摘要:根瘤菌與豆科植物共生是豆科植物固氮的重要方式,苜蓿作為一種優(yōu)質(zhì)豆科牧草,應(yīng)用苜蓿根瘤菌劑可以提升豆科牧草的固氮功能,提高苜蓿產(chǎn)量,降低氮肥使用量,不僅可以改善土壤結(jié)構(gòu),還能夠降低農(nóng)業(yè)生產(chǎn)成本,進(jìn)而促進(jìn)農(nóng)業(yè)可持續(xù)發(fā)展。本文介紹了根瘤菌研究和應(yīng)用概況,從根瘤菌、苜蓿根瘤菌劑及促生菌與根瘤菌共接種等方面對(duì)苜蓿生長(zhǎng)影響進(jìn)行綜述,并對(duì)根瘤菌及相關(guān)菌劑研究方向進(jìn)行展望。
關(guān)鍵詞:苜蓿;根瘤菌;促生菌;根瘤菌菌劑
中圖分類號(hào):S541" " " " " " " " "文獻(xiàn)標(biāo)志碼:A" " " " " " " " "文章編號(hào):2097-2172(2025)01-0001-07
doi:10.3969/j.issn.2097-2172.2025.01.001
Research and Application Status of Alfalfa Rhizobia and Inoculants
YANG Xiaolei YAO Tuo ZHANG Ying ZHANG Yixin ZHANG Li
(1. College of Grassland Science, Gansu Agricultural University, Lanzhou Gansu 730070, China;
2. Key Laboratory for Grassland Ecosystem of Education Ministry, Lanzhou Gansu 730070, China)
Abstract:" The symbiosis between rhizobium and leguminous plants is an important way of nitrogen fixation in leguminous plants. As a high-quality leguminous herbage, the use of alfalfa rhizobium agent can improve the nitrogen fixing function of leguminous herbage, increase the yield of alfalfa, reduce the utilization rate of nitrogen fertilizer, which improve the internal structure of soil, reduce the cost of agricultural production and promote the sustainable development of agriculture. Based on this, this paper introduces an overview of the research and application of rhizobia, reviewing the effects of rhizobia, alfalfa rhizobial inoculants, and co-inoculation of growth-promoting bacteria with rhizobia on alfalfa growth. Additionally, the paper looks ahead to future research directions for rhizobia and related microbial agents.
