Diversity and Pathogenicity of <i>Phaeoacremonium</i> Species Infecting <i>Haloxylon</i> and <i>Tamarix</i> Species in Iran

ABSTRACT Tamarisk ( Tamarix spp.) and saxaul ( Haloxylon spp.) are two major plant genera in arid and semi‐arid ecosystems in Iran. During 4 years of field surveys (2018–2021), wood samples were collected from branches and trunks of tamarisk and saxaul trees showing canker and dieback symptoms across five provinces: Kerman, Sistan and Baluchestan, Yazd, Semnan and Hormozgan. Fungal isolations were made from discoloured wood tissues onto potato dextrose agar. This study aimed to identify and evaluate the pathogenicity of Phaeoacremonium isolates. Morphological characteristics along with phylogenetic analyses of β‐tubulin ( tub2 ) and actin ( act ) genes were used for the identification of the fungal isolates. Fourteen Phaeoacremonium species were identified: Phaeoacremonium alvesii , Phaeoacremonium aureum , Phaeoacremonium camporesii , Phaeoacremonium inflatipes , Phaeoacremonium iranianum , Phaeoacremonium italicum , Phaeoacremonium krajdenii , Phaeoacremonium minimum , Phaeoacremonium parasiticum , Phaeoacremonium roseum , Phaeoacremonium rubrigenum , Phaeoacremonium sicilianum , Phaeoacremonium venezuelense and Phaeoacremonium viticola . Pathogenicity tests were carried out on the branches of Tamarix aphylla and Haloxylon ammodendron under controlled and field conditions. P. parasiticum and P. rubrigenum were the most aggressive pathogens on T. aphylla and H . ammodendron , respectively. Our study is the first report of Phaeoacremonium species on tamarisk and saxaul trees worldwide. It is also the first record of P. aureum , P. roseum and P. camporesii for the mycoflora of Iran, and all three species are therefore morphologically described. Additionally, we described the anamorphic stage of P . camporesii .