Genetic resistance is the main strategy to control Fusarium wilt in common bean. Despite this, few studies have focused on defense mechanisms involved in bean resistance to Fusarium oxysporum f. sp. phaseoli (Fop). Thus, the present study aimed to investigate the changes in xylem morphology and involvement of phenylpropanoid compounds and their biosynthetic enzymes in bean resistance against Fop. Uirapuru and UFSC-01 genotypes characterized, respectively, as susceptible and resistant were used. In roots and hypocotyls, guaiacol peroxidase (GPX), phenylalanine ammonia-lyase (PAL), and polyphenol oxidase (PPO) activities were determined at 0, 1, 2, 3, 4, 5, and 6 days after inoculation (dai), and flavonoids, total phenolics, and lignin content were quantified at 0, 3, and 6 dai. Cross sections of taproots and hypocotyls were examined under epifluorescence (at 1, 3, and 6 dai) and transmission electron (at 6 dai) microscopic to analyze the morphology of xylem cell walls. Overall, there was an increase in the activity of all studied enzymes in resistant bean plants, mainly during advanced colonization stages. Modifications in xylem morphology were more intense in roots of resistant genotype resulting in an increase of occluded cells, organelles, and cell wall strengthening. This study provides evidence that bean resistance is associated with increased phenylpropanoid enzymatic activity and cell wall reinforcement of some xylem cells.

遗传抗性是防治菜豆枯萎病的主要策略。尽管如此，很少有研究关注豆类对尖孢镰刀菌的抗性所涉及的防御机制。sp。菜豆（Fop）。因此，本研究旨在研究木质部形态的变化以及苯丙素类化合物及其生物合成酶在豆类抗Fop中的作用。. 使用分别表征为易感和抗性的 Uirapuru 和 UFSC-01 基因型。在接种后 0、1、2、3、4、5 和 6 天（dai）测定根和下胚轴中的愈创木酚过氧化物酶 (GPX)、苯丙氨酸解氨酶 (PAL) 和多酚氧化酶 (PPO) 活性，黄酮类化合物、总酚类物质和木质素含量分别在 0、3 和 6 天进行量化。在落射荧光（在 1、3 和 6 dai）和透射电子（在 6 dai）显微镜下检查主根和下胚轴的横截面，以分析木质部细胞壁的形态。总体而言，抗性豆类植物中所有研究的酶的活性都有所增加，主要是在晚期定殖阶段。在抗性基因型的根中，木质部形态的改变更加强烈，导致闭塞细胞的增加，细胞器和细胞壁强化。这项研究提供的证据表明，豆类抗性与增加的苯丙素酶活性和一些木质部细胞的细胞壁强化有关。