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1.
ABSTRACT A molecular marker was developed to separate and identify subspecific populations of Phialophora gregata, the causal agent of soybean brown stem rot. A variable DNA region in the intergenic spacer of the nuclear rDNA was identified. Two specific primers flanking the variable region were developed for easy identification of the genotypes using polymerase chain reaction (PCR). These two specific primers amplified three DNA products. The three PCR products were used to separate isolates of P. gregata into distinct genotypes: A (1,020 bp), B (830 bp), and C (660 bp). Genotype C was found in isolates obtained from Adzuki beans from Japan, whereas all 292 isolates obtained from soybean and the 8 isolates from mung bean belonged to either genotype A or B. The original nondefoliating (type II) strain ATCC 11073 (type culture of P. gregata) belonged to genotype B. The difference between genotypes A and B was due only to an 188-bp insertion or deletion; genotype C, however, differs from genotypes A and B at 58 point mutations, in addition to the length difference. Isolates of both genotypes A and B were widespread in seven Midwestern states. Genotype A was found mostly in certain susceptible soybean cultivars like Sturdy and Pioneer 9305, whereas genotype B was found predominately in brown stem rot-resistant soybean cvs. Bell, IA 3003, and Seiben SS282N. The specific primers were also used to directly detect cultivar-preferential infection by the two genotypes in infected soybean stems growing in the same field. Data from direct detection in soybean stems showed that cultivar-preferential infection by the two genotypes of P. gregata was significant. 相似文献
2.
ABSTRACT The prevalence of brown stem rot (caused by Phialophora gregata), Heterodera glycines, and Phytophthora sojae in the north central United States was investigated during the fall of 1995 and 1996. Soybean fields were randomly selected using an area-frame sampling design in collaboration with the National Agricultural Statistics Service. Soil and soybean stem samples, along with tillage information, were collected from 1,462 fields in Illinois, Iowa, Minnesota, Missouri, and Ohio. An additional 275 soil samples collected from Indiana were assessed for H. glycines. For each field, the incidence and prevalence of brown stem rot was assessed in 20 soybean stem pieces. The prevalence and recovery (expressed as the percentage of leaf disks colonized) of P. sojae and the prevalence and population densities of H. glycines were determined from the soil samples. The prevalence of brown stem rot ranged from 28% in Missouri to 73% in Illinois; 68 and 72% of the fields in Minnesota and Iowa, respectively, showed symptomatic samples. The incidence of brown stem rot was greater in conservation-till than in conventional-till fields in all states except Minnesota, which had few no-till fields. P. sojae was detected in two-thirds of the soybean fields in Ohio and Minnesota, whereas 63, 55, and 41% of the fields in Iowa, Missouri, and Illinois, respectively, were infested with the pathogen. The recovery rates of P. sojae were significantly greater (P 相似文献
3.
Phialophora gregata f.sp. sojae , a soilborne vascular pathogen causing brown stem rot of soybean, has been divided into A and B populations based on variation in the intergenic spacer region of nuclear rDNA (rDNA marker). The A and B populations correlate with defoliating and nondefoliating pathotypes, respectively. In this study, eight additional polymorphic anonymous marker loci (five inter simple sequence repeat loci and three long-primer random amplified polymorphic DNA loci) were identified and applied to a total of 189 isolates. Alleles of these eight loci were invariant within, but different between the A and B populations, providing further evidence that the rDNA marker identifies genetically distinct populations. The two populations were sympatric, residing not only in the same field, but also in the same plants under field conditions. Representative strains of the two populations, when used individually in inoculations, infected both resistant cv. Bell and susceptible cv. Sturdy. However, when the same representatives of the two populations were mixed in a 1 : 1 ratio and used as a mixed inoculum in a competitive bioassay, differential cultivar preference was revealed using PCR detection of populations in infected plants. Population A was detected significantly more often (18 out of 24 plants) in the susceptible cv. Sturdy, whereas population B was detected significantly more often (17 out of 24 plants) in the resistant cv. Bell, corroborating earlier field studies. This is the first controlled experiment to demonstrate a differential host preference of P. gregata f.sp. sojae toward different cultivars of the same host species. Unification of terminologies used in P. gregata f.sp. sojae is discussed. 相似文献
4.
