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Germplasm evaluation for resistance to insect pests of the sunflower head

Charlet, L.D., Aiken, R.M., Miller, J.F., Seiler, G.J., Grady, K.A., Knodel, J.J.
Proceedings / Sunflower research workshoop 2007 no.9
Helianthus annuus, insect pests, resistance mechanisms, germplasm evaluation, flowers, Homoeosoma electellum, Smicronyx fulvus, Cochylis hospes, Contarinia schulzi, seeds, larvae, crossing, lines, hybrids, integrated pest management, North Dakota
The key insect pests attacking the sunflower head and seeds include the sunflower moth, the red sunflower seed weevil, the banded sunflower moth, and the sunflower midge. There is a need to reduce losses from these pests by providing long-term economical management for sunflower growers. In 2005, sunflower accessions and interspecific crosses were screened for those having reduced seed damage from larval feeding by the seed weevil and two moth species. Discovery of germplasm that has less insect damage can provide breeding lines to be incorporated into hybrids targeted to locations where specific insect problems occur. This will increase grower confidence in being able to produce a profitable crop. Plots were established in nurseries in Kansas and North and South Dakota, regions where these insects have caused economic losses. In 2006, commercial hybrids were evaluated in North Dakota for tolerance to the sunflower midge. Results from 2005 identified promising resistance in germplasm against the three insects studied. There was a reduction in seed damage of 90% and 80% between the most susceptible and the most resistant line in the sunflower moth and banded sunflower moth trials, respectively. The red sunflower seed weevil trial had some genotypes with a 70% to 80% reduction in seed damage. After each year of testing, lines with low damage levels are retested to confirm their resistance to attack. The resistance mechanisms responsible for lower percentage of seeds consumed by larvae of the banded sunflower moth, sunflower moth, or red sunflower seed weevil have not been determined. These may be the subject of later studies once resistant germplasm for each insect has been confirmed. The sunflower midge trial in 2006 revealed that among the hybrids evaluated there were differences in susceptibility to infestation. Thus, some available hybrids offer the potential to lessen the impact of midge damage enabling growers to make informed choices when selecting hybrids to grow in locations where a midge infestation might be anticipated.