Clonal variation in reproductive phenology in a seed orchard of Pinus patula

Abstract

Pinus patula is an important native species from Mexico. A clonal seed orchard with 83 clones was established in a location at 2,800 m asl. Floral synchrony was evaluated on a sample of 157 ramets of 20 clones that were eight and nine years old. Reproductive phenology was recorded every five days for 10 weeks until the pollen was completely released, and scales of female strobili were closed. The beginning and ending dates of receptivity and pollen release was scored. Reproductive synchronization for all possible pairs of clones was quantified. Phenological synchronization index indicated an acceptable degree of crossover. The receptivity of the female strobili and delivering pollen from male strobili showed good synchronization, according to the synchronization index values that varied from 0.33 to 0.54 for female flowering, and it ranged from 0.22 to 0.55 for the male flowering of different clones. The index of phenological synchronization (pollen-ovule) of the group of clones with superior genetic quality was slightly larger than that of low genetic quality clones (0.48 vs 0.40). The contribution of pollen from lower genetic clones to higher clones was moderate (PO = 0.46). The behavior of the clones was stable over the two years of evaluation on synchronization, onset and duration of reproductive events, particularly in the male flowering. Female strobili production was very sensitive to the low temperatures occurred in 2013.