Transformation of peanut (Arachis hypogaea L.) with tobacco chitinase gene: variable response of transformants to leaf spot disease

Abstract

Fertile transgenic plants of peanut (Arachis hypogaea L.) cv. TMV-2 expressing tobacco chitinase and neomycin phosphotransferase (npt II) genes were generated using an Agrobacterium tumefaciens (LBA4404/pBI121-pBTex)-mediated transformation system. A tissue culture-independent method wherein embryo in the mature seed is inoculated and reared into single plant transformant was used for transformation. Southern blot analysis of genomic DNA isolated from T₀ transformants and progeny plants (T₁) demonstrated that the transgenes are stably integrated in the genome of transgenic peanut plants and inherited by the offspring. The expression of the heterologous chitinase gene driven by CaMV 35S promoter led to a high level of activity in some of the transgenic plants. Small-scale field tests indicated increased ability of these plants to resist the fungal pathogen Cercospora arachidicola (the causal organism of the leaf spot or Tikka disease of peanut), which is an important peanut pathogen. These results suggest that a heterologous chitinase gene was functional in peanut and expressed in healthy plants. The study also shows that peanut plants containing transgenically increased activity of chitinase were resistant to attack by the fungal pathogen C. arachidicola to different degrees. The strategy employed may be useful for the control of other fungal diseases of the crop.