2009 Annual Report
1a.Objectives (from AD-416)
The objectives of our proposed research are threefold: (1) To evaluate cultivated sunflower and wild Helianthus species for insect and disease resistance, concentrating on those diseases and insects which are of greatest impact to the U.S. sunflower industry, (2) to develop and phenotype segregating populations for DNA marker discovery, which will be used to supplement classical breeding methods to identify breeding material with improved agronomic, disease and insect resistance traits, and (3) to develop advanced germplasm which carry genes for insect and disease resistance.
1b.Approach (from AD-416)
To identify new sources of insect and disease resistance in sunflower we will evaluate, either under natural infestations (insects) or with artificial inoculations (diseases) a diverse selection of sunflower germplasm, including breeding populations, USDA Plant Introductions, and wild species (obtained from a companion research project 5442-21000-034-00D). For diseases, we will focus on Sclerotinia, downy mildew, and rust. The major insect pests in our studies are the sunflower stem weevil, sunflower moth, and banded sunflower moth. We have developed segregating populations for some insect and diseases, and are developing others. These populations will be used by the project molecular geneticist to identify markers for these traits. Phenotyping will be done at several locations, using either natural insect infestations or artificial inoculations for diseases. Finally, using field plots with natural insect infestations or artificial disease inoculations, and supplemented by marker-assisted selection, we will evaluate the new sources for resistance to the major insect pest species and disease pathogens and transfer that resistance into genetic stocks or advanced USDA germplasm for release to the public.
We evaluated about 250 germplasm sources including accessions, F3:4 lines, and interspecific crosses for resistance to one or more key insect pests of sunflower, including the sunflower moth and sunflower stem weevil in Kansas, the red sunflower seed weevil in South Dakota, and the banded sunflower moth in North Dakota. Each insect is the subject of a separate phenotypic recurrent selection program, and all four populations are beginning the third cycle of selection this year. Testcrosses (experimental hybrids) of the F3:4 banded sunflower moth and red sunflower seed weevil resistant lines are currently under evaluation in North Dakota and South Dakota, and will allow us to see the effectiveness of the resistance in sunflower hybrids.
Studies also were conducted to evaluate selected commercial sunflower hybrids for tolerance to damage by the sunflower midge, sunflower seed maggot, and sunflower bud moth. We organized, for a second year, a network of cooperators to monitor flight activity of the sunflower moth from southern Texas to Canada using pheromone traps to provide a system to alert consultants and growers when moths are active in the area. This information is plotted weekly on a map available on university and industry websites. Research was continued on a study to develop a degree-day model for banded sunflower moth emergence and flight activity using pheromone traps in North Dakota, South Dakota, Minnesota, and Manitoba.
Two hundred sixty diverse cultivated sunflower germplasms were evaluated for Sclerotinia stalk rot resistance in inoculated field trials at three locations, which will complete a two-year study. In addition to identifying new sources of resistance, the combined data set from five environments will be used in a subsequent association mapping study. Twenty-six accessions of seven annual wild Helianthus species were tested in two inoculated field trials for stalk rot resistance, which required transplanting over 3000 plants. Breeding material from three other unit scientists was evaluated for head rot and stalk rot resistance in six inoculated nurseries in Minnesota and North Dakota. The effect of root exudates of six different crops on the mode of sclerotial germination was studied in a greenhouse trial. Two hundred rust samples collected from six states were identified to race, completing a two-year effort totaling over 400 isolates. Downy mildew samples were collected for race identification and to monitor the possible development of fungicide resistance.
Transfer of downy mildew resistance into multiple genetic backgrounds was continued, effectively combining this resistance with IMI herbicide resistance, Sclerotinia resistance, and altered fatty acid profiles. Rust resistant populations are in the early stages of development, and this resistance will be placed in an elite genetic background with other already stacked traits in both confectionery and oilseed backgrounds. We began work to investigate sources of resistance to Verticillium wilt, and have F2 populations segregating for Verticillium wilt resistance genes, as well as other stacked traits, in both confection and oilseed background.
Identification of Sclerotinia stalk rot resistance in wild annual Helianthus species. Sclerotinia stalk rot is one of the major diseases affecting U.S. sunflower production, annually found in up to a third of all fields and destroying up to 3% of the crop. Improved levels of stalk rot resistance have previously been incorporated into public and private germplasm, but the resistance sources were always derived from other cultivated sunflower. In an attempt to broaden the genetic basis of Sclerotinia resistance and identify new sources of resistance, ARS scientists in the Sunflower Research Unit, Fargo, ND, initiated a project in cooperation with the USDA Plant Introduction Station, Ames, IA, to (1) develop a greenhouse resistance evaluation method, and (2) evaluate over 300 available accessions of the 15 annual Helianthus species. This research resulted in the identification of 20 accessions of seven annual species with stalk rot resistance superior to the best commercial hybrids. After confirmation by field tests, these wild species will be used in our breeding program. Release of sunflower germplasm with enhanced Sclerotinia resistance derived from wild species will provide public and private breeders with genetically more diverse sunflower sources for production of seed that will increase profitability to producers and improve quality for consumers.
Resistance among sunflower germplasm to stem-infesting insect pests. Insect pests attacking sunflower stems in the central Plains, including the sunflower stem weevil and a longhorned beetle, cause plants to fall over, reducing crop yield for producers. A 7-year field study by ARS scientists at the Sunflower Research Unit in Fargo, ND, evaluated 61 sunflower accessions and 31 crosses with wild sunflower species for resistance to attack by naturally occurring populations of the stem weevil, longhorned beetle, and a root boring moth at two locations in the central Great Plains. They identified germplasm with potential sources of resistance to attack from all three stem-infesting pests. Results from the study showed potential for developing resistant genotypes for these stem-infesting insect pests of sunflower and further effort is anticipated to utilize the identified lines and interspecific crosses to introduce resistance genes into cultivated sunflower. The prospect of adding host-plant resistance as an integrated pest management tactic provides another tool for reducing economic losses from insect pests of sunflower in the central Great Plains.
Morris, B.D., Charlet, L.D., Foster, S.P. 2009. Isolation of Three Diterpenoid Acids from Sunflowers, as Oviposition Stimulants for the Banded Sunflower Moth, Cochylis hospes. Journal of Chemical Ecology. 35:50-57.
Charlet, L.D., Aiken, R.M., Miller, J.F., Seiler, G.J. 2009. Resistance Among Cultivated Sunflower Germplasm to Stem-Infesting Pests in the Central Great Plains. Journal of Economic Entomology. 102(3):1281-1290.