P-399 - Identification of fungal pathogens associated with kiwifruit cordon canker and dieback in California

California is the primary kiwifruit (Actinidia chinensis) producer in the United States, representing approximately 98% of the national output. Trunk diseases are major constraints on kiwifruit production in top-producing countries; however, their incidence, etiology and impact in California remain unclear. Since 2019, trunk disease symptoms have been observed in mature ‘Hayward’ and gold kiwifruit vineyards located in Yuba and Butte counties, with incidences ranging from 5 to 50%. Affected vines exhibited stunted or absent growth on cordons and canes, dieback, and wedge-shaped cankers often associated with white rot. In severe cases, cankers extended across the trunk, reaching the rootstock. Isolations from symptomatic samples (n = 48) collected from seven vineyards revealed multiple trunk disease pathogens. Diaporthe spp. were the most prevalent, followed by Neofusicoccum and Phaeoacremonium spp. Basidiomycetes and soil-borne pathogenic fungi were less frequently isolated from the crown of vines with advanced symptoms. Multi-locus phylogenetic analyses of rDNA ITS, tub2, and tef1 genes allowed the identification of Diaporthe ambigua (n = 12), D. eres (n = 4), D. australafricana (n = 2), D. chamaeropis (n = 1), D. rudis (n = 1), Neofusicoccum parvum (n = 13), N. mediterraneum (n = 4), Phaeoacremonium parasiticum (n = 3), P. rubrigenum (n = 2), and P. minimum (n = 1). Currently, we are investigating the pathogenicity and epidemiology of these fungal species to develop potential management strategies.