Showing papers on "Molecular breeding published in 2011"

Diversity Arrays Technology (DArT) and next-generation sequencing combined: genome-wide, high throughput, highly informative genotyping for molecular breeding of Eucalyptus

Abstract: Background Wider genome coverage and higher throughput genotyping methods have become increasingly important to meet the resolution and speed necessary for a variety of applications in genomics and molecular breeding of forest trees. Developed more than 10 years ago [1], the Diversity Arrays Technology (DArT) has experienced an increasing interest worldwide for it has efficiently satisfied the requirements of throughput, genome coverage and inter-specific transferability for over 40 different plant species to date, including Eucalyptus[2] and recently Pinus (Dione Alves-Freitas, this meeting). DArT is based on genome complexity reduction using restriction enzymes, followed by hybridization to microarrays to simultaneously assay hundreds to thousands of markers across a genome. Genome complexity reduction for genotyping has now been taken to another level when combined to next generation sequencing (NGS) technologies. Such a strategy has been used for rapid SNP discovery in different organisms [3], and proposed as a way to genotype with RAD (Restriction-associated DNA) sequencing [4]and recently by a similar method generally termed GbS (Genotyping-by-Sequencing)[5]. In this work we assessed the power of the now well established DArT marker platform in combination with Illumina short read sequencing to generate a linkage map for a segregating outcrossed F1 population derived from E. grandis BRASUZ1, the donor of the Eucalyptus reference genome.

Mutagenesis as a tool in plant genetics, functional genomics, and breeding.

Abstract: Plant mutagenesis is rapidly coming of age in the aftermath of recent developments in high-resolution molecular and biochemical techniques. By combining the high variation of mutagenised populations with novel screening methods, traits that are almost impossible to identify by conventional breeding are now being developed and characterised at the molecular level. This paper provides a comprehensive overview of the various techniques and workflows available to researchers today in the field of molecular breeding, and how these tools complement the ones already used in traditional breeding. Both genetic (Targeting Induced Local Lesions in Genomes; TILLING) and phenotypic screens are evaluated. Finally, different ways of bridging the gap between genotype and phenotype are discussed.

Towards marker-assisted selection in pulses: a review

Abstract: With 2 figures and 2 tables Abstract Pulses are important sources of proteins in vegetarian diet. However, genetic improvement in production and productivity of pulse crops has been very slow owing to several constraints. The present view of researchers is that the effectiveness and efficiency of conventional breeding can be significantly improved by using molecular markers. Nowadays, molecular markers are routinely utilized worldwide in all major crops as a component of breeding. The pace of development of molecular markers and other genomic sources has been accelerated in chickpea, pigeon pea and some other pulses, and marker–trait associations have been established for a number of important agronomic traits. The efforts are underway to use high-throughput genotyping platforms besides developing more genomic resources in other pulses. So far, progress in the use of marker-assisted selection as a part of pulse breeding programmes has been very slow and limited to few pulse crops such as chickpea and common bean. In this article, we have reviewed the progress made, limitations encountered and future possibilities for the application of marker-assisted selection in the genetic improvement of pulse crops.

Analysis of BAC-end sequences (BESs) and development of BES-SSR markers for genetic mapping and hybrid purity assessment in pigeonpea (Cajanus spp.)

