Quantitative relationships between inoculum of Melampsora larici-epitea and corresponding disease on Salix

Six Salix clones were inoculated with urediniospores of four isolates of Melampsora larici-epitea at five inoculum levels using a leaf-disc method. Disease reactions were recorded using a digital camera; the number and size of uredinia were examined using image analysis software; and spore yield per leaf disc was measured. In three Salix / Melampsora combinations, S.  ×  mollissima 'Q83'/Q1 (LET4); S. viminalis '78183'/V1 (LET1); and S.  ×  stipularis /V1, pustule numbers increased as inoculum density became higher. In the remainder, S. viminalis 'Mullatin'/V1; S.  ×  calodendron /DB (LET3); and S. burjatica 'Korso'/K (LR1), pustule numbers initially increased, then decreased as inoculum densities exceeded 140–360 spores per disc. Calculated infection efficiency ranged from 0·11 to 0·20 on the three willows inoculated with V1: 0·16–0·68 for S.  ×  calodendron /DB; 0·20–0·55 for 'Q83'/Q1; and 0·07–0·48 for Korso/K. In single-spore inoculations, up to 10% of spores produced single uredinia. Infection efficiency increased sharply between inoculum densities of 1–40 spores per leaf disc. Spore yield was more closely correlated to pustule area (accounting for 61·2% variance for the combined data) than to the number of pustules (42·7% variance). For spore yields in relation to pustule numbers, clone-specific individual lines having different intercepts and slopes fitted significantly better than either a single line for all the tested willows, or parallel lines fitted to each clone ( P  < 0·001). For spore yields in relation to pustule area, clone-specific individual parallel lines were significantly better than a single line ( P  < 0·001).     

Host-specific Genetic Composition of Melampsora larici-epitea Populations on Two Salix viminalis Varieties in a Mixture Trial

The genetic composition of Melampsora larici-epitea populations on two Salix viminalis varieties in monoculture and in mixed stands of Salix was studied using amplified fragment length polymorphism (AFLP). A total of 88 isolates collected from a large-scale mixture trial in Northern Ireland were analyzed. Genetic analyses were based on polymorphism for 63 AFLP markers. Differences in genetic composition of M. larici-epitea populations between the two S. viminalis varieties were indicated by all population characteristics used. In neighbor-joining analysis and principal component analysis, isolates from the same variety tended to group together. Analysis of molecular variance indicated a substantial differentiation between varieties (_ST = 0.20) and differences in genotypic composition was indicated by the non-random distribution of clonal isolates between the two varieties. The detection of host specialization with selectively neutral DNA markers was ascribed to predominant asexual reproduction. No differences in gene or genotypic diversity between M. larici-epitea populations in mixed and monoclonal stands were found for any of the two S. viminalis varieties.     

Pathotype Composition in Melampsora Epitea Populations Occurring on Willow (Salix) Grown in Mixed and Monoculture Plantations

Species/variety mixtures of Salix are used as a disease control strategy for rust (Melampsora epitea Thum. var. epitea) in short rotation coppice (SRC). Six LET (larici-epitea typica) pathotypes and two LR (larici-retusae) pathotypes of M. epitea var. epitea and also M. caprearum were detected in Northern Ireland plantations in 1994 and 1995. Three of these, LET7, LET8 and NI5 were detected in plantations for the first time. The predominant pathotype on most varieties was LET1. Logistic analysis showed that this pathotype was less prevalent on Salix X dasyclados Wimm. and more prevalent on S. viminalis L. 'Bowles Hybrid' than on S. viminalis '683'. The Shannon-Weaver Index of diversity indicated that there was greater pathotype diversity in mixtures than on the constituent varieties in monoculture. There was also a general trend of increasing diversity as the season progressed. The lowest pathotype diversity was recorded on S. viminalis 'Bowles Hybrid'. Pathotype predominance and diversity have an impact on the sustainability of the crop.     

