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Effects of free and encapsulated co-culture bacteria on cotton growth and soil bacterial communities

Guo, Lina, Wu, Zhansheng, Rasool, Aamir, Li, Chun
European journal of soil biology 2012 v.53 pp. 16-22
Bacillus subtilis, Klebsiella oxytoca, antioxidants, biomass, catalase, coculture, cotton, crop yield, damping off, encapsulation, leaves, peroxidase, shoots, soil, soil bacteria, soil salinization, species diversity, superoxide dismutase
Soil salinization and cotton damping-off disease are limiting the cotton yield in the world. To overcome them, encapsulated co-culture bacteria was successfully applied. The study was carried out to evaluate the effects of free and encapsulated co-culture bacteria Klebsiella oxytoca Rs-5 and BCL-8 (mixture of Bacillus subtilis SL-13, SL-14 and SL-44) on promoting cotton growth, alleviating soil salinization stress and suppressing the growth of Rizoctonia solani. Both free and encapsulated co-culture bacteria resulted in the increase of cotton biomass, and the decrease of incidences of cotton damping-off disease, the activity of catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) of cotton leaves. Furthermore, the disease incidences of cotton plants treated with encapsulated co-culture bacteria were 20.45% lower than free co-culture bacteria. The dry weight and individual shoot length of cotton plant inoculated with encapsulated co-culture bacteria significantly increased (p < 0.05) 85.71% and 82.26%, respectively, compared to cotton damping-off disease and salinization stressed plants without bacteria. The bacterial richness of species in case of encapsulated co-culture bacteria was more than free one. At the end of the experimental period the bacterial richness of species of encapsulated co-culture bacteria treatment was similar to the soil of unstressed cotton plant due to the effect of encapsulated co-culture bacteria. Meanwhile, the varying trends of soil bacterial communities were consistent with the results of antioxidant enzymes with the same treatments. The study demonstrated that application of encapsulated co-culture bacteria could efficiently protect the cotton plants from negative stresses and promote the cotton growth in a long time via artificially regulating the soil bacterial community, without negatively affecting the bacterial richness of species in soil.