Genetic studies of leaf and stem rust resistance in six accessions of Triticum turgidum var. dicoccoides.

Six accessions of Triticum turgidum var. dicoccoides L. (4x, AABB) of diverse origin were tested with 10 races of leaf rust (Puccinia recondita f.sp. tritici Rob. ex Desm.) and 10 races of stem rust (P. graminis f.sp. tritici Eriks. &Henn.). Their infection type patterns were all different from those of lines carrying the Lr or Sr genes on the A or B genome chromosomes with the same races. The unique reaction patterns are probably controlled by genes for leaf rust or stem rust resistance that have not been previously identified. The six dicoccoides accessions were crossed with leaf rust susceptible RL6089 durum wheat and stem rust susceptible 'Kubanka' durum wheat to determine the inheritance of resistance. They were also crossed in diallel to see whether they carried common genes. Seedlings of F1, F2, and BC1F2 generations from the crosses of the dicoccoides accessions with RL6089 were tested with leaf rust race 15 and those from the crosses with 'Kubanka' were tested with stem rust race 15B-1. The F2 populations from the diallel crosses were tested with both races. The data from the crosses with the susceptible durum wheats showed that resistance to leaf rust race 15 and stem rust race 15B-1 in each of the six dicoccoides accessions is conferred by a single dominant or partially dominant gene. In the diallel crosses, the dominance of resistance appeared to be affected by different genetic backgrounds. With one exception, the accessions carry different resistance genes: CI7181 and PI 197483 carry a common gene for resistance to leaf rust race 15. Thus, wild emmer wheat has considerable genetic diversity for rust resistance and is a promising source of new rust resistance genes for cultivated wheats.     

Development and validation of molecular markers linked to an Aegilops umbellulata-derived leaf-rust-resistance gene, Lr9, for marker-assisted selection in bread wheat.

An Aegilops umbellulata-derived leaf-rust-resistance gene, Lr9, was tagged with 3 random amplified polymorphic DNA (RAPD) markers, which mapped within 1.8 cM of gene Lr9 located on chromosome 6BL of wheat. The markers were identified in an F2 population segregating for leaf-rust resistance, which was generated from a cross between 2 near-isogenic lines that differed in the alien gene Lr9 in a widely adopted agronomic background of cultivar 'HD 2329'. Disease phenotyping was done in controlled environmental conditions by inoculating the population with the most virulent pathotype, 121 R63-1 of Puccinia triticina. One RAPD marker, S5550, located at a distance of 0.8+/-0.008 cM from the Lr9 locus, was converted to sequence-characterized amplified region (SCAR) marker SCS5550. The SCAR marker was validated for its specificity to gene Lr9 against 44 of the 50 known Lr genes and 10 wheat cultivars possessing the gene Lr9. Marker SCS5550 was used with another SCAR marker, SCS73719, previously identified as being linked to gene Lr24 on a segregating F2 population to select for genes Lr9 and Lr24, respectively, demonstrating the utility of the 2 markers in marker-assisted gene pyramiding for leaf-rust resistance in wheat.     

Genetics of adult plant stripe rust resistance in CSP44, a selection from Australian wheat

Wheat line CSP44, a selection from an Australian bread wheat cultivar Condor, has shown resistance to stripe rust in India since the last twenty years. Seedlings and adult plants of CSP44 showed susceptible infection types against stripe rust race 46S119 but displayed average terminal disease severity of 2.67 on adult plants against this race as compared to 70.33 of susceptible Indian cultivar, WL711. This suggests the presence of nonhypersensitive adult plant stripe rust resistance in the line CSP44. The evaluation of F₁, F₂ and F₃ generations and F₆ SSD families from the cross of CSP44 with susceptible wheat cultivar WL711 for stripe rust severity indicated that the resistance in CSP44 is based on two genes showing additive effect. One of these two genes isYr18 and the second gene is not yet described.     