Mendelian inheritance of rust resistance to Melampsora larici‐epitea in crosses between Salix sachalinensis and S. viminalis

Two F₁, two F₂ and two backcross (BC) full‐sib families of Salix sachalinensis × S. viminalis were tested for resistance to two pathotypes of Melampsora larici‐epitea in leaf‐disc inoculation experiments. Two single‐pustule isolates, VM and ST, belonging to pathotypes LET1 and LET5, respectively, were used in the tests. Disease was scored based on the number of uredinia, uredinial diameter and inoculum densities. Both F₁ families were completely resistant to both VM and ST. Resistance to VM segregated at a 9:6:1 ratio in the F₂ families and at a 1:2:1 ratio in the BC families, suggesting that two independently segregating genes controlled rust resistance, with resistance dominant over susceptibility. This also indicates incomplete dominance of the resistance alleles over the susceptibility to VM. For ST, the equivalent ratios were 3:1 and 1:1, showing that a single dominant gene was responsible for rust resistance. The broad sense heritabilities were >0·91 for uredinial diameter and 0·1–0·33 for the number of uredinia. There were significant overall correlations between data from inoculations with VM and those from inoculations with ST in the number of uredinia, uredinial diameter and disease scores (Spearman’s rank correlation coefficients = 0·31–0·75).     

Genetic Diversity in Relation to Sexual and Asexual Reproduction in Populations of Melampsora larici-epitea

Genetic diversity of Melampsora larici-epitea leaf rust from three cultivated stands of the willow Salix viminalis was studied using AFLP polymorphisms at 60 loci. One population was located in Northern Ireland and two in Sweden. Analysis of molecular variance (AMOVA) showed that most of the genetic variation was distributed on a fine scale within the field in all populations. Both Swedish populations displayed a very high genotypic diversity (normalized Shannon's indices of 0.95 and 1.00) and random association among loci. These results suggested that sexual reproduction had an important influence on the Swedish populations. The occurence of the alternate host (larch) adjacent to one of the Swedish rust populations did not affect the genetic diversity. However, severe rust attacks started earlier in the season in this population. The M. larici-epitea population in Northern Ireland was characterized by a low genotypic diversity (normalized Shannon's index = 0.54) and non-random association among loci was indicated by test of multilocus association and by pairwise tests among loci. These results suggested that asexual reproduction had a major effect on the genetic structure of this population, probably because of the overwintering of asexual spores and/or a population bottleneck associated with the annual sexual phase.     

Genetic Structure of Melampsora Epitea Populations in Swedish Salix Viminalis Plantations

Amplified fragment length polymorphism (AFLP) was used to study the genetic structure of populations of the willow leaf rust, Melampsora epitea, in Swedish willow plantations. In total, 197 isolates collected from Salix viminalis clones in three locations in Sweden were analysed. AFLP profiles based on 83 markers were used to compute genetic distances between pairs of individuals. High levels of gene and genotypic diversity were detected in all populations, with 96% of the AFLP loci being polymorphic and with normalized Shannon's diversity indices ranging from 0.977 to 1.0. Analysis of molecular variance (AMOVA) showed small significant differences among locations, although most of the molecular variability was found within locations (97.5%). Five isolates from one willow clone in one location differed markedly from the common pattern. When these five exceptional isolates were excluded, no significant differences among willow clones were found with AMOVA. Sexual reproduction and spore migration appear to be important factors for the population genetic structure of this pathogen.     

东北地区水稻种质资源抗纹枯病研究初报

为明确东北地区水稻种质资源对纹枯病的抗性, 收集了本地区水稻种质资源152份, 在苗期和分蘖期进行离体叶片接种; 在分蘖末期对79份种质进行了牙签嵌入法接种鉴定?结果表明, 供试的152份稻种资源中, 苗期离体叶片接种表现抗病的种质有2份, 中抗种质有42份?分蘖期离体叶片接种表现抗病的种质2份, 中抗种质8份; 进行牙签嵌入法接种鉴定的79份种质中, 表现中抗的种质16份?在苗期?分蘖期离体叶片接种?牙签嵌入法接种鉴定中均表现为中抗以上的种质仅有‘沈农9819’?分蘖期离体叶片接种和牙签嵌入接种法所获结果符合率最高, 为77.22%?     

