Genetic analysis of morphological variation in Brassica oleracea using molecular markers

Abstract

A cross between the open-pollinated Brassica oleracea cabbage cultivar 'Wisconsin Golden Acre' and the hybrid broccoli cultivar 'Packman' was used with molecular markers to investigate the genetic control of morphological variation. Twenty-two traits derived from leaf, stem, and flowering measurements were analyzed in 90 F2 individuals that were also classified for genotype by restriction fragment length polymorphism (RFLP) markers. Seventy-two RFLP loci, which covered the mapped genome at an average of 10 map-unit intervals on all nine linkage groups, were tested individually for associations to phenotypic measurements by single factor ANOVA, and markers with significant associations (P<0.05) were used to develop multilocus models. These data were utilized to describe the location, parental contribution of alleles, magnitude of effect, and the gene action of trait loci. Single marker loci that were significantly associated (P<0.05) with trait measurements accounted for 6.7-42.7% of the phenotypic variation. Multilocus models described as much as 60.1% of the phenotypic variation for a given trait. In some cases, different related traits had common marker-locus associations with similar gene action and genotypic class ranking. The numbers, action, and linkages, of genes controlling traits estimated with marker loci in this population corresponded to estimates based on classical genetic methods from other studies using similar, or similarly-wide, crosses. There was no evidence that genome duplication accounted for a significant portion of multiple genes controlling trait loci over the entire genome, but possible duplications of trait loci were identified for two regions with linked, duplicated marker loci.

Morphological characterisation of white head cabbage (Brassica oleraceavar.capitatasubvar.alba) genotypes in Turkey

“…Many reports conclude that relationships among genotypes obtained from morphological and agronomic characters are different from those obtained from isozyme and allozyme, RFlpS and RApD markers. there are similar reports for cabbage (Dias et al 1993;Kennard et al 1994;Santos et al 1994;Koutsos& Koutsika 2001). It would be possible to reach more conclusive results by using these techniques, even if cabbage genotypes were very similar to each other in their morphological traits.…”

Genetic dissection of seed shattering, agronomic, and color traits in American wildrice (Zizania palustris var. interior L.) with a comparative map

“…Multilocus models were constructed with a multiple regression "backwards elimination" procedure using PROC GLM (Kennard et al 1994; SAS Institute, Cary, North Carolina). PLABQTL (Utz and Melchinger 1997) composite interval mapping in a stepwise regression was used to confirm results with the "backwards elimination" procedure.…”

USDA Plant Genome Research Program

“…However, much of the variation for morphology in Brassica is under polygenic control. Some of these quantitative trait loci (QTL) were identified by analyzing populations from crosses of very different morphological forms in B. oleracea (Kennard et al, 1994) and B. rapa (Song et al, 1994). Although analyzed as QTL, alleles at many of the loci identified in these studies had very large effects, suggesting that major genes have played an important role in the evolution of morphological variations in Brassica.…”

“…However, loci with small effects also were identified, and it is alleles at these types of loci that breeders have probably manipulated to fine tune the current forms of our cultivars. The vernalization requirement is an important component of morphological variation, and loci controlling this have been mapped in several studies (Camargo, 1994;Ferreira et at., 1994b;Kennard et al, 1994;Kianian and Quiros, 1992).…”