Differences in plant nutrient content, root growth and endophytic bacterial community between infected and non-infected sugarcanes by ratoon stunting disease

Objectives The characters of NPK nutrition, root growth and endophytic bacteria community in the sugarcanes that infected with ratoon stunting disease (RSD) were analyzed, which would provide an theoretical support for the control of the disease.

Methods In a field where sugarcane had been continuously grown for three years, RSD infected and RSD non-infected sugarcane plant samples were collected by digging up the whole plant. The biomass, NPK contents, root growth indices and the endophytic bacteria community structure were determined using acknowledged methods.

Results In comparison with RSD non-infected sugarcanes, in RSD infected plants, the absorption of NPK were significantly decreased, especially that of K. The root length, root surface area, root volume and tips were all decreased significantly. About the indexes of bacterial diversity, the Shannon index was significantly declined and the Simpson index was promoted. At the dominated bacteria abundance at phylum level, the ratios of Chloroflex and Actinobacteria were increased and those of the Firmicutes and the others were significantly decreased. Likewise, at genus level, the percentages and ranking of some dominant endophytic bacteria were changed obviously, and some such as Pseudarthrobacter and Rhodoplanes even disappeared at all.

Conclusions Due to infection of RSD, the root development of sugarcane is inhibited seriously, and the decrease of root length, surface area, volume and tip numbers leads to a significant decrease in nitrogen, phosphorus and potassium uptake. The worse NPK nutrition, especially K nutrition, impacts the growth of sugarcane and results low yield and quality. When infected with RSD, the diversity of endophytic bacteria is significantly decreased, although the numbers of bacteria on genus or species levels are not changed. Compared with RSD non-infected plants at phylum level, the abundance percentage of Chloroflexi and Acidobacteria increases greatly, while that of Firmicutes and others decreases. The ranking of the dominant genus of endophytic bacteria changes as well. The Pseudarthrobacter and Rhodoplanes which belong to the dominant endophytic bacteria and account for over 1% of the community in RSD non-infected plants lost in RSD infected plants.