Physical Mapping Of Rye Chromosomes 2R And 6R And Allocation Of Powdery Mildew Resistance Genes

Secale cereale L.cv.Jingzhouheimai(JZHM)confers high resistance to several wheat diseases such as powdery mildew,sharp eyespot and wheat yellow mosaic virus,which represents an important genetic resource for wheat improvement.In our previous studies,a wheat landrace Huixianhong(HXH)-rye cv.JZHM amphiploid Jinghui 1 and a series of HXH-JZHM alien chromosome lines involving different chromosomes were developed in Cytogenetic Institute,Nanjing Agricultural University(CINAU).Two powdery mildew resistance genes were allocated to the long arms of chromosomes 2R and 6R,respectively.To precise map and use these powdery mildew resistance genes,28 and 9 markers(polymorphism rate 16.2%)specific for chromosomes 2R and 6R were identified from 637 primer pairs designed using wheat EST and gSSR,rye EST,barley and Brachypodium genomic sequences at CINAU.To efficiently develop more markers,343 new primer pairs were designed using the up-regulated transcriptome sequences of JZHM induced by Bgt(Blumeria graminis f.sp.tritici).From these primers,30 and 12 markers specific for 2R and 6R were identified with a polymorphism rate at 53.9%,which was quite higher than the former,indicating a new and efficient method to develop specific markers.From previous 88 aberrations involved 2R,17 stable structural aberrations were characterized after sequential GISH/FISH and molecular marker analysis.These lines included 7 whole arm translocations,6 small segmental translocations,3 large segmental translocations,and 1 deletion line.88 markers including 30 previous reported were physically mapped to 13 blocks of 2R,including 3 on 2RS named 2RS-1?3 and 10 on 2RL named 2RL-1?10.The powdery mildew resistance gene PmJZHM2RL was mapped to block 2RL-7,which included 18 markers with 10 from up-regulated genes of rye.Disease resistance test using 25 virulent isolates collected from China indicated that H-J DA6R might carry different resistance gene preliminarily named PmJZHM6RL.55 chromosome 6R aberrations were induced by spontaneous breakage and reunion,irradiation and zebularine.20 stable lines were identified after sequential GISH/FISH and marker analysis,which included 11 whole arm translocations,2 large segmental translocations,3 deletion lines,2 ditelosomic additions and 2 isochromosomes.44 markers including 23 previously reported were mapped to 6 blocks including 3 on 6RS and 3 on 6RL.The resistance gene PmJZHM6RL was mapped to block 6RL-2,which contained 29 markers with 9 from up-regulated genes of rye.Fourteen translocations including 6 involved 2RL and 8 involved 6RL showed powdery mildew resistance,10 translocations involved 2RL showed reduced plant height,and one translocation involved 2RL showed increased thousand kernel weight,among these translocations,4 translocations involved 2RL showed powdery mildew resistance and promise agronomic traits,indicating new genetic resources for wheat improvement.