Multi-Gene Phylogenetic Approach for Identification and Diversity Analysis of Bipolaris maydis and Curvularia lunata Isolates Causing Foliar Blight of Zea mays

Abstract

<i>Bipolaris</i> species are known to be important plant pathogens that commonly cause leaf spot, root rot, and seedling blight in a wide range of hosts worldwide. In 2017, complex symptomatic cases of maydis leaf blight (caused by <i>Bipolaris maydis</i>) and maize leaf spot (caused by <i>Curvularia lunata</i>) have become increasingly significant in the main maize-growing regions of India. A total of 186 samples of maydis leaf blight and 129 maize leaf spot samples were collected, in 2017, from 20 sampling sites in the main maize-growing regions of India to explore the diversity and identity of this pathogenic causal agent. A total of 77 <i>Bipolaris maydis</i> isolates and 74 <i>Curvularia lunata</i> isolates were screened based on morphological and molecular characterization and phylogenetic analysis based on ribosomal markers-nuclear ribosomal DNA (rDNA) internal transcribed spacer (ITS) region, 28S nuclear ribosomal large subunit rRNA gene (LSU), D1/D2 domain of large-subunit (LSU) ribosomal DNA (rDNA), and protein-coding gene-glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Due to a dearth of molecular data from ex-type cultures, the use of few gene regions for species resolution, and overlapping morphological features, species recognition in <i>Bipolaris</i> has proven difficult. The present study used the multi-gene phylogenetic approach for proper identification and diversity of geographically distributed <i>B</i>. <i>maydis</i> and <i>C</i>. <i>lunata</i> isolates in Indian settings and provides useful insight into and explanation of its quantitative findings.