Pear and apple cultivars widely grown in Tunisia were tested for their susceptibility to Erwinia amylovora (Burrill). Based on a preliminary evaluation of 11 cultivars, three were classified as susceptible, six as moderately susceptible, and two as the least susceptible to E. amylovora. Investigation of physiological and molecular mechanisms modulating the host response in two pear cultivars with different susceptibility degree indicated that early positive regulation of SOD gene, together with a reduced CAT activity, leads to higher H₂O₂ burst, which was more sustained in the least susceptible cultivar. After inoculation, the genes involved in the salicylic acid (SA) pathway and coding for PR1 protein, PAL, ICS1, and ICS2 were repressed in both cultivars, much more so in the susceptible one. In addition, their expression levels were significantly higher in the least susceptible cultivar before inoculation, which suggested that triggering of the SA pathway is important for promoting the tolerance to E. amylovora. The genes coding for ANS, CHI, CHS, and FHT were repressed after inoculation, except that the degree of that repression was more prominent in the susceptible cultivar, which suggested that phenylpropanoid (PP) pathway could play a critical role in the tolerance of pear plants to E. amylovora. Furthermore, comparisons of the SA-related gene expression trends with that pursued by H₂O₂ indicated that higher SA and H₂O₂ accumulation together with PP metabolites are important factors of the tolerance of the cultivar ‘Ambri’. Finally, our results provide important insights for genetic improvement programs aiming to develop cultivars resistant to E. amylovora.

测试了在突尼斯广泛种植的梨和苹果品种对桃蚜欧文氏菌（Burrill）的敏感性。根据对11个品种的初步评估，将3个分类为易感，将6个分类为中度易感，将2个分类为对淀粉样小球藻最不敏感。对两个易感程度不同的梨品种调控寄主响应的生理和分子机制的研究表明，SOD基因的早期正向调节以及CAT活性的降低会导致更高的H ₂ O ₂爆发，至少在更短的时间内更持久易感品种 接种后，参与水杨酸（SA）途径并编码PR1蛋白PAL的基因， ICS1 ，并ICS2分别在这两个品种的压抑，更因此在易感之一。另外，它们的表达水平在接种前最不易感的品种中显着更高，这表明SA途径的触发对于提高对淀粉状肠球菌的耐受性是重要的。接种后，编码ANS，CHI，CHS和FHT的基因被抑制，除了这种抑制的程度在易感品种中更为突出，这表明苯丙烷（PP）途径可能在梨的耐性中起关键作用。植物到支链霉菌。此外，SA相关基因表达趋势与H ₂ O ₂追求的趋势比较表明较高的SA和H ₂ O ₂积累以及PP代谢产物是'Ambri'品种耐性的重要因素。最后，我们的研究结果为旨在开发抗淀粉样变性双歧杆菌的遗传改良计划提供了重要的见识。