USE OF ISOZYMES AND RFLP MARKERS TO ASSESS GENETIC DIVERSITY IN INTROGRESSION PROCEDURES BETWEEN ADAPTED AND NON-ADAPTED MAIZE POPULATIONS (ZEA-MAYS L)

Genetic diversity and its organization were investigated in a diallel cross involving six six-line maize synthetic populations, consisting o f three Corn Belt dents and three exotics (a Cateto flint, and an adap ted version each of Mexican dent and Caribbean flint/dent). Sixteen is ozyme loci were analysed on the 6 parental synthetic populations and t he 15 Fl crosses. RFLP analysis was also conducted using eighteen geno mic DNA probes on material from Cornbelt 1, Cateto synthetics and thei r F1 cross progenies. Genetic diversity revealed by isozymes and RFLPs was high for Corn Belt synthetics, whereas the lines involved in the exotic synthetics did not reflect the high level of polymorphism descr ibed by other authors. Some Cateto inbreds (from which the Cateto synt hetic population was derived) presented a residual polymorphism for on e to four isozyme loci. Cateto and Cornbelt2 synthetics showed the low est genetic variability. Confrontation between ''adapted'' and ''non a dapted'' genomes revealed segregation distortion for six isozyme loci, mainly for crosses between exotic and Corn belt on one hand and betwe en exotic populations on the other hand. From RFLP analysis of F1 cros s (Cornbelt 1 x Cateto) no segregation distortion was evidenced. This study supports discussion on prebreeding strategies needed for genetic resources enhancement.