Expression of Tcchitinase-I gene in transgenic peanut (Arachis hypogaea L.) confers enhanced resistance against leaf spot and rust diseases

The disease-resistant transgenic peanut cv ICG 13942 plants were developed by using Tcchitinase-I gene. Agrobacterium tumefaciens strain LBA4404 harboring the binary vector (pBinAR) contains the chitinase (Tcchitinase-I) gene and neomycin phosphotransferase resistance (nptII) gene. The transformed shoots were developed on selection medium (MMS + 0.5 mg/L IAA + 15 mg/L TDZ + 100 mg/L Kan + 250 mg/L Cefotaxime) from deembryonated cotyledon (DC) explants. Established plantlets were screened for the presence of Tcchitinase-I and nptII genes. Stable integration and expression of the transgenes (T0) were confirmed by using PCR, RT-PCR and Southern blot analyses. The transformation frequency 63.34% was recorded. All the transformed (T0) plants were found normal, flowered and set seeds. After selfing the T0 plants, a Mendelian inheritance pattern (3:1) for the transgene in T1 progeny is revealed. T1 transgenic peanut plants were evaluated for resistance against Cercospora arachidicola, C. personatum and Puccinia arachidis by infection with the microspores using detached leaf assay. These T1 plants have shown longer incubation, latent period and lower infection frequencies in comparison to non-transformed (WT) plants. The Tcchitinase-I gene expression in resistant transgenic plants was compared to that of a susceptible control. A significant negative correlation was recorded between chitinase activity and the frequency of infection to the three tested disease causing agents.