Inheritance of partial resistance to powdery mildew in spring wheat

Summary Four spring wheat (Triticum aestivum L.) cultivars exhibiting partial resistance to powdery mildew induced by Erysiphe graminis f.sp. tritici were crossed to a common susceptible cultivar to study the inheritance of resistance. The genetic parameters contributing to resistance were estimated by generation means analyses. Additive gene action was the most important genetic component of variation among generation means in all four crosses. Additive by additive effects were significant in one cross and both additive by additive and additive by dominance effects were significant in another. Dominance effects were not significant. The F2/F3 correlations in three crosses ranged from 0.27 to 0.43. Three additional crosses among resistant cultivars were employed to study the effectiveness of selection in improving resistance. By selecting the most resistant plants from the F2 and evaluating the progenies in the F4, increases in resistance ranging from 21% to 31% were obtained. In all crosses, there was transgressive segregation in both directions indicating that the genes conferring resistance to these cultivars differ and exhibit additive effects.     

Identification of efficient leaf-rust resistance genes in wheat (Triticum aestivum) using STS markers

Molecular STS markers J13, Gb, and J09 were used for screening wheat (Triticum aestivum L.) accessions previously found to possess leaf-rust resistance genes according to test crosses or phytopathological tests. Specific amplicons were detected in all accessions assumed to possess the Lr9 gene, in nine of ten accessions with the conjectured Lr19 gene, and in 13 of 29 accessions with the conjectured Lr24 gene. Application of STS markers to identification of accessions possessing efficient leaf-rust resistance genes is discussed.     

Transfer of leaf rust and stem rust resistance genes from Triticum triaristatum to durum and bread wheats and their molecular cytogenetic localization.

Six accessions of Triticum triaristatum (Willd) Godr. &Gren. (syn. Aegilops triaristata) (6x, UUMMUnUn), having good resistance to both leaf rust (Puccinia recondita f.sp. tritici Rob. ex Desm) races and stem rust (P. graminis f.sp. tritici Eriks. &Henn.) races, were successfully crossed with both susceptible durum wheats (T. turgidum var. durum L., 2n = 28, AABB) and bread wheats (T. aestivum, 2n = 42, AABBDD). In some crosses, embryo rescue was necessary. The T. triaristatum resistance was expressed in all F1 hybrids. Backcrossing of the F1 hybrids to their wheat parents to produce BC1F1 plants was more difficult (seed set 0-7.14%) than to produce F1 hybrids (seed set 12.50-78.33%). The low female fertility of the F1 hybrids was due to low chromosome pairing. Only gametes with complete or nearly complete genomes from the F1 hybrids were viable. In BC2F4 populations from the cross MP/Ata2//2*MP, monosomic or disomic addition lines (2n = 21 II + 1 I or 22 II) with resistance to leaf rust race 15 (IT 1) were selected. In BC2F2 populations from the crosses CS/Ata4//2*MP and MP/Ata4//2*MP, monosomic or disomic addition lines with resistance to either leaf rust race 15 or stem rust race 15B-1 (both IT 1) were selected. Rust tests and cytology on the progeny of the disomic addition lines confirmed that the genes for rust resistance were located on the added T. triaristatum chromosomes. The homoeologous groups of the T. triaristatum chromosomes in the addition lines from the crosses MP/Ata2//2*MP, CS/Ata4//2*MP, and MP/Ata4//2*MP were determined to be 5, 2, and 7, respectively, through the detecting of RFLPs among genomes using a set of homoeologous group specific wheat cDNA probes. The addition lines with resistance to leaf rust race 15 from the crosses MP/Ata2//2*MP and CS/Ata4//2*MP were resistant to another nine races of leaf rust and the addition line with resistance to stem rust race 15B-1 from the cross MP/Ata4//2*MP was resistant to another nine races of stem rust as were their T. triaristatum parents. Since such genes provide resistance against a wide spectrum of rust races they should be very valuable in wheat breeding for rust resistance.     

