柳杉毛虫空间分布型的研究

本文应用Twao、Taylor等的回归分析法和聚集度指标测定方法,研究了柳杉毛虫幼虫的空间分布型。结果表明幼虫的空间分布型为聚集型分布。柳杉毛虫在树冠上层占16．9％,中层占30．2％,下层占52．9％,且在上中下层的分布型均为聚集分布。     

河北省小麦冠腐病发生现状及病原菌初探

2013-2015年对河北省小麦主产区65县124点小麦冠腐病的田间症状和发生情况进行了调查。该病主要引起小麦茎基部变褐,灌浆期引起枯白穗,对产量影响较大。调查结果表明,小麦冠腐病发生主要集中在河北省中南部地区,而且发生程度呈逐年加重的趋势。2013年田间很少见由小麦冠腐病引起的枯白穗,2015年田间普遍发生枯白穗,严重发生地块局部枯白穗率达到20%~50%。病原菌分离结果显示,河北省中南部地区小麦冠腐病菌的分离频率较高,东北部麦区分离频率较低;经形态及分子生物学鉴定,河北省小麦冠腐病的病原菌主要为假禾谷镰刀菌和禾谷镰刀菌。     

The Pathogen of Crown Gall Disease on Flowering Cherry and its Sensitivity to Strain K1026

Six strains of crown gall bacteria were isolated from flowering cherry. It was revealed by Otten paper electrophoresis that of the six strains, only BYH18-4 possessed the octopine type Ti plasmid, the remainder having nopaline type Ti plasmid. BYH5-1 was identified by physiological and biochemical tests to be Agrobacterium tumefaciens (originally biovar 1). The other five were A. rhizogenes (originally biovar 2). It was demonstrated with Stonier's method of double layer medium that flowering cherry crown gall bacteria exhibited different sensitivities to agrocin produced by biocontrol strain K1026. Strain K1026 on greenhouse-grown sunflower seedlings exerted a relatively potent inhibitory action on flowering cherry crown gall bacteria. Artificial inoculation showed that K1026 produced 67–99% inhibition of flowering cherry crown gall disease, compared with the treatment of inoculation with crown gall bacteria only.     

不同地面覆盖对花椒冠层光能分布的影响

在陕西凤县大田生产条件下研究了种植三叶草、覆膜和覆秸秆3种地面覆盖方式对8 a生花椒林冠层光能分布的影响。结果表明,在树冠层,随高度升高,太阳总辐射、净辐射增加,地面反射辐射减小。各覆盖处理树冠下表面太阳总辐射与对照差异显著,覆膜、种植三叶草和覆秸秆林地的总辐射分别较对照低13.6%、6.4%和11.3%;树冠下表面接受的地面反射辐射差异最大,覆膜、种植三叶草和覆秸秆的林冠分别较对照高66.3%、21.4%和35.6%,树冠中部接受的地面反射辐射明显低于树冠下表面;不同覆盖处理的冠层净辐射垂直分布趋势基本一致,在冠层范围内,净辐射能的分布随高度升高呈指数规律增大。     

Mapping and Comparative Analysis of QTL for Crown Rust Resistance in an Italian x Perennial Ryegrass Population

