CURRENT STATUS OF BIOTYPE COMPOSITION IN HESSIAN FLY POPULATIONS FROM THE EASTERN UNITED STATES AND EFFECTIVENESS OF RESISTANCE GENES IN WHEAT

Authors: Ratcliffe, Roger; OHM, HERBERT - PURDUE UNIVERSITY; PATTERSON, FRED - PURDUE UNIVERSITY; Cambron, Sue

Submitted to: Southern Small Grain Workers Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/22/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Research determined the frequency of resistance-breaking races, or biotypes, in Hessian fly populations from mid-Atlantic, southeastern, and mid-south states in the eastern United States soft winter wheat growing region. This information is vital in order to determine the effectiveness of currently grown Hessian fly resistant wheat varieties, since the fly gradually adapts genetically to specific sources of resistance over time. The biotype make-up of these populations indicated that four of five Hessian fly resistance genes presently incorporated in soft winter wheat varieties are ineffective in managing fly populations from the mid-Atlantic states, and that only two of the five genes are effective in much of the southeastern and mid-south area. Fortunately, the wheat variety INW9811, which was released jointly by USDA, ARS and Purdue University in 1998, was resistant to fly populations representative of those found in the eastern U.S. Although INW9811 is not adapted to growing conditions throughout the eastern U.S., the resistance associated with the H13 gene can be incorporated and used effectively in locally adapted varieties in the future. Thirty-five of forty Purdue wheat breeding lines evaluated against eastern Hessian fly populations also demonstrated a broad range of resistance. Many of these wheat lines should be important sources of resistance for improving wheat varieties in the future to manage resistance breaking fly biotypes. This research benefits public and private soft winter wheat breeders, and ultimately wheat producers, in the eastern United States by identifying the most effective Hessian fly resistance genes to incorporate in new wheat varieties. Up-to-date information is essential in order to control resistance-breaking biotypes of the insect.

Technical Abstract: Twenty four Hessian fly populations collected from the eastern United States soft winter wheat growing region in 1999 and 2000 were evaluated for biotype composition and virulence to deployed resistance genes in wheat. Based on biotype frequency in these fly populations, we concluded that wheat varieties carrying resistance genes H3, H5, H6, and H7H8 would be relatively ineffective as a management tool in much of the eastern U.S. I more southern portions of Alabama, Arkansas, Georgia, and South Carolina, resistance assocated with the gene combination H7H8 would still be effective, based on the absence or relatively low frequency of the biotype L. Research with the soft red wheat cultivar INW9811, released jointly by Purdue University and USDA, ARS in 1998, demonstrated that resistance was effective against fly populations from throughout the eastern U.S. that had a high frequency of biotype L. The resistance in INW9811 is associated with the H13 gene originally selected from Triticum tauschii, a wild relative of wheat. Although INW9811 is not adapted to growing conditions throughout the eastern U.S., the resistance associated with the H13 gene can be incorporated and used effectively in locally adapted varieties in the future. Forty wheat lines from the Purdue breeding program also were evaluated for resistance to fly populations representative of those found in the eastern U.S. Thirty-five lines demonstrated excellent resistance to all populations and will serve as potential sources of resistance to incorporate into wheat cultivars of the future to manage resistance breaking biotypes. The gene(s) conferring resistance are not known in all thirty-five lines. Research to determine the presence of new, or unique, genes in these lines, is underway.