Interactive influences of intercropping by nitrogen on flavonoid exudation and nodulation in faba bean

Yingchao Liu,Jingxiu Xiao,Li Tang,Xinhua Yin,Yi Zheng

doi:10.1038/s41598-019-41146-9

Abstract

In order to address the question of how flavonoids affected root nodulation of faba bean in a wheat and faba bean intercropping system, we set up soil and hydroponic experiments comprising two cropping pattern treatments (intercropped and monocropped) and three nitrogen (N) supply treatments at the deficient (50% N), adequate (100% N), and excessive (150% N) levels with three replicates in a randomized complete block design. Across the three N treatments and two experiments, it was frequently observed that intercropping increased but N fertilization decreased the nodule number and nodule dry weight of faba bean. Six types of flavonoids were detected in the faba bean root secretion, but only genistein, hesperetin, and naringenin often had significant correlations with the nodule number and nodule dry weight. Intercropping increased faba bean root secretions of genistein, hesperetin, and naringenin compared to monoculture only at the deficient and adequate N supply levels. The differences in flavonoids of faba bean caused by the intercropped patterns, N supply levels, and their interactions were mainly significant at flowering stage. In conclusion, interspecies and N supply interactively altered the contents and proportions of flavonoids in faba bean root exudations under wheat and faba bean intercropping. These findings provide insight into flavonoids-nodule-yield interactions in cereal and legume intercropping systems.

Highlights

In recent years, agricultural production had to strive for higher yield in order to increase food supply to feed a rapidly growing population
The nodule number was enhanced by 48.8%, 31.7%, and 93.3% with intercropped faba bean relative to its monoculture under the three N treatments, respectively (Table 1)
No difference in nodule dry weight of faba bean was observed between mono- and inter-cropping faba beans under any N treatment in the hydroponic experiment

Summary

Introduction

Agricultural production had to strive for higher yield in order to increase food supply to feed a rapidly growing population. Intercropping, as a widely accepted agronomical practice for two thousand years in China, can increase crop yield through increasing resource use efficiencies and improving land-equivalent ratio[3]. Besides the advantages of using leguminous crops as a fundamental tool for the maintenance of N fertility[10], there are many other positive effects derived from intercropping legumes with non-leguminous crops, such as enhanced yield stability, smothering of volunteer plants, pathogen and pest reduction, and increased water and nutrient use efficiencies[11,12,13]. There are very few reports revealing the underlying nitrogen-nodules-flavonoids interaction mechanisms in wheat-faba bean intercropping. The effects and related mechanisms on secretion of flavonoids and their influences on legume crop nodulation and N2 fixation at different N fertilization levels are so far unclear in leguminous and gramineous intercropping systems. It is imperative to recognize the roles performed by roots in a cereal and legume intercropping system and to understand the impacts of plant-plant interactions on rhizospheric processes

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Discussion

Conclusion