Novel Fungal Pathogens Associated with Date Palm Leaf Spot in Egypt

Abstract

Date palms in Egypt are susceptible to leaf spot diseases caused by various fungal pathogens. The aim of this study was to identify and characterize these pathogens to understand their distribution and impact on date palm health. During 2019–2021 Leaf samples were collected at five locations for each of the five districts with infected date palms in New Valley Governorate, Egypt. The occurrence incidence and severity of disease were recorded at each location as a natural infection. Fungal isolates were identified using morphological characters and internal transcribed spacer (ITS) sequencing, yielding five genera: Alternaria, Aspergillus, Curvularia, Neoscytalidium, and Nigrospora. Pathogenicity assays were performed in both wounded and unwounded states to evaluate the virulence of each isolate. Aspergillus terreus showed the highest virulence using the unwounded method, while A. terreus and Curvularia siddiquii were the most virulent using the wounded method. A comprehensive analysis identified 22 different fungal species, including several novel reports of leaf spot pathogens on date palms: A. angustiovoidea, A. botrytis, Asp. Terreus, Cur. clavata, Cur. lunata, Cur. mebaldsii, Cur. siddiquii, Cur. specifera, Neo. novaehollandiae and Nig. lacticolonia. These findings provide valuable insights into the diversity and virulence of fungal pathogens threatening date palm health in Egypt.