First report of Alternaria tenuissima causing leaf blight disease on Madhuca longifolia (Mahua) seedlings in India

Forest tree diseases are often neglected because of their perennial nature and regenerative capacity. One such important tree is Madhuca longifolia, commonly known as Mahua. It is a socioeconomically important deciduous tree species found in India. 12-month-old seedlings showed severe leaf spot and blight symptoms, with 45–70 % disease severity in Ahmadpur Nursery, Bhopal, Madhya Pradesh, during a disease survey in December 2023 and June 2024. Leaf blight disease was extensive, leading to premature defoliation and seedling death in the nursery. The pathogen was isolated and identified as Alternaria tenuissima using a morpho-molecular approach. Multigene sequence analysis of three housekeeping genes, Internal Transcribed Spacer (ITS), Translation Elongation Factor 1-alpha (tef-1α), and major allergen (Alt a1) gene confirmed the identity of the pathogen at the species level. Pathogenicity was established using Koch's postulates, and partial sequences were submitted to NCBI GenBank. Phylogenetic analysis of the concatenated sequences of the three genes revealed a close association between isolate MA1 and the NCBI reference genome of A. tenuissima strain JgmB 36–2. These findings highlight the importance of early detection and management to prevent the spread of this pathogen in forest nurseries and plantations. This is the first report of Mahua leaf blight caused by A. tenuisima in India.