Table_1_Inducibility of Plant Secondary Metabolites in the Stem Predicts Genetic Variation in Resistance Against a Key Insect Herbivore in Maritime Pine.docx

Resistance to herbivores and pathogens is considered a key plant trait with strong adaptive value in trees, usually involving high concentrations of a diverse array of plant secondary metabolites (PSM). Intraspecific genetic variation and plasticity of PSM are widely known. However, their ecology and evolution are unclear, and even the implication of PSM as traits that provide direct effective resistance against herbivores is currently questioned. We used control and methyl jasmonate (MJ) induced clonal copies of genotypes within families from ten populations of the main distribution range of maritime pine to exhaustively characterize the constitutive and induced profile and concentration of PSM in the stem phloem, and to measure insect herbivory damage as a proxy of resistance. Then, we explored whether genetic variation in resistance to herbivory may be predicted by the constitutive concentration of PSM, and the role of its inducibility to predict the increase in resistance once the plant is induced. We found large and structured genetic variation among populations but not between families within populations in resistance to herbivory. The MJ-induction treatment strongly increased resistance to the weevil in the species, and the genetic variation in the inducibility of resistance was significantly structured among populations, with greater inducibility in the Atlantic populations. Genetic variation in resistance was largely explained by the multivariate concentration and profile of PSM at the genotypic level, rather than by bivariate correlations with individual PSM, after accounting for genetic relatedness among genotypes. While the constitutive concentration of the PSM blend did not show a clear pattern of resistance to herbivory, specific changes in the chemical profile and the increase in concentration of the PSM blend after MJ induction were related to increased resistance. To date, this is the first example of a comprehensive and rigorous approach in which inducibility of PSM in trees and its implication in resistance was analyzed excluding spurious associations due to genetic relatedness, often overlooked in intraspecific studies. Here we provide evidences that multivariate analyses of PSM, rather than bivariate correlations, provide more realistic information about the potentially causal relationships between PSM and resistance to herbivory in pine trees.

抗食草动物和病原体能力被视为树木的关键性状，具有强大的适应性价值，通常涉及多种植物次生代谢物（PSM）的高浓度积累。PSM在种内遗传变异和可塑性方面广为人知。然而，其生态学和进化机制尚不明确，甚至PSM作为提供直接有效抗食草动物抵抗力的性状的意义也受到质疑。本研究利用来自马尾松主要分布区十个种群中家族内基因型的甲基茉莉酸（MJ）诱导克隆副本，全面表征了构成型和诱导型PSM在茎韧皮部的浓度和轮廓，并测量了昆虫食草损伤作为抵抗力的指标。随后，我们探讨了食草动物抗性中的遗传变异是否可以通过PSM的构成浓度进行预测，以及其诱导性在植物被诱导后预测抗性增加的作用。我们发现，在食草动物抗性方面，种群之间存在显著且结构化的遗传变异，而种群内家族之间则不存在。MJ诱导处理显著增强了物种对象鼻虫的抵抗力，而在种群间，抗性诱导性的遗传变异呈现出显著的结构化，大西洋种群表现出更高的诱导性。在考虑了基因型之间的遗传关系后，抗性遗传变异主要可由PSM在基因型水平的多元浓度和轮廓解释，而非与单个PSM的双变量相关性。尽管PSM混合物的构成浓度没有显示出对食草动物抵抗力的明显模式，但PSM混合物化学轮廓的特定变化以及MJ诱导后浓度的增加与抵抗力的增强相关。迄今为止，这是首次排除由于遗传关系导致的错误关联，这在种内研究中往往被忽视，对树木中PSM的诱导性及其在抗性中的作用进行了全面和严谨的分析。本研究提供了证据，表明PSM的多元分析，而非双变量相关性，为松树中PSM与食草动物抵抗力之间潜在因果关系的现实信息提供了更真实的见解。