69 Strawberry Breeding for Resistance to Verticillium Wilt M. Amenduni, C. Colella, M. D’Amico, G. Bubici and M. Cirulli University of Bari, Department of Biology and Plant Pathology via Amendola 165/A, 70126 Bari, Italy Keywords: Verticillium dahliae, Verticillium albo-atrum, Fragaria x ananassa Abstract Evaluation of resistance/susceptibility to Verticillium wilt of strawberry germplasm obtained during a 20 year breeding program supported by the Italian Ministry of Agriculture was made. An improved method for screening strawberry resistance to Verticillium was also set up. The results of this research activity have contributed to the enlargement of Verticillium wilt resistance background in the newly produced strawberry breeding material and the release of new strawberry cultivars possessing high levels of resistance to Verticillium dahliae. INTRODUCTION Verticillium wilt is a serious disease of strawberry that causes severe loss of yield.The disease, incited by Verticillium dahliae Kleb. and less frequently by V. albo-atrum Reinke and Berth., has been known since 1931 (Thomas, 1931). In the early decades of the last century lack of effective control measures stimulated research on resistance to Verticillium wilt in strawberry and in the years up to about 1950 cultivars such as ‘Sierra’, ‘Blackmore’, ‘Catskill’, ‘Talisman’, ‘Wiltguard’, ‘Marshall’, ‘Sparkle’, ‘Redglow’, ‘Alpine’ and ‘Guardian’ were developed. These cultivars possess variable levels of resistance to wilt. Starting from about 1960 the extensive use of soil fumigation (methyl bromide) caused a pause in the production of new cultivars possessing resistance to Verticillium wilt. A strawberry breeding programme supported by the Italian Ministry of Agriculture (MiPAF) was started two decades ago and included among its aims the release of new cultivars with multiple disease resistance. Within this programme, named “Frutticoltura” Project, we evaluated the resistance/susceptibility to Verticillium wilt of strawberry germplasm originated from a large number of crosses made between cultivars and breeding material. MATERIALS AND METHODS Evaluations of resistance/susceptibility to Verticillium wilt of strawberry germplasm were carried out in a greenhouse conditioned at a temperature of 25 ± 2 °C. Strawberries tested included old cultivars, known for their resistance to Verticillium wilt, and several hundreds of clones derived from numerous controlled crosses made by partners participating to the MiPAF project. An improved method of plant inoculation including two inoculation interventions was used (Table 1). Disease symptoms included leaf yellowing, wilting, necrosis and plant stunting. Disease severity was assessed on the base of a scale ranging from 0 (healthy plant) to 4 (severely affected or dead plant). Disease records were taken seven months after the second inoculation, when Verticillium wilt occurred on 100% in susceptible strawberry check cultivar (Cirulli and Amenduni, 1996).