疣粒野生稻抗白叶枯病新基因xa32(t)的鉴定及其分子标记定位

xa32（t）是从疣粒野生稻与栽培稻经体细胞杂交途径获得的新种质Y76中鉴定出的水稻抗白叶枯病新基因。将Y76与栽培稻＂大粒香＂回交构建F2群体,获得132个抗性稳定的株系。经致病菌株P6对该F2群体抗性鉴定,得到抗感株系数分别为32和100。随机选用覆盖水稻12条染色体的412对SSR引物对亲本和F2代群体进行多态性分析。筛选出8对多态性好的引物标记,连锁遗传分析发现位于xa32（t）同侧的RM8216和RM20A与其连锁,从而将xa32（t）定位在第12染色体长臂上,遗传距离为6.9cm和1.7cm。     

分子标记辅助甜瓜抗蔓枯病基因的聚合及品种改良

【目的】蔓枯病（gummy stem blight）是一种真菌性土传病害,是危害甜瓜生产的严重病害之一,其存在生理小种的分化,品种即使仅携带单个抗病基因,仍会导致甜瓜抗性逐步降低甚至丢失。建立甜瓜抗蔓枯病聚合育种的分子标记辅助选择体系,选育抗性高且不再分离的聚合抗源自交系和品质优良且高抗甜瓜蔓枯病的改良白皮脆品种（品系）,为甜瓜优质、抗病和高产育种提供一种简单、快捷的选择方法和重要的中间材料。【方法】利用5份甜瓜单一抗源材料PI140471、PI157082、PI511890、PI482398和PI420145两两杂交获得8份聚合抗源（082-471、082-890、082-398、145-471、145-082、145-890、145-398和890-398）。利用3个不同浓度的蔓枯病病菌孢子液（5×10⁵个/mL、5×10⁷个/mL、5×10⁹个/mL）对8份聚合抗源的F₁植株幼苗进行接种鉴定。结合春、秋两季的接种鉴定结果,筛选得到2份聚合后抗性显著提高的基因组合145-471和145-398。一方面,以145-471和145-398为材料,利用苗期梯度接种鉴定、分子标记辅助选择以及农艺性状观察,对其自交后代进行逐代筛选至F₇。另一方面,选用组合PI420145和PI140471以及PI420145和PI482398作为蔓枯病抗性基因的供体亲本,综合性状优良的感病甜瓜品种‘白皮脆’为抗性基因受体亲本。先分别单向回交5代,在单个基因回交转移时,利用分子标记检测结合农艺性状观察对回交后代进行筛选。当回交后代的遗传背景得到一定程度恢复后,再将2个方向的回交后代进行杂交,后自交3代稳定。【结果】聚合抗源对不同浓度的蔓枯病菌均表现为抗,而单一抗源对不同浓度蔓枯病菌表现出选择性抗性且抗性水平低于聚合抗源。SSR标记CMCT505和CMTA170a在PI140471和PI482398上可分别扩增出189 bp和121 bp的特异性片段,SCAR标记SGSB₁₈₀₀可以在PI420145上扩增出1 800 bp的特异性片段,而145-471（145-398）的聚合单株可以同时扩增出189 bp和1 800 bp（121 bp和1 800 bp）两条特异片段。聚合抗源145-471（或145-398）的自交F₇世代以及改良白皮脆BC₅F₄世代群体的分子标记鉴定结果显示,各单株已经成功聚合了Gsb-1和Gsb-6（或Gsb-4和Gsb-6）两个抗病基因,抗性不再有分离且农艺性状稳定一致。初步建立了甜瓜抗蔓枯病聚合育种的分子标记辅助选择体系,获得了两份表现高抗且抗性不再分离的聚合抗源自交系F₇和2个以优质品种‘白皮脆’为受体亲本的改良白皮脆BC₅F₄品种（系）。改良白皮脆BC₅F₄世代表现为高抗甜瓜蔓枯病,且在单果质量、果形指数、果实脆度、果肉质地、果肉厚度和可溶性固形物含量等农艺性状方面与白皮脆并无显著差异。【结论】创建的3个分子标记CMCT505、CMTA170a和SGSB₁₈₀₀对抗病基因Gsb-1、Gsb-4和Gsb-6的选择具有较高的准确性。初步建立了甜瓜抗蔓枯病聚合育种的分子标记辅助选择体系,为甜瓜优质、抗病和高产育种提供了一种简单、快捷的选择方法,将大大提高育种的效率。改良‘白皮脆’作为抗病育种的新材料,为甜瓜抗病品种的选育和抗病基因进一步聚合提供了材料。     