Abstract: Background: Pigeonpea [Cajanus cajan (L.) Millsp.] is an important legume crop of rainfed agriculture. Despite of concerted research efforts directed to pigeonpea improvement, stagnated productivity of pigeonpea during last several decades may be accounted to prevalence of various biotic and abiotic constraints and the situation is exacerbated by availability of inadequate genomic resources to undertake any molecular breeding programme for accelerated crop improvement. With the objective of enhancing genomic resources for pigeonpea, this study reports for the first time, large scale development of SSR markers from BAC-end sequences and their subsequent use for genetic mapping and hybridity testing in pigeonpea. Results: A set of 88,860 BAC (bacterial artificial chromosomes)-end sequences (BESs) were generated after constructing two BAC libraries by using HindIII (34,560 clones) and BamHI (34,560 clones) restriction enzymes. Clustering based on sequence identity of BESs yielded a set of >52 K non-redundant sequences, comprising 35 Mbp or >4% of the pigeonpea genome. These sequences were analyzed to develop annotation lists and subdivide the BESs into genome fractions (e.g., genes, retroelements, transpons and non-annotated sequences). Parallel analysis of BESs for microsatellites or simple sequence repeats (SSRs) identified 18,149 SSRs, from which a set of 6,212 SSRs were selected for further analysis. A total of 3,072 novel SSR primer pairs were synthesized and tested for length polymorphism on a set of 22 parental genotypes of 13 mapping populations segregating for traits of interest. In total, we identified 842 polymorphic SSR markers that will have utility in pigeonpea improvement. Based on these markers, the first SSR-based genetic map comprising of 239 loci was developed for this previously uncharacterized genome. Utility of developed SSR markers was also demonstrated by identifying a set of 42 markers each for two hybrids (ICPH 2671 and ICPH 2438) for genetic purity assessment in commercial hybrid breeding programme. Conclusion: In summary, while BAC libraries and BESs should be useful for genomics studies, BES-SSR markers, and the genetic map should be very useful for linking the genetic map with a future physical map as well as for molecular breeding in pigeonpea

A unifying theory for general multigenic heterosis: energy efficiency, protein metabolism, and implications for molecular breeding

Abstract: Hybrids between genetically diverse varieties display enhanced growth, and increased total biomass, stress resistance and grain yield. Gene expression and metabolic studies in maize, rice and other species suggest that protein metabolism plays a role in the growth differences between hybrids and inbreds. Single trait heterosis can be explained by the existing theories of dominance, overdominance and epistasis. General multigenic heterosis is observed in a wide variety of different species and is likely to share a common underlying biological mechanism. This review presents a model to explain differences in growth and yield caused by general multigenic heterosis. The model describes multigenic heterosis in terms of energy-use efficiency and faster cell cycle progression where hybrids have more efficient growth than inbreds because of differences in protein metabolism. The proposed model is consistent with the observed variation of gene expression in different pairs of inbred lines and hybrid offspring as well as growth differences in polyploids and aneuploids. It also suggests an approach to enhance yield gains in both hybrid and inbred crops via the creation of an appropriate computational analysis pipeline coupled to an efficient molecular breeding program.

The Transcriptome of the Reference Potato Genome Solanum tuberosum Group Phureja Clone DM1-3 516R44.

Abstract: Advances in molecular breeding in potato have been limited by its complex biological system, which includes vegetative propagation, autotetraploidy, and extreme heterozygosity. The availability of the potato genome and accompanying gene complement with corresponding gene structure, location, and functional annotation are powerful resources for understanding this complex plant and advancing molecular breeding efforts. Here, we report a reference for the potato transcriptome using 32 tissues and growth conditions from the doubled monoploid Solanum tuberosum Group Phureja clone DM1-3 516R44 for which a genome sequence is available. Analysis of greater than 550 million RNA-Seq reads permitted the detection and quantification of expression levels of over 22,000 genes. Hierarchical clustering and principal component analyses captured the biological variability that accounts for gene expression differences among tissues suggesting tissue-specific gene expression, and genes with tissue or condition restricted expression. Using gene co-expression network analysis, we identified 18 gene modules that represent tissue-specific transcriptional networks of major potato organs and developmental stages. This information provides a powerful resource for potato research as well as studies on other members of the Solanaceae family.

