基于大食物观的草地农业发展趋势及关键科学问题

大食物观下,国家食物安全的重点是饲料粮安全。草地农业是全球最重要的食物生产系统之一,既直接生产草畜产品,又间接地为食物生产提供生态保障,满足国家对食物安全、生态安全和边疆稳定不断增长的刚性需求。目前,草地农业保障国家食物安全的水平亟待提高,支撑国家高质量发展的能力亟待加强。种子是草地农业的物质基础,天然草原和栽培草地(也称“人工草地”)是草地农业生产食物的主要基地,草地保护为草地农业开展食物生产“保驾护航”,草地农业系统耦合促进食物生产的效益放大。草地农业是基础性战略产业,保障国家食物安全的水平依靠基础研究的创新。为此,本文分析了草类种质资源挖掘利用与种子生产控制、牧草优质高产栽培与转化、草原生态生产力维持与修复、草地有害生物管理、草地农业系统耦合与管理等5个方面的研究进展,并提出对应的关键科学问题。

Comparative transcriptome analyses reveal that the MsNST1 gene affects lignin synthesis in alfalfa(Medicago sativa L.)

As the second most abundant natural polymer,accounting for approximately 30%of the organic carbon in the biosphere,lignin plays an essential role in plant development.However,a high lignin content affects the nutritional quality of alfalfa(Medicago sativa L.),the most widely cultivated perennial legume forage crop.Histological analysis indicated that G-lignin and S-lignin were present in the stem,leaf,and petiole of alfalfa,and the deposition of lignin increased gradually in descending internodes.Neutral detergent fiber(NDF),acid detergent fiber(ADF),and acid detergent lignin(ADL)contents continually increased from the top to the bottom of the stem,and ADL content showed a similar trend in leaves.Alfalfa leaves and stems from five different nodes(1,2,4,6,and 8)were used as materials to investigate molecular regulatory mechanisms in lignin synthesis by RNA sequencing.Respectively 8074 and 7752 differentially expressed genes(DEGs)were identified in leaves and stems,and 1694 DEGs were common to the two tissues.‘‘Phenylpropanoid biosynthesis”was the most enriched pathway in both leaves and stems,and 134 key regulatory genes in lignin synthesis were identified by a weighted gene co-expression network analysis.The NAC family transcription factor MsNST1 gene was highly expressed in old leaf and stem tissues.The deposition pattern of G-and S-lignin differed among M.truncatula wild-type,nst1 mutants,and overexpression lines,and the transcription levels of lignin synthesis genes such as HCT,F5H,and COMT in these three materials also differed.These results suggest that MsNST1 affects lignin synthesis in alfalfa.These findings provide a genetic basis and abundant gene resources for further study of the molecular mechanisms of lignin synthesis,laying a foundation for low-lignin alfalfa breeding research.

Alpine grassland degradation intensifies the burrowing behavior of small mammals:evidence for a negative feedback loop

Globally,grassland degradation is an acute ecological problem.In alpine grassland on the Tibetan Plateau,increased densities of various small mammals in degraded grassland are assumed to intensify the degradation process and these mammals are subject to lethal control.However,whether the negative impact of small mammals is solely a result of population size or also a result of activity and behavior has not been tested.In this study,we use plateau pika as a model to compare population size,core area of colony,and the number of burrow entrances and latrines between lightly and severely degraded grassland.We test whether the alleged contribution of pika to grassland degradation is a result of increased population size or increased burrowing activities of individuals in response to lower food abundance.We found that grassland degradation resulted in lower plant species richness,plant height,and biomass.Furthermore,the overall population size of pika was not significantly affected by location in lightly and severely degraded grassland.However,pika core areas in severely grassland degradation were significantly larger and had significantly higher densities of burrows and latrines.Our study provides convincing evidence that habitat-induced changes in the behavior of small,burrowing mammals,such as pika,can exacerbate grassland degradation.This finding has significant implications for managing small mammals and restoring degraded grassland ecosystems.

我国牧草育种进展及存在问题

高产、优质、多抗牧草品种是保证我国草牧业可持续发展的关键,关系到国家的食物安全、生态安全和乡村振兴。自1987年至2022年底,国家审定和省级审定(西部七省份)分别通过了674个和271个草类植物新品种,并制定了25个牧草种/属的DUS测试指南。但我国牧草育种在种质资源收集、育种方法、育种方向、DUS测试和资源共享等方面仍比较薄弱,严重阻碍了我国草牧业发展进程。本文综述了我国牧草品种审定进展,分析了目前我国牧草育种存在的问题并提出建议,以期促进我国培育具有自主知识产权的高产、优质、多抗牧草新品种。

Genome-wide analysis of nucleotide-binding site disease resistance genes in Medicago truncatula

