Infection Process and Host Defense Responses in Compatible and Incompatible Interactions between Cowpea (Vigna unguiculata) andColletotrichum gloeosporioides

The infection process ofColletotrichum gloeosporioideswas examined by light microscopy on two cowpea genotypes, BR 3 Tracuateua and TE 97‐411. In the susceptible genotype BR 3 Tracuateua, the pathogen acted as an intracellular hemibiotroph. Invasion of cowpea primary leaves occurred preferentially t...

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Bibliographic Details
Published in:International journal of plant sciences 2007-02, Vol.168 (2), p.193-203
Main Authors: Barreto, A. L. H., Vasconcelos, I. M., Grangeiro, T. B., Melo, V. M. M., Matos, T. E., Eloy, Y. R. G., Fernandes, C. F., Torres, D. C., Freire‐Filho, F. R., Freire, F. C. O., Oliveira, J. T. A.
Format: Article
Language:English
Subjects:
Appressoria
Colletotrichum
Epidermal cells
Fungi
Genotypes
Infections
Inoculation
Leaves
Lesions
Papillae
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Summary:The infection process ofColletotrichum gloeosporioideswas examined by light microscopy on two cowpea genotypes, BR 3 Tracuateua and TE 97‐411. In the susceptible genotype BR 3 Tracuateua, the pathogen acted as an intracellular hemibiotroph. Invasion of cowpea primary leaves occurred preferentially through the leaf epidermal cells by penetration tubes that emerged from appressoria. The penetration tube swelled within 48 h to form a spherical infection vesicle inside the epidermal cell in a biotrophic interaction. Subsequently, it became multilobed and multiseptated. By 4 d after inoculation, one or more large primary hyphae emerged from the lateral lobes and grew intracellularly and further colonized several adjacent epidermal host cells, characterizing the necrotrophic phase of infection. Primary leaves of the resistant cowpea genotype, TE 97‐411, showed enhanced penetration resistance toC. gloeosporioidesassociated with higher epidermal H2O2accumulation beneath appressoria and primary germ tubes, papilla formation, and increased phenylalanine ammonia‐lyase activity, possibly related to accumulation of phenolic compounds and host cell wall lignification. Macroscopic examination of the primary leaves revealed the presence of shrunken necrotic lesions characteristic of anthracnose in infected BR 3 Tracuateua, whereas in the genotype TE 97‐411, cell death was also observed but only in a reduced percentage of the infection sites. In summary, the results obtained in this study suggested that TE 97‐411 is the resistant genotype toC. gloeosporioidescompared with BR 3 Tracuateua because it developed more effective defense responses against the establishment of the pathogen.
ISSN:1058-5893
1537-5315
DOI:10.1086/509608