Isolation, spore production and Koch's postulates of elsinoe pyri

Abstract

Elsinoe leaf and fruit spot is a minor disease of apple and pear. Very little is known of the biology and life cycle of the causal agent Elsinoe pyri. The fungus was isolated from spots on apple fruit, and grew very slowly on potato dextrose agar (PDA). The conditions needed for spore production were examined using different culturing media, plating techniques and culture ages. When small pieces of a 2- to 6-week-old culture from PDA were sub-cultured onto corn meal agar for 2 days, viable conidia were produced. Conidial germination occurred between 10°C and 26°C, with the highest germination percentage at 20°C and 26°C, and greatest germination tube elongation at 20°C. At least 200 conidia per leaf were required to infect 'Royal Gala' leaves. Typical elsinoe spots were visible 6 weeks after inoculation. Four months after inoculation, conidia from the spots were re-isolated onto PDA and grew into typical colonies of E. pyri. © 2013 New Zealand Plant Protection Society.