Cytology of infection of apple leaves by Diplocarpon mali

Diplocarpon mali, the causal agent of Marssonina leaf blotch of apple, causes severe defoliation during the growing season. Little information is available on the mode of infection and the infection process. In this study, the infection strategies of D. mali in apple leaves were investigated using f...

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Bibliographic Details
Published in:European journal of plant pathology 2013-05, Vol.136 (1), p.41-49
Main Authors: Zhao, Hua, Han, Qingmei, Wang, Jie, Gao, Xiaoning, Xiao, Chang-Lin, Liu, Jing, Huang, Lili
Format: Article
Language:English
Subjects:
Agriculture
Apples
appressoria
Biomedical and Life Sciences
conidia
Cytology
Defoliation
Diplocarpon
Ecology
electron microscopy
fluorescence
Fruits
germ tube
Growing season
leaf blotch
Leaves
Life Sciences
Malus
Marssonina
pathogens
Plant diseases
Plant Pathology
Plant Sciences
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Summary:Diplocarpon mali, the causal agent of Marssonina leaf blotch of apple, causes severe defoliation during the growing season. Little information is available on the mode of infection and the infection process. In this study, the infection strategies of D. mali in apple leaves were investigated using fluorescence and electron microscopy. Conidia attached to leaf surface apparently by mucilage and germinated on both sides of leaves 6 h post-inoculation (hpi). The pathogen penetrated the cuticle by infection pegs formed either in germ tubes or appressoria in 6 hpi, and then formed haustoria in host epidermal and mesophyll cells accompanied by extension of subcuticular and intercellular hyphae. Five days post-inoculation (dpi), the intracellular hyphae were observed. At the same time, the subcuticular hyphal strands (SHS) were produced as a means for fast expansion and reproduction. About 7 dpi, acervuli formed on inoculated leaves. This was the first observation that D. mali formed haustoria and SHS as infection strategies. Our results suggest that D. mali may behave like a hemibiotroph, which can use both biotrophic and necrotrophic strategies to establish infections on apple leaves.
ISSN:0929-1873
1573-8469
DOI:10.1007/s10658-012-0129-8