title: Genetic Structure and Selection of a Core Collection for Long Term Conservation of Avocado in Mexico.
abstract: Mexico, as the center of origin of avocado (Persea americamaMill.), harbors a wide genetic diversity of this species, whose identification may provide the grounds to not only understand its unique population structure and domestication history, but also inform the efforts aimed at its conservation. Although molecular characterization of cultivated avocado germplasm has been studied by several research groups, this had not been the case in Mexico. In order to elucidate the genetic structure of avocado in Mexico and the sustainable use of its genetic resources, 318 avocado accessions conserved in the germplasm collection in the National Avocado Genebank were analyzed using 28 markers [9 expressed sequence tag-Simple Sequence Repeats (SSRs) and 19 genomic SSRs]. Deviation from Hardy Weinberg Equilibrium and high inter-locus linkage disequilibrium were observed especially indrymifolia, andguatemalensis. Total averages of the observed and expected heterozygosity were 0.59 and 0.75, respectively. Although clear genetic differentiation was not observed among 3 botanical races:americana, drymifolia, andguatemalensis, the analyzed Mexican population can be classified into two groups that correspond to two different ecological regions. We developed a core-collection by K-means clustering method. The selected 36 individuals as core-collection successfully represented more than 80% of total alleles and showed heterozygosity values equal to or higher than those of the original collection, despite its constituting slightly more than 10% of the latter. Accessions selected as members of the core collection have now become candidates to be introduced in cryopreservation implying a minimum loss of genetic diversity and a back-up for existing field collections of such important genetic resources.
authors.affiliation: Centro Nacional de Recursos Genéticos, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias Tepatitlán de Morelos, Mexico.
authors.forename: Luis F
authors.initials: LF
authors.lastname: Guzmán
authors.affiliation: Gene Research Center, University of Tsukuba Tsukuba, Japan.
authors.forename: Ryoko
authors.initials: R
authors.lastname: Machida-Hirano
authors.affiliation: Gene Research Center, University of Tsukuba Tsukuba, Japan.
authors.forename: Ernesto
authors.initials: E
authors.lastname: Borrayo
authors.affiliation: Centro Nacional de Recursos Genéticos, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias Tepatitlán de Morelos, Mexico.
authors.forename: Moisés
authors.initials: M
authors.lastname: Cortés-Cruz
authors.affiliation: Fundación Salvador Sánchez Colín, CICTAMEX S. C., Ignacio Zaragoza, Col. Centro Coatepec Harinas, Mexico.
authors.forename: María Del Carmen
authors.initials: MD
authors.lastname: Espíndola-Barquera
authors.affiliation: Campo Experimental Bajío, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias Celaya, Mexico.
authors.forename: Elena
authors.initials: E
authors.lastname: Heredia García
keywords: PCA-Kmeans; Persea americana; botanical races; core collection; microsatellites