Huanglongbing (HLB), the most important citrus disease worldwide, is associated with bacteria transmitted by the Asian citrus psyllid (ACP) preferably through new shoots present in the canopy. In a commercial citrus plant, the vegetative growth of the scion is influenced by the rootstock variety in which it is grafted. Although all commercial citrus varieties planted in recent years are susceptible to HLB, the dynamics of the rootstock in grafted plant could influence the progress of HLB, whether at the plant or grove scale. In this work, HLB incidence in ‘Valencia’ sweet orange grafted onto 16 rootstocks and its relationship to the tree canopy volume and flushing dynamics were evaluated in a field trial under ACP control. The experiment was conducted under rainfed conditions in Bebedouro, state of Sao Paulo, Brazil, from 2011 to 2019. ‘Flying Dragon’ trifoliate orange known for its dwarfing characteristics was used as the rootstock. A reduction in canopy volume by 77% at 8 years of age were observed compared to the most vigorous rootstocks. The frequency of flush shoots of ‘Valencia’ sweet orange was not influenced by the rootstock, but the abundance of flush shoots was lower on three semi-dwarfing rootstocks and as well as ‘Flying Dragon’. Although HLB incidence on ‘Flying Dragon’ was lower than on ‘Rangpur’ lime and other three semi-standard rootstocks (trees with canopy volume between 51 and 75% of the ‘Rangpur’ lime canopy volume), all other combinations had similar HLB disease progress regardless of the canopy volume and flushing dynamics. Moreover, under field conditions, variations on the cumulative HLB incidence greater than 26% were necessary to significantly separate rootstocks. Therefore, the results suggest that true dwarfing rootstocks have potential to integrate the management program for HLB and that mechanisms in addition to tree vigor appear to be involved in the host–vector relationship.

中文翻译：

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'瓦伦西亚'甜橙嫁接16根砧木黄龙病发生率、冠层体积及发芽动态

黄龙病 (HLB) 是世界上最重要的柑橘病害，与亚洲柑橘木虱 (ACP) 传播的细菌有关，最好通过冠层中的新芽传播。在商业柑橘植物中，接穗的营养生长受其嫁接的砧木品种的影响。尽管近年来种植的所有商业柑橘品种都对 HLB 敏感，但嫁接植物中砧木的动态可能会影响 HLB 的进展，无论是在植物还是树林规模。在这项工作中，在 ACP 控制下的田间试验中，评估了嫁接到 16 个砧木上的“瓦伦西亚”甜橙的 HLB 发生率及其与树冠体积和潮红动态的关系。该试验于 2011 年至 2019 年在巴西圣保罗州贝贝杜罗的雨育条件下进行。以矮化特性着称的'飞龙'三叶橙被用作砧木。与最旺盛的砧木相比，8 岁时树冠体积减少了 77%。'Valencia'甜橙的红芽频率不受砧木的影响，但三个半矮化砧木和'飞龙'的红芽丰度较低。尽管'飞龙'的HLB发病率低于'Rangpur'石灰和其他三种半标准砧木（树冠体积在'Rangpur'石灰树冠体积的51%到75%之间），但所有其他组合都具有相似的HLB病害无论树冠体积和冲洗动态如何，都会取得进展。此外，在田间条件下，大于 26% 的累积 HLB 发生率的变化对于显着分离砧木是必要的。因此，结果表明真正的矮化砧木具有整合 HLB 管理程序的潜力，并且除了树势之外的机制似乎还涉及宿主 - 媒介关系。