ABSTRACT Investigations were conducted to determine whether the effects of tillage practices on the prevalence of brown stem rot of soybean (caused by Phialophora gregata), Heterodera glycines, and Phytophthora sojae were confounded by soil texture in samples collected in the fall of 1995 and 1996. Soil and soybean stem samples, along with tillage information, were collected from 1,462 randomly selected fields in Illinois, Iowa, Minnesota, Missouri, and Ohio in collaboration with the National Agricultural Statistics Service. The incidence of brown stem rot was determined from 20 soybean stem pieces collected from each field in a zigzag pattern. The detection frequency of P. sojae (expressed as percent leaf disks colonized) and population densities of H. glycines were determined from soil cores also collected in a zigzag pattern. The soil samples were grouped into various textural classes, and the effect of soil texture and tillage relations on the activities of each pathogen were determined. Both tillage and soil texture affected the incidence of brown stem rot; however, there was no interaction between tillage and soil texture. Conservation tillage had a greater (P < 0.05) incidence of brown stem rot in clay loam and silty clay loam than did conventional tillage. The detection frequency of P. sojae was not affected by tillage, but a tillage x texture interaction (P = 0.013) indicated that the effect of tillage depended on soil texture. There was a greater (P < 0.05) detection frequency of P. sojae in conservation tillage than in conventional tillage in silt loam and loam soils. However, in sandy loam, the detection frequency of P. sojae was greater (P = 0.0099) in conventional tillage than in conservation tillage. Population densities of H. glycines were significantly affected by both tillage and soil texture, but overall, there was no tillage x texture interaction. There was an inverse relationship between population densities of H. glycines and percent clay (r = -0.81, P = 0.01) in no-till fields, but little or no change in nematode densities was observed with increasing clay content in tilled fields. Population densities of H. glycines were less (P < 0.05) in no-till fields than in tilled fields in silty clay loam and clay soils. There was no difference in H. glycines densities between the tillage categories in soils sandier than silty clay loam or clay. The findings emphasize the need for cautious interpretation of the effects of tillage practices on diseases and pathogens in the absence of information on soil texture. 相似文献
5.
Two diseases of adzuki bean, brown stem rot (BSR, caused by Cadophora gregata f. sp. adzukicola) and adzuki bean Fusarium wilt (AFW, caused by Fusarium oxysporum f. sp. adzukicola), are serious problems in Hokkaido and have been controlled using cultivars with multiple resistance. However, because a
new race of BSR, designated race 3, was identified, sources of parental adzuki bean for resistance to race 3 were needed.
Therefore, we examined 67 cultivars and lines of cultivated and wild adzuki bean maintained at the Tokachi Agricultural Experiment
Station using a root-dip inoculation method. Consequently, nine adzuki bean cultivars, one wild adzuki bean accession and
30 lines (including two lines resistant to all the three races of BSR and AFW) were confirmed to be resistant or tolerant
to race 3 of BSR, and we found a cultivar Akamame as well as a wild adzuki bean Acc2515 to be a new source for a resistance
gene to the race 3. This cultivar also holds promise as a source of resistance against other races of BSR and AFW. 相似文献
6.
Norio Kondo Kie Nakazawa Shohei Fujita Hisanori Shimada Shigeo Naito 《Journal of General Plant Pathology》2005,71(5):360-363
Adzuki bean cultivar Acc259, which is resistant to races 1 and 2 of Phialophora gregata f. sp. adzukicola, was used as a breeding resource for resistance to brown stem rot (BSR). During the third year after two successive cultivations of Acc259, a severe outbreak of BSR occurred in an experimental plot at the Tokachi Agricultural Experiment Station, Hokkaido, Japan. The isolates obtained from diseased plants were virulent to Erimo-shozu (susceptible to all races) and Acc259 but avirulent to Kita-no-otome (resistant to race 1 but susceptible to race 2). The existence of a new race of P. gregata f. sp. adzukicola, designated race 3, was determined; and its frequency in the plot soil was shown to increase from 16.7% before planting Acc259 to 100% after the third year. Of 140 isolates from the commercial production area that were formerly identified as race 1, 13 were actually race 3 and were restricted to certain limited fields. 相似文献
7.
