Study on Identification of RAPD Marker of Phytophthora sojae Associated with Rps1-k

A near-isogenic lines(NILs)-Williams and Williams82 is used to identify molecular marker linked to the resistance gene Rps1-k by RAPD. Genomic DNAs extracted from soybean leaves of the NILs were analyzed by RAPDusing 160 different 10-nt random primers. Some specific DNA fragments were amplified from Williams82 with 4 primer(OPF-16, OPB-05, OPD-06 and OPH-05) which contains Rps1-k. All these specific DNA fragments were not de-tected in Williams. The experiment with OPH-05 was repeated 3 times and the results were the same. Using primer-OPH-05 to detect other resistance cultivars with Rps1-k, almost everyone can amplify the specific DNA fragment. So it is inferred that the specific DNA fragment is probably linked to Rps1-k.     

鳜野生群体与养殖群体的RAPD分析

用60个随机引物对鳜Siniperca chuatsi Basilewsky野生群体和养殖群体进行随机扩增多态DNA(RAPD)分析,经过引物筛选,分别用55个和54个引物对野生鳜和养殖鳜进行群体内分析。结果表明,野生群体多态位百分率为85．75％,群体内遗传相似率和遗传距离分别为0．8547和0．1453;养殖群体多态位百分率为16．39％,遗传相似率和遗传距离分别为0．9527和0．0473;两群体间遗传相似率和遗传距离分别为0．6905和0．3095;鳜野生群体具有较高的遗传多样性,养殖群体的遗传多样性却显著降低,野生群体与养殖群体间有明显的遗传差异,说明人工繁育对鳜基因组造成了显著的影响。     

Independent segregation of two isozyme markers and inter-plant differences in nuclear DNA content in the interspecific backcross (Allium fistulosum L. × A. cepa L.) × A. cepa L.

Summary From backcrosses of three interspecific hybrids (A. fistulosum x A. cepa) with a. cepa 14 diploid and 2 triploid plants were recovered.In this BC1 population introgression of A. fistulosum genetic material into the A. cepa nuclear genome was studied using two isozyme markers: Got-1 and Got-2. Both loci carried two alleles. A. cepa was monomorphic for both markers. A. fistulosum was polymorphic for Got-2. Based on their Got isozyme pattern seven out of the 14 diploid BC1 plants had a recombinant genotype. The loci appeared to be unlinked. Differences were observed in nuclear DNA contents between the diploid BC1 plants, indicating that gametes produced by the interspecific hybrids contained different combinations of chromosomal material from A. cepa and A. fistulosum.Abbreviations Adh alcohol dehydrogenase - Got glutamate oxaloacetate transaminase - Idh isocitrate dehydrogenase - Pgi phosphoglucoisomerase - Pgm phosphoglucomutase     

Molecular markers for late blight resistance breeding of potato: an update

Late blight is the most devastating disease of the potato crop that can be effectively managed by growing resistant cultivars. Introgression of resistance (R) genes/quantitative trait loci (QTLs) from the Solanum germplasm into common potato is one of the plausible approaches to breed resistant cultivars. Although the conventional method of breeding will continue to play a primary role in potato improvement, molecular marker technology is becoming one of its integral components. To achieve rapid success, from the past to recent years, several R genes/QTLs that originated from wild/cultivated Solanum species were mapped on the potato genome and a few genes were cloned using molecular approaches. As a result, molecular markers closely linked to resistance genes or QTLs offer a quicker potato breeding option through marker‐assisted selection (MAS). However, limited progress has been achieved so far through MAS in potato breeding. In near future, new resistance genes/QTLs are expected to be discovered from wild Solanum gene pools and linked molecular markers would be available for MAS. This article presents an update on the development of molecular markers linked to late blight resistance genes or QTLs by utilization of Solanum species for MAS in potato.     

