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Istituto Agronomico Mediterraneo di Bari (IAMB) 2012

Evaluation of sampling methods for assessing Citrus tristeza virus incidence in Apulian citrus groves

Al Naasan, Yaseen

Titre : Evaluation of sampling methods for assessing Citrus tristeza virus incidence in Apulian citrus groves

Auteur : Al Naasan, Yaseen

Etablissement de soutenance : Istituto Agronomico Mediterraneo di Bari (IAMB)

Grade : Master of Science : Integrated pest management of Mediterranean fruit crops 2012

Résumé
In Apulia region, large-scale monitoring of Citrus tristeza closterovirus (CTV) is regulated by a Regional Decree, which has introduced the Hierarchical Sampling method scheme by Gottwald and Hughes (HS) with some modifications (MAIB-S) relating to the use of DTBIA individual testing instead of ELISA grouped testing. The use of an efficient sampling method is important for the estimation of the pathogen incidence, presence and distribution patterns ; therefore, HS and MAIB-S were evaluated with the simple random sampling method (SRS). Advanced spatial and statistics analyses were used : automatic tree extraction, Moran’s I, Ripley’s K-function, Rcitrus and a MATLAB-based simulation (CTVSimula). In the surveyed groves CTV incidence ranged from 0.46% to 16.21%, when testing 100% of the trees by DTBIA. By simulating the different sampling methods the infection rate was underestimated by HS, more accurate with MAIB-S, but the optimum was achieved by random sampling. Noticeable reduction in estimation accuracy for CTV incidence was observed with HS (0.1% to 65%). MAIB-S can be improved following a different systematic sampling scheme. According to three spatial aggregation indices, CTV spatial patterns proved to be remarkably aggregated in nearly 60% of the groves.

Mots-clés : APULIA ; CITRUS ; CITRUS TRISTEZA VIRUS ; STATISTICAL ANALYSIS ; STATISTICAL METHODS

Présentation (IAMB Library)

Page publiée le 12 mars 2018, mise à jour le 6 septembre 2018