Application of Molecular Marker Technologies in Stress Resistance Breeding of Rapeseed

Rapeseed is the largest source of China's edible vegetable oil and plays a pivotal role in China's edible oil market.With global warming and frequent occurrence of various extreme climates,traditional hybrid breeding has been unable to meet the production requirements for rape yield and stress resistance.In recent years,the rapid development and maturity of molecular marker technologies have opened up new ways for stress resistance breeding in rape.This article mainly discusses several types of molecular marker technologies commonly used in rapeseed breeding,such as RFLP,SSR,and SNP,the advantages of molecular marker technologies over conventional breeding and other genetic marker technologies,as well as the application of molecular marker technologies in rapeseed disease resistance,drought resistance,cold resistance and lodging resistance breeding,the current problems and development prospects in breeding.

Research Progress of Molecular Markers in Genetic Diversity of Rapeseed

In recent years,with the continuous improvement and development of molecular technology in the application process,different types of DNA molecular markers have made rapid progress in the study of genetic diversity of rapeseed. The study of genetic diversity is conducive to the correct formulation of the strategy of collecting and in situ preservation of genetic resources of rapeseed,and it is the genetic basis for the improvement of rapeseed varieties. This article mainly starts with the three DNA molecular markers( SSR,RAPD,AFLP) widely used in the study of genetic diversity of rapeseed. By introducing the application principles and characteristics of SSR,RFPD and AFLP molecular markers,research progress of these three marker technologies in genetic diversity of rapeseed is briefly described.

Development and Utilization of 1S^1 Chromosomearm-specific Molecular Markers of Aegilops longissima

Introducing the 1S^1 chromosome of Aegilops longissima into wheat genome can significantly improve wheat grain quality and contents of iron and zinc. Therefore, the development of molecular markers specific to 1S^1 chromosome of A. longissima is of important significance for breeding high-quality wheat with high contents of iron and zinc in grains. In this study, nine molecular markers specific to 1S^1 chromosome of A. longissima were developed, including two 1S^1S specific markers,six 1S^1L specific markers and one 1S^1 specific marker which was located on both short and long arms. The practicability of these molecular markers were verified using hybrid population as materials. The results showed that hybrid population could be effectively screened and identified, which indicated that the developed 1S^1 chromosome-specific molecular markers could be used for screening and identification of hybrid population and could be used in marker-assisted breeding of high-quality wheat with high contents of Fe and Zn in grains.

Breeding Rice Restorer Lines with High Resistance to Bacterial Blight by Using Molecular Marker-Assisted Selection

Two bacterial blight （BB） resistance genes, Xa21 and Xa4, from IRBB24 were introduced into hybrid rice restorer line Mianhui 725, which is highly susceptible to BB, by using hybridization and molecular marker-assisted selection technology. Four homologous restorer lines were obtained through testing the R target genes with molecular markers and analyzing parental genetic background. Inoculation of the four lines and their hybrids with the specific strains of Xanthomonas oryzae pv. oryzae, P1, P6 and seven representative strains of Chinese pathotype, C Ⅰ -CⅦ, showed that all of the four lines and their hybrids were highly resistant and presented broad resistance-spectrum to BB. The hybrids of G46A / R207-2 displayed good agronomic characters and high yield potential, and R207-2 was named Shuhui 207.

Pyramiding Breeding by Marker-Assisted Recurrent Selection in Upland Cotton: Selected Effects on Resistance to Helicoverpa armigera

