Methodologies used for screening and determining resistance to the European corn borer
1989
Guthrie, W.D. | Barry, B.D. (USDA Agricultural Research Service, Ankeny, IA (USA). Corn Insects Research Unit)
In first-generation European corn borer (ECB), Ostrinia nubilalis Hubner, resistance studies, maize, Zea mays L., plants are infested with egg masses or larvae during the midwhorl stage of plant development. The relative degree of resistance (antibiosis) is measured by rating leaf-feeding damage on plants (individual plant or plot basis) in classes 1 = no damage to leaf tissue to 9 = extensive damage. Leaf-feeding damage ratings are made 3 weeks after egg hatch or larval infestation in second-generation ECB resistance studies, maize plants are infested with egg masses or larvae during anthesis. The relative degree of antibiosis is measured by rating sheath-collar feeding damage on plants (plot basis) in classes 1 = no damage to 9 = extensive damage. Sheath-collar feeding ratings are made 45 to 60 days after infestation. Genotypes with ratings of 7 to 9 are discarded. Cavity counts (cm of damage in stalks) may be used to detect differences among genotypes with ratings of 1 to 6. Genotypes are evaluated for tolerance by determining percentage of broken stalks as an index of stalk strength and by determining percentage of dropped ears as an index of shank strength.
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