SCAR and RAPD markers associated with 18-carbon fatty acids in rapeseed, Brassica napus

Breeding rapeseed for enhanced oil quality includes the development of varieties with low linolenic acid content. The breeder also aims to develop varieties with a high linoleic acid content because of its nutritional value. Restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) markers have been developed for linolenic acid content, but they are not best suited for a direct application in marker-assisted selection. The RFLP technique is too complex and time-consuming and RAPD markers lack codominance, precluding the distinction of homozygous from heterozygous individuals. In this report the conversion of a RAPD marker to a codominant sequence characterized amplified region (SCAR) marker named L1L9 is described. One of the alleles consisting of an 899 bp fragment (allele A), is associated with low linolenic acid content. The other allele consists of an 641 bp fragment (allele B) and is associated with high linolenic acid content. This marker explains approximately 25% of the genetic variation for this trait. Linkage analysis in the mapping population indicates that the SCAR marker probably tags an ω-3 desaturase gene in B. napus. Two RAPD markers were found to be associated with oleic/linoleic acid content. Markers M14-350 and I06-650 explained approximately 10% and 7% of the genetic variation for linoleic acid content, respectively. These two markers were found linked at 12.3cM in the segregating B. napus F₂ progeny used for mapping. All the markers reported in this paper should be useful in breeding programmes for developing high linoleic and low linolenic acid rapeseed varieties.     

Marker-assisted selection of common beans for resistance to common bacterial blight: efficacy and economics

The possibility of using random amplified polymorphic DNA (RAPD) markers previously mapped in the common bean PC50/XANI59 population to select for resistance to common bacterial blight (CBB) in different populations was examined. Two out of 02 selected RAPD markers were polymorphic in HR56 and W0633d, the parental lines used in this experiment. Cosegregation analysis of the two polymorphic markers and disease reaction in a recombinant inbred (RI) population derived from HR67/W1744d confirmed that one of the two RAPD markers, BC420₉₀₀, was significantly associated with a major quantitative trait locus‐conditioning resistance to CBB in HR67. This locus accounted for approximately 51) of the phenotypic variation. The RAPD marker was transformed into a sequence characterized amplified region (SCAR) marker and used for selection in a different population derived from ‘Envoy’/HR67. Prediction for resistance to CBB with the BC420_.990 SCAR marker was 94.2% accurate in this population. A comparison between marker‐assisted selection (MAS) and conventional greenhouse screening showed that the cost of MAS is about one‐third less than that of the greenhouse test.     

Random amplified polymorphic DNA analysis of Australian rice (Oryza sativa L.) varieties

Summary The genetic relationships between rice varieties were analysed by using the polymerase chain reaction (PCR), with arbitrary oligonucleotide primers in the random amplified polymorphic DNA (RAPD) method. PCR with 22 arbitrary primers applied to 37 varieties produced 144 useful markers, of which 67% were polymorphic. Thus, with selected primers sufficient polymorphism could be detected to allow identification of individual varieties. Visual examination of electrophoresis gels and analysis of banding patterns confirmed that commercial Australian and USA lines and their relatives were very closely related, with similarity indices of 88–97%. Three varieties originating from more distant geographical centres were easily distinguished, producing variety-specific amplification profiles and expressing a lower similarity index of 80% to all other varieties tested. PCR offers a potentially simple, rapid and reliable method for rice genotype identification and recognition of lines that could contribute genetic diversity to new commercial varieties.Abbreviations PCR Polymerase Chain Reaction - RAPD Random Amplified Polymorphic DNA     

Identification of a SCAR marker associated with Bm, the beet mosaic virus resistance gene, on chromosome 1 of sugar beet

Beet mosaic virus (BtMV) is an aphid transmitted, viral disease of beet found worldwide. The Bm gene, a resistance gene effective against BtMV, was identified in the sugar beet line 8500 and backcrossed into a C37 background to produce line C719. Three populations were developed from the cross of line C719 with the susceptible line C37 with the intent of developing markers for use in marker‐assisted selection. The F₂ progeny of three crosses were scored for resistance. Two of the three populations conformed to a 3 : 1 ratio, indicating a single gene trait. Sequence characterized amplified region (SCAR) markers were developed by using bulked segregant analysis combined with random amplified polymorphic DNA type markers. The markers showed close association to the Bm resistance gene and were effective in all three populations. The A₁ allele for genetic male sterility also was found to be associated with Bm and the SCAR marker. Development of a single‐nucleotide polymorphism marker from the SCAR sequence was used to validate linkage to chromosome 1 using separate mapping populations. This marker will be useful for the introgression of the Bm gene into germplasm.     

