Characterization and pathogenicity of fungi and oomycetes associated with root diseases of date palms in Oman

Date palm is the most important crop in Oman and the Arabian Peninsula. A study was conducted to investigate fungal and oomycete pathogens associated with root diseases of date palms in Oman. Isolations were done from date palm roots showing root rot/necrosis symptoms. The root samples were collected from 111 date palm trees representing 29 different date palm cultivars. Morphological and molecular identification of the isolated fungi and oomycetes showed that they belong to 34 different fungal and oomycete species. . Fusarium solani (27%), . Ceratocystis radicicola (25%) and . Lasiodiplodia theobromae (19%) were found to be the most common pathogens associated with root diseases of date palms. Pathogenicity tests on seedlings of date palm cv. Khalas showed that 21 fungal and oomycete species are pathogenic on date palm seedlings. The pathogenic species produced root rot, root necrosis or wilt symptoms upon inoculation on date palm seedlings. A total of 1, 7, 13 and 10 fungal and oomycete pathogens were found to be aggressive, moderately aggressive, weak and non-pathogenic on date palm seedlings, respectively, with . C. radicicola being the most aggressive. Among the 21 pathogenic species, 13 are reported in this study for the first time as new root pathogens of date palm on a global basis. These include . Ceratocystis omanensis, . Cochliobolus hawaiiensis, . Exserohilum rostratum, . Corynascus kuwaitiensis, . Fusarium brachygibbosum, . Fusarium acuminatum, . Fusarium redolens, . Fusarium thapsinum, . Nigrospora sphaerica, . Phoma multirostrata, . Pythium indigoferae, . Pythium spinosum and . Pythium ultimum var. . ultimum. In addition, this study reports for the first time the occurrence of 22 fungal and oomycete species in Oman.