北京地区早熟禾褐斑病菌生物学特性及防治研究

对北京地区早熟禾褐斑病分离到的立枯丝核菌(Rhizoctonia solaniKuhn)进行了7个温度(12,16,20,24,28,32,36℃)、两种光照条件(全黑暗和12 h光暗交替)下的菌丝生长速率测定、菌核产生量比较,温度对发病的影响,10种杀菌剂的抑菌试验和几种杀菌剂的田间药效试验。菌丝生长的适宜温度范围为24~32℃;12 h光/暗交替条件下,菌丝生长速率加快;32℃下菌核产生量显著多于其他温度;20~30℃下早熟禾发病严重。多菌灵、扑海因、坪安1号和多氧霉素等杀菌剂的抑菌效果好。田间药效试验表明,扑海因、井岗霉素、坪安1号和多菌灵对褐斑病有良好的防治作用。     

单萜酚类化合物与苯醚甲环唑和噻呋酰胺混配对立枯丝核菌的抑菌活性研究

为探究单萜酚类化合物与杀菌剂混配对立枯丝核菌的抑制效果,筛选能够防治水稻、玉米纹枯病的药剂,本研究分别将百里香酚、香芹酚与苯醚甲环唑、噻呋酰胺混配,通过菌丝生长速率法测定了其对R. solani的抑菌活性,并以孙云沛法评价了单萜酚与杀菌剂混配的增效作用。试验结果表明：香芹酚、百里香酚与噻呋酰胺以1:5、1:4、2:3、3:2、4:1和5:1比例混配均表现出协同增效作用,其中香芹酚和噻呋酰胺4:1混配的抑菌效果最好,EC₅₀值为0.928 mg/L,共毒系数(CTC)为1397.39;香芹酚与苯醚甲环唑以3:2、4:1和5:1比例混配以及百里香酚与苯醚甲环唑以2:3、4:1和5:1比例混配也表现出协同增效作用。百里香酚和香芹酚对苯醚甲环唑和噻呋酰胺增效作用明显,香芹酚与噻呋酰胺的4:1混剂对R. solani抑菌活性高,具备应用于水稻、玉米纹枯病的防治的潜力。天然单萜酚类化合物与杀菌剂以一定比例混配能够显著提高其抑菌活性,在杀菌剂研发、筛选中具备很高的研究价值。     

黑痣病菌毒素诱导马铃薯幼苗体内防御酶活性的变化

试验选取对黑痣病菌抗性不同的马铃薯材料,研究黑痣病菌毒素处理后马铃薯幼苗体内防御酶活性的变化及其与抗黑痣病的关系,以探讨马铃薯抗黑痣病机制。结果表明,经毒素处理一定时间,POD、PPO、SOD和CAT这4种防御酶活性都有不同程度的提高。处理36～96 h时,POD、PPO、SOD活性快速升高,抗病品种底西芮酶活性的增加值明显大于感病品种大西洋的增加值;CAT活性先降低后升高,60 h达到最高,但处理时间内酶活性的增加值和品种抗病性不相关。处理96 h以后,POD和SOD的活性仍升高,但酶活性增加值在抗感品种之间没有显著差异,PPO和CAT的活性增加值降低。     

长枝木霉T8对水稻纹枯病菌拮抗作用的研究

对峙培养表明：长枝木霉T8[Trichoderma longibrachiatum]对立枯丝核菌有较强的拮抗作用,拮抗系数为1。长枝木霉T8对立枯丝核菌形成明显的拮抗区带,界面处病菌菌丝的细胞质变稀薄、消解或菌丝断裂,病菌菌丝停止生长,同时对立枯丝核菌菌核形成包围,抑制其萌发。在光学显微镜下,可观察到长枝木霉T8对立枯丝核菌菌丝的缠绕、细胞质变稀薄、菌丝消解、菌丝断裂或侵入等现象。     

