Molecular breeding

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

Enhancing onion breeding using molecular tools

Abstract: Bulb onion (Allium cepa L.) is an ancient crop that is thought to have originated in Central Asia and has been cultivated for over 5000 years. Classical genetic and plant breeding approaches have been used to improve onion yield, quality, and resistance against biotic and abiotic stresses. However, its biennial life cycle, cross-pollinated nature and high inbreeding depression have proved challenging for the characterization and breeding of improved traits. New technologies, notably next-generation sequencing, are providing researchers with the genomic resources and approaches to overcome these challenges. Using these genomic technologies, molecular markers are being rapidly developed and utilized for germplasm analysis and mapping in onion. These new tools and knowledge are allowing the integration of molecular and conventional breeding to speed up onion improvement programmes. In this review, we outline recent progress in onion genomics and molecular genetics and prospects for enhancing onion yield and quality in the future.

Impact of plant breeding on genetic diversity of agricultural crops: searching for molecular evidence

Abstract: There is a long-standing concern that modern plant breeding reduces crop genetic diversity, which may have consequences for the vulnerability of crops to changes in pests, diseases, climate and agricultural practices. Recent molecular assessments of genetic diversity changes in existing genepools of major agricultural crops may shed some light on the impact of plant breeding on crop genetic diversity. Reviewing published assessments revealed different impacts of plant breeding on improved genepools, not only narrowing or widening their genetic base, but also shifting their genetic background. In general, the genome-wide reduction of crop genetic diversity accompanying genetic improvement over time is minor, but allelic reduction at individual chromosomal segments is substantial. More efforts are needed to assess what proportion of lost alleles is associated with undesirable traits.

Allele-specific marker-based assessment revealed that the rice blast resistance genes Pi2 and Pi9 have not been widely deployed in Chinese indica rice cultivars

Abstract: The most sustainable approach to control rice blast disease is to develop durably resistant cultivars. In molecular breeding for rice blast resistance, markers developed based on polymorphisms between functional and non-functional alleles of resistance genes, can provide precise and accurate selection of resistant genotypes without the need for difficult, laborious and time-consuming phenotyping. The Pi2 and Pi9 genes confer broad-spectrum resistance against diverse blast isolates. Development of allele-specific markers for Pi2 and Pi9 would facilitate breeding of blast resistant rice by using the two blast resistance genes. In this work, we developed two new markers, named Pi9-Pro and Pi2-LRR respectively, targeting the unique polymorphisms of the resistant and susceptible alleles of Pi2 and of Pi9. The InDel marker Pi9-Pro differentiates three different genotypes corresponding to the Pi2/Piz-t, Pi9 and non-Pi2/Piz-t/Pi9 alleles, and the CAPS marker Pi2-LRR differentiates the Pi2 allele from the non-Pi2 allele. Based on the two newly developed markers and two available markers Pi2SNP and Pi9SNP, the presence of Pi2 and Pi9 was assessed in a set of 434 rice accessions consisting of 377 Chinese indica cultivars/breeding materials and 57 Chinese japonica cultivars/breeding materials. Of the 434 accessions tested, while one indica restorer line Huazhan was identified harboring the Pi2 resistance allele, no other rice line was identified harboring the Pi2 or Pi9 resistance alleles. Allele-specific marker-based assessment revealed that Pi2 and Pi9 have not been widely incorporated into diverse Chinese indica rice cultivars. Thus, the two blast resistance genes can be new gene sources for developing blast resistant rice, especially indica rice, in China. The two newly developed markers should be highly useful for using Pi2 and Pi9 in marker-assisted selection (MAS) breeding programs.