scholarly journals Two Receptor-Like Genes, Vfa1 and Vfa2, Confer Resistance to the Fungal Pathogen Venturia inaequalis Inciting Apple Scab Disease

2008 ◽  
Vol 21 (4) ◽  
pp. 448-458 ◽  
Author(s):  
Mickael Malnoy ◽  
Mingliang Xu ◽  
Ewa Borejsza-Wysocka ◽  
Schuyler S. Korban ◽  
Herb S. Aldwinckle
Keyword(s):  
Fungal Pathogen ◽  
Southern Blotting ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Microscopic Analysis ◽  
Chain Reaction ◽  
Resistance Response ◽  
Malus Floribunda ◽  
Apple Cultivars ◽  
Polymerase Chain

The Vf locus, originating from the crabapple species Malus floribunda 821, confers resistance to five races of the fungal pathogen Venturia inaequalis, the causal agent of apple scab disease. Previously, a cluster of four receptor-like genes, Vfa1, Vfa2, Vfa3, and Vfa4, was identified within the Vf locus. Because the amino-acid sequence of Vfa3 is truncated, it was deemed nonfunctional. In this study, each of the three full-length Vfa genes was introduced into a plant cloning vector, pCAMBIA2301, and used for Agrobacterium-mediated transformation of two apple cultivars, Galaxy and McIntosh, to assess functionality of these genes and to characterize their roles in resistance to V. inaequalis. Transformed apple lines carrying each of Vfa1, Vfa2, or Vfa4 were developed, analyzed for the presence of the transgene using polymerase chain reaction and Southern blotting, and assayed for resistance to apple scab following inoculation with V. inaequalis. Transformed lines expressing Vfa4 were found to be susceptible to apple scab, whereas those expressing either Vfa1 or Vfa2 exhibited partial resistance to apple scab. Based on Western blot analysis as well as microscopic analysis of plant resistance reactions, the roles of Vfa1 and Vfa2 in apple scab disease resistance response are discussed.

scholarly journals Apple Autotetraploids with Enhanced Resistance to Apple Scab (Venturia inaequalis) Due to Genome Duplication-Phenotypic and Genetic Evaluation

2021 ◽  
Vol 22 (2) ◽  
pp. 527
Author(s):  
Małgorzata Podwyszyńska ◽  
Monika Markiewicz ◽  
Agata Broniarek-Niemiec ◽  
Bożena Matysiak ◽  
Agnieszka Marasek-Ciolakowska
Keyword(s):  
Venturia Inaequalis ◽  
Leaf Shape ◽  
Apple Scab ◽  
Early Period ◽  
Physiological Parameters ◽  
Aflp Analysis ◽  
Poor Growth ◽  
Enhanced Resistance ◽  
Apple Cultivars ◽  
Old Trees

Among the fungal diseases of apple trees, serious yield losses are due to an apple scab caused by Venturia inaequalis. Protection against this disease is based mainly on chemical treatments, which are currently very limited. Therefore, it is extremely important to introduce cultivars with reduced susceptibility to this pathogen. One of the important sources of variability for breeding is the process of polyploidization. Newly obtained polyploids may acquire new features, including increased resistance to diseases. In our earlier studies, numerous tetraploids have been obtained for several apple cultivars with ‘Free Redstar’ tetraploids manifesting enhanced resistance to apple scab. In the present study, tetraploids of ‘Free Redstar’ were assessed in terms of phenotype and genotype with particular emphasis on the genetic background of their increased resistance to apple scab. Compared to diploid plants, tetraploids (own-rooted plants) were characterized with poor growth, especially during first growing season. They had considerably shorter shoots, fewer branches, smaller stem diameter, and reshaped leaves. In contrast to own-rooted plants, in M9-grafted three-year old trees, no significant differences between diplo- and tetraploids were observed, either in morphological or physiological parameters, with the exceptions of the increased leaf thickness and chlorophyll content recorded in tetraploids. Significant differences between sibling tetraploid clones were recorded, particularly in leaf shape and some physiological parameters. The amplified fragment length polymorphism (AFLP) analysis confirmed genetic polymorphism of tetraploid clones. Methylation-sensitive amplification polymorphism (MSAP) analysis showed that the level of DNA methylation was twice as high in young tetraploid plants as in a diploid donor tree, which may explain the weaker vigour of neotetraploids in the early period of their growth in the juvenile phase. Molecular analysis showed that ‘Free Redstar’ cultivar and their tetraploids bear six Rvi genes (Rvi5, Rvi6, Rvi8, Rvi11, Rvi14 and Rvi17). Transcriptome analysis confirmed enhanced resistance to apple scab of ‘Free Redstar’ tetraploids since the expression levels of genes related to resistance were strongly enhanced in tetraploids compared to their diploid counterparts.

scholarly journals Quantification of Venturia inaequalis Growth in Malus × domestica with Quantitative Real-Time Polymerase Chain Reaction

