Genetic diversity evolution through participatory maize breeding in Portugal

Abstract

Natural, and in particular, artificial (human) selection may pose a danger to the existing crop genetic diversity. Nevertheless, on-farm breeding systems seem to achieve phenotypic improvements even though preserving variability. Using SSR markers, we analysed several selection cycles, over a 20 years period, of a Portuguese on-farm participatory maize OPV-'Pigarro' breeding project. No significant differences in allelic richness (N ar ), observed heterozygosity (H O ), expected heterozygosity (or gene diversity; H E ) or inbreeding coefficient (f) were detected among the selection cycles. 58 out of 107 alleles were common to all the selection cycles studied. The analysis of molecular variance showed that the variation among selection cycles represented only 7% of the total molecular variation. However, the number of private alleles varied among the selection cycles, being the highest detected at the beginning of the selection project. These findings demonstrate that an allele flow took place during the on-farm selection process of 'Pigarro' but the level of genetic diversity was not significantly influenced. Since interesting phenotypic improvements were also achieved, on-farm breeding projects, like this one, should be valued as a way to preserve unique Portuguese maize landraces in risk of disappearing.

Participatory Plant Quality Breeding: An Ancient Art Revisited by Knowledge Sharing. The Portuguese Experience

“…On the contrary, ear length decreased significantly [38]. Molecular SSR mark-er data, from [42], on three selection cycles (C0-1984, C9-1993 and C20-2004), revealed that no effective loss of genetic diversity has occurred during the selective adaptation to the farmer's needs and the regional growing conditions. Variation among selection cycles represented only 7% of the total molecular variation, indicating that a great proportion of the genetic diversity is maintained in each selection cycle.…”

“…Genetic diversity has not been reduced from the "Pigarro" bred before 1984 to those examples improved after 2004, but the genetic diversity maintained is not exactly the same. Mass selection seems to be an effective way to conserve diversity on-farm, and interesting phenotypic improvements were achieved as the bigger ears farmers' objective [42].…”

“…First we are using molecular markers to evaluate the progress obtained in conserving or increasing diversity through participatory breeding, as already described in the section 2.3 of PPB success evaluation [42]. The genetic diversity of the newly introduced maize and beans landraces into the participatory plant breeding net is now also routinely characterized, with 20 to 22 SSR uniformly distributed throughout the maize and bean genomes respectively.…”

Phenotypic Changes in Different Spinach Varieties Grown and Selected under Organic Conditions

“…In the literature, results can be found on the evolution of farmer varieties based on genetic markers, for instance [11][12][13], but there are few results based on phenotypic traits that are of direct relevance to the farmers [12,14]. Thus, in the EU, research programme Farm Seed Opportunities [15], experiments over three years studied on-farm cultivation and selection in contrasting environments of farmer varieties of wheat, maize, bean and spinach.…”

Sample size for diversity studies in tetraploid alfalfa (Medicago sativa) based on codominantly coded SSR markers

“…The number of alleles is often compared within and among studies to investigate which populations or groups of populations shows a higher diversity (Flajoulot et al 2005;Sardaro et al 2008;Patto et al 2008). The coefficient of variation of number of alleles was decisively reduced when comparing subsamples with 40 genotypes to 10 genotypes but a moderate decrease was still observed between 40 and 20 genotypes (Table 1).…”