Nutritional and Environmental Regulation of Pectinase Production by Post-Harvest Fungal Pathogens Associated with Sapodilla (Achras sapota L.)

Abstract

Pectinase production by post-harvest fungal pathogens associated with sapodilla (Achras sapota L.) was evaluated under selected nutritional and physicochemical conditions. Four predominant fungi were isolated from diseased fruits collected in Thane District, Maharashtra, during 2010–2011, and Aspergillus niger, Geotrichum candidum, and Rhizoctonia solani were selected for enzyme studies. Pectinase activity was determined by the viscometric method and expressed as percentage loss of viscosity. Pectin-containing medium generally supported greater enzyme production than non-substrate medium, although the response differed among fungi. Carbon, nitrogen, phosphorus, sulphur, vitamin, amino-acid, and antibiotic sources produced marked species-specific effects. Sucrose supported comparatively high activity across the three fungi, while sodium nitrate, ammonium phosphate, ammonium sulphate, urea, peptone, and gelatin produced variable responses among isolates. Calcium sulphate enhanced activity in G. candidum and R. solani, whereas aspartic acid stimulated pectinase production in all three fungi. Ampicillin reduced activity in all isolates. Incubation period, temperature, and pH also influenced enzyme production. Comparatively high activity occurred after 8–12 days of incubation, at 25–30 °C, and under mildly acidic conditions around pH 6.0–6.5, depending on the fungal species. These findings demonstrate that pectinase production by sapodilla-associated post-harvest fungi is strongly influenced by nutrient composition and physicochemical conditions, with distinct responses among fungal species.