Converting restriction fragment length polymorphism to single‐strand conformation polymorphism markers and its application in the fine mapping of a trichome gene in cotton

A well‐characterized and systematically organized collection of genetic markers is crucial in the study of any crop species. It is the basis of map‐based gene cloning and crop improvements through marker‐assisted selections. Single‐strand conformation polymorphism (SSCP) has been a robust way of discovering new polymorphisms in marker development without the requirement of sequencing. Here, we report the first approach of applying SSCP marker discovery methods in the genetic map construction and gene mapping of cotton species. A total of 80 restriction fragment length polymorphism (RFLP) markers were selected from a region on published cotton genetic maps around the T1 gene related to cotton trichome. Among the 80 RFLPs, 28 showed polymorphisms through SSCP, showing a polymorphic rate of approximately 35%, which is much higher than that of simple sequence repeat (SSR) markers in the same region (7.8%). By integrating these newly generated SSCP markers, a detailed genetic map was reconstructed around this region using an F₂ population derived from a cross between Gossypium arboreum and G. herboceum. The reconstructed region comprises 22 SSCP markers, eight SSR markers and the T1 gene, spanning 21.6 cM. The marker order of the new map agrees well with published reference RFLP maps. The above results suggest that SSCP method can be applied very efficiently and reliably to the marker development of cotton genomes. It will prove to be even more valuable and robust after the public release of cotton whole‐genome sequences.     

Genetic linkage between male sterility and non‐spiny trait in safflower (Carthamus tinctorius L.)

Genetic male sterility (GMS) exists naturally in safflower (Carthamus tinctorius L.). In the existing safflower GMS lines, sterile and fertile plants are distinguishable at flowering. This causes delay in fertile plants rouging and reduction in hybrid purity. In this investigation, a cross between a spiny GMS parent 13‐137 and a spiny non‐GMS parent ‘A1’ was effected. One sib cross, SC‐67, producing non‐parental‐type non‐spiny sterile and spiny fertile plants in F₃ was advanced to F₉ through sib crossing between non‐spiny sterile and spiny fertile plants. Mendelian digenic segregation was not observed for non‐spiny trait and male sterility. The results revealed strong linkage between these traits. The linkage was confirmed in F₂ generations of crosses between a non‐spiny marker‐linked GMS line (MGMS) and five elite lines. Male sterility–linked non‐spiny trait could distinguish sterile and fertile plants at elongation stage. The MGMS would be useful in production of pure F₁ hybrid seed and development of elite populations.     

大豆对大豆花叶病毒株系SC6和SC17抗病基因的精细定位

针对我国北方和长江流域大豆产区广泛分布的SMV株系SC6和SC17,利用2个抗病大豆品种Q0926和中豆35分别与感病品种南农1138-2和南农菜豆5号配制2个抗感杂交组合Q0926×南农1138-2和中豆35×南农菜豆5号以及一个抗抗组合Q0926×中豆35,研究3个组合的F₁、F₂、F_2:3抗性遗传规律,探讨Q0926对SC6和中豆35对SC17及2个抗病品种对同一SMV株系抗性基因的等位关系,并对大豆对2个株系的抗病基因进行了标记定位。结果显示,Q0926×南农1138-2和中豆35×南农菜豆5号2个抗感杂交组合在分别接种SC6和SC17后,F₁表现抗病,F₂呈3抗∶1感分离比例,F_2:3家系呈1抗∶2分离∶1感病的分离比率,表明Q0926对SC6和中豆35对SC17的抗病性分别由1对显性基因控制;抗抗组合Q0926×中豆35的F₁和F₂在接种2个株系后均未发现感病单株,表明Q0926与中豆35对SC6和SC17株系的抗病基因分别是等位或紧密连锁的。分别利用2个抗感组合的F₂和F_2:3群体对2个抗病基因的定位结果显示,第2染色体上的25个SSR标记与抗SC6的基因R_SC6连锁,最近的2个标记与抗性基因R_SC6的排列次序和遗传距离为BARCSOYSSR_02_0617(0.775 cM)-R_SC6-BARCSOYSSR_02_0621(0.519 cM);第2染色体上的38个SSR标记与抗SC17的基因R_SC17连锁。最近的2个标记与抗性基因R_SC17的排列次序和遗传距离为BARCSOYSSR_02_0622(0.264 cM)-R_SC17-BARCSOYSSR_02_0627(0.262 cM),其对应的物理区间分别为52 kb和60 kb。抗性遗传研究为抗大豆花叶病毒育种的亲本选配、后代选择提供了理论指导,抗性基因的标记定位研究为抗性基因的分子标记辅助选择和抗病基因的图位克隆奠定了基础。     

Development and utilization of novel SSRs in foxtail millet [Setaria italica (L.) P. Beauv.]