Breeding tef [Eragrostis tef (Zucc.) trotter]: conventional and molecular approaches

Abstract: With 2 figures and 5 tables Abstract Tef [Eragrostis tef (Zucc.) Trotter] is an important food staple cereal crop in Ethiopia. Despite its importance in the Ethiopian agriculture, there are constraints that need to be addressed through scientific research. The major constraints are low yield of landrace cultivars under widespread cultivation, susceptibility to lodging and a lack of knowledge concerning the genetic control of agronomic traits. Conventional tef breeding efforts started in the late 1950s, and since then a total of 24 varieties have been developed and released. Yield gain from tef breeding has been linear with an average annual increase of 0.8%. Tef genomics has provided much molecular genetic information on important agronomic traits. More than 1500 PCR-based molecular markers have been developed and several genetic linkage maps based on intra- and inter-specific crosses have been constructed. Results from quantitative trait loci studies have provided information necessary for marker-assisted selection. Lodging is the number one cause of yield loss in tef. Recently, molecular breeding techniques and biotechnologies are being employed to understand the genetic control of lodging.

Development and application of a set of breeder-friendly SNP markers for genetic analyses and molecular breeding of rice (Oryza sativa L.).

Abstract: Single nucleotide polymorphisms (SNPs) are the most abundant DNA markers in plant genomes. In this study, based on 54,465 SNPs between the genomes of two Indica varieties, Minghui 63 (MH63) and Zhenshan 97 (ZS97) and additional 20,705 SNPs between the MH63 and Nipponbare genomes, we identified and confirmed 1,633 well-distributed SNPs by PCR and Sanger sequencing. From these, a set of 372 SNPs were further selected to analyze the patterns of genetic diversity in 300 representative rice inbred lines from 22 rice growing countries worldwide. Using this set of SNPs, we were able to uncover the well-known Indica-Japonica subspecific differentiation and geographic differentiations within Indica and Japonica. Furthermore, our SNP results revealed some common and contrasting patterns of the haplotype diversity along different rice chromosomes in the Indica and Japonica accessions, which suggest different evolutionary forces possibly acting in specific regions of the rice genome during domestication and evolution of rice. Our results demonstrated that this set of SNPs can be used as anchor SNPs for large scale genotyping in rice molecular breeding research involving Indica-Japonica and Indica-Indica crosses.

High-throughput SNP genotyping in the highly heterozygous genome of Eucalyptus: assay success, polymorphism and transferability across species.

Abstract: High-throughput SNP genotyping has become an essential requirement for molecular breeding and population genomics studies in plant species. Large scale SNP developments have been reported for several mainstream crops. A growing interest now exists to expand the speed and resolution of genetic analysis to outbred species with highly heterozygous genomes. When nucleotide diversity is high, a refined diagnosis of the target SNP sequence context is needed to convert queried SNPs into high-quality genotypes using the Golden Gate Genotyping Technology (GGGT). This issue becomes exacerbated when attempting to transfer SNPs across species, a scarcely explored topic in plants, and likely to become significant for population genomics and inter specific breeding applications in less domesticated and less funded plant genera. We have successfully developed the first set of 768 SNPs assayed by the GGGT for the highly heterozygous genome of Eucalyptus from a mixed Sanger/454 database with 1,164,695 ESTs and the preliminary 4.5X draft genome sequence for E. grandis. A systematic assessment of in silico SNP filtering requirements showed that stringent constraints on the SNP surrounding sequences have a significant impact on SNP genotyping performance and polymorphism. SNP assay success was high for the 288 SNPs selected with more rigorous in silico constraints; 93% of them provided high quality genotype calls and 71% of them were polymorphic in a diverse panel of 96 individuals of five different species. SNP reliability was high across nine Eucalyptus species belonging to three sections within subgenus Symphomyrtus and still satisfactory across species of two additional subgenera, although polymorphism declined as phylogenetic distance increased. This study indicates that the GGGT performs well both within and across species of Eucalyptus notwithstanding its nucleotide diversity ≥2%. The development of a much larger array of informative SNPs across multiple Eucalyptus species is feasible, although strongly dependent on having a representative and sufficiently deep collection of sequences from many individuals of each target species. A higher density SNP platform will be instrumental to undertake genome-wide phylogenetic and population genomics studies and to implement molecular breeding by Genomic Selection in Eucalyptus.

A first generation microsatellite- and SNP-based linkage map of Jatropha.