番茄第9号染色体上抗晚疫病基因的发掘及表达模式

为提供番茄晚疫病抗病育种候选基因,本研究以高抗晚疫病的CLN2037E自交系和感病5#自交系为实验材料,在前期使用分子标记将CLN2037E中存在的抗晚疫病基因定位在第9号染色体的基础上,利用晚疫病病菌诱导CLN2037E的cDNA文库、番茄基因组CDS数据库、本地Blast程序及实时荧光定量PCR技术,发掘与第9号染色体上EST最佳匹配的CDS以及对晚疫病病菌的响应模式。结果发掘出6条抗晚疫病的候选基因,其中Solyc09g097960、Solyc09g082810和Solyc09g065760在5#自交系和CLN2037E自交系中均响应晚疫病病菌,Solyc09g092030和Solyc09g090430在2个自交系中分别被抑制和不响应晚疫病病菌,Solyc09g008670STBZ的表达在5#自交系中被抑制,而在CLN2037E中被诱导。为验证该基因的功能,成功构建Solyc09g008670基因的过表达和VIGS(Virus Induced Gene Silencing)沉默载体。     

黄瓜耐冷性遗传分析与连锁标记筛选

黄瓜(Cucumis sativusL.)是典型的冷敏型植物。对黄瓜来说,冷害是生产上制约其丰产、优质的主要逆境因素之一。为了掌握黄瓜耐冷性遗传规律,加快黄瓜耐冷品种的选育,本研究选取黄瓜耐冷型品系0839和低温敏感型品系B52为亲本杂交得到F1和F2,进行苗期低温鉴定和遗传分析。供试亲本的耐冷性主要受一对显性单基因控制。结合BSA(群体分离分析)和SSR分子标记,获得了与黄瓜耐冷性主效基因连锁的SSR标记。通过F2群体分析,鉴定出与耐冷性基因连锁的分子标记SSR07248,该标记与耐冷性基因间的遗传距离为32.6cM。     

Identification of a Resistance Gene bls1 to Bacterial Leaf Streak in Wild Rice Oryza rufipogon Griff.

Bacterial leaf streak (BLS) of rice, caused by Xanthomonas oryzae pv. oryzicola (Xoc) is a worldwide destructive disease. Development of resistant varieties is considered to be one of the most effective and eco-friendly ways to control the disease. However, only a few genes/QTLs having resistance to BLS have been identified in rice until now. In the present study, we have identified and primarily mapped a BLS-resistance gene, bls1, from a rice line DP3, derived from the wild rice species Oryza rufipogon Griff. A BC₂F₂ (9311/DP3//9311) population was constructed to map BLS-resistance gene in the rice line DP3. The segregation of the resistant and susceptible plants in BC₂F₂ in 1:3 ratio (χ²=0.009, χ²_{0.05, 1}=3.84, P>0.05), suggested that a recessive gene confers BLS resistance in DP3. In bulked segregant analysis (BSA), two SSR markers RM8116 and RM584 were identified to be polymorphic in resistant and susceptible DNA bulks. For further mapping the resistance gene, six polymorphic markers around the target region were applied to analyze the genotypes of the BC₂F₂ individuals. As a result, the BLS-resistant gene, designated as bls1, was mapped in a 4.0-cM region flanked by RM587 and RM510 on chromosome 6.     

Genetic analysis and SSR mapping of stem rust resistance gene from wheat mutant D51

