Morphological and molecular studies of a rare mucoralean species causing flower rot in Hylocereus polyrhizus

Abstract

The order Mucorales typically includes fast-growing saprotrophic and plant pathogenic fungi. Flower rot of red-fleshed dragon fruit (Hylocereus polyrhizus) caused by Mucor-like fungi was observed in a field in Phatthalung province, southern Thailand. Agglomeration of sporangiophores and sporangia on the wet rotten tissues of the red-fleshed dragon fruit flower was detected. Fungal isolates obtained from symptomatic tissues were cultured on potato dextrose agar for macroscopic and microscopic observations. Based on the growth rate and morphology of sporangia and sporangiospores, the fungus was identified as Gilbertella persicaria, which was further confirmed using phylogenetic analyses of the internal transcribed spacer and nuclear large subunit ribosomal DNA sequences. Pathogenicity tests revealed that the fungal isolate G. persicaria caused flower rot, similar to that observed in the field. This study is the first report of flower rot disease in H. polyrhizus caused by G. persicaria in Thailand.