Effect of Jhum Cycles on Acidobacteria and Burkholderia Community in the Rhizosphere of Mixed Crops of Different Jhum Fields

In the present study, culture-dependent and independent [Denaturing gradient gel electrophoresis (DGGE)] approach were used to analyze the effect of fallow cycle on bacterial populations associated with mixed crops selected from three different jhum fallow cycles (5-, 10- and 20- years) of Changki village, Nagaland. Two important bacterial phyla viz. Acidobacteria and Burkholderia were selected for DGGE analysis. According to the DGGE banding profile, Acidobacteria showed more richness compared Burkholderia. The presence and absence of few of the bands in the profile indicate the community shifts in the selected jhum fields. Shannon diversity index was higher in Acidobacteria than Burkholderia. Multivariate analysis showed that Acidobacteria community structure was similar among the crop plants of the same fallow cycle. Burkholderia community did not show clear separation among fallow cycles although crop of same fallow cycle tend to group together. ANOSIM and PERMANOVA showed significant differences in rhizosphere community pattern among fallow cycles and the crop plants of same fallow cycles indicated that both fallow cycle and crop plants are factors determining the Acidobacteria and Burkholderia community composition in jhum soils which was also confirmed by the culture-dependent analysis. Culturable bacterial counts were dependent on media used and significantly different at different fallow cycles. Bacterial communities (both culturable and DGGE patterns) were correlated with soil nutrients suggesting their importance in stability of jhum soil. The present study revealed that both fallow cycle and host plant may be the key factors in shaping many bacterial communities in jhum soils.