|Biles, C - EAST CENTRAL UNIVERSITY|
Submitted to: American Society for Horticultural Science
Publication Type: Abstract Only
Publication Acceptance Date: April 4, 1997
Publication Date: N/A
Technical Abstract: Phomopsis cucurbitae (latent infection) and Fusarium semitectum (non-latent infection) in cantaloupe fruit can cause severe postharvest losses and limit export possibilities. The production of polygalacturonase (PG) in vitro and in vivo by these two fungi has been investigated. When P. cucurbitae and F. semitectum were grown in autoclaved shake cultures using cantaloupe fruit tissue (mesocarp) as the carbon source, both fungi produced PG. When 40 day old fruits (horticultural maturity) were inoculated with these two fungi, P cucurbitae produced PG in decayed tissue, but PG was not detected from F. semitectum decayed tissue. P. cucurbitae produced with eight PG isozymes in shake culture using fruit tissue as the carbon source, and six PG isozymes in decayed fruit. The PIs of PG isozymes in shake culture were not the same as those produced in fruit. Only one basic isozyme was detected from shake cultures of F. semitectum. When the fruit tissue (mesocarp) from different aged melons (20, 40, and 50 days after anthesis) was subjected to partially purified P. cucurbitae PG from decayed fruit, little maceration observed on tissue from 20 and 40 day fruit. Maceration of 50 day fruit mesocarp was 13X and 4X that observed on 20 and 40 day fruit mesocarp, respectively. Once the latent infection becomes active, the PG isozymes of P. cucurbitae appear to play a major role in the decay process. However, enzymes other than PG are apparently involved in the decay process of cantaloupe fruit by F. semitectum.