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1.
Brachypodium distachyon (Bd) has established itself as an essential tool for comparative genomic studies in cereals and increasing attention is being paid to its potential as a model pathosystem. Eyespot and ramularia leaf spot (RLS) are important diseases of wheat, barley and other small‐grain cereals for which very little is known about the mechanisms of host resistance despite urgent requirements for plant breeders to develop resistant varieties. This work aimed to test the compatibility of interaction of two Bd accessions with the cereal pathogens Oculimacula spp. and Ramularia collo‐cygni, the causal agents of eyespot and RLS diseases, respectively. Results showed that both Bd accessions developed symptoms similar to those on the natural host for all pathogen species tested. Microscopy images demonstrated that R. collo‐cygni produced secondary conidia and both Oculimacula spp. formed characteristic infection structures on successive tissue layers. Visual disease assessment revealed that quantitative differences in disease severity exist between the two Bd accessions. The results presented here provide the first evidence that Bd is compatible with the main causal agents of eyespot and RLS diseases, and suggest that future functional genetic studies can be undertaken to investigate the mechanisms of eyespot and RLS disease resistance using Bd.  相似文献   

2.
Brachypodium distachyon (Bd) is increasingly being used as a model for cereal diseases and to study cereal root architecture. Rhizoctonia solani AG 8 is a necrotrophic root pathogen that infects wheat soon after germination resulting in reduced plant growth and yield loss. Genetic resistance to R. solani AG 8 is not available in commercial wheat cultivars, although some quantitative levels of resistance have previously been found in mutant lines and grass relatives. Resistance mechanisms in cereals remain unknown. The ability to use Bd as a model to study the wheat–R. solani AG 8 pathosystem was investigated. The results presented show that Bd is susceptible to R. solani AG 8 and that the pathogen infects both species to a similar degree, producing comparable disease symptoms. Root length reduction was the primary indicator of disease, with shoots also affected. The second objective was to develop a repeatable phenotyping method to screen Bd populations for resistance to R. solani AG 8. Results of a preliminary experiment provide evidence for variation in resistance between Bd inbred lines. This is the first report showing the potential of Bd as a model plant for discovery of quantitative genetic variation in resistance to a necrotrophic cereal root pathogen.  相似文献   

3.
Cereal cyst nematode (CCN) severely threatens wheat production in many regions of China. Cultivars susceptible to CCN are the main reason for its spread. This study was initiated to determine whether wheat cultivars conferring different resistance levels are the dominant determinants of CCN populations in the rhizospheric soil. Field experiments were conducted at two locations in Henan province, China, where high populations of Heterodera filipjevi or H. avenae have occurred, during the growing seasons of 2010/11 and 2011/12. Conventional enumeration of white female nematodes on the plant roots, reproductive factor (Rf) and a molecular diagnostic approach, PreDicta B test, a soil testing service based on a sensitive quantitative PCR technique, were used to determine the nematode populations in the rhizospheric soils of seven common wheat and durum wheat cultivars with different reactions to CCN. The resistant responses to CCN conferred by durum wheat Wascana and Wakooma and common wheat Madsen were effective against both H. filipjevi and H. avenae and resulted in significantly fewer nematodes (<5 females) on the roots, and lower Rf. Those cultivars were effective in limiting nematode propagation, resulting in fewer CCN eggs in their rhizospheric soils. Taikong 6 conferred moderate resistance (5–10 females) to both Heterodera species. Tianmin 668 only showed resistance to H. avenae. Aikang 58 and Wenmai 19 were susceptible to both CCN species, which facilitated increases in the nematode populations. These results demonstrate that the reactions to CCN of wheat genotypes have obvious impact on the propagation of nematodes.  相似文献   

