Advances in rating and phytochemical screening for corn rootworm resistance
1997
Moellenbeck, D.J. | Bergvinson, D.J. | Barry, B.D. | Darrah, L.L.
Evaluating and identifying sources of resistance to the corn rootworm, Diabrotica spp., continues to be a challenge due to subterranean feeding by the larvae and the destructive sampling to evaluate resistance. With the development of artificial infestation techniques, screening for resistance has progressed rapidly. However, evaluation of resistance continues to be labor intensive, with the most accurate rating system requiring root extraction, cleaning, and visual assessment of damage. Because field sampling and evaluation is costly, new evaluation techniques are constantly being evaluated. Refinement of field evaluation techniques using vertical root pulling resistance has increased the amount of corn germplasm that can be evaluated. In addition, consistent preliminary evaluations in the greenhouse and laboratory can reduce the amount of material screened in more costly field evaluations. Greenhouse evaluations have been used successfully to screen both maize germplasm and Tripsacum dactyloides L. for corn rootworm resistance. With the identification of DIMBOA as an antibiosis resistance mechanism, screening for elevated levels of DIMBOA in the roots can now be done on a large scale. Using a hydroponic system, over 100 genotypes a day can be evaluated for hydroxamic acid content and root mass. Genotypes with good root growth and high DIMBOA levels have shown field resistance to both artificial and natural infestations of Diabrotica spp. in sandy-loam and clay soil types. Bioassay systems are presently being developed to further large-scale screening efforts as well as our understanding of resistance mechanisms and feeding behavior of Diabrotica spp.
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