Development Of DNA Molecular Markers For Genes Of Wheat Rust Resistance

The genes for leaf rust resistance Lr34 and for stem rust resistance Sr31 are all the most important resistance genes against rust fungi in wheat in the world. It is important for utilizing Z,r34 and Sr3l rapidly and effectively in wheat breeding program to develop the molecular markers linked to resistant genes and establish the technical system of molecular marker assistant breeding.DNA polymorphism of the near isogenic lines and chromosome substitution lines with/without Lr34 were analyzed using AFLP method. A total of 78 random primer pairs were screened to identify the AFLP markers linked to Lr34 gene. Two polymorphic DNA fragments with the molecular weight of 237bp and 300bp respectively were amplified by a pair of specific primers ( E03 : 5'-GACTGCGTACCAATTCAAT -3' and M01: 5'- GATGAGTCCTGAGTAACAT -3' ) in the resistant parents and not in the susceptible parents. The 237bp polymorphic DNA fragment was separated, cloned and sequenced. Based on the sequence, the specific primer pairs could be designed and the linkage analysis between the polymorphic DNA fragment and the resistant gene (Ir34) would be further conducted in the near further.Of seven specific primer pairs designed with the software of Primer 5.0 according to the previous sequence of the DNA polymorphic fragment related to Sr3l, a gene for stem rust resistance, one primer pair (BR41: 5'cac ccc ctt ggt age aca 3'and BR12: 5'age cag tat cct cca cct cct 3') can produce a 331bp specific band in the resistant parents and without in the susceptible parents of NILs and other materials. Two F2 segregating population of resistance to stem rust sourced from the crossing of Kavkaz McNair701 and Lovrinl3 McNair701 were constructed separately, the former with 123 F2 plants and the later with 120 FI plants. The seedling infection types of F2 plants were recorded based on the scale of Roelfs (1992) after inoculated with the dominant race 21C3 of Puccinia graminis f. sp. tritici. The results of genetic analysis indicated that the stem rust resistance to 21C3 in Kavkaz and Lovrin13 controlled respectively by one dominant gene and two complementary dominant genes. All plants of F2 generation was separately detected by the specific SCAR marker of Sr31 gene. Genetic linkage between SCAR marker and Sr31 were analyzed by the software of Map Manager QTXb17. The results indicated that the SCAR marker was obviouslylinked with the Sr31 gene. The genetic distances is 25.8cM±4.2cM in the combination of Kavkaz D McNair701 and 19.3cM±3.4cM in the combination of Lovrin13 a McNair701 respectively. It suggested that the SCAR marker of Sr31 could provide an useful tool for identifying resistance genes and assistant selection in wheat breeding program.Several questions were also discussed in this paper that included the reliability and points for attention of AFLP, gene kind of RAPD marker, identification of translocation with RAPD and the prospective of SCAR marker of Sr31 in wheat breeding for resistance.