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{
    "pk": 41301,
    "title": "Candidatus Liberibacter asiaticus causes damage to citrus fibrous roots before visual decline of Huanglongbing-infected citrus trees",
    "subtitle": null,
    "abstract": "Huanglongbing (HLB), associated with \nCandidatus\n Liberibacter asiaticus (\nLas\n), was first detected in Florida in late 2005 and is now widely distributed throughout the commercial citrus-growing regions. In recent seasons, concurrent with freeze and drought episodes, symptomatic HLB-infected trees were much more affected by the extremes of temperature and moisture than trees without HLB. Symptoms exhibited by the stressed trees were excessive leaf loss and premature fruit drop even when HLB-infected trees were managed with good nutritional and irrigation practices recommended to support health of HLB-affected trees. This stress intolerance may be due to a loss of fibrous roots. To assess root status of HLB-infected trees on Swingle citrumelo rootstock (\nCitrus paradisi\n × \nPoncirus trifoliata\n), blocks of 2,307 three-yr-old Hamlin orange trees and 2,693 four-yr-old Valencia orange trees were surveyed visually and with a real time polymerase chain reaction (PCR) assay to determine \nLas\n infection status. The incidence of \nLas\n-infected trees (pre-symptomatic: \nLas\n+, visually negative, and symptomatic: \nLas\n+, visually positive) trees was 89% for the Hamlin block and 88% for the Valencia block. \nLas\n+ trees had 30 and 37% lower fibrous root mass density for pre-symptomatic and symptomatic trees, respectively, compared to \nLas\n- trees. In a second survey, 10- to 25-yr-old Valencia trees on ‘Swingle’ citrumelo or ‘Carrizo’ citrange (\nC. sinensis\n (L.) × \nP. trifoliata\n) rootstock were sampled within 3-6 months after identification of visual HLB status as symptomatic (\nLas\n+, visually positive) or non-symptomatic (\nLas\n-, visually negative) in orchards located in the central ridge, south-central and southwest flatwoods. Pairs of HLB symptomatic and non-symptomatic trees were evaluated for PCR status, fibrous root mass density and \nPhytophthora nicotianae\n progagules in the rhizosphere soil. \nLas\n+ trees had 27-40% lower fibrous root mass density and in one location higher \nP. nicotianae\n per root but Phytophthora populations per cm3 soil were high on both \nLas\n+ and \nLas\n- trees.  Fibrous root loss from HLB damage interacted with \nP. nicotianae\n depending on orchard location and time of year.",
    "language": "en",
    "license": {
        "name": "Creative Commons Attribution 4.0",
        "short_name": "CC BY 4.0",
        "text": "Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.\n\nNo additional restrictions — You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.",
        "url": "https://creativecommons.org/licenses/by/4.0"
    },
    "keywords": [],
    "section": "Abstracts of Presentations at the 3rd International Research Conference on Huanglongbing",
    "is_remote": true,
    "remote_url": "https://escholarship.org/uc/item/5jn2v2hd",
    "frozenauthors": [
        {
            "first_name": "J.",
            "middle_name": "H.",
            "last_name": "Graham",
            "name_suffix": "",
            "institution": "Univ. Florida, CREC, Lake Alfred, FL, USA",
            "department": "None"
        },
        {
            "first_name": "E.",
            "middle_name": "G.",
            "last_name": "Johnson",
            "name_suffix": "",
            "institution": "Univ. Florida, CREC, Lake Alfred, FL, USA",
            "department": "None"
        },
        {
            "first_name": "T.",
            "middle_name": "R.",
            "last_name": "Gottwald",
            "name_suffix": "",
            "institution": "USDA-ARS, Fort Pierce, FL, USA",
            "department": "None"
        },
        {
            "first_name": "M.",
            "middle_name": "S.",
            "last_name": "Irey",
            "name_suffix": "",
            "institution": "US Sugar Corp., Clewiston FL, USA",
            "department": "None"
        }
    ],
    "date_submitted": "2014-12-17T14:26:42-05:00",
    "date_accepted": "2014-12-17T14:26:42-05:00",
    "date_published": "2013-12-31T19:00:00-05:00",
    "render_galley": null,
    "galleys": [
        {
            "label": "",
            "type": "pdf",
            "path": "https://journalpub.escholarship.org/iocv_journalcitruspathology/article/41301/galley/30900/download/"
        }
    ]
}