Development of wheat lines with complex resistance to rusts and Fusarium head blight

[摘要] Wheat is the second most important food crop worldwide. The world human population isincreasing daily. Sustainable food production is necessary to ensure sufficient futurefood supply. Wheat production is negatively affected by various pathogens thatchallenge breeders to develop more disease resistant wheat cultivars. Leaf-, stem- andstripe rust as well as Fusarium head blight (FHB) are considered some of the mostdestructive fungal pathogens of wheat. Resistance breeding is considered the mosteconomic and eco-friendly solution to control wheat diseases in the long-term.Combining of several effective resistance genes/quantitative trait loci (QTL) into a singlewheat line is necessary to increase the probability of obtaining durable resistance.Molecular markers linked to resistance genes/QTL can assist breeders in selecting thebest offspring throughout their breeding scheme.The main aim of this study was to develop a wheat line with combined resistance to therusts and FHB. Both wheat rust and FHB resistant lines used in this study weredeveloped in previous studies. The best resistant lines developed in these studies wereidentified using marker-assisted selection (MAS) and were then used in a breedingscheme to combine wheat rust and FHB resistance genes/QTL. Offspring from crosseswas evaluated for the presence of six rust resistance genes/QTL: Lr19, Lr34/Yr18/Sr57,Sr2/Yr30, Sr26, Sr39 and QYr.sgi.2B-1, as well as for three FHB resistance genes/QTL:Fhb1, Qfhs.ifa-5A-1 and Qfhs.ifa-5A-2. The best identified lines obtained from a series ofcrosses were selected to develop two double-cross populations as well as self-pollinatedpopulations. Selected pre-breeding lines were also used to optimise and apply thedoubled haploid (DH) technique to develop lines with fixed genotypes. Molecularmarkers linked to the high-molecular-weight glutenin subunits (HMW-GS) and the1BL.1RS translocation were used for screening the final populations developed becausethe primary focus for selection was rust and FHB resistance genes/QTL and not HMWGSand the 1BL.1RS translocation.Validation of the phenotypic expression of the rust and FHB resistance genes/QTL wasdone through greenhouse inoculation of the parental, control and experimentallines/cultivars containing different resistance gene/QTL combinations. Seedling and adultplants were inoculated with the three rusts respectively, firstly for the timeline study todetermine the optimal day's post inoculation (dpi) to collect sample material forquantitative-polymerase chain reaction (qPCR) analysis and secondly to determinefungal gene expression in the experimental lines. Both point and spray inoculations forFHB were used and disease development was evaluated at 4, 7, 10, 14, 18 and 21 dpi.Sample collection for qPCR analysis was done at 21 dpi. Good correlations between thedata obtained from the phenotypic evaluations, qPCR and MAS were obtained for bothrust and FHB resistance evaluations. Therefore, markers linked to rust and FHBresistance genes were phenotypically expressed.Lines with combined wheat rust and FHB resistance were obtained from the selfpollinatedpopulations but are still segregating for some of the genes/QTL. Lines withcombined rust and/or FHB resistance genes/QTL were also developed through the DHtechnique. No markers linked to stripe rust resistance were used in this study except forgenes with multiple disease resistance such as Lr34/Yr18/Sr57 and Sr2/Yr30. Additionalstripe rust resistance genes are however present in the genetic background of theexperimental lines as they were present in the parental cultivars/lines originally used todevelop these lines like Kariega, AvocetYrSP, 2S#/163 and CM-82036. Valuable prebreedingwheat lines with combined rust and FHB resistance have been developedwhich can be used in future disease resistance breeding programmes.

[发布机构] University of the Free State