【作者】 师尚礼；

【导师】 曹致中；

【作者基本信息】 甘肃农业大学 ， 草业科学， 2005， 博士

【摘要】 提高紫花苜蓿（Medicago sativa L.）产量及质量最重要的方法之一是给苜蓿接种高效固氮根瘤菌,苜蓿根瘤菌除与根系共生结瘤进行固氮之外,是否具有其它生物功能和作用目前尚未见报道。随着联合固氮微生物研究的深入,促生菌研究已从固氮范畴扩展到固氮、溶磷和分泌生长激素等多功能范畴（Hendry GS 1983）,共生固氮微生物—根瘤菌是非常重要的一类促生菌,按照促生微生物存在多功能促进生长的特点,开辟根瘤菌其它促生功能的研究,进一步研究根瘤菌的促生机理和影响根瘤菌结瘤与促生功能影响因子,筛选优质高效多功能促生根瘤菌株尤为重要。本研究对甘肃5个不同生态区域阿尔冈金苜蓿（M. Algonquin）和陇东苜蓿（M. Longdong）草地春、夏、秋三季根瘤菌结瘤能力及其影响因子进行大系统多层次权重分析,采用YMA培养基法、回接初筛选试验法、¹⁵N同位素稀释法、蒙金娜培养基和PKO培养基溶磷圈法、刚果红液体培养基比色法、YMA培养基附加胁迫因子培养法对根瘤菌进行了分离纯化和筛选,对初筛选菌株的固氮能力、溶磷能力、分泌生长素IAA能力和抗逆能力进行了测试,采用多元逐步回归和通径分析讨论了影响根瘤菌固氮、溶磷、分泌生长素、抗逆能力的主要土壤理化因子,结果表明:1)研究区域大部分属干旱半干旱地区,不论是旱作区的长期干旱,还是灌溉区的间隙性干旱,水分因子对根瘤菌结瘤数量造成较大影响,进而影响固氮量,表现出干旱地区苜蓿草地的干旱胁迫缺氮。2)供试的两个苜蓿品种,阿尔冈金苜蓿根瘤菌的有效性（结瘤能力）高于陇东苜蓿。并且在甘肃区域苜蓿结瘤主要发生于春季,春季苜蓿根瘤菌的有效性比夏季和秋季高。这一研究结果为甘肃苜蓿栽培应用根瘤菌剂最佳施用时期提供了依据。3)综合考虑各项根瘤测定指标,苜蓿根瘤菌在不同区域土类中的有效性以庆阳黑垆土最好,其次为武威灌淤土和定西灰钙土。甘南亚高山草甸土区,根瘤较大,但数量最少,根瘤菌的有效性不高,气温低和生长季节短是主要的限制性因素。天水褐土根瘤菌有效性差,与该土粘重、易板结、通气性差有关。4)不同区域苜蓿根瘤菌平均固氮能力差异性较大。庆阳、武威菌株平均固氮能力最强,定西菌株次之。菌株对生物量平均作用的大小与来源地区菌株固氮能力的强弱相对应,亦即庆阳、武威和定西菌株对苜蓿的平均促生能力较好,甘南菌株平均促生能力中等,天水菌株平均促生能力差。5)¹⁵N示踪试验表明,苜蓿%¹⁵N含量在0.425 %以下时,苜蓿% ¹⁵N含量与固更多还原

【Abstract】 Biological nitrogen fixation is a biochemical process attracting almost the same attention as photosynthesis. With the deepening research of nitrogen fixation bio-organisms, their growth-improving effects have been shown from nitrogen fixation, phosphorus dissolving and growth hormone secret (Hendry G S, 1983).Alfalfa is one of the main cultivated forage legumes in China, the most important way to improve its yield and quality is effective rhizobia inoculation. However, whether alfalfa rhizobia have other biological functions except nitrogen fixation has not been elucidated. So it is vital to find factors affecting noduling and growth-improvement, to screen effective multi-function rhizobia strains for different ecological regions and varieties. In this study, the noduling and its affecting factors in two alfalfa pastures (cv. Algonquin and Longdong) from 5 different eco-regions were analyzed by means of Analytical Hierarchy Process (AHP) in spring, summer and fall.The ability of nitrogen fixation phosphorus dissolving,IAA secret and stress tolerance of selected strains was tested and the main soil physical and chemical factors affecting the above ability were analyzed and discussed by means of multi-regression and path analysis.The results showed that:1) Soil moisture played a vital role on nodule number of alfalfa rhizoia both in long term drought in arid regions and interval drought in irrigation regions. Alfalfa pasture showed nitrogen deficiency under drought stress in drought regions.2) The noduling ability of Algonquin was higher than that of Longdong. This difference could partly attributed to environmental factors and their genetic features. Furthermore, in Gansu province, nodule formation mainly took place in spring, with higher capacity than in summer and autumn. The appropriate temperature for nodule formation could be lower than 15～20℃.3) Taking all the indexes of alfalfa rhizobia into a comprehensive consideration, meanwhile referring to effective nodule rate, the effectiveness of alfalfa rhizobia in different types of soils could be scored as chernozem soil in Qingyang >irrigate soil in Wuwei >podzol soil in Dingxi. Soil from sub-alpine meadow in Gannan had a better effect更多还原