Identification of phytopathogenic fungus causing stem rot on Opuntia ficus-indica grown in Ninh Thuan

Abstract

     Opuntia ficus-indica known as both a nutritious food source for both humans and livestock, and an ideal solution for regions affected by desertification and salinity in sandy soils along coastal areas, that were unsuitable for cultivation in Viet Nam, especially in Ninh Thuan province. In recent years, O. ficus-indica stem rot disease has emerged and rapidly spread, leading to the collapse of plants and causing many difficulties for farmers. Based on morphological characteristics and DNA sequence analysis of the internal transcribed spacer (ITS) region, the pathogenic fungi were identified as Macrophomina sp. and Lasiodiplodia theobromae. Phylogenetic analysis based on ITS region sequences showed that these two fungi were grouped into the same clade with reference isolates of Macrophomina sp. and L. theobromae from GenBank. Pathogenicity tests were performed, meeting Koch's postulates. The research results confirming the roles of both fungi in causing stem rot on O. ficus-indica, providing essential information for studying reasonable and effective disease prevention and control measures.