Differential responses of resistant and susceptible tomato varieties to inoculation with Alternaria solani

• Differential responses of resistant and susceptible tomato to Alternaria solani were studied.
• Histochemical, biochemical and molecular parameters were used for assay of resistance.
• Comet assay showed faster rate of apoptosis in the susceptible tomato.
• A. solani was transformed using GFP constructs for detailed observation of infection.
• Differential TPK1b gene expression profile was obtained over a time course for the two varieties.

In spite of numerous studies on host pathogen interaction, very few address the differences in response in a resistance and a susceptible host. This study investigates the defense responses of resistant versus susceptible variety of tomato against the necrotrophic pathogen Alternaria solani. Various histochemical, biochemical and molecular methods were employed to compare the production and localization of phenolics, hydrogen peroxide, superoxide dismutase, polyphenol oxidases and protein cross-linking. Comet assays showed different rates of apoptosis in the hosts. A. solani transformed with green fluorescent protein gene under a constitutive promoter was used to compare progress of infection in the two varieties. The differential expression profiles of TPK1b gene were obtained over time in the two hosts. The implication of the findings, in the context of mechanism of resistance in plants, is discussed.

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