Key words: Alfafa; Rhizobium; Plant growth-promoting rhizobacteria (PGPR); Rhizobium agent
根瘤菌(Rhizobium)是一類重要的土壤細(xì)菌,可以生活在土壤中,也可以與豆科植物互惠互利形成根瘤進(jìn)行生物固氮[1 ]。豆科植物-根瘤菌共生固氮是目前應(yīng)用最廣泛的生物固氮方法,它們能夠從植物細(xì)胞中攝取必要的營(yíng)養(yǎng)物質(zhì),并將其轉(zhuǎn)化為氨,以滿足植物的需求。根瘤菌具有寄主專一性,即每種根瘤菌只能在特定種類的豆科植物上結(jié)瘤。苜蓿(Medicago)是重要的豆科牧草,能夠通過(guò)選擇具有共生特征的根瘤菌來(lái)產(chǎn)生固氮作用[2 ]。苜蓿根瘤菌劑的有效應(yīng)用,不僅能增強(qiáng)豆科牧草的固氮能力,大幅度減少對(duì)氮肥的依賴,緩解因過(guò)度施用氮肥導(dǎo)致的環(huán)境壓力,還能夠提升土壤地力,縮減農(nóng)業(yè)生產(chǎn)的經(jīng)濟(jì)投入,在促進(jìn)作物生產(chǎn)力穩(wěn)定、實(shí)現(xiàn)綠色高質(zhì)量發(fā)展方面潛力巨大。但目前有關(guān)苜蓿根瘤菌及其相關(guān)菌劑的綜述較少,本文從苜蓿根瘤菌、根瘤菌劑及促生菌與根瘤菌共接種等方面對(duì)苜蓿生長(zhǎng)影響等方面進(jìn)行綜述,并對(duì)根瘤菌及相關(guān)菌劑研究方向進(jìn)行展望,以期為后續(xù)研究提供指導(dǎo)。
1" "根瘤菌研究概況
近百年來(lái),國(guó)際上對(duì)豆科根瘤菌的科學(xué)研究獲得了重要發(fā)展。18世紀(jì)末,Beijerink等人首次從豆科植物的根瘤中提取了第一個(gè)純培養(yǎng)細(xì)菌,隨后,研究員Frank將該細(xì)菌命名為豆科根瘤菌(Rhizobium leguminosarum),經(jīng)過(guò)多年的研究工作,研究人員最終把能夠與豆科植物結(jié)瘤的細(xì)菌命名為“根瘤菌”[3 ]。1889年,Prazmoski運(yùn)用純培養(yǎng)技術(shù),成功將根瘤菌接種至豆科植物[4" ],直接驗(yàn)證了根瘤菌接種能促進(jìn)根瘤形成并提升其固氮效率的理論。截至目前,已經(jīng)發(fā)現(xiàn)的能成功侵染豆科植物并與豆科植物共生固氮的根瘤菌主要包括α-變形菌綱和β-變形菌綱16個(gè)屬的140多個(gè)種,包括根瘤菌屬(Rhizobium)、中慢生根瘤菌屬(Mesorhizobium)、甲基桿菌屬(Methylobacterium)、新根瘤菌屬(Neorhizobium)、中華根瘤菌屬(Sinozobium)和伯克霍爾德氏菌屬(Burkholderia)等[5 - 6 ]。
2" "苜蓿根瘤菌研究
2.1" "苜蓿根瘤菌的作用機(jī)理
