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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Sunflower and Plant Biology Research » Research » Publications at this Location » Publication #177178
Title: INHERITANCE OF SCLEROTINIA HEAD ROT RESISTANCE IN NUSUN AND TRADITIONAL SUNFLOWER HYBRIDS

Author
item MILLER, JERRY
item GULYA JR, THOMAS
item HAMMOND, JAMES - NORTH DAKOTA STATE UNIV.

Submitted to: Proceedings Sunflower Research Workshop
Publication Type: Proceedings
Publication Acceptance Date: 2/2/2005
Publication Date: 2/8/2005
Citation: Miller, J.F., Gulya Jr, T.J., Hammond, J.J. Inheritance of sclerotinia head rot resistance in NuSun(R) and traditional sunflower hybrids. Proceedings Sunflower Research Workshop. Available: http://www.sunflowernsa.com/research/research-workshop/documents/Miller_etal_HeadRot_05.PDF

Interpretive Summary: Sclerotinia is one of the most important diseases attacking sunflower in the United States and is also encountered in all sunflower-growing regions of the world. The fungus can attack several plant parts, but in the United States, the two most common forms of the disease are stalk rot or wilt and head rot. The importance of additive or nonadditive gene action involved in the expression of Sclerotinia resistance is of great interest to sunflower breeders in order to select the best strategy for developing resistant hybrids. Little research has been focused on differences that may exist between NuSun sunflower hybrids and traditional oil sunflower hybrids in their reaction to Sclerotinia head rot infection. Therefore, the objective of this study was to cross Sclerotinia resistant germplasm with various high oleic acid and low oleic acid lines to create NuSun and traditional sunflower hybrids and determine their reaction to artificial infection under the mist irrigation system. There were highly significant differences among hybrids tested for resistance to Sclerotinia head rot. The highest percentage of plants infected by Sclerotinia was found in the hybrid cms HA 403 X RHA 409 at 75.8%. The lowest percentage of plants infected was found in the hybrid cms HA 441 X RHA 439 at only 2.5%. The general combining ability (GCA) effects of both the females and males were highly significant. However, the GCA effects of the male lines accounted for 64% of the treatment sums of squares, suggesting that male effects were more important in controlling Sclerotinia head rot resistance than female effects. The ratio of GCA to SCA was large, indicating that additive gene effects were more important than nonadditive gene effects in the variation expressed among hybrid combinations. This experiment indicated the importance of testing hybrid combinations under the mist irrigation system utilizing artificial inoculation. The degree of resistance of the NuSun hybrids was excellent. Two of the three NuSun hybrids tested in this experiment equaled or were more resistant than the resistant check. The Sclerotinia stalk rot resistant line, RHA 409, appeared to not have any contribution of genes for resistance for Sclerotinia head rot. Therefore, a line possessing genes for Sclerotinia stalk rot resistance does not necessarily indicate that it also possesses genes for resistance to Sclerotinia head rot. Hybrids will need to be evaluated for both diseases to create hybrids acceptable to sunflower producers.

Technical Abstract: Sclerotinia sclerotiorum is one of the most important diseases attacking sunflower (Helianthus annuus) in the United States and is also encountered in all sunflower-growing regions of the world. The fungus can attack several plant parts, but in the United States, the two most common forms of the disease are stalk rot or wilt and head rot. The importance of additive or nonadditive gene action involved in the expression of Sclerotinia resistance is of great interest to sunflower breeders in order to select the best strategy for developing resistant hybrids. Little research has been focused on differences that may exist between NuSun sunflower hybrids and traditional oil sunflower hybrids in their reaction to Sclerotinia head rot infection. Therefore, the objective of this study was to cross Sclerotinia resistant germplasm with various high oleic acid and low oleic acid lines to create NuSun and traditional sunflower hybrids and determine their reaction to artificial infection under the mist irrigation system. There were highly significant differences among hybrids tested for resistance to Sclerotinia head rot. The highest percentage of plants infected by Sclerotinia was found in the hybrid cms HA 403 X RHA 409 at 75.8%. The lowest percentage of plants infected was found in the hybrid cms HA 441 X RHA 439 at only 2.5%. The general combining ability (GCA) effects of both the females and males were highly significant. However, the GCA effects of the male lines accounted for 64% of the treatment sums of squares, suggesting that male effects were more important in controlling Sclerotinia head rot resistance than female effects. The ratio of GCA to SCA was large, indicating that additive gene effects were more important than nonadditive gene effects in the variation expressed among hybrid combinations. This experiment indicated the importance of testing hybrid combinations under the mist irrigation system utilizing artificial inoculation. The degree of resistance of the NuSun hybrids was excellent. Two of the three NuSun hybrids tested in this experiment equaled or were more resistant than the resistant check. The Sclerotinia stalk rot resistant line, RHA 409, appeared to not have any contribution of genes for resistance for Sclerotinia head rot. Therefore, a line possessing genes for Sclerotinia stalk rot resistance does not necessarily indicate that it also possesses genes for resistance to Sclerotinia head rot. Hybrids will need to be evaluated for both diseases to create hybrids acceptable to sunflower producers.