长枝木霉T8对水稻纹枯病菌拮抗的作用研究

对峙培养表明:长枝木霉T8[Trichoderma longibrachiatum]对立枯丝核菌有较强的拮抗作用,拮抗系数为1。长枝木霉T8对立枯丝核菌形成明显的拮抗区带,界面处病菌菌丝的细胞质变稀薄、消解或菌丝断裂,病菌菌丝停止生长,同时对立枯丝核菌菌核形成包围,抑制其萌发。在光学显微镜下,可观察到长枝木霉T8对立枯丝核菌菌丝的缠绕、细胞质变稀薄、菌丝消解、菌丝断裂或侵入等现象。     

提高棉种置床发芽率的措施

在新疆,棉种以常规种子为主,种植面积大,用种量远远超过其他作物,因而其发芽率在质量评定上非常重要。但棉种发芽率与其他大田作物相比,即使在室内最适宜的条件下,也极易感染立枯丝核菌,所检测的发芽率也往往比种子的实际发芽率偏低,给销售和调运带来困难。经过近几年的实践和摸索,笔者认为应做好以下关键几点。     

橡胶树棒孢霉落叶病苗圃防治初报

为了给田间筛选出防治橡胶树棒孢霉落叶病的高效药剂,对甲基硫菌灵、咪鲜胺锰盐、多菌灵、百菌清、咪鲜胺等5种杀菌剂在发病苗圃进行常规防治试验。结果表明：25%咪鲜胺乳油最好,2000倍液药后28天防效达到82.99%;75%百菌清可湿性粉剂次之,2000倍液药后28天防效达到78.20%;70%甲基硫菌灵可湿性粉剂、50%咪鲜胺锰盐可湿性粉剂、50%多菌灵可湿性粉剂的防效较差,参试浓度防效均在50%以下。初步结论表明,25%咪鲜胺乳油和75%百菌清可湿性粉剂为苗圃防治橡胶树棒孢霉落叶病的较好药剂,推荐使用浓度为2000倍。     

河北省棉花立枯丝核菌菌丝融合群及其致病性研究

从河北省22个主要产棉县市分离纯化得到67个棉花立枯病菌菌株,经鉴定均为立枯丝核菌(Rhizoctonia solani Kühn)。菌丝融合试验表明,其中的62个菌株属于2个菌丝融合群,即AG-4和AG-2,分别占测定菌株的91.04%和1.50%;另有5个菌株与标准菌株不融合,占7.46%,表明河北省棉田立枯丝核菌的优势菌系是AG-4融合群。通过选用麦芽蛋白胨(MPDA)培养基(Ⅱ)进行对峙培养,将AG-4融合群菌株划分为6个不同的营养亲和群,即AG-4-A、AG-4-B、AG-4-C、AG-4-D、AG-4-E和AG-4-F,分别占测定菌株的59.02%,6.56%,9.84%,1.64%,21.31%,1.64%。致病力测定结果表明,不同菌丝融合群及其各营养亲和群致病力不同,以AG-4-A对棉苗的致病力最强,其次是AG-2,均导致棉苗死亡;AG-4-E和AG-4-F虽然致病,但并不致死棉苗,各群相对致病力强弱顺序依次为:AG-4-AAG-2AG-4-BAG-4-C非融合类AG-4-DAG-4-EAG-4-F。     

大豆立枯丝核菌G蛋白β亚基基因的克隆与分析

由立枯丝核菌[Rhizoctonia solani Kuhn,有性世代:Thanatephorus cucumeris(Frank)Donk]引起的大豆纹枯病(soybean sharp eyespot)是一种重要病害.G蛋白β亚基(guanine nucleotide binding protein beta-subunit)作为重要的信号传导因子,在植物病原菌致病分子机制中起着重要作用.为了解G蛋白β亚基基因的结构与功能,根据同源物种G蛋白β亚基相关序列设计引物,利用PCR和RT-PCR技术克隆了大豆立枯丝核菌G蛋白β亚基的基因序列和开放阅读框(G-protein beta-subunit of soybean Rhizoctonia solani,简写为gbsrs1,GenBank登录号为EU663628).该片段全长1 864 bp,含有4个内含子和5个外显子;开放阅读框(ORF)长1 047 bp,编码348氨基酸残基,与多种真菌G蛋白β亚基的氨基酸序列相似程度较高,达79.72%-99-43%;该蛋白质具有2个α-螺旋和7个β-折叠的二级结构,形成无规则卷曲连接的桶形三级结构.将gbsrs1的ORF连接于原核融合表达载体pGEX-4T-2中,经IPTG诱导,获得了相应蛋白的表达.gbsrs1的克隆和特性研究为了解大豆立枯丝核菌的致病机理、有效防治纹枯病奠定了基础.     

