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Late blight (Phytophthora infestans) can have devastating effects on tomato production over the whole world. Most of the commercial cultivars of tomato, Solanum lycopersicum, are susceptible. Qualitative and quantitative resistanc...
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Late blight (Phytophthora infestans) can have devastating effects on tomato production over the whole world. Most of the commercial cultivars of tomato, Solanum lycopersicum, are susceptible. Qualitative and quantitative resistance has been described in wild relatives of tomato. In general qualitative resistance can more easily be overcome by newly evolved isolates. Screening of three S. habrochaites accessions (LA1033, LA2099 and LA1777) through a whole plant assay showed that accession LA1777 had a good level of resistance to several isolates of P. infestans. To explore the potential in this wild species, an introgression line (IL) population of S. habrochaites LA1777 was used to screen individual chromosome regions of the wild species by a detached leaf assay. Two major isolates (T-1,T-2 and T-1,T-2,T-4) were used and two parameters were measured: lesion size (LS), and disease incidence (DI). Substantial variation was observed between the individual lines. QTLs were identified for LS but not for DI. The presence of five QTLs derived from LA1777 (Rlbq4a, Rlbq4b, Rlbq7, Rlbq8 and Rlbq12) results in unambiguous higher levels of resistance. All QTLs co-localized with previously described QTLs from S. habrochaites LA2099 except QTL Rlbq4b, which is therefore a novel QTL.
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A rice gene, OsBIANK1, encoding a protein containing a typical ankyrin repeat domain, was cloned and identified. The OsBIANK1 protein, consisting of 329 amino acids, contains a conserved ankyrin repeat domain with two ankyrin repe...
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A rice gene, OsBIANK1, encoding a protein containing a typical ankyrin repeat domain, was cloned and identified. The OsBIANK1 protein, consisting of 329 amino acids, contains a conserved ankyrin repeat domain with two ankyrin repeats organized in tandem and was showed to be localized on cytoplasmic membrane during transient expression in onion epidermal cells. Expression of OsBIANK1 was induced by treatment with benzothiadiazole (BTH), a chemical inducer capable of inducing disease resistance response in rice. In BTH-treated rice seedlings, expression of OsBIANK1 was further induced by infection with Magnaporthe grisea, the rice blast fungus, as compared with those in water-treated seedlings. Our preliminary results confirm previous evidences that OsBIANK1 may be involved in regulation of disease resistance response in rice.
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Controlling health of livestock has become of considerable importance to the aquaculture industry. Selective breeding of animals with increased resistance to pathogens is likely to complete efficiently the use of drugs, vaccines o...
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Controlling health of livestock has become of considerable importance to the aquaculture industry. Selective breeding of animals with increased resistance to pathogens is likely to complete efficiently the use of drugs, vaccines or prophylactic approaches that may be difficult to implement. A review of the scientific literature shows that the prospect of selecting for increased resistance is quite hopeful in both molluscs and fish. Yet, selecting for disease resistance is hampered by the difficulty to measure the resistance of individuals. Prospects for the development of that would predict the genetic merit of individuals without pathogen challenge are presented. The breeding schemes that may be implemented for fish and molluscs in the French industry are discussed.
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Small-scale laboratory challenges were use to assess the possible clinical significance of disc diffusion susceptibility measurements. The evidence suggests that Aeromonas salmonicida strains giving a zone size of 18-20 mm for dis...
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Small-scale laboratory challenges were use to assess the possible clinical significance of disc diffusion susceptibility measurements. The evidence suggests that Aeromonas salmonicida strains giving a zone size of 18-20 mm for discs containing 2 mu g oxolinic acid should be considered as being clinically resistant.
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The ascorbic acid (AA)-deficient Arabidopsis thaliana vtc1-1 mutant exhibits increased resistance to the virulent bacterial pathogen Pseudomonas syringae. This response correlates with heightened levels of salicylic acid (SA), whi...
