Trichoderma species form endophytic associations within Theobroma cacao trichomes
Trichoderma species are usually considered soil organisms that colonize plant roots, sometimes forming a symbiotic relationship. Recent studies demonstrate that Trichoderma species are also capable of colonizing the above ground tissues of Theobroma cacao (cacao) in what has been characterized as an...
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Veröffentlicht in: | Mycological research 2009-12, Vol.113 (12), p.1365-1376 |
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Zusammenfassung: | Trichoderma species are usually considered soil organisms that colonize plant roots, sometimes forming a symbiotic relationship. Recent studies demonstrate that
Trichoderma species are also capable of colonizing the above ground tissues of
Theobroma cacao (cacao) in what has been characterized as an endophytic relationship.
Trichoderma species can be re-isolated from surface sterilized cacao stem tissue, including the bark and xylem, the apical meristem, and to a lesser degree from leaves. SEM analysis of cacao stems colonized by strains of four
Trichoderma species (
Trichoderma ovalisporum-DIS 70a,
Trichoderma hamatum-DIS 219b,
Trichoderma koningiopsis-DIS 172ai, or
Trichoderma harzianum-DIS 219f) showed a preference for surface colonization of glandular trichomes versus non-glandular trichomes. The
Trichoderma strains colonized the glandular trichome tips and formed swellings resembling appresoria. Hyphae were observed emerging from the glandular trichomes on surface sterilized stems from cacao seedlings that had been inoculated with each of the four
Trichoderma strains. Fungal hyphae were observed under the microscope emerging from the trichomes as soon as 6
h after their isolation from surface sterilized cacao seedling stems. Hyphae were also observed, in some cases, emerging from stalk cells opposite the trichome head. Repeated single trichome/hyphae isolations verified that the emerging hyphae were the
Trichoderma strains with which the cacao seedlings had been inoculated. Strains of four
Trichoderma species were able to enter glandular trichomes during the colonization of cacao stems where they survived surface sterilization and could be re-isolated. The penetration of cacao trichomes may provide the entry point for
Trichoderma species into the cacao stem allowing systemic colonization of this tissue. |
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ISSN: | 0953-7562 1469-8102 |
DOI: | 10.1016/j.mycres.2009.09.004 |