Identification and Characterization of Bipolaris secalis and B. setariae Associated with Brown Stripe Disease on Saccharum officinarum in Yunnan, China.

Abstract

Sugarcane (Saccharum officinarum L.) is the most important sugar crop that belongs to the Poaceae family and is mainly cultivated in tropical and subtropical regions worldwide. Brown stripe disease is a common and serious foliar fungal disease of sugarcane and has become a serious threat to sugarcane production in China. Yunnan Province is the second-largest sugar base in China. From 2022 to 2023, brown stripe-like symptoms from different sugarcane varieties were observed in Yunnan. Thirty-nine Bipolaris-like isolates were obtained from symptomatic leaves of different sugarcane varieties and characterized by means of morphological identification combined with multilocus phylogeny comprising internal transcribed spacer rDNA (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and the translation elongation factor-1α (TEF-1α) gene sequence data. The analysis provided strong support for the delineation and identification of two Bipolaris species associated with sugarcane brown stripe, including Bipolaris secalis and B. setariae. The pathogenicity test in potted sugarcane plants confirmed that these two Bipolaris species can cause brown stripe of sugarcane, thus fulfilling Koch's postulates. This study confirmed that B. secalis and B. setariae were the pathogens of brown stripe in Yunnan Province. To the best of our knowledge, this study is the first to report B. secalis as a causal agent of brown stripe of sugarcane. Collectively, this finding provides a basis for the accurate diagnosis of sugarcane brown stripe disease and would be helpful to the development of effective management strategies.