The coincidence rates were more than 96% among the instar-weighted average of bioassaysin the lab, the percentage of resistance to Km in the field and the percentage of plantscontaining Bt gene. So, the performance of resistance to Km in the field can be used torepresent the transgenic Bt gene for selecting the resistance to bollworm. The instar-weighted averages were 30.585, 24.182, 16.615, 10.601, 10.123, 7.440 and 7.215 for theC0, P1, M1, M2, MP1, P2 and MP2 populations, respectively. The variance analysisindicated that the instar-weighted average in C0 was greatly significantly higher thanthat in all other populations, i.e., the performance of resistance to bollworm in C0 washighly significantly lower than all other populations. And the resistance in P1 wasgreatly lower than that of M1, M2, MP1, P2 and MP2, and M1 greatly lower than that of M2,MP1, P2 and MP2. There were no significant differences among M2, MP1, P2 and MP2. Withinthe populations of the first cycle selection, MP1 and M1 were greatly significantlyhigher than P1, and MP1 significantly higher than M1. The populations of the second cycleselection were significantly higher than their initial population M1, but no significantdifference among them. The boll size, seed index, the percent of the first harvest yield,fiber length, strength and elongation of the resistant plants to bollworm were significantlylower than that of sensitive plants to bollworm. And the yield of seed and lint cottonof the resistant plant to bollworm were lower than that of the sensitive to bollworm, butno significant difference between them. The boll numbers per plant, lint percent andmicronaire of the resistant plants to bollworm were significantly higher than that of thesensitive plant to bollworm.

Research Progresses of Sugarcane Brown Rust Resistance Gene and Molecular Markers

Brown rust is a main sugarcane disease in China, affecting stable development of sugarcane industry. Resistance breeding is an effective measure to control sugarcane rust, and looking for diverse sugarcane rust resistance alternative resources is another important way to improve rust resistance level. This article reviewed from the aspects of construction of sugarcane genetic map, research progress of rust resistance gene, development of rust resistance molecular markers, and research strategies of rust resistance gene, in order to provide scientific guidance and reference for rust resistance breeding.

Genetic Diversity in <i>Jatropha platyphylla</i>Accessions Based on Morphological Traits and Inter-Simple Sequence Repeats Molecular Markers

Seven accessions of Jatropha platyphylla were evaluated for their phenotypic traits and genetic diversity using inter-simple sequence repeats (ISSRs). Cluster analyses with nine traits were performed: number of branches per plant;fruit per bunch;bunch per branch;bunch per plant;total seed production;total fruit production, protein content, oil content, and fatty acid profile. Genotypes from Rosario, Sinaloa, Mexico (PR11) yielded the highest values in all traits. The correlation analysis of the quantitative traits showed high correlations between seed and total fruit production (r = 0.99). Unsaturated linoleic acid was the most abundant fatty acid (57.64% - 52.39%). Within a genetic improvement program, two of the most important variables to be considered are oil content and phenotypic characteristics of the plant. J. platyphylla has shown viable selection traits that provide a possibility of producing interspecies hybrids and giving them added value. ISSRs primers generated variable banding patterns that were found to be polymorphic;the polymorphic information content (PIC) of these loci ranged from 0.21 to 0.45 with an average of 0.34. The unweighted pair group method (UPGMA) cluster analysis of the data showed the formation of three groups, where the most divergent accession pair was the genotype from Quelite (QP11) and Rosario (PR11).

Application of Molecular Marker Technology in the Study of Forest Tree Species

Due to its unique advantages, molecular marker technology is widely applied in the research of forest tree species. This paper reviewed the application of molecular marker technology in tree species resource diversity, germplasm identification, genetic map construction, gene mapping and marker-assisted selection (MAS) breeding. In addition, it elaborated the great significance of molecular marker technology to promote the sustainable development of forestry production in China.

Application of Molecular Marker Assisted Selection in Gene Pyramiding and Selection of New Cultivars

The feasibility of molecule markers＇ application in gene pyramiding has been proved,and obvious progresses in crop breeding have been made till now.Furthermore,different QTLs or molecular markers linked tightly to yield,quality or resistance may be used for marker assisted selection.MAS will be applied widely in crop breeding due to the development of more gene-based markers and efficient quantitative trait locus（QTL） as well as lower cost marking systems.