Abstract: Jatropha curcas is a potential plant species for biodiesel production. However, its seed yield is too low for profitable production of biodiesel. To improve the productivity, genetic improvement through breeding is essential. A linkage map is an important component in molecular breeding. We established a first-generation linkage map using a mapping panel containing two backcross populations with 93 progeny. We mapped 506 markers (216 microsatellites and 290 SNPs from ESTs) onto 11 linkage groups. The total length of the map was 1440.9 cM with an average marker space of 2.8 cM. Blasting of 222 Jatropha ESTs containing polymorphic SSR or SNP markers against EST-databases revealed that 91.0%, 86.5% and 79.2% of Jatropha ESTs were homologous to counterparts in castor bean, poplar and Arabidopsis respectively. Mapping 192 orthologous markers to the assembled whole genome sequence of Arabidopsis thaliana identified 38 syntenic blocks and revealed that small linkage blocks were well conserved, but often shuffled. The first generation linkage map and the data of comparative mapping could lay a solid foundation for QTL mapping of agronomic traits, marker-assisted breeding and cloning genes responsible for phenotypic variation.

Development and validation of functional marker targeting an InDel in the major rice blast disease resistance gene Pi54 (Pikh)

Abstract: Rice blast is one of the most devastating diseases affecting the rice crop throughout the world. In molecular breeding for host plant resistance, functional markers are very useful for enhancing the precision and accuracy in marker-assisted selection (MAS) of target gene(s) with minimum effort, time and cost. Pi54 (which was earlier known as Pikh) is one of the major blast resistance genes and has been observed to show resistance against many isolates of the blast pathogen in India. The gene has been cloned through map-based strategy and encodes a nucleotide-binding site–leucine-rich repeat (NBS–LRR) domain-containing protein. In the present study, we carried out allele mining for this gene and identified a 144-bp insertion/deletion (InDel) polymorphism in the exonic region of the gene. A PCR-based co-dominant molecular marker targeting this InDel, named Pi54 MAS, was developed. Pi54 MAS was observed to perfectly co-segregate with blast resistance in a mapping population with no recombinants. Validation of this marker in 105 genotypes which are either susceptible or resistant to rice blast disease showed that the marker is polymorphic in most of the resistant–susceptible genotype combinations and is more accurate than the earlier reported markers for Pi54. Hence this functional, co-dominant marker is suggested for routine deployment in MAS of Pi54 in breeding programs.

Biology and breeding of food legumes.

Abstract: 1 History, Origin and Evolution 2 Biology and Floral Morphology 3 Domestication 4 Breeding for Improvement of Cool Season Food Legumes 5 Breeding for Improvement of Warm-season Food Legumes 6 Distant Hybridization and Alien Gene Introgression 7 Polyploidy 8 Cytology and Molecular Cytogenetics 9 Molecular Cytogenetics in Physical Mapping of Alien Introgressions 10 In vitro techniques 11 Microsporogenesis and Haploidy Breeding 12 Genetic Transformation 13 Male Sterility and Hybrid Production Technology 14 Mutagenesis 15 Breeding for Biotic Stresses 16 Breeding for Abiotic Stresses 17 Legume Improvement in the Acidic and less Fertile Soils 18 Genomic Approaches for Management of Abiotic Stresses 19 Molecular Breeding and Marker-assisted Selection 20 Underutilized Food Legumes 21 Legumes as a Model Plant Family 22 Plant Genetic Resources and Conservation of Biodiversity 23 Seed Dormancy and Viability 24 Post Harvest Technology 25 Value Addition and Trade

Molecular approaches to improvement of Jatropha curcas Linn. as a sustainable energy crop