Field Resistance to Willow Leaf Rust Melampsora epitea in Inter- and Intraspecific Hybrids of Salix viminalis and S. dasyclados

Families of interspecific hybrids between Salix dasyclados and S. viminalis, and intraspecific hybrids of the two species, were monitored for rust infection caused by Melampsora epitea during the years 1997–1999. The resistance of interspecific hybrids was compared to intraspecific pure species halfsibs. In addition, uredospores were sampled from the most infected interspecific hybrids to determine whether rust from interspecific hybrids differed from the rust spores that infected the pure species. The results from 1997 and 1999 showed that interspecific hybrids were more resistant than the intraspecific pure species, thus exhibiting a pattern of hybrid resistance. In 1998 the interspecific hybrids showed intermediate resistance compared to intraspecific pure species hybrids, i.e., an additive pattern of resistance. The rust sampled from the interspecific hybrids consisted of the same types of rust that infect the pure species. Comparisons of weather conditions prevailing during the three growing seasons indicated that these conditions might play a role in the infection pattern, in addition to the level of sensitivity to infection shown by the plants.     

甘蔗白叶病抗病性鉴定方法的建立与应用

为建立简便高效、致病性稳定和规范实用的甘蔗抗白叶病鉴定方法,推动甘蔗抗白叶病育种,本文从甘蔗材料处理与种植、接种液配制、接种方式、病情调查、分级标准制定等层面对甘蔗抗白叶病鉴定技术进行了系统研究与探索,首次优化创建了简便高效、致病性稳定和规范实用的甘蔗抗白叶病鉴定方法,即种苗喷雾接种法和生长期切茎接种法。种苗喷雾接种法：直接筛选甘蔗白叶病植原体蔗茎榨汁加10倍量无菌水配制接种液,接种液喷洒蔗种,塑料薄膜保湿,接种材料桶栽置于防虫温室培养,接种种植30 d开始调查病株率,按1~5级标准进行抗病性评价。切茎接种法：直接筛选甘蔗白叶病植原体蔗茎榨汁加10倍量无菌水配制接种液,鉴定材料桶栽置于防虫温室培养,株龄6月时切茎用移液枪将100 μL接种液滴入根部切口接种,接种种植20 d开始调查病株率,按1~5级标准进行抗病性评价。两种方法与自然传播相似,接种后发病显著、灵敏度高、重现性好,抗性鉴定结果与田间自然发病相吻合。通过两种接种方法和田间自然发病调查,鉴定明确了10个主栽品种对甘蔗白叶病抗病性,其抗病性真实、可靠,可作为今后甘蔗抗白叶病鉴定标准品种。     

剑麻抗斑马纹病鉴定技术研究

为了促进形成一套剑麻抗斑马纹病的鉴定技术,本研究对剑麻斑马纹病最适宜接种条件进行了探讨,并利用活体叶片接种和离体叶片接种两种方式,以抗性不同的8个剑麻种质为试验材料,在人工气候箱和恒温室中进行剑麻抗斑马纹病接种试验,并与大田抗病性进行比较.结果表明:针刺法接种,25～30℃保湿培养是该病最适宜的发病条件;两种接种方法都能比较准确地鉴定剑麻种质对斑马纹病的抗病性,而活体叶片接种较离体叶片接种鉴定抗病性更加准确.     

Development of an effective screening method for partial resistance to Alternaria brassicicola (dark leaf spot) in Brassica rapa

In order to develop a method to measure resistance to Alternaria brassicicola (cause of dark leaf spot disease) in Brassica rapa, the effects of inoculum concentration, leaf stage, leaf age and incubation temperature of inoculation on infection were studied under controlled conditions using several B. rapa genotypes. Three inoculation methods (cotyledon, detached leaf and seedling inoculation) were evaluated for this purpose. The detached leaf inoculation test was the most suitable for screening B. rapa genotypes because clear symptoms were observed on the leaves in less than 24 h, and there was a significant positive correlation between the results from the detached leaf inoculation test and the seedling inoculation test, an established method considered to yield reliable results. In addition, it was very easy to screen plants for resistance on a large scale and to maintain standard physical conditions using detached leaves. For successful infection, inoculum concentration should be adjusted to 5 × 10⁴ conidia ml⁻¹, and incubation temperature should be between 20 °C and 25 °C. The 3rd/4th true leaves from 30 day-old plants were optimal for inoculation. In a screening test using 52 cultivars of B. rapa, the detached leaf test effectively discriminated between various levels of partial resistance among cultivars. As a result, we identified two cultivars, viz Saori and Edononatsu, as highly resistant and five cultivars, viz Tokinashi Taisai, Yajima Kabu, Purara, Norin-F₁-Bekana and Tateiwa Kabu, as having borderline resistance.     

