Mating dynamics of Scots pine in isolation tents

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). Self-fertilization 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.     

Leaf-rust resistance in rye (<Emphasis Type="Italic">Secale cereale</Emphasis> L.). 2. Genetic analysis and mapping of resistance genes <Emphasis Type="Italic">Pr3</Emphasis>, <Emphasis Type="Italic">Pr4</Emphasis>, and <Emphasis Type="Italic">Pr5</Emphasis>

The conventional way to drive modifications in old forest tree seed orchards is to establish progeny trials involving each parent tree and then evaluate its contribution to the performance of the progeny by estimating its general and specific combining ability (GCA and SCA). In this work, we successfully applied an alternative parent selection tactic based on paternity testing of superior offspring derived from a hybrid seed orchard established with a single Eucalyptus grandis seed parents and six E. urophylla pollen parents. A battery of 14 microsatellite markers was used to carry out parentage tests of 256 progeny individuals including two independent samples of selected trees and one control unselected sample, all derived from 6-year-old forest stands in eastern Brazil. Paternity determination was carried out for all progeny individuals by a sequential paternity exclusion procedure. Exclusion was declared only when the obligatory paternal allele in the progeny tree was not present in the alleged parent tree for at least four independent markers to avoid false exclusions due to mutation or null alleles. After maternity checks to identify seed mixtures and selfed individuals, the paternity tests revealed that approximately 29% of the offspring was sired by pollen parents outside the orchard. No selfed progeny were found in the selected samples. Three pollen parents were found to have sired essentially all of the offspring in the samples of selected and non-selected progeny individuals. One of these three parents sired significantly more selected progeny than unselected ones (P0.0002 in a Fisher exact test). Based on these results, low-reproductive-successful parents were culled from the orchard, and management procedures were adopted to minimize external pollen contamination. A significant difference (P<0.01) in mean annual increment was observed between forest stands produced with seed from the orchard before and after selection of parents and revitalization of the orchard. An average realized gain of 24.3% in volume growth was obtained from the selection of parents as measured in forest stands at age 2–4 years. The marker-assisted tree-breeding tactic presented herein efficiently identified top parents in a seed orchard and resulted in an improved seed variety. It should be applicable for rapidly improving the output quality of seed orchards, especially when an emergency demand for improved seed is faced by the breeder.Communicated by D.B. Neale     

Plants,position and pollination: Planting arrangement and pollination limitation in a revegetated eucalypt woodland

The spatial arrangement of plants is a key determinant of pollination services in natural ecosystems. Despite this, plant arrangements are rarely considered an important characteristic of revegetated communities and this may be limiting successful pollination dynamics in these re‐created systems. We assessed if aggregated South Australian Blue Gum (Eucalyptus leucoxylon, F. Muell) had greater pollination success than more dispersed trees by measuring fruit set, seed production and germination in a revegetated eucalypt woodland. The proportion of buds that developed into fruit (fruit set) was similar between aggregated (five flowering Blue Gum within 30 m) and dispersed (no flowering Blue Gum within 30 m) trees (<14%). Aggregated and dispersed trees produced a similar number of seeds per fruit in 2015, when fewer trees flowered and those that flowered produced fewer flowers (ca 8 seeds/fruit). In 2016, when flowering was more abundant, aggregated trees produced more seeds per fruit than dispersed trees (12 seeds/fruit compared to 4 seeds/fruit). Despite differences in seed number, there was no difference in the quality of seed produced, indicating outcrossed pollen was received by both aggregated and dispersed trees. Although outcrossing was likely, this did not prevent pollination limitation, with the addition of outcrossed pollen increasing fruit and seed set for trees in both arrangements. Consequently, we propose that planting individuals of the same species (conspecifics) in clumps, rather than intermixing species, can increase seed set in revegetated eucalypts, particularly in good flowering years. However, aggregated plantings will be most effective if the needs and foraging behaviour of pollinators are also considered, to attract and sustain pollinators in revegetated systems, thereby minimizing the risk of pollination limitation.     