ABSTRACT Crown rust (Puccinia coronata f. sp. lolli) is a serious fungal foliar disease of perennial ryegrass (Lolium perenne L.) and Italian ryegrass (L. multiflorum Lam.), which are important forage and turf species. A number of quantitative trait loci (QTL) for crown rust resistance previously were identified in perennial ryegrass under growth chamber or greenhouse conditions. In this study, we conducted a QTL mapping for crown rust resistance in a three-generation Italian x perennial ryegrass interspecific population under natural field conditions at two locations over 2 years. Through a comparative mapping analysis, we also investigated the syntenic relationships of previously known crown rust resistance genes in other ryegrass germplasms and oat, and genetic linkage between crown rust resistance QTL and three lignin genes: LpOMT1, LpCAD2, and LpCCR1. The interspecific mapping population of 156 progeny was developed from a cross between two Italian x perennial ryegrass hybrids, MFA and MFB. Because highly susceptible reactions to crown rust were observed from all perennial ryegrass clones, including two grandparental clones and eight clones from different pedigrees tested in this study, two grandparent clones from Italian ryegrass cv. Floregon appeared to be a source of the resistance. Two QTL on linkage groups (LGs) 2 and 7 in the resistant parent MFA map were detected consistently regardless of year and location. The others, specific to year and location, were located on LGs 3 and 6 in the susceptible parent MFB map. The QTL on LG2 was likely to correspond to those previously reported in three unrelated perennial ryegrass mapping populations; however, the other QTL on LGs 3, 6, and 7 were not. The QTL on LG7 was closely located in the syntenic genomic region where genes Pca cluster, Pcq2, Pc38, and Prq1b resistant to crown rust (P. coronata f. sp. avenae) in oat (Avena sativa L.) were previously identified. Similarly, the QTL on LG3 was found in a syntenic region with oat genes resistant to crown rust isolates PC54 and PC59. This indicates that the ortholoci for resistance genes to different formae speciales of crown rust might be present between two distantly related grass species, ryegrass and oat. In addition, we mapped four restriction fragment length polymorphism loci for three key ryegrass lignin genes encoding caffeic acid-O-methyltransferase, cinnamyl alcohol dehydrogenase, and cinnamoyl CoA-reductase on LG7. These loci were within a range of 8 to 17 centimorgans from the QTL on LG7, suggesting no tight linkage between them. The putative ortholoci for those lignin biosynthesis genes were identified on segments of rice (Oryza sativa L.) chromosomes 6 and 8, which are the counterparts of ryegrass LG7. Results from the current study facilitate understanding of crown rust resistance and its relationship with lignin biosynthesis, and also will benefit ryegrass breeders for improving crown rust resistance through marker-assisted selection.     

The relative importance of Colletotrichum musae as a crown-rot pathogen on Windward Island bananas

Low numbers of conidia of Colletotrichum musae (10–50) applied directly to the surface of freshly cut banana crowns caused extensive rot development. At least 20 times more conidia of Fusarium pallidoroseum were required to cause comparable levels of crown rot. Examination of the relative pathogenicity of the major fungal species involved in development of crown rot, C. musae, F. pallidoroseum, Fusarium moniliforme, F. moniliforme var. subglutinans , and Botryodiplodia theobromae , using a standard inoculum of 2 × 10³ conidia per crown, showed C. musae to be the most aggressive species. C. musae produced a distinctive soft, dry fibrous rot while the fruit was still green, and on ripening further rotting, softening and blackening of crown tissues occurred. The other crown-rot pathogens tested did not rot green fruit.
Fruit inoculated with C. musae and held for 0, 1, 2 and 3 days at ambient temperature before ripening sustained increasingly more severe crown rot. C. musae was isolated with increasing frequency from rotting tissue the longer the period under ambient conditions. Crowns which had been inoculated with F. pallidoroseum and held for a comparable period did not display such extensive rot development although the pathogen was very frequently isolated from the tissue.     

Rhamnus lycioides in Tunisia is a new aecial host of oat crown rust

Puccinia coronata was not previously described on Rhamnus spp. in Tunisia. Three sites in the northwest of Tunisia, where Rhamnus is reported to be abundant, were surveyed for the presence of pycnia and aecia of oat crown rust caused by Puccinia coronata f. sp. avenae. Two Rhamnus species (R. lycioides and R. alaternus) were encountered in the sites. Pycnia with viable pycniospores and aecia with viable aeciospores were found on R. lycioides. However, no characteristic structures of crown rust were found on R. alaternus. Aeciospores collected from leaves of R. lycioides were used to inoculate oat plants usually susceptible to oat crown rust. Typical uredinia containing oat crown rust urediniospores appeared on the leaves of these plants. Moreover, the sixteen Pc-gene differential oat lines, used by oat researchers to study the virulence pattern in oat crown rust populations, were artificially inoculated with aeciospores from R. lycioides. These inoculated lines showed resistance/susceptibility similar to the registered resistance level of these lines to crown rust under field conditions in Tunisia. These results indicate that R. lycioides, a common and endemic part of the vegetation in the northwest of Tunisia, is a new aecial host of oat crown rust. The aeciospores produced on this forest plant could constitute the source of the virulence diversity already detected via the Pc-gene line trials.     

