| Wheat is an extremely important staple food crop all around the world.But along with the continuous growth of the world population and constantly appearing of the pests and diseases,the wheat production is endangered and breeding has become more urgent.Developing wheat varieties with high yield,stable yield,disease resistances and high quality is the main target of wheat breeding.During the planting process the genetic background of wheat gradually narrows and diversity decreases,so it is very difficult to resist when new pathogens emerge.Therefore,it becomes pressing for wheat breeding to excavate the good traits or genes from the near or distant species,broaden the genetic resources,and enrich the inheritance diversity of wheat.Thinopyrum intermedium,belonging to the genus Elymus of grass family,is one of important species of tertiary gene pool for wheat improvement and studied by researchers for a long time.On the one hand,it has abundant genetic diversity and possesses genes conferring resistance to various diseases,such as leaf rust,stem rust,root rot,fusarium head blight,barley yellow dwarf virus,stripe mosaic virus,insect pest,and also has tolerance for some abiotic stresses.On the other hand,it is easy for Th.intermedium to hybridize with wheat,so the beneficial genes can be imported into the wheat background for breeding purposes.In the present study,we screen and analyze the hybridization derivatives of line Z4and common wheat MY11 using fluorescence in situ hybridization(FISH)and molecular marker.At the same time,the investigation and statistics of their agronomic characters and disease resistance are also carried out,which lay a foundation for the follow-up wheat breeding.The main results of this study are as follows:(1)Using fluorescence in situ hybridization,the chromosome karyotypes of Z4and its parent Zhong5 are identified.Also we found that Tr-?and Tr-?,two pairs of translocation chromosomes of Z4,were from Zhong5 and respectively corresponded to the F and G chromosomes of Zhong5.FISH with pDb12H as probe identified the J~S chromosomes involved in Z4.FISH karyotypes of 351 progenies derived from crosses between Z4 and MY11 indicated that the transmission of the translocated chromosomes appeared normal and the number of wheat chromosomes 3A and 3D frequently varied.There are some special materials:S2-8(2n=42)contained two Tr-I chromosomes with the absence of 3A;S49(2n=44)had two Tr-II chromosomes,four 3D with the absence of 3A;d77(2n=43)contained two Tr-I and one Tr-II chromosomes with the absence of 3D.(2)The FISH signal distribution of a new repetitive probe,named Oligo-3A1,confirmed the physical breakage points on chromosome 3AL incorporated into translocated chromosomes.PLUG markers revealed the breakage points on chromosomes 3A,7J~S,and 3D invloved in the translocated chromosomes,and they were designated as T3DS-3AS.3AL-7J~SS and T3AL-7J~SS.7J~SL.It is proved that the 3A chromosome breakpoint was located between 566.87Mb-568.09Mb and the breakage point of 7J~S for chromosomes Tr-I and Tr-II was located between TNAC1797 and TNAC1917.And it is found that chromosome Tr-I contains an added distal region of10%of the short arm from 3DS.(3)Stripe rust resistance responses of Z4 and its derived progenies were measured at the adult plant stages in the field.Experimental results of cytology and molecular biology indicated that the stripe rust resistance was from the Th.intermedium 7J~S of Tr-II responsible for high resistance.In the present study,the Tr-II translocation clearly showed an improvement in the grain weight in the progenies of Z4ŚMY11 hybrids,and further selection of the superior main yield-related traits will be feasible by reducing the 7J~S fragment size by chromosome engineering.It has been more than 20 years since Z4 was created.However,Z4 still displays resistance to stripe rust which is of great significance to the breeding of wheat.Our study lays a foundation for the future application of Z4 in wheat genetic breeding. |
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