Temporal Trends of Variation in Italian Rice Germplasm over the Past Two Centuries Revealed by AFLP and SSR Markers

Abstract

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.

Molecular Genetic Diversity of Major Indian Rice Cultivars over Decadal Periods

“…However, from 1970s to 2000s the trend of increase was 4.71% and 8.92% for year of releasewise and longevitywise varieties, respectively. The observed trends in the present study are in agreement with Mantegazza et al, [12], who have reported increase of genetic diversity of Italian rice cultivars between 1850 and 2001. The same trend has been reported also by Morin et al, [35].…”

“…Estimation of genetic diversity in varieties released in different crops during the last century reveals no clear trends [10]. In rice, both decreased [11] as well as increased trend of diversity [12] has been reported.…”

Wholesale replacement of lima bean (Phaseolus lunatus L.) landraces over the last 30 years in northeastern Campeche, Mexico

“…This result indicates that the genetic erosion is not only quantitative as described in the earlier sections, but also qualitative, meaning that over the last 30 years, the genetic make-up of this crop in NECAMP has shifted. This result is also similar to other studies that indicated that plant breeding can generate a qualitative change in the genetic diversity of the crops (Donini et al 2000;Khlestkina et al 2004;XiuQiang et al 2007;Le Clerc et al 2005;Lu and Bernardo 2001;Mantegazza et al 2008). Indeed, our result supports the hypothesis proposed by Martínez-Castillo et al (2004) that the sac ib and mulicion landraces could be improved varieties or landraces introduced to the Yucatan peninsula (probably between 1970 and 1980), that has displaced the local varieties of lima bean.…”

“…Similar results were reported for many other crops (Khlestkina et al 2004;Xiu-Qiang et al 2007;Le Clerc et al 2005;Mantegazza et al 2008). This genetic shift may be a consequence of the introduction of improved varieties or landraces of P. lunatus (Hernández and Delgado 1992).…”

“…Indeed, the loss of landraces is believed to generate erosion at the allelic level (Upadhyay and Sthapit 1998). Several studies to test this hypothesis using molecular data have been carried out in important world crops such as wheat (Donini et al 2000;Khlestkina et al 2004;Xiu-Qiang et al 2007), maize (Le Clerc et al 2005;Lu and Bernardo 2001), and rice (Mantegazza et al 2008). In short, these studies have shown that plant breeding and displacement of landraces have resulted in a qualitative, rather than quantitative, change in genetic diversity over time.…”