Association and characterization of the Fusarium incarnatum–F. equiseti species complex with leaf blight and wilt of peanut in India

Abstract

Leaf blight and wilt have been observed since 2012 on peanut crops in western provinces of Rajasthan state of India, with the highest incidence of 52% at Asarlai. Leaves had water-soaking, then developed chlorosis at the tip and margins, and became brown and blighted. Later, stems became flaccid and wilted. The disease affected plants in patches and reappeared in the same areas in subsequent years. Isolates were shown to be pathogenic on peanut cultivar Girnar 2. Based on morphological and molecular characterization, the pathogen associated with leaf blight and wilt of peanut was identified as Fusarium incarnatum, the first confirmed report of F. incarnatum as pathogenic on peanut. Further, sequence analysis of TEF-1a gene, part of rpb2 gene and rDNA-ITS region of six representative isolates from peanut in areas where the disease prevails, and a search of the Fusarium-ID database showed > 98% nucleotide similarity with the Fusarium incarnatum–F. equiseti species complex (FIESC) and presence of at least two Fusarium multilocus sequence types (MLSTs). However, difficulties were observed in differentiation of species in FIESC due to indistinguishable pathogenicity and morphological characters of Jodhpur and Bikaner isolates.