Plant Genome III Conference Plant Genome III Conference
The absence of near isogenic lines and the high ploidy levels in sugarcane pose difficulties for the identification of molecular markers. In the present study the potential use of bWk segregant analysis [Michelmore et al, Proc. Natl. Acad. Sci. USA, BI: 9828-9832 (1991)] to establish molecular markers associated with complex traits was investigated. This was done in a population of 150 Fl individuals from a commercial cross AA157 segregating for fibre. Four bulks comprising DNA from five and ten individuals, taken from the extremes for low and high fibre content, were constructed. A total of 749 loci were amplified with 60 random decamer primers. There were 79 polymorphic fragments between the parents, of which 22 were single dose fragments. Eight polymorphic fragments were scored between the high and low fibre groups based on two criteria. Firstly, fragments were scored solely on the basis of presence or absence in the bulks. Secondly, fragments were scored on the basis of their presence in individuals used to construct the bulks, the criterion being that a fragment should be present in four or more individuals on one extreme of the trait, while one aberrant individual could be tolerated in the individuals of the opposite extreme. Six of the polymorphic fragments were traced to the mate parent, 79F201l, and the remaining two to the female parent, N14. Six of the polymorphic DNA fragments segregated in a 1:1 ratio. Two of these markers are significantly linked (p<0.05). In a simulated marker based selection with one of the linked markers a highly significant enrichment for clones with high fibre and carriage of less than 28% clones with low fibre was achieved. Use of both markers in tandem led to carriage of less than 1O% low fibre individuals and a significant further enrichment for high fibre clones in the selected progeny.