Soybean Root Rot Research Articles

Genetic Diversity and Biological Control of Rhizoctonia solani Associated with Root Rot of Soybean in Assiut Governorate, Egypt

Genetic Diversity and Biological Control of Rhizoctonia solani Associated with Root Rot of Soybean in Assiut Governorate, Egypt Rhizoctonia solani Kuhn (Teleomorph: Thanatephorus cucumeris) is considered one of the most destructive soil and seed-borne plant pathogens infecting various agricultural crops including soybean. Study on genetic diversity of the pathogen can provide information on its behavior in field as well as its pathogenicity. We isolated five isolates from R. solani and tested that for pathogenicity test our results indicate that, all tested isolates were able to infect soybean plants causing root rot with different degrees of virulence. Isolates R5 showed the highest pathogenic capability and gave high significantly root rot rating.

Enhance Suppressive Effect of Compost on Soybean Rhizoctonia Root Rot by Soil Treatment with Trichoderma harzianum

Enhance Suppressive Effect of Compost on Soybean Rhizoctonia Root Rot by Soil Treatment with Trichoderma harzianum This study deals with in vitro, under greenhouse, and field efficacy of Trichoderma harzianum (Th1 and Th2), and two types of compost, plant compost (PC) and animal compost (AC) to control the soybean root rot disease caused by Rhizoctonia solani. In vitro study indicated that, Trichoderma spp. isolate Nos. 1 and 2 were the most effective on the pathogen growth, also both composts at 50% concentration were effective on the growth of the pathogen.

First report of root and stem rot of soybean caused by Phytophthora sojae in Mato Grosso do Sul State, Brazil

Kaufm. &Gerd. is a widespread problem in the southern region of Brazil,affecting most areas where soybeans are grown. However, itsoccurrence in the central region of the country is unusual. In Brazil,this disease was first observed in Rio Grande do Sul State in 1995(Costamilan et al. Ocorrencia de

Phylogenetic and transcriptional analysis of an expanded bZIP transcription factor family in Phytophthora sojae

BackgroundBasic leucine zipper (bZIP) transcription factors are present exclusively in eukaryotes and constitute one of the largest and most diverse transcription factor families. The proteins are responsible for central developmental and physiological processes in plants, animals, and fungi, including the pathogenicity of fungal plant pathogens. However, there is limited understanding of bZIPs in oomycetes, which are fungus-like organisms in the kingdom Stramenopila. Oomycetes include many destructive plant pathogens, including the well-studied species Phytophthora sojae, which causes soybean stem and root rot.ResultsCandidate bZIPs encoded in the genomes of P. sojae and four other oomycetes, two diatoms, and two fungal species were predicted using bioinformatic methods. Comparative analysis revealed expanded numbers of bZIP candidates in oomycetes, especially the Phytophthora species, due to the expansion of several novel bZIP classes whose highly conserved asparagines in basic DNA-binding regions were substituted by other residues such as cysteine. The majority of these novel bZIP classes were mostly restricted to oomycetes. The large number of novel bZIPs appears to be the result of widespread gene duplications during oomycete evolution. The majority of P. sojae bZIP candidates, including both conventional and novel bZIP classes, were predicted to contain canonical protein secondary structures. Detection of gene transcripts using digital gene expression profiling and qRT-PCR suggested that most of the candidates were not pseudogenes. The major transcriptional shifts of bZIPs occurred during the zoosporangia/zoospore/cyst and host infection stages. Several infection-associated bZIP genes were identified that were positively regulated by H2O2 exposure.ConclusionsThe identification of large classes of bZIP proteins in oomycetes with novel bZIP motif variants, that are conserved and developmentally regulated and thus presumably functional, extends our knowledge of this important family of eukaryotic transcription factors. It also lays the foundation for detailed studies of the roles of these proteins in development and infection in P. sojae and other oomycetes.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-14-839) contains supplementary material, which is available to authorized users.

