FLAVANOLS AS DEFENCE BARRIERS IN APPLE LEAVES AGAINST THE APPLE SCAB FUNGUS (VENTURIA INAEQUALIS)

1998 ◽  
pp. 79-82 ◽  
Author(s):  
U. Mayr ◽  
D. Treutter
Plant Disease ◽  
2017 ◽  
Vol 101 (3) ◽  
pp. 414-420 ◽  
Author(s):  
Franziska M. Porsche ◽  
Barbara Pfeiffer ◽  
Andreas Kollar

Ascospores of Venturia inaequalis, released from pseudothecia in overwintered, infected apple leaves, serve as the primary inoculum for apple scab. In this study, we tested a new sanitation strategy to reduce ascospore inoculum under orchard conditions over three overwintering periods. After leaf fall, nutrient media containing different concentrations of degraded casein or a yeast extract from Saccharomyces cerivisiae were applied to leaf litter infected with apple scab. The application of 30 and 60% yeast extract showed the greatest efficacy, and significantly reduced ascospore discharge by 99% (P < 0.01) in 2013 and 2014. The efficacy of the treatments did not differ from treatment with 5% urea (P > 0.05). Leaf litter decay was accelerated in the plots treated with yeast extract compared with untreated control plots. Moreover, apple leaves treated with yeast extract had completely decayed due to earthworm activity before ascospore maturity. In comparison, up to 26% of the leaves in untreated control plots had not decayed. These results suggest that the treatment of leaf litter with yeast extract can almost completely eliminate apple scab inoculum in the course of the whole primary season. These sanitation practices may be beneficial for both organic and conventional cultivation. The reduced infection pressure may allow growers the usage of fungicides with lower efficacy or to reduce the number of applications needed to manage apple scab in spring.


2005 ◽  
Vol 77 (3) ◽  
pp. 129-134 ◽  
Author(s):  
J. Bernier ◽  
O. Carisse ◽  
T.C. Paulitz

Venturia inaequalis, the causal agent of apple scab, overwinters in apple (Malus pumila) leaves on the orchard floor by producing pseudothecia. The objectives of this survey were to make a collection of fungi to be subsequently tested for their potential as psychrophile biocontrol agents against V. inaequalis and to acquire knowledge on the diversity of the microflora of dead apple leaves. Fungi were recovered from dead apple leaves collected in the spring and fall of 1993. A total of 345 isolates from 49 genera were identified. Fifteen gene were not previously recorded as colonizers of apple leaves in North America.


1985 ◽  
Vol 31 (3) ◽  
pp. 251-255 ◽  
Author(s):  
Daniel Cullen ◽  
John H. Andrews

Resistance to the fungicide benomyl (BenR) was induced with N-methyl-N′-nitro-N-nitrosoguanidine in Chaetomium globosum isolated from apple leaves. The population densities of a resistant strain reintroduced to leaves on apple trees in an orchard were determined at 3 h, and 1 and 3 weeks following inoculation. Relative to wild-type parents, BenR populations declined more rapidly on orchard trees, but the rate of decline was reduced by amending initial inoculum with 18.5 ppm benomyl. Survival of BenRC. globosum increased 40–58% relative to BenRC. globosum applied without benomyl. In growth chamber experiments with potted apple seedlings, the BenR strain was as antagonistic as were the wild-type parents to the scab pathogen, Venturia inaequalis. The marked strain alone did not significantly reduce scab infection on saplings in the field; however, when it was applied with benomyl, scab severity was significantly (P = 0.01) less than with benomyl alone.


2013 ◽  
Vol 55 (1) ◽  
pp. 225-231
Author(s):  
Beata Meszka ◽  
Anna Bielenin

The effect of pre-leaf fall of 5% urea treatment on primary infection of apple by <i>Venturia inaequalis</i>, the cause of scab, was investigated in commercial apple orchards of McIntosh cv. in different regions of Poland, at Miłobądz, Sinołęka and Dąbrowice. Additionally, the development of pseudothecia and maturation of ascospores were evaluated in the spring on apple leaves of two cultivars (McIntosh and Gloster) treated with 5% solution of urea. Microscopic observations of leaves showed that urea treatment significantly reduced the number of pseudothecia (by ca. 90%) and ascospore production. Low number of ascospores after urea treatment has strongly affected primary infection of apple by the fungus in all tested orchards. Reduction of leaf infection on control trees was usually more than 30%. Also efficacy of chemical control of apple scab was significantly higher on plots treated with urea.