4.
 近年来, 小麦孢囊线虫(cereal cyst nematodes, CCN:主要病原为燕麦孢囊线虫Heterodera avenae)对小麦(Triticum aestivum)的危害日益严重, 亟待探索新的生防途径。丛枝菌根真菌(arbuscular mycorrhizal fungi, AMF)作为环境功能生物, 对寄主植物具有生物药肥双重作用, 不仅能促进植物吸收利用养分, 而且能拮抗土传病原物、提高植物抗病性。本研究以AMF与CCN相互作用为切入点, 试图明确AMF与CCN相互作用关系, 并科学评价不同AMF抑制CCN、降低病害的效应。试验于温室盆栽条件下进行, 设接种AMF Gigaspora margarita(Gi.m)、Glomus mosseae(G.m)、Glomus intraradices(G.i)、Glomus versiforme(G.v)、Gi.m +G.m+G.i+G.v、CCN、CCN+Gi.m、CCN+G.m、CCN+G.i、CCN+G.v、CCN+Gi.m+G.m+ G.i+G.v和不接种对照(CK)共12个处理。结果表明, 接种AMF各处理均能降低小麦孢囊线虫侵染率、土壤中孢囊数和根内J2数量, 其中Gi.m处理抑制效果最大;CCN不同程度减少AMF侵入点数和产孢数量。Gi.m 和CCN+Gi.m处理的根内丛枝着生数量最多, 而后者根内的超氧化物歧化酶、苯丙氨酸解氨酶和过氧化氢酶活性显著高于其他处理、丙二醛含量则显著低于其他CCN+AM真菌处理。Gi.m和G.i处理的小麦株高、地上部干重高于其他处理;Gi.m 和CCN+Gi.m的处理的单穗重和单株产量均高于其他处理。表明AMF能不同程度拮抗CCN、促进小麦生长和提高产量, 其中, Gi.m是高效菌种。结论认为, AMF与CCN之间存在一定相互抑制作用, AMF能通过诱导植株防御反应拮抗CCN。  相似文献   

5.
安徽省萧县禾谷类孢囊线虫发生与分布规律   总被引：1，自引：0，他引：1  
为了解安徽省萧县不同自然条件和耕作制度下禾谷类孢囊线虫(cereal cyst nematode,CCN)发生和分布规律,2007-2010年间进行了田间调查.利用随机调查法采集土样360份,用漂浮法分离孢囊,计算雌虫、孢囊的数量以及CCN发生率;每取样点选30个孢囊测计卵密度,利用频度法分析卵密度发生量(egg density occurrencequantity,EDQ)频度,以及不同自然条件和耕作制度下EDQ差异.依据孢囊阴门锥形态和de-Man法鉴定种类.结果表明,萧县马井镇麦区线虫种类为Heterodera avenae,调查田块中87％田块发生CCN,中等海拔(31～40m)田块的EDQ显著高于低海拔(21～30m)的EDQ (P＜0.05);沙土地田块中,前茬为大豆时的EDQ显著高于前茬为玉米时的EDQ (P＜0.05),不同土壤类型田块EDQ差异不显著.本文首次揭示了安徽省萧县禾谷类孢囊线虫发生和分布规律,为当地相关部门制定防治措施提供了理论依据.  相似文献   

6.
小麦孢囊线虫病传播扩散途径研究初报   总被引：4，自引：0，他引：4  
为了明确小麦孢囊线虫病的扩散传播途径,调查病区农用机械、麦田翻耕后田间及其周边流水中小麦孢囊线虫的孢囊数量.结果表明,收割机、旋耕机和播种机上土样的孢囊检出率分别为27.1％、51.6％和44.0％,麦稻轮作的病田中,浪渣的孢囊检出率为58.3％,翻耕后麦田积水、沟渠和小河流中的孢囊检出率分别为33.3％、22.7％和7.7％.说明农业机械的跨区作业和水流是小麦孢囊线虫病传播、扩散的重要途径.  相似文献   

