Beeman Augustine Q, Njus Zach L, Pandey Santosh, Tylka Gregory L
First and fourth authors: Department of Plant Pathology and Microbiology, and second and third authors: Department of Electrical and Computer Engineering, Iowa State University, Ames 50011.
Phytopathology. 2016 Dec;106(12):1563-1571. doi: 10.1094/PHYTO-06-16-0224-R. Epub 2016 Sep 30.
Plant-parasitic nematodes cause substantial damage to agricultural crops worldwide. Long-term management of these pests requires novel strategies to reduce infection of host plants. Disruption of nematode chemotaxis to root systems has been proposed as a potential management approach, and novel assays are needed to test the chemotactic behavior of nematodes against a wide range of synthetic chemicals and root exudates. Two microfluidic chips were developed that measure the attraction or repulsion of nematodes to chemicals ("chemical chip") and young plant roots ("root chip"). The chip designs allowed for chemical concentration gradients to be maintained up to 24 h, the nematodes to remain physically separate from the chemical reservoirs, and for images of nematode populations to be captured using either a microscope or a flatbed scanner. In the experiments using the chemical chips, seven ionic solutions were tested on second-stage juveniles (J2s) of Meloidogyne incognita and Heterodera glycines. Results were consistent with previous reports of repellency of M. incognita to a majority of the ionic solutions, including NHNO, KNO, KCl, MgCl, and CaCl. H. glycines was found to be attracted to both NHNO and KNO, which has not been reported previously. A software program was written to aid in monitoring the location of nematodes at regular time intervals using the root chip. In experiments with the root chip, H. glycines J2s were attracted to roots of 3-day-old, susceptible (cultivar Williams 82) soybean seedlings, and attraction of H. glycines to susceptible soybean was similar across the length of the root. Attraction to resistant (cultivar Jack) soybean seedlings relative to the water only control was inconsistent across runs, and H. glycines J2s were not preferentially attracted to the roots of resistant or susceptible cultivars when both were placed on opposite sides of the same root chip. The chips developed allow for direct tests of plant-parasitic nematode chemotaxis to chemicals and roots with minimal human intervention.
植物寄生线虫对全球农作物造成了巨大损害。对这些害虫的长期管理需要新的策略来减少对寄主植物的感染。干扰线虫对根系的趋化性已被提议作为一种潜在的管理方法，并且需要新的测定方法来测试线虫对多种合成化学品和根系分泌物的趋化行为。开发了两种微流控芯片，一种用于测量线虫对化学品的吸引或排斥（“化学芯片”），另一种用于测量线虫对幼苗根系的吸引或排斥（“根系芯片”）。芯片设计能够使化学浓度梯度保持长达24小时，线虫与化学物质储存器保持物理隔离，并且可以使用显微镜或平板扫描仪捕获线虫群体的图像。在使用化学芯片的实验中，对南方根结线虫和大豆胞囊线虫的二龄幼虫测试了七种离子溶液。结果与之前关于南方根结线虫对包括硝酸铵、硝酸钾、氯化钾、氯化镁和氯化钙在内的大多数离子溶液具有排斥性的报道一致。发现大豆胞囊线虫对硝酸铵和硝酸钾均有吸引力，这在之前尚未有报道。编写了一个软件程序，以帮助使用根系芯片定期监测线虫的位置。在使用根系芯片的实验中，大豆胞囊线虫二龄幼虫被3日龄易感（品种Williams 82）大豆幼苗的根系所吸引，并且大豆胞囊线虫对易感大豆的吸引力在整个根系长度上相似。相对于仅用水作为对照，对抗性（品种Jack）大豆幼苗的吸引力在各次实验中并不一致，并且当抗性和易感品种的根系放置在同一根系芯片的相对两侧时，大豆胞囊线虫二龄幼虫不会优先被抗性或易感品种的根系所吸引。所开发的芯片能够在最少的人为干预下直接测试植物寄生线虫对化学品和根系分泌物的趋化性。