Complex patterns of mating revealed in a Eucalyptus regnans seed orchard using allozyme markers and the neighbourhood model

The neighbourhood model apportions offspring of individual mother plants to self-fertilization, outcrossing to males within a circumscribed area around the mother plant (the neighbourhood), and outcrossing to males outside the neighbourhood. Formerly the model was applied only to haploid pollen gametes in the offspring of conifers, but is extended so that it can be used with genotypic data from diploid offspring of both angiosperms and gymnosperms. In addition, it is shown that the mating parameters can be estimated without independent estimates of allele frequencies in the pollen pools outside the neighbourhood; thus the model might be applied effectively to natural populations exposed to unknown external pollen sources. Parameters of the neighbourhood mating model were estimated for a 10-year-old seed orchard population of the insect-pollinated tree, Eucalyptus regnans, in southeast Australia, which contained a mixture of two geographical provenances (Victoria and Tasmania). The mating patterns revealed were complex. Crosses between trees of the same provenance occurred three times more often than crosses between trees of different provenances. Levels of self-fertilization and patterns of mating within neighbourhoods were influenced by provenance origin, crop fecundity and orchard position (central vs. edge) of mother trees. Gene dispersal, however, was extensive, with approximately 50% of effective pollen gametes coming from males more than 40 m away from mother trees (average distance between neighbouring trees was 7.4 m). Thus, insect pollinators are efficient promoters of cross-fertilization in this orchard, with the result that the effective number of males mating with each female is large.     

Performance of microsatellites for parentage assignment following mass controlled pollination in a clonal seed orchard of loblolly pine (Pinus taeda L.)

Mass controlled pollination (MCP), involving large-scale application of pollen on physically isolated female reproductive organs, has been a lower cost alternative to controlled pollination for the commercial production of genetically improved seeds. Nevertheless, rare are the studies that examined the efficacy of operational MCP and no such assessment has been done in loblolly pine to date. The success of MCP was assessed by a microsatellite-based investigation of the realized versus expected parentage of a set of 300 Pinus taeda offspring in 19 families generated in two subsequent rounds of MCP in 2005 and 2006 in a clonal seed orchard in Brazil. Multi-locus combined probability of parentage exclusion both theoretical and realized from actual testing was >99 % for single parent and parent pair testing when using nine or ten markers. Parentage assignments carried out under a maximum likelihood framework revealed a significantly higher success rate of MCP in 2006 (84 %) following technical improvements adopted to minimize pollen contamination and maximize male reproductive success, although significant variability in the correct maternity and full parentage was seen among individual families. The observed patterns of unexpected parentage indicated that this variability likely resulted from mislabeling of clonal ramets of the parents used in the crosses which impacted both maternity and paternity. Preventing pollen contamination will not be sufficient for successful MCP if inaccuracies exist in the identity of the clonal plants that ultimately provide pollen and female strobili, showing that DNA marker auditing and correction of identity of all ramets in a clonal seed orchard should be a standard practice in the operational implementation of MCP.     

Changes in growth performance and fecundity of Eucalyptus camaldulensis and E. tereticornis during domestication in southern India

