Molecular breeding

About: Molecular breeding is a research topic. Over the lifetime, 2120 publications have been published within this topic receiving 56908 citations.

Molecular Breeding Using a Major QTL for Fusarium Head Blight Resistance in Wheat

Abstract: The difficulties of breeding for Fusarium head blight (caused by Fusarium graminearum Schwabe [teleomorph: Gibberella zeae]) resistance, a quantitatively inherited fungal disease, caused us to initiate a marker-assisted selection (MAS) approach to accelerate our gains from selection. Although MAS for simply inherited traits has become commonplate in many plant breeding programs, there are few examples of its application with quantitatively inherited traits. Several barriers to MAS for a quantitative trait locus (QTL) must be addressed before it can be integrated into a breeding program, including (i) its efficiency or gain compared to phenotypic selection; (ii) the usefulness of markers in breeding-relevant populations; and (iii) the cost, throughput, and expertise required. We identified a major QTL, Fhb1, for Fusarium head blight resistance in wheat (Triticum aestivum L.) and validated its effect in an additional mapping population and near-isogenic lines developed from segregating lines in our breeding program. The effect of this QTL was large and consistent enough to justify complementing our extensive phenotypic screening efforts for this disease with MAS for this major QTL. Fhb1 is located in a highly polymorphic region, and we developed highly diagnostic markers while fine mapping this QTL. The establishment of the USDA-ARS Regional Small Grains Genotyping Centers has dramatically increased our capabilities to apply MAS by providing access to high-throughput DNA extraction and genotyping equipment. Because a limited number of induvidual can be can be subjected to MAS, we use a process of retrospective breeding to identify those populations that are most likely to produce cultivar candidates. More efficient DNA extraction technologies and marker platforms will allow us to fully implement MAS in breeding programs.

Molecular tools for characterization of rice blast pathogen (Magnaporthe grisea) population and molecular marker-assisted breeding for disease resistance

Abstract: Rice blast caused by the fungal pathogen, Magnaporthe grisea (anamorph: Pyricularia grisea) limits rice yield in all major rice-growing regions of the world, especially in irrigated lands and dry upland environments where predisposition factors favour disease development to epidemic proportions. Deployment of host resistance is by far the most effective means of control. The dynamic evolution of the blast fungus in response to different rice genotypes complicates breeding for blast resistance. In order to prolong the useful life of resistance genes, a knowledge of population genetics and evolutionary biology of the pathogen is r equired. The population structure and virulence composition of the blast fungus have been analysed in terms of genetic diversity, fertility and virulence characteristics. A global atlas of M. grisea and a rice blast database have been constructed based on the information. This report discusses the molecular tools that have been used for characterizing M. grisea populations in epidemic areas and describes how the molecular data generated through these methods are linked to breeding for durable blast resistance. Molecular breeding approach has been deployed in several countries across the world including India for the improvement of blast resistance in high-yielding commercial rice cultivars.

Improving Lives: 50 Years of Crop Breeding, Genetics, and Cytology (C‐1)

Abstract: During the past 50 yr, we have witnessed a revolution in the science of plant breeding, genetics, and cytology, and its impact on human lives (e.g., the Green Revolution). Because of increased productivity, breeding objectives evolved from predominantly improving yield to include greater quality and value-added traits. The discovery of the chemical nature of deoxyribonucleic acid (DNA), coupled with Mendelian genetics led to the refinement of quantitative genetics, the robust use of molecular markers, and transgenic crop plants. Cytogenetics elucidated the physical structure of chromosomes, aided trait and molecular mapping, and greatly enhanced the exploitation of genetic variation from wild relatives, as have transgenes and mutations. The fundamental process of selection has been improved by a better understanding of gene action, when to select, and better methods to select plants and analyze their relationship to the environments in which they grow. Single-seed descent plant breeding methods were popularized and evolved to doubled haploid breeding. Plant breeding, genetics, and cytology remain impact sciences that will continue to improve lives as part of the Evergreen Revolution.

Molecular breeding in the genus Musa: a strong case for STMS marker technology

Abstract: Musa species are among the tallest monocotyledons and include major food-producing species. The principal cultivars, derived from two major species Musa acuminata (‘A’ genome) and Musa balbisiana (‘B’ genome), are polyploid hybrids (mainly AAA, AAB and ABB triploids), medium to highly sterile, parthenocarpic and clonally propagated. Bananas and plantains are crops to which molecular breeding is expected to have a positive impact. In order to better understand banana genetics, more knowledge has to be accumulated about the complex genome structure of hybrids and cultivars. Therefore, the aim of our work is to develop molecular markers that are codominant, reliable, universal, highly polymorphic and that are applicable to collaborative Musa germplasm genotyping and mapping. Two size-selected genomic libraries have been screened for the presence of simple sequence repeats (SSR). Our data demonstrate that SSR are readily applicable to the study of Musa genetics. Our comprehensive analyses of a significant number of banana sequence tagged microsatellite sites (STMS) will add to our knowledge on the structure and phylogeny of genomes of the Musa species, and suggest that microsatellites be used as anchor markers for a banana genetic core map. Additional markers, such as e.g. CAPS have also been tested in order to increase the detection of polymorphisms exceeding that revealed by STMS technology. The utility of PCR-derived markers for collaborative genetic analyses of the banana genome, and the transferability of 'streamlined’ laboratory techniques and data analysis to Developing Countries are discussed.

Increased Genomic Prediction Accuracy in Wheat Breeding Through Spatial Adjustment of Field Trial Data

Abstract: In crop breeding, the interest of predicting the performance of candidate cultivars in the field has increased due to recent advances in molecular breeding technologies. However, the complexity of the wheat genome presents some challenges for applying new technologies in molecular marker identification with next-generation sequencing. We applied genotyping-by-sequencing, a recently developed method to identify single-nucleotide polymorphisms, in the genomes of 384 wheat (Triticum aestivum) genotypes that were field tested under three different water regimes in Mediterranean climatic conditions: rain-fed only, mild water stress, and fully irrigated. We identified 102,324 single-nucleotide polymorphisms in these genotypes, and the phenotypic data were used to train and test genomic selection models intended to predict yield, thousand-kernel weight, number of kernels per spike, and heading date. Phenotypic data showed marked spatial variation. Therefore, different models were tested to correct the trends observed in the field. A mixed-model using moving-means as a covariate was found to best fit the data. When we applied the genomic selection models, the accuracy of predicted traits increased with spatial adjustment. Multiple genomic selection models were tested, and a Gaussian kernel model was determined to give the highest accuracy. The best predictions between environments were obtained when data from different years were used to train the model. Our results confirm that genotyping-by-sequencing is an effective tool to obtain genome-wide information for crops with complex genomes, that these data are efficient for predicting traits, and that correction of spatial variation is a crucial ingredient to increase prediction accuracy in genomic selection models.