Components of Partial Resistance to Powdery Mildew in Wheat Mutants

Components of resistance to powdery mildew (latent period, pustule density and conidium production) were analysed on glasshouse-grown artificially inoculated plants of wheat mutants (n = 11) derived from either induced mutagenesis or adventitious regeneration of cv. Guardian. These mutants had previously been shown to be partially resistant to the disease in the field over a two-year period. Analyses were carried out at three stages of development: seedling, tillering and heading. None of the mutants exhibited a latent period significantly different from that of the susceptible parent Guardian at any stage of development tested. With respect to pustule density, one mutant (M61) was significantly more resistant than Guardian at all stages of development, two mutants (M19 and SC100) were more resistant at tillering and heading, and two (M156 and SC267) were more resistant only at heading. Significantly reduced conidium production per pustule (as a measure of pustule size) over a 24h period was observed on three mutants (M61, SC100 and SC231) at tillering and heading, while mutant SC68 exhibited this trait at heading only. On the basis of resistance components and relative grain yield in the presence of mildew, the eleven mutants were categorised into five categories. Tests for associations between field resistance score and components of resistance measured in the glasshouse, both measured at heading, revealed a significant positive correlation only between pustule density and field score. To assess the effects of combining different components (i.e. pyramiding different partial resistance genes), mutants were crossed. Transgressive segregation for at least one component was observed in the F₂ generation in crosses between mutants with complementary modes of action (i.e. involving different components of partial resistance), but not in cases where the parents exhibited the same component of resistance.     

A comparative study of resistance to powdery mildew in wild emmer wheat in the seedling and adult plant stage

An isometric virus was isolated from cucumber plants growing in a plastic house in Crete and showing stunting and bright yellow mosaic of the leaves. Based on host range, properties in crude sap, behaviour during purification, electron microscopy and serology, the virus was identified as an isolate of artichoke yellow ringspot nepovirus. Ecological data corroborate transmission of the virus via the soil.Samenvatting Uit komkommerplanten in plastic-foliekassen op Kreta werd een bolvormig virus geïsoleerd; de aangetaste komkommerplanten vertoonden dwerggroei en helder geel mozaïek op de bladeren. Gebaseerd op de resultaten verkregen uit onderzoek met het virus naar de waardplantenreeks, de eigenschappen in perssap, zuivering, elektronen-microscopie en serologie kon het virus worden geïdentificeerd als een strain van het artichoke yellow ringspot nepovirus. Waarnemingen op het gebied van de ecologie wijzen op overdracht van het virus via de grond.     

Chemical and Biological Treatments for Control of Gummy Stem Blight of Greenhouse Cucumbers

Experiments were conducted to determine the effects of chemical and biological treatments on gummy stem blight of cucumber caused by Didymella bryoniae in vitro and under greenhouse conditions. Eleven strains of Bacillus subtilis, strain AGB10 of B. cereus, and strain B8Fr of Enterobacter agglomerans produced antagonistic zone against D. bryoniae in vitro. Of four experiments conducted, the chemical treatments Nova,¹ kresoxim-methyl, and azoxystrobin controlled the disease in three experiments and the biological treatments E. agglomerans (B8Fr), B. subtilis (AGS-4), and lysozyme in one experiment when applied as sprays on lesions caused by D. bryoniae on cucumber plants under greenhouse conditions. Fruit rot of cucumber was significantly reduced when the fruit was treated with Nova or kresoxim-methyl. These results suggest the potential of azoxystrobin, kresoxim-methyl, E. agglomerans (B8Fr), and B. subtilis (AGS-4) applied post-inoculation to control gummy stem blight on greenhouse cucumbers.     