Bulk seedlots of two unpedigreed multiprovenance seed production areas (SPAs) each of Eucalyptus camaldulensis and Eucalyptus tereticornis and one pedigreed seedling seed orchard (SSO) of E. tereticornis were planted in genetic gain trials at three southern Indian trial sites. At the time of seed collection, fewer than 30% trees flowered in these orchards, except in one E. camaldulensis SPA where 73% of the trees flowered, which had an estimated outcrossing rate of 86%. The E. tereticornis SSO was dominated by pollen from five highly fecund families of the Indian Mysore gum land race, which contributed 59% of the fruits produced. The SPA and SSO seedlots were compared with a bulked natural-provenance seedlot of E. camaldulensis (Morehead, Laura, and Kennedy Rivers, Queensland), another natural-provenance seedlot (Petford, Queensland), commercial eucalypt clones at two sites, and a Mysore gum seedlot at one site. At 3 years, progeny from all the four SPAs displayed good survival (79–93%) and performance similar to that of the natural provenances and the commercial clones. Progeny from the E. tereticornis SSO had significantly lower growth (at two sites) and lower survival at all three test sites. The Mysore gum seedlot displayed high fecundity and lower growth but better survival than the SSO progeny. Seed orchard genetic composition and flowering contributions thus affected progeny performance and the extent to which orchard genetic diversity was captured in the progeny. SPA progeny displayed greater fecundity than the natural provenances, indicating a response to selection for fertility.     

A comparison of the effect of genetic improvement, seed source and seedling seed orchard variables on progeny growth in Eucalyptus nitens in South Africa

Eucalyptus nitens is an important forestry species grown for pulp and paper production in the temperate, summer-rainfall regions of South Africa. A tree improvement programme has been ongoing at the Institute for Commercial Forestry Research for two decades, but genetic improvement in the species has been slow due to delayed and infrequent flowering and seed production. Three trials were established, firstly, to quantify the gains that have been made in the first generation of improvement in the breeding programme and, secondly, to establish whether a number of seed source and orchard variables influence the performance of the progeny. These variables were the amount of flowering trees in the seed orchard, year of seed collection, seed orchard origin and composition of seed orchard bulks. Diameter at breast height and tree heights were measured in the trials at between 87 and 97 months after establishment, and timber volumes and survival were calculated. Improved seed orchard bulks performed significantly better (p?<?0.01) than unimproved controls in the field trials. Genetic gains ranging from 23.2 to 164.8 m³?ha^?1 were observed over the unimproved commercial seed. There were significant differences (p?<?0.01) in progeny growth between the levels of seed orchard flowering, with higher levels of flowering (≥40 %) producing substantially greater progeny growth than lower flowering levels (≤20 %). The seed orchard had no effect on progeny growth in this trial series. This suggests that seed collected from any of the four seed orchards tested will produce trees with significant improvement in growth.     

Pollen tube growth and early ovule development following self- and cross-pollination in<Emphasis Type="Italic"> Eucalyptus nitens</Emphasis>

Controlled self- and cross-pollinations were conducted on flowers of five mature Eucalyptus nitens trees. Levels of self-sterility of the trees ranged from 25.8 to 93.6%. Pollen tube numbers in styles and ovule penetration by pollen tubes was investigated 2 weeks after pollination by fluorescence microscopy. There were no significant differences between treatments in the number of pollen tubes present in styles or in the percentage of ovules penetrated by pollen tubes. Embryology of material harvested 2 and 4 weeks after pollination was investigated by bright-field microscopy. Fertilisation had taken place by 2 weeks after pollination with nearly every ovule showing evidence of fertilisation. Cross-pollination resulted in a greater proportion of healthy, developing ovules, at both 2 and 4 weeks after pollination, compared with self-pollination. The proportion of degenerating ovules increased from 2 to 4 weeks after pollination. The reduced ability of E. nitens to set self-pollinated seed compared with cross-pollinated seed appears to be controlled by a post-zygotic mechanism. Differences in ovule size may potentially assist in the identification of trees incapable of setting self-pollinated seed.     