Colonization of Clonostachys rosea on soybean root grown in media inoculated with Fusarium graminearum

Soybean root rot, caused by Fusarium graminearum, is an important disease in Canada. Clonostachys rosea has been reported to provide protection against plant pathogens in different crops. The objectives of this study were to determine if a strain of C. rosea, ACM 941, can colonize soybean root that were grown in media inoculated with F. graminearum, and to determine if the distribution of C. rosea was different at different root depths. There were three treatments in this study, which included a control (CK) using normal seed without any fungal treatments; seed inoculated with ACM 941 (ACM); and seed inoculated ACM 941 and growing media inoculated with F. graminearum (ACM +Fg). Results showed that the colony forming unit (CFU) of ACM 941 was lower on the tap roots and secondary roots growing 8–13 cm below ground level than sections of roots growing 0–3 cm or 3–8 cm below ground level. ACM 941 was found in roots at the third day after soybean seed was planted, and maintained high CFU most of the time during soybean growth. Inoculation with F. graminearum had no effect on CFU of ACM 941. The ACM 941 strain colonized soybean root rapidly and was not affected by the existence of F. graminearum, suggesting that ACM 941 can successfully compete with F. graminearum, may have potential as an effective biocontrol agent for protecting soybean from the Fusarium root rot.

The Phytophthora sojae Avr1d Gene Encodes an RxLR-dEER Effector with Presence and Absence Polymorphisms Among Pathogen Strains

Soybean root and stem rot is caused by the oomycete pathogen Phytophthora sojae. The interaction between P. sojae and soybean fits the "gene-for-gene" hypothesis. Although more than 10 P. sojae avirulence (Avr) effectors have been genetically identified, nearly half of genetically defined avr genes have been cloned. In a previous bioinformatic and global transcriptional analysis, we identified a P. sojae RxLR effector, Avr1d, which was 125 amino acids in length. Mapping data demonstrated that Avr1d presence or absence in the genome was co-segregated with the Avr1d avirulence phenotype in F2 populations. Transient expression of the Avr1d gene using co-bombardment in soybean isogenic lines revealed that this gene triggered a hypersensitive response (HR) in the presence of Rps1d. Sequencing of Avr1d genes in different P. sojae strains revealed two Avr1d alleles. Although polymorphic, the two Avr1d alleles could trigger Rps1d-mediated HR. P. sojae strains carrying either of the alleles were avirulent on Rps1d soybean lines. Avr1d was upregulated during the germinating cyst and early infection stages. Furthermore, transient expression of Avr1d in Nicotiana benthamiana suppressed BAX-induced cell death and enhanced P. capsici infection. Avr1d also suppressed effector-triggered immunity induction by associating with Avr1b and Rps1b, suggestive of a role in suppressing plant immunity.

Resistance of soybean cultivars (lines) against Fusarium species causing soybean root rot in northeast China

In this study,408 soybean cultivars(lines) were identified for resistance to the strong virulent strains of Fusarium oxysporum and F.solani from northeast China.Results showed that the resistant resources of soybean against F.oxysporum and F.solani were abundant in northeast China.Among 357 soybean cultivars(lines) from Heilongjiang Province,resistant cultivars against F.solani and F.oxysporum accounted for 39.03% and 62.37% respectively.Among 27 soybean cultivars from Jilin Province,resistant cultivars against F.solani and F.oxysporum accounted for 23.46% and 46.91% respectively.Among 24 cultivars from Liaoning Province,resistant cultivars against F.solani and F.oxysporum accounted for 25.00% and 61.11% respectively.Jiaojin05-SH,Heinong65,D09-005,D09-072 and D09-077 from Heilongjiang Province showed resistance against strong virulent strains of F.solani and F.oxysporum from northeast China.There were differences in the virulence of F.solani and F.oxysporum strains from different provinces to the same soybean cultivar(line),so the local Fusarium strain should be selected for resistance identification.Ten major soybean cultivars from northeast China were identified for resistance against eight Fusarium species with strong and weak virulence.The results showed that resistant interac-tions accounted for 74.38% among the 160 interactions,indicating that the resistance against Fusarium root rot existed abundant in soybean cultivars.Suinong28 and Dandou13 were immune to weak virulent F.avenaceum,Heinong44 and dongnong2037 immunized to weak virulence F.oxysporum;and at the same time there was no cultivar resistant to all eight Fusarium species.According to the proportion of resistance interactions and the average disease index,the resistant frequency of ten cultivars descending order were Jiunong28,Jiyu35,Suinong28,Tiedou44,Heinong44,Dandou13,Kenfeng16,Dongnong2037,Liaodou17,Hefeng55.Cultivars shown resistance to both Fusarium strong and weak virulence strains accounted for 71.25%,therefore virulence of Fusarium strain was not taken into account for identifying resistance of soybean cultivar to Fusarium species.

