Morphological and molecular characterization of Podosphaera xanthii associated with powdery mildew of betel leaves (Piper betle L.) – a new record from India

Betel leaf (Piper betle), a medicinally and economically valuable climber, is widely cultivated in Karnataka, India. During field investigations in 2023–24, the distinctive powdery mildew signs were noted on both young and adult betel vine leaves. Estimates of the disease severity ranged from 5 to 34 %. Representative plant samples affected with powdery mildew were gathered and were identified using microscopic observations. The powdery mildew fungus was identified as a species of Podosphaera after morphological analysis. Microscopic and morphological examinations corroborated the identification. Six representative samples were chosen, and their ITS-rDNA regions were amplified and sequenced to confirm the identity. The ITS-rDNA sequence alignment was used for the phylogenetic analysis. The ITS region sequence data shared the highest degree of homology with reference sequences of Podosphaera xanthii, according to the results of the nBLAST sequence analysis. Additionally, phylogenetic study was carried out to establish the identity. Based on ITS-rDNA sequence information, phylogeny, and micro-morphological attributes, the associated pathogen was confirmed as Podosphaera xanthii. Severe infections resulted in reduced leaf yield, posing risks to betel farmers. To the best of our knowledge, this is the first time that P. xanthii has been associated with P. betle powdery mildew disease in India.