Studies on cherry leaf spot at Dresden- Pillnitz Mirko Schuster Institute for Breeding Research on Fruit Crops
Cherry breeding Disease resistance Cherry leaf spot (Blumeriella jaapii) Leaf spot on sweet cherry Leaf spot on sour cherry
Leaf spot fungus, Blumeriella jaapii - Life cycle Pathogen: - Ascomycet, Blumeriella jaapii (Rehm) Arx (syn. Coccomyces hiemalis Higgins) Vegetative cycle (conidia) April Sept. H I C J A A - Myceli between mesophyll cells B Acervulus at the lower site of a leaf C - Macro-conidia Generative cycle (ascospores) April-June B D Premature apothecia G F F - Micro-conidiophore and trichogyne G - Trichogyne with micro-conidia H - Apothecia containing asci Nach Jakobsen at al., 1986) D I - Asci J - Ascospores
Objectives: Development of a artificial leaf spot test Description of rating scales Evaluation of cherry genotypes and cherry wild species resistant to leaf spot Studies about the inheritance of leaf spot resistance Use of resistant donors in cherry breeding
Leaf spot fungus, Blumeriella jaapii - Isolation Infected cherry leaf Acervuli with conidia (Hochapfel, 1952) Acervuli with conidia on the lower leaf surface
Leaf spot fungus, Blumeriella jaapii Isolation/Propagation Leaf spot fungus-isolates on potato dextrose agar Mycelia of B. jaapii
Leaf spot fungus Propagation / 1 st inoculation test Propagation of the fungus / conidia Inoculation method
Results of the 1 st inoculation test = Successful infection, but low infection rate on the leaves Use of conidia suspension from naturally infected leaves
Germination test of conidia - Dry stored infected leaves Conidia germinated after 3, 5, 7, 11 months and more
Inoculation test Inoculation suspension Collection of infected leaves in the orchard Drying of the leaves at room temperature Storage of the dry leaves in an exsiccator
Inoculation test Inoculation suspension Leaving of the dry infected leaves in a wet chamber for one day
Inoculation test Inoculation suspension Collection of the conidia from the lower surface of leaf
Inoculation test Inoculation suspension Counting of the concentration of conidia and diluting of the inoculation suspension
Inoculation test Preparation of Petri dishes for inoculation test
Inoculation test Inoculation Leaving of the leaves in the Petri dishes Moistening of the leaves with water Inoculation of the leaves with the suspension
Inoculation test Evaluation Evaluation of the reaction to leaf spot after 10-12 days susceptible resistant genotypes
Inoculation test Test material Leaf spot infection on old leaves of sour cherry cv. Schattenmorelle
Inoculation test Test material Seedling 82 ( Almaz x o.p.) 1. leaf 2. leaf 3. leaf 4. leaf x 1,0 x 1,0 x 1,0 x 1,0 x 2,5 x 2,5 x 2,5 x 2,5 x 4,0 x 4,0 x 4,0 x 4,0 3. or 4. leaf for the inoculation test
Inoculation test Evaluation Clone 'DK1,7,3' Clone 'DK1,7,13' Resistant and susceptible genotypes
Inoculation test Evaluation sheet + scale
Inoculation test Rating scale Reaction type 1 no symptoms, green leaf 2 chlorotic or necrotic points or small pigmented lesions 3 larger lesions, partly with aerial mycelium and stunted sporulating lesions 4 2 to 10 sporulating lesions, acervuli 5 11 or more sporulating lesions, acervuli (modified after Wharton et al. 2003)
Cherry leaf spot Field evaluation F2 seedling populations: F2 population: 'Namati' x clone 18,167 'Sunburst' Prunus canescens clone 3,105 (P. cerasus x P. maackii) x 'Fanal' clone 3,106 (P. cerasus x P. maackii) x 'Fanal' 'Schattenmorelle' x clone 3,105 'Schattenmorelle' x clone 3,106 'Schattenmorelle' 'Gerema' 'Ujfehertoi fürtös' 'Coralin'
Cherry leaf spot Rating scale Evaluation (two rating scales): Reaction type scale 1 5 Distribution of infection scale 1 9 Reaction type on the leaf (R-type): 1 - no symptoms, green leaf 2 - chlorotic or necrotic points 3 - larger lesions, partly with aeial mycelium and stunted sporulating acervuli 4 - sporulating acervuli with chlorotic and necrotic lesions 5 - heavily sporulating acervuli Distribution of infection on the tree (R-distribution): 1 - no symptoms, green leaf 3 - chlorotic or necrotic points, scattered infected leaves 5 - infected leaves >50 % of the tree 7 - infected leaves, 50 % of the tree defoliated 9 - heavily sporulating acervuli on all leaves, >90 % of the tree defoliated
