• The Plant Pathology Journal
• /
• 제34권2호
• /
• pp.139-142
• /
• 2018

Pyrenophoratritici-repentis is the causal agent of tan spot. According to their ability to produce necrosis and/or chlorosis on a set of four differential bread wheats, the isolates of this fungus are currently grouped into eight races. When durum wheat genotypes were added to the differential set, a new virulence type was identified in Algeria. The isolates showing this virulence pattern are unable to attack bread wheat while they cause necrosis in durum genotypes. In this work, characterization of those isolates was based on pathological and molecular aspects. This included inoculation of bread and durum wheat, and virulence gene analysis using PCR and sequencing. The results showed that all isolates caused a resistance on all bread wheats of the differential set, while they produced necrosis in durum. ToxA and ToxB genes were amplified in all isolates, whereas toxb was absent. Sequence analysis for both genes showed no differences with those found in the two functional genes. The presence of two genes, ToxA and ToxB, despite the absence of symptoms usually caused by their products, suggests the existence of a new homologous for these two genes yet unknown. The presence of ToxA in the isolate unable to produce necrosis in Glenlea is reported for the first time.

• The Plant Pathology Journal
• /
• 제22권1호
• /
• pp.28-35
• /
• 2006

Virulence and genetic diversity were studied using 21 isolates of Sclerospora graminicola, the pearl millet downy mildew pathogen collected from major pearl millet growing areas of India. Variability for virulence was determined by inoculating a set of 10 differential hosts with the S. graminicola isolates in a greenhouse. The isolates varied for latent period (6.4 to 11 days), disease incidence (0 to $98\%$), virulence index (0 to 18.7) and oospore-production potential (1 to 4). Among the 21 isolates, Sg 139 (Rajasthan) was the most virulent and Sg 110 (Tamil Nadu) the least virulent. Based on virulence index (disease incidence$\time$slatent $period^{-1}$), the 21 isolates were classified into eight virulence groups. Genetic diversity among isolates was studied using AFLP markers. Based on similarity index of banding pattern, the 21 isolates were clustered into eight genotypic groups. The AFLP groupings, however, did not match with that of the virulence groupings, and these two were found independent. The isolate Sg 139 that remained distinct in both pathogenic and genetic groupings indicated its highly virulent nature. Implications of these results in downy mildew resistance breeding are discussed.

• The Plant Pathology Journal
• /
• 제26권3호
• /
• pp.260-263
• /
• 2010

Scald, caused by Rhynchosporium secalis has been the major yield-reducing factor for barley production during the last decade. In this study, pathogenic groups of R. secalis were identified to obtain a global picture of the assembly of isolates involved in Syrian populations which is essential for the development of scald-resistant barley cultivars. To identify a number of pathogenic groups, 49 isolates collected over ten years from major barley growing areas in Syria were evaluated on five differential barley genotypes. Genotypes presented a continuous range of response from highly susceptible to moderately resistant, but none were immune to the disease. A cluster analysis placed isolates in six distinct differential pathogenic groups. Mean disease rating of 39.24% was the separation point between avirulent and virulent reactions. Isolate Rs46 exhibited distinct differential virulence patterns associated with high frequency across all genotypes. Hence, the data presented here provides crucial information for future selection of isolates to develop durable barley scald resistance.

• Parasites, Hosts and Diseases
• /
• 제44권1호
• /
• pp.15-20
• /
• 2006

Free-living amoebae of the genus Acanthamoeba are causative agents of granulomatous amebic encephalitis and amebic keratitis. Because the virulence of Acanthamoeba culbertsoni cultured in the laboratory is restored by consecutive brain passages, we examined the genes induced in mouse brain-passaged A. culbertsoni by differential display reverse transcriptase polymerase chain reaction (DDRT-PCR). Enhanced A. culbertsoni virulence was observed during the second mouse brain passage, i.e., infected mouse mortality increased from $5\%\;to\;70\%.$ Ten cDNAs induced during mouse brain passage were identified by DDRT-PCR and this was confirmed by northern blot analysis. BlastX searches of these cDNAs indicated the upregulations of genes encoding predictive NADH-dehydrogenase, proteasomal ATPase, and GDP-mannose pyrophosphorylase B, which have previously been reported to be associated with A. culbertsoni virulence factors.

• The Plant Pathology Journal
• /
• 제40권2호
• /
• pp.151-159
• /
• 2024

Bacterial soft rot caused by Pectobacterium carotovorum subsp. carotovorum (Pcc) is one of the most severe diseases in radish cultivation. To control this plant disease, the most effective method has been known to cultivate resistant cultivars. Previously, we developed an efficient bioassay method for investigating resistance levels with 21 resistant and moderately resistant cultivars of radish against a strain Pcc KACC 10421. In this study, our research expanded to investigate the resistance of radish cultivars against six Pcc strains, KACC 10225, KACC 10421, ATCC 12312, ATCC 15713, LY34, and ECC 301365. To this end, the virulence of the six Pcc strains was determined based on the development of bacterial soft rot in seedlings of four susceptible radish cultivars. The results showed that the Pcc strains exhibited different virulence in the susceptible cultivars. To explore the race differentiation of Pcc strains corresponding to the resistance in radish cultivars, we investigated the occurrence of bacterial soft rot caused by the six Pcc strains on the 21 resistant and moderate resistant cultivars. Our results showed that the average values of the area under the disease progress curve were positively correlated with the virulence of the strains and the number of resistant cultivars decreased as the virulence of Pcc strains increased. Taken together, our results suggest that the resistance to Pcc of the radish cultivars commercialized in Korea is more likely affected by the virulence of Pcc strains rather than by race differentiation of Pcc.

