Plant physiologist McCollum has been working on glucanases. These enzymes break down glucans, which are anti-fungal compounds found in citrus. Fungi release pectinases during the infection process. PGIP proteins inhibit pectinase production, thereby preventing the fungus from growing. Lab director Mayer says that PGIP proteins may also prove valuable in increasing resistance to insect pests.
Insects secrete pectinase when they feed.
If we can get transgenic citrus plants to express PGIP, then we have an excellent chance of producing insect-resistant plants. The West Indies sugarcane rootstalk borer weevil, Diaprepes abbreviatus, and the fungal pathogen Phytophthora parasitica are two interrelated problems for citrus growers. Diaprepes larvae feed on citrus roots, causing plant decline and death. Injured roots are more susceptible to infection by the fungi that cause foot rot. Most of the best citrus varieties are sweet oranges whose roots are highly susceptible to foot rot, so they must be grafted on more resistant rootstocks.