Identification of molecular markers associated with oleic and linolenic acid in spring oilseed rape (Brassica napus)

The quality of the oil derived from oilseed rape is determined by its fatty acid composition. Breeding oilseed rape for enhanced oil quality includes the development of cultivars with high oleic and low linolenic acid. Random amplified polymorphic DNA (RAPD) and intersimple sequence repeat (ISSR) techniques were investigated for the development of molecular markers for genes controlling oleic and/or linolenic acid. Markers that were identified were converted to sequence characterized amplified region (SCAR) markers for use in breeding. Molecular markers associated with these two fatty acids were identified in a doubled haploid population derived from a cross between the oilseed rape lines TO99‐5318‐20, very high oleic (>79%) and very low linolenic acid (<2%) × DH12075, high oleic (68%) and higher linolenic acid (>7%). Eight RAPD markers were associated with oleic and linolenic acid contents. The RAPD marker UBC 2₈₃₀ accounted for 43% and 13% of the genetic variation for oleic and linolenic acid levels, respectively. The RAPD marker UBC 153₅₅₀ accounted for 19% of the genetic variation for linolenic acid. The UBC 2₈₃₀ fragment was converted to a SCAR marker. The markers identified in this study should be useful tools for the early generation selection of high oleic and low linolenic acid genotypes in oilseed rape breeding programmes.     

Contrasting patterns of fatty acid composition and oil accumulation during fruit growth in several olive varieties and locations in a non-Mediterranean region

Olive growing has expanded considerably in the last few decades outside of the Mediterranean Basin to non-traditional regions in the Southern Hemisphere. When growing olive genotypes (i.e., varieties) outside of their area of origin, the importance of environmental factors such as temperature and genotype × environment interactions in determining olive oil production and oil quality has been suggested. In several Mediterranean varieties and one South American variety, we assessed the dynamics of fruit growth and oil accumulation along with the evolution of fatty acid composition at multiple locations over two growing seasons. Oleic acid content (%), the principal fatty acid present in olive oil, showed four contrasting patterns during fruit growth when modeled against thermal time from flowering using linear and bilinear regressions: (1) a sharp linear decrease for the varieties ‘Arauco’ and ‘Arbequina’; (2) a plateau followed by a late linear decrease of moderate slope for ‘Barnea’ and ‘Manzanilla Fina’; (3) a slow linear decrease for ‘Frantoio’; and (4) no decrease in ‘Coratina’. Linoleic acid (%) showed linear increases in ‘Arauco’ and ‘Arbequina’ that appear to be inversely related to the decreases in oleic acid, while bilinear patterns were found for many other varieties. Both the rates of fruit growth and of oil accumulation were more important in determining maximum fruit dry weight and oil concentration (%), respectively, than duration when expressed on a thermal time basis. Temperature during oil synthesis was negatively related to final oil concentration. Experiments under controlled conditions would greatly contribute to our understanding of how fruit growth as well as oil quantity and quality are influenced by environmental factors.     

四季蜜龙眼夏季开花坐果特性及传粉昆虫种类调查

为了解四季蜜龙眼夏季开花坐果特性和传粉昆虫种类,于夏季开花期间选定花穗记录雌雄花和果实数量,并以随机网捕方式采集传粉昆虫进行鉴定。结果表明:四季蜜龙眼夏季花期平均每穗开花天数为12.9天,雌雄花比例为1:6.57,授粉受精期的温度处于25～36℃之间,在较高的温度条件下雌花坐果率达到27.6%;雌花脱落占雌花数的11.1%,小果脱落占雌花数的61.3%。传粉昆虫有5目13科21种,以花金龟科的种类最多,占总数的33.3%;其次为蜂类和蝇类昆虫,分别占总数的30.1%和24.1%。     