Identification of effective leaf-rust resistance genes in wheat (Triticum aestivum) using STS markers

Molecular STS markers J13, Gb, and J09 were used for screening wheat (Triticum aestivum L.) accessions previously found to possess leaf-rust resistance genes according to test crosses or phytopathological tests. Specific amplification products were detected in all accessions assumed to possess the Lr9 gene, in nine of ten accessions with the conjectured Lr19 gene, and in 13 of 29 accessions with the conjectured Lr24 gene. Application of STS markers to identification of accessions possessing effective leaf-rust resistance genes is discussed.     

15个小麦农家品种抗叶锈基因分析

本研究旨在明确小麦农家品种中可能含有的抗叶锈病基因,为抗源的选择和利用提供理论依据。以15个小麦农家品种、感病对照品种郑州5389和36个含有已知抗叶锈病基因的载体品种为材料,苗期接种19个具有鉴别力的叶锈菌生理小种进行基因推导,同时利用12个与抗叶锈病基因紧密连锁的分子标记进行分析。为明确其成株期抗性,分别于2016-2017年和2017-2018年在河北保定对小麦农家品种、感病对照品种郑州5389与慢锈品种SAAR进行田间接种,调查并记录田间严重度及普遍率。基因推导和分子标记检测结果显示,在15个小麦农家品种中共检测到7个抗叶锈病基因,其中部分品种还有多个抗性基因,如红狗豆含有Lr1和Lr46;黄花麦含有Lr13和Lr34;大白麦含有Lr14b和Lr26;洋麦含有Lr37和Lr46;成都光头含有Lr34和Lr46;墨脱麦和西山扁穗含有Lr26和Lr46。部分品种含有1个成株期慢叶锈病抗性基因,如同家坝小麦、武都白茧儿、边巴春麦-6、白花麦含有Lr34;红抢麦、白扁穗和白火麦含有Lr46。这些携带有效抗叶锈病基因的农家品种,可为小麦抗叶锈病育种提供抗源。     

Inheritance of resistance to Fusarium head blight in three European winter wheat populations

Fusarium head blight (FHB) resistance is of particular importance in wheat breeding programmes due to the detrimental effects of this fungal disease on human and animal health, yield and grain quality. Segregation for FHB resistance in three European winter wheat populations enabled the identification of resistance loci in well-adapted germplasm. Populations obtained from crosses of resistant cultivars Apache, History and Romanus with susceptible semi-dwarfs Biscay, Rubens and Pirat, respectively, were mapped and analysed to identify quantitative trait loci (QTL) for FHB severity, ear emergence time and plant height. The results of the present study together with previous studies in UK winter wheat indicated that the semi-dwarfing allele Rht-D1b seems to be the major source for FHB susceptibility in European winter wheat. The high resistance level of the cultivars Romanus and History was conditioned by several minor resistance QTL interacting with the environment and the absence of Rht-D1b. In contrast, the semi-dwarf parents contributed resistance alleles of major effects apparently compensating the negative effects of Rht-D1b on FHB reaction. The moderately resistant cultivar Apache contributed a major QTL on chromosome 6A in a genome region previously shown to carry resistance loci to FHB. A total of 18 genomic regions were repeatedly associated with FHB resistance. The results indicate that common resistance-associated genes or genomic regions are present in European winter wheats.     

Genetics of durable resistance to leaf rust and stripe rust of an Indian wheat cultivar HD2009

The Indian bread wheat cultivar HD2009 has maintained its partial resistance to leaf rust and stripe rust in India since its release in 1976. To examine the nature, number and mode of inheritance of its genes for partial leaf rust and stripe rust resistance, this cultivar was crossed with cultivar WL711, which is susceptible to leaf rust and stripe rust. The F1, F2, F3 and F5 generations from this cross were assessed separately for adult plant disease severity under artificial epidemic of race 77-5 of leaf rust and race 46S119 of stripe rust. Segregation for rust reaction in the F2, F3 and F5 generations indicated that resistance to each of these rust diseases is based on 2 genes, each with additive effects. Although the leaf rust resistance of HD2009 is similar in expression to that conferred by the gene Lr34, but unlike the wheats carrying this gene, cultivar HD2009 did not show leaf tip necrosis, a morphological marker believed to be tightly linked to the leaf rust resistance gene Lr34. Thus, the non-hypersensitive resistance of HD2009 was ascribed to genes other than Lr34.     