Abstract: With the increase in crude oil prices, climate change concerns and limited reserves of fossil fuel, attention has been diverted to alternate renewable energy sources such as biofuel and biomass Among the potential biofuel crops, Jatropha curcas L, a non-domesticated shrub, has been gaining importance as the most promising oilseed, as it does not compete with the edible oil supplies Economic relevance of J curcas for biodiesel production has promoted world-wide prospecting of its germplasm for crop improvement and breeding However, lack of adequate genetic variation and non-availability of improved varieties limited its prospects of being a successful energy crop In this review, we present the progress made in molecular breeding approaches with particular reference to tissue culture and genetic transformation, genetic diversity assessment using molecular markers, large-scale transcriptome and proteome studies, identification of candidate genes for trait improvement, whole genome sequencing and the current interest by various public and private sector companies in commercial-scale cultivation, which highlights the revival of Jatropha as a sustainable energy crop The information generated from molecular markers, transcriptome profiling and whole genome sequencing could accelerate the genetic upgradation of J curcas through molecular breeding

Application of gene targeting to designed mutation breeding of high-tryptophan rice

Abstract: Site-directed mutagenesis via gene targeting (GT) based on homologous recombination is the ultimate mutation breeding technology because it enables useful information acquired from structural- and computational-based protein engineering to be applied directly to molecular breeding, including metabolic engineering, of crops. Here, we employed this rationale to introduce precise mutations in OASA2—an α-subunit of anthranilate synthase that is a key enzyme of tryptophan (Trp) biosynthesis in rice (Oryza sativa)—via GT, with subsequent selection of GT cells using a Trp analog. The expression level of OASA2 in plants homozygous and heterozygous for modified OASA2 was similar to that of nontransformants, suggesting that OASA2 transcription in GT plants was controlled in the same manner as endogenous OASA2, and that GT could lead to a lower risk of gene silencing than in conventional overexpression approaches. Moreover, we showed that enzymatic properties deduced from protein engineering or in vitro analysis could be reproduced in GT plants as evidenced by Trp accumulation levels. Interestingly, mature seeds of homozygous GT plants accumulated Trp levels 230-fold higher than in nontransformants without any apparent morphological or developmental changes. Thus, we have succeeded in producing a novel rice plant of great potential nutritional benefit for both man and livestock that could not have been selected using conventional mutagenesis approaches. Our results demonstrate the effectiveness of directed crop improvement by combining precision mutagenesis via GT with a knowledge of protein engineering.

Molecular marker-assisted genotyping of mungbean yellow mosaic India virus resistant germplasms of mungbean and urdbean.

Abstract: Mungbean Yellow Mosaic India Virus (MYMIV) belonging to the genus begomovirus causes the yellow mosaic disease in a number of economically important edible grain legumes including mungbean (Vigna radiata), urdbean (Vigna mungo) and soybean (Glycine max). The disease is severe, critical, open spread and inflicts heavy yield losses annually. The objective of this study is to develop molecular markers linked to MYMIV-resistance to facilitate genotyping of urdbean and mungbean germplasms for MYMIV-reaction. Resistance-linked molecular markers were successfully developed from consensus motifs of other resistance (R) gene or R gene homologue sequences. Applying linked marker-assisted genotyping, plant breeders can carry out repeated genotyping throughout the growing season in absence of any disease incidence. Two MYMIV-resistance marker loci, YR4 and CYR1, were identified and of these two CYR1 is completely linked with MYMIV-resistant germplasms and co-segregating with MYMIV-resistant F2, F3 progenies of urdbean. The present study demonstrated that these two markers could be efficiently employed together in a multiplex-PCR-reaction for genotyping both V. mungo and V. radiata germplasms from field grown plants and also directly from the seed stock. This method of genotyping would save time and labour during the introgression of MYMIV-resistance through molecular breeding, as methods of phenotyping against begomoviruses are tedious, labour and time intensive.

Transcriptome Analysis and Functional Genomics of Sugarcane

Abstract: Sugarcane is a genetically complex polyploid with increasing economic importance as a feedstock for biofuel production. The characterization of sugarcane genes and their association with biological traits such as sugar accumulation, biomass yield and stress tolerance has so far primarily relied on studies of the sugarcane transcriptome. Associations of gene expression with biological traits have been based on alterations in the timing and intensity of gene expression with various treatments and developmental stages, and in some instances, by genotypic correlations using segregating populations or genotypes contrasting for traits. The transcriptome of sugarcane is complex and includes transcripts of homo(eo)logues reflecting the highly polyploid genome of commercial sugarcane hybrids derived recently from two Saccharum species. The impact of this genomic complexity on transcription will be greatly informed by data emerging from the International Sugarcane Genome Sequencing Project. Increasingly, expressed gene sequences are exploited as genetic markers for traits in genome mapping and association studies. Reverse genetics approaches are possible in sugarcane but only very few sugarcane genes have had their specific functions examined in transgenic sugarcane plants. An integration of genome, transcriptome and metabolome data is emerging that will inform the molecular breeding of this important sugar and energy crop.