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The ascorbic acid (AA)-deficient Arabidopsis thaliana vtc1-1 mutant exhibits increased resistance to the virulent bacterial pathogen Pseudomonas syringae. This response correlates with heightened levels of salicylic acid (SA), which induces antimicrobial pathogenesis-related (PR) proteins. To determine if SA-mediated, enhanced disease resistance is a general phenomenon of AA deficiency, to elucidate the signal that stimulates SA synthesis, and to identify the biosynthetic pathway through which SA accumulates, we studied the four AA-deficient vtc1-1, vtc2-1, vtc3-1, and vtc4-1 mutants. We also studied double mutants defective in the AA-biosynthetic gene VTC1 and the SA signaling pathway genes PAD4, EDS5, and NPR1, respectively. All vtc mutants were more resistant to P. syringae than the wild type. With the exception of vtc4-1, this correlated with constitutively upregulated H2O2, SA, and messenger RNA levels of PR genes. Double mutants exhibited decreased SA levels and enhanced susceptibility to P. syringae compared with the wild type, suggesting that vtc1-1 requires functional PAD4, EDS5, and NPR1 for SA biosynthesis and pathogen resistance. We suggest that AA deficiency causes constitutive priming through a buildup of H2O2 that stimulates SA accumulation, conferring enhanced disease resistance in vtc1-1, vtc2-1, and vtc3-1, whereas vtc4-1 might be sensitized to H2O2 and SA production after infection.
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The presence of seedling resistance to leaf scald in Australian barley varieties and breeding lines has been determined using differential pathotypes of Rhynchosporium secalis. The previously described resistance genes Rrs1, Rrs2 ...
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The presence of seedling resistance to leaf scald in Australian barley varieties and breeding lines has been determined using differential pathotypes of Rhynchosporium secalis. The previously described resistance genes Rrs1, Rrs2 and Rh4/Rh10 have been identified as well as other resistance sources that show different reactions against the isolates. Seedling resistance in the barley variety Skiff, Rh (Skiff), has been found to react in an identical fashion to seedling resistance in the variety Barque suggesting the same gene/allele is present in these varieties. Virulence in R. secalis has been detected against almost all barley resistance sources tested, reinforcing previous experience that single gene resistance to scald is not a safe option. The differential isolates are being used to detect resistance genes in breeding lines as a service to barley breeding programs. They are also being used to detect novel resistances and will prove useful to breeders in building gene pyramids to try and develop varieties with more durable resistance.
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AC Taber is a hard red spring wheat cultivar that has had long-lasting resistance to the leaf rust fungus Puccinia triticina. The objective of this study was to determine the chromosome location of the leaf rust resistance genes i...
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AC Taber is a hard red spring wheat cultivar that has had long-lasting resistance to the leaf rust fungus Puccinia triticina. The objective of this study was to determine the chromosome location of the leaf rust resistance genes in AC Taber. The leaf rust-susceptible cultivar Thatcher was crossed with AC Taber to develop an F6 recombinant inbred line (RIL) population. The RILs and parents were evaluated for segregation of leaf rust resistance in five field plot tests and in two seedling tests to race BBBDB of P. triticina. A genetic map of the RIL population was developed using 90,000 single nucleotide polymorphism markers with the Illumina Infinium iSelect 90K wheat bead array. Quantitative trait loci (QTLs) with significant effects for lower leaf rust severity in the field plot tests were found on chromosomes 2BS and 3BS. The same QTLs also had significant effects for lower infection type in seedlings to leaf rust race BBBDB. The gene on 2BS was the adult plant resistance gene Lr13, and the gene on 3BS mapped to the same region as the adult plant resistance gene Lr74 and other QTLs for leaf rust resistance. Kompetitive allelespecific PCR assay markers linked to the 2BS and 3BS regions were developed and should be useful for marker-based selection of these genes.
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The dominant Pvr4 gene identified in Capsicum annuum cv. Criollo de Morelos 334 (CM334) is frequently used in pepper cultivars because it possesses one of the largest spectra of action among plant virus resistance genes. This gene...
