The biological control of the watermelon seedling blight and fruit blotch disease was investigated by screening the potential use of antagonistic bacteria. Between May and August 2012, totally 322 putative antagonistic bacteria were isolated from symptomless melon and watermelon plants grown in Adana, Hatay, and Osmaniye provinces of the Eastern Mediterranean Region of Turkey. In vitro dual culture tests showed that 54 out of 322 strains inhibited the Acidovorax citrulli (Ac) growth with an appearance of clear zones between 2.3 and 27.0 mm in diameter. However, the remaining 268 strains did not exhibit any antagonistic activity against Ac. Seed treatments with fourteen individual antagonistic bacteria resulted in a significant reduction in disease incidence (DI) and severity (DS) ranging between 14.06–79.47% and between 4.57–41.49%, respectively. The bacteria Pseudomonas oryzihabitans (Antg-12), Microbacterium oxydans (Antg-57), Curtobacterium flaccumfaciens (Antg-198), and Pseudomonas fluorescens (Antg-273) were the most potent antagonistic bacterial isolates which reduced DI and DS as compared to the untreated control. This study suggested the potential of bacterial antagonists Curtobacterium flaccumfaciens, Microbacterium oxydans, Pseudomonas oryzihabitans, and Pseudomonas fluorescens for the biocontrol of Ac-induced bacterial fruit blotch (BFB).

Pseudomonas is a highly diverse genus that includes species that cause disease in both plants and animals. Recently, pathogenic pseudomonads from the Pseudomonas syringae and Pseudomonas fluorescens species complexes have caused significant outbreaks in several agronomically important crops in Turkey, including tomato, citrus, artichoke and melon. We characterized 169 pathogenic Pseudomonas strains associated with recent outbreaks in Turkey via multilocus sequence analysis and whole-genome sequencing, then used comparative and evolutionary genomics to characterize putative virulence mechanisms. Most of the isolates are closely related to other plant pathogens distributed among the primary phylogroups of P. syringae , although there are significant numbers of P. fluorescens isolates, which is a species better known as a rhizosphere-inhabiting plant-growth promoter. We found that all 39 citrus blast pathogens cluster in P. syringae phylogroup 2, although strains isolated from the same host do not cluster monophyletically, with lemon, mandarin orange and sweet orange isolates all being intermixed throughout the phylogroup. In contrast, 20 tomato pith pathogens are found in two independent lineages: one in the P. syringae secondary phylogroups, and the other from the P. fluorescens species complex. These divergent pith necrosis strains lack characteristic virulence factors like the canonical tripartite type III secretion system, large effector repertoires and the ability to synthesize multiple bacterial phytotoxins, suggesting they have alternative molecular mechanisms to cause disease. These findings highlight the complex nature of host specificity among plant pathogenic pseudomonads.

No abstract

Since March, 2011, typical leaf spot symptoms were observed on parsley in several fields inspected in Hatay and Adana provinces of Turkey. Incidence of the disease was 5–15% in the regions. Symptoms were characterized as angular to irregular, initially water soaked later brown to dark black spots. Spots often limited by veins which were visible from both adaxial and abaxial sides of leaves but were not present on stems. Fluorescent bacterial colonies were consistently isolated from typical leaf spots. Biochemical tests, fatty acid methyl ester (FAME) analysis, molecular, pathogenicity tests and sequence of 16S ribosomal DNA of bacterial isolates were performed to identify possible causal disease agent. The causal disease agent was identified as Pseudomonas syringae pv. apii based on symptoms, biochemical, molecular, pathogenicity tests and sequencing. To our knowledge, this is the first report of bacterial leaf spot on parsley caused by Pseudomonas syringae pv. apii in Turkey.

Horuz S., Cetinkaya-Yildiz R., Mirik M., Aysan Y. (2014): Occurrence, isolation, and identification of Acidovorax citrulli from Melon in Turkey. Plant Protect. Sci., 50: 179-183.During February and August of 2010 and 2011, disease symptoms were detected in melon (Cucumis melo cv. Surmeli) fields and commercial nurseries in Adana and Mersin provinces (Eastern Mediterranean Region, Turkey). Lesions on leaves and fruits were observed in nearly 75 and 85 acres production areas of melon in 2010 and 2011, respectively. Initial symptoms were water-soaked irregular spots, light brown to reddish spots advancing through veins on leaves, small water-soaked lesions, greasy, dark olive green colour areas on the surfaces of melon fruit followed by brown lesions, softening, and cracks. Thirty-five non-fluorescent, slow-growing, round, cream and Gram-negative bacterial isolates were isolated from symptomatic plant materials. The pathogenicity of the isolates was proved using melon seedlings and fruits. According to classical, serological, and molecular assays, the causal organism was identified as Acidovorax citrulli. To the best of our knowledge, this is the first report and occurrence of bacterial fruit blotch disease on melon as a new host in Turkey.

No abstract

Clavibacter michiganensis subsp. michiganensis (Cmm), domateste tohum kökenli bakteriyel kanser ve solgunluk hastalığına neden olur. Bu hastalık tüm dünyada seralarda ve tarlada yetiştirilen domateslerde ciddi kayıplar oluşturmaktadır. Hastalığa karşı etkin bir mücadele yöntemi bulunmamaktadır. Bu çalışmanın amaçlarından biri ülkemizde kullanılan 41 adet ticari domates tohumlarında patojen Cmm varlığının fidede belirti izleme, tohum çalkalama suyundan King B ve SCM besi yerlerine ekim ile bakteri izolasyonu yapılarak türe spesifik ELISA ve BIO-PCR yöntemleriyle tespit etmektir. Diğer amacı ise, tohum kökenli inokulumu yok edebilecek veya azaltabilecek farklı tohum uygulamalarının etkisini belirlemektir. Bu amaçla, yapay olarak patojenle bulaşık domates tohumlarına K2C kodlu bölgesel bir antagonist bakteri, Serenade, ISR 2000, sodyum hipoklorit, üzüm sirkesi, elma sirkesi, sıcak su ve laktik asit uygulanmıştır. Tohum çalkalama suyundan yapılan ELISA testlerinde bir adet tohum partisinde (tohum partisi 13) ve SCM besi yerinde gelişen bakterilerin toplanmasıyla yapılan ELISA testlerinde iki farklı tohum partisinde (tohum partisi 6 ve 13) Cmm bulaşıklığı saptanmıştır. Yapılan çeşitli tohum uygulamaları, tohumdaki bakteri yoğunluğunu %77-100, bulaşık tohum sayısını % 31-100 oranında azaltmıştır. Sodyum hipoklorit, üzüm sirkesi, elma sirkesi, sıcak su ve laktik asit uygulamaları başarılı tohum uygulamaları olarak saptanmıştır. Çalışma ile, konvansiyonel ve organik tarım yetiştiriciliğinde patojene karşı üzüm ve/veya elma sirkesi tohum uygulamalarının kullanılabileceği sonucuna varılmıştır.

No abstract