Wheat (Triticum aestivum L.) stem rust caused by Puccinia graminis f. sp. tritici is one of the main diseases of wheat worldwide. Wheat mutant line D51, which forms a highly susceptive cultivar ‘L6239’ to the three races notated and cultured with immature embryos, shows resistance to prevailing races 21C3CPH, 21C3CKH, and 21C3CTR of P. graminis f. sp. tritici in China. In this study, the number and the expression stages of the resistance genes in mutant D51 were studied using inoculation identification and microsatellite (SSR) marker analysis. Two F₁ populations from the crosses of D51 × L6239 (60 individuals) and D51 × Chinese Spring (60 individuals), their F₂ populations (185 and 175 individuals respectively) at the seedling stage, and one F₂ population derived from the cross of D51 × L6239 (194 individuals) at the adult stage were inoculated with pathogen race 21C3CPH to test for resistance. All F₁ individuals of the two crosses were immune to stem rust at both seedling and adult stages. The response pattern of the three F₂ populations showed that the R:S segregation ratio was 3:1, suggesting that the stem rust resistance of D51 is controlled by a single dominant gene, and is expressed during the entire growth period. The identification of the stem rust resistance by the F₃ progeny test confirmed the credibility of the F₂ population test. Segregating populations and small population analyses were used to identify chromosomal regions and molecular markers linked to the gene by the SSR marker method. A total of 675 SSR markers and 185 individuals of the D516L6239 F2 population were used to search genetically linked markers to the target gene. Using Mapmaker 3.0 and Map-draw with Kosambi’s function and other options set at default values, molecular mapping revealed that the gene was located on chromosome 5DS, linked with and flanked by two SSR markers, Xgwm190 and Xwmc150, at 18.58 and 21.33 cM, respectively. It has been reported that only one stem rust resistant gene, Sr30, is located on the wheat chromosome 5DL, and that it has no resistance to 34C2MKK and 34C2MFK, while the parent L6239 of mutant D51 has no resistance to 21C3CPH, 21C3CTK and 21C3CTR, but has resistance to 34C2MKK and 34C2MFK. The results above indicate that the gene identified in the study might be a novel resistance gene to stem rust, tentatively designated as SrD51. __________ Translated from Acta Agronomica Sinica, 2007, 33(8): 1262–1266 [译自: 作物学报]     

五叶草莓与凤梨草莓种间杂交F_1代的形态学及SSR标记鉴定

运用传统杂交方法,以五叶草莓为母本、凤梨草莓品种‘达赛莱克特’为父本进行远缘杂交,获得了11个F1代株系,利用形态学性状与分子标记相结合进行种间杂种鉴定。对父母本、F1代主要的植物学特征、生物学特性的调查分析结果表明,F1代在叶、花、果实等方面的很多性状不同于父母本,其中大部分介于双亲之间;植株长势明显强于父母本,具有明显的杂种优势。采用草莓属46对SSR引物进行分子鉴定,利用3对引物鉴定出种间杂种。形态学与SSR标记综合鉴定结果表明,全部F1代株系均为五叶草莓与凤梨草莓的种间杂种。     

Identification of disease resistances in wheat-<Emphasis Type="Italic">Leymus multicaulis</Emphasis> derivatives and characterization of <Emphasis Type="Italic">L. multicaulis</Emphasis> chromatin using microsatellite DNA markers

To identify resistance to Fusarium head blight (FHB), cereal yellow dwarf virus (CYDV), stem rust (Sr), and powdery mildew (Pm) in 24 common wheat (Triticum aestivum)-Leymus multicaulis addition/translocation lines that were developed cytogenetically and to verify the authenticity of these lines using microsatellite (SSR) DNA markers. Resistance to FHB was identified in the wheat-L. multicaulis addition lines, Line 9 and Line 26, which both contained L. multicaulis-specific fragments as shown by SSR markers. The translocation line, Trans 1, and the addition lines, Line 5 and Line 29, have resistance to stem rust (IT 0). Resistance to CYDV was evaluated based on virus titers measured by enzyme linked immunosorbent assay (ELISA). The addition line, Line 23, showed low virus titer (0.15), indicating resistance to CYDV. The segregation distribution of CYDV resistance in 98 F₂ plants of Line 23/CS showed a significant deviation from 3:1. Inoculation with a set of 14 differential Blumeria graminis f. sp. tritici (Bgt) isolates did not detect powdery mildew resistance in translocation line Trans 1, addition line Line 9 and the amphiploid of wheat-L. multicaulis. However, Line 26 exhibited the resistance response pattern of Kavkaz, which carries Pm8, indicating that Line 26 most likely has the powdery mildew resistance gene Pm8 inherited from its parent lines Feng Kang 7 or Feng Kang 10. Twelve SSR markers, distributed on different homeologous chromosome groups of wheat, which distinguished L. multicaulis addition/translocation chromosomes, were used to verify the presence of L. multicaulis chromatin in the putative wheat-L. multicaulis addition/translocation lines. Of the 24 addition/translocation lines investigated using the 12 polymorphic SSR markers, 18 wheat-L. multicaulis derivatives showed the expected L. multicaulis-specific fragments, indicating that all of these 18 addition/translocation lines would most likely have the introgressed L. multicaulis chromosome(s). Chromosomal rearrangements also were detected in some of the wheat-L. multicaulis introgression lines.     

