Elevated temperature during reproductive development affects cone traits and progeny performance in Picea glauca x engelmannii complex

Abstract

Two temperature regimes were applied during reproductive development of seed and pollen cones of interior spruce (Picea glauca (Moench) Voss and Picea engelmannii (Parry) complex) to determine temperature effects on the adaptive traits of progeny. In Experiment 1, identical crosses were made on potted interior spruce using untreated pollen followed by exposure to a day/night temperature of 22/8 or 14/8 degrees C with a 12-h photoperiod during the stages of reproductive development from post-pollination to early embryo development. Frost hardiness and growth of progeny from seed produced in the two temperature treatments were measured over a 4-year period. Elevated temperature significantly affected both seed-cone development and the adaptive properties of the progeny. Seed cones exposed to the 22/8 degrees C treatment reached the early embryo stage in 53 days versus 92 days in the 14/8 degrees C treatment. Seed yields, cotyledon emergence and percent germination were also significantly enhanced by the 22/8 degrees C treatment. Progeny from seed produced in the higher temperature treatment showed significantly reduced spring and fall frost hardiness, but the elevated temperature treatment had no significant effects on time of bud burst, growth patterns or final heights. In Experiment 2, single ramets of the same clone were subjected to a day/night temperature of 20/8 or 10/8 degrees C during pollen cone development, starting from meiosis and ending at pollen shedding. The two populations of pollen were then crossed with untreated seed cones. Compared with pollen cones exposed to the 10/8 degrees C treatment, pollen cones exposed to the 20/8 degrees C treatment during development reached the shedding stage 2-4 weeks earlier, whereas pollen yields, in vitro viability and fertility (seed set) were significantly lower; however, the resulting progeny displayed no treatment differences in frost hardiness or growth after 1 year. Results suggest that seed orchard after-effects could be caused by temperature differences between orchard site and parent tree origin and that this effect acts on maternal development. Gametophytic (pollen or megagametophyte or both) and early embryo (sporophytic) selection are possible mechanisms that may explain the observed results. Although the effects are biologically significant, they are relatively small and do not justify changes in current deployment strategies for seed orchard seed.

Epigenetic memory effects in forest trees: a victory of “Michurinian biology”?

“…It appeared that the seeds produced in southern seed orchards 'remember' in some way the climate at the site of production, despite containing genes inherited from parents originating from the North (hence the designation 'memory' or 'carryover' effects). Similar observations were made on North-American conifers (Greenwood and Hutchison 1996;Stoehr et al 1998;Webber et al 2005).…”

Rapid change in adaptive performance from one generation to the next in Picea abies—Central European trees in a Nordic environment

“…In particular, seed production in a cold environment advances bud set and cold acclimation in the autumn (Johnsen et al 2005a, b;Webber et al 2005). Compared to outdoor conditions, seed production of the same full-sib families under higher temperatures in a greenhouse delayed the bud set for several days.…”

Does maternal environmental condition during reproductive development induce genotypic selection in Picea abies?

“…Several other studies clearly indicated an influence of the crossing environment on the performances of different spruce progenies (e.g. [20][21][22]55]). This rapid change in behaviour may be explained by different factors and, in particular, the occurrence of selective effects during the reproductive process could be one of them.…”