Investigation of molecular diagnosis and control of Acidovorax citrulli the causal agent of bacterial fruit blotch of watermelon by endophytic bacteria

The aim of this thesis was to evaluate the effect of endophytic bacterial (EB) strains on bacterial fruit blotch of watermelon caused by Acidovorax citrulli (Ac), and to realize molecular identification of Ac. Out of 20 EB isolates, which were isolated from internal tissues of healthy cucumber plants, were screened for in vivo antagonistic activity against Ac. Watermelon seeds, which were previously inoculated with Ac suspension by vacuum infiltration technique were treated by EB suspensions. Copper oxychloride and mancozeb were used as reference chemicals. Treated watermelon seeds were sown in peat medium and kept in growth chamber room, and then evaluated for seedling emergence and disease symptoms on cotyledone leaves. According to in vivo test results, more than 50% of tested EB isolates inhibited the disease development on cotyledons of seedlings at the rate of 64 to 85% compared to pathogen alone treatment, and found more effective than tested chemicals. It was also determined that the possible mode of action of EB strains to Ac was based on competition for Fe 3+. The most effective EB strains were identified as Pseudomonas fluorescens (strain 31), P. lutea (strain 53), P. putida (strain 61), Enterobacter cloaceae (strain 108), Chryseobacterium elymi (strain 88), Cronobacter sakazakii (strain 15) and Serratia ureilytica (strain 18) by using 16s rRNA primers and sequence analysis.