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1.
Real-time PCR protocols were developed to detect and discriminate 11 anastomosis groups (AGs) of Rhizoctonia solani using ribosomal internal transcribed spacer (ITS) regions (AG-1-IA, AG-1-IC, AG-2-1, AG-2-2, AG-4HGI+II, AG-4HGIII, AG-8) or β-tubulin (AG-3, AG-4HGII, AG-5 and AG-9) sequences. All real-time assays were target group specific, except AG-2-2, which showed a weak cross-reaction with AG-2tabac. In addition, methods were developed for the high throughput extraction of DNA from soil and compost samples. The DNA extraction method was used with the AG-2-1 assay and shown to be quantitative with a detection threshold of 10−7 g of R. solani per g of soil. A similar DNA extraction efficiency was observed for samples from three contrasting soil types. The developed methods were then used to investigate the spatial distribution of R. solani AG-2-1 in field soils. Soil from shallow depths of a field planted with Brassica oleracea tested positive for R. solani AG-2-1 more frequently than soil collected from greater depths. Quantification of R. solani inoculum in field samples proved challenging due to low levels of inoculum in naturally occurring soils. The potential uses of real-time PCR and DNA extraction protocols to investigate the epidemiology of R. solani are discussed.  相似文献   

2.
Rhizoctonia spp. cause substantial yield losses in direct-seeded cereal crops compared with conventional tillage. To investigate the mechanisms behind this increased disease, soils from tilled or direct-seeded fields were inoculated with Rhizoctonia spp. at population densities from 0.8 to 250 propagules per gram and planted with barley (Hordeum vulgare). The incidence and severity of disease did not differ between soils with different tillage histories. Both R. solani AG-8 and R. oryzae stunted plants at high inoculum densities, with the latter causing pre-emergence damping-off. High inoculum densities of both species stimulated early production of crown roots in barley seedlings. Intact soil cores from these same tilled and direct-seeded fields were used to evaluate the growth of Rhizoctonia spp. from colonized oat seeds. Growth of R. oryzae was not affected by previous tillage history. However, R. solani AG-8 grew more rapidly through soil from a long-term direct-seeded field compared to tilled soils. The differential response between these two experiments (mixed, homogenized soil versus intact soil) suggests that soil structure plays a major role in the proliferation of R. solani AG-8 through soils with different tillage histories.  相似文献   

3.
小麦纹枯病菌核糖体基因内转录区序列比较   总被引：13，自引：1，他引：12  
 对7个从江苏省小麦纹枯病样本分离到的丝核菌菌株,进行形态学鉴定、融合群分类和致病性测定,提取病菌的DNA,采用通用引物ITS1(TCC GTA GGT GAA CCT GCG G)和ITS4(TCC TCC GCT TAT TGA TAT GC),扩增病菌的rDNA内转录区(ITS),并对扩增产物进行了测序.用这些序列在NCBI中进行BLAST分析,得到与这些菌株亲缘关系最近的菌株序列,并明确了这些菌株的分类地位.对以上的菌株序列进行Alignment分析,结果表明,病菌的5.8S rDNA序列高度保守,而ITS区的可变性则相对较高,在双核和多核丝核菌、双核丝核菌CAG1融合群和非CAG1融合群菌株间存在差异,可用于反映菌株间的进化关系和双核丝核菌种下分类.  相似文献   

