Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/1999
Publication Date: N/A
Technical Abstract: To evaluate virulence factors of Didymella bryoniae on cantaloupe fruit, three virulent and two hypo-virulent isolates were compared for the production of cell wall-degrading enzymes polygalacturonase (PG), B- galactosidase (B-Gal), and cellulase (Cx) in vitro and in vivo. Lesion size on 10-day-old fruit averaged 7.9 cm(2) for virulent isolates, and 4.4 cm(2) for hypo-virulent isolates. PG activity in pectin shake culture ranged from 287.4 to 361.2 and 137.8 to 185.2 units/g fungal dry wt for virulent and hypo-virulent isolates, respectively. Average PG activity (units/mg protein) of virulent isolates in decayed cantaloupe fruit was 4.4 times greater than that of the two hypo-virulent isolates. Mean B-Gal activity in pectin shake culture was 50.9 and 15.5 units/g fungal dry wt for virulent and hypo-virulent isolates, respectively. Mean Cx activity of fvirulent isolates in vivo was 2.3 times higher than that of hypo-virulent isolates. Cell wall-degrading enzymes PG, B-Gal, and Cx, seem to be important virulence factors of D. bryoniae in the development of black rot of cantaloupe fruit.