Utilization of Cross-Resistance to Create Herbicide-Resistant Sunflower Hybrids J. F. Miller, USDA-ARS, Northern Crop Science Laboratory, Fargo, ND 58105 R. Zollinger, North Dakota State University, Plant Science Dept., Fargo, ND 58105 Introduction Hybrid sunflower (Helianthus annuus L.) producers had very few herbicides available for controlling broadleaf weeds. The discovery of wild sunflower populations resistant to the imidazolinone and sulfonylurea classes of herbicides gave sunflower breeders the opportunity to create cultivated sunflower hybrids with resistance to these classes of herbicides (Al-Khatib et al., 1998). Beyond herbicide, a herbicide in the imidazolinone class, has been registered for application on Clearfield sunflower (Zollinger, 2003). Germplasm with resistance to the Express sulfonylurea herbicide has been released to sunflower breeders (Miller and Al-Khatib, 2004). These two herbicides control many of the broadleaf weeds causing yield losses in sunflower. Cross-resistance among the common mutations of ALS genes have been reported as early as 1992 (Guttieri et al., 1992). The mutation of ALA205 to VAL at the conserved region AFQEPT of the ALS gene gave high resistance to the imidazolinone herbicide, Beyond, but only moderately low resistance to Express (Bruniard, 2001). However, in a study conducted by Fabie and Miller (2002), the USDA source of Express resistance (USDA GH274-1) gave moderately high cross-resistance to the Beyond imidazolinone herbicide, as well as complete resistance to the Express sulfonylurea herbicide. Results of their study indicated that the conserved region of the ALS gene involved in the USDA SU-resistant germplasm would be the AITGQVPRRMIGT region, or a mutation of the PRO197. The 197 and 205 amino acid positions refer to the equivalent positions in the Arabidopsis thaliana L. ALS gene. Two breeding lines from the USDA genetics project, 02 1339-2 and 02 1404-5, were treated with a 2X application of Express and Harmony GT, with the 1X rate being 1/3 oz/a and 6/10 oz/a for the two herbicides, respectively. The USDA 02 1339-2 line was highly resistant to Express 2X and Harmony GT 2X applications. However, the USDA 02 1404-5 line was highly resistant to Express 2X and completely susceptible to Harmony GT 2X. The pedigrees of the two lines differ in that the herbicide resistance was derived from different wild plants discovered in Kansas. The objective of this study was to determine if the powerful cross-resistance in the USDA 02 1339-2 line could be utilized in hybrids, which can be sprayed with Express and Harmony GT sulfonylurea herbicides and also the Beyond imidazolinone herbicide.
Materials and Methods The treatments are listed in Table 1. HA 89 was the susceptible check. The SU X SU hybrid was the sulfonylurea herbicide-resistant check and the IMI X IMI hybrid was the imidazolinone herbicide-resistant check. Table 1. Line or hybrid and their respective female and male parents sprayed with three herbicides, Express, Harmony GT, and Beyond, at Fargo, ND, 2004. HA 89 (Susceptible check inbred line) SU X SU USDA 02 1339-2 X SURES-2 Sel. IMI X IMI HA 425 X RHA 426 SU X Sus USDA 02 1339-2 X HA 434 Sus X SU HA 434 X SURES-2 Sel. SU X IMI USDA 02 1339-2 X RHA 426 IMI X SU HA 425 X SURES-2 Sel. IMI X Sus HA 425 X HA 434 Sus X IMI HA 434 X RHA 426 All treatments were sprayed with a 0.5X, 1.0X, and 2.0X rate of Express, Harmony GT, and Beyond herbicides. The recommended 1X rates of these herbicides are 1/3 oz/a (Express), 6/10 oz/a (Harmony GT), and 4 oz/a (Beyond). All plants were sprayed with the herbicides in the Weed Science spray chamber at North Dakota State University by Ron Roach. The plants were in the V4 to V6 leaf stage (Schneiter and Miller, 1981) when sprayed. Six days after herbicide application, plants were visually scored for damage. The score was based on chlorosis of leaf tissue, damage sustained by the meristematic tissue, and leaf crinkling. A score of 100 indicated completely dead, and a score of 0 indicated no damage. Results and Discussion The differing reactions of the two USDA lines, 02 1339-2 and 1404-5, to the Express and Harmony GT applications in the field indicate that plants from the same wild species population collected in Kansas may have different resistant genes and produce reactions to herbicide applications differing than those expected. Breeders are cautioned to spray plants with different herbicides before crossing to cultivated lines to insure the transfer of specific resistance genes.