Cherry leaf spot Rating scale (R-distribution) Distribution of infection on the tree (R-distribution): 1 no symptoms, green leaf, no leaves drop down 3 chlorotic or necrotic points, scattered infected leaves, first leaves drop down 5 infected leaves 30-50 % of the tree 7 infected leaves, 50 % of the tree defoliated 9 heavily sporulating acervuli on all leaves, >90 % of the tree defoliated
Cherry leaf spot Rating scale Evaluation (rating scale): Reaction type scale 1 5 Distribution of infection scale 1 9 Reaction type on the leaf (R-type): 1 - no symptoms, green leaf 2 - chlorotic or necrotic points 3 - larger lesions, partly with aeial mycelium and stunted sporulating acervuli 4 - sporulating acervuli with chlorotic and necrotic lesions 5 - heavily sporulating acervuli Distribution of infection on the tree (R-distribution): 1 - no symptoms, green leaf 3 - chlorotic or necrotic points, scattered infected leaves 5 - infected leaves 30-50 % of the tree 7 - infected leaves, 50 % of the tree defoliated 9 - heavily sporulating acervuli on all leaves, >90 % of the tree defoliated Resistant (R) R-type 1-3 / R-distribution 1-5 Susceptible (S) R-type 4-5 / R-distribution 6-9
Problem? - Hypersensitive resistance reaction type Hypersensitive reaction / defoliation DK1,5,45 (clone 3,105 x Fanal) LS r-type - 2N! LS r-distrib. - 7
Evaluation of cherry genotypes and Prunus species as to resistance to cherry leaf spot Prunus species R-type P. serrulata 1 P. maackii 1 P. canescens 1 P. kurilensis 1 P. nipponica 1 P. insisa 1 P. subhirtella 1 P. sargentii 1 P. dawyckensis 4 Sour cherry R-type Almaz* 0 Ciganus 59 2 Csengödi 2 Hartai 1 Karneol 1 Korai Pipacsmeggy 1 Köröser Gierstädt 2 Morina 2 Paljus 2 Wishnja* 1 *interspecific hybrid Sweet cherry R-type Krupnoplodnaja 4 Lapins 3 Namati 4 Napoleon 3 Naprumi 4 Sunburst 4 Vinka 4 40 sour cherry - susceptible
Inheritance of cherry leaf spot resistance P. canescens Segregation analysis of leaf spot resistance 2008-2010: Combination resistant susceptible total χ 2 P % Namati' x clone '18,167' 41 39* 80* 0,05 90-70 * 7 susceptible seedlings dead from 2008-2010 1 : 1 Segregation: resistant : susceptible 1 : 1 (41 : 39) one dominant resistance gene Detection of a QTL on LG 4 for leaf spot resistance from P. canescens (Cooperation with MSU East Lansing, A. Iezzoni) Travis Stegmeir, Mirko Schuster, Audrey Sebolt, Umesh Rosyara, George W. Sundin and Amy Iezzoni Cherry Leaf Spot Resistance in Cherry (Prunus) is Associated with a Quantitative Trait Locus on Linkage Group 4 Inherited from P. canescens. Molecular Breeding (in process)
Inheritance of cherry leaf spot resistance P. maackii Segregation analysis of leaf spot resistance 2009-2010: Cross combination resistant susceptible total χ 2 1 : 1 P % clone 3,105 x Fanal 35 31 66 0,24 70-50 clone 3,106 x Fanal 39 52 91 1,86 30-10 Schattenmorelle x clone 3,105 24 18 42 0,86 50-30 Schattenmorelle x clone 3,106 18 31 49 3,45 10-5 Segregation: resistant : susceptible 1 : 1 one dominant resistance gene
Use of resistant donors in cherry breeding Diploid (2x): P. canescens F1 x P. avium F2 x P.avium F3 x P. avium Tetraploid (4x): P. maackii P. padus P. serotiona P. spinosa F1 x P. cerasus F2 x P. cerasus F3 x P. cerasus
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Cherry leaf spot fungus, Blumeriella jaapii - symptoms At first on the upper surface of leaves small, circular, purple spots appear which eventually turn brown Infected leaves turn yellow, the area around lesions may remain green During wet weather, white to light pink spore masses appear on the lower surface in the centre of the spots Serious defoliation of trees can cause uneven ripening and poor fruit quality The tree vigour and winter-hardiness of the flower buds and the wood is reduced
Inoculation test Evaluation scale DK1,7,5 scale 1 no symptoms, green leaf Korall scale 1-2 chlorotic or necrotic points, small pigmented lesions DK1,7,16 scale 3 larger lesions, partly with aerial mycelium and stunted sporulating lesions DK1,7,10 DK1,7,13 scale 5 11 or more sporulating lesions