Location: Plant Genetics Research
Project Number: 5070-21000-041-023-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Oct 1, 2020
End Date: Jun 30, 2022
Objective:
Evaluate bacterial isolates for effects on the western corn rootworm and maize.
Approach:
The greenhouse methods will utilize methods similar to those previously published by ARS. Briefly, Clay or plastic pots filled with growth medium will be watered until saturation prior to the planting of seeds. Pots will contain ~3.3 liters of growth medium. Two corn seeds will be planted per pot equidistant from the center at a depth of ~2.5 cm. A 114-µm stainless steel mesh screen. will be glued over the pot drainage hole to prevent larval escape out the bottom. Following coleoptile emergence, the entirety of the smaller seedling will be removed to achieve one corn plant per pot. Pots will be watered to saturation as needed throughout the entirety of the experiment. Once plants reached the V3-V4 growth stages (Ritchie et al. 1992), a small hole will be made 1-2 cm from the base of the plant to a depth of ~2.5 cm and used as the infestation site. All pots will be infested with ~70 western corn rootworm eggs. Extra pots not used in the replications will also be infested to be checked for larval development.
During the warmer months of the year, activity will shift to field experiments focused on approximately 40 bacterial isolates selected from those originating from Missouri. For field experiments, nine kernels will be planted in 1.8 m-long single row plots with an implement developed by ARS which was specially designed for plots of this size. Plots will be artificially infested at a level to be determined by egg availability and project goals, but a trap crop for natural rootworm infestation will also be used. For any artificial infestation, western corn rootworm eggs will be suspended in 0.15% agar solution and used to mechanically infest plots at ~V2 stage of plant development with ARS’ implement designed for this purpose. Prior to root excavation, barcoded plot information will be affixed to four plants per plot. Roots will be excavated after most WCR feeding is completed. This will be determined by monitoring growing degree days Excavation will be accomplished using a specially designed, tractor-mounted implement. Roots will be soaked, washed, and rated for damage using a 0 to 3 scale.