大豆立枯丝核菌G蛋白ß亚基基因的克隆与分析

由立枯丝核菌[Rhizoctonia solani Kühn,有性世代：Thanatephorus cucumeris (Frank) Donk] 引起的大豆纹枯病(Soybean sharp eyespot)是一种重要病害。G蛋白β亚基(Guanine nucleotide binding protein beta-subunit)作为重要的信号传导因子,在植物病原菌致病分子机制中起着重要作用。为了解G蛋白β亚基基因的结构与功能,根据同源物种G蛋白β亚基相关序列设计引物,利用PCR和RT-PCR技术克隆了大豆立枯丝核菌G蛋白β亚基的基因序列和开放阅读框(G-protein beta-subunit of Soybean Rhizoctonia solani,简写为gbsrs1,GenBank登录号为EU663628)。该片段全长1 864 bp,含有4个内含子和5个外显子;开放阅读框(ORF)长1 047 bp,编码348氨基酸残基,与多种真菌G蛋白β亚基的氨基酸序列相似程度较高,达79.72%~99.43%;该蛋白质具有2个α-螺旋和7个β-折叠的二级结构,形成无规则卷曲连接的桶形三级结构。将gbsrs1的ORF连接于原核融合表达载体pGEX-4T-2中,经IPTG诱导,获得了相应蛋白的表达。gbsrs1的克隆和特性研究为了解大豆立枯丝核菌的致病机理、有效防治纹枯病奠定了基础。     

Nitrogen Fixation in Hybrids of White Clover (Trifolium repens L.) and Caucasian Clover (Trifolium ambiguum M. Bieb)

Hybrids between white clover (Trifolium repens L.) and Caucasian clover (or Kura clover, Trifolium ambiguum M. Bieb) are a potential route for the improvement of drought tolerance and persistence in white clover. However, to be agronomically viable they must show no significant reduction in their potential for nitrogen fixation relative to white clover. A comparative study of growth rate and nitrogen fixation was carried out in flowing solution culture without a supply of mineral nitrogen to the plants. The two parental species and two generations of backcross hybrids, with white clover as the recurrent parent, were assessed. The growth rate and N content of T. ambiguum were significantly lower than those of the other lines. However, dry matter production, nodule biomass per plant and rates of fixation were similar in second‐generation backcross plants and white clover. The results suggest that the agronomic potential of this novel germplasm is not compromised by limitations with respect to nitrogen fixation.     

Effects of water deficit and plant interaction on morphological growth parameters and yield of white clover (Trifolium repens L.) and ryegrass (Lolium perenne L.) mixtures

The effects of soil water deficit and interspecific plant interaction were studied on the dry matter (DM) yield of white clover and ryegrass and on the morphogenesis of white clover. Plants were grown either: (1) individually (no interaction); or in a mixture of equal plant numbers with either (2) just shoot interaction, or (3) both shoot+root interaction. Plants were subjected to soil water deficits corresponding to no (0 MPa), moderate (−0.5 MPa) or severe (−1.0 MPa) water deficit. Ryegrass had higher above- and below-ground DM yields than white clover. The above- and below-ground DM yield for ryegrass, and the above-ground DM yield, stolon growth and relative growth rate (RGR), and leaf appearance rate (LAR) for white clover decreased as soil water deficit increased. In shoot+root interaction at no and moderate soil water deficit levels, white clover had the highest proportion of above-ground growth in the leaf form (69%) and had, respectively, 11% and 32% more above-ground DM yield than when grown in just shoot interaction; ryegrass had, respectively, 20% and 25% more above-ground DM yield than ryegrass grown in just shoot interaction. In shoot+root interaction at severe soil water deficit, ryegrass had twice as much above-ground DM yield as white clover (3.50 g per plant versus 1.59 g per plant, respectively) and white clover had 60% less above-ground DM yield than when grown in just shoot interaction. In a soil column of restricted depth (30 cm) at no and moderate soil water deficit levels, remarkable increases in shoot biomass yield were observed for both white clover and ryegrass grown in shoot+root interaction. The increased shoot biomass yield of ryegrass can be attributed to benefits from white clover's N fixing ability, whereas the causes for increased white clover biomass yield need to be studied further. However, at severe soil water deficit, ryegrass had a competitive advantage over white clover when grown in shoot+root interaction. This was due to the larger root system of ryegrass and its ability to control transpirational losses more efficiently, thus prolonging its growth period compared with white clover.     