鲜食甜玉米南方锈病抗性QTL定位分析

为挖掘新的抗南方锈病基因资源,本研究以甜玉米组合M5×M114的216个F2单株为遗传作图群体,应用BSA方法从500对SSR引物中筛选出2对在F2代抗病和感病DNA池间具有多态性的引物,分别位于4和9号染色体上;在4和9号染色体上重新设计100对SSR引物,构建了包含33个标记位点总长为241.2cM的连锁遗传图,各个标记间的平均距离为7.53cM。结合F2单株对南方锈病的抗性表现,用复合区间作图法在4和9号染色体上共检测到7个显著的南方锈病抗性QTLs,其中:4个QTLs位于4号染色体上,可解释12.1%、7.8%、18.2%和14.9%表型变异;3个位于9号染色体上,分别解释17.0%、13.3%与19.2%的表型变异。研究结果可为抗南方锈病的精细定位、主效基因克隆和抗南方锈病鲜食甜玉米品种选育提供理论依据。     

Molecular mapping of stripe rust resistance gene YrH9017 in wheat-Psathyrostachys huashanica introgression line H9017-14-16-5-3

Several new stripe rust pathogen races emerged in the wheat growing regions of China in recent years. These races were virulent to most of the designated wheat seedling resistance genes. Thus, it is necessary and worthwhile to identify new valuable resistant materials for the sake of diversifying resistant sources, pyramiding different resistance genes and achieving durable resistance. Here, we identified the resistance gene, temporarily designated as YrH9017, in wheat-Psathyrostachys huashanica introgression line H9017-14-16-5-3. A total of 146 F₂ plants and their derived F_2:3 families in a cross of Mingxian 169 and H9017-14-16-5-3 were used to evaluate seedling stripe rust response and as a mapping population. Finally, we constructed a genetic map including eight simple sequence repeat (SSR) markers and expressed sequence tag (EST) markers. YrH9017 was located on the long arm of chromosome 2A and closely linked with two EST-sequence tagged site (EST-STS) markers BG604577 and BE471201 at 1.3 and 1.8 cM distance, respectively. The two closest markers could be used for marker-assisted selection of YrH9017 in breeding.     

Inheritance and Molecular Mapping of Stripe Rust Resistance Gene Yr88375 in Chinese Wheat Line Zhongliang 88375

Stripe rust is one of the most important diseases of wheat worldwide. Inheritance of stripe rust resistance and mapping of resistance gene with simple sequence repeat （SSR） markers are studied to formulate efficient strategies for breeding cultivars resistant to stripe rust. Zhongliang 88375, a common wheat line, is highly resistant to all three rusts of wheat in China. The gene conferring rust disease was deduced originating from Elytrigia intermedium. Genetic analysis of Zhongliang 88375 indicated that the resistance to PST race CYR31 was controlled by a single dominant gene, temporarily designated as Yr88375. To molecular map Yr88375, a F2 segregating population consisting of 163 individuals was constructed on the basis of the hybridization between Zhongliang 88375 and a susceptible wheat line Mingxian 169; 320 SSR primer pairs were used for analyzing the genetic linkage relation. Six SSR markers, Xgwm335, Xwmc289, Xwmc810, Xgdmll6, Xbarc59, and Xwmc783, are linked to Yr88375 as they were all located on chromosome 5BL Yr88375 was also located on that chromosome arm, closely linked to Xgdmll6 and Xwmc810 with genetic distances of 3.1 and 3.9 cM, respectively. The furthest marker Xwmc783 was 13.5 cM to Yr88375. Hence, pedigree analysis of Zhongliang 88375 combined with SSR markers supports the conclusion that the highly resistance gene Yr88375 derived from Elytrigia intermedium is a novel gene for resistance to stripe rust in wheat. It could play an important role in wheat breeding programs for stripe rust resistance.     