甘蔗花叶病抗病性鉴定接种新技术研究

研究了甘蔗花叶病抗病性鉴定的一种新技术—甘蔗生长期切茎接种法。此法和传统苗期手指摩擦接种法相比,接种后发病率极显著地高于手指摩擦接种法,且发病均匀、结果稳定,可以有效地区分不同甘蔗品种(材料)之间对病害的抗感性。比较11个甘蔗品种材料生长期切茎接种法和田间自然感病法对SrMV-HH1的抗性鉴定,结果表明:两种方法发病率呈正相关,且相关程度极密切,相关系数达0.9997,鉴定所得的抗病性和抗病等级结果完全一致,说明切茎接种法鉴定结果能真实反映甘蔗品种材料的自然抗感性;此外该方法简便实用、可操作性强、接种工效高,因此可以对大批量材料进行鉴定和筛选。     

玉米灰斑病抗性鉴定技术

对玉米灰斑病菌孢子产生、病菌接种和寄主抗病性测定技术的研究结果表明，应用玉米叶粉碳酸钙琼脂和玉米叶粉琼脂两种培养基，温度24～25℃，培养5天，病菌可大量产生分生孢子；于植株喇叭口期，用注射器将病菌孢子悬浮液注射于植株喇叭口中，获得了理想的发病效果；对20个玉米自交系注射接种鉴定结果表明，玉米自交系间抗病性差异明显，但未发现免疫自交系。     

河北省主推番茄品种抗黄化曲叶病鉴定与筛选初报

采用田间自然鉴定方法对河北省42个番茄生产主推品种进行抗番茄黄化曲叶病鉴定。结果表明,‘迪芬尼’、‘74 589’、‘佳西娜’、‘格利’、‘74 587’、‘荷兰6号’、‘Ty204’等7个品种田间表现明显抗番茄黄化曲叶病,发病率分别为0、0、0、1.35%、1.32%、0、1.76%。其余35个品种田间均表现明显感病,发病率最高的品种为‘鲁寿巨粉’,发病率达到99.22%,各品种发病率差异显著。     

Pathogenic variation in poplar rust <Emphasis Type="Italic">Melampsora larici-populina</Emphasis> from England

Using a leaf disc method, 19 isolates of the poplar rust, Melampsora larici-populina , and one isolate of M.populnea from England were inoculated on to 25 poplar clones belonging to Populus nigra and P.trichocarpa, and hybrids between P. deltoides and P. nigra, P. deltoidesand P. trichocarpa, P.tacamahaca and P.trichocarpa, and P. alba and P. tremula. Disease was scored based on the pustule area and inoculum density. In terms of whether sporulating uredinia formed, the 19 isolates showed seven different patterns to the tested poplar clones. The majority of the rust isolates infected P. nigra P3090 and Vereecken, P.nigra×P. deltoides Casale and Tasman, P. tacamahaca×trichocarpa 36 and Balsam Spire, and P.trichocarpa Blom. Populus trichocarpa×P. deltoides 69039/4 was infected by only three isolates collected from southern England. No visible symptoms appeared on P. alba ×P. tremulaTower and P.trichcarpa×P. deltoides×P. deltoides76028/5 in inoculations with M. larici-populina isolates. Populus alba×P.tremula Tower was infected only by M. populnea. When M. larici-populina isolates were tested using AFLP, no differences were found either between isolates from different geographical regions or between those having narrow spectrum of virulence and those showing wide spectrum of virulence on the tested clones. The results suggest that the UK rust populations possess virulences which were found in races E1, E2, E3 and E4 in continental Europe and that rust having virulence patterns similar to race E4 has occurred in UK poplar plantations since 1996.     

34份粗山羊草抗白粉病性鉴定及遗传分析

粗山羊草为小麦D基因组的供体,通过对来自不同产地的粗山羊草抗病性进行鉴定,用离体叶段接种方法接种12个小麦白粉病菌株(E02、E03、E05、E06、E07、E09、E11、E15、E18、E21、E23、E25),鉴定了34份不同产地的粗山羊草抗病性。结果表明:9份粗山羊草(Y170、Y186、Y189、Y192、Y201、Y206、Y212、Y214、Y215)对12个小麦白粉病菌株完全免疫,有3份山羊草(Y126、Y208、Y185)对12个菌株全部感病,其余的材料抗白粉病的部分菌株。田间全生育期用混合菌种鉴定粗山羊草抗性,其结果与离体叶鉴定的结论相一致。粗山羊草Y219与Y122杂交的后代的遗传分析发现抗病基因是1对显性基因控制;Y215与Ae43杂交后代的遗传分析表明抗病基因是1对隐性基因控制。     

