Effects of Trichoderma harzianum applications on fresh pruning wounds in Actinidia deliciosa for the protection against pathogens associated with the “wood decay” of kiwifruit

A chronic wood wasting disease of kiwifruit (Actinidia deliciosa) has recently been identified in Italian kiwifruit vineyards. This disease is principally caused by Phaeoacremonium aleophilum and Fomitiporia mediterranea. The “wood decay” causes a reduced productivity and longevity in the vineyards and influences the quality of the final product. “Wood decay” has a high incidence throughout the vineyards, and is difficult to eradicate once present, leaving prevention as the best defence strategy. The different pathogens causing the disease infect the plant mainly through pruning wounds. We studied a commercial formulation of Trichoderma harzianum T22 for the protection of pruning wounds, and thus for the prevention and reduction of the infection. The studies were carried out on potted plants, on shoots of the year that were cut, simulating a summer pruning, and treated with a T. harzianum commercial suspension. A different morphologic reaction was observed on treated and control shoots; physiological processes connected to the reaction, such as the variation in the levels of a growth-promoting hormone (auxin) and the content of total phenols were investigated through biochemical and histological analyses. The higher levels of auxin and phenols recorded in treated shoots suggested a stimulation of T. harzianum on the wound healing processes