Leaf rust (Puccinia triticina) resistance in wheat (Triticum aestivum) cultivars grown in Northern Europe 1992-2002

Diversity of resistance to leaf rust caused by Puccinia triticina can be enhanced in wheat (Triticum aestivum) cultivars through a better knowledge of resistance genes that are present in important cultivars and germplasm. Multi-pathotype tests on 84 wheat cultivars grown in Denmark, Finland, Norway and Sweden during 1992-2002 and 39 differential testers enabled the postulation of nine known genes for seedling resistance to leaf rust. Genes Lr1, Lr2a, Lr3, Lr10, Lr13, Lr14a, Lr17, Lr23 and Lr26 were found singly or in combination in 47 of the cultivars (55.9%). The most frequently occurring genes in cultivars grown in Sweden were Lr13 (20.4%), Lr14a (14.8%) and Lr26 (14.8%). Lr14a was the most common gene in cultivars grown in Norway (18.7%), Lr13 in Denmark (35.5%) and Lr10 in Finland (20.0%). Although 28 cultivars (33.3%) exhibited a response pattern that could not be assigned to resistance genes or combinations present in the tester lines, several pathotypes carried virulence and hence these genes or combinations are of limited use. Nine cultivars (10.7%) lacked detectable seedling resistance. One cultivar was resistant to all pathotypes used in the study.     

Rust resistance in Triticum cylindricum Ces. (4x, CCDD) and its transfer into durum and hexaploid wheats.

In order to counteract the effects of the mutant genes in races of leaf rust (Puccinia recondita f.sp. tritici Rob. ex Desm.) and stem rust (P. graminis f.sp. tritici Eriks. &Henn.) in wheat, exploration of new resistance genes in wheat relatives is necessary. Three accessions of Triticum cylindricum Ces. (4x, CCDD), Acy1, Acy9, and Acy11, were tested with 10 races each of leaf rust and stem rust. They were resistant to all races tested. Viable F1 plants were produced from the crosses of the T. cylindricum accessions as males with susceptible MP and Chinese Spring ph1b hexaploid wheats (T. aestivum, 6x, AABBDD), but not with susceptible Kubanka durum wheat (T. turgidum var. durum, 4x, AABB), even with embryo rescue. In these crosses the D genome of hexaploid wheat may play a critical role in eliminating the barriers for species isolation during hybrid seed development. The T. cylindricum rust resistance was expressed in the F1 hybrids with hexaploid wheat. However, only the cross MP/Acy1 was successfully backcrossed to another susceptible hexaploid wheat, LMPG-6. In the BC2F2 of the cross MP/Acy1//LMPG-6/3/MP, monosomic or disomic addition lines with resistance to either leaf rust race 15 (infection types (IT) 1=, 1, or 1+; addition line 1) or stem rust race 15B-1 (IT 1 or 1+; addition line 2) were selected. Rust tests and examination of chromosome pairing of the F1 hybrids and the progeny of the disomic addition lines confirmed that the genes for rust resistance were located on the added T. cylindricum C-genome chromosomes rather than on the D-genome chromosomes. The T. cylindricum chromosome in addition line 2 was determined to be chromosome 4C through the detection of RFLPs among the genomes using a set of homoeologous group-specific wheat cDNA probes. Addition line 1 was resistant to the 10 races of leaf rust and addition line 2 was resistant to the 10 races of stem rust, as was the T. cylindricum parent. The added C-genome chromosomes occasionally paired with hexaploid wheat chromosomes. Translocation lines with rust resistance (2n = 21 II) may be obtained in the self-pollinated progeny of the addition lines through spontaneous recombination of the C-genome chromosomes and wheat chromosomes. Such translocation lines with resistance against a wide spectrum of rust races should be potentially valuable in breeding wheat for rust resistance.     

