Identification and Description of a New Pathogen Causing Flower Dry Rot on Passiflora edulis in China

Passiflora edulis Sims (passion fruit) is an economically important fruit crop. However, a new flower dry rot has occurred in orchards located in Zhanjiang, China, and has led to serious production loss. Its disease incidence is approximately 30 to 40%. A total of 221 isolates of Fusarium sp. were obtained from samples of three types of symptomatic flowers. Three representative single-spore isolates (PaB-1, PaB-2, and PaB-3) from each type were used for pathogenicity tests, multilocus phylogenetic analyses, and morphological descriptions. Pathogenicity tests of buds of 5-month-old P. edulis plants showed symptoms similar to those observed in nature, and Koch's postulates were achieved. By comparing 36 typical species from the FUSARIUM-ID database, multilocus phylogenetic analyses showed that the sequences of TEF1, RPB2, and ITS of these isolates belong to the Incarnatum clade of the F. incarnatum-equiseti species complex (FIESC-17-a) with an independent branch. Therefore, the pathogenic isolates were identified as F. pernambucanum (FIESC-17-a). Moreover, in this study, the conidial anastomosis tubes were first observed in the FIESC. This is the first report of flower dry rot on P. edulis caused by F. pernambucanum. Further studies should be performed to determine effective disease management strategies.