A method to test wheat leaves for their reactions to inoculation with Septoria species

The construction and application is described of a polystyrol humidity box in which wheat leaves, while continuing to function as parts of living plants, can be tested for their reactions toSeptoria spp. in an atmosphere nearly saturated with water, as is required for successful infection. The method is simple, accurate ans inexpensive.Samenvatting Voor dit doel is een z.g. vochtdoos geconstrueerd (Fig. 1A). Het te toetsen blad wordt daar doorheen geleid en in de doos geïnoculeerd met een druppel conidiën-suspensie van de schimmel. Onder het blad staat wat water in de doos (Fig. 1B). Na afsluiting ontstaat in de doos de hoge luchtvochtigheid van bijna 100% die nodig is voor de infectie. Dit wordt op deze wijze eenvoudig en goedkoop gerealiseerd. De bladeren die zo worden getoetst blijven onbeschadigd functioneren aan de plant. Na enkele dagen kan de doos worden geopend en kan de symptoom-ontwikkeling worden afgewacht en gevolgd (Fig. 3A, 3B en 4). De methode leent zich voor nauwkeurig werk en vereist zeer weinig infectiemateriaal. De Technische en Fysische Dienst voor de Landbouw (TFDL), Wageningen, ontwierp en construeerde een statief voor het gebruik van de vochtdozen in serie (Fig. 2).     

Development of a PCR-based diagnostic tool specific to wheat dwarf bunt,caused by <Emphasis Type="Italic">Tilletia controversa</Emphasis>

Wheat dwarf bunt, one of the important international quarantine diseases, is caused by Tilletia controversa. Tilletia caries is a close relative species of T. controversa and the teliospore morphology and genomic structure of T. caries are very similar to those of T. controversa. In order to distinguish between them, a random amplified polymorphic DNA (RAPD) primer-mediated asymmetric-PCR (RM-PCR) was developed to screen differential sequences between the two pathogens. By RM-PCR, a 1,322 bp DNA fragment (PR32) was selected from 18 T. controversa and 29 T. caries strains. The PR32 genes were specific for T. controversa and almost had no homology to T. caries or other fungi in the present database. With primers designed from PR32, all 18 T. controversa strains were amplified, but no bands appeared in 29 T. caries strains by classical PCR. To identify T. controversa rapidly and accurately, SYBR Green I and TaqMan probe real-time PCR were established based on PR32. With TaqMan Real-Time PCR, different T. controversa strains and T. caries strains were detected. The results showed that all T. controversa strains were amplified with Ct from 19–29 and amplified curves were obtained. In contrast, the amplification of all T. caries strains did not show any signals, without Ct and amplified curves. Moreover, the developed TaqMan real-time PCR was used to detect T. controversa from asymptomatic wheat tissues successfully.     

Compatible Biological and Chemical Control Systems for Rhizoctonia solani in Potato

A series of chemical and biological control agents were tested for compatibility with the Rhizoctonia-specific biocontrol fungus Verticillium biguttatum aimed at designing novel control strategies for black scurf (Rhizoctonia solani) and other tuber diseases in potato. The efficacy of chemicals, alone and in combination with V. biguttatum was tested in in vitro assays on nutrient agar plates, in bio-assays with minitubers and in the field. Generally, there were both antagonistic, neutral and additive interactions with V. biguttatum among the combinations tested; there were no indications for synergistic interactions. Broad-spectrum fungicides (azoxystrobin, chlorothalonil, thiabendazole) were fungitoxic to V. biguttatum as shown in in vitro assays, and hampered black scurf control by V. biguttatum in bio-assays. Oomycete-specific chemicals (cymoxanil and propamocarb) and various biocontrol strains (Gliocladium spp., Pseudomonas spp. and Trichoderma spp.) did not interfere with the growth of V. biguttatum on agar nutrient plates and did not affect black scurf control by V. biguttatum in co-applied treatments in the minituber bio-assay. Rhizoctonia-specific (pencycuron, flutalonil) fungicides co-applied with V. biguttatum showed additive effects on black scurf control. When combinations of V. biguttatum and cymoxanil or propamocarb were applied to immature potato tubers at green crop lifting, a reduction of both black scurf and Pythium- or Phytophthora-incited tuber rot was observed at harvest. In conclusion, the biocontrol fungus V. biguttatum is compatible with selected chemical control systems and may improve control efficacy in combination with Rhizoctonia-specific fungicides or may extend control spectrum in combination with Oomycete-specific fungicides.     