Plant Disease ◽  
2012 ◽  
Vol 96 (12) ◽  
pp. 1791-1797 ◽  
Author(s):  
Michele Gusberti ◽  
Andrea Patocchi ◽  
Cesare Gessler ◽  
Giovanni A. L. Broggini
Keyword(s):  
Polymerase Chain Reaction ◽  
Real Time ◽  
Malus Domestica ◽  
Venturia Inaequalis ◽  
Simultaneous Detection ◽  
Scab Resistance ◽  
Infected Leaf ◽  
Chain Reaction ◽  
Limit Of Quantification ◽  
Polymerase Chain

A quantitative real-time polymerase chain reaction (qPCR) was developed and validated for quantification of Venturia inaequalis in infected leaf tissue of Malus × domestica. The method is based on dual-labeled hybridization probes, allowing simultaneous detection of host and pathogen DNA within one single reaction. Limit of quantification for the pathogen was 0.5 pg per reaction and, for the host, reached 5 pg per reaction. The fungal growth measured in four apple cultivars 2 weeks after inoculation significantly correlated with their different level of scab resistance and allowed the observation of ontogenic resistance. After sporulation on the youngest leaf, fungal biomass in susceptible ‘Gala’ was 118 times higher than in resistant ‘Florina’ and ‘Discovery’ while intermediate values were found with the intermediate susceptible ‘Milwa’. Correlation was also observed between severity classes obtained by visual scoring of symptoms and qPCR results. Moreover, qPCR demonstrated validity of the developed method as a disease severity forecast tool 10 days after the pathogen's inoculation and prior to the appearance of the symptoms. Applications of the methodology can include the quantification of scab resistance during breeding programs, evaluation of fungicide and biocontrol efficacy, and quantification of the fitness of different pathogenic strains.

Genetic transformation of Stella De Oro daylily by particle bombardment

2003 ◽  
Vol 83 (4) ◽  
pp. 873-876 ◽  
Author(s):  
A. N. Aziz ◽  
R. J. Sauvé ◽  
S. Zhou
Keyword(s):  
Southern Blotting ◽  
Basal Medium ◽  
Callus Cultures ◽  
Naphthaleneacetic Acid ◽  
Ms Medium ◽  
Chain Reaction ◽  
Polymerase Chain ◽  
Semi Solid ◽  
Independent Transformation

Daylily (Hemerocallis sp. ‘Stella de Oro’) callus cultures initiated from ovules were bombarded with gold particles coated with plasmid harboring Basta® resistance gene. Resulting putative transgenic calli were selected after 3 wk on semi-solid Murashige and Skoog’s (MS) basal medium supplemented with 10 mg L-1 1-naphthaleneacetic acid, 2 mg L-1 6-benzylaminopurine and 3 mg L-1 phosphinothricin (PPT). Surviving calli regenerated shoots after 2 mo on semi-solid MS medium supplemented with 2 mg L-1 thiadiazuron and 1 mg L-1 PPT. Polymerase chain reaction and Southern blotting were used to confirm independent transformation events. Key words: Basta® resistance, in vitro, Hemerocallis

scholarly journals A Two-Phase Resistance Response of Venturia inaequalis Populations to the QoI Fungicides Kresoxim-Methyl and Trifloxystrobin

Plant Disease ◽  
2004 ◽  
Vol 88 (5) ◽  
pp. 537-544 ◽  
Author(s):  
Wolfram Köller ◽  
D. M. Parker ◽  
W. W. Turechek ◽  
Cruz Avila-Adame ◽  
Keith Cronshaw
Keyword(s):  
Cytochrome B ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Target Site ◽  
Site Mutation ◽  
Two Phase ◽  
Resistance Response ◽  
Population Responses ◽  
North Germany ◽  
Qoi Resistance

The class of fungicides acting as respiration inhibitors by binding to the Qo center of cyto-chrome b (QoIs) are in wide use for the management of apple scab caused by Venturia inaequalis. In order to assess responses of V. inaequalis populations to treatments with QoIs, sensitivities of isolates were determined for germinating conidia or for mycelial colonies developing from germinating conidia. Under both test conditions, inhibitory potencies of kresoxim-methyl and trifloxystrobin were largely equivalent. V. inaequalis populations treated with QoIs in a commercial and an experimental orchard both responded with significant shifts toward declining QoI sensitivities. However, the population responses were quantitative in nature, and highly resistant isolates indicative of a cytochrome b target site mutation were not detected. V. inaequalis populations from both orchards investigated also were fully resistant to sterol de-methylation-inhibiting fungicides (DMIs) such as fenarimol and myclobutanil, but isolate sensitivities to QoIs and DMIs were largely unrelated. Performance tests with kresoxim-methyl and trifloxystrobin at the experimental orchard diagnosed as DMI-resistant revealed that the quantitative shift toward declining QoI sensitivities did not constitute the status of practical QoI resistance. In contrast to these quantitative responses, emergence of qualitative QoI resistance was documented for V. inaequalis in an orchard in North Germany, which had been treated intensively with a total of 25 QoI applications over four consecutive seasons. Isolates retrieved from the orchard were highly resistant to both kresoxim-methyl and trifloxystrobin and were characterized as G143A cytochrome b mutants. The results indicated that the paths of QoI resistance can be both quantitative and qualitative in nature. A similar phenomenon has not been described before. Circumstantial evidence suggests that the quantitative phase of V. inaequalis population responses to QoIs might be succeeded by a quantitative selection of highly resistant G143A target-site mutants.

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