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ABSTRACTThe stolbur disease associated with “Candidatus Phytoplasma solani” (CaPsol) is very common in Europe and the Mediterranean regions and adversely affects perennial or annual plants but is rarely reported on cucurbits. We report the first multilocus genetic characterisation of CaPsol strains infecting cucurbit plants and the presence of some RNA viruses prevalent in cucurbits. Between 2019 and 2020, 156 symptomatic and nine asymptomatic plant samples were collected during surveys in cucurbit‐growing areas. Symptomatic plants exhibited leaf deformation, growth retardation, yellowing, flower deformation and other virus‐like symptoms. Molecular testing detected potyviruses, tobamoviruses and Cucumis melo endornavirus (CmEV) as single and double infections in 108 samples, but CaPsol was determined only in seven plants as a single infection. CaPsol strains infecting squash and watermelon in the Marmara region of Türkiye were genetically characterised by describing their tuf, vmp1 and stamp gene sequences. All cucurbit‐associated CaPsol strains were of the tuf‐b1 genotype and five different stamp genotypes previously reported in other crops and wild plant reservoirs in Europe. Cucurbit CaPsol strains had vmp1 gene sequences corresponding to RFLP types V4 and V14, previously detected in the Mediterranean basin. These strains were not novel cucurbit‐specific genotypes but shared similarities with genotypes from diverse plant hosts across Europe. This indicated that CaPsol is not restricted to cucurbits and may persist in alternative plant hosts. Thus, disease management should include monitoring alternative plant reservoirs, rather than focusing solely on cucurbit production areas. Viral infections showed significantly higher prevalence compared to phytoplasma infections in the region.

Introducción: La Punta Morada de la Papa (PMP) es una de las enfermedades más graves que afectan al cultivo de la papa en diversos países de América y del mundo; Candidatus Liberibacter solanacearum (CaLso) es el agente causal de esta enfermedad que en los últimos años en el Ecuador ha sido causante de importantes pérdidas económicas. El manejo de la PMP está enfocado en el control del insecto vector Bactericera cockerelli a través de la aplicación periódica de insecticidas. Sin embargo, el uso de semilla proveniente de plantas enfermas puede también ser causante de la diseminación de la enfermedad. Objetivos: este estudio complementa las investigaciones que buscan establecer el porcentaje de transmisión de la enfermedad a través del uso de tubérculos-semilla provenientes de plantas con diferente sintomatología, causadas por CaLso en el cultivo de papa variedad Superchola. Metodología: se evaluó la transmisión de CaLso mediante la siembra de tubérculos-semilla provenientes de plantas con diferente sintomatología bajo condiciones controladas. Las plantas emergidas de estas semilas, fueron monitoreadas para detectar síntomas, recolectando muestras para ser analizadas mediante pruebas PCR. Los resultados permitieron estimar el porcentaje de transmisión a partir de tubérculos-semilla. La metodología aplicada, ayudó a determinar la viabilidad del patogeno en el material vegetativo y su potencial para establecer infecciones en una nueva generación de plantas. Resultados: de esta manera se encontró que el porcentaje de transmisión fue del 11.07% cuando se utiliza como semilla a los tubérculos provenientes de plantas con síntomas severos y si se utiliza semilla libre de la enfermedad, la transmisión es del 0.06 %. Conclusiones: se logró determinar una escala fenotípica según el grado de infección de la enfermedad en plantas progenitoras. Área de estudio general: Agronomía. Área de estudio específica: Sanidad Vegetal. Tipo de artículo: original.

Sunhemp (Crotalaria juncea L.) is a tropical leguminous crop valued for its multifaceted utility in fiber production, green manuring, and as a raw material in the manufacture of paper and rope. One of the major biotic stresses affecting sunhemp is phyllody disease, caused by a phytoplasma, specifically belonging to the “Candidatus Phytoplasma” spp. These are obligate intracellular pathogens classified under the class Mollicutes, and are primarily transmitted by sap-sucking insect vectors such as leafhoppers, and psyllids. Phyllody-infected plants exhibit a range of morphological abnormalities, including malformed floral structures, chlorosis, stunted growth, and proliferation of axillary shoots, resulting in significant agronomic losses. In the present study, the sunhemp genotype NTPSH 11-02 was subjected to gamma irradiation at doses of 20 kR, 30 kR, 40 kR, and 50 kR to induce genetic variability. The M₂ generation lines derived from these treatments were evaluated under natural field conditions to assess their resistance to phyllody. Out of 44 mutant genotypes, two genotypes, NTPSH 63 and NTPSH 32 exhibited moderate resistance to phyllody, while nine genotypes—NTPSH 24, NTPSH 31, NTPSH 36, NTPSH 39, NTPSH 41, NTPSH 48, NTPSH 53, NTPSH 56, and NTPSH 60 demonstrated a tolerant reaction under natural infestation. Phyllody infection was found to negatively impact key yield-contributing traits, including plant height, number of pods per plant, and 100-seed weight (test weight). A significant reduction in these parameters was observed in infected plants compared to healthy controls, underscoring the detrimental effect of phyllody on overall productivity and crop performance.

Candidatus phytoplasma affects a wide range of host plants. In recent years, the severity and distribution of the disease have increase many fold. The present study isolated the pathogen from leaves (chlorosis), dried branches, and the other tissues of the infected tree. Acacia trees (n=15) showing severe yellowing and desiccation in the landscape areas of Şanlıurfa province were sampled from the buds (V-shaped) in three different parts of the branches, backward from the top of the branches during the flowering period, and from the middle veins of the leaves on the same branch during the leafing period. Samples were initially amplified using the universal primer pair R16F1/R16R0 and subsequently subjected to nested PCR with the primer pair R16F2n/R2. The results indicated that, on average, 2 out of 15 buds collected from the apical parts of the branches, 11 out of 15 from the middle, and 6 out of 15 from the basal parts were infected with ‘Candidatus Phytoplasma australasia’. Moreover, all samples collected from the midribs of these 15 trees were found to be infected with Ca. P. australasia.