7.
小麦孢囊线虫病目前已在中国13个省(市区)的小麦种植区有发生与分布,其扩散与蔓延将直接威胁我国的粮食生产和经济安全,系统开展小麦孢囊线虫病的防治研究迫在眉睫.本文在大田条件下研究了5％涕灭威颗粒剂(aldicarb)、3％克百威颗粒剂(carbofuran)、5％硫线磷颗粒剂(cadusafos)、10％苯线磷颗粒剂(fenamiphos)和0.5％阿维菌素颗粒剂(abamectin)等5种杀线剂各3个不同剂量在小麦返青期使用对小麦孢囊线虫病的控制效果.结果表明,各药剂处理均对土壤中孢囊线虫的繁殖有明显的抑制作用,但各处理间的校正孢囊减退率差异并不显著;不同药剂处理后的小麦株高、单株根重和单株鲜重均优于对照,且小麦产量与对照相比均有增加.其中0.5％阿维菌素颗粒剂 30 kg/hm2处理后的校正孢囊减退率最大值为55.13％,且增产效果最好,增产率为18.54％;而0.5％阿维菌素颗粒剂60 kg/hm2处理后小麦株高平均值最大,为59.32 cm,促进植物生长的效果明显.由于0.5％阿维菌素颗粒剂能够明显抑制土壤中孢囊线虫的繁殖,同时促进植株生长并减少产量损失,因此,在小麦孢囊线虫重病田于小麦返青期施用0.5％阿维菌素颗粒剂30 kg/hm2进行土壤处理,可在一定程度上减轻小麦孢囊线虫造成的损失.  相似文献   

8.
This is the first genetic study reporting on the interaction and molecular mapping of resistance to the barley grass stripe rust pathogen (Puccinia striiformis f. sp. pseudo‐hordei, Psph) in common wheat. Seedlings of 638 wheat accessions were tested and it was determined that wheat is a near‐nonhost to Psph based on rare susceptibility observed in <2% of commercial cultivars and <5% of wheat landraces. As previously observed for P. striiformis f. sp. tritici (Pst), the Australian cultivar Teal was highly susceptible to Psph. In contrast, a selection of cv. Avocet carrying complementary resistance genes Yr73 and Yr74 (Avocet R; AvR) was resistant. The Teal × AvR (T/A) doubled haploid (DH) population was used to map resistance in AvR to Psph. Infection types on the T/A DH lines inoculated with Psph and Pst indicated that all DH lines carrying both Yr73 and Yr74 were also resistant to Psph; however, fewer DH lines were susceptible to Psph than expected, suggesting the resistance was more complex. QTL analysis using 9053 DArT‐Seq markers determined that resistance to Psph was polygenically inherited and mapped to chromosomes 3A, 3D, 4A and 5B. The 3DL and 5BL markers co‐located with Yr73 and Yr74, suggesting an overlap between host and non‐host resistance mechanisms.  相似文献   

9.
The spot blotch disease of wheat is caused by Bipolaris sorokiniana, which is an anamorph (teleomorph Cochliobolus sativus). The disease mainly occurs in warm, humid wheat‐growing regions, and the Eastern Gangetic Plains (EGP) of South Asia is a hotspot. Significant progress has been made in recent years in characterizing the host–pathogen interaction. The study of the pathogen's life cycle and diversity have been an active area of research. A number of resistance sources have also been identified, characterized and used for breeding. Although immunity has not been observed in any genotype, cultivars displaying a relatively high level of resistance have been developed and made available to farmers. Further progress will require regular use of marker‐assisted breeding, genomic selection, gene editing and transgenic interventions. This review summarizes the current state of knowledge about genetic and breeding efforts on the wheat–B. sorokiniana pathosystem and discusses ways in which emerging tools can be used for future research to understand the mechanism involved in infection and for developing cultivars exhibiting a high level of resistance.  相似文献   

10.
In plant–pathogen interactions, strong structural and biochemical barriers may induce a cascade of reactions in planta, leading to host resistance. The kinetic speed and amplitudes of these defence mechanisms may discriminate resistance from susceptibility to necrotrophic fungi. The infection processes of two Ascochyta lentis isolates (FT13037 and F13082) on the recently identified ascochyta blight (AB)‐resistant Lens orientalis genotype ILWL180 and two cultivated genotypes, ILL7537 (resistant) and ILL6002 (susceptible), were assessed. Using histopathological methods, significant differences in early behaviour of the isolates and the subsequent differential defence responses of the hosts were revealed. Irrespective of virulence, both isolates had significantly lower germination, shorter germ tubes and delayed appressorium formation on the resistant genotypes (ILWL180 and ILL7537) compared to the susceptible genotype (ILL6002); furthermore, these were more pronounced on genotype ILWL180 than on genotype ILL7537. Subsequently, host perception of pathogen entry led to the faster accumulation and notably higher amounts of reactive oxygen species and phenolic compounds at the penetration sites of the resistance genotypes ILWL180 and ILL7537. In contrast, genotype ILL6002 responded slowly to the A. lentis infection and reaffirmed previous gross disease symptomology reports as highly susceptible. Interestingly, quantification of H2O2 was markedly higher in ILWL180 particularly at 12 h post‐inoculation compared to ILL7537, potentially indicative of its superior resistance capability. Faster recognition of A. lentis is likely to be a major contribution to the superior resistance observed in genotype ILWL180 to the highly aggressive isolates of A. lentis assessed.  相似文献   