A Review of Molecular Makers Applied in Cowpea （Vigna unguiculata L. Walp.） Breeding

In recent years, with the rapid development of molecular biology, molecular markers have been widely used in genetic breeding of various crops including cowpea. However, molecular researches in cowpea are lack of systematic summary. This review presents an overview of accomplishments on different aspects of molecular markers in cowpea genetic breeding, such as genetic diversity analysis, genetic linkage map construction, QTL mapping, etc. Furthermore, it provides the discussion of some existing problems about molecular markers applied in cowpea breeding and the prospect of the future development. The authors find that SSR is the most frequently used molecular marker, while SNP has not been used in the genetic diversity analysis of cowpea. And the authors also conclude that more QTL of cowpea should be located and more molecular markers linked to resistance gene should be found. This will be useful for scientists and breeders to research cowpea with the aid of molecular markers, thus accelerating improvement of cowpea varieties.

Improving Blast Resistance of a Thermo-Sensitive Genic Male Sterile Rice Line GD-8S by Molecular Marker-Assisted Selection

The broad-spectrum blast resistance gene Pi-1, from donor line BL122, was introduced into a thermo-sensitive genic male sterile rice line GD-8S, which possessed good grain quality but high susceptibility to rice blast, by using backcross breeding and molecular marker-assisted selection. Five elite improved male sterile lines, RGD8S-1, RGD8S-2, RGD8S-3, RGD8S-4 and RGD8S-5, were selected based on the results of molecular marker analysis, spikelet sterility, recovery rate of genetic background and agronomic traits. Thirty-three representative blast isolates collected from Guangdong Province, China were used to inoculate the improved lines and the original line GD-8S artificially. The resistance frequencies of the improved lines ranged from 76.47% to 100%, much higher than that of the original line GD-8S （9.09%）. On the agronomic characters, there were no significant differences between the improved lines and GD-8S except for flag leaf length and panicle number per plant. The improved lines could be used for breeding hybrid rice with high blast resistance.

Development of anthracnose disease resistance and heat tolerancechili through conventional breeding and molecular approaches:a review

Chili(Capsicum annuum L.)is the popular spicy vegetable crops belonging to family Solanaceae.Chili peppers are known for their pungency characteristic due to the presence of capsaicinoids that classifies them into hot or sweet pepper.Chili is used as spices,folk remedies for diseases,vegetables,and coloring agent showing a diverse role in human’s life.However,its production is hampered by different biotic stress and abiotic factors.Similarly,the unavailability of high yielding varieties,high temperature,and disease incidence,particularly,anthracnose disease,are the major constraints responsible for the low production of chili pepper.The advents of molecular markers,advancement in quantitative trait loci by classical genetic analysis,and conventional breeding have shown the number of genes for many important and major traits.While the newly developed genotyping technologies and nextgeneration sequencing have led to the discovery of molecular basis for economic important characters in the chili genome and generate large scale data for genomic resources.Based on this background,this review summarizes progress in the development of anthracnose disease-resistant and heat-tolerant chili genotypes through conventional breeding and molecular approaches.This review would help plant breeders in understanding the phenotypic and genetic make-up of capsicum genotypes and provides opportunities for pyramiding two respected genes with the help of diversified phenotypic and molecular marker evaluation.

Low-Cost Strategies for Development of Molecular Markers Linked to Agronomic Traits in<i>Prunus</i>

Evaluation of agronomic traits in Prunus breeding programs is a tedious process because of the long juvenile period of trees, the influence of juvenility and the existence of climatic factors affecting the expression of the trait. For these reasons, marker-assisted selection (MAS) strategies are particularly useful in these cases. The objective of this work is the analysis of alternative low- cost strategies for development of molecular markers linked to agronomic traits in Prunus including the application of modified Bulked segregant analysis (BSA) using Simple sequence repeat (SSRs) markers and the application of Random amplified polymorphism microsatellite (RAMP) markers. First BSA results showed that two SSR loci were found to be tightly linked to flowering time in almond. On the other hand, RAMP analysis has been demonstrated to be a potentially valuable molecular marker for the study of genetic relationships in Prunus. Results showed the dominant nature of these markers with a great abundance and transferability although with a reduced polymorphism. In addition, RAMP application in F1 progenies showed its suitability for molecular characterization and mapping, and later Quantitative trait loci (QTL) or BSA analysis.

