PHYSIOLOGICAL RACES OF VENTURIA INAEQUALIS

1957 ◽  
Vol 37 (2) ◽  
pp. 102-107 ◽  
Author(s):  
J. B. Julien ◽  
L. P. S. Spangelo
Keyword(s):  
Venturia Inaequalis ◽  
Physiological Races ◽  
Apple Leaves

Cultures of Venturia inaequalis were isolated from infected apple leaves and fruits received from various parts of Canada. The isolates differed in their ability to produce spores and to a certain extent in their growth. Variations were observed among monoconidial isolates obtained from a tissue isolate. Monoconidial cultures from an isolate varied in the shape, size, and colour of their colonies and in their pathogenicity to different varieties and seedlings. It would appear, therefore, that distinct physiological races of this fungus occurred among isolates tested.

scholarly journals Treatment of overwintering apple leaves to reduce primary inoculum of apple black spot

2003 ◽  
Vol 56 ◽  
pp. 95-99
Author(s):  
K. Tshomo ◽  
I.J. Horner ◽  
M. Walter ◽  
A. Stewart ◽  
M.V. Jaspers
Keyword(s):  
Venturia Inaequalis ◽  
Black Spot ◽  
Field Trials ◽  
Water Control ◽  
Primary Inoculum ◽  
Apple Leaves ◽  
Fungal Isolates ◽  
Glass Slides ◽  
Ascospore Production ◽  
Nutrient Amendments

Field trials were conducted in Hawkes Bay and Lincoln into methods of treating overwintering apple leaves to reduce ascospore production by the apple black spot pathogen Venturia inaequalis The leaf treatments comprised three levels of nutrient amendments (including a water control) and five levels of saprophytic fungal isolates (including a nofungus control) in a factorial design Leaves were left to overwinter on the orchard floor and in spring the V inaequalis ascospores released were trapped on glass slides and counted Ascospore numbers were reduced (Plt;005) by the leaf amendment urea which alone caused 73 reduction but not by the BioStarttrade; product The effect of fungal isolates was not significant (P012) although when combined with the water treatment the isolates Chaetomium Phoma and Epicoccum spp and Trametes versicolor reduced numbers of ascospores by 33 27 15 and 28 respectively compared to the nofungus control When combined with urea the Chaetomium isolate reduced ascospore numbers by 92 and 82 compared to the nil fungus/water control treatments in Hawkes Bay and Lincoln respectively indicating that this treatment has potential for reducing primary inoculum of apple black spot

scholarly journals A New Phytosanitary Method to Reduce the Ascospore Potential of Venturia inaequalis

Plant Disease ◽  
2017 ◽  
Vol 101 (3) ◽  
pp. 414-420 ◽  
Author(s):  
Franziska M. Porsche ◽  
Barbara Pfeiffer ◽  
Andreas Kollar
Keyword(s):  
Leaf Litter ◽  
Yeast Extract ◽  
Untreated Control ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Nutrient Media ◽  
Apple Leaves ◽  
Litter Decay ◽  
Ascospore Discharge ◽  
Infection Pressure

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.

scholarly journals Baseline Sensitivities of Venturia inaequalis Populations to the Strobilurin Fungicide Kresoxim-methyl

Plant Disease ◽  
1999 ◽  
Vol 83 (3) ◽  
pp. 274-278 ◽  
Author(s):  
Gilberto Olaya ◽  
Wolfram Köller
Keyword(s):  
Venturia Inaequalis ◽  
Resistance Development ◽  
Additional Tool ◽  
Apple Leaves ◽  
Scab Control ◽  
In Vivo Tests ◽  
Strobilurin Fungicide ◽  
The Mean

The efficacies of the new strobilurin fungicide kresoxim-methyl for the protection of apple leaves from infection by baseline populations of Venturia inaequalis were uniform across five major apple growing regions in North America. The mean ED50 value determined for 25 populations was 0.35 μg ml-1, with values ranging from 0.11 μg ml-1 to 0.75 μg ml-1. The mean level of scab control achieved at the kresoxim-methyl dose of 4 μg ml-1 was 93%. For one of the five orchards sampled in each region, kresoxim-methyl sensitivities of germinating conidia were determined. Sensitivities of 250 isolates were broadly distributed, with ED50 values ranging from 0.003 μg ml-1 to 0.14 μg ml-1 and a mean of 0.02 μg ml-1. This broad range of in vitro sensitivities was not reflected for the in vivo efficacy of kresoxim-methyl in the protection of apple leaves from scab infections. The discrepancy between in vivo and in vitro sensitivities implies that in vivo tests are more useful for the monitoring of kresoxim-methyl sensitivities of orchard populations. Because it can be expected that only isolates resistant under both test conditions will be prone to future selection, such isolates will contribute to increased frequencies of the least sensitive isolates described in this baseline study. Testing of in vitro isolate sensitivities will, therefore, provide an additional tool in the monitoring of kresoxim-methyl resistance development.