根瘤菌與豆科植物之間形成了共生固氮模式,能夠有效地利用空氣中的氮素來(lái)實(shí)現(xiàn)氮素循環(huán),在農(nóng)業(yè)生產(chǎn)方式中發(fā)揮了重要作用。苜蓿根瘤的形成要求雙方基因的協(xié)同作用和生態(tài)環(huán)境的調(diào)節(jié),以及根瘤菌和苜蓿彼此間的相互作用,以達(dá)到共生固氮效果。無(wú)論根瘤菌是本土的還是通過(guò)接種劑引入的,固氮途徑都是從細(xì)菌感染植物根部開始,其發(fā)展過(guò)程包含根部定殖、觸及根表、根毛變形卷曲、侵入根毛、菌株繁殖、類菌體產(chǎn)生等,每一步都受到遺傳因素的控制[7 ]。當(dāng)苜蓿生根后,其根部釋放的碳水化合物及氨基酸為根瘤菌的繁衍提供了豐富的營(yíng)養(yǎng)物質(zhì),促進(jìn)根瘤菌聚集在根部周圍并定殖,歷經(jīng)一系列生理代謝活動(dòng),最終形成根瘤。根瘤可以固定空氣中的氮素,將空氣中的氮素轉(zhuǎn)化為能夠被植物吸收的離子態(tài)氮,使苜蓿從根瘤活動(dòng)中受益[2 ]。苜蓿進(jìn)入成熟期后,植物氮素需求減少,根瘤固氮酶活性降低,出現(xiàn)老化現(xiàn)象,表現(xiàn)為皺褶和軟化,根瘤內(nèi)的豆血紅蛋白會(huì)形成膽色素,此時(shí)的根瘤為褐綠色。隨時(shí)間推移,類菌體包膜的破裂標(biāo)志著根瘤的衰敗,其內(nèi)微生物重歸土壤循環(huán)。當(dāng)苜蓿成功越冬,第2年長(zhǎng)出新的根葉時(shí),根瘤菌就會(huì)侵染新的根系,產(chǎn)生根瘤,從而繼續(xù)為苜蓿供給氮素。因此對(duì)于2年生以上的豆科植物,根瘤通常會(huì)出現(xiàn)在當(dāng)年生長(zhǎng)的側(cè)根上,而在主根上則很難發(fā)現(xiàn)根瘤[8 - 10 ]。
2.2" "苜蓿根瘤菌的共生固氮
苜蓿的生態(tài)效益依賴于其與根瘤菌共生固氮的能力,從而減少或避免氮肥的施用[11 ]。當(dāng)苜蓿植株形成根瘤后,其光合作用產(chǎn)物的1/3將用于支持根瘤的成長(zhǎng)和固氮,從而不斷地向植株供給氮素[12 ]。苜蓿對(duì)氮素的需求量較大,共生固氮占氮素總量的33%~80%[13 ]。根瘤通過(guò)有效固定空氣中的氮素轉(zhuǎn)化成植物可以利用的氨態(tài)氮,滿足苜蓿的生長(zhǎng)需要,此過(guò)程可以減少對(duì)工業(yè)氮肥的依賴,增加土壤微生物的活性,改善土壤的物理性質(zhì)[9 ]。雖然苜蓿在收獲時(shí)會(huì)帶走部分氮素,但遺留于土壤中的根系、根瘤及下部葉片將逐漸被微生物分解,從而使土壤氮素含量增加,可以為后茬作物提供更多的營(yíng)養(yǎng)。研究表明,種植苜蓿后的純氮年產(chǎn)出量可達(dá)到220~670 kg/hm2。此外,紫花苜蓿在與禾本科作物間作套種時(shí),可為禾本科作物提供20%~30%的氮素,顯著提高農(nóng)作物的產(chǎn)量[14 - 16" ]。
2.3" "苜蓿根瘤菌緩解植物逆境脅迫研究
2.3.1" " 緩解苜蓿鹽脅迫" " 紫花苜蓿(Medicago sativa L.)是一種營(yíng)養(yǎng)豐富、適口性好的優(yōu)質(zhì)飼草[17 - 18 ],廣泛種植于干旱和半干旱地區(qū),對(duì)當(dāng)?shù)厣鐣?huì)經(jīng)濟(jì)發(fā)展做出了巨大貢獻(xiàn)[11 ],而鹽度是限制該作物生長(zhǎng)的主要因素之一[19 - 20 ]。紫花苜蓿被認(rèn)為是中等耐鹽植物,當(dāng)鹽度值接近20 mM NaCl時(shí),紫花苜蓿產(chǎn)量下降明顯[21 ]。利用傳統(tǒng)育種、標(biāo)記輔助選擇和植物基因工程等方法,已經(jīng)開發(fā)出多種策略來(lái)選育新的耐鹽品種,降低高鹽度對(duì)植物的毒性影響[22 - 23 ]。然而,這些技術(shù)進(jìn)展緩慢,且對(duì)農(nóng)民來(lái)說(shuō)難度較大。植物生長(zhǎng)與根際微生物密切相關(guān),這些微生物在脅迫和環(huán)境刺激下能提高植物的抗逆性,促進(jìn)植物生長(zhǎng)發(fā)育。因此,基于利用有益土壤微生物(根瘤菌、促生菌等)的方法被認(rèn)為是可持續(xù)農(nóng)業(yè)發(fā)展中解決鹽度問題的有效策略。
