Tomato pith necrosis caused by Pseudomonas corrugata and other Pseudomonas species is a common disease occurring worldwide, including Saudi Arabia. We demonstrated how the pith necrosis length induced by P. corrugata strain KSU-RT3 significantly increased (>31%) when it was co-inoculated along with P. fluorescens strain KSU-AT1. The latter exhibited antagonistic activity against P. corrugata in vitro and revealed its ability to induce pith necrosis symptoms on tomato when inoculated individually. The two bacterial strains could grow in the presence of NaCl concentrations of up to 80 mM. The growth of the two bacterial strains was suppressed under acidic conditions (pH 4–5). In vivo, the pith necrosis length was significantly increased by 16.15% under irrigation with saline water. A short exposure of 14 days to high salinity (in the absence of pathogens) was sufficient to render the tomato plants significantly more susceptible to subsequent inoculation with either of the two pathogens or when inoculated in combination. In conclusion, our study showed that acid soil and saline soil watered with fresh water showed decreased infection, only neutral to alkaline soil (up to pH 8) and saline soil watered with saline water showed increased infection. So an important cultural measure could be to keep soil pH reasonably low. More antagonistic P. fluorescens strains should be tested for pathogenicity before large-scale application to avoid the risk of introducing strains, such as our P. fluorescens strain KSU-AT1 that proved to be pathogenic to tomato plants.

中文翻译：

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盐和碱土胁迫接种皱纹假单胞菌和/或荧光假单胞菌后，对番茄髓坏死的敏感性和严重性增强

皱纹假单胞菌和其他假单胞菌引起的番茄髓坏死是全世界普遍发生的疾病，包括沙特阿拉伯。我们证明了与皱纹假单胞菌菌株KSU-AT1一起接种时，皱纹假单胞菌菌株KSU-RT3诱导的髓坏死长度显着增加（> 31％）。后者表现出对皱纹波霉的拮抗活性。体外研究发现，单独接种可诱导番茄上的髓坏死症状。两种细菌菌株可以在浓度高达80 mM的NaCl存在下生长。在酸性条件下（pH 4-5），两个细菌菌株的生长受到抑制。在体内，用盐水冲洗时，髓坏死长度显着增加了16.15％。在高盐度下短时间暴露14天（在没有病原体的情况下）足以使番茄植株明显更易于随后接种两种病原体或组合接种。总之，我们的研究表明，用淡水浇灌的酸性土壤和盐渍土壤显示出减少的感染，仅中性至碱性土壤（pH值高达8）和用盐水浇灌的盐渍土壤感染增加。因此，一项重要的文化措施可能是保持土壤pH值合理较低。更具对抗性荧光假单胞菌菌株应在大规模应用前进行致病性测试，以避免引入菌株的风险，例如我们的荧光假单胞菌菌株KSU-AT1被证明对番茄植物具有致病性。