Induction of antimicrobial substances
Phytoalexins are antimicrobial substances produced by plants in response to pathogen. They accumulate at the site of infection. For example, when soya bean (Glycine mar) is infected by the fungus Phytophthora megasperma the chemical phytoalexin glyceollin is accumulated in the plant. Glucan extracted from fungal cell wall can also induce the synthesis of glyceollin. Such a substance which can cause a response in target cells similar to that caused by pathogen is called an elicitor. If phytoalexin can be produced in plants by artificial gene transfer, it would probably be possible to have disease resistant crops.