Over 110 million tons of nitrogen fertilizer every year is used for crop production.Scientists have dreamed of enabling rhizobial nitrogen fixation in non-leguminous crops to mitigate the increasing demand for nitroge...Over 110 million tons of nitrogen fertilizer every year is used for crop production.Scientists have dreamed of enabling rhizobial nitrogen fixation in non-leguminous crops to mitigate the increasing demand for nitrogen fertilizer.However,despite decades of research,rhizobial nitrogen fixation in non-host plants has not been demonstrated.Here,we reported that an N-fixing rhizobium and a clubroot pathogen Plasmodiophora brassicae exhibited a synergistic effect on fixing nitrogen in cruciferous plants.Rhizobia were found to invade P.brassicae-infected rapeseed(Brassica napus)roots in the field.The colonization of rhizobium on rapeseed roots was confirmed by co-inoculating Mesorhizobium huakuii with P.brassicae under controlled laboratory conditions.M.huakuii infection could alleviate clubroot symptoms and promote the growth of diseased rapeseeds.M.huakuii could fix nitrogen in P.brassicae-infected plants based on the results of 15N isotope dilution tests.The expression of homologs of legume genes required for symbiosis and early-nodulin genes was significantly upregulated in Arabidopsis during early infection by P.brassicae.More importantly,M.huakuii could even fix nitrogen in P.brassicae-resistant rapeseed cultivar and promote plant growth when co-inoculated with P.brassicae.Our findings provide a new avenue to understand the interaction of rhizobia with non-host plants,stimulate the exploration of fixing nitrogen in non-leguminous plants by nitrogen-fixing rhizobia,and develop a strategy for both disease control and nitrogen fixation on non-host crops.展开更多
Soil microbial biomass is an active fraction of soil organic matter. It shows quicker response than soil organic matter to any change in the soil environment. Being an index of soil fertility, it plays a key role in t...Soil microbial biomass is an active fraction of soil organic matter. It shows quicker response than soil organic matter to any change in the soil environment. Being an index of soil fertility, it plays a key role in the decomposition of litters and fast release of available nutrients. Leaf litters of leguminous and non-leguminous species in alone and mixed form were applied as treatments in the soil to observe the changes in the magnitude of soil microbial biomass. Soil microbial biomass C and N were determined by chloroform fumigation extraction method. Increment in the concentration of microbial biomass C and N was higher in the treatments with leguminous leaf litter (497 - 571 μgCg?1, 48 - 55 μgNg?1) than the non-leguminous one (256 - 414 μgCg?1;22 - 36 μgNg?1). However, when non-leguminous litters were mixed with leguminous litters then the values increased distinctly (350 - 465 μgCg?1, 28 - 48 μgNg?1). On the basis of increment in soil microbial biomass, leaf litters of the species considered potential to improve soil nutrients are—Cassia siamea and Dalbergia sissoo from leguminous trees, Anthocephalus + Cassia and Shorea + Dalbergia from mixed form of non-leguminous and leguminous one and Eichhornia crassipes, an alien aquatic macrophyte. The leaf litters of these species can be used as source of organic matter to improve the crop yield.展开更多
基金supported by the Fundamental Research Funds for the Central Universities(2662022PY001)Wuhan Science and Technology Project(2020020601012260)the earmarked fund for CARS-12.
文摘Over 110 million tons of nitrogen fertilizer every year is used for crop production.Scientists have dreamed of enabling rhizobial nitrogen fixation in non-leguminous crops to mitigate the increasing demand for nitrogen fertilizer.However,despite decades of research,rhizobial nitrogen fixation in non-host plants has not been demonstrated.Here,we reported that an N-fixing rhizobium and a clubroot pathogen Plasmodiophora brassicae exhibited a synergistic effect on fixing nitrogen in cruciferous plants.Rhizobia were found to invade P.brassicae-infected rapeseed(Brassica napus)roots in the field.The colonization of rhizobium on rapeseed roots was confirmed by co-inoculating Mesorhizobium huakuii with P.brassicae under controlled laboratory conditions.M.huakuii infection could alleviate clubroot symptoms and promote the growth of diseased rapeseeds.M.huakuii could fix nitrogen in P.brassicae-infected plants based on the results of 15N isotope dilution tests.The expression of homologs of legume genes required for symbiosis and early-nodulin genes was significantly upregulated in Arabidopsis during early infection by P.brassicae.More importantly,M.huakuii could even fix nitrogen in P.brassicae-resistant rapeseed cultivar and promote plant growth when co-inoculated with P.brassicae.Our findings provide a new avenue to understand the interaction of rhizobia with non-host plants,stimulate the exploration of fixing nitrogen in non-leguminous plants by nitrogen-fixing rhizobia,and develop a strategy for both disease control and nitrogen fixation on non-host crops.
文摘Soil microbial biomass is an active fraction of soil organic matter. It shows quicker response than soil organic matter to any change in the soil environment. Being an index of soil fertility, it plays a key role in the decomposition of litters and fast release of available nutrients. Leaf litters of leguminous and non-leguminous species in alone and mixed form were applied as treatments in the soil to observe the changes in the magnitude of soil microbial biomass. Soil microbial biomass C and N were determined by chloroform fumigation extraction method. Increment in the concentration of microbial biomass C and N was higher in the treatments with leguminous leaf litter (497 - 571 μgCg?1, 48 - 55 μgNg?1) than the non-leguminous one (256 - 414 μgCg?1;22 - 36 μgNg?1). However, when non-leguminous litters were mixed with leguminous litters then the values increased distinctly (350 - 465 μgCg?1, 28 - 48 μgNg?1). On the basis of increment in soil microbial biomass, leaf litters of the species considered potential to improve soil nutrients are—Cassia siamea and Dalbergia sissoo from leguminous trees, Anthocephalus + Cassia and Shorea + Dalbergia from mixed form of non-leguminous and leguminous one and Eichhornia crassipes, an alien aquatic macrophyte. The leaf litters of these species can be used as source of organic matter to improve the crop yield.
