Germplasm management of faba bean (Vicia faba L.):: Monitoring intercrossing between accessions with inter-plot barriers

Knowledge of gene flow is essential for designing strategies of germplasm multiplication. Inter and intraplot gene flow and pollen dispersion between small plots in a field of Vicia faba germplasm multiplication were measured under four isolation zones at two locations. The four isolation zones were: a barren zone, a nucleocytoplasmic Vicia faba male sterile line, a Vicia faba tetraploid genotype and a Vicia narbonensis L. population. Genotypes fixed for alternative isozyme and allozyme alleles allowed the identification of inter and intra-plot hybrids through progeny testing. A set of log-likelihood ratio (LLR) G tests were used to analyze the effects of geographical location, isolation zone and genotype on the different components of gene flow. Considerable heterogeneity among the genotypes in all the components, inter and intra-plot gene flow and pollen dispersion, of gene flow has been found. It has been shown that gene flow is location, isolation zone and genotype dependent. Planting a barrier surrounding the plots rather than using a non cultivated area between plots seemed more or less efficient for preventing inter-plot gene flow depending on the genotype and the location. Specific associations between genotype and male sterile or tetraploid border rows for every location can bring about gene flow as high, or even higher, than those produced by a barren zone. Differences among the genotypes and borders in flowering overlapping appear not to be the major factor influencing the pattern of gene flow. Implications of the pattern of gene flow observed are discussed in relation to crop diversity managed by farmers.