Cucumis melo L. is a widely cultivated horticultural crop for its delicious fruits. Melon crop is highly susceptible to various fungal diseases. Powdery mildew is one of the common fungal diseases that severely affects the plant growth thereby compromises the fruit yield and quality. Currently applying chemical fungicides by farmers poses serious threat to human health in the long-term use and also impacts the soil quality as well as leads to adaptation of the causative agent, Podosphaera xanthii into fungicide resistant variants. Therefore, at present, numerous studies are being conducted worldwide to develop the melon cultivars resistant to fungal diseases by the use of various resistance breeding approaches as well as stimulating the plant innate immune response pathways. In order to target the plant’s innate immunity, prior knowledge on functions of such disease resistance proteins is paramount. Therefore, in this study, here we analyzed the known powdery mildew resistance protein sequence from wheat in order to predict the putative disease resistance candidate protein encoded by C. melo genome. We predicted a putative disease resistance protein available in NCBI GenBank database as a putative powdery mildew disease resistance protein based on its sequence similarity to the characterized powdery mildew resistance protein from wheat. We performed its phylogenetic and sequence analysis in relation to the homologous disease resistance proteins from other members of the Cucurbitaceae family and found its evolutionary relationship and high conservation. In addition, its homology model built with the SWISSMODEL program revealed the presence of a protein fold called Leucine-Rich Repeat (LRR), which is a signature property of proteins conferring innate immunity in plants. Altogether, this study provides valuable insights into the understanding of the conservation of powdery mildew resistance proteins in

melon and would help future studies aimed at exploration of the powdery mildew disease resistance mechanisms in melon.

Highlights

• A putative disease resistance protein from Cucumis melo L. is predicted to be mediating resistance to powdery mildew.
• Phylogenetic and sequence analysis revealed its conservation and 3D structure model confirmed its role in the plant immune system.