Evaluation Of Wheat Leaf Rust Resistance Of23Chinese Wheat Mini-core Collections And Molecular Mapping Of Leaf Rust Resistance Genes In Een1at Seedling Stage

Wheat leaf rust, caused by Puccinia triticina, is one of the most important andwidespread diseases in China. It is adapted to a wide range of climates, occurs whereverwheat is grown, and can cause significant yield and economic losses. Given favorableconditions, the disease can cause yield losses up to or above40%. Uilization of theresistant cultivars is the most economical, effective and safe way to control wheat leaf rust.The newly appeared races of pathogens or the secondary races became the pandemic racesmade the cultivars lose resistance easy. Therefore, identification of resistance genes,polymerization of multiple resistance genes and resistance breeding are important tasks toprevent and control wheat leaf rust effectivly.Chinese wheat mini core collections are important source of parents in modern wheatbreeding, and are important material basis for breeding new wheat varieties of high yieldand quality. Resistance evaluation and resistance gene postulation of the23accessionswere carried out at seedling and adult stages. A series of molecular markers linked to wheatleaf rust resistance genes were used for marker test of these accessions.The objective ofthis study was to determine the leaf rust resistance of23mini-core wheat accessions, andto detect the Lr genes related to resistance. Een1developed by West Hubei HongmiaoAgricultural Sciences Institute, showed high resistance to leaf rust in the field. In this study,F1, F2plants and F3lines from a cross between resistant line Een1and susceptible lineThatcher were used for molecular mapping leaf rust resistance genes in Een1by genepostulation, genetic analysis and SSR markers. This study provided the basic informationof leaf rust resistance of Chinese wheat mini core collections, and provided the basis forbreeding for disease resistance. The main results were obtained as follows:1. Resistance evaluation and resistance gene postulation of the23accessions werecarried out with12races with different virulences of P. triticina at seedling stage. Theresults showed that Huoqiu, Atlas66, Jianmai, Xiaofoshou, Baitiaoyu, Laoqimai,Jinhuangmai, Fengmai11, Tongjiabaxiaomai, Honghuamai, Chinese Spring,Shanhongmai, Hongheshangtou, Galaohan and Shanmai all displayed high levels of Infection type, so the Lr genes contained could not be postulated. Kefeng3,Bailanghuimai, Fumai and Zhengyin4had different infection type (IT) patterns withthe near-isogenic lines (NILs). They might carry unknown resistance genes or otherknown resistance genes to wheat leaf rust which were not used in the tester lines. Lr1and Lr17were postulated in Yannong15. Lr15was detected in Yunmai34. Lr14a andLr32were suggested in Muzongzhuoga.2. Ten races of P. triticina were mixed and inoculated the23test accessions in field todetect the field reaction to wheat leaf rust at adult stage. Bailanghuimai,Muzongzhuoga, Jinhuangmai and Yunmai34displayed low IT of “;” or “;1”, andconferred nearly immune. Bainong3217displayed low IT of “;3” with30diseaseindex, it blonged to middle resistant level. Chinese Spring displayed high IT of “34”with50disease index, it blonged to susceptible resistant level. The other17accessionsdisplayed IT of “;3”“;4”or“;2”, and with less than10disease index.They belonged tohighly resistant level.3. Twenty four molecular markers closely linked or co-segregated with Lr1, Lr2c, Lr9,Lr10, Lr16, Lr19, Lr20, Lr21, Lr24, Lr25, Lr26, Lr28, Lr29, Lr32, Lr34, Lr37, Lr38,Lr42, Lr48and LrZH84were employed to molecular assisted identify the wheat leafrust resistance genes. The specific fragments of Lr1, Lr10, Lr26, Lr34, Lr37, Lr2c,Lr16, Lr32, Lr42and LrZH84were detected in the test genotypes either alone or invarious combinations.4. Combining with gene postulation, field reaction at adult stage and molecularcharacterization, the synthetical resistance analysis indicated that: the23accessionsfrom wheat mini-core collections all showed good resistance except Chinese Spring,and were postulated to carry some resistance genes. Lr34and unknown Lr genes inHuoqiu, Laoqimai, Fengmai11, Shanhongmai, Hongheshangtou, Fumai, Galaohan andZhengyin4. Lr34was found in Chinese Spring. Lr1and Lr34were found in Jianmaiand Xiaofoshou. Lr34and Lr32were identified in Tongjiabaxiaomai and Honghuamai.Lr10, Lr34, Lr16and Lr32were postulated in Kefeng3. Lr1, Lr2c and Lr32werefound in Atlas66. Lr1and Lr17were postulated in Yannong15. Lr26, Lr16, Lr42andLrZH84were postulated in Baitiaoyu. Lr26combined with suggested Lr14a inMuzongzhuoga. Lr1, Lr34and Lr32were postulated in Jinhuangmai. Lr26, Lr37,LrZH84and maybe Lr15were detected in Yunmai34. Lr1and Lr16in Bainong3217.Besides, Bailanghuimai and Shanmai may carry un-known resistance genes to wheatleaf rust. The results indicated that the resistance genes in response to leaf rust diseasewere relatively richer in the23Chinese wheat mini-core collections, and the Chinesewheat mini-core collections could be applied in breeding programs for leaf rustresistance.5. Een1and35near-isogenic lines with known leaf rust resistance genes were inoculated with12pathotypes of P. triticina for postulation of leaf rust resistance genes effectiveat the seedling stage. The result showed that the response pattern of Een1was differentwith the35known Lr resistance genes used in the test and Een1may carry new leafrust resistance gene (s).6. Een1, Thatcher, and their Fl, F2populations and F3families were tested for wheat leafrust resistance with Chinese P. triticina pathotype FHNQ in greenhouse. The resultsshowed that Een1was resistant to FHNQ with infection type “;” and Thatcher wassusceptible to FHNQ with infection type “4”, F2population segregated for a singlegene, fitting3:1ratio and F3lines also segregated monogenically, fitting1:2:1ratio.Results from the F2and F3populations indicated that a single dominant gene,tentatively designated as LrE1, conferred resistance to P. triticina pathotype FHNQ inEen1.7. SSR primers were used to test the parents and their resistant and susceptible bulks. Thepolymorphic SSR markers between the resistant and susceptible bulks were used foranalying the F3lines. Linkage analysis was conducted with the software MapManagerQTXb20. Results indicated that Een1carried a single dominant resistance gene LrE1to FHNQ, located on chromosome7BL. The resistance gene LrE1was linked to thenine known SSR loci (Xgwm344, Xgwm146, Xwmc10, Xwmc70, Xwmc273, Xbarc50,and Xbarc32) on the7BL with genetic ranging from2.6cM to30.5cM. The closestSSR loci were Xgwm344with genetic distances of2.6cM.8. Five formally named leaf rust resistance genes Lr14a, Lr14b, Lr68, LrBi16and LrFunwere located on chromosome7BL. LrE1was different from Lr14a, Lr14b, Lr68,LrBi16and LrFun. LrE1might be a new leaf rust resistance gene.