根瘤菌與苜蓿共生可以固定大氣中的氮,是農(nóng)業(yè)氮的可再生來(lái)源。除了這種營(yíng)養(yǎng)作用外,根瘤菌還可以通過(guò)以下機(jī)制緩解鹽脅迫的負(fù)面影響,包括根際酸化、增強(qiáng)根表面積、增加根分泌物(胞外多糖)、改善寄主植物葉片水分狀況、提高養(yǎng)分可利用性以及釋放細(xì)菌揮發(fā)物作為系統(tǒng)抗性的誘導(dǎo)物等[24 ]。Raklami等[25 ]和Meddich等[26 ]的研究發(fā)現(xiàn),根瘤菌可以緩解鹽脅迫并提高鹽漬土壤中的植物生產(chǎn)力,它們的有益作用與脯氨酸和糖等滲透性物質(zhì)的較高積累有關(guān)??鼓嫫贩N和根瘤菌的結(jié)合已被證明對(duì)豆科植物在鹽脅迫條件下的生長(zhǎng)和生存能力具有積極的協(xié)同優(yōu)勢(shì)[27 - 28 ]。Li等[29 ]的研究表明,根瘤菌通過(guò)GmMYB183磷酸化影響類黃酮代謝,在鹽脅迫下平衡細(xì)胞活性氧(ROS),從而防止大豆受到鹽損傷。對(duì)紫花苜蓿的代謝組學(xué)分析表明,耐鹽根瘤菌接種可以通過(guò)調(diào)節(jié)有機(jī)酸含量(草酸、檸檬酸、琥珀酸和蘋果酸)來(lái)減輕鹽脅迫對(duì)植物根系的傷害;醇類物質(zhì)和蔗糖以及特定氨基酸(脯氨酸、谷氨酸、鳥氨酸和天冬氨酸)的積累與根瘤菌提高紫花苜蓿的耐鹽性有關(guān)[21 ]。
2.3.2" " 緩解苜蓿干旱脅迫" " 干旱已成為制約作物生產(chǎn)能力和品質(zhì)提升的重大障礙。作為在我國(guó)西北和東北地區(qū)廣泛栽培的豆科牧草,苜蓿的產(chǎn)量與水分條件緊密相關(guān)[30 ]。當(dāng)干旱發(fā)生時(shí),苜蓿會(huì)遭受水分虧缺,其生長(zhǎng)發(fā)育受阻,細(xì)胞老化加速,若持續(xù)缺水時(shí)間較長(zhǎng)甚至可能引發(fā)植物的死亡[31 - 33 ]。干旱限制了植物根毛的正常生長(zhǎng),減少了根瘤菌附著及侵染的機(jī)會(huì),阻礙了根瘤的形成過(guò)程,影響根瘤菌的數(shù)量[34 ],進(jìn)而降低其豆血紅蛋白含量,對(duì)固氮酶活性產(chǎn)生負(fù)面影響[35 ]。在干旱條件下,施用根瘤菌可以提高侵染率,促進(jìn)根瘤形成,還能夠有效地減輕植物所承受的干旱壓力,抑制氧化應(yīng)激、維持滲透壓平衡等生理機(jī)能[36 - 37 ]。Defez等[38 ]對(duì)接種苜蓿劍菌(Ensifer meliloti)野生型Ms-1021及其過(guò)量產(chǎn)生吲哚乙酸(IAA)的衍生菌株Ms-RD64的植株進(jìn)行干旱脅迫,與接種Ms-1021脅迫植株相比,接種Ms-RD64的植株受到干旱損傷較輕,表明根瘤菌分泌的IAA對(duì)植物應(yīng)對(duì)干旱脅迫有積極的影響。李鵬珍等[39 ]的研究表明,接種根瘤菌條件下再外源添加生物炭,能有效提升紫花苜蓿的葉面積,從而增強(qiáng)植物的光合作用,促進(jìn)植物生長(zhǎng),進(jìn)而緩解干旱脅迫對(duì)植株的不利影響。