Molecular Mapping of Two Novel Stripe Rust Resistant Genes YrTp1 and YrTp2 in A-3 Derived from Triticum aestivum × Thinopyrum ponticum

Loss of variety resistance to stripe rust (Puccinia striiformis Westend f. sp.tritici) is an important factor causing massive periodical epidemic of rust in wheat production. Creation and development of new races of rust pathogen have led to serious crisis of resistance loss in widely planted varieties. This has quickened the search for new resistance resources. Molecular marker could facilitate the identification of the location of novel genes. A line A-3 with high resistance (immune) to currently epidemic yellow rust races (CY29, 31, 32) was screened out in offspring of Triticum aestivum × Thinopyrum ponticum. Segregation in F₂ and BC₁ populations indicated that the resistance was controlled by two independent genes: one dominant and one recessive. SSR markers were employed to map the two resistant genes in the F₂ and BC₁ populations. A marker WMC477-_167bp located on 2BS was linked to the dominant gene with genetic distance of 0.4 cM. Another marker WMC364-_{208 bp} located on 7BS was linked to the recessive-resistant gene with genetic distance of 5.8 cM. The two genes identified in this paper might be two novel stripe rust resistant genes, which were temporarily designated as YrTp1 and YrTp2, respectively. The tightly linking markers facilitate transfer of the two resistant genes into the new varieties to control epidemic of yellow rust.     

中梁12小麦抗条锈病基因遗传分析与SSR分子定位

中梁12具有抗逆性强、适应性广、抗条锈性强等许多优良的生物学特性。为明确其抗条锈性及遗传规律,利用当前流行的中国条锈菌小种CYR30对抗病品种中梁12与感病品种铭贤169及其杂交后代代F1、F2、F3和BC1代进行苗期抗条锈性遗传分析,并对其抗条锈基因进行SSR分子标记。结果表明,中梁12对CYR30小种具有良好的抗性,由1对显性基因控制,暂命名为YrZh12。该基因与位于小麦7AL染色体上的4个SSR位点Xwmc695、Xcfd20、Xbarc121和Xbarc49连锁,其中最近的侧翼位点为Xcfd20和Xbarc121,其遗传距离分别是3.1cM和4.9cM。系谱分析YrZh12基因可能来自抗引655,由于7AL染色体上没有其他抗条锈病基因,YrZh12可能是一个抗条锈病的新基因。     

枸杞种间杂交F_1群体的SSR鉴定及遗传分析

以黄果枸杞(Lyciumbararumvar.auranticarpum,用P_1表示)为父本,北方枸杞(L.chinensevar.potaninii,用P_2表示)为母本,杂交获得F_1群体91个单株。从66对SSR引物中筛选出具有双亲互补型杂合位点6对引物,对91个F_1单株进行杂种鉴定和遗传变异分析。结果表明:6对引物在91个单株进行扩增检测结果中有83个单株在6个SSR位点上表现为双亲互补型杂合位点,可被认定为真杂种,杂种率为91.2%,另外8个单株出现异常SSR基因型,需要结合细胞学进一步验证。UPGMA聚类分析结果显示:在遗传距离为0.712处,83个F_1单株被划分为2大类,第Ⅰ大类包括38个F_1单株,占45.8%,第二大类包括45个F_1单株,占54.2%。杂交后代遗传变异大,遗传多样性丰富。     

重庆番茄晚疫病抗病性鉴定与遗传分析

比较了重庆晚疫病田间自然发病鉴定和室内人工接种鉴定结果的差异,进行了晚疫病抗性材料CLn2037B对晚疫菌生理小种T1的配合力、遗传参数及后代分离遗传规律分析.结果表明:①田间自然发病鉴定与室内人工接种鉴定结果一致,在重庆春季露地进行晚疫病田间自然发病鉴定是可行的;②番茄抗晚疫病材料CLN2037B对生理小种T1的抗性以基因的加性效应为主,遗传力较高,抗性遗传中不存在细胞质基因效应,抗性表现为单基因不完全显性.     

小麦抗白粉病种质“N9134”的抗性遗传分析

抗性种质"N9134"含有野生二粒小麦(资源编号:AS846)的抗白粉病基因。为了研究其白粉病抗性基因的遗传规律,用感病品种阿勃、中国春、陕160、陕优225与该种质正反交,结果F1白粉病感染0～1级,F2白粉病抗感比例为3∶1;以小麦缺体系与其杂交,F1白粉病感染0～1级,F2白粉病抗感比例除"5B"偏离3∶1外,其余均为3∶1。表明N9134的白粉病抗性由1对完全显性基因控制,位于"5B"染色体上。     