Development of SCAR markers linked to the Ns locus in potato

A random amplified polymorphic DNA marker OPG17₄₅₀ linked to the Ns gene that confers resistance of potato to potato virus S (PVS), was used to develop sequence‐characterized amplified region (SCAR) markers. After cloning and sequencing of OPG17₄₅₀ new polymerase chain reaction (PCR) primers were designed to generate dominant (SCG17₃₂₁) and codominant (SCG17₄₄₈) markers. For SCG17₄₄₈, polymorphism between susceptible and resistant genotypes was recovered after digestion of the marker with the restriction enzyme Muni. In addition to the band corresponding to ‘susceptible’ allele that does not contain the Muni cleavage site, two bands of approximately 251 bp and 197 bp were observed in the resistant genotypes. The usefulness of these SCAR markers was verified in diploid potatoes possessing the Ns locus from clone G‐LKS 678147/60, and in tetraploid potatoes derived from G‐LKS 678147/60 and from clone MPI 65118/3.     

Development of SCAR markers linked to the Pm21 gene conferring resistance to powdery mildew in common wheat

Powdery mildew is an important disease in most of the wheat production areas of the world. The resistance gene Pm21 (6AL/6VS trans-location) derived from Haynaldia villosa confers resistance to all available isolates of Erysiphe (Blumeria) graminis f. sp. tritici in China and Europe. The objective of this study was to develop fast and reliable sequence characterized amplified region (SCAR) markers linked to the Pm21 gene. A random amplified polymorphic DNA (RAPD) marker for Pm21, OPH17₁₄₀₀, was converted to SCAR markers after sequencing the two ends of the polymorphic DNA fragment. Two SCAR markers, SCAR₁₂₆₅ and SCAR₁₄₀₀, were developed to detect the Pm21 gene in different genetic backgrounds. The specific SCAR₁₂₆₅ marker enable large-scale accurate screening for the presence/absence of Pm21 allele.     

Genetic diversity,population structure and key phenotypic traits driving variation within soyabean (Glycine max) collection in Ghana

Soybean [Glycine max (L.) Merrill] is an important oilseed crop worldwide and it has recently become the crop of interest in Ghana. In this study, 142 soybean accessions were genotyped with 34 SSR markers and concurrently evaluated for five quantitative and two qualitative phenotypic traits. Twenty‐nine of the SSR markers were polymorphic with mean allele number of 5.3, polymorphic information content (PIC) of 0.51 and gene diversity of 0.55. Molecular analysis based on unweighted paired group arithmetic mean (UPGMA) clustering and principal coordinate analysis (PCoA) was similar in explaining the extent of diversity within the accessions. Structure analysis placed most of the accessions into two subpopulations with 18 (12.7%) as admixtures. Principal component analysis (PCA) based on phenotypic traits revealed two clusters. Both UPGMA clustering‐based SSR data and PCA from phenotypic data showed similar results. The assembled germplasm is genetically diverse with high variation in flowering and maturity period, and key yield components which could be exploited in developing superior varieties well adapted to Ghana and West Africa.     

开花期低温胁迫对四川攀西稻区水稻开花结实的影响

以3种籼稻品种和3种粳稻品种为试验材料, 利用人工气候室在开花期进行低温胁迫处理, 研究了低温胁迫对攀西稻区籼、粳稻开花和结实及两者间关系的影响。结果表明, 开花期低温胁迫下籼稻和粳稻的开花习性、花药和花粉特性和结实表现不同。常规粳稻开花对低温有较高的耐冷性。低温胁迫下籼稻品种(组合)花药体积、花药开裂率、可育花粉率、柱头着花粉数和柱头花粉萌发率较对照降低幅度均比粳稻品种(组合)大; 籼稻品种(组合)各产量构成因素较对照降低幅度比粳稻品种(组合)大。相关分析表明, 结实与水稻花药和花粉主要性状有密切关系。开花期低温胁迫影响花药和花粉发育成熟, 使花药不能正常开裂、散粉不足, 可育花粉率和柱头花粉萌发率降低, 直接影响受精结实, 成为结实率降低的主要原因之一。     

Development and Validation of SCAR Markers Co-Segregating with an Agropyron Elongatum Derived Leaf Rust Resistance Gene Lr24 in Wheat

