Abstract

Timber from walnut is highly prized by its aesthetical, mechanical and physical properties. Although several varieties for fruit production have been obtained, few genotypes and progenies exist for wood production. The French hybrid progeny Mj209xRa has showed great adaptability to European conditions, and its superiority regarding other hybrids and pure species, becoming the most valuable and widely used progeny for timber production. Although the great phenotypic variability that affects seed plantations reduces their industrial exploitation, it is a suitable opportunity for the selection of outstanding genotypes. Since this progeny is formed by half-siblings, the use of solid markers, as microsatellites, might help to characterize the genetic variability and to differentiate close related individuals. Recently have been published microsatellite markers for this progeny; however, because of the great degree of kinship of Mj209xRa offspring, might be necessary more markers to differentiate individuals with a high certainty degree. Therefore, the suitability of microsatellite markers from American black walnut (Juglans nigra L.) for genetic differentiation of trees from the walnut hybrid progeny Mj209xRa was assessed. Genomic DNA from 50 trees from the hybrid progeny Mj209xRa were used. For PCR amplifications, 10 microsatellite markers were selected, and statistical analysis were performed to determine their individual and combined differentiation capacity. PCR products from all 10 loci were obtained, although for 2 of them the amplifications were non-scorable. In general, reduced polymorphisms (3 alleles/locus) as well as lower heterozygosities and combined discriminative power (PID_sib in the order of 10^-2) were registered. Hence, this set of SSR markers was not suitable to differentiate putative hybrid trees from the Mj209xRa progeny. However, 3 loci can be used as a complement for other microsatellite sets, increasing thus the discriminative capacity of the existing markers.

Keywords: Timber Production; Genotyping; Genotype Identification; Simple Sequence Repeats; SSR

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