GENETIC VARIATION AMONG Pinus patula POPULATIONS ALONG AN ALTITUDINAL GRADIENT. TWO ENVIRONMENT NURSERY TESTS

Abstract

Aiming to determine if there is genetic differentiation among Pinus patula Schiede et Chamizo populations along an altitudinal gradient and for quantifying the genotype x environment interaction, 13 Pinus patula populations were sampled from forests of the Native Indian Community of Ixtlán de Juárez, Oaxaca, state of México, along an altitudinal gradient (2400 m to 3000 m), cones being collected on groups of trees on every 50 m of altitudinal step). Seedlings were grown in tree pots in two different environments: a shadehouse located at Ixtlán de Juárez, and in a greenhouse and then in a shadehouse situated at Quebec, Canada. Total seedling height was measured at 6-months of age in both locations. Results indicated that populations differed significantly (P = 0.025), but there was no significant genotype x environment interaction (P = 0.426; B type genetic correlation = 0.93). Population from 2650 m (middle altitude) exhibited the best height. Although not definitive, our study suggests the presence of a weak altitudinal pattern of variation in seedling height, where populations originating of mid-altitudes exhibit the highest growth potential while populations from the upper and lower altitudinal extremes exhibit the lowest growth potential.