Molecular Mapping Of Leaf Rust Resistance Gene In Chinese Wheat Line Zhoumai22and Romanian Wheat Line Fundulea900

Wheat leaf rust, caused by Puccinia triticina, is one of the most important and widespread wheat diseases in the world. Given favorable conditions, the disease can causeyield losses of up to40%. Resistant cultivars are the most efficient, economic andenvironmentally-friendly way for reducing the losses caused by the disease. Wheat leafrust resistances are divided into seedling resistance and adult palnt resistance. Theseedling resistance is race specific resistance controlled by single gene, and it may loseresistance when virulent races emerge or increase. Adult plant resistance （APR） is non-racespecific resistance controlled by polygene, and it is considered as durable resistance.Therefore it is necessary to study leaf rust resistance at both seedling stage and adultplant stage to understand the resistance completely. QTL analysis can be used to mapresistance genes in wheat lines with APR. Zhoumai22, Chinese spring, and their Fl, F2populations and F_2:3lines were inoculated with Chinese Puccinia triticina pathotypeFHDQ in greenhouse for genetic analysis of wheat leaf rust resistance gene in Zhoumai22. The results showed that F2population segregated for a single gene, fitting3:1ratioand F_2:3lines also segregated monogenically, fitting1:2:1ratio. Results from the F2andF_2:3populations indicated that a single dominant gene, tentatively designated LrZH22,conferred resistance to P. triticina pathotype FHDQ. Fundulea900, Thatcher, and theirF_2:3populations were used to map APR QTLs for leaf rust in Fundulea900using mixedP. triticina pathotypes.1) SSR markers were used to test the parents and their resistant and susceptiblebulks. The polymorphic SSR markers between the resistant and susceptible bulks wereused to test all the F_2:3lines. Linkage analysis was conducted with the software MapManager QTXb20. Results indicated that Zhoumai22carried a single dominantresistance gene LrZH22, located on chromosome2BS. The resistance gene LrZH22wasclosely linked to the six known SSR locis （Xbarc55、Xgwm374、Xgwm148、Xgwm410、Xbarc183and Xwmc474） on the2BS with genetic distance ranging from2.5cM to12.6cM. The two closest flanking SSR locis were Xbarc55and Xgwm374with geneticdistances of2.5cM and4.7cM, respectively.2) Five formally named leaf rust resistance genes Lr13, Lr23, Lr48, Lr16and Lr35 were located on chromosome2BS. In the seedling test Zhoumai22, RL4031（Lr13）and RL6012（Lr23） were inoculated with13P. triticina pathotypes. The result showedthat Lr13and Lr23were susceptible to most of P. triticina pathotypes, indicating Lr13and Lr23were different from LrZH22, and temperature sensitivity test futher confirmedLr13was different from LrZH22. Lr16was susceptible to all leaf rust isolates, so it wasdifferent from LrZH22. Lr35and Lr48were adult resistanc genes and insensitivity totemperature, and their positions on chromosome were different from LrZH22. Based onthe discussion above it can be concluded LrZH22is likely to be a new leaf rust resistancegene.3) A total of188F_2:3lines derived from the cross Fundulea900/Thatcher wereinoculated with mixed P. triticina pathotypes in2010-11and2011-12crop seasons forscoring leaf rust severities in the field. Five super-resistant lines and fivesuper-susceptible lines were selected to build small resistant and susceptible groups. Atotal of1300SSR and1STS markers were used to screen between parents and smallgroups. Polymorphic markers between parents and small groups were used to test F_2:3lines. Software Map Manager QTXb20and QTL Ici Mapping3.1were used for linkagemapping and QTL analysis. One QTL for the resistance to leaf rust was detected onchromosome7DS, and it might be Lr34. The QTL explains81.21%and64.64%ofphenotypic variance in2010-11and2011-12seasons, respectively.