Factors Influencing Bacterial Diversity in the Rhizosphere of Cucumbers and Tomatoes in the Arabian Peninsula

The Arabian Peninsula is characterized by generally hot and dry conditions. Although limited studies addressed bacterial diversity in this part of the world, there is a lack of information about bacterial diversity under farming systems. This study investigated bacterial diversity across three farms in Oman, at the South Eastern part of the Arabian Peninsula. Pyrosequencing was used to analyze bacterial communities from the rhizosphere soil of tomatoes and cucumbers grown in the farms. Results revealed that bacterial diversity is variable among various farms. Chao 1 richness and Shannon diversity estimates demonstrated that soils from the three farms differed in the levels of bacterial diversity. Proteobacteria was the major phylum in the soil samples from all farms. Gammaproteobacteria was the main and most abundant class in the rhizosphere soil of cucumber, while Gammaproteobacteria, Alphaproteobacteria, Deltaproteobacteria, Bacilli, Actinobacteria, Cytophagia and Nitrospira were common in the rhizosphere soil of tomatoes. The genera Bacillus, Nitrospira, Sphingomonas, Gemmatimonas and Pseudomonas were the most common in the rhizosphere of both crops in the three farms. Principle component analyses showed that bacterial diversity in the rhizosphere of cucumbers and tomatoes was found to be affected by the farming system but not the crop type. The study also presents information about the most common bacterial groups under farming systems in the Arabian Peninsula. Most of the bacterial taxa were saprophytic, suggesting that they play a role in cucumber and tomato growth and disease prevention.