Submitted to: Oklahoma Academy of Science Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 10/5/1999
Publication Date: N/A
Citation: BILES, C., BRUTON, B.D., ZHANG, J. FRUIT MATURATION AND PATHOGENESIS. OKLAHOMA ACADEMY OF SCIENCE PROCEEDINGS. 1999. V. 79. P. 104.
Technical Abstract: There are two general categories of fungal pathogens; latent and non- latent. Latent pathogens are thought to invade the fruit epidermis (exocarp) during net development; 12-15 days after pollination. The fungus remains dormant until the fruit is harvested. Subsequently, the fungus begins to cause decay which may not be discovered until the fruit reaches market. Non-latent pathogens infect the fruit at all stages of development. Phomopsis lacturonase (PG) has been found to be synthesized in fruit tissue by the latent pathogen Phomopsis cucurbitae. PG produced by the fungus appears to be inhibited until the fruit is about 40 days old. The data suggest that there may be fruit PG-inhibitors that delay the onset of the latent pathogen. Two plant defense related enzymes that have been investigated in our laboratory are peroxidase and chitobiase. Peroxidase activity peaks 30 days after pollination. HPLC anion exchange chromatography indicates that an anionic peroxidase declines in 40 and 50 day fruit when compared to 30 day fruit. The time of anionic peroxidase decline in activity corresponds to the activation of the latent pathogen Phomopsis cucurbitae. Chitobiase is an exo-chitinase that has been found throughout the cantaloupe fruit. Early in fruit development, two chitobiase isozymes were evident according to HPLCanion-exchange chromatography profiles. However, the isozyme disappears in 20 day fruit and did not reappear in later developmental stages. If these enzymes are involved, it may be possible to use genetic bioengineering to maintain or increase the level of these enzymes to inhibit fungal colonization of the fruit.