First report of a ‘Candidatus Phytoplasma asteris‘‐related strain (16SrI‐B) associated with Sonchus oleraceus (common sowthistle) phyllody disease in Iran

Abstract

Common sowthistle (Sonchus oleraceus) is a major weed problem in Iran and is also used for medicinal purposes. During 2012-2015 surveys of Fars and Yazd provinces (Iran) for phytoplasma diseases, a phyllody disease was observed in S. oleraceus plants growing as weeds within and/or in the surroundings of fields and orchards. The main symptoms of the disease were yellowing and reddening of leaves, shortened internodes, flower virescence, phyllody, proliferation and witches' broom ( Fig. 1).Total DNA was extracted from 0.2 g of leaf midribs of eight symptomatic (four plants per province) and four symptomless (collected in Fars province) S. oleraceus plants using the CTAB method of Zhang et al. (1998). DNA samples were tested for phytoplasma presence by a nested PCR assay primed by primer pairs P1/P7 followed by R16F2n/R16R2 (Lee et al., 1998). Amplicons of~1.25 kb were obtained in the nested round from all eight diseased plants but not from the four symptomless plants. Eight nested amplicons were separately cloned and sequenced. The obtained sequences were identical and a consensus sequence corresponding to the Abarkooh (Yazd Province, Iran) S. oleraceus phyllody phytoplasma was deposited in GenBank (Accession No. MG652627). The S. oleraceus phyllody phytoplasma strain had 99.78% sequence identity with the 'Ca. P. asteris' reference strain (M30790). A BLAST search showed that this sequence had maximum identity (99-100%) with members of the 16SrI subgroup B. Phylogenetic analysis using the neighbour-joining method (MEGA7) (Fig. 2) showed that the Abarkooh S. oleraceus phyllody phytoplasma was clustered within the 16SrI group closest to onion yellows phytoplasma (NC_005303), representative of subgroup 16SrI-B.A 16SrI-A phytoplasma has been previously reported in S. oleraceus in Canada (Khadhair et al., 2008), however to our knowledge this is the first report of a 16SrI-B phytoplasma associated with S. oleraceus phyllody disease. The occurrence of 16SrI-B phytoplasma strains were previously reported in Iran on Brassica napus (Salehi et al., 2011), Eruca sativa (Esmailzadeh Hosseini et al., 2017) and Eucalyptus camaldulensis (Salehi et al., 2016); S. oleraceus may act as a reservoir host. References

Journal of Plant Protection Research

“…In spite of several reports about the presence of aster yellows phytoplasmas (16SrI) in Iran (Babaie et al 2007;Asghari Tazehkand et al 2010;Rashidi et al 2010;Esmailzadeh Hosseini et al 2015a, b, c;Salehi et al 2016Salehi et al , 2018 this is the first phytoplasma affiliated to the 16SrI-R subgroup in the country. This creates a greater awareness of the diversity of phytoplasmas in Iran.…”

Identification of phytoplasma strains associated with witches’ broom and yellowing in Ziziphus jujube nurseries in Iran

“…Phytoplasma groups 16SrI and 16SrVI have broad host plant ranges (Lee et al, 2004;Hiruki et al, 2004), and have also been reported from numerous and different plant hosts in Iran (Babaie et al, 2007;Salehi et al, 2016;2018;Asghari Tazehkand et al, 2010;Rashidi et al, 2010;Esmailzadeh Hosseini et al, 2015, 2017aFattahi et al, 2016). This indicates that various reservoir host plants besides jujube nurseries are likely to be present.…”

“Candidatus Phytoplasma solani” associated with Eucalyptus witches’ broom in Iran

“…Although three different phytoplasma groups including 16SrI, 16SrII and 16SrV (Marcone et al., ; Neves de Souza et al., ; Salehi et al., ) have been reported from Eucalyptus spp., no difference in the disease symptoms has been described. This confirms that different phytoplasmas may induce identical symptoms in a given plant species (Marcone et al., ).…”

“…Sensitive and accurate detection of phytoplasmas is a prerequisite for the management of their associated diseases. The group 16SrI phytoplasma was previously recorded in E. camaldulensis in eastern Fars, Iran (Salehi, Esmailzadeh Hosseini, & Salehi, ). Based on observed symptoms, the presence of a phytoplasma was suspected during surveys on the E. camaldulensis plant species in western Fars and the Khozestan province in Iran.…”