分子标记技术在马铃薯晚疫病研究中的应用

马铃薯是世界上重要的粮食作物之一,晚疫病则是当今危害马铃薯生产最为严重的病害。重点介绍了四种常用的分子标记技术RFLP、RAPD、AFLP和SSR,以及国内外利用这些标记技术在马铃薯晚疫病研究中的应用。分析了马铃薯晚疫病菌的遗传多样性、菌株抗药性、有性杂交后代的遗传分离以及抗病种质资源的遗传多样性,介绍了遗传图谱的构建、抗性基因及与晚疫病抗性相关的QTL定位、体细胞杂种及回交后代的晚疫病抗性检测。这些对今后中国学者开展相关领域的研究具有重要的借鉴意义。     

小麦品种辽春10抗叶锈病基因LrLC10的比较基因组学定位

为明确小麦品种辽春10对叶锈菌小种PHT抗病的遗传基础,利用感病小麦材料87-1与抗病小麦材料辽春10构建的F_(2:3)群体,对其进行成株期抗病性鉴定和遗传分析。结果表明,辽春10中含有1个显性抗叶锈病基因,暂命名为LrLC10。利用BSA法和比较基因组学策略对该抗病基因进行分子标记分析,将LrLC10定位于小麦2BS染色体上。共构建了含有8个分子标记的LrLC10基因的连锁图,其中:CAUT253位于LrLC10的远着丝粒侧,距离为0.1cM;CAUT163和CAUT131与LrLC10共分离;CAUT239位于LrLC10的近着丝粒侧,遗传距离为0.5cM。     

Identification and Molecular Mapping of the RsDmR Locus Conferring Resistance to Downy Mildew at Seedling Stage in Radish (Raphanus sativus L.)

Downy mildew (DM), caused by the fungus Peronospora parasitica, is a destructive disease of radish (Raphanus sativus L.) worldwide. Host resistance has been considered as an attractive and environmentally friendly approach to control the disease. However, the genetic mechanisms of resistance in radish to the pathogen remain unknown. To determine the inheritance of resistance to DM, F₁, F₂ and BC₁F₁ populations derived from reciprocal crosses between a resistant line NAU-dhp08 and a susceptible line NAU-qtbjq-06 were evaluated for their responses to DM at seedling stage. All F₁ hybrid plants showed high resistance to DM and maternal effect was not detected. The segregation for resistant to susceptible individuals statistically fitted a 3:1 ratio in two F₂ populations (F_2(SR) and F_2(RS)), and 1:1 ratio in two BC₁F₁ populations, indicating that resistance to DM at seedling stage in radish was controlled by a single dominant locus designated as RsDmR. A total of 1972 primer pairs (1036 SRAP, 628 RAPD, 126 RGA, 110 EST-SSR and 72 ISSR) were screened, and 36 were polymorphic between the resistant and susceptible bulks, and consequently used for genotyping individuals in the F₂ population. Three markers (Em9/ga24₃₇₀, NAUISSR826₇₀₀ and Me7/em10₄₀₀) linked to the RsDmR locus within a 10.0 cM distance were identified using bulked segregant analysis (BSA). The SRAP marker Em9/ga24₃₇₀ was the most tightly linked one with a distance of 2.3 cM to RsDmR. These markers tightly linked to the RsDmR locus would facilitate marker-assisted selection and resistance gene pyramiding in radish breeding programs.     

Identification of <Emphasis Type="Italic">Lr24</Emphasis> with targeted region amplified polymorphism (TRAP) analysis in wheat

This research is aimed at developing TRAP markers, as a probe for library screening, closely linked to or co-segregated with Lr24. Ninety TRAP primer pairs were used to test the resistant and susceptible parents, as well as the resistant bulk and the susceptible bulk in our study. The polymorphic TRAP primers of TcLr24 were employed to genotype the F₂ population from TcLr24×Thatcher subsequently. Ten of 90 TRAP primer pairs displayed polymorphism between TcLr24 and Thatcher, accounting for 11.11%. A further study found that primer ARBI1/RGA-2F generated a 161 bp fragment presented only in the resistance plants of F₂ population. Forty-five other wheat leaf rust resistant NILs and 30 diploid materials of wheat were also tested to detect the specificity of the primer. This specific band was amplified in TcLr19, TcLr29, TcLr38, TcLr42 and TcLr44, but absented in all the 30 diploid materials. It was concluded that this marker ARBI1/RGA-2F was closely linked to Lr24, which could be used to detect Lr24 in the F₂ population of TcLr24×Thatcher, and be further used as a probe for cDNA and BAC library screening of TcLr24.