• 식물병연구
• /
• 제14권3호
• /
• pp.165-170
• /
• 2008

국내에서 수집한 103 금주의 벼 흰잎마름병 균주를 한국 판별품종과 한 개의 저항성 유전자를 갖고 있는 4개의 준동질 계통에 병원성을 검정하였다. 청청벼, 풍산벼, 한강찰벼, 밀양42호는 저항성 유전자의 배경을 완전히 알 수 없어 벼 흰잎마름병균의 분류에 적합하지 않았다. IRBB101, IRBB103, IRBB105, IRBB107의 계통은 1개의 저항성 유전자를 갖고 있어 벼 흰잎마름병 균주의 레이스를 구분할 수 있었다. 이 계통들은 우리나라 벼 흰잎마름병균의 분류하는 판별품종으로 유용할 것으로 생각된다. 우리나라 벼 흰잎마름병 균주는 4개의 NIL과의 반응에 따라 3개의 레이스로 분류하였다.

• Parasites, Hosts and Diseases
• /
• 제37권4호
• /
• pp.257-263
• /
• 1999

Identification of the genes responsible for the recovery of virulence in brain-passaged Acanthamoeba culbertsoni was attempted via mRNA differential display polymerase chain reaction (mRNA DD-PCR) analysis. In order to identify the regulatory changes in transcription of the virulence related genes by the brain passages, mRNA DD-PCR was performed which enabled the display of differentially transcribed mRNAs after the brain passages. Through mRNA DD-PCR analysis. 96 brain-passaged amoeba specific amplicons were observed and were screened to identify the amplicons that failed to amplify in the non-brain-passaged amoeba mRNAs. Out of the 96 brain-passaged amoeba specific amplicons, 12 turned out to be amplified only from the brain-passaged amoeba mRNAs by DNA slot blot hybridization. The clone, A289C, amplified with an arbitrary primer of UBC ＃289 and the oligo dT$_{11}$-C primer, revealed the highest homology (49.8％) to the amino acid sequences of UPD-galactose lipid transferase of Erwinia amylovora, which is known to act as an important virulence factor. The deduced amino acid sequences of an insert DNA in clone A289C were also revealed to be similar to cpsD, which is the essential gene for the expression of type III capsule in group B streptococcus. Upregulated expression of clone A289C was verified by RNA slot blot hybridization. Similar hydrophobicity values were also observed between A289C (at residues 47-66) and the AmsG gene of E. amylovora (at residues 286-305: transmembrane domains). This result suggested that the insert of clone A289C might play the same function as galactosyl transferase controlled by the AmsG gene in E. amylovora.a.

• Journal of Microbiology
• /
• 제42권2호
• /
• pp.143-146
• /
• 2004

Vancomycin-resistant Enterococcus faecium (VREFM) is becoming a threatening pathogen. We identified a gene called DD1.5K by differential display-PCR, which was preferentially expressed in the bloodstream isolates of VREFM. Due to its amino acid similarity to transfer complex protein, trsE, and tissue-specific expression, this gene may be involved in virulence of VREFM.

• Journal of Microbiology and Biotechnology
• /
• 제15권5호
• /
• pp.1146-1151
• /
• 2005

The yeast Candida albicans has a distinguishing feature, dimorphism, which is the ability to switch between two morphological forms: a budding yeast form and a multicellular invasive filamentous form. This ability has been postulated to contribute to the virulence of this organism. Previously, we reported that the yeast-to-hypha transition in this organism is suppressed by farnesoic acid, a morphogenic autoregulatory substance that accumulates in the medium as the cells proliferate. In this study, using a differential display reverse transcription polymerase chain reaction (DDRT-PCR) technique, we have identified several genes induced in C. albicans by farnesoic acid treatment. These observations indicate that farnesoic acid can alter the expressivity of multiple genes, including the DNA replication machinery and cell-cycle-control proteins.

• The Plant Pathology Journal
• /
• 제36권5호
• /
• pp.450-458
• /
• 2020

Pepper and tomato plants infected with two Clavibacter species, C. capsici and C. michiganensis have shown different patterns of disease development depending on their virulence. Here, we investigated how pepper and tomato plants respond to infection by the high-virulent or low-virulent Clavibacter strains. For this, we chose two strains of each Clavibacter species to show different virulence level in the host plants. Although low-virulent strains showed less disease symptoms, they grew almost the same level as the high-virulent strains in both plants. To further examine the response of host plants to Clavibacter infection, we analyzed the expression patterns of plant defense-related genes in the leaves inoculated with different strains of C. capsici and C. michiganensis. Pepper plants infected with high-virulent C. capsici strain highly induced the expression of CaPR1, CaDEF, CaPR4b, CaPR10, and CaLOX1 at 5 days after inoculation (dai), but their expression was much less in low-virulent Clavibacter infection. Expression of CaSAR8.2 was induced at 2 dai, regardless of virulence level. Expression of GluA, Pin2, and PR2 in tomato plants infected with high-virulent C. michiganensis were much higher at 5 dai, compared with mock or low-virulent strain. Expression of PR1a, Osmotin-like, Chitinase, and Chitinase class 2 was increased, regardless of virulence level. Expression of LoxA gene was not affected by Clavibacter inoculation. These results suggested that Clavibacter infection promotes induction of certain defense-related genes in host plants and that differential expression of those genes by low-virulent Clavibacter infection might be affected by their endophytic lifestyle in plants.