4.
Mazzola M  Gu YH 《Phytopathology》2002,92(12):1300-1307
ABSTRACT The induction of disease-suppressive soils in response to specific cropping sequences has been demonstrated for numerous plant-pathogen systems. The role of host genotype in elicitation of the essential transformations in soil microbial community structure that lead to disease suppression has not been fully recognized. Apple orchard soils were planted with three successive 28-day cycles of specific wheat cultivars in the greenhouse prior to infestation with Rhizoctonia solani anastomosis group (AG)-5 or AG-8. Suppressiveness to Rhizoctonia root rot of apple caused by the introduced isolate of R. solani AG-5 was induced in a wheat cultivar-specific manner. Pasteurization of soils after wheat cultivation and prior to pathogen introduction eliminated the disease suppressive potential of the soil. Wheat cultivars that induced disease suppression enhanced populations of specific fluorescent pseudomonad genotypes with antagonistic activity toward R. solani AG-5 and AG-8, but cultivars that did not elicit a disease suppressive soil did not modify the antagonistic capacity of this bacterial community. When soils were infested prior to the initial wheat planting, all cultivars were uniformly susceptible to R. solani AG-8. However, when pathogen inoculum was added after three growth-cycles, wheat root infection during the fourth growth-cycle varied in a cultivar specific manner. The same wheat cultivar-specific response in terms of transformation of the fluorescent pseudomonad community and subsequent suppression of Rhizoctonia root rot of apple was observed in three different orchard soils. These results demonstrate the importance of host genotype in modification of indigenous saprophytic microbial communities and suggest an important role for host genotype in the success of biological control.  相似文献   

5.
烟草靶斑病菌菌丝融合群及ITS序列分析   总被引：1，自引：0，他引：1  
 烟草靶斑病是2006年我国新报道发生的一种叶部病害［1］,其病原的无性世代为立枯丝核菌(Rhizoctonia solani Kühn),有性世代为瓜亡革菌(Thanatephorus cucumeris (Frank)Donk)。该病菌主要危害叶部形成病斑,对烟草的产量和品质影响显著,目前该病害主要分布在辽宁省丹东和铁岭地区,并呈现出迅速蔓延趋势。烟草靶斑病最早由巴西报道,此后,哥斯达黎加、美国、南非和津巴布韦也相继发生［2,3］。  相似文献   

6.
ABSTRACT Rhizoctonia solani anastomosis group (AG)-13 was collected from diseased roots of field grown cotton plants in Georgia in the United States. Isolates of AG-13 did not anastomose with tester isolates of AG-1 through AG-12. Mycelium of all isolates of AG-13 were light brown but darkened as cultures aged. All isolates produced aerial mycelium. Concentric rings were visible after 3 to 4 days of growth but disappeared as cultures aged and darkened. Individual sclerotia were up to 1.5 mm in diameter, similar in color to the mycelium, and generally embedded in the agar. Clumps of sclerotia up to 5 mm in diameter were produced on the agar surface. All attempts to induce basidiospore production were unsuccessful. The 5.8S region of the rDNA from isolates of AG-13 was identical in length and sequence to isolates of all other AGs of R. solani. Length and sequence of the internal transcribed spacer (ITS) regions of rDNA from isolates of AG-13 were unique among AGs of R. solani. Similarity between AG-13 and other AGs of R. solani ranged from 68 to 85% for ITS region 1 and 85 to 95% for ITS region 2. Selected isolates of AG-13 caused minor or no damage to barley, cauliflower, cotton, lettuce, potato, and radish in laboratory or greenhouse studies.  相似文献   

7.
Rhizoctonia solani was an important though erratically occurring pathogen of protected lettuce but was unimportant in outdoor crops. The most common fungal pathogen in rotted basal leaves of both protected and outdoor lettuce in Humberside and Lancashire was Botrytis cinerea. Sclerotinia sclerotiorum was common in leaves of outdoor lettuce in Lancashire but was encountered infrequently in protected crops in Humberside, Of 27 isoJates of R. solani which were tested for anastomosis group. 11 were AG-L 13 were AG-2 type I. two were AG-2 and one was AG-4. The AG-4 isolate had a Thanatephorus praticola teleomorph whereas representatives from the other groups were Thanatephorus cucumeris.  相似文献   

