LAUSR

During the 2016 growing season, melon fruits were severely affected by rind necrosis and rot and nearly 80% of the fruits were unmarketable in a field in Kocarli district of Aydin. In order to determine occurrences of the fruit infections in the following year, surveys were conducted in 2017. Isolations were made from the symptomatic fruits and bacterial growths were observed consistently. In this study, we identified the causal agents of melon fruit necrosis and rot. Pathogenicity of the bacterial strains was determined on melon fruit by needle injection method and thirteen strains were further characterized with phenotypic characterization, analysis of 16S rRNA gene sequences and specific PCR assays. As a result of the pathogenicity tests, brown spots and necrosis formation was observed initially and in the later stage, inoculated fruit burst out by the fermentative strains. The oxidative strains produced limited necrosis on the rind. Fermentative bacterial agents isolated from the melon necrosis and rot were identified as Enterobacter cloacae, Klebsiella pneumoniae and Kosakonia cowanii. Enterobacter cloacae strains were further tested with tDNA-PCR using T5A/T3B primers. The oxidative bacteria were phenotypically grouped within the fluorescent pseudomonads. Homology search of the oxidative strains using the sequence information of partial 16S rRNA gene identified the strains as Pseudomonas spp. The oxidative strain 413-Si2-L2 and the reisolate 06R2K were the most similar to strains of Pseudomonas putida and P. reidholzensis including the type strains. The strain, 413-MKV-3 and the reisolate 03R2K were the most related to Pseudomonas fluorescens, P. baetica, P. syringae, and Pseudomonas sp. strains. The ability of Enterobacter cloacae, Klebsiella pneumoniae and Kosakonia cowanii to cause disease on melon fruit was shown for the first time in this study by fulfilling Koch postulate. Furthermore, although limited rind necrosis was produced, pathogenicity of the fluorescent pseudomonads on melon fruit was also confirmed.