Variation and Diversity of Microbial Populations in the Rhizosphere Soil of Tomato Plants

Abstract:

The total amount of colony forming units (CFU) of bacteria, fungi and actinomycetes in the rhizosphere and surrounding soils were investigated at four different growing stages of tomato plants using traditional plate-counting method. The amount of bacteria reached its peak value at the blossoming stage and the fruiting stage. From seedling stage to late period, actinomycete number decreased gradually with time, but fungi increased. For bacteria, the rhizosphere effect of tomato plant (R/S) was the highest at the early blossoming stage and the early fruiting stage. The variation and diversity of microbial populations in the rhizosphere soil of tomato plants were also studied using cultivation-independent analysis. DGGE profile indicated high diversity of microbial populations in the rhizosphere soil at different growth stages. The bacterial species kept stable but the population of particular species changed in different patterns. Manifest change in rhizosphere bacterial species and populations occurred at the early blossoming stage, and the most abundant bacterial species was observed at the early fruiting stage. This investigation successfully revealed the community features of the culturable and unculturable microbes in the rhizosphere soil of tomato plants, and indicated that the most abundant bacterial species occurred at the fruiting stage, suggesting this stage a suitable period for screening antagonistic bacteria.