A California isolate of Meloidogyne javanica increased Fusarium wilt symptoms in cowpea cultivars California Blackeye No. 3 (CB3) (resistant to wilt) and Grant (tolerant) inoculated with each of the three races of Fusarium oxysporum f. sp. tracheiphilum. The same isolate of M. javancia did not similarly increase wilt in wilt-resistant cultivar CB7977 inoculated with two isolates of race 3 of F. o. tracheiphilum. Six of seven isolates of M. javanica caused similar increases in vascular discoloration in cultivar CB3. but one isolate of M. javanica and seven of M. incognita did not. Vascular discoloration rating was positively correlated with galling severity. However, increasing the initial inoculum density, and thus galling index, of one isolate of M. incognita did not increase vascular discoloration. The vascular discoloration ratings for the wilt-susceptible CB5 controls in each experiment were higher than those for the wilt-resistant cultivars infected with M. javanica. It is hypothesized that M. javanica but not M. incognita reduces, but does not eliminate, resistance to all races of F. o. tracheiphilum in cultivars CB3 and Grant. 相似文献
8.
ABSTRACT Phytophthora sojae, which causes Phytophthora root and stem rot of soybean, is a serious disease worldwide and is managed primarily by deploying cultivars with resistance. Thirty-two soybean plant introductions (PIs), all but three of which were from South Korea, were proposed as new sources of single-gene resistance to P. sojae. The objective of this study was to characterize the inheritance of resistance to P. sojae in these PIs. Twenty-two soybean populations from crosses of these PIs and the susceptible cv. Williams were inoculated with P. sojae OH17 (vir 1b, 1d, 2, 3a, 3b, 3c, 4, 5, 6, 7), and OH25 (vir 1a, 1b, 1c, 1k, 7). These isolates were selected because they are virulent on soybeans with all known Rps genes and many Rps gene combinations. Thirteen of the twenty-two populations had consistent segregation responses following inoculations between the two generations. In two PIs, resistance was conferred by two genes to OH17 and three genes to OH25. Resistance to both isolates was conferred by a single gene in PI 398440 although the individual families were not resistant to the same isolates. The data suggest that six of the populations have three-Rps gene combinations as previously proposed, while another four may have either a novel Rps gene or a four-Rps gene combination. Based on this phenotypic analysis, novel and uncharacterized Rps genes may be present in this material. More importantly, these PIs may serve as sources of novel Rps genes that can be used to more effectively manage Phytophthora root and stem rot. 相似文献
9.
Takuma Sugimoto Shinya Yoshida Masataka Aino Kazuhiko Watanabe Kuniko Shiwaku Mikihiro Sugimoto 《Journal of General Plant Pathology》2006,72(2):92-97
Since 1987, Phytophthora root and stem rot of soybean [Glycine max (L.) Merr. cv. Tanbakuro], caused by Phytophthora sojae Kaufman and Gerdemann, has been increasing in the Sasayama, Nishiwaki, and Kasai regions in Hyogo, the most famous soybean
(cv. Tanbakuro)-producing areas in Japan. In 2002 to 2004, 51 isolates (one from each field) of P. sojae were recovered from 51 fields in Hyogo. These isolates were tested for virulence on six Japanese differential soybean cultivars
used for race determination in Japan, and three additional ones containing four Rps genes used in Indiana, USA. Race E was the most prevalent from 2002 to 2004, followed by races A, C, D, and four new races
(proposed as races K, L, M, and N). Interestingly, none of the new races had high virulence on the Japanese differential cultivars,
compared with other races in each area. One (race N) was avirulent on all six soybean differentials. There was a difference
in race distribution on each of three individual areas; race E seemed to be a major component of the P. sojae population in Sasayama, whereas race A and the new race M were the most prevalent in Nishiwaki and Kasai, respectively. Rps6 (cv. Altona) and Rps1a + Rps7 (cv. Harosoy 63) were infected by 90.2% and 33.3% of all isolates, respectively. However, Rps1d (cv. PI103091) was not susceptible to any of the 51 isolates, nor was cv. Gedenshirazu-1. These two soybean cultivars were
considered to be potential sources of resistance to breed new resistant cultivars with the desirable characteristics of cv.
Tanbakuro for this region. 相似文献
10.