Introgression of reproductive traits from Trifolium nigrescens increases the seed yield of white clover (T. repens)

Interspecific hybrids between white clover and the annual, profuse flowering ball clover have been developed as a strategy to improve the potential seed yield of white clover. The seed yield and seed yield components of advanced white clover × ball clover hybrids were compared with white clover in replicated field experiments over two harvest years. The backcross 3 hybrid had more reproductive nodes per stolon than the control variety ‘AberHerald’ which was reflected in more inflorescences per unit area but inflorescences with fewer florets and seeds. The hybrid had a greater potential seed yield than the control variety in 2002 but not 2001. Backcross 3 hybrids have also been produced across the range of leaf size categories. Medium and large leaved hybrids produced significantly more inflorescences and a higher potential seed yield than control varieties of comparable leaf size in both harvest years. The small leaved hybrid was not significantly greater than the control variety ‘AberDale’ in either inflorescence production or seed yield.     

紫茎泽兰对两种牧草发芽的化感克异作用

研究了紫茎泽兰地上部分、根系及根际土壤不同浓度提取液对白三叶和多花黑麦草发芽的影响。研究结果表明：紫茎泽兰对白三叶和黑麦草种子萌芽存在化感克异现象，并且随浓度的增加，影响越大；相同条件下，对白三叶的影响强于多花黑麦草；低浓度对白三叶败育的影响较大，但对多花黑麦草几乎没有影响；紫茎泽兰根际土壤对两种牧草种子萌芽无明显的化感克异作用。     

果园种植三叶草对杂草群落及物种多样性的影响

为实现果园杂草生态控制,减少或避免使用化学除草剂。根据生态位先估和生态位竞争原理,设计间种豆科绿肥白三叶草和红三叶草两种杂草生态控制技术,同时设置清耕对照(CK),采用小样方多点取样连续两年调查果园杂草种群数量、生物量、平均株高等指标。结果表明：果园共有杂草13科28属34种;3个处理在4次调查时,对照杂草多度(Pi)高达1.001和1.000,间种白三叶草处理分别为0.755、0.664、1.001和0.945,间种红三叶草处理分别为0.986、0.889、0.982和0.992。种植白三叶处理果园在四次调查时期,杂草物种丰富度(S)和种群多样性(H)均大于对照,均匀度(J)在第一次调查时小于对照,优势集中性指数(C)均小于对照;间种红三叶草处理四次调查杂草总数量均低于对照。本研究表明间种白三叶草能改变果园杂草群落结构,有效控制杂草的生长。     

Symbiotic Nitrogen Fixation of White Clover in a Mixed Sward is not Limited by Height of Repeated Cutting

