Identification And Genetic Analysis Of Wheat-Thinopyrum Ponticum Germplasm Line

Thinopyrum ponticum?2n=10x=70?is a perennial plant of the genus Thinopyrum,which is closely related to common wheat and has become an important gene pool for genetic improvement of wheat.The wheat-Thinopyrum ponticum derived germplasm lines are valuable intermediate material for transferring superior genes between Th.ponticum and wheat.This study identified and screened the progenies of wheat-Th.ponticum,and developed germplasms with excellent agronomic traits,good disease resistance,low plant height,and we have identified their genetic composition.The main results are as follows:?1?Nine octoploid Trititrigia,SN0389,SN0392,SN0398,SN0399,SN0401,SN0402,SN0403,SN0404,and SN0406,which were derived from wheat-Th.ponticum were identified in this study.Plant heights were between 101.0 cm and 144.5 cm,and the length of spike ranged from 10.75 cm to 16.83 cm.There were many variations among traits such as ear type,awn type,and spikelet arrangement,and they also had strong resistance to common wheat diseases such as powdery mildew,stripe rust,and leaf rust.?2?The RTC results ofcctoploid Trititrigia SN0389,SN0398,SN0399 and SN0406showed that SN0389 has 54 chromosomes?2n=54?and that of SN0398,SN0399 and SN0406are 56?2n=56?.PMC research results show that SN0389 has 27 bivalents,while SN0392,SN0398,SN0399,SN0401,SN0402,SN0403,SN0404 and SN0406 all have 28 bivalents.The in situ hybridization results showed that the chromosome composition of SN0389 was14A+14B+14D+12J^s,and the chromosome composition of SN0398,SN0399 and SN0406both were 14A+14B+14D+12Js+2J.The results of FISH and GISH also showed that the J^schromosomes in theses four octoploid Trititrigia were not identical.FISH and McGISH were used to analyze the variation of wheat chromosomes in these octoploid Trititrigia,9pairs of chromosome mutations were detected in the three chromosome groups,respectively are 1A and 3A,6A,4B,5B,6B,1D,2D and 5D.The octoploid Trititrigia have diferent variation types and good resistance to different diseases,and also keep genetic stability in cytology,thus make them valuable bridge materials in the wheat improvement.?3?The plant heights of the dwarf germplasms SN31504,SN31504-1,SN31504-2,SN31504-3,SN31505 and SN31505-1 of wheat-Th.ponticum were between 53.00 cm and59.70 cm,all of which were gibberellic acid-insensitive.Compared with the parent Lumai5,the internode length of the dwarf germplasms shortened significantly,the number of internodes decreased,the number of sterile spikelets and thousand kernel weight decreased,the spike length,the number of spikelets per spike,and the number of grains per spike increased significantly.Different soil environments have a greater impact on the growth of dwarf germplasms.The higher nitrogen and phosphorus content in the soil would increase the plant height,panicle length and the area of flag leaf,and it also will affect the the length of the internodes and reduce the thousnad kernel weight of the dwarf germplasms.?4?The RTC results of the dwarf germplasms showed that SN31504,SN31504-1,SN31504-2,SN31504-3,and SN31505 were all have 42 chromosomes,and SN31505 has 44chromosomes.In the PMC MI,line SN31505 forms 22 bivalents,the other 5 dwarf lines form21 bivalents,they all have high genetic stability.Three sets of FISH probes?pAs1+?GAA?8,pSc119.2-1+pAs1-4+?GAA?10+?AAC?6,AFA-3+AFA-4+pAs1-1+pAs1-3+pAs1-4+pAs1-6+?GAA?10+pSc119.2-1?were used to identify the genetic composition of dwarf germplasms.Chromosomal variations were detected at 14 sites on 11 chromosomes.Absent of fluorescence signals were detected on 7 positions in 2AL,4AL,2BL,3BL,6BL,6BS,and1DL chromosomes.The additional fluorescence signals were detected on 5 positions in 4BS,6BL,1DS,and 2DL chromosomes,and replacement of different fluorescence signals was detected at 5AL and 6AL chromosomes.?5?The identification of dwarf lines using specific molecular markers of Th.ponticum and dwarf gene markers showed that the dwarf germplasm lines all contain the chromosome segments from Th.ponticum and also contain the dwarf genes Rht-B1b and Rht8.Genetic analysis of the plant height of the dwarf germplasm line SN31504-2 showed that the proportion of inverting four and below internodes of SN31504-2/Lumai 5 F₂ and dwarf parent SN31504-2 to plant height was significantly less than higher parents,and the number of internodes is generally less than the high stalk parent.Twelve pairs of SSR primers were used to anlysis the F₂ populations of SN31504-2/Lumai 5,and a genetic map containing two linkage groups was constructed,involving the long arms of both chromosomes 2A and 2D,and there have no major QTL which associated with plant height was be detected.