Ranathunge K Thomas RH Fang X Peterson CA Gijzen M Bernards MA 《Phytopathology》2008,98(11):1179-1189
Phytophthora sojae is the causal agent of root and stem rot of soybean (Glycine max). Various cultivars with partial resistance to the pathogen have been developed to mitigate this damage. Herein, two contrasting genotypes, the cultivar Conrad (with strong partial resistance) and the line OX760-6 (with weak partial resistance), were compared regarding their amounts of preformed and induced suberin components, and to early events during the P. sojae infection process. To colonize the root, hyphae grew through the suberized middle lamellae between epidermal cells. This took 2 to 3 h longer in Conrad than in OX760-6, giving Conrad plants more time to establish their chemical defenses. Subsequent growth of hyphae through the endodermis was also delayed in Conrad. This cultivar had more preformed aliphatic suberin than the line OX760-6 and was induced to form more aliphatic suberin several days prior to that of OX760-6. However, the induced suberin was formed subsequent to the initial infection process. Eventually, the amount of induced suberin (measured 8 days postinoculation) was the same in both genotypes. Preformed root epidermal suberin provides a target for selection and development of new soybean cultivars with higher levels of expression of partial resistance to P. sojae. 相似文献
11.
从进境的美国大豆豆秆样品中分离到2株疑似大豆茎褐腐病菌Phialophora gregata的分离物247-8和8300-5,2株分离物在PGM培养基上菌落圆形,边缘规则,白色至暗褐色,表面隆起,粗糙,轮纹状。分生孢子卵形至椭圆形,无色,平滑,单胞,平均大小4.3 μm×1.9 μm。分生孢子梗具有瓶梗状结构,无色,无隔膜或有隔膜,大小(5~16)μm×(2~3) μm,呈桶型或长颈瓶型。特异性引物BSRIGS1/2、BSR1/2和Pgl/4分别扩增分离物247-8的DNA得到预期1 022 bp、483 bp和499 bp的产物;分离物8300-5的DNA经PCR扩增分别得到834 bp、483 bp和499 bp的预期条带。2株分离物的ITS区序列完全一致,与GenBank中大豆茎褐腐病菌(登录号AB190396、DQ459387、DQ459386和AF132804)的序列相似性为100%。人工接种大豆幼嫩植株茎基部均产生大豆茎褐腐病菌的典型症状。根据分离物形态特征、PCR检测、序列分析以及致病性测试结果,将进境美国大豆样品中的分离物247-8和8300-5鉴定为大豆茎褐腐病菌P. gregata。 相似文献
12.
ABSTRACT Resistance to brown stem rot of soybean has been identified and utilized in cultivar development and germ plasm enhancement. However, little is known about the nature of resistance to this disease. In an attempt to better understand the resistance mechanism by locating the tissue or tissues responsible for resistance, reciprocal grafts were made between brown stem rot-resistant and -susceptible genotypes including near-isogenic lines for resistance gene Rbs2. Results of brown stem rot evaluation of grafted plants indicate that brown stem rot resistance is conditioned by the root in all resistance sources evaluated. 相似文献
13.
H. J. M. Löffler Th. P. Straathof J. R. Mouris R. P. Baayen 《European journal of plant pathology / European Foundation for Plant Pathology》1995,101(3):261-271
Prospects of durability of resistance in lily to basal rot have been evaluated by testing the virulence and aggressiveness of 31 isolates ofFusarium oxysporum f. sp.lilii towards a number of different resistance sources inLilium spp. Isolates differed strongly in aggressiveness as did species and cultivars ofLilium spp. in resistance. Significant interactions were observed between isolates of the pathogen and genotypes ofLilium spp., but the magnitude was very small compared to the main effects. The interactions were mainly due to a small group of isolates with low aggressiveness. It is argued that the interactions might be based on minor genes. No major break down of the resistance was found. For practical purposes it will be sufficient to use highly aggressive isolates in screening tests. 相似文献
14.
