Probing behavior of the corn leafhopper Dalbulus maidis on susceptible and resistant maize hybrids

The corn leafhopper Dalbulus maidis is the main vector of the pathogens that cause corn stunt, a major disease of maize in the Americas. In line with plant resistance being an efficient tool to control diseases, the findings of a previous work showed that some corn hybrids are resistant to D. maidis. In this work, we assessed the probing behavior of D. maidis on susceptible and resistant corn hybrids using EPG (Electrical Penetration Graph) technology. Feeding of fifteen-day-old, non-inoculative females was recorded for 20 hours, with access to hybrids DK390, DK670, DK79-10, and DK72-10. Compared to the susceptible hybrid DK670, the other hybrids shifted D. maidis probing behavior in a way consistent with plant resistance to insects. This shift consisted of a higher number of probes of short duration, difficulties in attaining phloem ingestion and increase in xylem ingestion. In addition to this common shift in probing behavior, a phloem-located resistance factor was inferred in DK72-10 based on the longer time spent in phloem conditioning to attain phloem ingestion. In contrast, DK390 expressed the highest level of mesophyll and phloem-based resistance, in both cases seen with repeated attempts of short duration, a behavior typically associated with failed attempts to ingest. These findings support and are consistent with previous research, providing useful information to characterize maize hybrids resistant to D. maidis, and consequently to corn stunt.