The genetic dissection of quantitative traits in crops

Abstract

Most traits of interest in plant breeding show quantitative inheritance, which complicate the breeding process since phenotypic performances only partially reflects the genetic values of individuals. The genetic variation of a quantitative trait is assumed to be controlled by the collective effects of quantitative trait loci (QTLs), epistasis (interaction between QTLs), the environment, and interaction between QTL and environment. Exploiting molecular markers in breeding involve finding a subset of markers associated with one or more QTLs that regulate the expression of complex traits. Many QTL mapping studies conducted in the last two decades identified QTLs that generally explained a significant proportion of the phenotypic variance, and therefore, gave rise to an optimistic assessment of the prospects of markers assisted selection. Linkage analysis and association mapping are the two most commonly used methods for QTL mapping. This review provides an overview of the two QTL mapping methods, including mapping population type and size, phenotypic evaluation of the population, molecular profiling of either the entire or a subset of the population, marker-trait association analysis using different statistical methods and software as well as the future prospects of using markers in crop improvement.

Chromosomal localization of selected SCARs converted from new RAPD, ISSR and R-ISSR markers linked to rye (Secale cereale L.) tolerance to nutrient deprivation stress identified using bulk segregant analysis

“…Bulk segregant analysis conducted for pooled groups of segregants selected from such populations allows quick and effective identification of markers linked to QTL(s) controlled by major genes (Michelmore et al 1991). The possibility of rapid screening of many loci (Michelmore et al 1991;Soller, 1992, Darvasi andSoller, 1994;Angaji, 2009;Semagn et al 2010), combined with the possibility of the application of markers exploring thus far unexamined chromosome regions, provides the possibility of the identification of a new range of variability as well as markers linked to the identified QTL(s) (Ye et al 2005;Saleh, 2011;Smolik et al 2012;Smolik, 2013b).…”

“…On the basis of excellent reviews characterizing the methods of bulk segregant analysis and selective genotyping, Darvasi and Soller (1992), Darvasi and Soller (1994), Gallais et al (2007), Angaji (2009), andSemagn et al (2010), emphasize overlapping methodological similarity, the role of description of allele frequency in pooled DNA samples, the kind of population, tail number and methodological limitations (Xu and Crouch, 2008). BSA has been successfully used in the mapping of single major genes (Barua et al 1993;Villar et al 1996;Quarrie et al 1999;Shen et al 2003), but a combination of BSA and the candidate genes approach could be very effective in discovering genes with a significant effect on QTLs (Angaji, 2009).…”

PCR, sequencing and PCR–RFLP of the 5S‐rRNA‐NTS region as a tool for the DNA fingerprinting of medicinal and aromatic plants

“…[20] The development and use of molecular markers for the detection and exploitation of DNA polymorphism is one of the most signifi cant developments in the fi eld of molecular genetics. [21] DNA markers can identify the organism and its taxonomic association, even from fragmentary remains and even where morphology cannot distinguish strains. [15] Polymorphic markers can defi ne a multilocus genotype characteristic for an individual or a clone; selected markers can be diagnostic for a population or a species.…”

Genetic structure and diversity of a soybean germplasm considering biological nitrogen fixation and protein content

“…BNF has often been excluded from consideration in plant breeding programs mainly due to the difficulty of evaluating phenotypic traits as nodulation. However, molecular tools may be used to overcome this evaluation limitation (Semagn et al, 2010).…”