Molecular And Cytogenetic Identification On Derivatives Of Wheat-thinopyrum Ponticum

Thinopyrum ponticum(Th.ponticum)(2n = 10 x = 70)is an important breeding material with excellent resistance and stress tolerance.By the method of distant hybridization,a large number of wheat-Th.ponticum derivatives could be obtained,such as alien addition lines,alien substitution line,and translation lines.These derivatives can provide important intermediate material to translate excellent genes into wheat,which were benefit to rich wheat germplasm resources and broaden the genetic base of wheat.In this study,many wheat-Th.ponticum derivatives were screened and identified by using morphological observation,cytological identification,in situ hybridization analysis,molecular marker analysis,and disease resistance identification.The main conclusions are as follows:1.The BC1F5 and BC1F6 lines of wheat-Th.ponticum derivatives were identified.It was found that the number of chromosomes of root tip cells in these two generations was from 40 to 57,and the two generations had a lot of variation of chromosome numbers;There were many univalent,telocentric chromosome,trivalent,or quadrivalent in the pollen mother cells in the meiosis.The results of GISH showed that the number of alien chromosomes was still unstable in most of the materials,and further selfing,screening and identification were needed to obtain stable materials.The results of cytological identification during two generations laid the foundation for subsequent identification and screening of wheat-Th.ponticum derivatives.2.The FISH karyotype of 1E-7E chromosomes of Thinopyrum elongatum(Th.elongatum)was constructed.Using the probes of Oligo-pTa535 and Oligo-pSc119.2,a complete set of alien addition lines of the wheat-Th.elongatum was conducted FISH analysis.The results showed that a pair of chromosomes was different from the FISH karyotype of common wheat in every wheat-Th.elongatum 1E-7E disomic alien addition lines.Compared and analyzed these seven pairs of chromosomes,the FISH karyotypes of 1E-7E chromosomes of wheat-Th.elongatum were constructed,and they were provided reference for FISH identification of alien chromosomes.3.Identification of wheat-Th.ponticum derivatives CH1115-B15.CH1115-B15 was the BC1F5 of progeny of the cross 7182/Th.ponticum//87-1-9.The results of cytological identification showed that the somatic cells contained 44 chromosomes and the PMC MI configuration was: 2n = 0.22 I+21.87 II+0.01 IV.The GISH and FISH analysis showed that there were two J(E)chromosomes derived from Th.ponticum,and the FISH signals of alien chromosomes were different form the FISH signals of Th.elongatum.Molecular markers analysis showed that CH1115-B15 contained the genetic materials of Th.ponticum which belonged the fifth homoeologous group.Thus,CH1115-B15 was a wheat-Th.ponticum 5J(E)disomic alien addition line.The results of salt tolerance test and disease resistance test showed that CH1115-B15 had excellent agronomic traits,and it also had high resistance to wheat stripe rust and high salt tolerance,and longer kernel than its wheat parents.We were presumed that the(a)new salt tolerance gene(s)and the control kernel length gene(s)existed on chromosome 5J(E)of Th.ponticum.4.Identification of wheat-Th.ponticum derivatives CH1113-B13.CH1113-B13 was the BC1F5 of progeny of the cross 7182/Th.ponticum//Zhongmai 895.The results of cytological identification showed that the somatic cells contained 42 chromosomes and the PMC MI configuration was: 2n = 20.97 II+0.06 I.The GISH and FISH analysis showed that there were two JSt chromosomes derived from Th.ponticum,and a pair of 7B chromosomes was absent.Molecular markers and Nulli-tetrasomic analysis showed that CH1113-B13 contained the genetic materials of Th.ponticum which belonged the senventh homoeologous group,and a pair of 7B chromosomes was missed.Thus,CH1113-B13 was a wheat-Th.ponticum disomic alien substitution line which carried a pair of 7JSt chromosome from Th.ponticum and a pair of 7B chromosome from common wheat was absent.The results of disease resistance test showed that CH1113-B13 was immune to wheat stripe rust,and its common wheat parents were susceptible to the disease.So we assumed that(a)new wheat stripe rust tolerance gene(s)was(were)existed on chromosome 7JSt of Th.ponticum.This research based on the identification of BC1F5 and BC1F6 lines of wheat-Th.ponticum derivaties by molecular cytology and construction of the FISH karyotype of Th.elongatum 1E-7E chromosomes,screened and identified a wheat-Th.ponticum 5J(E)disomic alien addition line with high resistance to wheat stripe rust and high salt tolerance,and a wheat-Th.ponticum 7JSt/7B disomic alien substitution line with high resistance to wheat stripe rust.These were provided important intermediate materials for wheat breeding.