Use of carbendazim and carbendazim-resistant yeasts to create different yeast densities on wheat leaves for field studies on biological control

Phyllosphere yeasts may play an important role in suppressing necrotrophic pathogens. In a randomized block design, yeast densities on flag leaves and second leaves of field-grown wheat were left unchanged (D), or were lowered by sprayings with carbendazim (A), or were raised by sprayings with a mixture ofSporobolomyces roseus, Cryptococcus laurentii var.flavescens and nutrients (B), or with carbendazim, carbendazim-resistantS. roseus andC. laurentii var.flavescens and nutrients (C). The application of carbendazim to plots A and C would avoid a biased interference of carbendazim due to other effects than reducing the natural yeast population. Prolonged differences in yeast density would be reflected in differences in severity of diseases caused by carbendazim-insensitive necrotrophic pathogens.Both treatments B and C enhanced the yeast density about 10-fold at the beginning of leaf colonization, 2 to 3 weeks after leaf emergence. Untreated leaves (D), however, were rapidly leaves. Initially, the yeasts were suppressed by carbendazim (A). However, progressively the yeast population consisted of carbendazim-resistant strains which made the carbendazim sprayings ineffective. Therefore, the substantial differences in yeast density were of limited duration. The effect of the treatments on naturally occurringMycosphaerella graminicola (anam.Septoria tritici), Puccinia recondita f. sp.tritici and the total necrotic leaf area (D-value) is discussed.Samenvatting Fyllosfeergisten kunnen misschien een belangrijke rol spelen in de onderdrukking van necrotrofe pathogenen. In een blokkenproef werd de dichtheid van gisten op vlagbladeren en tweede bladeren niet beïvvloed (D) of verlaagd door bespuitingen met carbendazim (A), of verhoogd door bespuitingen met een mengsel van gisten (Sporobolomyces roseus enCryptococcus laurentii var.flavescens en voedingsstoffen (B), of met een mengsel van carbendazim, carbendazim-resistenteS. roseus enC. laurentii var.flavescens en voedingsstoffen (C). De grootste verschillen in dichtheden van de gistpopulaties werden verwacht tussen de behandelingen A en B of C. Door alle veldjes A en C met carbendazim te behandelen wordt een eenzijdig effect van carbendazim, berustend op andere eigenschappen dan de onderdrukking van de natuurlijke gistpopulatie, voorkomen. Langdurige verschillen in de populatiedichtheden van de gisten zouden weerspiegeld kunnen worden in verschillen in aantasting door carbendazimongevoelige necrotrofe pathogenen.Aan het begin van de bladkolonisatie door gisten, 2 tot 3 weken na het verschijnen van het blad, leidde zowel behandeling B als C tot, een 10-voudige verhoging van de gistdichtheid. De onbehandelde bladeren (D) werden echter spoedig door de van nature voorkomende gisten gekoloniseerd en het verschil tussen de onbehandelde en met gist bespoten bladeren werd snel kleiner. Aanvankelijk werden de gisten door carbendazim (A) onderdrukt. Geleidelijk bestond de gistpopulatie echter uit carbendazim-resistente stammen, zodat de carbendazim bespuitingen nauwelijks meer effect hadden. Hierdoor werden grote verschillen in gistdichtheden niet langdurig gerealiseerd. Het effect van de behandelingen op de natuurlijke infectie doorMycosphaerella graminicola (anam.Septoria tritici), Puccina recondita f. sp.tritici en op het totale dode bladoppervlak (D-waarde) wordt besproken.     

小麦条锈病菌致病类型G22-83及流行小种CYR32和CYR33在四川省小麦品种(系)上寄生适合度的测定及分析

为了解致病类型G22-83及流行小种CYR32和CYR33对四川省近年小麦生产品种和后备品种的寄生适合度,在田间分别将致病类型G22-83、流行小种CYR32和CYR33接种于四川省109个小麦品种(系),采用综合病情指数法测定3个供试菌株的相对寄生适合度。结果显示,致病类型G22-83、流行小种CYR32和CYR33的平均寄生适合度分别为0.1930、0.0560和0.0379,且前者显著高于后两者;流行小种CYR32和CYR33的平均相对寄生适合度有差异,但是差异不显著。致病类型G22-83、流行小种CYR32和CYR33在四川省109个小麦品种(系)上相对寄生适合度的中位数分别为0.0626、0.0000和0.0000,前者在四川省109个小麦品种(系)上相对寄生适合度的平均水平和波动程度均高于后两者。致病类型G22-83在四川省小麦生产品种和后备品种上的寄生适合度较高,在今后一段时间内可能成为该地区小麦条锈菌的优势菌系。     

