Temporal trend of variation in Italian rice germplasm over the past two centuries reveled by AFLP and SSR markers

The aim of this study was to characterize the Italian rice (Oryza sativa L.) gene pool, paying particular attention to its variation over time, to determine whether human activity can reduce genetic variability, and whether such a reduction actually occurred in Italian rice varieties. We analyzed 135 Italian rice accessions, representing genotypes either introduced from abroad or developed in Italy from 1880 to 2001, using two groups of molecular markers, amplified fragment length polymorphisms and simple sequence repeats. These accessions were divided into four groups for which different statistical analyses were performed. The levels of gene diversity, from 0.1023 to 0.1921, and genetic richness, from 0.1579 to 0.3064, increased over time. Genetic structure, as estimated by analysis of molecular variance, revealed that the within-component was overwhelmingly dominant (92%) compared with the among-component. These results show that the level of genetic diversity in Italian rice accessions has remained high since 1850 and continues to increase. This is most likely the result of Italian breeding programs that developed new cultivars and introduced others from abroad, without substituting previous accessions. Our results show that the management and improvement of rice germplasm in Italy have been successful in maintaining sufficient genetic diversity.