11.
R Aly 《Weed Research》2013,53(4):231-241
Parasitic plants have evolved various methods of invading host plants. Some invade aerial parts, whereas others invade the roots to obtain necessary nutrients for their development. Phelipanche and Orobanche spp. (broomrapes) and Cuscuta spp. (dodders) are holoparasitic plants that subsist on roots and shoots, respectively, of a variety of agricultural crops. These weeds are able to connect directly with the vascular system of the host, thereby acquiring the water, minerals and carbohydrates necessary for their own growth and reproduction. This exploitation by parasitic plants often causes severe losses in yield quality and quantity of host crops. The key to an effective means for controlling parasitic plants lies in the development of resistant crops, supported by an improved understanding of broomrape and dodder biology. The haustoria formed at the junctions of parasite and host open the way for translocation of a variety of molecules and macromolecules from the host to the parasite. At the same time, however, the haustoria also open opportunities for the development of methods to control parasitic plants. This review will summarise the current knowledge on translocation of siRNAs, mRNAs, viruses, sugars, proteins and herbicides from host to parasitic plants and the potential significance of such molecules to the parasite. Improved understanding of the molecular exchange between host plants and their parasites is expected to lead to the development of state‐of‐the‐art, effective approaches to parasitic weed management.  相似文献   

12.
Tree tomato, Solanum betaceum, is an Andean fruit crop previously shown to be attacked by Phytophthora andina in Ecuador and Colombia. Blight‐like symptoms were discovered on tree tomato plants in the central highlands of Peru in 2003 and shown to be caused by P. andina. Isolates of P. andina, collected from three different plantations in Peru over a 6‐year time span (2003–2008), were compared genetically with P. andina isolates from Colombia and Ecuador to test whether the pathogen population is geographically structured in the Andes. Restriction fragment length polymorphism (RFLP), mitochondrial DNA and simple sequence repeat (SSR) genetic markers, and mating type behaviour indicated that the Peruvian P. andina population from tree tomato is genetically distinct from populations infecting tree tomato in Colombia (CO‐1) and Ecuador (EC‐3, Ia, A1), but is more similar to the population infecting solanaceous hosts of the Anarrhichomenum complex (EC‐2, Ic, A2). Such geographic substructuring within this pathogen species could result from spatial isolation. Most strikingly, in contrast to the Ecuadorian and Colombian P. andina isolates from tree tomato, the Peruvian isolates have the A2 mating type. The presence of both mating types in the Andean population of P. andina attacking tree tomato indicates a risk of sexual reproduction and the presence of long‐lasting oospores in this pathosystem.  相似文献   

13.
Understanding pathogenic variation in plant pathogen populations is key for the development and use of host resistance for managing verticillium wilt diseases. A highly virulent defoliating (D) pathotype in Verticillium dahliae has previously been shown to occur only in one clonal lineage (lineage 1A). By contrast, no clear association has yet been shown for race 1 with clonal lineages. Race 1 carries the effector gene Ave1 and is avirulent on hosts that carry resistance gene Ve1 or its homologues. The hypothesis tested was that race 1 arose once in a single clonal lineage, which might be expected if V. dahliae acquired Ave1 by horizontal gene transfer from plants, as hypothesized previously. In a diverse sample of 195 V. dahliae isolates from nine clonal lineages, all race 1 isolates were present only in lineage 2A. Conversely, all lineage 2A isolates displayed the race 1 phenotype. Moreover, 900‐bp nucleotide sequences from Ave1 were identical among 27 lineage 2A isolates and identical to sequences from other V. dahliae race 1 isolates in GenBank. The finding of race 1 in a single clonal lineage, with identical Ave1 sequences, is consistent with the hypothesis that race 1 arose once in V. dahliae. Molecular markers and virulence assays also confirmed the well‐established finding that the D pathotype is found only in lineage 1A. Pathogenicity assays indicated that cotton and olive isolates of the D pathotype (lineage 1A) were highly virulent on cotton and olive, but had low virulence on tomato.  相似文献   

