Plant-parasitic nematodes are able to sense and respond to gradients of chemical signals. How pH and inorganic salts in the rhizosphere affect nematode accumulation and host-seeking is poorly understood. We investigate the response of different groups of plant-parasitic nematodes to pH and salt concentration gradients. Responses of infective juveniles (J2) of the economically important plant-parasitic nematodes, soybean cyst nematodes (SCN; Heterodera glycines) and root-knot nematodes (RKN; Meloidogyne incognita and M. hapla) to pH and salt gradients were assessed using Pluronic F-127 gel-based assays. Microelectrodes were utilized to measure pH and ion concentration gradients in the gel. Differences were found between the three nematode species in response to acid, base and salts. For SCN, maximum nematode accumulation was between pH range 4.98–5.46 in an acid gradient, while the preferred alkaline pH ranges were 8.40–8.78 and 9.52–9.99. The preferred Cl− concentration for SCN attraction was 171–256 mM. RKN showed weak attraction to base and salt at low J2 concentration but increasing attraction at a greater nematode concentration. The pH and inorganic salts affect nematode behavior, accumulation, and survival. These findings provide new considerations for strategies to manage plant-parasitic nematodes under field conditions.

中文翻译：

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大豆胞囊线虫（甘氨酸异种线虫）和根结线虫（根结线虫属）对 pH 和无机盐梯度的响应

植物寄生线虫能够感知和响应化学信号的梯度。根际中的 pH 值和无机盐如何影响线虫的积累和寻找寄主，我们知之甚少。我们调查了不同组的植物寄生线虫对 pH 值和盐浓度梯度的响应。使用 Pluronic F 评估经济上重要的植物寄生线虫、大豆胞囊线虫（SCN；甘氨酸异线虫）和根结线虫（RKN；南方根结线虫和 M. hapla）的感染性幼虫 (J2) 对 pH 和盐梯度的反应-127 基于凝胶的检测。微电极用于测量凝胶中的 pH 值和离子浓度梯度。发现三种线虫物种对酸、碱和盐的反应存在差异。对于 SCN，最大线虫积累在 pH 值范围 4.98-5 之间。46 在酸性梯度中，而优选的碱性 pH 范围是 8.40-8.78 和 9.52-9.99。SCN 吸引的首选 Cl- 浓度为 171-256 mM。RKN 在低 J2 浓度下对碱和盐的吸引力较弱，但在较高线虫浓度下吸引力增加。pH 值和无机盐会影响线虫的行为、积累和存活。这些发现为在田间条件下管理植物寄生线虫的策略提供了新的考虑。