Rice Root-Associated Diazotrophic Community Succession is Driven by Growth Period Combined With Fertilization

Abstract

BackgroundBiological nitrogen fixation (BNF) and nitrogenous fertilizers are two crucial ways for nitrogen input in the rice paddy system. Little is known about the effect of nitrogenous fertilizers on root-associated diazotrophs. Here, we investigated the succession of total and active diazotrophs in rhizosphere soil and rice roots under four fertilization treatments (control, NPK, NPK + pig manure, and NPK + rice straw) during three key growth periods (tillering, heading and mature).ResultsThe 15N isotope dilution experiment verified that root-associated diazotrophs could supply N for rice under low nitrogen nutrition by BNF (%Ndfa=11.51). Niche differentiation of diazotrophs existed at the rhizosphere soil-root interface. At both DNA and RNA levels, growth period had stronger effects on the community composition of endophytic diazotrophs than rhizosphere diazotrophs. The Chao1 and Shannon indices of total endophytic diazotrophs dramatically increased at the vegetative stage, and underwent relatively minor changes at the reproductive stage. Furthermore, the community structures of total endophytic diazotrophs were more stabilized in the reproductive stage than the vegetative stage. The number of OTUs shared by rhizosphere soil and roots increased during rice growth. Compared with CK, NPK reduced the relative abundances of Pelobacter and increased the relative abundances of Azoarcus. Pig manure not only improved soil nutrients (OM, TN, TP, AN, AP and NO3-N), but reduced the effect of chemical fertilizers on the community composition of natural rhizosphere diazotrophs. ConclusionsGrowth period demonstrated a stronger influence on the root-associated diazotrophs than fertilization practices. The community structures of total endophytic diazotrophs were more stabilized in the reproductive stage than the vegetative stage, and the alpha-diversity indices and complex of network structures of endophytic diazotrophs increased at the vegetative stage. Replacing chemical fertilization with pig manure not only increased soil nutrients, but regulated rhizosphere diazotrophic community structures. Understanding the combined effects of growth period and fertilization on root-associated diazotrophs presents the basis towards the sustainable crop production.

Temporal dynamics of total and active root-associated diazotrophic communities in field-grown rice

“…We thank Jiaqin Fan of Nanjing Agricultural University for generously providing greenhouse and Yongfeng Li of Jiangsu Academy of Agricultural Sciences, Nanjing, China, for kindly providing assistance in rice cultivation management. The older version of this manuscript has been released as a pre-print at Research Square ( Cui et al, 2020 ).…”