ABSTRACT Phytophthora root and stem rot of soybeans caused by Phytophthora sojae is a serious limitation to soybean production in the United States. Partial resistance to P. sojae in soybeans is effective against all the races of the pathogen and is a form of incomplete resistance in which the level of colonization of the root is reduced following inoculation. Other forms of incomplete resistance include the single dominant gene Rps2 and Ripley's root resistance, which are both race-specific. To differentiate partial resistance from the other types of incomplete resistance, the components lesion length, numbers of oospores, and infection frequency were measured in eight soybean genotypes inoculated with two P. sojae isolates. The Rps2 and root-resistant genotypes had significantly lower oospore production and infection frequency compared with the partially resistant genotype Conrad, while the root-resistant genotype also had significantly smaller lesion lengths. However, the high levels of partial resistance in Jack were indistinguishable from Rps2 in L76-1988, based on the evaluation of these components. Root resistance in Ripley and Rps2 in L76-1988 had similar responses for all components measured in this study. Partial resistance expressed in Conrad, Williams, Jack, and General was comprised of various components that interact for defense against P. sojae in the roots, and different levels of each component were found in each of the genotypes. However, forms of incomplete resistance expressed via single genes in Ripley and Rps2 in L76-1988, could not be distinguished from high levels of partial resistance based on lesion length, oospore production, and infection frequency. 相似文献
15.
ABSTRACT Root and stem rot caused by Phytophthora sojae is one of the most destructive diseases of soybean (Glycine max) worldwide. P. sojae can survive as oospores in soil for many years. In order to develop a rapid and accurate method for the specific detection of P. sojae in soil, the internal transcribed spacer (ITS) regions of eight P. sojae isolates were amplified using polymerase chain reaction (PCR) with the universal primers DC6 and ITS4. The sequences of PCR products were aligned with published sequences of 50 other Phytophthora species, and a region specific to P. sojae was used to design the specific PCR primers, PS1 and PS2. More than 245 isolates representing 25 species of Phytophthora and at least 35 other species of pathogens were used to test the specificity of the primers. PCR amplification with PS primers resulted in the amplification of a product of approximately 330 bp, exclusively from isolates of P. sojae. Tests with P. sojae genomic DNA determined that the sensitivity of the PS primer set is approximately 1 fg. This PCR assay, combined with a simple soil screening method developed in this work, allowed the detection of P. sojae from soil within 6 h, with a detection sensitivity of two oospores in 20 g of soil. PCR with the PS primers could also be used to detect P. sojae from diseased soybean tissue and residues. Real-time fluorescent quantitative PCR assays were also developed to detect the pathogen directly in soil samples. The PS primer-based PCR assay provides a rapid and sensitive tool for the detection of P. sojae in soil and infected soybean tissue. 相似文献
16.
A. S. Turner P. Nicholson S. G. Edwards G. L. Bateman † L. W. Morgan A. D. Todd D. W. Parry J. Marshall M. Nuttall 《Plant pathology》2002,51(4):464-471
Relationships between the incidence and severity of brown foot rot and of pathogenic fungi, determined by diagnostic and quantitative PCR, were investigated during the growth of nine winter wheat crops in three cropping seasons. Microdochium nivale vars nivale and majus were the only brown foot rot pathogens present in significant amounts. Relationships between disease symptoms and amounts of pathogen DNA were often weak in early spring (when shoot-base symptoms are usually most difficult to ascribe to particular pathogens by visual examination) because of indistinct symptoms and small amounts of pathogen. Relationships were strongest during stem elongation. The amount of M. nivale in the tissues tended to decline in the summer as the plants matured, apparently disappearing partially from necrotic lesions to which it contributed, resulting in a weakened relationship between symptoms and pathogen DNA. Regression analyses of brown foot rot on amounts of M. nivale DNA for different wheat cultivars generally produced lines with similar slopes but were often most significant for the cultivar with most eyespot resistance (i.e. with least confounding eyespot) or most apparently genuine brown foot rot. DNA of Fusarium spp. was rarely present in amounts sufficient to quantify. 相似文献
17.
