Invasive Species Compendium

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Abstract

First report of brown apical necrosis of walnut fruit caused by Fusarium avenaceum in Hubei, China.

Abstract

Brown apical necrosis (BAN) is a serious disease complex of walnut (Juglans regia) in France, Italy, Spain, and Turkey. A total of 165 symptomatic fruits (cultivar Qingxiang) were collected periodically from Baokang County, Hubei, China, from May 2016 to 2018, and 165 fungal isolates and 104 bacterial isolates were obtained from infected fruits. Among the bacterial isolates, Pantoea agglomerans was the dominant species and accounted for 45.2% (2-year average). Among the fungal isolates, Fusarium avenaceum [Gibberella avenacea] was the dominant species and accounted for 28.7% (3-year avg.), and Alternaria spp. for 25.5% (3-year avg.) and Colletotrichum spp. for 24.1% (3-year avg.). The frequency of F. avenaceum isolation between diseased and healthy areas was higher than that from rotted areas, but the opposite was observed for Alternaria spp. and Colletotrichum spp. Two Fusarium isolates, JRBK-5 and JRBK-10, were characterized and identified as F. avenaceum based on morphological characteristics, sequence analysis of the TEF-1α and TUB2 gene, and pathogenicity test. This is thought to be the first report of F. avenaceum causing BAN disease of walnut in Hubei, China.