Dissecting the regulation of fructan metabolism in perennial ryegrass (Lolium perenne) with quantitative trait locus mapping

Abstract

Summary• Quantitative trait locus (QTL) mapping, which can be a useful tool for dissecting complex traits, has been used here to study the regulation of fructan metabolism in temperate forage grasses.• An F2 mapping family, derived from a high water-soluble carbohydrate (WSC) × low WSC cross, was used to map fructans and the other components of WSC (sucrose, glucose and fructose) in leaves and tiller bases of perennial ryegrass ( Lolium perenne ) in spring and autumn. To characterize regions of the genome that control basic carbohydrate metabolism, a strategy to minimize the impact of genotype (G) × environment (E), and E-effects on the characterization of G-effects, was adopted.• Most traits were highly variable within the family. There was also considerable year-to-year environmental variation. However, significant genetic effects were detected, and several traits had high broad-sense heritability. QTL were identified on chromosomes 1, 2, 5 and 6. Leaf and tiller base QTL did not coincide. Individual QTL explained between 8 and 59% of the total phenotypic variation in the traits.• Fructan turnover, metabolism and their genetic control, and the effect of environment, are discussed in the context of the results. Abbreviations AFLP, amplified fragment length polymorphism; DP, degree of polymerisation; G × E, genotype by environment; HPLC, high-performance liquid chromatography; LOD, log-odds score; QTL, quantitative trait locus (loci); RFLP, restriction fragment length polymorphism; SSR, simple sequence repeat; STS, sequence-tagged site; WSC, watersoluble carbohydrate.

Testing water-soluble carbohydrate QTL effects in perennial ryegrass (Lolium perenne L.) by marker selection

“…All these regions were later conWrmed by subsequent analysis of a full data set for three replicate years, although fructan and/or total WSC QTLs were not always detected ). Only one further major QTL region (on chromosome 6) was subsequently detected by Turner et al (2006). The QTL eVects reported in the 2006 publication are summarised in Table 1.…”

“…The plants were renewed each year from a small group of tillers. Tiller base and leaf material were sampled from February 2002 to October 2004 for analysis of the individual components of WSC as in Turner et al (2006). All material was immediately frozen in liquid nitrogen, stored at ¡80°C, freeze-dried and then Wnely chopped prior to extraction for WSC.…”

“…Carbohydrates from plants in the glasshouse were extracted and analysed following the procedures of Turner et al (2006). Individual sugars were separated and quantiWed by isocratic high performance liquid chromatography (HPLC).…”

“…The WSC data for leaves and tiller bases (mg g ¡1 dry matter) are means with standard errors and were calculated from the 3-year entry means of the data collected in the study of Turner et al (2006). The frequency of the high QTL-allele was based on one QTL-speciWc PCR-based marker per QTL content of neutral detergent Wbre (NDF), and WSC content all expressed as percentage of dry matter.…”

“…The primary objective of the work reported here was to carry out a test-crossing programme to examine the eVects of the individual perennial ryegrass WSC QTLs published by Humphreys et al (2003) and subsequently conWrmed in Turner et al (2006). Accordingly, markers were used to design individual narrow-based populations with contrasting homozygosity for each of four target QTL regions.…”