Development And Characterization Of Wheat-Ae.Geniculate 7M~g Recombinants With Powdery Mildew Resistance

Powdery mildew,caused by the powdery mildew fungus Blumeria graminis f.sp.Tritici（Bgt）,is a fungal disease in the Poaceae family and one of the major diseases affecting wheat.It has a significant impact on global wheat production and quality.Breeding resistant cultivars is the most effective,economical,and environmentally friendly strategy to curb this disease.Aegilops geniculata Roth（syn.Aegilops ovata L.,2n=4x=28,U^gU^gM^gM^g）,is an allotetraploid plant belonging to the genus Aegilops.It is classified as a tertiary gene pool species It possesses several desirable traits,including resistance to powdery mildew,stem rust,leaf rust,insects,abiotic stress,and high grain protein content et al,it is an important genetic resource for wheat improvement.The 7M^gchromosome of Aegilops geniculata carries highly resistance genes against powdery mildew,its a crucial target chromosome for breeding disease-resistant wheat varieties.we aimed to introduce 7M^gchromosome from 7M^g（7A）alien disomic substitution line into ph1b background to induce genetic exchange between the alien chromosomes and their wheat homoeologous chromosomes,and to identify translocations with improved inheritance of PM resistance.Molecular marker detection and cytological identification methods were employed to screen for plants with chromosomal translocations,and their resistance to powdery mildew was assessed.The translocations with PM gene（s）can be used for breeding disease-resistant wheat varieties.The major findings are as follows:（1）Four specific molecular markers for the 7M^gchromosome were developed,which are located in the proximal region of the short arm,near the centromere,and the proximal region of the long arm.These markers,namely Q_7M/Q_7A-64Mb,Q_7M/Q_7A-111Mb,Q_7M/Q_7A-476Mb,and P_7M/P_7A-736Mb,can be used for the detection of the 7M^gchromosome or its fragments.（2）Chinese Spring（CS）-Aegilops geniculate 7M^g（7A）alien disomic substitution line TA6646 were hybridized with the ph1b mutant SM830ph1b ^H.Plants homozygous for the ph1b deletion carrying the alien chromosome 7M^gwere identified from the segregating populations using molecular markers.Then,eight types（14 plants）of translocations between the 7A-7M^g（three types,5 plants）or 7D-7M^g（five types,9 plants）chromosomes were identified from selfing F₃and F₄by molecular markers and confirmed by genomic in situ hybridization（GISH）and fluorescence in situ hybridization（FISH）.（3）All translocations were highly resistant to powdery mildew,that brings closer the wheat improvement of disease resistance breeding.Meanwhile,Four newly-developed specific makers are able to efficiently detect the 7M^gand identifying secondary translocations.