| Wheat is one of the main grain crops in China, but weed in wheat fields cause serious damage to the yield and quality of wheat. How to control weed in wheat fields has become a key to wheat production. Using wheat allelopathy to control weed has the advantage of a low dosage, high selective and without"3R"problems (resistance, rampancy and residue), which will be a key technology to control weed friendly in 21st century.Wheat release allelochemicals into rhizospheric microsystem via volatilization, leaching, excretion, and decomposition. The behavior of the allelochemicals has a direct influence on the realization of the allelopathic potential. In this paper, we used wheats of different allelopathic potential at seedling stage as experimental material. Plate culture count, most probable number method,BIOLOG ECO plate and T-RFLP analysis method were applied to determined the soil microbial diversity, and soil enzyme activities in the rhizospheric soil were also determined. The results were mainly concluded as below.1. The allelopathic potential of the wheats rhizospheric soils changed after they were sterilized. The relative inhibitory rates of 115/qinghaimai and 92L89 decreased respectively by 10.8% and 13.7%, while kang10103 increased by 1.4%. It indicated that allelopathy of rhizospheric soils were related to the microbial flora in the soils.2. Allelopathic wheats enhanced the activities of Catalase, Urease, Protease, Invertase and Cellulase in its rhizospheric soils. They promoted the soil carbon cycles and phosphorus cycles in the rhizosphere, which established the foundation of allelopathic effect for wheat allelopathy. Besides, allelopathic wheat inhibited the activities of Polyphenoloxidase and Peroxidase.3. The total number and population components of rhizospheric microbial flora showed significant difference among the three wheat cultivars. Among the three major microbial species, bacterium was the predominant one, accounting for 89.52%-96.12% of the total microbial population. The following-up was actinomycete with 7%-11.3%, and the last one of fungus with only 0.06%-1% of the total microbial number. In addition, the cultivation of allelopathy wheat was likely to enhance the abundance of microbal components of Azotobacteria, Nitrate bacteria, Denitrifying bacteria, Nitrobacteria, Ammonifier, Aerobic cellulose decomposing bacteria.4. BIOLOG analysis showed that the value of Average Well Color Development (AWCD) differed significantly among wheat cultivars. It was always the highest in the rhizospheric soil of the strongly allelopathic wheat 115 /Qinghaimai and 92L89, and the lowest in the poorly allelopathic wheat Kang10103,indicated that strongly allelopathic wheat had higher utilization rate of carbon source. According to the AWCD incubated for 96h, Principal Component Analysis (PCA) identified 3 principal component factors (PCF) in relation to carbon sources, accounting for 72.05%, 18.216% and 9.733% of the variation respectively.5. We extracted DNA from the soils, combing the technology of T-RFLP, five common bacteria were found in the rhizospheric soils of 115/Qinghaimai and 92L89, and they were putative to be Bacillus, Azoarcus, Rhodococcus, Paenibacillus, Erythromonas and Blastomons rotatoria. These bacteria involved in nitrogen fixation, nutrient cycle, pestcise degradation and the rehabilitation of soil contaminated. Allelopathic wheats mostly promoted the population of bacteria, Actinomycete and azotobacteria, which enhance the adoption ability for wheat.In summary, wheat allelopathy was a trait, which was closed correlative to the function of rhizosphere microbial ecology. They were beneficial to the accumulation of allelopathic substances, promoted the soil carbon cycles and phosphorus cycles in the rhizosphere, which established the foundation of allelopathic effect for wheat allelopathy. |
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