青海青稞主栽品种(系)对条纹病和云纹病的抗性鉴定

本研究旨在明确青海青稞主栽品种和后备品种对条纹病和云纹病的抗性,以期为抗病育种及田间病害防治提供理论依据。试验采用田间自然病圃法,对青海主栽的30个青稞品种(系)进行了条纹病和云纹病田间抗性鉴定。结果表明,供试青稞品种(系)对2种病害的抗性存在显著差异,但缺乏免疫品种。对条纹病表现高抗的有13个品种(系),占鉴定总数的43.3%,其中主栽品种有3个,即‘门农1号’、‘昆仑13号’、‘巴青1号’。品系17发病率最低。对云纹病表现高抗的有品系1、品系2、品系6、品系17、品系28、RQKQ-3、RQKQ-5、RQKQ-6、RQKQ-7、RQKQ-8、‘门农1号’、‘互青2号’、‘北青6号’和‘昆仑10号’,共14个,其病情指数均在10以下;表现中抗的共有8个,分别为品系5、品系11、RQKQ-1、RQKQ-9、‘巴青1号’、‘北青3号’、‘北青7号’和‘昆仑13号’。     

青稞种质资源对条纹病的抗性鉴定

条纹病是青藏高原青稞生产上的重要种传病害之一, 常采用药剂拌种防治，但培育和推广抗病品种是防控该病害最经济有效的措施。为发掘抗条纹病的优良青稞种质资源, 本研究以田间鉴定和利用2个菌株室内人工接种鉴定相结合的方法, 对231份青稞种质资源进行了抗条纹病评价, 获得免疫性遗传资源材料20份, 高抗类型材料18份, 中抗类型材料44份, 分别占鉴定总资源数的8.7%、7.8%、19.1%;其他149份青稞资源材料对条纹病表现为感病, 其中36份材料为中度感病类型, 113份材料为高度感病类型, 感病材料占总鉴定材料的64.5%。     

辽宁花生主栽品种(系)对褐斑病和网斑病抗性鉴定

本研究旨在明确辽宁花生主栽品种(系)对花生褐斑病和网斑病的抗性,以期为抗病育种及田间病害防治提供理论依据。试验采用田间自然病圃法,对辽宁主栽的16个花生品种(系)进行了褐斑病和网斑病田间抗性鉴定。结果表明,供试花生品种(系)对两种叶部病害抗性存在显著差异,但缺乏免疫和高抗品种。对花生褐斑病抗性鉴定结果表明,‘阜花17’属抗病类型,‘鲁花11’、‘铁引花2号’、‘良青8号’、‘新花2号’和‘锦花15’属中抗类型,其余属高感或感病类型。对花生网斑病抗性鉴定结果显示:‘鲁花11’、‘铁引花2号’和‘白花生’属抗病类型,‘黑花生’、‘新花2号’、‘花育20’、‘锦花14’、‘新花1号’、‘锦花15’和‘良青8号’属中抗类型,其余属高感或感病类型。多数花生品种(系)对花生叶斑病综合抗性较差。     

An optimized screening method for identifying levels of resistance to Crinipellis perniciosa in cocoa (Theobroma cacao)

The effects of host age, leaf number, host type (clone or seedling), pathogen spore concentration and incubation time on inoculation with Crinipellis perniciosa (witches' broom disease of cocoa) were studied in greenhouse experiments using susceptible cocoa genotypes. Three methods of inoculation (agar-drop, water-drop and spray) were also tested. An optimized inoculation method was selected and tested for its repeatability as well as its ability to discriminate between various levels of resistance to C. perniciosa in cocoa. The optimized method (350 000 viable basidiospores per mL, 60 h incubation, agar-drop technique) produced 100% infection repeatedly, on both clonal and seedling plants of a susceptible genotype. Seedling age (2–12 months) and leaf number did not significantly affect the percentage of plants with symptoms or broom characteristics. This method discriminated effectively between the various levels of resistance in 14 cocoa genotypes and is recommended as an inoculation method to identify levels of resistance in germplasm collections. Symptom severity was shown to be a better measure of resistance than infection success.