植物對(duì)脅迫條件最重要的調(diào)整之一是調(diào)節(jié)脫落酸(ABA)的含量。ABA廣泛參與調(diào)控植物的生命周期進(jìn)程(包括種子休眠與萌發(fā)、根系生長(zhǎng)),同時(shí)也在植物應(yīng)對(duì)各種生物脅迫和非生物脅迫中發(fā)揮重要作用,尤其是對(duì)于干旱等極端的環(huán)境因素有著極強(qiáng)的抗逆能力。ABA響應(yīng)元件結(jié)合因子(ABFs)是ABA信號(hào)傳導(dǎo)的關(guān)鍵調(diào)控因子,由營(yíng)養(yǎng)組織誘導(dǎo)響應(yīng)ABA和滲透脅迫,并激活非生物脅迫條件下植物的抗氧化防御反應(yīng)[40 - 42 ]。陳相莉[43 ]研究發(fā)現(xiàn),ABA信號(hào)傳導(dǎo)會(huì)導(dǎo)致Ca2+濃度上升或者激活鈣離子通道,從而利用鈣離子來(lái)影響結(jié)瘤信號(hào)的傳導(dǎo)途徑,進(jìn)而間接地影響根瘤的形成,進(jìn)一步證明ABA影響著豆科植物結(jié)瘤。
2.3.3" " 緩解苜蓿重金屬脅迫" " 苜蓿與根瘤菌等植物根際促生菌(Plant growth promoting rhizobacteria,PGPR)之間共生可以通過(guò)增加植物對(duì)氮和磷的吸收,增強(qiáng)植物的抗逆性來(lái)直接或間接地提升苜蓿在重金屬污染土壤中的防御[44 - 46 ]。根瘤菌具有耐受重金屬的先天能力[47 ],在受污染的土壤中種植豆科作物,可為后茬作物提供氨態(tài)氮和重金屬含量減少的土壤環(huán)境,從而有利于修復(fù)重金屬污染的土壤[48 - 49 ]。因此,作為一種新的植物-細(xì)菌污染修復(fù)策略,根瘤菌已被應(yīng)用于重金屬污染土壤中以促進(jìn)植物生長(zhǎng),提高土壤質(zhì)量。宋修勇[50 ]利用天藍(lán)苜蓿為材料,同時(shí)接種根瘤菌和促生菌可以顯著提高苜蓿的株高、根長(zhǎng)、地上部分及根部生物量、根瘤數(shù)。同時(shí),與單接種根瘤菌相比,雙接種植株對(duì)Zn和Cu的吸收量增加了89.22%和154.11%;而與單接促生菌相比,雙接種植株對(duì)Zn和對(duì)Cu的吸收量也顯著提高了28.36%和306.01%。接種根瘤菌主要通過(guò)促進(jìn)氮素的積累來(lái)提高苜蓿的植物提取能力。研究發(fā)現(xiàn),接種根瘤菌后,苜蓿葉片丙二醛含量降低,葉綠素含量、養(yǎng)分吸收、Cd積累和轉(zhuǎn)運(yùn)因子增加,增加了植株總氮的積累,接種根瘤菌和適量施氮可作為苜蓿修復(fù)Cd污染土壤的有效措施[51 ]。
苜蓿在重金屬脅迫下會(huì)產(chǎn)生大量的活性氧自由基,破壞細(xì)胞內(nèi)環(huán)境穩(wěn)定性并影響細(xì)胞膜透性,嚴(yán)重抑制了生物固氮能力。然而,根瘤中的抗氧保護(hù)機(jī)制能夠有效減輕由氧化應(yīng)激引起的損害,從而維系了其生物固氮的能力[52 - 53 ]。根瘤菌展現(xiàn)出的金屬耐受性、還原潛能以及促進(jìn)豆科植物生長(zhǎng)的能力,使之成為凈化金屬污染土壤的理想生物工具,并能有效緩解重金屬對(duì)紫花苜蓿的不良效應(yīng)。
