New alternative hosts of ‘Candidatus Phytoplasma australasia’ strains in the warm climate of Hormozgan province, southern Iran

Abstract

Hormozgan province in the south of Iran is one of the main regions in producing tomatoes, eggplants, bell peppers, and other vegetables as well as sesame in the winter season. In a 2021–2022 survey for phytoplasmas in different areas of this province, phytoplasma–type symptoms were observed in tomato, bell pepper, eggplant and sesame crops and many weed plants including Chenopodium album, Taraxacum officinale, Erodium cicutarium, Physalis angulata, Convolvulus virgatus, Tephrosia apollinea, and Malva sylvestris. Nested PCR assays using primers P1/P7 followed by R16mF2/R16mR1 confirmed association of phytoplasma with all symptomatic plants. 16 S rRNA nucleotide sequencing followed by virtual RFLP analysis showed that all detected phytoplasma strains from different hosts and locations belonged to 16SrII-D subgroup, ‘Candidatus Phytoplasma australasia’. The latter seemed to be the dominant phytoplasma among herbaceous plants in the region. To our knowledge, this is the first world report of natural infection of T. officinale, E. cicutarium, P. angulata, C. virgatus, T. apollinea, and M. sylvestris by a 16SrII-D phytoplasma. These plants can act as alternative hosts for transmission of the phytoplasma strains to major agricultural plants including tomato, pepper, eggplant, sesame and probably other plants.