Abstract

An isolate-specific restriction fragment length polymorphism (RFLP) marker previously found for the Trichoderma atroviride (formerly T. harzianum) isolate C65, an isolate with biological control activity against the kiwifruit stem-end rot pathogen Botrytis cinerea, was modified into a dot blot assay to facilitate the screening of large numbers of leaf and flower/fruit samples for the presence of C65. To increase sensitivity, the dot-blot assay was used in conjunction with a Trichoderma semi-selective medium. This modified diagnostic assay was used to track the survival and spread of C65 on kiwifruit leaves in the shadehouse and flowers/fruit in the orchard over two consecutive growing seasons in the Canterbury region of New Zealand. Results showed that isolate C65 could survive on both leaves and flowers/fruit over an entire growing season. The fungus, applied once in early summer (late November/early December) to coincide with bud burst, was detected on both leaves and fruit through to harvest in late summer (March). In addition to its ability to survive, isolate C65 was shown to spread to uninoculated leaves and fruit on the same plant and plants at least 3 m away. It is postulated that the high population of thrips present in the orchard at flowering was responsible for spread of the fungus within the orchard and that resident insects or wind currents could be responsible for spread in the shadehouse. The ability of C65 to survive and spread in the phylloplane and fructoplane of kiwifruit vines over an entire growing season makes it an ideal candidate biological control agent for reducing B. cinerea inoculum in the orchard at harvest and, consequently, post-harvest fruit rot.