IDENTIFICATION OF GENETIC-FACTORS FOR ALACHLOR TOLERANCE IN MAIZE BY MOLECULAR MARKERS ANALYSIS

Genetic factors controlling tolerance to the herbicide Alachlor in mai ze were localised by means of two different strategies. In the first a pproach, backcross (BC) plants, derived from pollen which had been sub jected to selective pressure for resistance to the herbicide, were ana lysed for segregation distortion at 47 RFLP loci and compared to BC pl ants obtained from non-selected pollen. Preferential transmission of f ive chromosomal regions where putative QTLs (Quantitative Trait Loci) are localised was revealed in the BC plants from selected pollen. A se cond approach was based on a classical linkage analysis for segregatio n of the same set of RFLPs and factors controlling the trait, in a BC population of 210 individuals, by means of regression analysis. This s tudy detected seven significant loci in four genomic regions. Overall, two loci revealed both segregation distortion and association with th e expression of the trait: indicating linkage to genes expressed in bo th gametophytic and sporophytic phase. Three chromosomal regions appea red to carry factors involved in plant tolerance to Alachlor which are not expressed in pollen. Conversely, three loci were linked to factor s selectable in pollen, but did not reveal significant association wit h tolerance in the plant in the segregating populations.