8.
ABSTRACT The relative contribution of migration of Rhizoctonia solani anastomosis group 3 (AG-3) on infested potato seed tubers originating from production areas in Canada, Maine, and Wisconsin (source population) to the genetic diversity and structure of populations of R. solani AG-3 in North Carolina (NC) soil (recipient population) was examined. The frequency of alleles detected by multilocus polymerase chain reaction-restriction fragment length polymorphisms, heterozygosity at individual loci, and gametic phase disequilibrium between all pairs of loci were determined for subpopulations of R. solani AG-3 from eight sources of potato seed tubers and from five soils in NC. Analysis of molecular variation revealed little variation between seed source and NC recipient soil populations or between subpopulations within each region. Analysis of population data with a Bayesian-based statistical method previously developed for detecting migration in human populations suggested that six multilocus genotypes from the NC soil population had a statistically significant probability of being migrants from the northern source population. The one-way (unidirectional) migration of genotypes of R. solani AG-3 into NC on infested potato seed tubers from Canada, Maine, and Wisconsin provides a plausible explanation for the lack of genetic subdivision (differentiation) between populations of the pathogen in NC soils or between the northern source and the NC recipient soil populations.  相似文献   

9.
Ninety-eight isolates of Rhizoctonia spp. were obtained from barley and wheat grown in Erzurum, Turkey. Of these, 78% were Rhizoctonia solani (AG-2 type 1, AG-3, AG-4, AG-5 and AG-11), 10% were binucleate Rhizoctonia (AG-I and AG-K) and the remainder were Waitea circinata var circinata ( Rhizoctonia sp.). Among the binucleate Rhizoctonia , AG-I was not recovered from barley. In pathogenicity tests on barley and wheat, the highest disease severity was caused by isolates of AG-4 and AG-11, whereas isolates of AG-2 type 1, AG-3, AG-5 and W. c . var  circinata were moderately virulent. Isolates of binucleate Rhizoctonia were all nonpathogenic. This is the first report of R. solani AG-11 and W. c . var  circinata from Turkey.  相似文献   

10.
A total of 119 isolates of Rhizoctonia were collected from stem canker lesions, stolon and root lesions, hymenia on stems, or from black scurf on tubers of potato plants ( Solanum tuberosum ) in Finland (latitudes 60–67°N). All isolates except three belonged to anastomosis group 3 (AG-3) of R. solani , as determined by phylogenetic analysis of the internal transcribed spacer sequences (ITS1 and ITS2) of ribosomal RNA (rRNA) genes. Sensitivity of the 119 isolates to the fungicide flutolanil was tested in vitro (EC50 values 0·14–0·75  µ g active ingredient mL−1). The isolates also varied considerably in growth rate (5·1–14·8 mm day−1). The severity of disease caused by 99 isolates was determined based on the proportion of potato sprouts affected by lesions, discoloration or death, which was c . 1–60%. Only two isolates that were able to cause severe symptoms showed particularly low sensitivity to the fungicide and rapid growth rate. One isolate each of anastomosis groups AG-2-1 and AG-5 and an unknown, binucleate Rhizoctonia sp. were detected. The AG-5 isolate and the binucleate isolate caused mild symptoms on potato sprouts, whereas the AG-2-1 isolate was not pathogenic. Taken together, AG-3 of R. solani was the predominant causal agent of the stem canker and black scurf diseases of potato in Finland and showed considerable variability in disease severity, fungicide sensitivity and growth rate in vitro .  相似文献   

11.
新疆北疆棉田立枯丝核菌不同菌丝融合群致病力的研究   总被引：1，自引：0，他引：1  
从新疆北疆棉区采集了典型的棉花立枯病病苗及棉田土标样686份,按常规分离方法分离得到399个分离物,从中鉴定出272个纯化的立枯丝核菌(Rhizoctonia solani Kühn)菌株。用标准菌株,通过载玻片菌丝融合试验测定,将纯化的272个菌株划归为3个菌丝融合群:即AG-2、AG-4和AG-5,分别占总菌株的6.24%、84.2%和1.1%。另有23个菌株不与任何标准菌株融合,占8.46%,说明新疆北疆棉田立枯丝核菌的优势菌系是多核丝核菌的AG-4融合群。通过从10种不同配方培养基中筛选效果好的麦芽蛋白胨(MPDA)配方培养基(Ⅱ)进行对峙培养,将纯化获得的272个丝核菌菌株,划分为6个不同的营养亲和群。将多核的不同菌丝融合群及其各营养亲和群代表菌株在3种不同主栽棉花品种上(每品种都加不接菌的对照)进行温室盆栽致病力测定,结果以AG-4对棉花的致病力最强,其次是非融合类,AG-2和AG-5虽致病,但并不致死苗,其平均病指数分别为94.9、81.4、53.1、43.5。  相似文献   