The class of nucleotide-binding site(NBS)-Leucine-rich repeat(LRR) disease resistance genes play an important role in defending plants from a variety of pathogens and insect pests. Consequently, many NBS-LRR genes have been identified in various plant species. In this study, we identified 617 NBS-encoding genes in the Medicago truncatula genome(Mt3.5v5) and divided them into two groups, regular(490) and non-regular(127) NBSLRR genes. The regular NBS-LRR genes were characterized on the bases of structural diversity, chromosomal location, gene duplication, conserved protein motifs, and EST expression profiling. According to N-terminal motifs and LRR motifs, the 490 regular NBS-LRR genes were then classified into 10 types: CC-NBS(4), CC-NBS-LRR(212), TIR-NBS(20), TIR-NBS-LRR(160), TIR-NBS-TIR(1), TIR-NBS-TIR-LRR(2), NBS-TIR(7), NBS-TIR-LRR(1), NBS(10), and NBS-LRR(73). Analysis of the physical location and duplications of the regular NBS-LRR genes revealed that the M. truncatula genome is similar to rice. Interestingly, we found that TIR-type genes are more frequently expressed than non-TIR-type genes in M. truncatula, whereas the number of non-TIR-type regular NBSLRR genes was greater than TIR-type genes, suggesting the gene expression was not associated with the total number of NBS-LRR genes. Moreover, we found that the phylogenetic tree supported our division of the regular NBS-LRR genes into two distinct clades(TIR-type and non-TIR-type), but some of the non-TIR-type lineages contain TIR-type genes. These analyses provide a robust database of NBS-LRR genes in M. truncatula that will facilitate the isolation of new resistance genes and breeding strategies to engineer disease resistance in leguminous crop.

Epichlo? festucae var. lolii endophyte affects host response to fungal disease progression in perennial ryegrass (Lolium perenne)

Dear Editor,Perennial ryegrass (Lolium perenne) is a globally important forage and turf grass species that commonly forms symbiotic associations with the asexual fungal endophyte—Epichloe festucae var.lolii.Epichloe endophytes mutualistically interact with host plants by providing major fitness enhancements and protection from both biotic and abiotic stresses (Young et al.,2013).Previous studies have shown that Epichloe festucae var.lolii inhibits the growth of plant pathogenic fungi and fungal spore germination in vitro.Additional studies conducted in the lab or field confirmed that endophytes inhibited pathogen invasion and lesion development in perennial ryegrass.However,endophytes are not always beneficial,and may even weaken the host plant and reduce the disease resistance of the host.Such inconsistent or contrasting results in Festuca spp.,Achnatherum inebrians and Leymus chinensis have also been reported (Wang et al.,2016).

Interactive effects of water stress and powdery mildew(Blumeria graminis)on the alkaloid production of Achnatherum inebrians infected by Epichlo?endophyte

Dear Editor,Achnatherum inebrians,also known as drunken horse grass（DHG）,is a toxic perennial bunch grass that can be infected by Epichloegansuensis or E.inebrians（Chen et al.,2015）.It is well known that Epichloefungal endophytes can protect their host plants from herbivores by producing different classes of alkaloids.A recent trial demonstrated that sheep exhibited notable toxicity symptoms by directly feeding with endophyte-infected（E＋）A.inebrians（Liang et al.,2017）.

Effects of Epichloë endophyte on antioxidant enzymes activities, photosynthesis and growth of three ecotypes of Elymus dahuricus

Fungal endophytes of some cultivated grasses can increase plant performance and competitive abilities,especially under stress. Far less is known about the influence of Epichlo? infections in wild populations of wild grasses. In this study, plants of three Elymus dahuricus ecotypes(WLS, QY and WTS) either infected with Epichlo? endophyte(E+) or uninfected(E–) were grown in the field. The activities of the antioxidant enzymes ascorbate peroxidase, catalase, peroxidase and superoxide dismutase, and concentrations of H_2O_2 and malondialdehyde were examined in the leaves of E+ and E– plants. We also determined photosynthesis parameters,leaf blade and sheath carbohydrate concentration and plant growth parameters of both E+ and E– plants. E+ plants from the WLS and QY populations had significantly higher antioxidant enzyme activities and photosynthetic capability(P < 0.05), superior growth characteristics including more abundant carbohydrate concentration than E– plants. In contrast, in plants from the WTS population,the endophyte had no significant effect on reactive oxygen species scavenging capability and growth performance(P > 0.05), and even displayed some negative effects on plant photosynthetic capability. Thus, endophyte infection significantly affected E. dahuricus antioxidant enzyme activities(P < 0.05), photosynthesis and growth capability,although, the effects varied with plant ecotypes.