Prevalence, pathogenicity and cultivar resistance of Fusarium and Rhizoctonia species causing soybean root rot

Zhang, J. X., Xue, A. G., Cober, E. R., Morrison, M. J., Zhang, H. J., Zhang, S. Z. and Gregorich, E. 2013. Prevalence, pathogenicity and cultivar resistance of Fusarium and Rhizoctonia species causing soybean root rot. Can. J. Plant Sci. 93: 221–236. Root rot complex, caused by Fusarium and Rhizoctonia species, is a major soybean disease in Canada. We isolated nine Fusarium and Rhizoctonia species including F. oxysporum (Fo), F. graminearum (Fg), F. solani (Fs), F. avenaceum (Fa), F. tricinctum (Ft), F. sporotrichioides (Fsp), F. equiseti (Fe), F. poae (Fp), and R. solani (Rs) from soybean roots in eastern Ontario, Canada. The isolation results indicated that Fo was the most prevalent species while Fa, Fsp, and Fp were the least frequent species in the soybean rhizosphere. Numbers of Fo, Fs, Fg, and Rs isolates recovered from adult plant roots were significantly greater than those from seedling roots (P<0.01). The Rs, Fg and Fsp isolates were significantly more abundant in the no-till field than in the tilled field (P<0.01). Based on the greenhouse assays, Rs, Fg, and Fa were the most pathogenic species, while Fe and Fsp were the least pathogenic to soybean. The field resistance evaluation, based on the root rot severity, identified 21, 17, 30, and 3 out of 70 cultivars among the most tolerant to Fg, Fo, Fs, and Rs, respectively. A few of the cultivars showed partial resistance to multiple species, based on root rot severity and reduction in their seedling emergence, plant height, and root dry weight, but no cultivar was found to partially resist all four species. There was no correlation (P>0.05) between root rot severity and the reduction in seedling emergence, plant height, or root dry weight.

Rhizobium japonicum as a biocontrol agent of soybean root rot disease caused by Fusarium solani and Macrophomina phaseolina

The activity of Rhizobium japonicum against the soil-borne pathogens Fusarium solani and Macrophomina phaseolina as causative agents of soybean root rot disease in both culture medium and soil was evaluated. Rhizobial culture filtrate caused an inhibition of the fungal radial growth of Fusarium solani and Macrophomina phaseolina on potato dextrose agar medium amended with the filtrate compared with control. The addition of rhizobial culture suspension to the soil contaminated by the two pathogens, Fusarium solani and Macrophomina phaseolina and their interaction, in pots, improved seed germination percentages and reduced the root rot disease index significantly. The sowing of rhizobial coated seeds in soil contaminated by Fusarium solani and Macrophomina phaseolina separately and in combination, in the field, increased seed germination significantly and induced a high reduction in disease severity for the same previous combination under field conditions. These results indicate that rhizobia could be an important element in root rot disease management.

First Report of Clonostachys rosea Causing Root Rot of Soybean in the United States.

