Traditional pathology and phylogenetic networking confirm the pathogen causing date palm wilt

Phoenix dactylifera L. (Date palm) is one of the leading perennial fruit crops regarding its nutritional profile, medicinal significance, excellent yields, long life, and high adaptability to diverse climatic conditions of semi-arid and arid regions globally. Eleven major palm-growing districts of Punjab, Sindh, and Khyber Pakhtunkhwa were surveyed for wilt disease assessment on date palms. The date palm plantation was highly affected with Fusarium wilt diseases with 55%, the incidence in Khairpur (Sindh province), followed by Bahawalpur at 47.4% (Punjab Province) and 45% in Dera Ismail Khan (KPK province). Disease severity was recorded as 65% in Khairpur, 55% in Bahawalpur, and 50% in Dera Ismail Khan (Sindh, Punjab, and KPK, respectively). Sixty-three Fusarium isolates were obtained from three hundred and eighty (380) diseased samples, and thirty isolates randomly selected out of 63 were studied for morpho-cultural and microscopic characterization. Morpho-cultural characters, i.e., colony pigmentation, growth pattern, conidia (macro and microconidia), shape, apical cell shape, and phalidies studied, coinciding with typical characteristics of Fusarium oxysporum. Twenty isolates of the Fusarium population were subjected to the ITS region sequence data-based phylogenetic network. The Neighbor net algorithm computed an unrooted phylogenetic network displayed as four branched genetic network that depicted the division of twenty fungal isolates into four groups. F. oxysporum (FMB-FO-PD-011) inoculated onto healthy symptomless detached date palm leaves, seedlings, and suckers under controlled and field conditions showed typical wilt disease symptoms. Hence this study proved that F. oxysporum is the potential cause of date palm wilt in Pakistan.