Local infection associated with vascular bundles: the colonization of coconut palm leaflets by two <Emphasis Type="Italic">Camarotella</Emphasis> species |
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| Authors: | Kelly Lana Araújo Silvaldo Felipe da Silveira Vicente Mussi-Dias Juan Manuel Anda Rocabado Flavio Costa Miguens |
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| Institution: | 1.Laboratório de Entomologia e Fitopatologia, Centro de Ciências e Tecnologias Agropecuárias,Universidade Estadual do Norte Fluminense Darcy Ribeiro – UENF,Campos dos Goytacazes,Brazil;2.Laboratório de Biologia Celular e Tecidual, Centro de Biologia e Biociências,UENF,Rio de Janeiro,Brazil |
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| Abstract: | Two Camarotella (Phyllachoraceae) species, C. torrendiella and C. acrocomiae are the causative agents of small (SV) and large verrucosis (LV), respectively, which are important diseases affecting Brazilian coconut palms. The small verrucosis produces necrotic lesions in coconut palm leaflets, whereas LV just produces chlorosis. Semi-thin sections of asymptomatic leaflets and of leaves presenting stromata in different development stages were compared through light microscopy in order to characterize the colonization process of these two coconut palm verrucosis agents. Camarotella torrendiella initially colonized the adaxial epidermal cells and the cells underlying the epidermis close to the vascular bundles. In latter colonization stages, the hyphae of C. torrendiella remained limited to the underlying necrotic tissue adjacent to the mature stromata, mostly in the intracellular spaces and in the collapsing cells of necrotized tissues around the vascular bundles. This species does not colonize intracellular intact fiber cells, xylem vessels or phloem sieve tube elements. In contrast, C. acrocomiae presented a typical biotrophic parasitism model such as that of some gramineous Phyllachora spp. High densities of C. acrocomiae hyphae were found inside intact sieve tube elements; however, with no evidence of cellular death. The extensive hyphal colonization by C. acrocomiae within sieve tube elements was also observed in tertiary and quaternary bundles, as well as in anastomosing vascular bundles. The dependence of both species on the colonization sites associated with vascular bundles indicates the need for additional studies about these intricate host-pathogen relationships. These studies could be important to define new strategies to control coconut palm verrucosis diseases. |
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