Germination and appressorium formation of wheat leaf rust on susceptible,partially resistant and resistant wheat seedlings and on seedlings of other Gramineae

Germination and appressorium formation of wheat leaf rust urediospores were studied in two experiments. No consistent differences could be detected between 11 genotypes of wheat (Triticum aestivum), two of barley, one ofTriticum dicoccum, one ofT. dicoccoides, one ofT. boeoticum and one ofAegilops squarrosa. Host genotypes and non-hosts gave similar results, suggesting that the phases before penetration of the host leaf are not affected by the resistance mechanisms operating in hosts and non-host genotypes.Samenvatting Kieming en de vorming van appressoria is bestudeerd in twee experimenten. Er zijn geen systematische verschillen waargenomen tussen 11 genotypen van tarwe, twee van gerst, een vanTriticum dicoccum, een vanT. dicoccoides, een vanT. boeoticum en een vanAegilops squarrosa. Waard en niet-waard genotypen gaven overeenkomstige resultaten, dit suggereert dat de fasen voor penetratie van het gastheerblad niet beïnvloed worden door de resistentiemechanismen werkzaam in waard en niet-waard.     

Control of Stagonospora nodorum and Septoria tritici in Wheat by Pre-treatment with Drechslera teres, a Non-host Pathogen

A field study is described which explored the possibility of controlling Stagonospora nodorum and Septoria tritici on wheat using a barley pathogen, Drechslera teres. Pre-treatment of wheat cv. Hussar flag leaves with D. teres resulted in a significant reduction in disease caused by S. nodorum and S. tritici, resulting in a significant increase in grain yield. When cv. Brigadier leaves were treated with D. teres prior to inoculation with S. nodorum there was an initial increase in disease expression whilst D. teres had no effect on symptoms produced by S. tritici on cv. Brigadier. There was significantly less disease on leaves of cvs. Hussar and Brigadier pre-treated with D. teres prior to inoculation with an equal mixture of S. nodorum and S. tritici compared to plants pre-treated with water. It is concluded that D. teres and other non-host pathogens show potential as biological control agents for S. nodorum and S. tritici.     

Variation in sensitivity to fungicides which inhibit ergosterol biosynthesis in wheat powdery mildew

Fungicides which inhibit ergosterol biosynthesis have been in use for control of wheat powdery mildew (Erysiphe graminis f. sp.tritici) in the Netherlands since 1978. Mildew populations were tested for their variation in sensitivity to triadimefon from 1982 to 1984.In 1982 isolates from the province Limburg, with a triazole spray-regime history, were less sensitive to triadimefon than isolates from the provinces Gelderland and Noord-Brabant, where triazoles had not been used. In the following years isolates with reduced sensitivity were also detected in the latter provinces and other parts of the country. This spread correlates with the increased use of triazoles, both in frequency and space, from 1983 onwards. The reduced sensitivity can as a whole or in part be responsible for the decline in field performance of triazoles, observed during these years.Cross-sensitivity to the triazoles triadimefon and propiconazole was established, but not to triazoles and the morpholine fungicide fenpropimorph. Effectiveness of the latter compound was similar to all isolates from Limburg tested in 1984. Field performance of fenpropimorph, introduced in 1983, appeared to be normal. It is recommended to counteract further development of resistance by sequential use of fenpropimorph early in the season (May) and triazoles at the end (June–July).Samenvatting Fungiciden die de ergosterolbiosynthese remmen worden in Nederland sinds 1978 gebruikt bij de bestrijding van tarwemeeldauw (Erysiphe graminis f. sp.tritici) Meeldauwpopulaties werden getoetst op hun variatie in gevoeligheid voor triadimefon van 1982 tot 1984.In 1982 bleken isolaten afkomstig uit de provincie Limburg, waar voordien triazolen werden toegepast, minder gevoelig te zijn voor triadimefon dan isolaten uit de provincies Gelderland en Noord-Brabant, waar nog geen triazolen werden gebruikt. In de daaropvolgende jaren werden isolaten met een verminderde gevoeligheid ook in laatstgenoemde provincies en in andere delen van het land gevonden. Deze uitbreiding is gecorreleerd met een toename in het gebruik van triazolen vanaf 1983 in areaal en frequentie. De afname in gevoeligheid kan geheel of gedeeltelijk verantwoordelijk zijn voor de verminderde meeldauwwerking van triazolen die gedurende deze jaren werd waargenomen.Kruisgevoeligheid werd vastgesteld voor de triazolen triadimefon en propiconazool, maar niet voor triazolen en het morfoline-derivaat fenpropimorf. De werking van dit middel was tegen alle isolaten uit Limburg die in 1984 werden getoetst, gelijk. De meeldauwwerking van fenpropimorf, dat in 1983 werd geïntroduceerd, was normaal. Aanbevolen wordt om verdere resistentie-ontwikkeling tegen te gaan door afwisselend gebruik van fenpropimorf vroeg in het groeiseizoen (mei) en een triazool aan het eind (juni-juli).     

