Identification And Application Of New Dwarf And Semi-dwarf Trititrigia Germplasms

The Green Revolution in the 1960s set off a wave of dwarf breeding.As one of the world’s most important food crops,the breeding and popularization of dwarf and semi-dwarf wheat varieties greatly promoted yield increase.However,with the excessive application of a few dwarf genes in breeding practice,it has caused serious homogenization of wheat germplasm,which limits the further improvement of wheat production potential.Thinopyrum ponticum（2n=10x=70,St St St St E^eE^eE^bE^bE^xE^xor JJJJJJJ^SJ^SJ^SJ^S）is a tertiary gene pool of wheat and the valuable sources of wheat genetic improvement,which contains abundant excellent traits.In our laboratory,a series of Trititrigia germplasms with outstanding specific traits were bred by hybridizing common wheat with Th.ponticum.In this study,on the basis of morphological identification,cytogenetics and molecular biology techniques were used to identify dwarf and semi-dwarf Trititrigia,and the following main results were obtained:1.Four wheat-Th.ponticum alien addition lines were obtained.The chromosome numbers of B21028,B21035,B21038 and B21039 were 2n=43,2n=43,2n=44 and 2n=45,respectively.GISH-FISH results showed that all of them carried a pair of alien chromosomes,in which B21028 and B21035 lacked a 5D and 1D chromosome,respectively,while B21039 had an extra4A chromosome.The plant height of B21028 was 68.6 cm,the spike length was 10.2 cm,the number of grains per spike was 82,and the thousand-grain weight was 40.72 g.It had excellent comprehensive characters and could be further used to product alien substitution lines and translocation lines.2.A wheat-Th.ponticum 1E^b（1B）disomic alien substitution line was obtained.The height of B21036 was 61.8 cm,which was shorter than its parents SNTE20（127.6 cm）and Jimai22（71.1 cm）.The number of grains per spike was 55,which was 3.8%more than Jimai22.GISH-FISH identification showed that the number of chromosomes was 2n=42,in which a pair of 1B chromosomes of B21036 was replaced by a pair of Th.ponticum chromosomes.It was found that there were structural variations in the chromosomes 2AS,5AS,7AS,3BS and 6BS during its formation.Eight pairs of IT markers derived from the homeologous group one were detected,and four of them can amplify the specific bands in both Th.ponticum and Th.bessarabicum,indicating that the alien chromosome is the 1E^b chromosome of Th.ponticum.Therefore,B21036 is a 1E^b（1B）disomic alien substitution line.3.Two wheat-Th.ponticum translocation lines were obtained.B21032 had stem thickness,which plant height was 48.9 cm.GISH-FISH identification results show that B21032Dan-5 and 10 are heterozygous reciprocal translocation lines involving chromosome 6A;Compared with the FISH pattern of the parents,it was found that there were structural variations in the chromosomes 5AS,6AS,7AL,4BS,5BS,6BL,7BL,1DS,2DL,and 2DS;Three pairs of specific IT markers derived from the homeologous group six were screened by molecular marker analysis,and two pairs of them could amplify obvious specific bands in both Th.ponticum and Th.bessarabicum,indicating that the alien fragment was derived from the 6E^bchromosome of Th.ponticum.Therefore,B21032 is T6AL·6AS-6E^b+T6AS·6AL-6E^btranslocation line.The plant height of B21043 was 62.5 cm,the number of grains per spike was76,and the thousand-grain weight was 55.93 g,all the data were higher than that of the parent Shannong 637.GISH-FISH results showed that the alien fragment in B21043 translocated at the end of the long arm of 3D chromosome.FISH band analysis showed that the chromosomes2A,5A,7AS,1BL,3BL,4BL,6BL,7BS and 2DS had structural variations.Therefore,B21043was a wheat-Th.ponticum 3DS·3DL-Tp disomic translocation line（Tp represents the fragment of Th.ponticum）.4.Thirteen wheat-Th.ponticum introgression lines were obtained.B21026,B21033,B21041,B21047,B21049-1,B21025,B21048,B21050,B21054,B21055,B21056,B210645-14 and B210645-17 all contained 42 wheat chromosomes,and GISH did not find alien genetic signal,indicating that the alien fragments are relatively small,and they are wheat-Th.ponticum introgression lines.B21026,B21033,B21041,B21047,and B21049-1 were compared with the FISH pattern of the parents,and found many differences,indicating that chromosomal structural variation occurred during formation.Among them,B21033 had more spikes（18）and grains per spike（69）than those of the parents,and the thousand-grain weight（54.22 g）was higher than that of the parents.B21026 had more spikes（11）than those of the two parents,and the thousand-grain weight（50.57 g）was higher than that of the parents;the grains of both were plump and the grain width was average wider than those of the parents.In addition,there grain length was longer than most of the parents,with excellent comprehensive traits.Therefore,both of them can be used as a parent in wheat breeding practice.5.In order to make full use of the positive characters,the translocation lines B21032 and B21043 were used as parents to cross with common wheat（such as Shannong 34,Shannong28,and Shannong 29）and 16 combinations were developed,and the F₂ generation has been obtained so far,which laid the foundation for its effective application in breeding.