MOLECULAR MARKERS IN PLANT IMPROVEMENT - MANIPULATION OF GENES AFFECTING QUANTITATIVE TRAITS

The use of molecular markers to enhance plant breeding efforts is bein g widely studied. A major area of research is the use of molecular mar kers to identify and manipulate chromosome segments QTL (quantitative trait locus or loci depending on context) controlling quantitative tra its. The objective of this paper is to review the theory and results a ssociated with the use of molecular markers to manipulate QTL in plant breeding programs. First, methods of identifying marker-QTL associati ons are considered. The various statistical methods used for this purp ose are reviewed along with a discussion of appropriate probability le vels to use in declaring associations real. The effects of genotype x environment interaction and repeatability between populations are then considered. Following the section on identification of associations, the use of marker-QTL associations in breeding procedures is reviewed. A review of procedures useful for small numbers of QTL is followed by a review of procedures appropriate when large numbers of QTL are foun d. The use of marker-QTL associations for multiple trait selection is considered. Throughout the review, appropriate theory is considered an d results which have been obtained are presented.