Molecular-marker-facilitated investigations of quantitative trait loci in maize

Abstract

Restriction fragment length polymorphisms have become powerful tools for genetic investigations in plant species. They allow a much greater degree of genome saturation with neutral markers than has been possible with isozymes or morphological loci. A previous investigation employed isozymes as genetic markers to infer the location of genetic factors influencing the expression of quantitative traits in the maize population: (CO159×Tx303)F2. This investigation was conducted to examine the inferences that might be derived using a highly saturated map of RFLP markers and isozymes to detect quantitative trait loci (QTLs) in the same maize F2 population. Marker loci that were associated with QTL effects in this investigation generally corresponded well with previous information where such comparisons were possible. Additionally, a number of previously unmarked genomic regions were found to contain factors with large effects on some plant traits. Availability of numerous marker loci in some genomic regions allowed: more accurate localization of QTLs, resolution of linkage between QTLs affecting the same traits, and determination that some chromsome regions previously found to affect a number of traits are likely to be due to linkage of QTLs affecting different traits. Many of the factors that affected plant height quantitatively in this investigation were found to map to regions also including known sites of major genes influencing plant height. Although the data are not conclusive, they suggest that some of the identified QTLs may be allelic to known major genes affecting plant height.

Variation in ITGB3 is associated with whole-blood serotonin level and autism susceptibility

“…In three samples, serotonin levels were associated with noncoding SNPs that account for 7 -10% of the population variance in their respective samples. Extrapolating from studies of quantitative traits in model organisms in which most QTLs have effect sizes less than 5%, 39 we predict that the ITGB3 effect sizes observed in our study contribute substantively to interindividual variation in serotonin level in multiple populations. Surprisingly, noncoding polymorphisms were more strongly associated with serotonin level than Leu33Pro in the Hutterites, Chicago controls, and the Chicago autism sample.…”

Identification of SSR markers associated with seed coat permeability and electrolyte leaching in soybean

“…The linkage relationship among the markers was established using the computer package MAPMAKER/EXP 3.0 (Lander et al, 1987;Lincoln et al, 1992). To test the significant associations between seed coat permeability as well as electrolyte leaching and marker loci, single factor analysis of variance was employed first as described by Edwards et al, (1987) on each pair wise combination of the traits and marker locus using the computer package SYSTAT 6.0 (SPSS Inc. USA). Associations of marker loci with QTLs were considered significant when level of significance was ≤ 0.05.…”

Molecular Plant Breeding as the Foundation for 21st Century Crop Improvement

“…Molecular marker systems for crop plants were developed soon thereafter to create high-resolution genetic maps and exploit genetic linkage between markers and important crop traits (Edwards et al, 1987;Paterson et al, 1988). By 1996, the commercialization of transgenic crops demonstrated the successful integration of biotechnology into plant breeding and crop improvement programs (Koziel et al, 1993;Delannay et al, 1995).…”