Alien Chromosome Transmission In The Backcross Progenies Of Gossypium Hirsutum-gossypium Stocksii

G.stocksii(2n=2x=26,E1),a diploid wild cotton species which mainly distributed in the Arabian Peninsula,Pakistan and the East african region,owns many excellent characters such as resistances to Leaf Curl Virus and other pests,good strength fibre,good water deficit tolerance.If these excellent genes can be introgressed into the land of cotton cultivation,it will broaden genetic basis ofG.hirsutum L which is the main cultivated cotton species,improve itsfiber quality and enhance its resistantance.The chromosomes of wild cotton lost easily in the backcross process since the genetic relationship between cultivated and wild cotton is distant.The results are as follows:(1)We have obtained the G.hirsutum-G.stocksiihexaploidand then backcrossed to G.hirsutum continuously.Finally,we obtained BC2,BC3 and BC4.We used the genomes ofG.stocksii and G.hirsutum as probes,the number of alien chromosomes of G.hirsutum ×G.stocksii in BC2 were indentified by using two-color fluorescence in situ hybridization(GISH).The number of alien addition chromosomes ranged from 0 to 10 and plants with 3 to 8 alien chromosomes accounted for 83.94%,of which plants with 5 alien chromosomes were the most,it’s 20.55%.The number of alien chromosomes of 75 plants in BC3 were indentified,the number ranged from 0 to 7 and plants with 0 to 4 alien chromosomes accounted for 89%,of which plants with 3 alien chromosomes were the most,it’s 32%.(2)We selectd 1402 pairs of markers on the D subgenome chromosomes to screen a set of G.hirsutum-G.stocksii alien addition lines polymorphic primers,according to the tetraploid cotton genetic map builded by our lab.We ultimately got a total of 411 pairs of polymorphic primers and then,removed the dense clusters and selected only one marker at an interval of 10 cM.Finally we got 313 pairs codominat primers to genotype the G.hirstum-G.stocksiialien addition lines and these primers were distributed on 13chromosomes of D subgenome in G.hirsutum.(3)Plants were identified in BC2 and BC3 by SSR and GISH and we found that after the pentploid of G.srocksiibackcrossed with TM-1,the original 13 chromosomes of G.stocksii would lost to varying degrees.We analyzed the transmission rates of 13 alien chromosomes of G.stocksii.The results showed that the chromosomes with low transmission rate were 5Es and 12Es,25%and 28%respectively.The transmission rate of other eleven chromosomes is higher,the 6Es is the highest,reaching 41%.On the whole,the transmission rate of the alien chromosomes of G.stocksii is relatively low during BC1 xTM-1,which also shows that the genetic relationship between G.stocksii and G.hirsutum is far and it caused loss of the alien chromosomes since not being properly matched in the meiosis period.(4)MAAL-1Es,MAAL-2Es,MAAL-4Es,MAAL-10Es,MAAL-11Es and MAAL-13Es were found in the 487 plants of BC2,BC3 and BC4 by SSR.MAAL-2Es,MAAL-4Es and MAAL-10Es were obtained in BC2.MAAL-1Es,MAAL-11ES and MAAL-13Eswere found in BC3,and it was regrettable that we didn’t gained MAAL-6Esalthough only 6Es and 13Es.This two alien chromosomes were lost during TM-1×BC3.(5)We found 59 albino seedlings in 352 plants of BC2 and BC3,the albino rate is about 16%.These albino seedlings were identified by SSR and the results showed that 57 albino seedlings contained 4Es chromosome,while 2 albino seedlings were MAAL-2Es.In three periods,we observed these albino seedlings.The albino type were spotted,reticular and massive and the albino positions were not same.There are slight albino in cotyledons,the albino in euphyllas,the albino in the edge of euphyllas and the albino in stems.The variation of albino seedlings was also different in three period and there were classified as recovery type,diffusion type and non-recovery type.(6)All the individuals of BCi,BC2 and BC3 were identified by molecular marker SSR and GISH.The traits were investigated.The traits mainly included bulging leaves,the exposed stigma,stigma didn’t fall off after pollination and glands in petals and so on.The traits of MAAL-1Es,MAAL-4Es and MAAL-11Es were not investigated since they are at the seedling stage.The results showed that the leaves of MAAL-2Es were albino,the leaves of MAAL-10Es were very dark and the stigma of MAAL-13Es were exposed.Plants with bulging leaves contained 1Es chromosome,with exposed stigma included 13Es,with stigma continuous growth included 5Es,10Es and 13Es,with glands in petals contained 2Es and 12Es in BC2.(7)We identified the pentploid,hexaploid of G.stocksii,some plants in BC2 by using two-color fluorescence in site hybridization.We found that the mitotic chromosomes showed similar law in the spatial arrangement,namely:the smallest chromosomes of D-subgenome were in center,while the most chromosomes of A and E genomes were distributed on the outer edge,and the chromosomes of D-subgenome were wrapped up,and there was no significant location relationship between chromosomes of A and E genomes.