GENETIC DIVERSITY AT TWO SEED ORCHARDS OF Pinus patula SCHIEDE ex SCHLTDL. et CHAM.

Genetic diversity is important in seed orchards to produce plants with high capability of adaptation to environmental changes; thus, the objective of this study was to evaluate the genetic diversity and structure of two asexual seed orchards of Pinus patula and to determine the degree of differentiation of each orchard. The first orchard is located at common land La Selva, municipality of Huayacocotla, Veracruz, Mexico and the second one at common land Villa Cuauhtemoc, municipality of Chignahuapan, Puebla. Mexico. Each orchard was established with phenotypically superior cloned trees selected in their own area. Foliage samples were collected from one ramet from each clone in both orchards. Microsatellite molecular markers NZPR114, NZPR5, PtTX2123, PtTX2146, PtTX3107 and PtTX3127 were used to perform the genetic diversity analysis. The average number of alleles per locus was 9.9 for both seed orchards. The observed and expected heterozygosities were 0.602 and 0.693, respectively. The fixation index was 0.125. A deficit of heterozygotes was found when both seed orchards were analyzed jointly (F-IT = 125) and within each of the orchards (F-IS = 105). The differentiation index was low (F-ST = 0.023). Most of the genetic diversity was found within the orchards with only 4.5 % between them. The genetic diversity was high in the asexual orchards of P. patula with moderate deficiency of heterozygotes and low level of differentiation between both seed orchards.