Comparative expression profile of selected genes in Venturia inaequalis Cooke (Wint.) infecting apple fruits and leaves

Scab is a noxious fungal disease of apples (Malus domestica Borkh) in all apple producing regions caused by a host-specific phytopathogen Venturia inaequalis Cooke (Wint.). Its symptoms include black or brown lesions on leaves as well as on fruits, and causes fruit deformation. In this study, V. inaequalis was isolated from infected fruit samples and expression level of selected pathogenesis related genes in scab infected fruits and leaves was studied. The isolated fungus formed a brown coloured mat-like colony having septate mycelium and produced acute ovoid shaped conidia. Molecular characterization of the fungus was done by amplification and sequencing of internal transcribed spacer (ITS) and Cytochrome (CYP51A1) regions of the isolate. The Sanger sequencing of amplicons and sequence analysis using BLAST tool of the NCBI against GenBank database confirmed that the obtained sequence of ITS and CYP51A1 regions had 99.6 % and 98 % sequence identity with the reference V. inaequalis, respectively. The isolated strain of V. inaequalis was submitted in the fungal repository of Microbial Type Culture Collection (MTCC), India. The phylogenetic analysis of ITS region of the isolate revealed that the isolated strain of V. inaequalis was more closely related to Fusicladium eriobotryae compared to other Venturia species. The expression levels of pathogenesis related genes viz. CIN1, CE5 and VICE16 were higher in infected leaves as compared to infected fruits. Whereas expression of VICE12 and GH28 were higher in infected fruits compared to infected leaves. VICE4 gene showed equal level of expression during infection in both fruits and leaves, which was also maximum as compared to the control treatment. The transcript analysis of aforementioned genes of V. inaequalis gives the insights of the pathogen's expression profile during pathogenesis in fruits and leaves. This expression analysis can form a basis selecting pathogenesis related genes as targets for developing dsRNA expressing constructs with an aim to reduce RNAi mediated silencing of specific genes, in a futuristic biotechnological based solution to deal with apple scab disease.