ABSTRACT
The quality of plant oil is determined by its component fatty acids. Relatively high levels of linolenic acid reduce the oxidative stability of the oil, and high levels of erucic acid in the diet have been associated with health problems. Thus, oilseed Brassica napus cultivars with low linolenic and low erucic acid contents are highly desirable for edible oil production. In order to identify genes controlling the levels of erucic and linolenic acids, we analyzed the oil composition of 99 F1-derived doubled haploid lines from a cross between cv 'Major' (high levels of erucic and linolenic acids) and cv 'Stellar' (low levels of both fatty acids). A molecular marker linkage map of 199 loci for this population was used to identify quantitative trait loci (QTL) controlling oil composition. We identified two regions that accounted for nearly all of the phenotypic variation in erucic acid concentration and one region that accounted for 47% of the variation in linolenic acid concentration. The QTL associated with linolenic acid concentration mapped near a RFLP locus detected by a cDNA clone encoding an omega-3 desaturase, suggesting that the low linolenic acid content of 'Stellar' may be due to a mutation in this gene.
ABSTRACT
The F2 generations from two maize crosses were used to compare the ability of RAPD and RFLP marker systems to create a genetic linkage map. Both RFLPs and RAPDs were shown to provide Mendelian-type markers. Most of the RFLPs (80%) could be placed with a good level of certainty (LOD>4) on the genetic linkage map. However, because of their dominant nature, only between 37% and 59% of the RAPDs could be placed with such a LOD score. The use of combined data from RFLPs and RAPDs increases the level of information provided by RAPDs and allows the creation of a combined RFLP/RAPD genetic linkage map. Thus, the RAPD technique was found to be a powerful method to provide improved probes coverage on a previously created RFLP map and to locate markers linked to chromosomal regions of interest.