Multiple fungal species have been associated with root rot of soybean (Glycine max) in the United States, but root rot in Minnesota (MN) also occurs in plants not known to be infected with previously reported pathogens (1). Soybean plants that lacked foliar symptoms, but exhibited taproot and lateral root necrosis were observed in 15 fields from nine counties in MN during 2007 and 2008. Plants were arbitrarily dug up at the R3 growth stage in July as part of a root rot study. Roots were washed, surface disinfested in 0.5% NaOCl for 3 min, rinsed in deionized water, dried, and embedded in potato dextrose agar (PDA). Thirty isolates with morphological characteristics consistent with those of Clonostachys rosea were recovered in total from necrotic lesions on different plants from all fields (3). For further morphological characterization, cultures were grown on PDA for 1 week at 24°C in the dark. Colonies were 39 to 46 mm in diameter, yellowish-white, and the surface was felty to tomentose with thick aerial hyphae. Primary conidiophores were Verticillium-like with two to three levels. The stipe length measured 65 to 105 μm and the base width was 5 μm. Primary conidia were smooth, hyaline, slightly curved, with an average length and width of 7 to 9 × 2.6 to 3 μm. Secondary conidiophores were penicillate with two or three whorls of phialides. The stipe length measured 50 to 75 μm, base width was 5 μm, and penicillus height was 25 to 35 μm. Secondary conidia were 5 to 6 × 2.5 μm. Perithecia were not produced. The identity of isolates was confirmed by sequencing the internal transcribed spacer (ITS) locus using the primers ITS1F/ITS4. BLAST analysis of the sequences in the NCBI database resulted in a 99.8 to 100% match for both C. rosea and its teleomorph Bionectria ochroleuca (e.g., HM751081, GU256766). Each isolate was tested for pathogenicity on soybean by initially growing it on sterile sorghum grain for 2 weeks at 23°C. Sterile sorghum was used for control plants. Seeds of soybean 'AG2107' were planted in 11.4-cm square pots containing pasteurized potting mix and a 25-cm3 layer of infested or sterile sorghum placed ~1 cm below the seeds. Two replicate pots containing four plants each were used per treatment and the experiment was repeated once. Root rot was assessed 28 days after planting in a greenhouse at 23°C day and 18°C night with a 14-h photoperiod. Twenty-eight of 30 C. rosea isolates caused taproot necrosis on inoculated plants in both experiments, whereas control roots did not exhibit necrosis. Approximately 6% of inoculated plants also developed interveinal chlorosis and marginal necrosis on trifoliates. Isolations were attempted from roots of all plants, and the isolates recovered from inoculated plants were identified as C. rosea based on morphology and ITS sequences. This fungus was not isolated from control plants. C. rosea was also isolated from petioles of symptomatic trifoliates, indicating systemic colonization of the plants. To our knowledge, this is the first report of C. rosea causing root rot of soybean and systemically colonizing soybean. This fungus may have been previously isolated from asymptomatic soybean plants and identified as Gliocladium roseum (2). The impact of this fungus on soybean production is unknown.

Effects of long-term chlorimuron-ethyl application on the diversity and antifungal activity of soil Pseudomonas spp. in a soybean field in Northeast China