Inheritance of resistance to Fusarium graminearum in wheat

To study the inheritance of resistance in wheat to Fusarium graminearum, six resistant cultivars from China were crossed to two susceptible cultivars. The parents and their progenies were evaluated in the greenhouse for resistance to the spread of scab within a spike. A central floret was inoculated by injecting a droplet of inoculum at the time of anthesis. Inoculated plants were kept in a moist chamber for three subsequent nights. The proportion of scabbed spikelets was recorded six-times from 3-days to 21-days after inoculation, and the area under the disease progress curve (AUDPC) was calculated from these proportions. One to three genes, depending on the cultivar, conditioned resistance to scab as reflected by the AUDPC. A simple additive-dominance effect model fitted the segregation data for 8 of the 11 crosses. Dominance and epistatic effects were significant in a few crosses. These effects increased resistance in some crosses but decreased resistance in others. However, relative to additive effects, dominant and epistatic effects accounted for only a small portion of the genetic effects in the populations evaluated. The importance of additive effects means that it should be possible to accumulate different genes to enhance resistance to scab in wheat. Received: 15 December 1998 / Accepted: 17 June 1999     

Assessment of genetic diversity of wheat genotypes by resistance gene analog-EST markers

Resistance gene analog-expressed sequence tag (RGA-EST)-based markers have been used for variety discrimination and studies of genetic diversity in wheat. Our aim is to increase the competitiveness of public wheat breeding programs through intensive use of modern selection technologies, mainly marker-assisted selection. The genetic diversity of 77 wheat nucleotide binding site (NBS)-containing RGA-ESTs was assessed. Resistant and susceptible bread wheat (Triticum aestivum) genotypes were used as sources of DNA for PCR amplifications. In our previous studies, the F? individuals derived from the combinations PI178383 x Harmankaya99, Izgi2001 x ES14, and Sonmez2001 x Aytin98 were evaluated for yellow rust resistance at both seedling and adult stages to identify DNA markers. We have now examined the genetic variability among the resistant and susceptible Turkish wheat cultivars for yellow rust disease and the mean genetic distance between the cultivars. The highest similarity was 0.500 between Harmankaya99 and Sonmez2001. The lowest similarity was 0.286 between Aytin98, PI178383 and Aytin98, ES14. A relatively high level (49.5%) of polymorphism was observed with 77 RGA-EST primers across the six wheat genotypes, despite the fact that all of them were local cultivars from geographically close locations. RGA-EST sequences were compared by BlastX algorithms for amino acid sequences to determine the polymorphic categories among the combinations. BlastX analyses of six RGA-ESTs that gave polymorphic patterns for all combinations were NBS-LRR class RGA, NB-ARC domain containing protein, NBS-type resistance protein RGC5, NBS-LRR-S/ TPK stem rust resistance protein, and putative MLA1 proteins, while 38 RGA-EST gave a monomorphic pattern.     

Gene action for adult-plant resistance to powdery mildew in wheat.

Gene action for adult-plant resistance to powdery mildew was studied using generation mean analyses of parents and of F1, F2, and backcross populations derived from a diallel cross of one susceptible and three adult-plant resistant wheat cultivars. Joint scaling tests showed that an additive-dominance model was sufficient to explain the variability in the expression of adult-plant resistance in one cross, while digenic epistasis was involved in the other five crosses. Additive gene effects were predominant; however, dominance was significant in four crosses, additive x additive interaction was significant in three crosses, additive x dominance interaction was significant in three crosses, and dominance x dominance interaction was significant in one cross. Therefore, selection for adult-plant resistance would likely be most effective in advanced generations derived from crosses among the adult-plant resistant cultivars Redcoat, Houser, and Massey.     