Progress and perspective on cotton breeding in Pakistan

Cotton is the prime natural fiber with economic significance globally.Cotton farming and breeding have a long his-tory in Pakistan.The development of high yielding upland cotton(Gossypium hirsutum)varieties gradually replaced the cultivation of diploid Gossypium species.Climate change along with emergence of new epidemic diseases caused yield loss in recent years.The biotic stress considerably reduced the performance and yield potential of cotton.Suit-able breeding strategies are essential to generate useful genetic variations and to identify desired traits.Conventional breeding has remarkably increased cotton yield and fiber quality,which has cultivated the NIAB-78,S-12,MNH‐786,and FH‐Lalazar like cultivars.However,this phenotypic selection based breeding method has low efficiency to pro-duce stress resilient cotton.The efficiency of traditional breeding has significantly improved by the marker assisted selection technology.Breakthroughs in molecular genetics,bioinformatics analysis,genetic engineering,and genome sequencing have opened new technique routes for cotton breeding.In addition,genetic improvement through quantitative trait loci,transcriptome,and CRISPR/Cas9 mediated genomic editing can provide suitable platform to improve the resistance to stresses induced by bollworms,cotton leaf curl virus,heat,drought,and salt.The approval of transgenic lines harboring triple gene Cry1Ac+Cry2A+GTG are critical for cotton crop.This review has critically discussed the progress and limitations of cotton breeding in Pakistan,and reviewed the utilization of novel genetic variations and selection tools for sustainable cotton production.

Pre-Breeding Genetic Diversity Assessment of Tomato(Solanum lycopersicum L.)Cultivars Based on Molecular,Morphological and Physicochemical Parameters

Appropriate knowledge of the parental cultivars is a pre-requisite for a successful breeding program.This study characterized fruit yield,quality attributes,and molecular variations of ten tomato cultivars during three consecutive generations under greenhouse conditions.Peto 86,Castle Rock,and Red Star cultivars showed the highest fruit yield(kg/plant),total phenolic compounds(TPC),and sap acidity.Principal component analysis categorized the evaluated fruit yield into three groups based on their quality attributes.A robust positive correlation appeared among traits inside each group.A positive correlation was likewise noticed between the first and the second groups.However,a negative correlation was detected between the first,the second and the third group.Molecular profiling,using seven inter-simple sequence repeat(ISSR)primers,produced 60 loci,including 49 polymorphic loci.The molecular analysis also pinpointed the highest genetic similarity(0.92)between P73 and Moneymaker,while the lowest genetic similarity(0.46)was observed between Castle Rock and Moneymaker.The cultivars P73 and Moneymaker showed the lowest genetic distance(2.24),while the highest genetic distance(5.92)was observed between Super Marmand and Peto86,on the one hand,and between Castle Rock and Moneymaker,on the other hand.The chemical analysis of fruit sap indicated the highest levels of TPC,total flavonoids,anthocyanin,ascorbic acid and total soluble solids in Peto 86 and Castle Rock cultivars.Phylogeny analysis of tomato cultivars based on morphological and molecular attributes indicated four distinct clades.Peto 86,Castle Rock,and Red star cultivars can be recommended for the tomato hybridization breeding programs in the future,with other tomato cultivars as potentially high-yielding parents.

Genetic and genomic analyses for economically important traits and their applications in molecular breeding of cultured fish

The traits of cultured fish must continually be genetically improved to supply high-quality animal protein for human consumption.Economically important fish traits are controlled by multiple gene quantitative trait loci(QTL),most of which have minor effects,but a few genes may have major effects useful for molecular breeding.In this review,we chose relevant studies on some of the most intensively cultured fish and concisely summarize progress on identifying and verifying QTLs for such traits as growth,disease and stress resistance and sex in recent decades.The potential applications of these major-effect genes and their associated markers in marker-assisted selection and molecular breeding,as well as future research directions are also discussed.These genetic and genomic analyses will be valuable for elucidating the mechanisms modulating economically important traits and to establish more effective molecular breeding techniques in fish.

