Background

Aphids are important pests of plants that utilize their mouthparts, which are modified into stylets, to remove phloem sap from the sieve elements. As part of their feeding process, aphids deposit saliva into the plant tissue. While some salivary components elicit plant defenses, others manipulate host physiology to benefit the insect, including suppressing plant defenses (Nalam et al., 2018). Plants utilize a variety of defenses to control aphid infestation. These include antibiosis, which adversely impacts aphid growth, development and fecundity, and antixenosis, which affects insect behavior, including feeding behavior. These defenses are exerted at various steps, including at the cell surface, during the intercellular penetration of leaf tissue by the insect stylet, when the stylet tip is inside plant cells, and when the stylet tip is in the sieve elements (Nalam et al., 2018). The green peach aphid (GPA), Myzus persicae Sülzer, is an important pest of plants in numerous families, including the Brassicaceae, Solanaceae, Cucurbitaceae, Rosaceae, Asteraceae, Malvaceae, Amaranthaceae (Blackman and Eastop, 2000). In addition, the GPA transmits several viral diseases (Kennedy et al., 1963; Matthews, 1991). During the last decade, the interaction between Arabidopsis thaliana, which belongs to the Brassicaceae family, and the GPA has been increasingly utilized to study plant-aphid interaction (Louis et al., 2012; Louis and Shah, 2013). This pathosystem has facilitated understanding of the physiological and molecular processes that determine the outcome of plant-aphid interaction, including plant defense mechanisms and their impact on insect population growth, fecundity and behavior (Louis et al. 2012; Louis and Shah, 2013).

The direct current (DC)-electrical penetration graph (EPG) system, which measures the electromotive force (EMF) signal and fluctuations in electrical resistance resulting from aphid stylet penetrations, provides a sensitive method to monitor aphid feeding behavior on plants (Tjallingii, 1985; Salvador-Recatalà and Tjallingii, 2015). When the aphid stylet is inserted intercellularly, the voltage is positive and when inserted intracellularly, the voltage is negative (Tjallingii, 2006). The different EPG waveform patterns are indicative of the different activities in which the insect is engaged. Moreover, the duration of each type of waveform provides a quantitative measure of the effect of plant genotype and/or treatment on insect feeding behavior, including the time spent by the insect feeding from the sieve elements. However, despite the success of the Arabidopsis-GPA pathosystem, the protocols utilized to study aphid population growth, fecundity and feeding behavior have not been described in detail. Here, we detail the protocols for rearing a Brassicaceae-adapted colony of the GPA, no-choice assays for monitoring GPA population growth, fecundity assays to monitor insect reproductive rate, and the EPG analysis to monitor GPA feeding behavior on Arabidopsis.