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Title: Identifying rare FHB-resistant transgressive segregants in intransigent backcross and F2 winter wheat populations

Author
item CLARK, ANTHONY - University Of Kentucky
item SARTI-DVORJAK, DANIELA - University Of Kentucky
item Brown-Guedira, Gina
item DONG, YANHONG - University Of Minnesota
item Baik, Byung-Kee
item VAN SANFORD, DAVID - University Of Kentucky

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2016
Publication Date: 5/7/2016
Citation: Clark, A., Sarti-Dvorjak, D., Brown Guedira, G.L., Dong, Y., Baik, B.V., Van Sanford, D. 2016. Identifying rare FHB-resistant transgressive segregants in intransigent backcross and F2 winter wheat populations. Frontiers in Microbiology. 7:277.

Interpretive Summary: Fusarium head blight (FHBin the US, is one of the most destructive diseases of wheat. FHB-infected grain is usually contaminated with deoxynivalenol (DON) a mycotoxin that threatens food and feed safety. Developing FHB-resistant wheat is widely acknowledged to be one of the best ways of reducing DON in food and feed. The primary challenge in resistance breeding is combining adequate resistance with superior agronomic and quality characteristics. Exotic QTL are widely used to improve FHB resistance. Success depends heavily on the genetic background into which the QTL are introgressed, whether through backcrossing or conventional forward crossing. This study began when four elite, high-yielding soft red winter wheat breeding lines with little or no scab resistance were each crossed to a donor parent (VA01W-476) with two resistance genes: Fhb1 (chromosome 3BS) and QFhs.nau-2DL (chromosome 2DL) to generate backcross and F2 progeny. F2 individuals were genotyped and assigned to 4 groups according to presence/ absence of one or both resistance genes. The effectiveness of these genes in reducing FHB rating, incidence, index, severity, Fusarium-damaged kernels (FDK) and DON, was assessed in a misted, inoculated scab nursery over two years. Fhb1 showed an average reduction in DON of 17.5%, and conferred significant resistance in 3 of 4 populations. QFhs.nau-2DL reduced DON 6.7 % on average and conferred significant resistance in 2 of 4 populations. The combination of Fhb1 and QFhs.nau-2DL resistance reduced DON 25.5% across all populations. Double resistant lines had significantly reduced DON compared to double susceptible lines in 3 of 4 populations. Some lines showed much greater than average improvement in FHB resistance. Backcross derived progeny in the four populations were planted in replicated yield trials (2011 and 2012) and in an irrigated, inoculated scab nursery in 2012. In one population (2), the yields of 23% of the 90 lines tested were not significantly different from the high yielding commercial cultivars used as checks. Several of the lines at the very top of the yield trial also performed well in the scab nursery, with acceptable DON concentrations, even though the average effect of either gene in this population was not significant. In resistance breeding population selection is often viewed as an “all or nothing” process: if the average resistance level is insufficient, the population is discarded. These results indicate that it may be possible to find transgressive segregants which combine scab resistance, superior agronomic performance and acceptable.

Technical Abstract: Fusarium head blight (FHB), caused mainly by Fusarium graminearum Schwabe [telomorph: Gibberella zeae Schwein.(Petch)] in the US, is one of the most destructive diseases of wheat (Triticum aestivum L. and T. durum L.). FHB-infected grain is usually contaminated with deoxynivalenol (DON) a mycotoxin that threatens food and feed safety. Developing FHB-resistant wheat is widely acknowledged to be one of the best ways of reducing DON in food and feed. The primary challenge in resistance breeding is combining adequate resistance with superior agronomic and quality characteristics. Exotic QTL are widely used to improve FHB resistance. Success depends heavily on the genetic background into which the QTL are introgressed, whether through backcrossing or conventional forward crossing. While QTL expression varies greatly depending on genetic background, penetrance is impossible to predict. This study began when four elite, high-yielding soft red winter wheat breeding lines with little or no scab resistance were each crossed to a donor parent (VA01W-476) with resistance alleles at two QTL: Fhb1 (chromosome 3BS) and QFhs.nau-2DL (chromosome 2DL) to generate backcross and F2 progeny. F2 individuals were genotyped and assigned to 4 groups according to presence/ absence of resistance alleles at one or both QTL. The effectiveness of these QTL in reducing FHB rating, incidence, index, severity, Fusarium-damaged kernels (FDK) and DON, in F2-derived lines was assessed in a misted, inoculated scab nursery over two years. Fhb1 showed an average reduction in DON of 17.5%, and conferred significant resistance in 3 of 4 populations. QFhs.nau-2DL reduced DON 6.7 % on average and conferred significant resistance in 2 of 4 populations. The combination of Fhb1 and QFhs.nau-2DL resistance reduced DON 25.5% across all populations. Double resistant lines had significantly reduced DON compared to double susceptible lines in 3 of 4 populations. Some lines showed much greater than average improvement in FHB resistance. Backcross derived progeny in the four populations were planted in replicated yield trials (2011 and 2012) and in an irrigated, inoculated scab nursery in 2012. In one population (2), the yields of 23% of the 90 lines tested were not significantly different from the high yielding commercial cultivars used as checks. Several of the lines at the very top of the yield trial also performed well in the scab nursery, with acceptable DON concentrations, even though the average effect of either QTL in this population was not significant. In resistance breeding population selection is often viewed as an “all or nothing” process: if the average resistance level is insufficient, the population is discarded. These results indicate that it may be possible to find transgressive segregants which combine scab resistance, superior agronomic performance and acceptable quality even in populations in which the average effect of the QTL is muted or negligible.