1961 ◽  
Vol 7 (4) ◽  
pp. 525-534 ◽  
Author(s):  
E. H. Barnes ◽  
E. B. Williams

A stimulating substance in apple leaves which enhances the growth of Venturia inaequalis (Cke.) Wint. was identified as phloridzin. The metabolism of this compound to phloretin, phloroglucinol, p-hydroxyphenyl propionic acid, p-hydrox-y benzoic acid, and protocatechuic acid is hypothesized on the presence of phloretin and phloroglucinol in the culture filtrates of V. inaequalis when it is grown in the presence of phloridzin. The only breakdown product which stimulated the parasite was p-hydroxyphenylpropionic acid and it is concluded that its utilization by V. inaequalis may be the basis for the stimulatory action of phloridzin.The effect of these compounds and m-inositol on the growth and sporulation of V. inaequalis was studied. All of the compounds induced resistant reactions in the 384-1 selection but not in the Geneva variety. This may represent a specificity of the host to the action of these chemicals, indicating that they are correlated with the specificity of the host to races of V. inaequalis. Preliminary studies on the effects of these compounds on the metabolism of the host indicated that new phenolic compounds are produced.


2009 ◽  
Vol 89 (4) ◽  
pp. 745-753 ◽  
Author(s):  
M Mikulic Petkovsek ◽  
F Stampar ◽  
R Veberic

Leaf samples were collected from apple varieties susceptible and resistant to apple scab [Venturia inaequalis (Cke.) Wint.] from June to September for 2 yr between 2005 and 2006. These were analyzed for phenolic compounds, using high-performance liquid chromatography (HPLC). In the apple leaves, the following hydroxycinnamic acids were detected: chlorogenic, caffeic and p-coumaric acids; the following dihydrochalcone: phloridzin, and the following flavonoids: epicatechin, catechin, rutin and quercitrin. The total of phenolic compounds in apple leaves was determined spectrophotometrically, using the Folin-Ciocalteu method. During the growing season, the content of phenolic compounds changed and was related to the physiological stage of the tissue and cultivar used. Each phenolic compound had its own curve of seasonal changes in concentration. In 2005 there was no significant change in total phenols during the growing season. In 2006, their content changed significantly during the growing season; statistically the highest content of total phenols was found in the leaves in August. Total phenols as well as single phenolics were statistically higher in resistant than in susceptible apple varieties for both years.Key words: Malus × domestica Borkh., leaves, phenolic compounds, seasonal changes, Venturia inaequalis (Cke.) Wint., resistance


2008 ◽  
Vol 61 ◽  
pp. 54-58
Author(s):  
P.N. Wood ◽  
R.M. Beresford ◽  
T.J. Taylor

In autumn 2006 apple leaves with visible scab (black spot) symptoms were collected at the time of leaf fall and dipped in fungicides at concentrations equivalent to field application rates The leaves were overwintered on gravel and ascospore production measured on three dates during the following spring using suction spore traps Of ten fungicides tested myclobutanil trifloxystrobin captan dodine tolyfluanid and cyprodinil either reduced or delayed ascospore production by Venturia inaequalis during the following spring compared with a waterdipped control Metiram dithianon urea and copper hydroxide had a minimal effect on ascospore production Leaves from a separate orchard trial produced significantly fewer ascospores after myclobutanil treatment than after captan treatment Captan and tolyfluanid are recommended for autumn application to control scab because they significantly reduced or delayed ascospore production and have a low risk of selecting resistant strains of V inaequalis Although also effective myclobutanil trifloxystrobin dodine and cyprodinil should not be used for autumn application because of the risk of fungicide resistance


Planta Medica ◽  
2007 ◽  
Vol 73 (09) ◽  
Author(s):  
JM Rollinger ◽  
R Spitaler ◽  
M Menz ◽  
P Schneider ◽  
EP Ellmerer ◽  
...  

2021 ◽  
Vol 22 (2) ◽  
pp. 527
Author(s):  
Małgorzata Podwyszyńska ◽  
Monika Markiewicz ◽  
Agata Broniarek-Niemiec ◽  
Bożena Matysiak ◽  
Agnieszka Marasek-Ciolakowska

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.


Sign in / Sign up

Export Citation Format

Share Document