14.
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15.
Bacterial wilt caused by Ralstonia solanacearum is a serious disease of peanut (Arachis hypogaea) in China. However, the molecular basis of peanut resistance to R. solanacearum is poorly understood. Arachis duranensis, a wild diploid species of the genus Arachis, has been proven to be resistant to bacterial wilt, and thus holds valuable potential for understanding the mechanism of resistance to bacterial wilt and genetic improvement of peanut disease resistance. Here, suppression subtractive hybridization (SSH) and macroarray hybridization were employed to detect differentially expressed genes (DEGs) in the roots of A. duranensis after R. solanacearum inoculation. A total of 317 unique genes were obtained, 265 of which had homologues and functional annotations. KEGG analysis revealed that a large proportion of these unigenes are mainly involved in the biosynthesis of phytoalexins, particularly in the biosynthetic pathways of terpenoids and flavonoids. Subsequent real‐time polymerase chain reaction (PCR) analysis showed that the terpenoid and flavonoid synthesis‐related genes showed higher expression levels in a resistant genotype of A. duranensis than in a susceptible genotype, indicating that the terpenoids and flavonoids probably played a fundamental role in the resistance of A. duranensis to R. solanacearum. This study provides an overview of the gene expression profile in the roots of wild Arachis species in response to R. solanacearum infection. Moreover, the related candidate genes are also valuable for the further study of the molecular mechanisms of resistance to R. solanacearum.  相似文献   

16.
Plasmodiophora brassicae causes clubroot of crucifers. A quantitative PCR (qPCR)‐based protocol was developed to measure P. brassicae DNA in the roots of susceptible, intermediately susceptible, intermediately resistant and resistant Brassica hosts, and the non‐host wheat, at 5, 10, 15, 20 and 42 days post‐inoculation (dpi). The final reaction of each plant genotype was recorded as an index of disease at 42 dpi. Plasmodiophora brassicae DNA showed an increase in susceptible and moderately resistant hosts from 5 to 42 dpi, in contrast to a decrease in a highly resistant host and the non‐host wheat over the same period. Index of disease was significantly positively correlated with the amount of P. brassicae DNA in the roots at 5, 15, 20 and 42 dpi in one experiment, and at 10, 15, 20 and 42 dpi in a repeated experiment. Significant positive correlations also existed between the amounts of P. brassicae DNA in the roots at 42 dpi and those at 5, 10, 15 and 20 dpi in one experiment, and those at 10, 15 and 20 dpi in a repeated experiment. The results generated by the qPCR assay were validated by microscopic examination of roots inoculated with P. brassicae. The qPCR‐based protocol developed in this study allows for the accurate quantification of P. brassicae DNA in host root tissues as early as 5 dpi, and may serve as a useful tool to evaluate pathogen proliferation and development in the roots.  相似文献   

17.
Plant–fungal specificity between cucurbitaceous crops and Diaporthe sclerotioides, the causal agent of black root rot, was studied using cucumbers (Cucumis sativa), melons (Cucumis melo), pumpkins (Cucurbita maxima), watermelons (Citrullus lanatus) and bottlegourd (Lagenaria siceraria var. gourda). Twelve D. sclerotioides isolates from these cucurbit species were cross‐inoculated. The virulence of the isolates was evaluated as the area under the disease progress curve (AUDPC). All cucurbit species were susceptible to each isolate, but AUDPCs were significantly different among the hosts, with the order of greatest to least being melon, cucumber, watermelon, bottlegourd and finally, pumpkin. The infectiveness of isolates was assessed as the quantity of D. sclerotioides DNA detected in the hypocotyls of seedlings 2 weeks after inoculation using a real‐time PCR protocol. The fungal DNA quantities varied among the species in the same order as the AUDPCs. Whilst there were statistically significant correlations between the virulence and infectiveness of D. sclerotioides isolates in cucumbers, melons and bottlegourds, their coefficients of determination were not high (r2 < 0·6). Orthogonal contrasts indicated no specificity in either the fungal virulence or infectiveness between D. sclerotioides isolates and the cucurbit hosts from which these isolates originated. Thus, although the degree of host susceptibility to D. sclerotioides varies among cucurbit species, the absence of specificity to the host species in either virulence or infectiveness suggests the pathogen may spread via various cucurbit crops, irrespective of their original host species.  相似文献   