Identification of Resistance to Common Bacterial Blight Disease on Bean Genotypes Grown in Turkey

Common bacterial blight (CBB) in edible beans (Phaseolus vulgaris), incited Xanthomonas campestris pv. phaseoli, reduces bean yields and seed quality. The main objective of this study was to determine resistance to common bacterial blight in bean genotypes. Twenty-two bean genotypes grown in Turkey including common and snap bean cultivars/lines were collected from different parts of Turkey and tested for resistance against to Xanthomonas campestris pv. phaseoli strain MFD-11. All the common and snap bean lines/cultivars tested were moderately susceptible, susceptible or highly susceptible, except AG-7117 which was found resistant to Xanthomonas campestris pv. phaseoli. This is the first report of a resistance source in a common bean line (AG-7117) against Xanthomonas campestris pv. phaseoli.     

Differential Control of Head Blight Pathogens of Wheat by Fungicides and Consequences for Mycotoxin Contamination of Grain

Fusarium head blight of wheat is caused by a disease complex comprised of toxigenic pathogens, predominantly Fusarium spp., and a non-toxigenic pathogen Microdochium nivale, which causes symptoms visually indistinguishable from Fusarium and is often included as a causal agent of Fusarium head blight. Four field trials are reported here, including both naturally and artificially inoculated trials in which the effect of fungicide treatments were noted on colonisation by Fusarium and Microdochium, and on the production of deoxynivalenol (DON) mycotoxin. The pathogen populations were analysed with quantitative PCR and samples were tested for the presence of the mycotoxin DON. Application of fungicides to reduce Fusarium head blight gave a differential control of these fungi. Tebuconazole selectively controlled F. culmorum and F. avenaceum and reduced levels of DON, but showed little control of M. nivale. Application of azoxystrobin, however, selectively controlled M. nivale and allowed greater colonisation by toxigenic Fusarium species. This treatment also lead to increased levels of DON detected. nobreak Azoxystrobin application two days post-inoculation increased the production of DON mycotoxin per unit of pathogen in an artificially inoculated field trial. This result indicates the potential risk of increased DON contamination of grain following treatment with azoxystrobin to control head blight in susceptible wheat cultivars. This is the first study to show differential fungicidal control of mixed natural pathogen populations and artificial inoculations in field trials.     