Genetics, genomics and breeding of oilseed brassicas.

Abstract: The book describes the history of Brassica oilseed crops, introduces the Brassica genome, its evolution, diversity, classical genetic studies, and breeding. It also delves into molecular genetic linkage and physical maps, progress with genome sequencing initiatives, mutagenesis approaches for trait improvement, proteomics, metabolomics, and bioinformatics. The concluding portion provides detailed methods for whole genome marker assisted breeding and the genetics and genomics of important traits including disease resistance, herbivory, insect and abiotic stress resistance, and discusses the future prospects for Brassica improvement through genomics. This volume provides a state-of-the-moment view of current Brassica genetics, genomics, and breeding research, which is the foundation for the continued understanding of oilseed Brassica species, their genomes, evolution, and further potential as important food and biofuel crops. [Book summary from publisher]

Efficient production of novel floral traits in torenia by collective transformation with chimeric repressors of Arabidopsis transcription factors

Abstract: Molecular breeding with genetic modification enables the production of novel floral traits in floricultural plants that could not be obtained by traditional breeding. To facilitate novel flower production, we collectively introduced 2 sets of 42 and 50 chimeric repressors of Arabidopsis transcription factors into Agrobacterium and then used these to co-transform torenia (Torenia fournieri). We generated 750 transgenic torenias, and identification of the transgenes revealed that more than 80% of the transgenic torenias had a single transgene. A total of 264 plants showed phenotypic modification, and 91.2% displayed modified flower colors and/or shapes, such as altered color patterns, curled petal margins, and wavy petals. These results indicated that the collective transformation system can be applied to molecular breeding of flowers. Detailed analysis of the phenotypes revealed that PETAL LOSS could control blotch sizes and that modification of cell shape could change the texture of petals. We found that the chimeric repressors of functionally unknown transcription factors also induced novel floral traits, and therefore, the transgenic torenias provide an understanding of the functions of transcription factors that could not be revealed by previous studies in Arabidopsis.

Trait mapping and molecular breeding

Abstract: This chapter provides general concepts of trait mapping and molecular breeding in food legumes, citing the examples of soyabean, common bean and chickpea where development and use of genetic and genomic resources are at an advanced stage.

Marker-assisted selection for quantitative traits

Abstract: Although thousands of scientific articles have been published on the subject of marker-assisted selection (MAS) and quantitative trait loci (QTL), the application of MAS for QTL in plant breeding has been restricted. Among the main causes for this limited use are the low accuracy of QTL mapping and the high costs of genotyping thousands of plants with tens or hundreds of molecular markers in routine breeding programs. Recently, new large-scale genotyping technologies have resulted in a cost reduction. Nevertheless, the MAS for QTL has so far been limited to selection programs using several generations per year, where phenotypic selection cannot be performed in all generations, mainly in recurrent selection programs. Methods of MAS for QTL in breeding programs using self-pollination have been developed.