Summary An Agropyron elongatum-derived leaf rust resistance gene Lr24 located on chromosome 3DL of wheat was tagged with six random amplified polymorphic DNA (RAPD) markers which co-segregated with the gene. The markers were identified in homozygous resistant F₂ plants taken from a population segregating for leaf rust resistance generated from a cross between two near-isogenic lines (NILs) differing only for Lr24. Phenotyping was done by inoculating the plants with pathotype 77-5 of Puccinia triticina. To enable gene-specific selection, three RAPD markers (S1302₆₀₉, S1326₆₁₅ and OPAB-1₃₈₈) were successfully converted to polymorphic sequence characterized amplified region (SCAR) markers, amplifying only the critical DNA fragments co-segregating with Lr24. The SCAR markers were validated for specificity to the gene Lr24 in wheat NILs possessing Lr24 in 10 additional genetic backgrounds including the Thatcher NIL, but not to 43 Thatcher NILs possessing designated leaf rust resistance genes other than Lr24. This indicated the potential usefulness of these SCAR markers in marker assisted selection (MAS) and for pyramiding leaf rust resistance genes in wheat.     

RAPD and SCAR markers linked to the sex expression locus M in asparagus

Bulk segregant analysis (BSA), random amplified polymorphic DNA (RAPD) and sequence characterized amplified region (SCAR) methods were used to map molecular markers to the sex locus M of asparagus. Two parents, A19 (male, Mm) and MW25 (female, mm), and 63 progeny were used for the study. Two DNA bulks, one male and one female, were made by pooling equal amounts of DNA from 10 randomly selected progeny of each sex type. A total of 760 arbitrary decamer oligonucleotide primers were used for RAPD analysis. Primer OPC15 produced two RAPD markers, OPC15-98 and OPC15-30, both of which were linked to the M locus at a distance of 1.6 cM. Subsequently, amplified RAPD fragment OPC15-98 was cloned and sequenced. The sequence was then used to design flanking 24-mer oligonucleotide SCAR primers SCC15-1 and SCC15-2. Both of these SCAR primers amplified a single 980 bp fragment; the same size as the cloned RAPD fragment. However, the SCAR marker was dominant as was the original OPC15-98 band from which it was derived. These RAPD and SCAR markers could be used for scoring male and female progeny in the mapping population, but were not found to be applicable to other asparagus germplasm studied. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of Increasing Temperatures on Spikelet Fertility in Different Rice Cultivars based on Temperature Gradient Chamber Experiments

Spikelet sterility in rice (Oryza sativa L.) induced by high temperatures is a major concern given global warming predictions. We studied differences among eight rice cultivars in spikelet fertility at five different temperature levels in temperature gradient chamber (TGC) experiments. Six japonica and two indica cultivars were exposed to high‐temperature gradients in TGCs during the 2005 flowering season. Spikelet sterility increased with temperature in TGCs and differed among cultivars because of both variations in temperature tolerance and timing of heading. The correlation between spikelet fertility of individual panicles and both air temperature and panicle temperature during flowering was analyzed to compare tolerances among cultivars. The temperature (T₇₅) at which spikelet fertility was 75 % of maximum ranged from 34 to 39 °C air temperature and differed significantly among cultivars. Indica varieties had higher T₇₅ values than japonica varieties. The T₇₅ values based on panicle temperature also differed among cultivars, but the difference between indica and japonica varieties were less significant. We concluded that the higher temperature tolerances of indica cultivars in our experiments could be attributed to lower spikelet temperatures, and cultivars with similar spikelet temperatures still had different heat tolerances due to differences in pollination ability.     

Earliness of flowering and fruiting of forty strawberry varieties; A statistical study

Summary For the purpose of strawberry breeding the earliness of flowering and the rate of fruit development of strawberries should be considered two independent properties. This is the main conclusion from a statistical study of the dates of flowering and harvest of 40 varieties in one-year-old plants grown in the open.Further it was found that in a number of varieties the date of first flowers is influenced by the temperature in November, that is, a warm November delays flowering.The vigour of the plant appeared not to be correlated with the date of flowering.Certain high temperatures appeared to depress the rate of fruit development.     

