Suitability of Mycorrhiza-Defective Rice and Its Progenitor for Studies on the Control of Nitrogen Loss in Paddy Fields via Arbuscular Mycorrhiza.

Xinyue Guo,Zhaoyang You,Wenfei Yun,Yu Xia,Shujuan Zhang,Matthias C. Rillig

doi:10.3389/fmicb.2020.00186

Abstract

Employing mycorrhiza-defective mutants and their progenitors does not require inoculation or elimination of the resident microbial community in the experimental study of mycorrhizal soil ecology. We aimed to examine the suitability of mycorrhiza-defective rice (non-mycorrhizal, Oryza sativa L., cv. Nipponbare) and its progenitor (mycorrhizal) to evaluate nitrogen (N) loss control from paddy fields via arbuscular mycorrhizal (AM) fungi. We grew the two rice lines in soils with the full community of AM fungi and investigated root AM colonization. In the absence of AM fungi, we estimated rice N content, soil N concentration and microbial community on the basis of phospholipid fatty acids; we also quantified N loss via NH3 volatilization, N2O emission, runoff and leaching. In the presence of AM fungi, we did not find any evidence of AM colonization for non-mycorrhizal rice while mycorrhizal rice was colonized and percentage of root colonization was 17–24%. In the absence of AM fungi, the two rice lines had similar N content, soil N concentration and microbial community. Importantly, there was no significant difference in N loss via all the four pathways between mycorrhizal and non-mycorrhizal systems. This mycorrhizal/non-mycorrhizal rice pair is suitable for further research on the role of AM fungi in the control of soil N loss in paddy fields.

Highlights

In rice production, nitrogen (N) is one of the main limiting nutrients, requiring N fertilizer application to enhance rice productivity
In the absence of arbuscular mycorrhizal (AM) fungi (Experiment 3), no AM colonization was observed in any rice line
In the absence of AM fungi (Experiment 3), there was no difference in biomass for shoot and root between the two rice lines; the plant N concentrations were similar; there was no difference in the plant N content between mycorrhizal and non-mycorrhizal rice lines (Figure 2)

Summary

Introduction

Nitrogen (N) is one of the main limiting nutrients, requiring N fertilizer application to enhance rice productivity. The amount of N fertilizers applied is intensive and excessive in China. Less than 35% of N fertilizers applied can be taken up by rice in the current growing season (Cao and Yin, 2015); the rest of N is transported into surrounding water systems via runoff and leaching and lost via N2O emission and NH3 volatilization. Test of Non-mycorrhizal Rice rice paddy field via runoff; 14% of N via leaching, 59% via NH3 volatilization and 2% via N2O emission. N loss does lead to degradation of water systems, but it contributes to greenhouse gas emission directly via N2O emission and indirectly via NH3 volatilization (Lam et al, 2017). It is crucial to reduce N loss from paddy fields to mediate water degradation and to cope with climate change

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