Conservation and utilization strategies require fundamental knowledge about levels of genetic diversity, population genetic structure and effective population size, because they are the key elements that determine a species ability to respond to selection, either natural and artificial procedures. Sweet chestnut (Castanea sativa Mill.), widely distributed around Europe, is a multipurpose tree species of great economic importance for fruit and timber. Moreover, chestnut contributes to carbon storage, the landscape structure and the biodiversity conservation, that are relevant factors for environment management especially under climate change. Although there is information about chestnut traditional varieties, up to now, there is not complete information on the genetic diversity of natural populations in Spain. In this study, patterns of genetic variation and structure are assessed within and among natural populations of chestnut in Spain. 17 natural populations were evaluated using 7 microsatellite markers and Alleles in Space (AIS) software. This study allowed to describe the level and distribution of the genetic variability in Spanish chestnut populations, showing a high genetic diversity. Moreover, populations displayed a structure that followed a geographical pattern, indicating in a first approach, a separation between populations from West and east of the Iberian Peninsula.
There is a shortage of information about the ryegrass crop (Lolium multiflorum Lam.), especially regarding the suitable sowing rate. Thus, the present work aimed to determine the most adequate sowing rate for tetraploid ryegrass cultivars. A tetraploid ryegrass population was sown at different densities: 150, 300, 600, 900, 1200, 1500, 1800 seeds/m². The number of plants per m², percentage of soil cover, leaf yield and green and dry forage yield were evaluated. The experimental design was randomized blocks with three replications. To observe the behavior of the pasture at different densities for each cut, regression analysis was performed, through which it was possible to verify that the sowing rate has greater influence on the initial cut of the crop. In all the variables analyzed by regression, only the second cut presented a linear trend favorable to the increase in density. In the other cuts, an increase was observed, both in the height of plants and in the yield variables, up to the density of 1500 seeds/m², with a subsequent fall to the highest density, indicating that higher densities may be detrimental to pasture yield. Therefore the density of 1500 seeds/m² is the most suitable for tetraploid ryegrass cultivars.
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