RMDAP: A Versatile, Ready-To-Use Toolbox for Multigene Genetic Transformation

Abstract: Background The use of transgenes to improve complex traits in crops has challenged current genetic transformation technology for multigene transfer. Therefore, a multigene transformation strategy for use in plant molecular biology and plant genetic breeding is thus needed. Methodology/Principal Findings Here we describe a versatile, ready-to-use multigene genetic transformation method, named the Recombination-assisted Multifunctional DNA Assembly Platform (RMDAP), which combines many of the useful features of existing plant transformation systems. This platform incorporates three widely-used recombination systems, namely, Gateway technology, in vivo Cre/loxP and recombineering into a highly efficient and reliable approach for gene assembly. RMDAP proposes a strategy for gene stacking and contains a wide range of flexible, modular vectors offering a series of functionally validated genetic elements to manipulate transgene overexpression or gene silencing involved in a metabolic pathway. In particular, the ability to construct a multigene marker-free vector is another attractive feature. The built-in flexibility of original vectors has greatly increased the expansibility and applicability of the system. A proof-of-principle experiment was confirmed by successfully transferring several heterologous genes into the plant genome. Conclusions/Significance This platform is a ready-to-use toolbox for full exploitation of the potential for coordinate regulation of metabolic pathways and molecular breeding, and will eventually achieve the aim of what we call “one-stop breeding.”

Beneficial genotype of swine FUT1 gene governing resistance to E. coli F18 is associated with important economic traits.

Abstract: 1Key Laboratory for Animal Genetics, Breeding, Reproduction and Molecular Design of Jiangsu Province, College of Animal Science and Technology, and 2College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu 225009, People’s Republic of China 3Suzhou Taihu Pig Breeding Centre, Jiangsu Province, Suzhou, Jiangsu 215000, People’s Republic of China 4Jiangsu Engineering Research Centre for Molecular Breeding of Pig, Changzhou, Jiangsu 213149, People’s Republic of China

Genetic improvement of cotton tolerance to salinity stress

Abstract: Soil salinity is a great threat to cotton production worldwide. Plant adaptation to environmental stresses involves the expression of specific stress-related genes. Consequently, engineering genes that protect and maintain the function and structure of cellular components can enhance tolerance to salinity stress. Engineered cotton plants have been reported to perform much better than their wilt plants either in greenhouse or field conditions under salinity stress. However, engineered cotton with improved salt-tolerance is still far behind the requirements of commercial production due to its limited salinity tolerance or poor agronomic performance. This review highlights recent advances in genetic improvement, particularly molecular breeding for salinity tolerance of cotton. It is suggested that future research should focus on the development of specific cotton cultivars with high salt tolerance through a combination of traditional breeding and molecular technology.

Breeding for Nematode Resistance: Use of Genomic Information

Abstract: Plant parasitic nematodes are a threat for several important crops. Genetic resistance is the more efficient and the more environmentally friendly way to protect crops against these nematodes. The genetic determinism of resistance to nematodes has been investigated, using DNA-based markers, in the most cultivated host plants. Major genes and Quantitative Trait Loci (QTL) acting on resistance to nematodes have been mapped in 20 crop species. The use of DNA-based markers, linked to nematode resistance genes or QTLs, in breeding programs has been described in Solanaceae, in Prunus, in soybean and in wheat. Six nematode resistance genes have been characterized at the molecular level. A strategy to avoid overcoming resistance genes by nematode populations is proposed.

Specific molecular markers of related genes of brassica napus grain weight and application thereof

Abstract: The invention belongs to the field of rape molecular breeding, and relates to preparation of specific molecular markers of related genes MINI3 and TTG2 of the brassica napus grain weight Double haploid colony (DH) is constructed with brassica napus I A 254 as a female parent and a brassica napus I A 177 as a male parent through hybridization, and the DH colony genotype and the thousand seed weight data are analyzed to obtain a QTLs locus of grain weight character The MINI3 and the TTG2 genes of the IA254 and the IA177 are cloned by using a homology based candidate gene method, specific molecular markers MINI3a and TTG2a of the MINI3 and the TTG2 genes are designed according to sequence different locuses, and the molecular markers MINI3a and TTG2a are located on two grain weight QTLs locus of an A5 linkage colony for related verification and application, which proves that the molecular marker prepared by the invention is a novel genetic marker The gene sequence is obtained firstly The invention provides a novel marker for the molecular breeding of the brassica napus grain weight, and also provides useful information for candidate gene clone and marker auxiliary selection of thethousand seed weight character locuses of the brassica napus