Development of Highly Validated SNP Markers for Genetics Analyses of Chestnut Species.

To better study and manage chestnut trees and species, we identified nuclear single nucleotide polymorphism (SNP) markers using restriction-associated DNA sequencing. Out of 343 loci tested, 68 SNP markers were selected that withhold stringent quality criteria such as quasi-systematic amplification across species and Mendelian segregation in both purebred and hybrid individuals. They provide sufficient power for species, hybrids and backcross characterization as well as for clonal identification, as shown by a comparison with single sequenced repeat (SSR) loci.

The traceability of Eucalyptus clones using molecular markers

The improvement of Eucalyptus clones plays a crucial role in modern silviculture. This study used a set of 17 microsatellite loci to analyze the genetic diversity and structure of 107 elite clones (80 E. grandis and 27 E. globulus). All clones were cultivated in Uruguay and were sourced from three different providers. Using the fingerprinting technique, an exclusive molecular profile was assigned for each clone, and the genotyping reaction showed differences between the two species. The cumulative probability of identifying two random individuals that share the same genotype (PI) with all 17 loci, was estimated as low for E. grandis (1.18×10-15) and E. globulus (4.03×10-14). The combined PIsibs was (1.05×10-5) and (2.17×10-5) for E. grandis and E. globulus, respectively. A total of 180 alleles were detected for E. grandis and 100 for E. globulus. We found a high mean number of alleles per locus (10 for E. grandis and 6 for E. globulus), and the results for mean polymorphic information content (PIC ) were (0.648) and (0.548), respectively. The observed heterozygosity (Ho ) ranged from 0.216 to 0.838 (mean = 0.509) for E. grandis and 0 to 1 (mean = 0.566) for E. globulus. Two core sets of seven EST-SSR loci were identified for each species. These markers revealed unambiguous fragment amplification, providing a minimum number of SSRs for effective clonal identification. The genetic structure analysis suggests that the germplasm of the E. grandis population is structured in four clusters, while the E. globulus population consists of two clusters.

Clonal Identification Based on Quantitative, Codominant, and Dominant Marker Data: A Comparative Analysis of Selected Willow (SalixL.) Clones

Clonal identification in forestry may employ different means, each with unique advantages. A comparative evaluation of different approaches is reported. Nine quantitative leaf morphometric parameters, 15 variable codominant (isoenzyme) and 15 variable dominant (RAPD) loci, were used. All clones presented unique multilocus isoenzyme genotypes and 86% presented unique multilocus RAPD genotypes. Quantitative, isoenzyme and molecular data were subjected to principal component analysis, the latter two data sets after vector transformation. Most of the variability (quantitative 99%, isoenzyme 72.5%, RAPD 89%) was accounted for in the first three axes. This study has shown: (1) individual quantitative parameters were inefficient for clonal identification, (2) multilocus clonal identification was successful, (3) dominant markers were more polymorphic than codominant ones: 1.5 variable loci per enzyme system, 7.5 variable RAPD loci per primer, (4) 15 codominant marker loci could identify about 2.8 times more individuals than 15 dominant ones, but this advantage is surpassed when 42 dominant loci are employed, (5) multivariate analysis of morphological, codominant and dominant genetic data could not discriminate at the clonal level. It was concluded that due to their higher number of loci available dominant markers perform better than codominant ones, despite the higher informativeness of the latter.