The aim of this study was to investigate whether symbiotic nitrogen fixation in white clover nodules limits nitrogen supply and hence clover growth by repeated defoliation at two cutting heights. Other possible factors governing symbiotic nitrogen fixation in the field were also elucidated. Using ¹⁵N, a 2-year field experiment including white clover ( Trifolium repens L. cv. Ladino) and perennial ryegrass ( Loliumperenne L. cv. Bastion) in monocultures and in mixtures was conducted in Eschikon, Switzerland. The effect of two cutting heights (4 cm and 10 cm above ground level) on the performance of symbiotic nitrogen fixation of white clover in the different sward-types was investigated. After each harvest, the plots were fertilized with 3 g N m^-2(equivalent to 30 kg N ha^-1 cut^-1 or 210 kg N ha^-1 year^-1). In both years, white clover grown in a mixture with grass received a significantly higher percentage of nitrogen from symbiotic fixation compared with clover grown in monoculture. This phenomenon is attributed to the strong competitiveness of ryegrass in soil nitrogen uptake. Consequently, white clover in the clover-ryegrass mixture was more dependent on symbiotic nitrogen fixation than that grown in monoculture. The cutting height did not preferentially influence symbiotic nitrogen fixation, as opposed to the uptake of mineral nitrogen from the soil. From this finding it is suggested that symbiotic nitrogen fixation did not limit the supply of nitrogen to clover and hence its growth. It is proposed that symbiotic nitrogen fixation in white clover is regulated by the demand for nitrogen rather than by the availability of carbohydrate reserves in the stolons. Symbiotic nitrogen fixation should thus be looked upon as an integrated plant growth factor and not as an isolated phenomenon.     

Effects of Competition upon the Productivity of White Clover-Perennial Ryegrass Mixtures. Analysis of and Interrelations between Characters

A diallel crossing programme amongst tour contrasting white clover varieties was used to generate material for studying the interrelationships amongst those characters which affect the productivity of white clover- perennial ryegrass mixtures under a cutting-only management regime. Such a regime favoured clover growth. All the clover characters exhibited strong positive correlations with mixture yield. However, this combination of clover characters did not promote growth of the grass companion. For this a low growing variety with a dense stolon network appeared preferable. Path analysis indicated that differences existed between the two companion grass varieties used for this experiment in their upon clover characters.     

Development of breeding populations from interspecific hybrids between Trifolium repens L. and T. occidentale Coombe

Trifolium occidentale is a diploid wild relative of T. repens (white clover) with adaptation to dry, saline coastal habitats. Transfer of drought and salt‐tolerant adaptive traits to white clover could be potentially valuable if interspecific hybridization can be achieved efficiently and leads to fertile hybrid populations. To achieve hybridization, 4x plants of T. occidentale were generated. Efficient techniques for generation of 4x plants and their identification using dry pollen shape are described. Interspecific 4x F₁ plants were achieved without embryo rescue. F₂ populations and first backcross hybrids to white clover were also efficiently achieved. Although male and female fertility were lower than in white clover, they were adequate to produce large amounts of seed from small numbers of inflorescences. Thus, early generation interspecific hybrid prebreeding populations can be readily developed, opening the way for transfer of traits from T. occidentale to white clover.     

干旱胁迫对白三叶光合参数日变化的影响

通过白三叶(Trifolium repens cv.Haifa)的盆栽试验,研究了连续干旱对白三叶叶片相对含水量、叶绿素含量和光合参数的影响。结果表明,当植株遭受较长时间干旱胁迫时,白三叶叶片相对含水量显著下降;净光合速率、蒸腾速率下降明显,日变化由双峰曲线转变为单峰曲线;水分利用效率仅在早晨有小幅升高,但仍以下降为主。气孔导度显著降低,而胞间CO2浓度显著升高,说明干旱胁迫下白三叶的光合作用降低的原因主要是非气孔限制的结果。     

Effects of Interspecific Competition on the Inheritance of Quantitative Traits in White Clover *)

Analysis of a half diallel cross among four white clover cultivars, grown as monocultures and in mixtures (duocultures) with two separate perennial rye-grass cultivars, confirmed that for stolon and leaf number a higher proportion of the genetic variance in duocultures was non-additive. For canopy height and dry weight, however, this proportion was less affected by inter-specific competition. An additive-dominance model of gene action sufficed for all four characters in monocultures, but in duocultures epis-tasis was just one of the factors complicating the genetic picture. This, coupled with short-term reversals in the direction of dominance, merely illustrates the complexity of breeding white clover cultivars. Possible future developments in the breeding of white clover are discussed in the light of these results.