Britt-Ugartemendia Kellee, Turner Donielle, Sieburth Peggy, Batuman Ozgur, Levy Amit
Department of Plant Pathology, Southwest Florida Research and Education Center, University of Florida, Immokalee, FL, United States.
Department of Plant Pathology, Citrus Research and Education Center, University of Florida, Lake Alfred, FL, United States.
Front Plant Sci. 2022 Dec 7;13:1050650. doi: 10.3389/fpls.2022.1050650. eCollection 2022.
The citrus industry of Florida faces insurmountable challenges against the destructive diseases citrus tristeza and Huanglongbing (HLB, or citrus greening). Though the tristeza causal agent, citrus tristeza virus (CTV), has been in Florida decades longer than HLB, growers have concentrated most of their efforts on combating the more detrimental HLB. The Asian citrus psyllid (; ACP) is the insect vector of the bacterial pathogen Liberibacter asiaticus and transmits the incurable HLB to all commercial citrus. During our searches for biological and viral controls against the ACP, we consistently detected sequences of CTV in Florida field populations of ACP. This unexpected finding led us to investigate whether ACPs collected from young shoots could be used as a tool to survey CTV in Florida citrus groves. We first surveyed for the most common CTV strains in Florida (T30, T36, and VT/T68) in citrus trees on mostly sour orange () rootstock, the rootstock susceptible to CTV decline. Out of 968 trees sampled across five years (2018-2022), approximately 8.2% were positive for CTV, with more than half of the CTV-positive trees infected with strain T30. Simultaneously, we looked at CTV strains in ACPs during this time and found that approximately 88% of pooled adult and nymph ACPs also had CTV, with over half the positive samples having the T36 strain. As a result of the much higher CTV incidences in the ACPs, we conducted a second investigation into whether we could more easily detect the same CTV strains in ACP nymphs as in CTV-infected citrus tissue. After individually sampling 43 trees and pooling the nymphs from each tree, we detected CTV at about the same incidence in the citrus tissue and the nymphs, but with much less ACP tissue, time, and resources required for detection compared to citrus tissue. Results from this study illustrate the sustained threat of CTV to Florida citrus and demonstrate the ACP as a potential bioindicator for CTV.
佛罗里达州的柑橘产业在应对毁灭性病害柑橘衰退病和黄龙病（HLB，即柑橘绿变病）方面面临着难以克服的挑战。尽管柑橘衰退病的病原体柑橘衰退病毒（CTV）在佛罗里达州存在的时间比HLB长几十年，但种植者大多将精力集中在对抗危害更大的HLB上。亚洲柑橘木虱（ACP）是细菌性病原体亚洲韧皮杆菌的昆虫传播媒介，会将无法治愈的HLB传播给所有商业柑橘品种。在我们寻找针对ACP的生物和病毒防治方法的过程中，我们在佛罗里达州田间的ACP种群中持续检测到CTV序列。这一意外发现促使我们研究从嫩梢上采集的ACP是否可以作为一种工具来调查佛罗里达州柑橘园中的CTV。我们首先在主要以酸橙为砧木（酸橙砧木易受CTV衰退病影响）的柑橘树上调查了佛罗里达州最常见的CTV株系（T30、T36和VT/T68）。在2018年至2022年的五年间对968棵树进行采样，约8.2%的树CTV呈阳性，超过一半的CTV阳性树感染的是T30株系。与此同时，我们在此期间观察了ACP中的CTV株系，发现约88%的成年和若虫ACP混合样本也携带CTV，超过一半的阳性样本携带T36株系。由于ACP中CTV的发生率要高得多，我们进行了第二项调查，探究是否能像在感染CTV的柑橘组织中一样，更容易在ACP若虫中检测到相同的CTV株系。在分别对43棵树进行采样并将每棵树的若虫汇集在一起后，我们在柑橘组织和若虫中检测到CTV的发生率大致相同，但与柑橘组织相比，检测所需的ACP组织、时间和资源要少得多。这项研究的结果说明了CTV对佛罗里达州柑橘的持续威胁，并证明了ACP作为CTV潜在生物指示物的作用。