12.
ABSTRACT The effect of seed meals derived from Brassica juncea, B. napus, or Sinapis alba on suppression of soilborne pathogens inciting replant disease of apple was evaluated in greenhouse trials. Regardless of plant source, seed meal amendment significantly improved apple growth in all orchard soils; however, relative differences in pathogen suppression were observed. All seed meals suppressed root infection by native Rhizoctonia spp. and an introduced isolate of Rhizoctonia solani AG-5, though B. juncea seed meal often generated a lower level of disease control relative to other seed meal types. When introduction of the pathogen was delayed until 4 to 8 weeks post seed meal amendment, disease suppression was associated with proliferation of resident Streptomyces spp. and not qualitative or quantitative attributes of seed meal glucosinolate content. Using the same experimental system, when soils were pasteurized prior to pathogen infestation, control of R. solani was eliminated regardless of seed meal type. In the case of B. juncea seed meal amendment, the mechanism of R. solani suppression varied in a temporal manner, which initially was associated with the generation of allylisothiocyanate and was not affected by soil pasteurization. Among those tested, only B. juncea seed meal did not stimulate orchard soil populations of Pythium spp. and infection of apple roots by these oomycetes. Although application of B. napus seed meal alone consistently induced an increase in Pythium spp. populations, no significant increase in Pythium spp. populations was observed in response to a composite B. juncea and B. napus seed meal amendment. Suppression of soil populations and root infestation by Pratylenchus spp. was dependent upon seed meal type, with only B. juncea providing sustained nematode control. Collectively, these studies suggest that use of a composite B. juncea and B. napus seed meal mixture can provide superior control of the pathogen complex inciting apple replant disease relative to either seed meal used alone.  相似文献   

13.
Rhizoctonia solani and R. cerealis were isolated from diseased sugar-beet seedlings in Ireland. Isolates of R. solani were assigned to anastomosis groups AG-2, AG-4, AG-5 and an unidentified group that did not anastomose with recognized tester isolates. Cultures of AG-2 were similar to those of AG-5 on oatmeal agar (OA) and potato-dextrose-marmite agar (PDMA). Cultures of AG-4, the unidentified group and R. cerealis were morphologically distinct from one another, AG-2 and AG-5. The optimum temperature for growth of AG-2 was 225 C, with optimum growth of AG-4, AG-5 and the unidentified group at 275-C. R. cerealis grew slower than all groups of R. solani, with optimum growth at 225°C. Hyphae of R. cerealis were significantly narrower than those of the groups of R. solani studied. In glasshouse pathogenicity tests, some AG-2 and all AG-4, AG-5 and isolates from the unidentified group caused damping-off of beet seedlings. In controlled environments of 10-25°C, an AG-2 isolate was the most aggressive at 10 C whilst AG-4, AG-5 and the unidentified group caused most disease at or above 15°C. R. cerealis was also pathogenic to beet seedlings, causing damping-off at 10 and 15 C.  相似文献   

14.
Israeli farmers export 250,000 tons of potato tubers annually, ≈40,000 tons of which are harvested early, before skin set. In recent years, there has been an increase in the occurrence of dark skin spots on early-harvested potato tubers ('Nicola') packed in large bags containing peat to retain moisture. The irregular necrotic spots form during storage and overseas transport. Characterization of the conditions required for symptom development indicated that bag temperature after packing is 11 to 13°C and it reaches the target temperature (8°C) only 25 days postharvest. This slow decrease in temperature may promote the establishment of pathogen infection. Isolates from typical lesions were identified as Rhizoctonia spp., and Koch's postulates were completed with 25 isolates by artificial inoculation performed at 13 to 14°C. Phylogenetic analysis, using the internal transcribed spacer sequences (ITS1 and ITS2) of rDNA genes, assigned three isolates to anastomosis group 3 of Rhizoctonia solani. Inoculation of wounded tubers with mycelium of these R. solani isolates resulted in an oversuberization response in the infected area. With isolate Rh17 of R. solani, expression of the suberin biosynthesis-related genes StKCS6 and CYP86A33 increased 6.8- and 3.4-fold, respectively, 24 h postinoculation, followed by a 2.9-fold increase in POP_A, a gene associated with wound-induced suberization, expression 48 h postinoculation, compared with the noninoculated tubers. We suggest that postharvest dark spot disease is an oversuberization response to R. solani of AG-3 infection that occurs prior to tuber skin set.  相似文献   