Genetic mapping of adult plant leaf rust resistance genes Lr48 and Lr49 in common wheat

Hypersensitive adult plant resistance genes Lr48 and Lr49 were named based on their genetic independence of the known adult plant resistance genes. This study was planned to determine genomic locations of these genes. Recombinant inbred line populations derived from crosses involving CSP44 and VL404, sources of Lr48 and Lr49, respectively, and the susceptible parent WL711, were used to determine the genomic locations of these genes. Bulked segregant analyses were performed using multiplex-ready PCR technology. Lr48 in genotype CSP44 was mapped on chromosome arm 2BS flanked by marker loci Xgwm429b (6.1 cM) and Xbarc7 (7.3 cM) distally and proximally, respectively. Leaf rust resistance gene Lr13, carried by the alternate parent WL711, was proximal to Lr48 and was flanked by Xksm58 (5.1 cM) and Xstm773-2 (8.7 cM). Lr49 was flanked by Xbarc163 (8.1 cM) and Xwmc349 (10.1 cM) on chromosome arm 4BL. The likely presence of the durable leaf rust resistance gene Lr34 in both CSP44 and VL404 was confirmed using the tightly linked marker csLV34. Near-isogenic lines for Lr48 and Lr49 were developed in cultivar Lal Bahadur. Genotypes combining Lr13 and/or Lr34 with Lr48 or Lr49 were identified as potential donor sources for cultivar development programs.     

水稻品种对美国稻瘟病小种IB-33、IB-45和IE-1的抗性遗传

1995年10月至1997年11月,在美国阿肯色大学水稻研究推广中心,用水稻品种LA110和Jasmine-85与水稻品种Teqing、Katy、Mars、LaGrue和Newbonnet进行不完全双列杂交,对其杂交后代和亲本用美国3个主要稻瘟病菌小种(以下简称小种)IB-33、IB-45和IE-1进行接种鉴定和遗传分析研究.结果表明:亲本LA110、Jasmine-85、Teqing抗所有3个小种.Katy抗小种IB-45和IE-1,感小种IB-33.Mars抗小种IE-1,感小种IB-33和IB-45.LaGrue感所有3个小种.Newbonnet抗小种IB-45,感小种IB-33和IE-1.所有抗病亲本的抗病基因,其F1分别对相应小种呈现显性抗病性.抗病亲本杂交,LA110与Jasmine-85对小种IB-33,LA110与Teqing、Jasmine-85对小种IE-1,及Jasmine-85与Teqing对小种IE-1,是等位的抗病基因.LA110与Teqing对小种IB-33,及Jasmine-85与Teqing对小种IB-33,分别存在三对独立遗传的显性抗病基因.LA110与Teqing、Katy、Newbonnet、Jasmine-85对小种IB-45,Jasmine-85与Teqing、Katy、Newbonnet对小种IB-45,LA110与Katy、Mars对小种IE-1,Jasmine-85与Katy、Mars对小种IE-1,分别存在两对独立遗传的显性抗性基因.抗病亲本LA110或Jasmine-85与感病亲本Mars对小种IB-33,抗病亲本LA110与感病亲本Mars对小种IB-45,具有两对显性互补抗病基因,当两对显性抗病基因同时存在时,表现出抗性.抗病亲本LA110或Jasmine-85与感病亲本Katy、LaGrue、Newbonnet对小种IB-33,抗病亲本LA110与感病亲本LaGrue对小种IB-45,抗病亲本Jasmine-85与感病亲本Mars、LaGrue对小种IB-45,抗病亲本LA110或Jasmine-85与感病亲本LaGrue、Newbonnet对小种IE-1,分别存在一对显性抗病基因.两个亲本正、反交的遗传表现一致.本文也讨论了LA110、Teqing和Jasmine-85三个抗病品种在美国水稻抗病育种中利用的可能性.     

