetum, a new species causing wilt disease of Pennisetum purpureum × P. americanum in southern China.

Abstract

Pennisetum purpureum × P. americanum is an important forage in southwest China. In recent years, a considerable number of wilting plants have occurred in forage-growing regions located in Yunnan Province. The typical symptoms were that the surface of the wilted stems turned brown with a covering of white powder. Six isolates were identified as a new Brunneomyces species based on morphological characteristics and combined phylogenetic analysis of partial 28S nuc rDNA region (28S), internal transcribed spacer (ITS), translation elongation factor 1-alpha (TEF1-α), and the RNA polymerase II second largest subunit (RPB2) sequence data. The Koch's postulates test confirmed Brunneomyces pennisetum, sp. nov. as a pathogen causing wilt disease in Pennisetum purpureum × P. americanum. The colony diameter of B. pennisetum, sp. nov. exhibited different sensitivity to the six fungicides. Carbendazol (50%) was demonstrated to be the most effective in slowing the growth rate of the pathogen. The pathogen exhibited a higher growth rate at pH 7.0 but could not grow when the pH was greater than 9. The pathogen growth peaked at 25 C, but it could not grow at 5, 10, and 35 C.