Based on the reactions of the SU X SUS and the SUS X SU hybrids after spraying with Express and Harmony GT, the resistance in the USDA 02 1339-2 and SURES-2 SEL parents was dominant (Table 2 and 3). Hybrids with the USDA 02 1339-2 used as a female parent had about 5 to 10% less damage than hybrids with the SURES-2 SEL used as the male parent after the two hybrids were sprayed with Express and Harmony GT. These results indicate that the 02 1339-2 parent has background genes or modifier effects imparting to or improving resistance. Crossing an SU resistant parent with an IMI resistant parent (SU X IMI and IMI X SU hybrids) increased resistance 10 to 40% over that of the SUS X IMI and IMI X SUS hybrids after application of the Beyond herbicide (Table 4). These results indicate that cross-resistance was contributed by the SU parent and expressed in hybrids sprayed with Beyond. The SU X IMI and IMI X SU hybrids sustained only 5 to 10% more damage than the IMI X IMI check hybrid when sprayed with the Beyond imidazolinone herbicide (Table 4). The contribution of resistance by the SU-resistant parents to hybrids that will be sprayed with the Beyond herbicide will need to be determined in field studies during the summer of 2004 to verify whether this resistance is adequate for commercial purposes. Acknowledgments The authors gratefully acknowledge the assistance of Ron Roach, Weed Science, Department of Plant Science, North Dakota State University for his assistance in spraying all plants, Dale Rehder and Bruce Goren, for their assistance in making crosses and organizing the entries for proper and timely treatment. References Al-Khatib, J. R. Baumgartner, D. E. Peterson, and R. S. Currie. 1998. Imazethapyr resistance in common sunflower (Helianthus annuus L.). Weed Sci. 46:403-407. Bruniard, J. M. 2001. Inheritance of imidazolinone resistance, characterization of crossresistance pattern, and identification of molecular markers in sunflower (Helianthus annuus L.). Ph.D. Dissertation, North Dakota State University, Fargo, ND. p. 1-78. Fabie, A., and J. F. Miller. 2002. Cross-resistance of two sulfonylurea-resistant sunflower sources to selected ALS herbicides. Proc. 24 th Sunflower Research Workshop, Fargo, ND. 17-18 January 2002. p. 117-122. Guttieri, M. J., C. V. Eberlin, C. A. Mallory Smith, D. C. Thill and L. Hoffman. 1992. DNA sequence variation in Domain A of the acetolactate synthase genes of herbicideresistant and susceptible weed biotypes. Weed Sci. 40:670-678. Miller, J. F., and K. Al-Khatib. 2004. Registration of two oilseed sunflower genetic stocks, SURES-1 and SURES-2, resistant to tribenuron herbicide. Crop Sci. 44:in press.
Schneiter, A. A., and J. F. Miller. 1981. Description of sunflower growth stages. Crop Sci. 21:901-903. Table 2. Injury to the sunflower line or hybrids from Express sulfonylurea herbicide applied at three rates in the greenhouse, Fargo, ND, 2004. Express Injury Rating HA 89 75 80 85 SU x SU 0 0 0 IMI x IMI 20 25 60 SU x Sus 5 5 10 Sus x SU 5 10 15 SU x IMI 0 0 5 IMI x SU 10 15 20 Sus x IMI 50 50 65 IMI x Sus 50 50 65 Injury rating: 0 to 100 scale, with 0=no damage and 100=all tissue dead.
Table 3. Injury to the sunflower line or hybrids from Harmony GT sulfonylurea herbicide applied at three rates in the greenhouse, Fargo, ND, 2004. Harmony GT Injury Rating HA 89 75 75 80 SU x SU 5 10 20 IMI x IMI 65 65 75 SU x Sus 5 0 15 Sus x SU 10 15 30 SU x IMI 0 5 20 IMI x SU 10 5 25 Sus x IMI 75 75 80 IMI x Sus 50 65 75 Injury rating: 0 to 100 scale, with 0=no damage and 100=all tissue dead. Table 4. Injury to the sunflower line or hybrids from Beyond imidazolinone herbicide applied at three rates in the greenhouse, Fargo, ND, 2004. Beyond Injury Rating HA 89 75 85 85 SU x SU 40 50 65 IMI x IMI 0 5 25 SU x Sus 25 50 75 Sus x SU 35 60 65 SU x IMI 5 10 35 IMI x SU 5 15 40 Sus x IMI 15 35 75 IMI x Sus 15 40 65 Injury rating: 0 to 100 scale with 0=no damage and 100=all tissue dead.