RELEASE OF REDUCING SUGARS FROM CITRUS SEEDLINGS, LEAVES AND FRUITS - EFFECT OF TREATMENT WITH PECTINASE AND CELLULASE FROM ALTERNARIA AND TRICHODERMA

Three species of Citrus tree were found to be differentially infected by the fungal association known in Chile as 'fumagina'. Grapefruit trees showed a 100% presence of fumagina with 34% foliage coverage, whereas lemon and orange trees showed ca 70% presence of the fungal association with only 0.2% foliage coverage. Treatment of Citrus (orange, lemon and grapefruit) seedlings and fruits and leaves from adult trees with pectinase obtained from Alternaria chlamydospora, showed that grapefruit tissues were the most sensitive to the action of the enzyme, as determined by the amount of reducing sugars released during the treatment. Cellulase obtained from Trichoderma harzianum had no effect on intact seedlings and released ca 20-fold less reducing sugars from damaged tissues than pectinase. These results correlate well with the natural infection of Citrus by the fungal association fumagina and also supports the role of pectinases in the initiation of plant cell wall degradation.