15.
An extensive study was conducted to determine where in the production chain Rhizoctonia solani became associated with UK module-raised Brassica oleracea plants. In total, 2600 plants from 52 crops were sampled directly from propagators and repeat sampled from the field. Additional soil, compost and water samples were collected from propagation nurseries and screened using conventional agar isolation methods. No isolates of R. solani were recovered from any samples collected from propagation nurseries. Furthermore, nucleic acid preparations from samples of soil and compost from propagation nurseries gave negative results when tested for R. solani using real-time PCR. Conversely, R. solani was recovered from 116 of 1300 stem bases collected from field crops. All the data collected suggested R. solani became associated with B. oleracea in the field rather than during propagation. Parsimony and Bayesian phylogenetic studies of ribosomal DNA suggested the majority of further classified isolates belonged to anastomosis groups 2-1 (48/57) and AG-4HGII (8/57), groups known to be pathogenic on Brassica spp. in other countries. Many R. solani isolates were recovered from symptomless plant material and the possibilities for such an association are discussed.  相似文献   

16.
Rhizoctonia cerealis E.P. van der Hoeven (anamorph of Ceratobasidium cereale D.I. Murray and Burpee), which causes sharp eyespot in wheat, is a major soilborne fungal pathogen that severely impairs yield and quality of winter wheat in China. Because the pathogen is difficult to identify and quantify in soil using conventional methods, a rapid and reliable method is needed to detect and quantify the fungus. In this study, we developed an SYBR Green-based quantitative real-time polymerase chain reaction assay for specific, sensitive detection and quantification of R. cerealis in soil samples. Using a specific primer pair based on the β-tubulin gene of the fungal DNA sequence, we could specifically detect R. cerealis at quantities as low as 100?fg of purified pathogen DNA. Using the real-time PCR assays, we were able to quantify R. cerealis in artificially and naturally infested soil samples. This new technique to quantify R. cerealis is rapid and accurate and will be a useful tool for future studies of pathogenic R. cerealis.  相似文献   

17.
ABSTRACT A murine hybridoma cell line GD2 secreting an immunoglobulin (Ig)M monoclonal antibody (MAb) was produced against surface antigens from an anastomosis group (AG) 4 isolate of Rhizoctonia solani (teleomorph: Thanatephorus cucumeris). Ascites were produced in mice using GD2 hybridoma cells and used to develop a rapid immunochromatographic lateral flow device (LFD) for the detection of antigens from R. solani and certain related Rhizoctonia spp. The LFD was tested for specificity against surface antigens from related and unrelated soil fungi. Antigens from representative isolates of R. solani AGs 1, 2-1, 2-3, 2-t, 3, 4, 5, 6, 7, 8, 9, 10, 11, and BI gave a positive response in LFD tests, as did antigens from Thanatephorus orchidicola, T. praticola, R. fragariae (teleomorph: Ceratorhiza fragariae), Ceratorhiza goodyerae-repentis, Ceratobasidium cornigerum, and binucleate AGE. Antigens from R. solani AGs 2-2, 2-2IIIB, and 2-2IV and from the related fungi R. carotae, R. cerealis (teleomorph: Ceratobasium cereale), R. crocorum (teleomorph: Helicobasidium brebissonii), R. oryzae (teleomorph Waitea circinata), and R. zeae gave negative responses, as did antigens from a range of unrelated fungi and oomycetes including Fusarium, Gliocladium, Trichoderma, Pythium, and Phytophthora spp. The usefulness of the LFD to detect R. solani was demonstrated in soils naturally infested with R. solani AG3. There was close agreement between results of LFD tests and conventional plate enrichment tests employing selective medium. The specificity of the technique was confirmed by polymerase chain reaction PCR using R. solani AG3-specific primers and by analyses based on sequences of the internal transcribed spacer (ITS)1-5.8S-ITS2 rRNA-encoding regions of unrelated fungi recovered from soil samples. The LFD was used to quantify R. solani AG4 in artificially infested soil samples (chopped potato soil inoculum). Estimates of CFU per gram of soil were derived using a most-probable number technique, which was based on the presence or absence of a detectable signal in the LFD. Estimates of CFU obtained in LFD tests and those obtained in a plate-trapped antigen enzyme-linked immunosorbent assay incorporating MAb GD2 were identical (449 CFU g(-1) of soil).  相似文献   