Control of crown rot (Phytophthora cactorum) of apple trees with the systemic fungicides metalaxyl and fosetyl-aluminium

Four fungicides were evaluated as combined soil drench and trunk treatments for the control of crown rot, caused by Phytophthora cactorum, in naturally infected apple trees. In a 3-year preliminary study, metalaxyl at 1 and fosetyl-aluminium at 8 g a. i. per tree, applied twice a year, prevented death of infected trees showing only initial, but not more severe, symptoms of crown rot. This indicates that these fungicides have the ability to arrest further symptom development in naturally infected trees if they are treated as soon as symptoms appear. Healthy trees remained free of infection if they were treated with these fungicides, suggesting a preventative action. Repeated bi-annual application of metalaxyl or fosetyl-aluminium should be sufficient to prevent the loss of trees to crown rot.     

A high-throughput glasshouse bioassay to detect crown rot resistance in wheat germplasm

A high-throughput and reliable seedling bioassay to screen wheat germplasm for crown rot resistance was developed. Single wheat seedlings were grown in square seedling punnets in a glasshouse and inoculated with a monoconidial Fusarium pseudograminearum isolate 10 days after emergence. The punnets were laid horizontally on their side and a 10- µ L inoculum droplet placed on the stem base. Seedlings were incubated at near-saturated relative humidity, and crown rot severity was assessed 35 days after inoculation. Studies on the duration of incubation period, inoculum concentration and temperature were carried out to optimize these parameters. Seedling growth at 25/15(±5)°C in a glasshouse and 48-h incubation at near-saturated RH in darkness gave the best results. When crown rot resistance rankings of 16 Australian cultivars from the bioassay were compared with their field performance, Spearman's rank correlation coefficient was highly significant. This indicated that the seedling bioassay mimicked field resistance to crown rot in adult plants. A bootstrap resampling analysis showed little or no improvement in the coefficient of variation with an increasing number of replications, indicating a high level of precision and reproducibility. By detecting small but consistent differences in crown rot severity, the bioassay proved effective in large-scale screening for partial resistance: already over 1400 wheat genotypes have been screened. The high degree of precision makes this an invaluable tool in the understanding of pathogen aggressiveness, host specialization and parasitic fitness.     

Heat shock-induced resistance in strawberry against crown rot fungus Colletotrichum gloeosporioides

This present study investigated the effects of heat shock treatments in strawberry seedlings against crown rot caused by Colletotrichum gloeosporioides. Heat shock treatment at 50 °C for 20 s reduced the disease index of strawberry crown rot and increased chitinase 2-1 gene expression as well as free salycilic acid accumulation. Heat shock treatment did not reduce mycelial growth of C. gloeosporioides. BIT(2-benzisothiazol-3(2H)-one,1,1-dioxide) treatment could not protect strawberry seedlings against crown rot disease. This finding suggests that heat shock induces strawberry resistance against Colletotrichum crown rot and assumes that mechanisms other than SAR probably mediated the protective effect of heat shock-induced resistance.     

Incidence and severity of dieback in birch plantings associated with Anisogramma virgultorum and Marssonina betulae in Scotland

Betula pendula and B. pubescens were surveyed at nine Scottish Woodland Grant Scheme (WGS) sites in 2004 to assess the incidence and severity of two fungal pathogens, Anisogramma virgultorum and Marssonina betulae , and their association with crown dieback. Of the surveyed trees, 47% had at least 40% crown dieback, with B. pendula more severely affected than B. pubescens at most sites. Overall, 57% of surveyed birch trees had A. virgultorum and 28% had M. betulae , with the incidence of trees infected with both species varying among sites. Incidence and severity of A. virgultorum were greater on B. pubescens than on B. pendula , whereas the reverse was true for M. betulae. The relationship between incidence of M. betulae foliar disease and sunken cankers was significant, with 83% of M. betulae -infected trees having these cankers. The presence of M. betulae foliar disease resulted in a greater percentage of crown dieback compared with non-infected trees in both birch species, whereas the presence of A. virgultorum caused greater crown dieback in B. pubescens only. Across all sites and both birch species, as severity of infection with either A. virgultorum or sunken cankers increased, so did the severity of crown dieback. This study showed that A. virgultorum and M. betulae appear to contribute significantly to birch dieback at the nine sites surveyed.     