Application of pathogen surveys,disease nurseries and varietal resistance characteristics in an IPM approach for the control of wheat yellow rust

The present paper presents the rationale for the use of pathogen surveys, inoculated and non-inoculated disease nurseries and varietal resistance characteristics in an integrated approach to control wheat yellow rust in Denmark. The non-inoculated disease observation plots, which gave valuable information about yellow rust at the year, site and variety level, served as the primary sample source for the pathogen survey revealing pathogen virulence dynamics. This survey was also the main source for isolates of new pathotypes, a prerequisite for the assessment of the resistance characteristics of varieties and breeding lines in inoculated nurseries, and the postulation of race-specific resistance genes. A simple grouping of varieties into four categories with respect to resistance to the current yellow rust population proved robust, and this grouping was used as a determinant in a web-based decision support system for pesticide applications in cereals, Crop Protection On-line (CPO). The interplay between the different research and survey activities in the integrated pest management (IPM) approach demonstrated the need for a coherent and long-term involvement at all stages from plant breeding to the official variety approval system, extension service and research in disease epidemiology and resistance genetics.     

甘肃省甘谷县小麦条锈菌群体遗传结构分析

为明确我国小麦条锈菌Puccinia striiformis f. sp. tritici主要越夏地区的群体遗传结构及演变情况,利用SSR荧光检测技术,对甘肃省甘谷县2013—2015年期间连续5个小麦生长季采集的141株小麦条锈菌单孢系基因组DNA进行分子标记分析,对小麦条锈菌季节亚群的遗传多样性进行分析。结果表明,甘谷地区小麦条锈菌的遗传多样性丰富,有效等位基因数为1.71,Shannon信息指数为0.66,2014年秋季(2014A)亚群体的基因型多样性低于其余亚群体。分子变异方差分析结果显示,小麦条锈菌季节亚群体间变异仅占21%,变异主要出现在亚群体内部,表明甘谷地区各季节亚群体间遗传分化水平差异较小,小麦条锈菌群体在一个小范围内基本能维持稳定状态。主坐标分析(PCoA)、遗传分化、基因流以及共享基因型分析均表明2014年秋季(2014A)亚群体的遗传结构与相邻季节亚群体存在一定差异,表明越夏过程对甘谷地区个别年份小麦条锈菌群体周年稳定性造成较大的影响,越冬过程对小麦条锈菌群体的影响相对较小,春季受外来菌源干扰的可能性较低。     

小麦白粉病菌对喹氧灵和苯菌酮的敏感基线及药剂的生物活性

采用离体叶段法,分别测定了从河北、河南、湖北、陕西和四川5省分离的53个小麦白粉病菌单孢菌株对苯菌酮和喹氧灵的敏感性,并分析了白粉病菌对三唑酮和苯菌酮以及喹氧灵之间的 交互抗性。结果表明:小麦白粉病菌群体对苯菌酮和喹氧灵的平均EC50值分别为(0.001 9±0.000 6) 和(0.013 1±0.002 0) mg/L,苯菌酮比喹氧灵具有更高的抑菌活性;小麦白粉病菌对三唑酮和苯菌酮与喹氧灵之间均不存在交互抗性(R2值分别为0.102 6和0.491 9);室内盆栽试验结果显示:接种前1 d和接种后1d施药,苯菌酮和喹氧灵对小麦白粉病的保护与治疗作用防效分别为92.21%、84.25%和82.43%、70.25%,表明这2种药剂不仅具有优异的保护作用,同时还具有较好的治疗作用。     

Field Response to Pratylenchus Thornei of a Wheat Line with the CreAet Gene for Resistance to Heterodera Avenae

The gene CreAet for resistance to Heterodera avenae, transferred from Aegilops triuncialis to Triticum aestivum introgression line TR-353, was assessed for responses to Pratylenchus thornei under field conditions. After 2.5 months, P. thornei infestation on TR-353 was similar to those on its progenitors (T. aestivum H10-15, T. turgidum H1-1 and A. triuncialis A-1) and on the cultivar Capa. After 5 months, TR-353 hosted significantly more P. thornei per plant than A. triuncialis, T. aestivum H10-15 or cultivar Rinconada, being very close to the maximum value obtained from T. turgidum. The final infestation of line TR-353 by H. avenae was significantly lower than on the other plants, except for A. triuncialis. In addition, at 2.5 months, the abundance of P. thornei on TR-353 was intermediate between the introgression wheat line H93-8 (Cre2 gene) and the cultivar Loros (Cre1 gene), but the final number of P. thornei per plant on TR-353 was significantly greater than on Loros. Line TR-353 was not able to control P. thornei in the field, but it confirmed its resistance to H. avenae, which was significantly lower than those due to Cre1 and Cre2 genes. No competition was observed between P. thornei and H. avenae populations on line TR-353 or A. triuncialis.     