18.
Isolates of Rhizoctonia collected from the stems, roots, tuber sclerotia and soil of potato crops in Virginia and Lenswood, South Australia, were identified to anastomosis groups (AG). Of the 301 multinucleate isolates of Rhizoctonia solani tested, 90% were AG-3, 7% were AG-4 and 2% were AG-5; 12 isolates were binucleate Rhizoctonia spp. This is the first report of isolates of AG-4 and AG-5 causing disease in potato crops in South Australia. All AG-3, AG-4 and AG-5 isolates tested caused rhizoctonia disease symptoms on the potato cultivar Coliban in pathogenicity trials conducted under glasshotise conditions. Both AG-3 and AG-5 isolates caused black scurf and stem cankers, although symptoms of black scurf were less severe with AG-5. AG-4 isolates produced the most severe stem and stolon cankers of all isolates tested. The pathogenicity of tuber-borne inoculum was confirmed by growing plants from sclerotia-infested tubers. AG-8 isolates from diseased barley and wheat produced severe root cankers and caused loss of feeder roots on inoculated potato plants. Results suggest that rhizoctonia disease in potato fields in South Australia is caused by a combination of different anastomosis groups and this has important implications for crop rotations.  相似文献   

19.
杨金红 《植物保护》2009,35(6):83-86
从新疆11种豆科作物病株上或病株根围土样中分离纯化出250个立枯丝核菌（Rhizoctonia DC）,番红O KOH染色后观察细胞核数目,经测试全部菌株均为多核,用标准菌株测定融合群, 250个菌株分属为AG 1、AG 2、AG 3、AG 4和AG 5共5个融合群,出现频率分别为16.4%、33.2%、0.4%、32.4%和17.6%,营养亲合群判别结果表明,AG 1、AG 2、AG 4和AG 5下各有2个VCG,说明新疆豆科作物立枯丝核菌各主要菌丝融合群内均有不同程度的分化。  相似文献   

20.
Foot rot of mature tomato plants was found in four cities of Hokkaido, Japan, from 2004 to 2007. Six of eight isolates obtained from damaged tissues were identified as Rhizoctonia solani anastomosis group (AG)-3, and the remaining two isolates belonged to AG-2-1. We compared these isolates with nine reference isolates including the different subgroups in AG-3 (PT, TB and TM) and AG-2-Nt (pathogen of tobacco leaf spot) within AG-2-1 in terms of pathogenicity to tomato, tobacco and potato. All eight isolates caused foot rot on tomato. The six AG-3 isolates caused stem rot on young potato plants. While, all reference isolates of AG-3 PT causing stem rot of young potato plants incited foot rot on tomato. The two AG-2-1 isolates and an AG-2-Nt reference isolate caused severe leaf spot on tobacco leaves. The sequences of rDNA- ITS region and rDNA-IGS1 region of the AG-3 isolates showed high similarity to that of AG-3 PT isolates. Phylogenetic tree based on ITS and IGS1 regions of rDNA indicated that the AG-2-1 isolates from tomato formed a single clade with AG-2-Nt isolates and that they were separate from Japanese AG-2-1 isolates (culture type II). Pathogenicity tests and DNA sequence evaluation of the causal fungi revealed that the present isolates of AG-3 and AG-2-1 belonged to AG-3 PT and AG-2-Nt, respectively. This is the first report of tomato foot rot caused by R. solani in Japan.  相似文献   

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