The herbicide chlorimuron-ethyl has been applied widely for weed control in farmland, especially in soybean fields in China over the past decade, but the chronic effects of this herbicide on soil microorganisms, particularly Pseudomonas spp., is not well understood. Taking a continuously cropped soybean field in the town of Fuyuan-a soybean production base of Heilongjiang Province in Northeast China-as a case study, soil samples were collected from plots having received 0-, 5-, and 10-year applications of chlorimuron-ethyl (30 g active component of chlorimuron-ethyl/ha/year) to study the abundance and diversity of Pseudomonas spp. Meanwhile, an in vitro assay was used to examine the antifungal activities of isolated Pseudomonas spp. against soil-borne pathogens (Fusarium graminearum, Fusarium oxysporum, and Rhizoctonia solani) causing soybean root rot disease. The production of siderophore, hydrogen cyanide (HCN), and lytic enzymes (cellulase, pectinase, and chitinase) by Pseudomonas spp. was also investigated. With 5- and 10- year chlorimuron-ethyl application, the numbers of soil Pseudomonas spp. decreased from 121 x 10(2) CFU/g dry soil in the control to 40 x 10(2) CFU/g dry soil and 13 x 10(2) CFU/g dry soil, and the Shannon index values decreased from 6.23 to 3.71 and 1.73, respectively. The numbers of antifungal Pseudomonas spp. also decreased, and the proportions of Pseudomonas spp. with antifungal activities against the different test pathogens altered. All the antifungal Pseudomonas spp. could produce siderophore and HCN but not lytic enzymes. The results suggest that long-term application of chlorimuron-ethyl in continuously cropped soybean field had negative effects on the abundance and diversity of soil Pseudomonas spp., including species with different antifungal activities against pathogens. Siderophore and HCN rather than lytic enzymes formed the antifungal metabolites of Pseudomonas spp., and the number of antifungal Pseudomonas that can produce siderophore and HCN decreased markedly under application of chlorimuron-ethyl, especially after 10-year application.

Biological potential of Pseudomonas sp. BS1 in the control of Phytophthora root rot of soybean

In this study, the biological potential of Pseudomonas sp. BS1 in the control ofPhytophthora root rot of soybean was investigated. Fermentation filtrates ofPseudomonas sp. BS1 inhibited zoosporangium formation and zoospore germination ofPhytophthora sojae (P. sojae), and the inhibitory effect gradually weakened with the increasing filtrate dilution. It had a relatively strong inhibition on hyphal growth of P. sojae, and the inhibition rate of stock solutions reach 95.9%; as dilution increased, the inhibition gradually weakened. The results indicated that Pseudomonas sp. BS1 can inhibit normal growth and development of P. sojae, and pathogen reproduction. Through investigating the controlling effect of Pseudomonas sp. BS1 fermentation filtrates on Phytophthora root rot of soybean under greenhouse conditions, we found that pre-treatment with fermentation filtrates had a preventive effect on disease caused by P. sojae, and post-inoculation treatment with fermentation filtrates had a therapeutic effect. Simultaneous treatment with fermentation filtrates and zoospore suspension had best controlling effects. These results will provide a theoretical basis for the biological control of Phytophthora root rot of soybean using Pseudomonas sp. BS1. Key words: Pseudomonas, Phytophthora, zoosporangium, zoospore, biological control.

Transient silencing mediated by in vitro synthesized double-stranded RNA indicates that PsCdc14 is required for sporangial development in a soybean root rot pathogen

In many eukaryotic organisms, Cdc14 phosphatase regulates multiple biological events during anaphase and is essential for mitosis. It has been shown that Cdc14 is required for sporulation in the potato blight pathogen Phytophthora infestans; however, the role that the Cdc14 homolog (PsCdc14) plays in the soil-borne soybean root rot pathogen P. sojae remains ambiguous. PsCdc14 is highly expressed in sporulation, zoospore, and cyst life stages, but not in vegetative mycelia and infection stages, suggesting that it contributes to asexual reproduction and thus the spread of the disease. Double-stranded RNA (dsRNA) mediates gene silencing, a post-transcriptional and highly conserved process in eukaryotes, involving specific gene silencing through degradation of target mRNA. We combined in vitro dsRNA synthesis and a polyethylene glycol-mediated transformation system to construct a dsRNA-mediated transient gene silencing system; and then performed a functional analysis of PsCdc14 in P. sojae. PsCdc14 mRNA was dramatically reduced in transformants after protoplasts were exposed in in vitro synthesized PsCdc14 dsRNA, resulting in low sporangial production and abnormal development in P. sojae silencing lines. Furthermore, dsRNA-mediated transient gene silencing could enable elucidation of P. sojae rapid gene function, facilitating our understanding of the development and pathogenicity mechanisms of this oomycete fungus.

