Coconut malformation: An emerging disease caused by Fusarium proliferatum in southern Iran

Abstract

Symptoms of vegetative malformation were observed on coconut palms (Cocos nucifera L.) in the Qeshm Island, Bandar Abbas and Minab, in Hormozgan province, southern Iran. The symptoms included misshapen and dwarfed leaves with shortened, thickened and tightened leaflets in wavy and zigzag form. The aim of this study was to identify the causal pathogen of coconut palm malformation and complete Koch's postulates for putative pathogen. Small pieces of surface‐disinfested malformed vegetative tissues of coconut palms were cultured on potato dextrose agar (PDA) medium. Fusarium isolates were permanently obtained from the symptomatic tissues. Sequence data from the internal transcribed spacer region (ITS1–5.8S‐ITS2) and translation elongation factor 1 alpha (TEF‐1α) gene were used for molecular identification of the isolates. BLAST search of the sequences showed 99%–100% identity to several Fusarium proliferatum strains in the GenBank, FUSARIUM‐ID and Fusarium MLST databases. A phylogeny inferred using individual sequence data from ITS region and TEF‐1α gene placed our isolates together with the other F. proliferatum sequences retrieved from the GenBank. Pathogenicity tests were carried out using one‐year‐old healthy coconut palm seedlings and conidial suspensions (106 conidia/ml) of the F. proliferatum isolates. The first visible symptoms appeared on newly produced leaves of the inoculated seedlings during the 16th week after inoculation, wherease no disease symptoms were observed on the control plants until the end of the experiment. Reisolation from symptomatic tissues of the inoculated seedlings yielded isolates of F. proliferatum with morphological and molecular characteristics identical to those of the isolates used for inoculations. This is the first report of coconut palm malformation caused by F. proliferatum worldwide.

A Conceptual Framework for a Modern Science of Integrated Pest Management for Pests and Diseases of Coconut

“…Insect pests and diseases remain as key factors in the decline in global coconut production (Gruber et al, 2021). This has been demonstrated in the recent outbreak of coconut scale insect: Aspidiotus rigidus Reyne in the Philippines (Caoili et al, 2014); the reported newly invasive coconut rhinoceros beetle populations that threatens the Pacific Island regions (Paudel et al, 2021); the occurrence of coconut malformation caused by Fusarium proliferatum in Southern Iran (Goudarzi et al, 2019); and the association of Candidatus Phytoplasma asteris with lethal disease of coconut (Babu et al, 2020). Pest infestation and disease occurrence in coconut can be efficiently dealt with should there be a holistic integrated pest management (IPM) framework based on modern science.…”