Genetic mapping of the barley Rrs14 scald resistance gene with RFLP, isozyme and seed storage protein markers

The scald susceptible barley cultivar ‘Clipper’ and a third‐backcross (BC₃) line homozygous for the Rrs14 scald resistance gene that originally came from Hordeum vulgare ssp. spontaneum were grown in replicated field trials. The level of resistance that Rrs14 confers against field populations of the pathogen Rhynchosporium secalis, the causal agent of scald disease, was evaluated. The Rrs14 BC₃ line exhibited 80% and 88% less leaf damage than ‘Clipper’ in 1995 and 1996, respectively. Given this effectiveness of Rrs14, research was undertaken to identify a linked marker locus suitable for indirect selection of Rrs14. Based on linkage to a set of previously mapped loci, Rrs14 was positioned to barley chromosome 1H between the seed storage protein (hordein) loci Hor1 and Hor2, approximately 1.8 cM from the latter locus. The Hor2 locus is thus an ideal codominant molecular marker for Rrs14. The tight linkage between Rrs14 and Hor2 and the availability of alternative biochemical and molecular techniques for scoring Hor2 genotypes, permits simple indirect selection of Rrs14 in barley scald resistance breeding programmes.     

Chromosomal localization of five mutant genes in rice, Oryza sativa, using primary trisomics

The chromosomal locations of five mutant genes in rice were determined by crossing the marker stocks with the 12 primary trisomics. Genetic segregation of each gene was studied in the F₂ or backcross populations. Out of the 60 possible cross combinations, 43 F₂ or BC₁ populations were studied. Segregation data indicated that spl11 was located on chromosome 12 while wp2 and eg2_(t) were located on chromosome 6. The genes v12_(t) and Bc₆ were located on chromosomes 8 and 9, respectively, which are sparsely populated with genetic markers.     

A quick methodology to identify sexual seedlings in citrus breeding programs using SSR markers

In citrus breeding and genetics, it is very important to distinguish between zygotic and nucellar seedlings in order to eliminate unwanted genotypes. Usually, isozyme marker shave been employed to determine the genetic origin of young plants. In this work we propose the use of SSR markers as an alternative methodology and compare them with isozymes in this kind of screenings. Two different populations were analysed: one derives from an interspecific cross and the other from selfing. We conclude that, in most cases, microsatellites are more efficient than isozymic markers to identify the sexual origin of citrus seedlings, given their higher level of polymorphism and the scarce number of polymorphic isozymes in some populations. We describe a quick and efficient methodology for SSR analysis, including a fast DNA extraction in microcentrifuge tubes, and visualization through silver staining, which eliminates the need for a labelling step. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic analysis of resistance in barley to barley yellow dwarf virus

The inheritance of resistance to barley yellow dwarf virus (BYDV) was studied in the selected 24 spring and winter barley cultivars that showed a high or intermediate resistance level in 1994‐97 field infection tests. The polymerase chain reaction diagnostic markers YLM and Ylp were used to identify the resistance gene Yd2. The presence of the Yd2 gene was detected with both markers in all the resistant spring barley cultivars and lines from the CIMMYT/ICARDA BYDV nurseries. The results of field tests and genetic analyses in winter barley corresponded with marker analyses only when the Ylp marker was used. Genes non‐allelic with Yd2 were detected by genetic analyses and the Ylp marker in moderately resistant spring barley cultivars ‘Malvaz’, ‘Atribut’ and ‘Madras’, and in the winter barley cultivars ‘Perry’ and ‘Sigra’. Significant levels of resistance to BYDV were obtained by combining the resistance gene Yd2 with genes detected in moderately resistant cultivars. The utilization of analysed resistance sources in barley breeding is discussed.     