Patterns of pollen flow in a dense population of the insect-pollinated canopy tree species Castanopsis sieboldii

Insect pollinations of tree species with high-density populations have rarely been studied. Since the density of adults can affect effective pollen dispersal, short-distance pollination, even by insects, may frequently occur in high-density populations. To test this prediction, we investigated pollination patterns in a high-density population of the insect-pollinated canopy tree species Castanopsis sieboldii by paternity analysis using genotypes at 8 microsatellite loci of 145 adult trees and 439 seeds from 11 seed parents in a 4-ha plot. We then explored their genetic effects on the population by calculating other population genetics parameters. Although C. sieboldii has high potential for long-distance dispersal of pollen (as indicated by a fat-tailed dispersal kernel), the cumulative pollination at the local scale was spatially limited and strongly dependent on the distance between parents due to the high density of adults. Genetic diversity estimates for pollen pools accepted by each seed parent converged on a maximum as the effective number of pollen parents increased. The genetic diversity of pollen pool bulked over all the seed parents from inside the plot did not differ from that of the total pollen pools. Therefore, although pollen flow from distant pollen parents may help to maintain the genetic diversity of offspring, pollen parents neighboring seed parents may be the main contributors to the genetic diversity of the offspring at the seed stage.     

Increased inbreeding and inter-species gene flow in remnant populations of the rare <Emphasis Type="Italic">Eucalyptus benthamii</Emphasis>

Eucalyptus benthamii Maiden & Cambage is a forest tree of interest for conservation and plantation forestry. It is vulnerable to extinction, occurring on the alluvial floodplains of the Nepean River and its tributaries, south-west of Sydney, Australia. These floodplains were largely cleared of native vegetation for agriculture by the mid-1800s. Flooding of the Cox Valley for Sydneys water supply further decreased the species distribution. The species is now confined to one population of approximately 6500 trees in the Kedumba valley and three remnant populations on the Nepean River at Bents Basin (about 300 trees), Wallacia (nine trees) and Camden (about 30 trees). Genetic analysis of the four populations using microsatellite markers revealed significant divergence among all populations, despite the Bents Basin, Wallacia and Camden remnants being separated by distances of only a few kilometres. Trees in these populations have been estimated to range from 35 to 200 years old, suggesting genetic divergence among populations occurred prior to land clearing. To investigate the impact of fragmentation on the next generation, outcrossing rates were estimated from 41 families. While no direct relationship was found between population size and outcrossing rates, fragmentation and the isolation of trees appears to have resulted in higher levels of selfing and biparental inbreeding in seed collected from the Camden and Wallacia remnants. There was also evidence from seedling morphology that inter-species gene flow increased with fragmentation since 20% of the progeny from Camden and 30% of the progeny from Wallacia were hybrids. Seed viability and germination rates were significantly lower in the remnant populations, reducing their value as seed sources for regeneration and plantation forestry. To maintain the genetic integrity of the remnant populations, germplasm should be sourced from the local area. Outcrossed, non-hybrid seed could be produced by controlled pollination in ex-situ conservation stands or by using seedling morphology and microsatellites to screen seedlings from the remnant populations.     

RAPD Detection of Pollen Contamination in Cross Breeding of Liriodendron (in English)

Based on the biology peculiarity of Liriodendron L., the non-bagged pollination technique was used widely in cross breeding of the genus. Theoretical analysis and indirect detection indicated that the pollen contamination rate of this pollination technique was no higher than 1%. But there is no evidence from direct detection by now. The pollen contamination rate produced in this pollination technique, for the first time, was detected by means of RAPD markers in this study. The results revealed that all the 93 progenies detected, derived from the non-bagged pollination technique, were progenies of the purpose male tree of the cross. No pollen contamination was found. Because the frequency of the 4 paternal marker fragments selected for the detection were relatively low in the population, the reliability of the pollen contamination rate detected was very high (>99%). Therefore, the non-bagged pollination technique is viable in Liriodendron . The authors also considered that RAPD markers had higher potential of use in other fields of botanic study such as pollen competition, pollen flow, pollen contamination of forest seed orchard, etc.     

