Molecular breeding

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

In silico guided structural and functional analysis of genes with potential involvement in resistance to coffee leaf rust: A functional marker based approach.

Abstract: Physiology-based differentiation of SH genes and Hemileia vastatrix races is the principal method employed for the characterization of coffee leaf rust resistance. Based on the gene-for-gene theory, nine major rust resistance genes (SH1-9) have been proposed. However, these genes have not been characterized at the molecular level. Consequently, the lack of molecular data regarding rust resistance genes or candidates is a major bottleneck in coffee breeding. To address this issue, we screened a BAC library with resistance gene analogs (RGAs), identified RGAs, characterized and explored for any SH related candidate genes. Herein, we report the identification and characterization of a gene (gene 11), which shares conserved sequences with other SH genes and displays a characteristic polymorphic allele conferring different resistance phenotypes. Furthermore, comparative analysis of the two RGAs belonging to CC-NBS-LRR revealed more intense diversifying selection in tomato and grape genomes than in coffee. For the first time, the present study has unveiled novel insights into the molecular nature of the SH genes, thereby opening new avenues for coffee rust resistance molecular breeding. The characterized candidate RGA is of particular importance for further biological function analysis in coffee.

Molecular Breeding of Cotton

Abstract: Molecular characterization provides comprehensive information about the extent of genetic diversity, it assists for the development of an effective, highly accurate, and rapid marker‐assisted cotton breeding program. Due to one of the world’s leading fiber crops, molecular studies of cotton are being explored widely by cotton researchers. Cotton provides raw material to the textile industry among other products. Limitations in conventional breeding program for genetic improvement are due to the complexity and limited knowledge on economically important traits. The use of molecular markers for the detection and exploitation of DNA polymorphism is one of the most significant developments in molecular genetics. In the present scenerio, cotton molecular breeding has become a reliable source through the study and exploitation of its genetic diversity and due to better understanding of the cotton genomes using the next‐generation sequencing technologies. Cotton breeders should utilize genomics in breeding programs for effective selection of best parents for agronomic and fiber‐related traits, as well as for the development of resistance against biotic and abiotic stresses. The genomic research work could be based upon genotyping using DNA markers, quantitative trait loci mapping, genome‐wide associations, and next‐generation sequencing. The objective of this chapter is to describe evolution as well as utilization of various molecular markers and review the contribution of marker‐assisted selection (MAS) in cotton breeding.

Genetic Markers, Trait Mapping and Marker-Assisted Selection in Plant Breeding

Abstract: Genetic markers have long been used for characterization of plant genetic diversity and exploitation in crop improvement. The advent of DNA marker technology (during 1980s) has revolutionized crop breeding research as it has enabled the breeding of elite cultivars with targeted selection of desirable gene or gene combinations in breeding programmes. DNA markers are considered better over traditional morphology and protein-based markers because they are abundant, neutral, reliable, convenient to automate and cost-effective. Over the years, DNA marker technology has matured from restriction based to PCR based to sequence based and to eventually the sequence itself with the emergence of novel genome sequencing technologies. Trait mapping has been the foremost application of molecular markers in plant breeding. Genomic locations of numerous genes or quantitative trait loci (QTLs) associated with agronomically important traits have been determined in several crop plants using linkage or association mapping approaches. Plant breeders always look for an easy, rapid and reliable method of selection of desirable plants in breeding populations. Conventionally, desirable plants are selected based on phenotypic observations. The phenotypic selection for complex agronomic traits is difficult, unpredictable and challenging. Once the marker-trait association is correctly established, the gene- or QTL-linked markers can be used to select plants carrying desirable traits, the process called marker-assisted selection (MAS). Marker-assisted backcrossing (MABC) has been widely used for transferring single major gene or combination of major genes into the background of elite cultivar; the process refers to gene pyramiding. Marker-assisted recurrent selection (MARS) and genome-wide association analysis (GWA) are considered potential MAS strategies for improvement of complex traits but still remain as theoretical possibilities in plant breeding. Though molecular markers and MAS have promises for improved plant breeding process, the marker-trait associations or QTLs are statistical associations, which are influenced by several factors such as trait heritability, phenotyping methods, marker density, population type and other experimental conditions that might lead to false positives. Therefore, a cautiously optimistic approach is necessary to consider MAS in crop breeding programmes. In this chapter, the potentials of genetic markers in plant breeding are described.

Identification and validation of breeder-friendly DNA markers for Pl arg gene in sunflower

Abstract: Downy mildew is a fungal disease of sunflower that can lead to severe yield losses The damage caused by the pathogen can be controlled by growing resistant sunflower varieties Gene Pl arg was introgressed into cultivated sunflower from the wild species Helianthus argophyllus and provides resistance against all known downy mildew races In this study, we used a mapping population from the cross-RHA 419/RHA-N-49 We identified a new co-segregating simple sequence repeat marker ORS675 and confirmed the co-segregation of markers ORS716 and ORS662 with Pl arg gene The markers were validated on two registered resistant inbred lines RHA 443 and RHA 464, as well as on twenty inbred lines RH 1–20 obtained through methods of classical breeding Molecular marker ORS716 was assessed for usefulness in selecting resistant progeny in 12 BC populations Markers were found to be valuable for molecular breeding in diverse genetic backgrounds and enabled transfer of the resistance gene in different sunflower genotypes

Identification of a Novel Specific Cucurbitadienol Synthase Allele in Siraitia grosvenorii Correlates with High Catalytic Efficiency.

Abstract: Mogrosides, the main bioactive compounds isolated from the fruits of Siraitia grosvenorii, are a group of cucurbitane-type triterpenoid glycosides that exhibit a wide range of notable biological activities and are commercially available worldwide as natural sweeteners. However, the extraction cost is high due to their relatively low contents in plants. Therefore, molecular breeding needs to be achieved when conventional plant breeding can hardly improve the quality so far. In this study, the levels of 21 active mogrosides and two precursors in 15 S. grosvenorii varieties were determined by HPLC-MS/MS and GC-MS, respectively. The results showed that the variations in mogroside V content may be caused by the accumulation of cucurbitadienol. Furthermore, a total of four wild-type cucurbitadienol synthase protein variants (50R573L, 50C573L, 50R573Q, and 50C573Q) based on two missense mutation single nucleotide polymorphism (SNP) sites were discovered. An in vitro enzyme reaction analysis indicated that 50R573L had the highest activity, with a specific activity of 10.24 nmol min−1 mg−1. In addition, a site-directed mutant, namely, 50K573L, showed a 33% enhancement of catalytic efficiency compared to wild-type 50R573L. Our findings identify a novel cucurbitadienol synthase allele correlates with high catalytic efficiency. These results are valuable for the molecular breeding of luohanguo.