Multiple fungal diseases resistance induction in Cucumis melo through co-transformation of different pathogenesis related (PR) protein genes

Achieving multiple resistance to fungal diseases, major threat in cucurbits production, is challenging due to the quick rate of variation of fungi species and races, the lack in the knowledge of resistance genes or their complexity, and dragging undesired genes in traditional breeding. Here, we generate polygenic resistance to fusarium and powdery mildew by introducing a transgene cassette of three antifungal pathogenesis related (PR) protein genes (chitinase, glucanase and PR1) into melon (Cucumis melo L.) as a single locus. The presence of three PRs was confirmed by PCR in eight transgenic plantlets among 130 regenerants grown in selective medium. Southern blot hybridization confirmed integration of the transgene cassette in the genome of three lines. Enzyme activity assay demonstrated that chitinase and b-1,3-glucanase activity were higher in transgenic lines than in wild type plants. In-vitro and in-vivo bioassay tests showed that transgenic lines were also more resistant to fungal diseases. Finally, to evaluate the stability and heritability of the acquired resistance, selected transgenic lines were self-pollinated and T1 generation was further evaluated for disease resistance. After artificial inoculation by Fusarium oxysporum f. sp. melonis (FOM), more than 80% of wild types seedlings were infected. By contrast, on average 87% of T1 transgenic seedlings did not show disease signs. Moreover, powdery mildew infection was strongly delayed in transgenic plants.