AbstractCassava witches’ broom CWB disease is associated with the presence of phytoplasmas. Typical symptoms include witches’ broom, shoot proliferation, short internodes and stunting. Severely infected plants decline, resulting in yield losses of up to 80%. CWB has been reported in several cassava growing regions in Thailand. In total, 25 CWB symptomatic cassava plant samples were collected from 9 plots in Kanchanaburi Province in November 2023. Detection of CWB phytoplasma was carried out using nested PCR assay to amplify the 16S rRNA gene using primers P1/P7, followed by R16F2n/R16R2. A target DNA fragment of approximately 1,800 bp was obtained by PCR in 15 samples, and a 1,200 bp fragment from nested PCR was obtained in 24 samples. Sample KRI-M-4 (GenBank accession number PQ333137) was used for molecular identification. It showed 98.65% identity with the reference strain ‘Candidatus Phytoplasma solani’ (GenBank accession number AF248959). BLAST analysis in the GenBank, NCBI database showed 99.07% similarity to a ‘Ca. P. solani’ strain from Japan (GenBank accession number LC460259). The partial stamp gene of KRI-M-4 strain was cloned, sequenced, and analyzed in the GenBank, NCBI database showing 100% identity to a ‘Ca. P. solani’ strain from Thailand (GenBank accession number MW464308). Phylogenetic tree analysis and a heatmap of pairwise distance analysis of the 16S rDNA sequences and partial stamp gene sequences confirmed that the KRI-M-4 strain clustered with phytoplasmas in the 16SrXII group. This is the first report of the presence of a ‘Ca. P. solani’ strain associated with CWB disease, in plants exhibiting witches’ broom, yellow leaf, and short internode symptoms in Thailand.
AbstractGrapevine yellows (GY) is a destructive phytoplasma disease complex in viticultural regions worldwide, mainly associated with the presence of ‘Candidatus Phytoplasma solani’ (“bois noir”, 16SrXII-A) and 16SrV group phytoplasmas (“flavescence doree”). Field surveys in 2021-2022 in Hatay and Kahramanmaras (Türkiye) investigated phytoplasma occurrence in grapevines, weeds, and insect vectors. Typical GY symptoms were observed in grapevine and bindweed (Convolvulus arvensis). ‘Ca. P. solani’ was detected in one grapevine and one bindweed plants among the 25 grapevine and 19 bindweed samples tested by PCR and sequencing analysis. Among the 3,086 leafhoppers (28 species), 12 individuals from six species were positive for phytoplasmas, with the highest infection rates in Psammotettix provincialis, Empoasca sp. and Balclutha hebe. Sequencing confirmed ‘Ca. P. solani’ presence in three insect species, grapevine, and bindweed, while ‘Ca. P. mali’ (apple proliferation phytoplasma, 16SrX-A) was detected in six leafhopper individuals. These results provide the first molecular evidence of ‘Ca. P. solani’ and ‘Ca. P. mali’ in leafhoppers collected from vineyards in Türkiye and highlight the possible epidemiological role of diverse leafhopper species in GY spread.
AbstractBesides viral diseases, phytoplasma-associated diseases pose a significant threat to okra cultivation in India. During 2022-2025 seasons, okra plants exhibiting characteristic phytoplasma symptoms such as little leaf, shoot proliferation, bud proliferation and bunchy crown were observed in Kerala, New Delhi and Tripura states of India. Molecular detection using phytoplasma-specific primers P1/Tint and R16F2n/R16R2 amplified DNA fragments of about 1.25 kb of the 16S rRNA gene from symptomatic okra leaf samples, while asymptomatic samples showed no amplifications. Pairwise sequence analysis of the 16S rRNA gene revealed almost 100% identity among the okra phytoplasma strains in the study and ‘Candidatus Phytoplasma asteris’ strains. Phylogenetic analysis further clustered these okra phytoplasma strains with ‘Ca. P. asteris’ strains. In silico RFLP analysis employing 17 restriction endonucleases confirmed the affiliation of the okra phytoplasma strains within the 16SrI-B subgroup, with a similarity coefficient of 1.00. Although the ‘Ca. P. asteris’ has been reported earlier in India, the present study highlights the prevalence and importance of ‘Ca. P. asteris’ strains occurrence in okra crops across three Indian states, underscoring their epidemiological importance.