河西灌区马铃薯茎基腐病的发生规律与防治技术研究

本文首次报道马铃薯茎基腐病在田间表现为立枯型、萎蔫型、根腐型、黄化型4种症状类型,一般在苗期至现蕾期、开花期至结薯期为发病高峰期;明确了河西灌区种植的大多数品种对茎基腐病无明显抗性;发病程度与多种因素有关,灰钙土发病较重,其次为壤土,沙土发病较轻;土壤pH与含水量较高发病重;植株密度较高发病重;连作年限越长发病越重;与油菜、茄科蔬菜连作发病较重;高温有利于该病发生;经药剂种薯、土壤、灌根处理表明：以代森锰锌、菌核净和敌磺钠种薯和土壤处理,代森锰锌、井•1亿活枯草芽孢菌、菌核净灌根处理,防效达50.3%～65.9%。     

Use of the Genetically Engineered Agrobacterium Strain K1026 for Biological Control of Crown Gall

Strain K84 of Agrobacterium (formerly called A. radiobacter) has been a successful biocontrol agent of crown gall disease for almost 30 years all over the world. In spite of its demonstrated efficiency, the most important risk of failure when using strain K84 is the possibility of transfer of plasmid pAgK84 to pathogenic Agrobacterium strains. pAgK84 codifies production of and immunity to agrocin 84, the main factor involved in crown gall biocontrol by strain K84. Then, a second generation of strain K84 was obtained and the genetically engineered strain was called K1026. It contains a deletion in the transfer region of pAgK84. To date, a considerable number of studies have been performed to compare both strains in its ability to control crown gall, plasmid transfer, antibiotic production, root colonization and survival in the rhizosphere. The aim of this review is to discuss all this comparative available information which advises that strain K1026 should be used as a biopesticide to safeguard biocontrol of crown gall wherever strain K84 is employed.     

Control of crown gall in Swiss apple nurseries1

Experiments to control crown gall, caused by Agrobacterium tumefaciens, were carried out in an apple-rootstock nursery. One-year-old apple rootstocks (M 9) were dipped in different concentrations of several copper compounds before planting. The compounds were used alone or in mixtures with clay or glue. Good control of crown gall was obtained with Copac E cuprammonium (ammoniacal cupric sulphate) and with copper oxychloride in clay slurries or mixed with glue. Although treatment with 2-methoxyethylmercury chloride prevented the development of crown gall, phytotoxicity was severe.     

土壤杆菌K1026对樱桃冠瘿病病原菌的抑制作用及田间防治效果

由致病性根癌土壤杆菌Agrobacteriumspp.侵染引起的根癌病对樱桃等果树生产造成严重的影响。利用双层平板、胡萝卜圆盘法和接种指示植物番茄等方法验证了澳洲生防菌株K1026对2种不同原生物型樱桃冠瘿病病原菌的抑制作用;检测了不同接种时间对病原菌侵染产生瘤状组织的影响,结果显示提前或者在病原菌接种后20h内接种K1026可抑制胡萝卜产生瘤状组织;研究了K1026对大樱桃根癌病的作用机制是产生土壤杆菌素和竞争附着位点;田间试验表明K1026蘸根处理,对‘中国樱桃’株系冠瘿病的防治效果达81.61%,使发病率降低至18.13%。     

胡杨融雪漏斗现象及生态作用

杜加依林春季积雪融化时,存在以胡杨根部为中心的融雪漏斗。通过调查比较胡杨林冠和融雪漏斗的形状相关性,测定漏斗区与林隙地表区温度的不同,分析漏斗区与林隙区表层土壤有机质和总盐的差异。结果表明：胡杨林冠下由于主干的存在,使林冠下土壤能得到较多的太阳辐射能量,并且林冠下枯落物的富集作用和胡杨的＂肥岛＂效应,使林冠下土壤的有机...     

