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A viability qPCR protocol to assess the efficacy of a heat treatment to sanitize carrot seeds from Candidatus Liberibacter solanacearum

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Abstract

Seeds may harbour plant pathogens and, therefore, may be regarded as a possible pathway for their dissemination along trade routes worldwide. Heat treatment appears to be a proper seed sanitation method to comply with the requirement of phytosanitary measures. Carrot seeds have been supposed as a pathway for the dissemination of Candidatus Liberibacter solanacearum, although vertical pathogen transmission is still under debate: nonetheless, such seeds may be conveniently heat treated as a sanitation method. We used a dry thermal treatment (50 ± 1 °C for 72 h) to sanitize seeds from Ca. Liberibacter solanacearum and, since this bacterium is not cultivable, we additionally implemented and evaluated a viability qPCR protocol able to detect only viable cells, therefore confirming seed sanitation. The population of the pathogen was estimated through a plasmid calibration curve. The infection of Ca. Liberibacter solanacearum was quantified in two positive samples at approx. 5 × 106 cells gram −1 of seed. Seed sample tested with monoazides (EMA and PMA) qPCR clearly indicated that seed-associated bacteria lost their viability during the heat treatment, thus confirming seed sanitation. Finally, such heat treatment did not affect seed viability and seed quality: conversely, a remarkable reduction of seed saprophytes was observed, together with a better vigour germination performance.

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  1. Department of Life Sciences, University of Modena and Reggio Emilia, via Amendola 2 – Pad. Besta, 42122, Reggio Emilia, Italy

    Soukaina Ben Othmen, Gianmarco Conti Nibali, Stefano Cassanelli, Davide Giovanardi & Emilio Stefani

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  1. Soukaina Ben Othmen
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  2. Gianmarco Conti Nibali
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Correspondence to Davide Giovanardi.

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Othmen, S.B., Nibali, G.C., Cassanelli, S. et al. A viability qPCR protocol to assess the efficacy of a heat treatment to sanitize carrot seeds from Candidatus Liberibacter solanacearum. Eur J Plant Pathol 166, 77–90 (2023). https://doi.org/10.1007/s10658-023-02646-7

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