3" "根瘤菌劑應(yīng)用概況
接種根瘤菌有助于提升苜蓿的結(jié)瘤率,提高苜蓿的產(chǎn)量及蛋白質(zhì)含量,同時(shí)促使后續(xù)輪作作物實(shí)現(xiàn)更高的產(chǎn)量收益,展現(xiàn)出突出的經(jīng)濟(jì)價(jià)值與生態(tài)效益[18 ]。1895年,美國(guó)和英國(guó)首先嘗試商業(yè)化生產(chǎn)豆科根瘤菌劑,加拿大、瑞典和澳大利亞也在1905年和1914年進(jìn)行工業(yè)生產(chǎn)根瘤菌劑,為了滿足當(dāng)?shù)卮笠?guī)模栽培豆科牧草產(chǎn)品的需求,根瘤菌劑的產(chǎn)量迅速發(fā)展壯大。據(jù)統(tǒng)計(jì),接種苜蓿根瘤菌面積約占苜??偡N植面積的30%~50%,更有部分發(fā)達(dá)國(guó)家占比達(dá)到80%以上[54 ]。Schwieger等[55 ]研究發(fā)現(xiàn),經(jīng)根瘤菌接種處理的紫花苜蓿,植物根表微生物群落發(fā)生顯著變化,突出表現(xiàn)為根瘤菌數(shù)量的大幅增長(zhǎng)。此外,相關(guān)研究進(jìn)一步指出,根瘤菌接種對(duì)根際土壤微生物同樣產(chǎn)生了一定程度的影響[56 - 57 ]。
我國(guó)根瘤菌劑的研究始于20世紀(jì)30年代,經(jīng)過(guò)幾十年的發(fā)展,我國(guó)根瘤菌劑相關(guān)研究已達(dá)到國(guó)際先進(jìn)水平。寧國(guó)贊等[58 - 59 ]對(duì)內(nèi)蒙古自治區(qū)在內(nèi)的23個(gè)省區(qū)開展根瘤菌接種試驗(yàn),結(jié)果表明,接種根瘤菌菌劑處理的紫花苜蓿有結(jié)瘤早、結(jié)瘤率高以及根瘤重量大等優(yōu)點(diǎn)。韓可等[60 ]通過(guò)接種不同根瘤菌對(duì)龍牧806和中苜三號(hào)紫花苜蓿的株高、地上干重和全氮量進(jìn)行檢測(cè),發(fā)現(xiàn)接種根瘤菌可有效提高植株的生產(chǎn)力。然而,受限于發(fā)酵生產(chǎn)工藝落后及產(chǎn)品質(zhì)量不達(dá)標(biāo)等問題,根瘤菌劑的大規(guī)模工業(yè)化生產(chǎn)和廣泛應(yīng)用面臨一定挑戰(zhàn)[61 ]。同時(shí),根瘤菌劑存在占瘤率低、自然環(huán)境適應(yīng)性差、接種效果不理想及受地域和環(huán)境限制等缺點(diǎn),從而無(wú)法有效提高植株生長(zhǎng)發(fā)育水平,阻礙了其在農(nóng)業(yè)生產(chǎn)中的應(yīng)用和發(fā)展[62 - 63 ]。
近年來(lái),研究人員對(duì)促生菌和根瘤菌共接種管理的促生效果開展了深入研究。發(fā)現(xiàn)將有益微生物與根瘤菌共同接種能有效促進(jìn)豆科植物根系生長(zhǎng),為根瘤菌的定殖提供更多的侵染位點(diǎn),繼而增強(qiáng)氮素的利用率,顯著地提高了豆科作物的產(chǎn)量[64 ]。協(xié)同作用能夠更有效幫助宿主植株的結(jié)瘤固氮,有效提升了植株的養(yǎng)分利用率和土壤肥力,進(jìn)而為植株的生長(zhǎng)提供了有力的支持[65 ]。促生菌與根瘤菌的聯(lián)合作用極大提升了宿主植物的結(jié)瘤數(shù)量、固氮效率、根系發(fā)育及根部營(yíng)養(yǎng)元素利用率,因而有利于植株的健康生長(zhǎng)[66 - 67 ]。