Mostly when a biotic factor (in this case virus) attacks a healthy plant there is an upsurge in secondary metabolites that are either directly triggered by the attack or result in the attempt of the plant to fight the attack. Such chemicals include chitinases, glucanases, catalases etc. The changes can be studied by conducting experiments between similar varieties at the same stage of infection just before and after infection. Also PCR detection tests can be carried out to verify the causal agent.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3142377/

http://scholarsresearchlibrary.com/ABR-vol3-iss2/ABR-2012-3-2-863-870.pdf

Hi There,

There is no doubts about Biochemical changes taking place upon virus infection (see attached article as an example). I will suggest that these changes should vary depending on the infected host and the virus infecting. Your hypothesis is an interesting one and I think it has not been exploited, probably because of what I said above. Nobody can fully predicts the benefit of an hypothesis until some effort is put into it.

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