Phytophthora sojae avirulence effector Avr3b is a secreted NADH and ADP-ribose pyrophosphorylase that modulates plant immunity.

Plants have evolved pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI) to protect themselves from infection by diverse pathogens. Avirulence (Avr) effectors that trigger plant ETI as a result of recognition by plant resistance (R) gene products have been identified in many plant pathogenic oomycetes and fungi. However, the virulence functions of oomycete and fungal Avr effectors remain largely unknown. Here, we combined bioinformatics and genetics to identify Avr3b, a new Avr gene from Phytophthora sojae, an oomycete pathogen that causes soybean root rot. Avr3b encodes a secreted protein with the RXLR host-targeting motif and C-terminal W and Nudix hydrolase motifs. Some isolates of P. sojae evade perception by the soybean R gene Rps3b through sequence mutation in Avr3b and lowered transcript accumulation. Transient expression of Avr3b in Nicotiana benthamiana increased susceptibility to P. capsici and P. parasitica, with significantly reduced accumulation of reactive oxygen species (ROS) around invasion sites. Biochemical assays confirmed that Avr3b is an ADP-ribose/NADH pyrophosphorylase, as predicted from the Nudix motif. Deletion of the Nudix motif of Avr3b abolished enzyme activity. Mutation of key residues in Nudix motif significantly impaired Avr3b virulence function but not the avirulence activity. Some Nudix hydrolases act as negative regulators of plant immunity, and thus Avr3b might be delivered into host cells as a Nudix hydrolase to impair host immunity. Avr3b homologues are present in several sequenced Phytophthora genomes, suggesting that Phytophthora pathogens might share similar strategies to suppress plant immunity.

Antagonistic Mechanism of Fusarium Oxysporum of Soybean Root Rot by Bacillus Subtilis

. Fusarium oxysporum is a soil-borne fungus that infects soybean roots and causes soybean root rot, a widespread and destructive soybean disease. The potential strain X6 belonged to Bacillus subtilis for controlling soybean root rot. And antagonistic mechanism of the pathogenic Fusarium oxysporum of soybean root rot by B. subtilis X6 was investigated. The antagonistic mechanism of strain X6 againt F. oxysporum can effectively inhibit mycelial growth, spores bearing and germination. After treated with metabolic product of strain X6, protoplast from the hyphae became abnormal. The activity effect of metabolic product of strain X6 was sensitive to temperature. So the study lay the groundwork for further research and application.

Proteomics study of changes in soybean lines resistant and sensitive to Phytophthora sojae.

BackgroundPhytophthora sojae causes soybean root and stem rot, resulting in an annual loss of 1-2 billion US dollars in soybean production worldwide. A proteomic technique was used to determine the effects on soybean hypocotyls of infection with P. sojae.ResultsIn the present study, 46 differentially expressed proteins were identified in soybean hypocotyls infected with P. sojae, using two-dimensional electrophoresis and matrix-assisted laser desorption/ionization tandem time of flight (MALDI-TOF/TOF). The expression levels of 26 proteins were significantly affected at various time points in the tolerant soybean line, Yudou25, (12 up-regulated and 14 down-regulated). In contrast, in the sensitive soybean line, NG6255, only 20 proteins were significantly affected (11 up-regulated and 9 down-regulated). Among these proteins, 26% were related to energy regulation, 15% to protein destination and storage, 11% to defense against disease, 11% to metabolism, 9% to protein synthesis, 4% to secondary metabolism, and 24% were of unknown function.ConclusionOur study provides important information on the use of proteomic methods for studying protein regulation during plant-oomycete interactions.

