Güldür, Mehmet Ertuğrul

AbstractPistachio (Pistacia vera L.) is a vital crop for Türkiye's economy, occupying over 420 000 ha, primarily in south‐eastern Anatolia. In 2023, severe symptoms, such as curling, chlorosis and needle‐like leaf deformation, were observed on pistachio trees in Şanlıurfa Province. This prompted a molecular study of phytoplasma pathogens. A real‐time PCR targeting the 16SrDNA gene was used to analyse DNA from eight symptomatic and two asymptomatic trees. A phytoplasma was found in two symptomatic samples but not in asymptomatic controls. Positive samples were further analysed using nested PCR. One sequence with 99% identity to ‘Candidatus Phytoplasma trifolii’ (16SrVI‐A subgroup) was found by bidirectional sequencing of PCR products. The identification of the phytoplasma was confirmed by a phylogenetic analysis showing the clustering of the UP 1 isolate with ‘Ca. Phytoplasma trifolii’ reference strain and by a virtual RFLP analysis using 17 restrictions enzymes. This first report of ‘Ca. Phytoplasma trifolii’ in pistachio in Türkiye highlights the presence of this phytoplasma in a key agricultural sector. Although no yield losses have been observed to date, broader surveys and monitoring of leafhopper vectors are necessary to assess the potential risk and implement timely management strategies.

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.

AbstractIncreasing incidences of phytoplasma infestations in Almond trees warrants the better management approach to prevent yield losses. Disease management rely on identification of the pathogen based on molecular profiling. The present study aimed, to identify the phytoplasma agent in almond trees and to measure the biochemical responses it causes in the host. Direct and Nested PCRs performed using phytoplasma specific primer pairs 16S rRNA, detected the presence of phytoplasma agent in symptomatic trees but not in symptomless trees. Phylogeny based on the sequence analysis revealed that the infecting agent was closely related to ‘Candidatus Phytoplasma phoenicium’ (16SrIX‐B subgroup). Then the study was carried out to determine the responses of physiological and biochemical mechanisms in almond trees infected with phytoplasma. Total chlorophyll and protein contents of infected almond trees were lower compared to healthy control, on the other hand, the levels of catalase and peroxidase activity increased in infected trees. Higher levels of stress‐related metabolites such as proline (20.53–39.23 μmol/g), phenol (3.00–4.44 mg GAE/g), salicylic (94.96–138.22 ng SA/mg protein) and jasmonic acid (965.86–1465.10 ng JA/mg protein) were observed in infected trees compared to asymptomatic trees, respectively in healthy and infected trees. The results showed that the Ca. P. phoenicium, which was detected for the first time in Türkiye, was able to change the physiological and biochemical mechanisms. The pathogenic agent could possess a potential danger in almond production areas. It is crucially important that this agent should be considered in certification programs.