諸多屬的促生菌能夠與根瘤菌共同作用,有效地幫助豆科植物生長(zhǎng)發(fā)育、結(jié)瘤和固氮,從而發(fā)揮出協(xié)同效應(yīng),為豆科植物的發(fā)育提供重要的支持[68 - 69 ]。劉冠一[66 ]發(fā)現(xiàn),熒光標(biāo)記根瘤菌與5株P(guān)GPR分別共接種于紫花苜蓿,顯著提升了根瘤數(shù)量,并且有助于根系的生長(zhǎng)發(fā)育,顯著提升了ACC脫氨酶、吲哚乙酸(IAA)的合成、解無(wú)機(jī)磷能力及固氮能力,改善了紫花苜蓿的生長(zhǎng)環(huán)境。Morel等[70 ]發(fā)現(xiàn),中華根瘤菌(Sinorhizobium meliloti)U143與促生菌Delftia sp. JD2共接種可提高紫花苜蓿的地上部和根系質(zhì)量,在微生物-植物相互作用的早期,酚類化合物(包括黃酮類化合物)、有機(jī)酸和揮發(fā)性化合物的定性和定量變化表明,某些分子的產(chǎn)生對(duì)微生物-植物關(guān)系產(chǎn)生積極影響。
4" "展望
隨著我國(guó)對(duì)優(yōu)質(zhì)苜蓿需求量的不斷提升,苜蓿種植面積不斷擴(kuò)大,氮肥需肥量隨之增大。長(zhǎng)期以來(lái),人類在農(nóng)業(yè)生產(chǎn)中重度依賴化學(xué)肥料以保障作物產(chǎn)量,過(guò)度施用氮肥不僅會(huì)損害土地的理化性質(zhì),還會(huì)對(duì)人類健康造成嚴(yán)重威脅。鑒于此,加強(qiáng)對(duì)苜蓿根瘤菌的研究及其應(yīng)用潛力開發(fā),提升其固氮效能,拓寬苜蓿根瘤菌制劑的應(yīng)用領(lǐng)域具有重要的意義和廣闊的發(fā)展前景。為更有效地促進(jìn)苜蓿與根瘤菌的共生結(jié)瘤及其固氮效率,可通過(guò)以下措施提高苜蓿根瘤菌固氮潛力,一是根據(jù)種植當(dāng)?shù)赝寥?、氣候、苜蓿品種等多種因素,選擇適合的專一性強(qiáng)的苜蓿根瘤菌株,以確保充分發(fā)揮根瘤菌的生物固氮潛力,減少對(duì)化學(xué)氮肥的依賴。二是合理施用氮肥,通過(guò)有機(jī)肥替代等方式減少氮肥施用量,減輕過(guò)量施用氮肥導(dǎo)致的徑流和滲透進(jìn)入地下水會(huì)造成的環(huán)境污染。三是重視抗逆性強(qiáng)的根瘤菌菌種選育,加強(qiáng)對(duì)耐旱、耐鹽堿、耐重金屬脅迫等菌株的篩選,提升菌株應(yīng)用范圍,響應(yīng)國(guó)家號(hào)召,使不能種植農(nóng)作物的鹽堿地、重金屬污染土地等變?yōu)榭梢苑N植紫花苜蓿的改良地。最后,應(yīng)針對(duì)性地篩選適合特定土壤類型、固氮能力強(qiáng)且結(jié)瘤性能優(yōu)異的本土菌株,并探究根瘤菌與本土化微生物或其他有益微生物間的互作機(jī)制,進(jìn)而研制出創(chuàng)新的復(fù)合微生物菌劑。隨著科學(xué)技術(shù)進(jìn)步,有效運(yùn)用多學(xué)科方法如宏基因組、代謝組等,進(jìn)一步完善菌劑的生產(chǎn)工藝流程、并進(jìn)行大規(guī)模推廣應(yīng)用,這無(wú)疑會(huì)成為未來(lái)的重要研究方向,使其在豆科植物生長(zhǎng)過(guò)程中得以更好的利用。
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