云南小麦条锈菌群体对18个抗条锈近等基因系的毒性分析

为监测云南省小麦条锈菌群体毒性及小麦抗条锈基因的有效性动态,2016年采用18个抗条锈近等基因系鉴别寄主对云南省9个州市的136个小麦条锈菌株进行毒性分析,并按八进制法对小种进行命名。结果表明,云南省小麦条锈菌群体毒性丰富,共鉴定出64个小种类型,其中居于前2位的小种是550273和550073,出现频率分别为28.68%和11.76%,是本年度优势小种;其它小种出现频率均在4.41%以下,为次要小种。条锈菌群体对Yr5、Yr10、Yr15、Yr32四个抗条锈基因的毒力频率均为0,对Yr24、Yr Tr1、Yr8、Yr17四个抗条锈基因的毒力频率在0.74%~11.76%之间,表明这8个基因是云南省当前有效的抗条锈基因;对Yr27的毒力频率为52.94%,对Yr1、Yr6、Yr7、Yr9、Yr43、Yr44、Yr SP、Yr Exp2、Yr Tye九个抗条锈基因的毒力频率为77.94%~91.91%,表明这10个抗条锈基因的抗性已减缓或丧失,说明这些基因在云南省已失效。     

Emmer wheat, a potential new host of Tilletia indica

Two representative Italian emmer wheat (Triticum dicoccum) landraces, two selected lines and three improved emmer wheat cultivars, derived from crosses with durum wheat (Molisano landrace × ‘Simeto’), were tested for their susceptibility to Tilletia indica, the cause of Karnal bunt of wheat. Plants of emmer wheat were inoculated by injecting allantoid sporidial suspensions into the boot cavity of plants, just prior to ear emergence. A highly susceptible Indian spring wheat cultivar (Triticum aestivum) was used as a comparative control. At maturity of the plants, the seeds were harvested and assessed for incidence and severity of disease. All emmer wheat genotypes tested were infected but showed differing levels of susceptibility. The percentage of infected seeds for individual genotypes ranged from 5.4 to 75.0% compared with 99.1% for WL-711. The severity of infection was less in the old landraces, but it was higher in all the improved emmer wheat cultivars. In conclusion, Italian cultivars of emmer wheat were found to be highly susceptible to T. indica, and are potentially able to support the establishment of the pathogen.Authors L. Riccioni and M. Valvassori contributed equally to this work and should both be considered as first author.     

西藏小麦条锈菌群体结构与遗传多样性

为查明西藏小麦条锈菌Puccinia striiformis f. sp. tritici群体结构和遗传多样性,采用中国鉴别寄主和近等基因系鉴别寄主,以及竞争性等位基因特异性PCR-单核苷酸多态性（kompetitive al-lele specific PCR-single nucleotide polymorphism,KASP-SNP）分子标记对2017年采自西藏的150个小麦条锈菌菌系分别进行表型分析和基因型分析。表型分析结果显示,中国鉴别寄主将150个菌系区分为 12 个已知小种、6 个已知致病类型和 13 个未知致病类型,所有菌系均不能侵染中四和Triticum spelta album鉴别寄主。近等基因系鉴别寄主将150个菌系区分为88个毒性类型,这些毒性类型均不侵染携带抗性基因Yr5、Yr10或Yr15的品种。基因型分析结果显示,26对引物将150个菌系划分为73个基因型,表明西藏小麦条锈菌群体基因型丰富。基因流分析结果表明,波密县与洛扎县小麦条锈菌亚群体之间的基因流N_m最高,达5.86,米林县西部与波密县、洛扎县、巴宜县、米林县东部条锈菌亚群体之间的N_m较低,分别为0.25、0.34、0.42和0.67,表明西藏不同地区条锈菌群体之间基因交流强度差异较大。说明西藏作为我国小麦条锈病的独立流行区,条锈菌群体毒性结构复杂,遗传多样性高。