The effect of three irrigation practices on phytophthora crown and root rot of apple trees under field conditions

The effect of microjet, drip, and two durations of sprinkler irrigation systems on phytophthora crown and root rot of apple trees was examined under field conditions. This eight year study indicates that crown and root rot caused byPhytophthora cactorum was most severe where young MM. 106 rootstock trees were watered by microjet irrigation for 2.3 h each day. There was no difference in infection byP. cactorum when trees were irrigated either by drip or sprinkler irrigation systems. The MM.106 apple rootstock trees watered by drip irrigation for 2.6 h each day were least affected by phytophthora crown and root rot.     

Assessment of canopy and ground deposits of fenitrothion following aerial and ground application in a northern ontario forest

Spray deposit patterns on simulated and live foliage of balsam fir and white birch were determined at different heights and at periphery and interior locations of the tree crown, following aerial and ground applications of fenitrothion formulations over a boreal forest near Searchmont, Ontario. Droplet size spectra and AI deposits were assessed at ground level with ‘Kromekote’ card/glass plate units. Aerial application was made with a Cessna 188 aircraft fitted with ‘Micronair’ AU3000 atomizers. For ground application, a ‘Soloport’ 423 backpack mistblower fitted with an extension tube and a diffuser nozzle at the tip was used. Deposit data on the ground samplers indicated significantly larger droplets and greater deposits from the aerial spray trial than from the mistblower treatment. However, foliar deposits at tree canopy level were only slightly higher in the former trial than in the latter. Analysis of spray deposits on simulated and live fir foliage showed definite gradients in deposit levels, decreasing from top to bottom crown, and from periphery to inner tree crown. In the birch tree crown, such gradients were not observed. The simulated leaves generally acted as better collectors of spray droplets than the natural leaves. The overall mean deposit values, expressed in ng cm^?2, showed a wide variation, although there was generally a close relationship between the deposits on the simulated and natural surfaces.     

Aetiology and toxigenicity of Fusarium graminearum and F. pseudograminearum causing crown rot and head blight in Australia under natural and artificial infection

Globally fusarium head blight (FHB) of wheat is predominantly caused by Fusarium graminearum (FG) and crown rot (FCR) by F. pseudograminearum (FP). While both FG and FP can cause FHB in Australia, the reasons why the morphologically and culturally similar FG is not a major FCR pathogen has remained elusive. Using aetiology and toxigenicity, this study clarifies the contrasting roles of FG and FP in FCR and FHB in Australia. Naturally infected wheat from 42 sites during 2010 FHB epidemics, and wheat inoculated with either pathogen to induce FCR or FHB at three field plantings in 2011, were used to determine pathogen prevalence and deoxynivalenol (DON) content of the crown, stem base, stem top, rachis and grain. As the primary aetiological agent, FP prevalence in the crown correlated with FCR severity while FG in grain and/or the rachis correlated with FHB severity. FG was an effective colonizer of the crown and stem base but colonization was symptomless. DON content was linked to FG biomass in all tissues except the crown, where FP biomass was the main contributor. Of the 30 measures derived to analyse pathogen fitness in 2011, 10 described the superior fitness of FG for FHB; six defined FP fitness for FHB including inoculum dispersal; and eight defined FCR fitness of both FP and FG. FG had superior FHB fitness but weak saprophytic survival may have undermined its FCR fitness.     

塔里木盆地南缘不同生境盐生草种群分布特征及地上生物量初步估测

本文对不同生境盐生草(Halogeton glomeratus)种群分布特征及地上生物量做了初步分析。结果表明:(1)盐生草种群格局均为成群分布。(2)不同生境盐生草地上生物量不同:策勒-洛浦公路北侧最高达40.34±2.59g.m-2,昆仑山北坡-恰哈乡其次达24.91±1.80g.m-2,策勒-洛浦公路南侧最低为3.65±1.33g.m-2。(3)各样地地上生物量最优回归方程分别为:策勒-洛浦公路南侧Y=7.07e0.0002x;策勒-洛浦公路北侧Y=0.006x1.17;昆仑山北坡-恰哈乡Y=16.1550.0011x,各模型检验的平均拟合率都在90%以上,预测精度较可靠。