Para-aminobenzoic (PABA) is reported to induce resistance against a range of plant pathogens in different crops in a salicylic acid-dependent manner. However, factors affecting its efficacy are not well understood. Foliar PABA applications on tomato seedlings reduced lesion incidence caused by Pseudomonas syringae pv. tomato (Pst) in a dose-dependent manner in distal leaves up to 18 mM under controlled environment conditions, but only three out of six commercial processing tomato cultivars tested showed a response to PABA. Leaves in direct contact with 9 and 18 mM PABA of both PABA-responsive and PABA-nonresponsive cultivars showed phytotoxicity. In a PABA-responsive cultivar, one, two and three PABA applications were equally effective at reducing lesion incidence in distal leaves, but the duration of control only persisted for approximately 7 days. Although PABA application reduced lesion incidence in distal leaves, the Pst population in leaves was unaffected. Lesions on PABA-treated plants were larger than nontreated plants, and thus the proportion of leaf surface area with lesions was unaffected by PABA treatment. In in vitro assays, 18 and 72 mM PABA produced zones of inhibition against Pst 15 and 50% larger than the ethanol control, demonstrating direct antimicrobial effects of PABA. PABA application did not affect symptom development in a mixed infection of Pst or Xanthomonas spp. in one field experiment with a PABA-responsive cultivar. Further research is needed to understand why PABA was unsuccessful in the field before it is to be used as a practical disease management tool for foliar bacterial diseases of tomato.

据报道，对氨基苯甲酸 (PABA) 以水杨酸依赖性方式在不同作物中诱导对一系列植物病原体的抗性。然而，影响其疗效的因素尚不清楚。在番茄幼苗上叶面喷洒 PABA 减少了丁香假单胞菌引起的病斑发生率。番茄( Pst) 在受控环境条件下以剂量依赖性方式在远端叶中高达 18 mM，但测试的六个商业加工番茄品种中只有三个表现出对 PABA 的反应。与对 PABA 有反应和对 PABA 无反应的品种的 9 和 18 mM PABA 直接接触的叶子显示出植物毒性。在对 PABA 有反应的栽培品种中，施用 1、2 和 3 种 PABA 在降低远端叶片病斑发生率方面同样有效，但控制持续时间仅持续了大约 7 天。虽然 PABA 的应用降低了远端叶片的病害发生率，但Pst叶中的种群不受影响。PABA 处理的植物上的病斑比未处理的植物大，因此病斑的叶表面积比例不受 PABA 处理的影响。在体外试验中，18 和 72 mM PABA 对Pst的抑制区为15 和 50%，比乙醇对照大 50%，证明了 PABA 的直接抗菌作用。在Pst或黄单胞菌属的混合感染中，PABA 的应用不影响症状的发展。在一项对 PABA 有反应的品种的田间试验中。在将 PABA 用作番茄叶面细菌性病害的实用病害管理工具之前，需要进一步研究以了解为什么 PABA 在该领域不成功。