Databasing Molecular Identities of Sugarcane (Saccharum spp.) Clones Constructed with Microsatellite (SSR) DNA Markers

This paper reports the development of the first SSR marker-based sugarcane (Saccharum spp.) molecular identity database in the world. Since 2005, 1,025 sugarcane clones were genotyped, including 811 Louisiana, 45 Florida, 39 Texas, 130 foreign, and eight consultant/seed company clones. Genotyping was done on a fluorescence-capillary electrophoresis detection platform involving 21 highly polymorphic SSR markers that could potentially amplify 144 distinctive DNA fragments. Genotyping data were processed with the GeneMapper? software to reveal electrophoregrams that were manually checked against the 144 fragments. The presence (A) or absence (C) of these 144 fragments in any sugarcane clone was recorded in an affixed sequence order as a DNAMAN? file to represent its molecular identity being achieved into a local molecular identity database. The molecular identity database has been updated annually by continued genotyping of newly assigned sugarcane clones. The database provides molecular descriptions for new cultivar registration articles, enables sugarcane breeders to identify mis-labeled sugarcane clones in crossing programs and determine the paternity of cross progeny, and ensures the desired cultivars are grown in farmers’ fields.

Molecular characterization of Cuban endemism Carica cubensis Solms using random amplified polymorphic DNA (RAPD) markers

The objective of this work is to present an appropriate set of RAPD (random amplified polymorphic DNA) markers using single and multiplex PCR analysis suitable for the characterization of the endemic Cuban species Carica cubensis and the establishment of genetic relationships with the cultivated species Carica papaya. RAPD markers presented a high level of polymorphism. In addition, the incorporation of more than one RAPD primer in the PCR analysis increased the number of obtained bands and the polymorphism of these bands. A total of 73 RAPD bands were detected (45 of them polymorphic) with the nine RAPD markers assayed using single and multiplex PCR analysis. Results demonstrated a reduced genetic variability within the tested Carica cubensis accessions. The observed clustering in this species could be better explained according to geographic proximity and can indicate the similar precedence of the isolated studied populations. C. cubensis seem to be subspecies of C. papaya adapted to the environmental conditions of the mountains of Cuba or a endemic species close to C. papaya. The implications of these results in the creation of effective germplasm core collection in Carica species have been also discussed.

Molecular Markers of Fat and Inosinic Acid Content in Sheep Muscle and Application

This study was conducted to speed up the process of improving the quality of lamb breeds in China,and to solve the problems that restrict the development of lamb breeds in China,such as low quality of lamb breeds,low meat production rate,and poor meat quality.By studying molecular markers of fat content in sheep muscles,we searched for polymorphic loci related to fat content in sheep muscles on the ANGPTL4 gene.Among the 9 polymorphic loci retrieved,ANGPTL4 was found.Two polymorphic sites,C724 A and A601 G,were significantly associated with intramuscular fat in mutton.In summary,these two molecular markers can be used as a molecular marker reference when breeding high-quality meat or hair and meat using German Merino sheep breeds.

小麦条锈病抗性基因定位及分子标记技术研究进展

条锈病流行对小麦生产造成巨大损失,选育和种植持久抗性品种是防治小麦条锈病最经济有效的策略。为达到多基因聚合培育持久抗病品种的目标,必须不断发掘抗病种质、解析其抗病遗传机制并开发分子标记。基于文献,对条锈病抗性基因发掘涉及的抗病性、分子标记、基因定位方法和定位进展及其在育种中的应用进行了综述,明确了小麦条锈病基因定位涉及技术的现状、局限性及优势,从而为后续的条锈病抗性基因发掘、多基因聚合和持久抗性小麦品种的选育与生产布局提供技术指导,以降低西北麦区和小麦主产区条锈病流行的频率,进一步促进国家粮食安全。