Erratum to:The fungal endophyte Epichloë gansuensis increases NaCl-tolerance in Achnatherum inebrians through enhancing the activity of plasma membrane H^(+)-ATPase and glucose-6-phosphate dehydrogenase

1.In the results,we mistakenly described the information of Figure 9B.The correct sentence should be“The factor 1 and factor 2 explained 71.30%and 16.68%of the total variance,respectively.The 0 mmol L^(-1) NaCl concentration showed the highest contribution(29.95%)to factor 1 in roots of E+plants,and 200 mmol L^(-1) NaCl concentration was significantly loaded(45.95%)on factor 2 in roots of E+plants(Figure 9B).”

The economic value of grassland ecosystem services: A global meta-analysis

Background:Grasslands provide a wide variety of ecosystem services that contribute to human wellbeing.While an increasing number of studies are evaluating the monetary value of grassland ecosystem services,most of them focus on specific grassland ecosystem services at regional or local scales,and they use different assessment methods.Methods:This paper provides a comprehensive assessment of the economic value of global grassland ecosystem services based on a meta-analysis of 702 observations from 134 primary studies.Results:The economic values of different ecosystem services cover a wide range of grassland types,regions,and estimation methods.The annual economic value per hectare ranges from$3955 for semidesert grasslands to$5466 for tropical grasslands.On average,regulating services have the highest value,which is approximately four times that of provisioning services or approximately eight times that of food supply services.Several factors impact the estimated ecosystem service values,including the evaluation method,source and year of publication,and study site.The results indicate that the annual economic value of global grasslands exceeds$20.8 trillion.Conclusions:The findings of this study not only provide useful information for understanding the economic value of various ecosystem services associated with different types of grasslands but also have important policy implications for the ecological conservation of grassland globally.

The fungal endophyte Epichloëgansuensis increases NaCltolerance in Achnatherum inebrians through enhancing the activity of plasma membrane H^(+)-ATPase and glucose-6-phosphate dehydrogenase

Salt stress negatively affects plant growth,and the fungal endophyte Epichloëgansuensis increases the tolerance of its host grass species,Achnatherum inebrians,to abiotic stresses.In this work,we first evaluated the effects of E.gansuensis on glucose-6-phosphate dehydrogenase(G6PDH)and plasma membrane(PM)H^(+)-ATPase activity of Achnatherum inebrians plants under varying NaCl concentrations.Our results showed that the presence of E.gansuensis increased G6PDH,PMH^(+)-ATPase,superoxide dismutase and catalase activity to decrease O2•^(–),H_(2)O_(2)and Na^(+)contents in A.inebrians under NaCl stress,resulting in enhanced salt tolerance.In addition,the PM NADPH oxidase activity and NADPH/NADP+ratios were all lower in A.inebrians with E.ganusensis plants than A.inebrians plants without this endophyte under NaCl stress.In conclusion,E.gansuensis has a positive role in improving host grass yield under NaCl stress by enhancing the activity of G6PDH and PM H^(+)-ATPase to decrease ROS content.This provides a new way for the selection of stress-resistant and high-quality forage varieties by the use of systemic fungal endophytes.

Elymus sibiricus populations drive the community of root-associated arbuscular mycorrhizal fungi in a monoculture agroecosystem

Dear Editor,Arbuscular mycorrhizal fungi(AMF)belonging to phylum Glomeromycota,form symbiotic associations with roots of over 80%of land plant species in terrestrial ecosystems(van der Heijden et al.,2015).A growing body of evidence shows that symbiotic AMF are important for plant growth and health(van der Heijden et al.,2015).A plant root is commonly associated with a complex AMF community in terrestrial ecosystems(Pivato et al.,2007;Davison et al.,2015;Mao et al.,2015).

Editorial

It is our honor to offer you this inaugural issue of Grassland Research.Grassland is the largest terrestrial ecosystem on the earth.It produces an array of goods,including food,feed,fiber,and fuel,and ecosystem services as varied as weather amelioration,carbon sequestration,biodiversity enhancement,soil conservation,recreation,and the maintenance of the atmospheric composition.Historically,grassland has played an essential role in the development of civilization.Humans would likely be very different without their coevolution with grassland.The saying“All flesh is grass”indicates partially the relationship between humans and grassland.Currently,the world is facing many serious challenges and problems,including global warming,food shortages,water scarcity,land degradation and desertification,soil erosion,flooding,and other illnesses.These challenges will become more severe in the coming years,making the role of grasslands in our agricultural and ecological systems ever more important.Of course,grasslands cannot solve all these problems,but they can play a positive role in our future welfare.The development and application of science and technology,and the support of policy,will ensure that grasslands play a significant role in solving these problems.It is the obligation of grassland scientists together with other stakeholders to redouble our efforts to understand and improve grasslands.