Influence of transgenic ath-miR399d tomato lines on microbial community and diversity in rhizosphere soil

Abstract

Transgenic ath-miR399d tomatoes (Solanum lycopersicum L. cv Zhongshu No. 4) have enhanced phosphorus (P) uptake and accumulation in shoots, and have the potential to improve P-use efficiency in agricultural soils. However, the effects of transgenic ath-miR399d tomatoes on soil microbial community and diversity are poorly understood. Soil carbon source utilization patterns and phospholipid fatty acid (PLFA) profiles were evaluated after a 35-d cultivation of transgenic tomato lines C1 and C2 and wild-type tomato at 0, 150 and 300 mg phosphorus pentoxide (P2O5) kg−1 soil. Microbial diversity indices deduced from carbon source utilization patterns were significantly decreased after cultivating transgenic tomato lines compared to wild-type tomato. So were the average well color development (AWCD) for general carbon sources, carbohydrates and amino acids. The AWCD for general carbon sources was increased with P levels, while the microbial diversity indices did not differ significantly among three P levels. The amounts of total, bacterial and Gram-positive bacterial PLFA significantly declined after cultivating transgenic tomato lines. So were Gram-negative bacterial PLFA at 0 and 150 mg P2O5 kg−1 soil. In contrast, the numbers of individual PLFA, the PLFA ratio of fungi:bacteria and Gram-positive bacteria:Gram-negative bacteria were not significantly affected by genotype or P level after the 35-d cultivation of transgenic tomato lines. Principal component analysis (PCA) for both substrate utilization patterns and PLFA profiles showed good separation of soil microbial communities between the transgenic tomato lines and wild-type tomato. Our results suggest that transgenic ath-miR399d tomatoes have transient adverse effects on microbial community and diversity in rhizosphere soil.