Assessment of Inoculation Methods of <i>Thielaviopsis paradoxa</i> (De Seynes) Höhn into Oil Palm Seedlings under Greenhouse Conditions
2021
Sandra Gaitán-Chaparro | Edwin Navia-Rodríguez | Hernán Mauricio Romero
Oil palm (<i>Elaeis guineensis</i> Jacq. and <i>Elaeis Oleifera</i> Cortes) is one of the most important oil crops in the world. Colombia is the fourth-largest oil palm producer worldwide. However, oil palm diseases are a significant factor affecting yield. <i>Thielaviopsis paradoxa</i> (De Seynes) Höhn is a pathogen that affects young palm trees, causing spear rot. Four disease establishment methods were studied to replicate, in a controlled environment, the symptoms of the disease found in the field. Young palm trees were inoculated with a suspension of endoconidia using either local infiltration, drip, scissor cut, or direct contact with agar blocks bearing mycelia and conidia. The effects of the inoculation methods were studied in dose-method-disease severity experiments conducted in a greenhouse under controlled conditions. All four methods resulted in <i>T. paradoxa</i> infections and the development of symptoms of the disease. The disease severity was correlated with the method and dose of inoculation. In trials to test Koch’s postulates, <i>T. paradoxa</i> was isolated from areas of disease progression in the inoculated trees, but the teleomorph <i>Ceratocystis paradoxa</i> (Dade) Moreau was not observed. A photographic record of the infection process at different times post-infection was compiled. Given that establishing the disease through artificial inoculation is essential for assessing plant pathogenesis, this study determined that the local infiltration method (1 × 10<sup>6</sup> endoconidia mL<sup>−1</sup>) and a 3–7 day incubation period were critical for the development of symptoms as severe as those observed in natural infections in the field.
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