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The dominant Pvr4 gene identified in Capsicum annuum cv. Criollo de Morelos 334 (CM334) is frequently used in pepper cultivars because it possesses one of the largest spectra of action among plant virus resistance genes. This gene was previously shown to confer efficient resistance to all known Potato virus Y isolates, to Pepper mottle virus, to Pepper yellow mosaic virus and to Ecuadorian rocoto virus. This study showed that the W4 line, derived from CM334 and carrying Pvr4, was also resistant to Peru tomato mosaic virus and Pepper severe mosaic virus, but not to Pepper veinal mottle virus, Chilli veinal mottle virus or Tobacco etch virus. It was noticed that the phenotype of the resistance was atypical since, in the W4 line, hypersensitive reaction or extreme resistance could be observed, depending on virus isolates and inoculated organs. Despite the large deployment of Pvr4 in hybrid cultivars, the numerous tests performed in controlled conditions and the use of W4 serial back-inoculations with potyvirus isolates controlled by this line, no virulent variant isolates were obtained. However, it was shown that the use of graft inoculation experiments allow PVY virulent variants to be selected.
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Preliminary field observations in our maize breeding nurseries indicated that breeding for improved resistance to gibberella ear rot (Fusarium graminearum) in maize may indirectly select for resistance to another ear disease, comm...
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Preliminary field observations in our maize breeding nurseries indicated that breeding for improved resistance to gibberella ear rot (Fusarium graminearum) in maize may indirectly select for resistance to another ear disease, common smut (Ustilago zeae). To investigate this, we compared the disease severity ratings obtained on 189 maize inbreds, eight of which included our inbreds developed with selection for gibberella ear rot resistance after field inoculation and breeding for 8-10 years. No correlation was found between disease severities for the 189 inbreds but the eight gibberella-resistant lines were consistently more resistant to smut. To further examine this relationship and to determine if these eight inbreds would be useful for developing inbreds with either common smut or fusarium ear rot (F. verticilliodes) resistance, we conducted a Griffing's diallel analysis on six inbreds of maize, four with high levels of gibberella ear rot resistance representing all of the pedigree groups in our eight gibberella lines, and two with very low levels. Our most gibberella ear rot resistant inbreds, CO433 and CO441, had the lowest disease ratings for all three diseases, the consistently largest general combining ability effects and several significant specific combining ability effects. It was concluded that some inbreds bred specifically for gibberella ear rot would also be useful in breeding for resistance to common smut and fusarium ear rot.
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Abstract Southern soybean stem canker, caused by Diaporthe aspalathi, has caused major soybean losses for growers in the Southeast U.S. The most effective disease management tool for growers is the use of stem canker resistant soy...
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Abstract Southern soybean stem canker, caused by Diaporthe aspalathi, has caused major soybean losses for growers in the Southeast U.S. The most effective disease management tool for growers is the use of stem canker resistant soybean varieties. A fast, reliable greenhouse assay for stem canker would facilitate identification of resistance in soybean germplasm. An existing toothpick assay was modified to include culturing D.?aspalathi on oxgall agar on toothpicks autoclaved in oxgall liquid medium. Three week-old seedlings were inoculated with toothpicks inserted in the stem between the cotyledon and the first trifoliate leaf. Inoculation sites were sealed with petroleum jelly, and seedlings were incubated in humidity chambers for 72?h. Stem canker disease was highly consistent on susceptible lines four weeks post-inoculation and was not observed on soybean lines with known Rdm genes. High levels of disease (≥98.3%) were observed with cultivars Braxton, Davis, and Centennial previously reported to have resistance in field studies. Isolates of D.?aspalathi were observed to differ in virulence. This modified greenhouse assay will assist in the efforts for breeding stem canker resistance and better understanding the differences in disease phenotypes for some cultivars. Highlights ? Modified toothpick assay resulted in high incidence of stem canker in the greenhouse. ? Soybean with known resistance genes did not develop disease. ? Isolates of Diaporthe aspalathi were observed to differ in virulence.
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