Stem rot of Anoectochilus formosanus (Af) caused by Fusarium oxysporum (Fo) is a major limiting factor to jewel orchid production in Taiwan. Fo causes discoloration in vascular tissues. However, some newly collected Fo isolates from Af stem rot do not cause vascular discoloration, suggesting changes may have occurred in the pathogen. Among recent Fo isolates from Af there are two colony types, the cottony alba (CA) and the sporodochial (S). In order to confirm that both colony types cause Af stem rot, 200 isolates were obtained from diseased stems in Nantou County and characterized by colony type and whether or not the infected plants had vascular discoloration. Isolates of both the CA and S types caused stem rot of Af; some isolates in each colony type caused vascular discoloration whilst others did not. Pathogenicity tests with 22 isolates resulted in stem rot disease severity ratings on Af of 3·1–4·0 and 2·1–4·0 with CA and S type colonies, respectively. The same isolates failed to cause disease on Cattleya, Dendrobium or Phalaenopsis plants. Phylogenetic analysis of partial intergenic spacer sequences showed that these isolates were distinguishable from other formae speciales of Fo and could be separated into two groups correlated with the CA or S type colonies with high bootstrap. Based on pathogenic, morphological and molecular characterizations, the Fo that causes stem rot of Af is proposed to be a new forma specialis, F. oxysporum f. sp. anoectochili, with different pathotypes. 相似文献
18.
水稻褐(紫)鞘病因之探讨 总被引：1，自引：0，他引：1
本文对褐(紫)鞘、鞘腐两种症状的诱发因子进行了描述。采用不同的接种方法,将不同来源的菌株在常规的水稻品种上接种,均可引起褐(紫)鞘和鞘腐二种症状,它们出现的频率随接种方法、品种和菌株的不同而异。作者认为把褐(紫)鞘症状看作为一种新的病害是不能成立的,它只能是水稻叶鞘腐败病的另一种症状。 相似文献
19.
大豆疫霉根腐病是大豆的毁灭性病害。为了深入了解大豆对疫霉菌的分子抗病机制,以大豆疫霉菌1号生理小种游动孢子接种抗性品种绥农10的根部及下胚轴,通过反转录差异显示技术分离到疫霉菌侵染0、0.5、1、2和4h后大豆下胚轴和茎部的差异表达基因,其中至少有8个基因与抗病相关。接种后0.5 h开始上调表达的有肉桂酸-4-羟化酶基因、ATP合成酶β亚基基因,以及类花生泛素结合酶基因;接种后1h和2h依次开始上调表达的有尿苷二磷酸-N-乙酰基-α-D-氨基半乳糖基因和豌豆蓝铜蛋白基因;接种后4 h才上调表达的有TGA型碱性亮氨酸拉链基因、大豆环孢素基因和14-3-3蛋白基因。这8个基因中有1个基因与信号传导有关、4个基因与抗病和防御有关、2个基因与转录调控有关、1个基因与能量代谢有关。研究表明,以上8个基因在疫霉菌游动孢子萌发、侵入大豆和在大豆体内扩展过程中起着重要作用。 相似文献
20.
The role of aggressiveness and competition in the selection of Phytophthora infestans populations 
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下载免费PDF全文 G. K. Young L. R. Cooke S. Watson W. W. Kirk F. M. Perez K. L. Deahl 《Plant pathology》2018,67(7):1539-1551
Selection within populations of Phytophthora infestans was investigated by comparing the aggressiveness of single‐lesion isolates on detached leaflets of four potato cultivars with differing levels of race‐nonspecific resistance to P. infestans. The isolates included 23 representative of Northern Ireland genotypes from the early 2000s, used to inoculate previously reported field trials on competitive selection (2003–2005), plus 12 isolates recovered from the 2003 trial. The cultivars were those planted in the previous trials: Atlantic (blight‐susceptible) and Santé, Milagro and Stirling (partially resistant). Very highly significant variation for latent period, infection frequency and lesion area was found between genotypes and cultivars; differences between genotypes were more marked on the more resistant cultivars, but no one genotype was the most aggressive across all. Detached leaflets were also inoculated with mixtures of isolates from each genotype group at three sporangial concentrations: differences in aggressiveness between genotypes were more apparent at lower concentrations and on the more resistant cultivars. Genotype groups that were the most aggressive on the more resistant cultivars tended to be those selected by the same cultivars in the field. A mixture of all isolates of all genotypes was used to inoculate detached leaflets of the same cultivars. With one exception, single spore isolates recovered from any one leaflet belonged to a single genotype, but different genotypes were recovered from different cultivars. Phytophthora infestans isolates from Northern Ireland showed significant variation for foliar aggressiveness, and pathogen genotypes exhibited differential aggressiveness to partially resistant cultivars and interacted competitively in genotype selection. 相似文献