Effect ofBacillus subtilison fruit yield and quality inActinidia deliciosaorchards infected with bacterial canker in the north of Portugal

Abstract

Bacterial canker of kiwifruit, caused by Pseudomonas syringae pv. actinidae (Psa), a disease included in the EPPO A2 List, has been registered in the north of Portugal since 2010. The relationship between the bacterium and cultural practices, namely the application of the biological control agent Bacillus subtilis in kiwifruit orchards in Portugal, is poorly understood. The most damaging phase of the disease occurs in winter and involves damage of the main vine structure and overwintering canes, and also in spring, during pollen spread, thus reducing subsequent yield and fruit quality. The main objective of this study was to evaluate the effect of B. subtilis Serenade Max ® on kiwifruit yield and quality in infected orchards of different ages. Two orchards (Actinidia deliciosa 'Hayward') with typical symptoms of Psa were selected for yield and quality assays. Thirty plants were selected from the young orchard (6 years old) and other 30 plants were selected from the old orchard (30 years old), both located in Valença, northwest Portugal. This work showed that the use of B. subtilis as a biological control agent against Psa did not affect overall kiwifruit quality, namely the longitudinal and length diameters of fruit, the total soluble solids content, firmness, pH, titratable acidity and dry matter, but contributed significantly to increased yield in the younger orchard compared with the older orchard.