Canopy health, but not Candidatus Liberibacter asiaticus Ct values, are correlated with fruit yield in Huanglongbing affected sweet orange trees.

Abstract

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.

Plant phenotyping relevance

HLB罹病樹の健康状態・重症度を、樹冠の光合成有効放射の遮断率（%INT）で判別する方法を提示し、独立圃場試験で精度を確認しているため、単なるルーチン測定を超えた表現型測定の検証研究である。

Code and data availability

The supplied blocks contain no data availability, code availability, or supplementary-material statements. The paper's phenotype measurements (yield, %INT, FDF, canopy volume, Ct values, TEM counts) are reported only in tables/figures within the article itself, with no public deposit or authors' URL for datasets, code,

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