2015年奉贤区梨花期异常气候对开花坐果影响的调查分析

为了解决梨花期气候异常波动引起的坐果数偏少的问题,以2015年上海金冠蜜梨种植园的5种梨树品种为材料,对蜜梨开花期、坐果数进行实地调查,并将调查结果与奉贤地区的实测气温、降水量、日照时数、天气现象进行对比分析。结果表明,适宜开花坐果的气候条件为持续3~4天以上以晴为主或晴雨相间天气,开花后前3天或开花盛期的日平均气温应≤15℃,最高气温应≤25℃;子房发育期遇冰粒天气有受冻现象,易产生劣质果。梨开花期遇温度过高使花期缩短而影响坐果数,冰粒天气对果实商品性有较大的影响,通过花粉树间作、嫁接、人工授粉、利用小气候效应调节花期等栽培措施,可避开和减轻开花坐果期不利天气的影响,提高坐果数和果实商品性。     

生物抑制剂处理结合低温冷藏对龙眼保鲜质量的影响

以提高龙眼的保鲜质量和商品率为目的，采用生物抑制剂处理龙眼进行低温气调保鲜。采用正交试验方法，分析了生物抑制剂对龙眼果皮褐变和保鲜效果的影响。结果表明，在相同的低温气调保鲜条件下，采用生物抑制剂处理，可更有效地抑制龙眼保鲜过程的呼吸作用，有效降低了酶活性的变化，延缓了龙眼果实的衰老与果皮褐变，保鲜时间长，且更好地保留了果实的营养成分，商品率高。     

粤西龙眼遗传多样性的RAPD分析

为了保护和利用粤西野生和栽培龙眼种质资源,通过RAPD技术对粤西野生和栽培共5个龙眼品种的遗传多样性进行分析。结果表明：从100个10 bp长的随机引物中筛选出14个重复性好、稳定性高的有效引物,共扩增出70条带,其中多态性带42条,占总扩增条带的60%。聚类分析结果表明：5个龙眼品种间的遗传差异性不大,但野生龙眼与其他4个龙眼品种的遗传距离相对较大,平均为0.07375,在系统树上单独聚为一支,其余4个品种聚为另一支,说明野生龙眼与栽培品种之间的亲缘关系相对较远。‘双孖木’与‘大乌圆’的遗传距离最小,仅为0.01236,在系统树上构成姊妹类群,推测二者具有共同起源或为近缘品种。     

Evaluation of F2 and F3 plants introgressed with QTLs for clubroot resistance in cabbage developed by using SCAR markers

Clubroot disease caused by Plasmodiophora brassicae is one of the major diseases of Brassica crops, often devastating to the cultivation of cruciferous crops in temperate regions. In a previous study (Moriguchi et al. 1999) identified three major quantitative trait loci (QTLs) for clubroot resistance, each in a separate linkage group, in a population derived from a cross between a clubroot‐susceptible inbred cabbage line, Y2A and a resistant inbred kale line, K269. In this study, the original random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphism (RFLP) markers were converted into sequence‐characterized amplified region (SCAR) markers to facilitate large‐scale marker‐assisted screening of clubroot resistance in cabbage breeding. Of 15 RAPD markers closely linked to the three QTLs, nine SCARs were developed as dominant markers after cloning and sequencing. In addition, two RAPD markers were converted into co‐dominant cleaved amplified polymorphic sequence (CAPS) markers, and one RFLP marker out of three tested was converted to a dominant SCAR marker. The effect of selection for resistance by the improved markers was evaluated in progeny plants in the F2 and F3. A total of 138 F2 plants were genotyped with nine SCARs and 121 well‐distributed makers consisting of 98 RAPD, 19 RFLP, two isozymes, and two morphological markers in order to estimate the level of resistance and the proportion of undesirable alleles from the kale in non‐target areas in each of the F2 populations. An F2 plant, YK118, had kale alleles at QTL1, QTL3 and QTL9. Three F2 plants, namely, YK107, YK25 and YK51 had kale alleles at only QTL1, QTL3 and QTL9, respectively. These F2 plants were selected for their low proportion of alleles derived from kale in non‐target regions. YK118, like the resistant kale parent, expressed very high resistance to three field isolates of Plasmodiophora brassicae, whereas the mean disease index in the F2 and F3 plants carrying only single QTLs was intermediate. The QTLs showed no differential response to the isolates. These plants with improved resistance will be useful as parental inbred lines for F1 hybrids.     

添加剂对速冻龙眼裂果率的影响

通过使用添加剂减少速冻龙眼生产过程中容易出现的裂果现象,将羧甲基纤维素钠(CMC-Na)、黄原胶和复合磷酸盐作为添加剂对速冻龙眼裂果率的影响进行研究,试验结果表明,0.6%的复合磷酸盐抗冻裂效果最好。