In Florida, almost all citrus trees are infected with Huanglongbing (HLB), caused by the gram-negative, intracellular phloem limited bacteria Candidatus liberibacter asiaticus (CLas). Distinguishing between the severely and mildly sick trees is important for managing the groves and testing new HLB therapies. A mildly sick tree is one that produces higher fruit yield, compared to a severely sick tree, but measuring yields is laborious and time consuming. Here we characterized HLB affected sweet orange trees in the field in order to identify the specific traits that are correlated with the yields. We found that canopy volume, fruit detachment force (FDF) and the percentage of photosynthetically active radiation interception in the canopy (%INT) were positively correlated with fruit yields. Specifically, %INT measurements accurately distinguished between mild and severe trees in independent field trials. We could not find a difference in the Ct value between high and low producing HLB trees. Moreover, Ct values did not always agree with the number of CLas in the phloem that were visualized by transmission electron microscopy. Overall, our work identified an efficient way to distinguish between severe and mild HLB trees in Florida by measuring %INT and suggests that health of the canopy is more important for yields than the Ct value.

中文翻译：

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受黄龙病影响的甜橙树的冠层健康与果实产量相关，但与 Candidatus Liberibacter asiaticus Ct 值无关

在佛罗里达州，几乎所有柑橘树都感染了黄龙病（HLB），由革兰氏阴性、细胞内韧皮部限制性细菌Candidatus 引起亚洲自由杆菌（CLas）。区分严重和轻度患病的树木对于管理树林和测试新的 HLB 疗法很重要。与重病树相比，轻度病树的果实产量更高，但测量产量既费力又费时。在这里，我们表征了田间受 HLB 影响的甜橙树，以确定与产量相关的特定性状。我们发现冠层体积、果实脱离力 (FDF) 和冠层中光合有效辐射拦截的百分比 (%INT) 与果实产量呈正相关。具体来说，在独立的田间试验中，%INT 测量准确地区分了轻度和重度树木。我们找不到高产和低产 HLB 树之间 Ct 值的差异。此外，Ct 值并不总是与通过透射电子显微镜观察到的韧皮部中 CLas 的数量一致。总体而言，我们的工作确定了一种通过测量 %INT 来区分佛罗里达州重度和轻度 HLB 树木的有效方法，并表明冠层的健康对产量比 Ct 值更重要。