Figure 3.

EPG showing representative waveform patterns produced when cowpea aphid apterae feed on susceptible accession Borung (A) or on resistant accession SA30199 (B). The horizontal axes represent a 1-h time period; the vertical axes represent voltage. Histological studies of plant-aphid interactions have correlated stylet positions in plant tissues with specific EPG waveforms [47]. “Non-penetration” indicates stylets are outside the plant. “Pathway” indicates mostly intramural probing activities between mesophyll or parenchyma cells. “Sieve element phase,” consisting primarily of sap ingestion with short periods of salivation into sieve elements, was frequently seen with plants of Borung and only rarely seen with plants of SA30199. Sharp, downward spikes, named potential drops, indicate cell puncture events by stylets, each lasting approximately 5 s. The percentage of time aphids spent in various activities on Borung or SA30199 during 9h exposure to the host plants is shown in C. Each value represents the mean and SE of 16 biological replicates. Means for the cultivars labeled with * are significantly different (P < 0.01)