Germination and initial growth of half-sibling families of Pinus pseudostrobus Lind. outstanding in resin production

The establishment of commercial forest plantations necessitates the use of high-quality genetic seed and the selection of superior individuals. This study aimed to evaluate the germination ability including germination percentage, germination velocity index, and germination rate as well as the initial growth characteristics (height and root collar diameter) of seedlings from 23 half-sibling families of Pinus pseudostrobus Lindl., selected for their exceptional resin production, across three altitudinal gradients. Half-sibling seeds of P. pseudostrobus were sown in 310 cm3 plastic-coated containers filled with a 1:1:1:1 substrate mixture of pine bark, Canadian sphagnum peat moss, vermiculite, and perlite, supplemented with Multicote® fertiliser at a concentration of 5 kg/m3. Each family was represented by four replicates, or experimental units, consisting of 25 completely randomised seeds. The evaluated variables were as follows: 1) germination percentage (PG), 2) germination vigour (VG) through the index of germination velocity (IVG), 3) germination rate (TG), 4) plant height (A), and 5) diameter of the root collar (DCR). Significant differences (p < 0.05) were found in the germination percentage and index of germination velocity between altitudinal gradients and between families in all measured variables. Our results suggest that germplasm collection should be performed within a gradient between 2,200 and 2,400 m, where seeds present the most intraspecific variation and the highest germination percentage, height, and root collar diameter.