18.
Phytophthora infestans populations can differ in composition as a result of host specialization on tomato and potato hosts. In Great Britain many amateur gardeners grow outdoor tomatoes but there is little or no commercial tomato production outdoors. This study analysed isolates of P. infestans from British gardens with 12 multiplexed simple sequence repeat markers that are used to monitor the disease on commercial potato crops. Samples of P. infestans from tomato hosts were collected in 3 years and from potato in 1 year from across Great Britain. Seven previously unreported clonal lineages were detected in garden populations and higher frequencies of unique clonal lineages (28–40%) were present compared with populations from British commercial potato crops reported elsewhere. Garden populations had a lower proportion (11–48% less) of the most common lineages (13_A2 and 6_A1) that together made up at least 86% of the commercial potato populations during the sampling period. Host species accounted for only 2·0% of molecular variance detected between garden potato‐ and tomato‐hosted samples. No significant difference in clonal lineage composition was found between host species in Great Britain and this could be due to the whole P. infestans population overwintering on potato. British garden populations on both hosts were much more diverse than those on commercial potato crops; this finding may be influenced by less frequent fungicide use by gardeners and a higher diversity of unsprayed susceptible potato cultivars, enabling metalaxyl‐sensitive and less aggressive genotypes to survive in gardens.  相似文献   

19.
Compositions of Aspergillus flavus populations determine the extent to which crops become contaminated with aflatoxins. In the current study, influences of diverse crop hosts on competition among A. flavus isolates were quantified with pyrosequencing. Maize, cotton, soyabean and sorghum supported different levels of sporulation, but intraspecific differences in sporulation were not detected on any host. However, hosts differentially influenced competition during infection, allowing greater sporulation by some isolates and increased host tissue invasion by others. Furthermore, competitive interactions during host invasion did not predict isolate success during sporulation. Isolates were similarly competitive on maize and sorghum, the two most closely related hosts. Host‐specific influences on intraspecific competition may dictate compositions of A. flavus populations and, as a result, the severity of aflatoxin contamination. Host factors should be considered when designing and implementing aflatoxin management strategies including biocontrol with atoxigenic strains.  相似文献   

20.
Potato cyst nematodes (PCN), Globodera pallida and Globodera rostochiensis, are obligate parasites of solanaceous plants, causing severe losses in several potato growing areas throughout the world. To date, management of PCN is related to nematode population densities estimated as eggs per gram of soil, without considering the actual number of viable juveniles within the cysts. In classical nematology, the standard method to determine PCN viability is based on a staining assay, using Meldola's blue dye (MB) followed by microscopic visualization of MB‐treated nematodes. Although MB is considered to be reliable in staining embryonated juveniles within eggs and cysts, it is a time‐ and labour‐consuming assay. In the present work, a real‐time PCR (qPCR)‐based method combined with propidium monoazide (PMA), a photoreactive DNA‐intercalating dye, was developed for the quantification of viable PCN. This dye renders exposed DNA of dead cells unable to be amplified by PCR, and thus only DNA from viable/intact PCN juveniles is amplified and detected. The novelty of the present method lies in the simultaneous quantitative and qualitative estimation of viable PCN inocula using species‐specific primers and TaqMan probes. The PMA–qPCR viability method (v‐PCR) developed for the two Globodera species successfully discriminated dead from living specimens in heat‐treated samples and eggs in old and newly formed cysts. Interestingly, the detection of DNA from 34‐year‐old nematode cysts stored at room temperature was observed. In conclusion, the proposed v‐PCR method should prove to be very useful for the routine determination of PCN viability from field samples.  相似文献   

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