Molecular identification and phylogenetic analysis of Alternaria perpunctulata GVKNSV7 causing leaf spot disease on Alternanthera philoxeroides (Mart.) Griseb : A first report in India

Abstract

Leaf spot disease caused by Alternaria perpunctulata (E.G. Simmons) poses a significant threat to Alternanthera philoxeroides (Mart.) Griseb, commonly known as alligator weed and Ceylon Spinach, contributes to persistent weed proliferation in Indian paddy fields. This study focuses on the molecular identification and phylogenetic analysis of the Alternaria perpunctulata strain GVKNSV7, which is responsible for leaf spot disease on A. philoxeroides. Diseased plant leaves were collected from Kakumanu Mandal, Guntur, and local vegetable markets of Visakhapatnam, Andhra Pradesh, India, in December 2021, revealing symptomatic samples with pink to reddish spots on A. philoxeroides leaves. Employing a comprehensive approach that included morphological assessment, pathogenicity testing, and ITS region sequencing, the isolated fungus was conclusively identified as A. perpunctulata with a high sequence similarity of 98.54%. Molecular comparison with sequences in the NCBI database further validated this identification. The resulting genetic sequence, formally catalogued as "Alternaria perpunctulata GVKNSV7," with the GenBank accession number OQ073752, has been successfully submitted to the NCBI database. This study emphasized the utility of ITS sequencing and molecular analyses for accurately identifying and documenting emerging pathogens. Such documentation provides essential insights for developing future bioherbicides and effective weed management strategies. Furthermore, it highlights the potential use of A. philoxeroides as a leafy vegetable, contributing to food security and agricultural sustainability. Overall, this research contributes to understanding Alternaria perpunctulata and its implications for crop health and management practices.