Mapping of quantitative trait loci for field resistance to Fusarium head blight in an European winter wheat

Fusarium head blight (FHB) caused by Fusarium culmorum is an economically important disease of wheat that may cause serious yield and quality losses under favorable climate conditions. The development of disease-resistant cultivars is the most effective control strategy. Worldwide, there is heavy reliance on the resistance pool originating from Asian wheats, but excellent field resistance has also been observed among European winter wheats. The objective of this study was to map and characterize quantitative traits loci (QTL) of resistance to FHB among European winter wheats. A population of 194 recombinant inbred lines (RILs) was genotyped from a cross between two winter wheats Renan (resistant)/Récital (susceptible) with microsatellites, AFLP and RFLP markers. RILs were assessed under field conditions For 3 years in one location. Nine QTLs were detected, and together they explained 30-45% of the variance, depending on the year. Three of the QTLs were stable over the 3 years. One stable QTL, QFhs.inra.2b, was mapped to chromosome 2B and two QTLs QFhs.inra.5a2 and QFhs.inra5a3, to chromosome 5A; each of these QTLs explained 6.9-18.6% of the variance. Other QTLs were identified on chromosome 2A, 3A, 3B, 5D, and 6D, but these had a smaller effect on FHB resistance. One of the two QTLs on chromosome 5A was linked to gene B1 controlling the presence of awns. Overlapping QTLs for FHB resistance were those for plant height or/and flowering time. Our results confirm that wheat chromosomes 2A, 3A, 3B, and 5A carry FHB resistance genes, and new resistance factors were identified on chromosome arms 2BS and 5AL. Markers flanking these QTLs should be useful tools for combining the resistance to FHB of Asian and European wheats to increase the resistance level of cultivars.     

Inheritance of leaf rust resistance in wheat lines carryingAegilops speltoides Tausch. translocation in Chinese Spring background

The genetic basis of seedling and adult-plant leaf rust resistance was analysed in wheat lines CS 2A/2M 4/2 and CS 2D/2M 3/8, which are reference lines for the leaf rust resistance gene Lr28. Some seedlings of CS 2A/2M 4/2 were susceptible to Indian Puccinia triticina (Pt) pathotypes 77-1, 77-2 and 77-5. These susceptible seedlings exhibited resistance at the adult-plant growth stage. In contrast, CS 2D/2M 3/8 showed resistance to all Pt pathotypes both at the seedling and adult-plant growth stages. The analysis of inheritance in the susceptible plants of CS 2A/2M 4/2 (CS 2A/2M 4/2 APR selection) and CS 2D/2M 3/8 against Pt 77-5 (the frequently occurring Pt pathotype from the Indian subcontinent), indicated that line CS 2D/2M 3/8 was fixed for a dominant gene, presumed to be Lr28, whereas line CS 2A/2M 4/2 was heterogeneous for Lr28. The adult-plant resistance in the CS 2A/2M 4/2 APR selection was conferred by an unknown recessive gene.     

小麦白粉病抗性基因的聚合及其分子标记辅助选择

采用了在早代进行抗性鉴定、淘汰感病株、保留抗病株继续种植、较晚世代（F4代）进行抗性鉴定结合分子标记辅助选择的策略,提高了选到聚合抗性植株的效率。利用与Pm2、Pm4α、Pm8、Pm21紧密连锁或共分离的RFLP标记和PCR标记（SCAR标记）,对含有这些基因的优良品系间配制的杂交组合的F4代进行了分子标记辅助育种选择,并结合抗性鉴定,筛选到14株Pm4α Pm2I的植株,16株Pm2 Pm4α的植株,6株Pm8 Pm21的植株。应该引起注意的是,Pm2 Pm4α对混合白粉病菌的抗性达到高抗至免疫水平,而Pm2和Pm4α单独存在时抗性较差,表明聚合抗病基因植株的抗性提高了,为培育具有持久性抗性的品系或品种提供了新思路,它在实践和理论研究上都将具有重要意义。