用RAPD标记检测鹅掌楸属种间杂交的花粉污染

根据鹅掌楸属 (LiriodendronL .)的生物学特点 ,实践上常采用不套袋杂交授粉技术 ,理论分析和间接检测结果证明这种杂交授粉方式的花粉污染率低于 1% ,但到目前为止仍缺乏直接的检测证据。本试验首次采用RAPD标记对鹅掌楸属种间不套袋杂交授粉的花粉污染率进行了检测 ,结果证明 93个受检不套袋杂交授粉子代均来自目的父本 ,而非花粉污染所致。通过对所用 4个父本标记谱带在试验群体中出现频率的测定和分析 ,证明这种检测结果的可靠性大于 99% ,从而认为对鹅掌楸属进行不套袋杂交授粉是可行的。并就这一方法在植物学研究领域的应用潜力进行了讨论     

Effect of defoliation on grass growth. A quantitative review

This study describes the seasonal patterns of seed and cone abortion in natural Pinus halepensis trees and assesses the effects of pollen quantity, tree size and cone location on seed and cone abortion. The cone-set ratio was similar to the expected value, based on literature on woody perennials. The seed-ovule ratio, however, was almost twice as high as its expected value. The investment in protective cone elements was high and did not vary with the seed-ovule ratio of a cone. Pollination factors influenced cone abortion, as indicated by the high abortion rate at the end of the pollination period. Furthermore, abortive cones had lower pollination rates and lower pollen loads than well developed cones. Effects of resource availability were assessed as effects of tree size and cone position on twigs. Small trees aborted more cones than big trees and cone abortion was higher in apical cones than in basal cones. Abortion in P. halepensis is selective, mediated by both pollen quantity and resource availability. The relative importance of pollen and resources is suggested to be flexible, probably varying between trees and years. The high seed-ovule ratio of P. halepensis is the result of high pollination rate and selective abortion. The selective abortion might be due to the high allocation to protective cone elements relative to the allocation to seeds.     

Genetic diversity in a seed production population vs. natural populations of Sitka Spruce

Isozyme analysis was applied to estimate the level of variation and the genetic structure of a seed-production population (i.e., seed orchard) and 10 range-wide natural populations of Sitka spruce (Picea sitchensis (Bong.) Carr.). Gene diversity and heterozygosity estimates were comparatively high in both the seed orchard and the natural populations studied. The seed orchard population showed a significantly higher number of alleles per locus and percentage of polymorphic loci. Though not significant, mean heterozygosity of the seed orchard was higher than that observed for all natural populations. Genetic distance analysis indicated that the seed-orchard population was genetically similar to three natural populations from which the parent trees were selected. Parent trees sampling breadth has been identified as the major cause for the observed increased level. The impact of recurrent selection and seed orchard biology and management on maintaining the genetic diversity is discussed.     

The nature of inbreeding in a seed orchard of Douglas fir as shown by an efficient multilocus model

Summary The amounts of self-fertilization versus consanguineous matings (as measured by effective selfing) was estimated in a seed orchard of Douglas-fir, using progeny array data at six allozyme loci. The orchard is family structured, consisting several grafts (clones) and/or open-pollinated (o-p) progeny from each of several plus-trees. Population-wide selfing rates were found to be 7% for the o-p trees and 2% for the cloned trees. Estimates of mating system parameters for individual trees showed this difference for average outcrossing rate t (1) still largely remained when outcrossingpollen gene frequency p was not allowed to vary among trees and (2) disappeared when p was allowed to vary among trees. Under this joint t and p estimation, o-p trees showed both significant variation of t (based upon a one-way ANOVA grouped by common plus-tree) and significant regressions of p on ovule genotype (indicative of consanguineous matings); cloned trees showed neither. This higher rate of consanguineous mating for o-p trees might be explained by the larger and more variable size of o-p families in the orchard. Estimates of outcrossing rate t and outcrossingpollen gene frequency p were based upon a multilocus model which makes full use of the information in the data. The increased information it gives over observed outcross models is equivalent to adding 30–50% more loci, and it gives enough degrees of freedom to jointly estimate t and p for individual trees (individual progeny arrays) under certain conditions. In addition, inclusion of megagametophyte data nearly doubles the information about the mating system of individual trees.     