Random amplified polymorphic DNA (RAPD) analysis for the verification of hybridity in interspecific crosses of Alstroemeria

Random amplified polymorphic DNA (RAPD) markers were used to verify interspecific hybridization in Alstroemeria. Five putative interspecific hybrids and their parents were analysed by means of four preselected RAPD primers. The putative parentage was confirmed in four hybrids and was excluded in one that showed completely different RAPD patterns from its putative parents and a different phenotype. Our results demonstrated that this molecular technique is a powerful tool for verifying hybridity rapidly if the putative parents are given. This tool will allow screening of small immature seedlings for verification of hybridity and should improve the efficiency of breeding programmes.     

Development of simple sequence repeat (SSR) markers in Eucalyptus from amplified inter-simple sequence repeats (ISSR)

Eucalyptus spp. are widely used in exotic plantations. Since many of these trees are derived from vegetative propagation, the routine identification of clones has become increasingly important. The most widely used molecular based method for fingerprinting these clones is by random amplified polymorphic DNAs (RAPDs). Although this technique is useful, its results are not very repeatable, especially between laboratories. The aim of this study was to develop microsatellite markers that are highly repeatable, and to investigate their value in Eucalyptus fingerprinting. Typically, this process involves the expensive procedure of constructing an enriched genomic library. However, we used an intersimple sequence repeat (ISSR) polymerase chain reaction (PCR)‐based enrichment technique for microsatellite‐rich regions. With this relatively inexpensive method, microsatellite‐rich regions were amplified directly from genomic DNA, after which PCR products were cloned and sequenced. From these microsatellite‐rich sequences, primer sets were constructed to amplify mono‐, di‐, tri‐, hexa‐and nona‐nucleotide repeats. These markers were all inherited in a Mendelian fashion in the progeny of a test cross between two Eucalyptus grandis trees. The primer sets developed were also able to amplify the corresponding microsatellite loci from five different Eucalyptus spp., namely E. grandis, E. nitens, E. globulus, E. camaldulensis and E. urophylla.     

甘蓝型油菜Pol CMS育性恢复基因的RAPD标记

采用恢、 保回交群体和集团分离分析(BSA), 筛选了860个10 mer随机引物, 找到了与甘蓝型油菜波里马细胞质雄性不育系(Pol cms)育性恢复基因(Rf)连锁的两个RAPD标记AH19690和AI16830。 它们位于Rf的一侧,与该基因的遗传图距分别为5.9 cM和13.6 cM,两标记间的遗传图距为7.8 cM。这两个RAPD标记的发掘,为进一步利用分子标记     

郏县红牛全基因组测序分析及关键基因SNP分子标记在育种的应用研究

为了更好地扩展对郏县红牛基因组变异的研究,开发更多有效的分子标记,达到促进郏县红牛的进一步选育改良的目标。本研究对30头郏县红牛进行了全基因组重测序,分析了郏县红牛的基因组变异情况,并结合查阅文献筛选影响重要经济性状的遗传变异,检测这些变异在郏县红牛群体中的分布情况。并同时通过实验在3头郏县红牛中加以验证,为郏县红牛的保种与淘汰提供一定的理论依据。     

DNA分子标记在甘薯遗传育种中的应用

DNA分子标记是继形态标记、细胞标记和生化标记之后发展起来的一种新的较为理想的遗传标记,在甘薯育种方面发挥了重要作用。主要概述了分子标记在甘薯的起源、进化与分类、图谱构建、遗传多样性分析、品种鉴定、基因定位与辅助育种等方面的研究进展,并对甘薯的分子育种提出了展望。     

SSR标记鉴定玉米品种亲子关系的研究

[目的]探讨杂交玉米品种亲子关系的分子检测判读标准。[方法]以16个玉米杂交种及其双亲和202个骨干自交系为引物筛选材料,分别构建2个二联体亲子鉴定盲样和2个三联体亲子鉴定盲样,用CTAB法提取幼苗叶片DNA,选137对SSR引物进行玉米品种的亲子检测。[结果]从137对SSR引物中筛选出了多态性信息含量（PIC值）高、扩增条带清晰和重复性好的20对核心引物。SSR分子检测结果与实际情况一致。[结论]利用SSR标记技术鉴定玉米品种亲子关系的方法是可行的。