MicroRNAs Involved in the Pathogenesis of Phytophthora Root Rot of Soybean ( Glycine max)

Phytophthora root rot is one of the most prevalent diseases in the world, which can infect the seedlings and plants, with substantial negative impact on soybean yield and quality. MicroRNAs (miRNAs) are a class of post-transcriptional regulators of gene expression during growth and development of organisms. A soybean disease-resistance variety Suinong 10 was inoculated with Phytophthora sojae race No. 1, and the specific miRNA resistant expression profile was acquired by microarray for the first time. Different expressional miRNAs have been found after comparing the results of the treated sample with the control sample. Furthermore, the target genes of different expressional miRNAs were predicted. Two miRNAs, cbr-mir-241 and ath-miR854a, regulated the disease-resistance process directly through their targets, some enzymes. Another two miRNAs, gma-miR169a and ath-miR169h, participated in disease-resistance regulation as transcription factors. Similarly, one miRNA, ptc-miR164f, has been reported to regulate the plant development. All of these studies would be served as the foundation for exploring the resistance mechanism.

Differential Gene and Protein Expression in Soybean at Early Stages of Incompatible Interaction with Phytophthora sojae

Soybean root and stem rot caused by Phytophthora sojae is a destructive disease worldwide. Using genetic resistance is an important and major component in the integrated pest management of this disease. To understand molecular mechanisms of root and stem rot resistance in soybeans, the gene and protein expression in hypocotyls and stems of variety Suinong 10 carrying resistance genes Rps1a and Rps2 was investigated by using mRNA differential display reverse transcription PCR and two-dimensional electrophoresis at 0, 0.5, 1, 2, and 4 h after inoculation with P. sojae race 1. The results of the comparison of gene and protein expression showed that at least eight differential fragments at the transcriptional level were related to metabolic pathway, phytoalexin, and signal transduction in defense responses. Sequence analyses indicated that these fragments represented cinnamic acid 4-hydroxylase gene, ATP β gene coding ATP synthase β subunit and ubiquitin-conjugating enzyme gene which upregulated at 0.5 h post inoculation, blue copper protein gene and UDP-N-acetyl-α-D-galactosamine gene which upregulated at 2 h post inoculation, TGA-type basic leucine zipper protein TGA1.1 gene, cyclophilin gene, and 14-3-3 protein gene which upregulated at 4 h post inoculation. Three resistance-related proteins, α-subunit and β-subunit of ATP synthase, and cytochrome P450-like protein, were upregulated at 2 h post inoculation. The results suggested that resistance-related multiple proteins and genes were expressed in the recognition between soybean and P. sojae during zoospore germination, penetration and mycelium growth of P. sojae in soybean.

Characterization of intronic structures and alternative splicing in Phytophthora sojae by comparative analysis of expressed sequence tags and genomic sequences

The oomycetes, a distinct phylogenetic lineage of fungus-like microorganisms, are heterokonts (stramenopiles) belonging to the supergroup Chromalveolata. Although the complete genomic sequences of a number of oomycetes have been reported, little information regarding the introns therein is available. Here, we investigated the introns of Phytophthora sojae, a pathogen that causes soybean root and stem rot, by a comparative analysis of genomic sequences and expressed sequence tags. A total of 4013 introns were identified, of which 96.6% contained canonical splice sites. The P. sojae genome possessed features distinct from other organisms at 5' splice sites, polypyrimidine tracts, branch sites, and 3' splice sites. Diverse repeating sequences, ranging from 2 to 10 nucleotides in length, were found at more than half of the intron-exon boundaries. Furthermore, 122 genes underwent alternative splicing. These data indicate that P. sojae has unique splicing mechanisms, and recognition of those mechanisms may lead to more accurate predictions of the location of introns in P. sojae and even other oomycete species.

Occurrence of Rhizoctonia Root Rot of Soybean Caused by Rhizoctonia solani AG-2-2Ⅳ and Adzuki Bean Caused by R. solani AG-1 IB in Commercial Fields of Hokkaido

Occurrence of <i>Rhizoctonia </i>Root Rot of Soybean Caused by <i>Rhizoctonia solani </i>AG-2-2Ⅳ and Adzuki Bean Caused by <i>R. solani </i>AG-1 IB in Commercial Fields of Hokkaido