Pollination in Verbascum thapsus (Scrophulariaceae): the advantage of being tall

According to the "effective pollination" hypothesis, tall stature resulting from strong apical dominance attracts greater pollinator visitation, thus allowing larger pollen loads and/or greater outcrossing rates, which in turn produces more vigorous offspring with greater genotypic variability and/or less inbreeding depression. Components of this hypothesis were tested in Verbascum thapsus, which commonly grows unbranched to over 2 m tall with strong apical dominance suppressing all axillary meristems. A natural population survey indicated that plants with visiting pollinators were significantly taller than their nearest neighboring individuals not possessing a visiting pollinator. Plants in natural populations with excluded pollinators produced seeds via a delayed selfing mechanism. However, delayed selfing under pollinator exclusion resulted in only 75% of the seed set obtained with natural pollinators. Under natural pollination, emasculated flowers experienced a 50% reduction in pollen deposition by the time of flower closure but only a 5% reduction in seed set relative to intact flowers. Hence, taller plants attracted more pollinators and maximum seed set could not be achieved without pollinators. Comparison of seed set and seed mass in plants that were artificially selfed and artificially crossed (in both the greenhouse and in natural populations) indicated that plants were fully self-compatible with no evidence of early-acting inbreeding depression. However, this does not exclude the possibility that inbreeding depression is manifested in later life stages. The results suggest that V. thapsus has a mixed mating system with potential for reproductive assurance and various levels of outcrossing depending on variables affecting pollinator availability (e.g., population size).     

Pollen Dispersal Between Isolated Trees in the Brazilian Savannah: A Case Study of the Neotropical Tree Hymenaea stigonocarpa

This case study examines the pollen dispersal distance, pollen dispersal patterns and intra‐family genetic structure for isolated trees in pastures of the bat‐pollinated Neotropical tree species Hymenaea stigonocarpa using six microsatellite loci and parentage analysis. The sampling included 28 grouped trees (referred to as the population) and six isolated trees in pastureland along a highway in Mato Grosso do Sul State, Brazil. From the population, we sampled 137 seeds from 12 seed‐trees, and from the isolated trees, we sampled 34 seeds from two seed‐trees. The results showed that pollen was dispersed over long distances (reaching 7353 m) and therefore the spatially isolated trees were not reproductively isolated. The pollen immigration rate in the population was also high (31%). Isolated trees presented a higher selfing rate (s=26%) than trees in the population (s=12%), suggesting that the spatial isolation of the trees increased selfing. However, selfing was responsible for only 30 percent of the inbreeding in offspring and mating among relatives was 70 percent. In the population, excluding selfing, ca 72 percent of the pollen was dispersed over distances <1000 m (average: 860 m). For the two isolated seed‐trees, excluding selfing, the average pollen dispersal distance was 5229 m. The results demonstrate that although pollen can be dispersed over long distances for H. stigonocarpa isolated trees, a high percentage of pollen comes from the same tree (selfing) and mating was correlated. Consequently, seeds must be collected from a large number of seed‐trees for conservation purposes.     

