| Flax (Linum usitatissimum L.) is known as both fiber and oil producing crop. Flax stems can provide natural fibers for textile industry, while flaxseeds can make healthy oil which contain high percent of unsaturated fatty acid. Along with the improvement of people's living standard, it become more and more important to develop flax production. Flax production has been restricted by some diseases, among them, flax rust caused by Melampsora lini Ehrenb. Lev. and flax wilt caused by Fusarium oxysporm f.sp. lini are two main diseases in flax. The most effective method to control these diseases is to screen and to breed resistant varieties. By identifying the molecular markers for resistant genes to rust and wilt and screening resistant germplasm in flax, we hope to set up a breeding procedure for maker-assisted selection and to get more resistant germplasm for flax breeding program. However, these works are still in a beginning stage in home and abroad. The major results in this paper are as follows:1. Identification of molecular markers for the rust resistance gene M4 in flax RAPD analysis of five near-isogenic lines, which contain MJ,M2,M3,M4 and A/5resistant(R) gene to flax rust, respectively, and their common recurrent parent, Bison, was carried out with 540 decamer primers. Two primers, OPA18 and OPC06, could stably amplify additional DNA fragments in the NM4 line which contain the R gene, M4. Using the F2 mapping population derived from a cross of Bison XNM4, the M4 gene was shown to be closely linked to an additional DNA fragment OPA18432 with a genetic distance of 2.1 cM. The cloned OPA18432was sequenced and then transformed to a SCAR marker. Analysis of different resistant materials with this marker proved its specificity for the M4 gene. Development of this M4 linked marker provides a good groundwork for marker-assisted selection in flax rust resistance breeding. Especially, the M4 gene performs high resistance to several rust pathogens in China, so it is more valuable than others. The specific molecular marker for M4 gene could been amplified from Jinya 8, a flax cultivar bred by the author, proving that it contain the M4 gene.2. Identification of molecular markers for the wilt resistance gene FuJ7(t) in flaxA cross between wilt resistant flax variety, Jinya 7, which was also bred by theVIauthor, and susceptible variety, Jinya 1, was made for mapping wilt resistance gene(s). Through inoculation test of its F, and F2 progeny, it is proved that the resistance of Jinya 7 to wilt is controlled by two dominant genes. With 48 EcoKl/Msel primer combinations, AFLP analysis was performed on two parents and their F2 resistance and susceptibility bulks. A total of about 3300 distinguishable bands were amplified, of which three were stable. The linkage analysis of the three polymorphic DNA fragments with the resistance gene(s) was tested in the F2 segregating population between Jinya 7 and Jinya 1. The DNA fragment AG/CAG was found closely linked to one of the wilt resistant genes, with a genetic distance of 5.2 cM, that was tentatively named FuJ7(t). The cloned fragment AG/CAG was sequenced and then transformed to a SCAR marker, which can be used more conveniently in the identification and marker-assisted selection for gene FuJ7(t).3. Identification and evaluation of flax germplasm for the resistance to wilt By using of the flax wilt nursery, which was established by the author, a total of 508 flax germplasm were identified and evaluated for their resistance to wilt. According to the reducing percent of wilt incidence compared with the uniform susceptible variety, the wilt resistance level were divided into six grades: high resistant (HR), mid resistant (MR), low resistant (LR), low susceptible (LS), mid susceptible (MS) and high susceptible (HS). The variety number of each grades are 45, 38, 64, 92, 112 and 157; the relevant percentages are 8.9%, 7.5%, 12.5%, 18.1%, 22.1% and 30.9%, respectively. The sum of high and mid resistant varieties accounts for only 16.4% of collectivity. It is show...
|
PDF Full Text Request