Acrostalagmus luteoalbus as the Novel Causing Agent of Root Rot on Strawberry and In Vitro Screening of Effective Fungicides

In November 2022, black-root and stem-rot symptoms were observed on the strawberry cultivar ‘Ssanta’ in Hohhot, Inner Mongolia Autonomous Region, China. In order to identify the causing agent of strawberry root rot, and select effective fungicides for controlling this disease, this study was carried out. The associated fungi were isolated from diseased strawberry plants, and the isolate that fulfilled Koch’s postulates was further identified based on morphological characteristics, together with the internal transcribed spacer regions and 28S rDNA sequences; then, the inhibitory activities of 11 commercial fungicides on the pathogenic strain were screened based on the mycelium growth method. Results showed that six candidate strains were isolated from diseased strawberry, and only the isolate CMGF-A caused typical root and stem rot on strawberry. The CMGF-A showed typical morphology of Acrostalagmus species, and sequence analyses revealed it as A. luteoalbus. The prochloraz was selected as the primary fungicide for effectively controlling CMGF-A, while tebuconazole, thiophanate-methyl, and difenoconazole·azoxystrobin could be used as alternatives. A. luteoalbus was previously reported to cause potato tuber disease, and red rust of needle mushroom, this work is the first report of A. luteoalbus causing strawberry root rot worldwide. This study provided helpful information for the diagnosis and management of strawberry root rot disease.