Although the foxtail millet [Setaria italica (L.) P. Beauv.] is recently regarded as a model crop for studying functional genomics of biofuel grasses, its genetic improvement to some extent was limited due to the non‐availability of molecular markers, particularly the microsatellite markers and the saturated genetic linkage map. Considering this, we attempted to generate a significant number of microsatellite markers in cultivar ‘Prasad’. Two hundred and fifty‐six clones were sequenced to generate 41.82‐kb high‐quality sequences retrieved from genomic library enriched with dinucleotide repeat motifs. Microsatellites were identified in 194 (76%) of the 256 positive clones, and 64 primer pairs (pp) were successfully designed from 95 (49%) unique SSR‐containing clones. The 67.4% primer designing ability, 100% PCR amplification efficiency and 45.3% polymorphic potential in the parents of F₂ mapping population established the efficacy of genomic microsatellites. All the 64 microsatellite markers displayed high level of cross‐species amplification (~67%) in 10 millets and non‐millets species. These experimental findings suggest the utility and efficacy of SSRs in diverse genotyping applications, resolving QTLs, phylogenetic relationships and transferability in several important grass species.     

Independent target region amplification polymorphism and single‐nucleotide polymorphism marker utility in genetic evaluation of sugarcane genotypes

The independent target region amplification polymorphism (TRAP) and single‐nucleotide polymorphism (SNP) marker s were used for genetic evaluation of different selected 47 sugarcane genotypes. A total of 23 pairs of TRAP markers generated 925 alleles, of which 74% alleles were polymorphic. Polymorphism was generally high (>50%), ranging from 54 to 98%. The polymorphism information content (PIC) values 0.20 varied among the primer combination ranging from 0.17 in SAI + Arbi 2 to 0.31 in GL 2+ Arbi 1 with an average of 0.24. However, the Pearson correlation between PIC and power of discrimination (PD) was found to be less significant. Single‐nucleotide polymorphisms were used first time for the assessment of genetic diversity among different species of Saccharum and cultivated sugarcane varieties. The SNPs were detected from 454 sequencing. A total of 245 SNP markers were assayed across the 47 genotypes, and 167 SNPs were found to be polymorphic. The PIC values ranged from 0.04 to 0.38 with an average of 0.21, and their respective PD varied from 0.58 to 0.04 with an average value of 0.31. The obtained results relatively significant were compared with the other marker systems through genetic similarity and the clusters formed in different unweighted pair group method with arithmetic mean clustering dendrogram. The clustering analysis established genetic relationship in the order of Erianthus > Sclerostachya > Narenga > Saccharum spontaneum > S. robustum > S. barberi > S. officinarum/cultivars. These results ratify TRAP and SNP marker systems for assessing genetic diversity studies, and more diversified Erianthus spp. can contribute substantially towards sugarcane varietal improvement through breeding with Saccharum spp. or hybrid cultivars.     

瓠瓜耐湿涝相关根系性状遗传规律及分子标记筛选

以耐湿涝瓠瓜材料JZS和不耐湿涝材料T2002及其杂交F2群体为材料,选择湿涝条件下不定根数目作为耐湿涝鉴定指标,分析瓠瓜耐湿涝特性遗传规律,并采用集团混合分离分析法筛选相关分子标记。结果表明,瓠瓜亲本JZS的耐湿涝特性由1对显性单基因控制,F1的不定根数目比耐湿涝亲本JZS增多,表现出超亲优势。在600个RAPD和100对瓠瓜SSR引物中,共有18个引物(14个RAPD和4对SSR)在双亲中显示多态性。最终筛选到瓠瓜SSR引物S87/88,在双亲及基因池间稳定扩增出片段大小为230 bp的差异条带。通过F2153个单株验证,确定表型调查耐湿涝结果与分子标记S87/88鉴定结果相关性极显著(相关系数0.78),利用Mapmaker 3.0软件对分子标记与表型结果进行连锁分析,S87/88与瓠瓜耐湿涝相关的不定根数目基因的连锁距离为8.8 cM,为进一步利用分子辅助育种加速耐湿涝瓠瓜新品种的选育提供有效标记。