scholarly journals Autumnapplied urea and other compounds to suppress Venturia inaequalis ascospore production

2000 ◽  
Vol 53 ◽  
pp. 387-392
Author(s):  
R.M Beresford ◽  
I.J. Horner ◽  
P.N. Wood
Keyword(s):  
Venturia Inaequalis ◽  
Black Spot ◽  
Leaf Fall ◽  
Single Application ◽  
Apple Trees ◽  
Spot Disease ◽  
Apple Leaves ◽  
Cupric Hydroxide ◽  
Fallen Leaves ◽  
Ascospore Production

The effect of urea applied to apple leaves in autumn on production of ascospores of Venturia inaequalis (black spot) was quantified in four studies Autumn urea at concentrations from 020 reduced ascospore production in spring in proportion to the log of the urea concentration A single application of 5 urea sprayed onto fallen leaves gave an 88 decrease in ascospore production Urea applied to apple trees before leaf fall significantly reduced black spot disease on leaves the following spring in cv Fuji but not in cv Royal Gala Ascospore production was reduced by the fungicide cupric hydroxide but was not affected by a low concentration of fish fertilizer Three methods of ascospore assessment were used to detect differences in ascospore production

scholarly journals Fungal communities isolated from dead apple leaves from orchards in Quebec

2005 ◽  
Vol 77 (3) ◽  
pp. 129-134 ◽  
Author(s):  
J. Bernier ◽  
O. Carisse ◽  
T.C. Paulitz
Keyword(s):  
North America ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Causal Agent ◽  
Biocontrol Agents ◽  
Fungal Communities ◽  
Malus Pumila ◽  
Apple Leaves

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.

ASSESSMENT OF INTRODUCED APPLE VARIETIES BY SCAB AFFECTION (VENTURIA INAEQUALIS (COOKE) G. WINTER)

2021 ◽  
Vol 66 (1) ◽  
pp. 66-72
Author(s):  
O. E. Merezhko ◽  
M. A. Tikhonova ◽  
A. I. Lokhova
Keyword(s):  
Control Parameter ◽  
Apple Tree ◽  
Venturia Inaequalis ◽  
Weather Conditions ◽  
Orenburg Region ◽  
Apple Varieties ◽  
Apple Leaves ◽  
Control Variant ◽  
Horticultural Research ◽  
Great Damage

The article presents data on the identifying of apple varieties resistant to scab for their further use in breeding. The research was carried out on the basis of the Orenburg branch of the Federal Horticultural Research Center for Breeding, Agrotechnology and Nursery from 2010 to 2020 in the orchard established in 2004. The objects of research were introduced apple varieties and local hybrids. Scab (the causative agent is the marsupial mushroom Venturia inaequalis (Cooke) G. Winter) causes great damage to the apple tree. This disease affects the fruits and leaves, while dramatically reducing the apple productivity and marketability. According to the results of the studies, the greatest development of scab was observed in 2011, 2013 and 2016. In dry years (2010, 2012, 2014, 2015, 2017-2020 years) scab lesions were not observed. We have identified apple introduced varieties, which over the years of observation had a weak scab lesion and few spots on the apple leaves. In the control variant, in summer varieties in 2011, the scab on the leaves of the Serebryanoe kopytse variety was 0.9 points, all other studied varieties had a lower parameter. In autumn varieties, the varieties Sverdlovchanin and Gornist had the lowest parameter — 0.3-0.4 points, respectively, with a control parameter of 0.8 points (Prizemlennoye variety); in winter varieties, all the studied samples were lower than the control variant — 0.9 points. Weather conditions 2013 and 2016 also showed apple varieties less susceptible to scab in the conditions of the Orenburg region. As a result, we identified apple varieties that are weakly affected by scab: summer varieties — Letneye polosatoye, Mechtatel’nitsa, Solntsedar, Chudnoye; autumn varieties — resident of Sverdlovsk, Hornist; winter — Anis Sverdlovsky, Krasa Sverdlovsk, Persian. The obtained data can be used in breeding to create new apple varieties resistant to scab in the conditions of the Orenburg region.

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