Mating dynamics of Scots pine in isolation tents

Abstract

Seed orchards are forest tree production populations for supplying the forest industry with consistent and abundant seed crops of superior genetic quality. However, genetic quality can be severely affected by non-random mating among parents and the occurrence of background pollination. This study analyzed mating structure and background pollination in six large isolation tents established in a clonal Scots pine seed orchard in northern Sweden. The isolation tents were intended to form a physical barrier against background pollen and induce earlier flowering relative to the surrounding trees. We scored flowering phenology inside and outside the tents and tracked airborne pollen density inside and outside the seed orchard in three consecutive pollination seasons. We genotyped 5683 offspring collected from the tents and open controls using nine microsatellite loci, and assigned paternity using simple exclusion method. We found that tent trees shed pollen and exhibited maximum female receptivity approximately 1 week earlier than trees in open control. The majority of matings in tents (78.3 %) occurred at distances within two trees apart (about 5 m). Selffertilization was relatively high (average 21.8 %) in tents without supplemental pollination (SP), but it was substantially reduced in tents with SP (average 7.7 %). Pollen contamination was low in open controls (4.8-7.1 %), and all tents remained entirely free of foreign pollen. Our study demonstrates that tent isolation is effective in blocking pollen immigration and in manipulating flowering phenology. When complimented with supplemental pollination, it could become a useful seed orchard management practice to optimize the gain and diversity of seed orchard crops.

Analysis of Nitrogen Utilization Capability during the Proliferation and Maturation Phases of Norway Spruce (Picea abies (L.) H.Karst.) Somatic Embryogenesis

“…After four weeks of germination, morphological differences related to the nitrogen sources in the maturation medium were evident ( Figure 5). Somatic embryos matured on Gln + NO 3 medium developed slightly better than those matured on NH 4 + NO 3 . Those matured on Gln showed impaired development with only rudimentary root development and often dead shoots.…”

“…PEMs PEM cultures grown either on standard medium or experimental NH 4 + NO 3 , Gln + NO 3 and Gln media exhibited no differences in morphology and development ten days after transfer to experimental media (not shown). However, the proliferation rate of the PEMs differed, resulting in differences in fresh weight increase (Figure 2).…”

“…Proliferation, maturation and synchronization of SE cultures were on media solidified by gelrite (3.5%) in Petri dishes. Cultures were kept in darkness at 20 • C. Mature embryos, selected as normal based on their morphology [16], were dried for 3 weeks under high humidity in darkness and subsequently germinated in 15-cm Petri dishes on solid medium; the germination medium was similar to the medium NH 4 + NO 3 in Table 1 but included KNO 3 (7.56 mM) and sucrose at 87.6 mM, and excluded the ammonium salts, K 2 SO 4 and KCl. The pH was adjusted to 5.8 ± 0.1 prior to autoclaving.…”

“…The germination rate was highest after maturation on Gln + NO 3 medium (90% of total 608 mature embryos), intermediate on NH 4 + NO 3 medium (82.1% of total 1021 mature embryos) and lowest after maturation on Gln medium (74.5% of total 2266 mature embryos). Plantlets with the healthiest shoots and roots developed from embryos matured on Gln + NO 3 medium, followed by those matured on NH 4 + NO 3 . Germinating embryos matured on Gln medium showed the least normal plant development.…”

“…To meet the increased demand for wood products, propagation of superior trees from breeding programs is necessary [1,2]. This has usually required seed orchards, which are expensive and have problems with both pollen contamination and cone diseases [3], or clonal propagation by cuttings, which to date has had only limited success [1]. Somatic embryogenesis (SE) is a promising tool for large-scale clonal propagation that allows the capture of values from the breeding program [2].…”