西双版纳热带雨林对叶榕传粉生物学

研究了西双版纳热带雨林地区雌雄异株植物对叶榕(Ficus hispida L.)的生物学、传粉物候学以及榕小蜂(Ceratosolen solmsi marchali Mayr)的传粉和繁殖行为.研究结果表明:雌雄异株的对叶榕与其他雌雄同株的榕属植物不同,它的种子形成与传粉者有着更为复杂的相互关系.对叶榕一年结隐花果6～8次,结果高峰期4～5次,其中雄性植株仅产生花粉和孕育榕小蜂,而雌性植株(无雄蕊)则需榕小蜂带花粉进入隐花果内,进行传粉授精,使之发育成种子.对叶榕的成熟花粉不能从花药开裂处自行散发出来,必须由榕小蜂采集才能散落.榕小蜂雌蜂羽化、交配后,找到雄花区,用足、触角、口器在推动中采集花粉.雌蜂飞出熟榕果找寻雌株或雄株榕树上的幼嫩隐花果,一般需3～67 min;一部分雌蜂在雄株中寻找幼嫩的隐花果,进去产卵繁殖,另一部分雌蜂则寻找雌株雌花期嫩隐花果进去传粉.雌蜂在雌株榕树的隐花果内传粉时间为15～23 h,在雄株榕树的隐花果内产卵时间为6～9 h.对叶榕小蜂在雌株上进入单个隐花果的数量多少关系到雌花结实率;观察表明,每个隐花果最佳进蜂数为2头;榕小蜂传粉后榕树成熟种子形成率在54.1%～82.5%之间,平均为73.8%;而在雄株上雌蜂进蜂数量则关系到榕小蜂在隐花果内的产卵率,每个隐花果最佳进蜂数为3～4头,产卵率在72.3%～93.8%之间,平均为84.4%.     

Marker-based parentage analysis facilitates low input ‘breeding without breeding’ strategies for forest trees

Controlled crosses and progeny testing are important components of tree breeding programs. Recently, a new approach, ‘breeding without breeding’ (BWB), has been proposed to obtain structured pedigrees for the breeding and testing from wind-pollinated progenies; the technique uses high-resolution markers instead of conventional approaches. The BWB approach is attractive for outcrossing conifers where the breeding cycle is long and reproductive maturity is often delayed. For the application of the BWB approach, the accurate assignment of parents is essential. The first step in the application of the BWB approach is to conduct tests into the reliability of paternity and parent-pair exclusion procedures in complex situations. In this study we conducted multi-locus-based empirical and simulation analyses for a Scots pine seed orchard crop, in order to develop the appropriate parentage assignment techniques for BWB and to investigate whether pedigrees from a seed orchard crop can be determined with sufficient accuracy. The results were promising, as 93–97% of the seeds generated by mating among the seed orchard clones were correctly assigned to a parent-pair. When mating occurred with foreign pollen, the success rate of identifying mother clones was 60–78%. Based on these results, we propose three novel low input breeding strategies for forest trees. The principles of the different options and their potential benefits and costs are described and discussed using Scots pine as a case study.     

Consistency of resistance to attack by the green spruce aphid (Elatobium abietinum Walker) in different ontogenetic stages of Sitka spruce

Abstract 1 The susceptibility of different genotypes of 29‐year‐old Sitka spruce to damage by the green spruce aphid, Elatobium abietinum, was investigated in a progeny trial where aphid damage on individual trees had previously been assessed twice in an earlier stage of ontogenetic development. The progeny trial comprised 14 open‐pollinated families originating from a clonal seed orchard that had been established using mature spruce trees selected for aphid resistance. 2 Previous investigations had demonstrated that resistance was inherited by the offspring, and that differences in resistance between progenies of the individual orchard clones were highly significant. 3 Susceptibility to aphid attack was recorded as the percentage loss of previous year's needles. Differences in susceptibility recorded between the juvenile trees were found to persist after the trees had developed into the closed‐canopy, sexually reproducing stage. Needle loss of the families was significantly less than that of the reference population of Sitka spruce. 4 Hybrids between Sitka spruce and white spruce were defoliated more heavily than pure Sitka spruce, and the difference increased with age. 5 Family heritability of resistance was estimated as 0.60 compared to 0.73 when the trees were assessed in the juvenile stage. The genetic correlation based on family means between damage in the juvenile and sexually reproducing stand was high (0.83), indicating a high consistency of resistance to the aphid over years and ontogenetic stages. 6 A skewed distribution of defoliation indicated that major genes are involved in the expression of resistance, and that the genetics behind resistance has a nonadditive component.