Identification and pathogenicity of Alternaria species causing leaf blotch and fruit spot of apple in California

In late summer 2020, symptoms of leaf blotch and fruit spot were observed in two different commercial apple orchards (cultivars ‘Pink Lady’ and ‘Modi’) in San Joaquin County, California, USA. Ninety Alternaria isolates were obtained from symptomatic leaves and fruits collected from the orchards. Bas...

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Bibliographic Details
Published inPhytopathologia mediterranea Vol. 62; no. 3; pp. 467 - 479
Main Authors ELFAR, Karina, BUSTAMANTE, Marcelo I., ARREGUIN, Molly, NOURI, Mohamed T., ESKALEN, Akif
Format Journal Article
LanguageEnglish
Published Florence Firenze University Press 30.12.2023
Firenze University Press Università degli Studi di Firenze
Subjects
Allergens
Apple
Apples
Ascomycota
Calmodulin
Causes of
Conidia
Cultivars
Disease
Diseases and pests
Epidemics
Fruits
Fungal diseases of plants
Fungi
Fungi, Phytopathogenic
Gene loci
Genetic aspects
Identification
Identification and classification
Leaf blotch
Leafspot
Leaves
Morphology
Nucleotides
Orchards
Pathogenicity
Pathogens
Phylogenetics
Phylogeny
Physical characteristics
Sporulation
Spot blotch
United States
California
Australia
United States > US
San Joaquin County California
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Summary:In late summer 2020, symptoms of leaf blotch and fruit spot were observed in two different commercial apple orchards (cultivars ‘Pink Lady’ and ‘Modi’) in San Joaquin County, California, USA. Ninety Alternaria isolates were obtained from symptomatic leaves and fruits collected from the orchards. Based on morphological characteristics of the colonies, sporulation patterns, and conidia, the isolates were preliminarily separated into three morphogroups, tentatively identified as A. alternata, A. tenuissima and A. arborescens. Multi-locus phylogenetic analyses, using nucleotide sequences of plasma membrane ATPase, calmodulin, and Alternaria major allergen genes, showed that the isolates initially identified as A. tenuissima clustered with strains of A. alternata, following the current taxonomical arrangement of the genus. Pathogenicity tests on detached wounded apple leaves and fruits, using representative isolates of the three morphogroups, fulfilled Koch’s postulates. This is the first report of A. alternata and A. arborescens as causal agents of leaf blotch and fruit spot of apple in California.
ISSN:0031-9465
1593-2095
DOI:10.36253/phyto-14559