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. A new disease, flower dry rot with an incidence of 30%–40%, has occurred in orchards located in Zhanjiang, China, and led to serious production loss. Disease incidence was about 30%–-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 test, multi-locus phylogenetic analyses, and morphological description. Pathogenicity test on bud of 5- month-old P. edulis plants reproducedshowed similar symptoms as those observed in nature, and Koch’’s postulates were fulfilledachieved.Results showed that the symptoms were observed on inoculated buds but not on the control, and Koch’s postulates were satisfied in all test isolates. By comparing 36 typical species from the FUSARIUM-ID database, multi-locus phylogenetic analyses showed that the sequences of TEF1, RPB2, and ITS of thethese isolates belong to the Incarnatum clade of the F. incarnatum–-equiseti species complex (FIESC-17-a) with an independent branch. Conidia of the isolates were falcate, smooth walled, curved apical cell, and foot-shaped basal cell, 1-5-septate. The conidial anastomosis tubes were first observed in the FIESC. Therefore, the pathogenic isolates were identifieddescribed as F. pernambucanum (FIESC-17-a). Moreover, in this study, the conidial anastomosis tubes were first observed in the FIESCIt is a new pathogen causing flower dry rot on P. edulis. This study representeds the first report of flower dry rot on P. edulis caused by F. pernambucanum. Further studies should be performed for the selection of effective disease management strategies.This finding provided crucial information on the threats of F. pernambucanum affecting P. edulis in China and management strategies for the new disease, which should be developed.