Investigation of trunk foaming on citrus in terms of viroid diseases

In recent years, different citrus rootstocks have started to be used in Çukurova Region, where citrus is grown intensively. In the orchards where these rootstocks were used, severe foaming symptoms were observed at the bud union points and the trees were often dried backwards. In this study, the presence of Citrus exocortis viroid (CEVd) and Citrus cachexia viroid (CCaVd) in trees showing foaming symptoms in citrus plantations grafted on rootstocks such as C35 [Poncirus trifoliata (L.) Raf. X Citrus sinensis Osb. 'Ruby'], Carrizo (C.sinensis Osb. x P.trifoliata Raf. var "Carrizo"), C22 (C.sunki × P.trifoliata) and FA5 [C.reshni Tan. x P.trifoliate (L.) Raf] in Çukurova Region were investigated. CEVd and CCaVd agents were screened by RT-PCR method by taking samples from different citrus rootstocks and cultivars showing foaming symptoms. It was determined that 17 of the 49 isolates were infected with CEVd and 14 of them were infected with CCaVd. The number of trees in which both viroid factors are infected together is 4. Blast analysis and reference genomes of CEVd and CCaVd in the NCBI gene bank were determined to have 96-99% similarity in nucleotide sequences. In addition, isolations were made from the foamy bark tissue of these trees, which show symptoms of foam disease, to investigate the status of fungal and bacterial agents. As a result of the isolations; Lasiodiplodia theobromae, Ilyonectria liriodendri, Fusarium pseudonygamai, Alternaria alternata and Streptomyces spp. were detected. As a result of the pathogenicity test made from these factors, no signs of drying or death were observed in the plants. As a result of soil analysis, it was determined that the soil structure was calcareous and the pH was 7.5 and above in the sampled gardens. It has been determined that especially trifoliate and hybrids are sensitive to high pH and therefore citrus trees may experience stress problems.