Breeding resistance cultivars is the most economical, preferable, and effective method of control the wheat leaf rust caused by Puccinia recondita Roberge ex Desmaz. f.sp. tritici Eriks. & E. Henn. To date, fifty-six leaf rust resistance genes have been designated and mapped in wheat. The cultivars with single resistance gene released in wheat growing areas have quickly led to the selection for the corresponding virulence in the Puccinia recondita population, rendering the genes ineffective. Continued efforts to isolate, characterize, map wheat leaf rust resistance genes, breed wheat leaf rust resistance cultivars, and pyramid different resistance genes are important task for us in the future. Twenty-four leaf rust resistance genes had been targeted by RFLP (restriction fragment length polymorphism), RAPD (randomly amplified polymorphic DNA), SSR (simple sequence repeats), ISSR (inter-simple sequence repeat) and AFLP (Amplified fragments length polymorphism). In the study, AFLP analysis were carried out in T
hatcher and forty two near-isogenic lines carrying 48 different genes conferring resistance against leaf rust in order to establish the AFLP analyses system used in wheat, fingerprinting of forty two wheat leaf rust resistance near-isogenic lines and six monogenic lines, and develop molecular markers for genes Lr37 and Lr44 resistance to wheat leaf rust. The resistance genes to wheat leaf rust in 124 wheat cultivars (lines) had been identified using the gene postulation method and molecular marker-assisted selection. The main results derived from the research were as follows:
1) Appropriate AFLP system for wheat genome was established in T-gradient Thermal cycler PCR with wheat leaf rust resistance near-isogenic lines. 2) The comparison of the restriction enzyme combinations between PstI:Mse\ and EcoRI:Pstl indicted that the polymorphisms of wheat genomic DNA were different when AFLP was done by using combinations to digest the wheat DNA. The combination of PstI:MseI was more preferable for wheat genome digestion than the other combinations. 3) Fingerprint maps of near-isogenic lines for 48 monogenic lines were developed using AFLP technique. It would be useful for identifying leaf rust resistance gene and for detecting the admixture from seeds. 4) Four AFLP markers were developed for Lr44. The genetic map showed that the distance between Lr44 and Paag:Mcta300, Paac:Mcgt85, Paag:Mcta395,
Pagc:Mcgt90 were 0.01cM, 1.1 cM, 2.2cM, and 2.8cM, respectively. These molecular markers could be useful for establishment of the higher density genetic map and therefore in wheat assisted breeding program. Tow molecular markers were tagged for Lr37. They were named as Paac:McaC185, Paca:Mcac90, and the distances to Lr37 were 3.1cM, 0.8cM, respectively. 5) Twenty four leaf rust resistance genes including Lr1, Lr3, Lr3ka, Lr9, Lr10, Lr11, Lr12, Lr13, Lr14a, Lr14b, Lr16, Lr17, Lr18, Lr19, Lr22a, Lr22b, Lr24, Lr26, L30, Lr34, Lr35, Lr37, Lr38, Lr46 and other resistance genes absent in the tested near-isogenic lines were identified to be present in 124 wheat cultivars and breeding materials by using the genotype postulation method and molecular marker assisted selection. Lr9, Lr19, Lr24, Lr35 and Lr38 is very efficient resistance gene in the wheat growing areas. The research first show in the world that the Lr35 was present in some cultivars used in many years ago, such as "6068", "Baiyoubao", "Zhongmai No.9", "
Early Premium", "Bima No A", "Xiaoyan 7431", "Dongfanghong NoY', "Madsen". Lr38 was found in "Shenmian 99085","Shenmian 99042", "Shenmian 99052", "Shenmian 20169", "Mianzi 52","Shenmian 20167", "Shenmian 20160", "Shenmian 99142", "Yuanzhong No.4", "Xiaobing 33", "BL26" and "Agropyron intermedium" by using Lr38 AFLP marker Pacg:Mctg335 The result indicated that China is a leading country in using Lr35 and Lr38 for wheat leaf rust resistance breeding programs in the world. Moreover, it may also promote a step stone for a marker-assisted selection program and the eventual gene cloning for wheat leaf rust resistan
