Paternal and maternal effects on the response of seed germination to high temperatures in Eucalyptus globulus

Context

High temperature stress in nurseries germinating Eucalyptus globulus seed is an important problem affecting germination synchrony and rate. Where there is a risk of high-temperature stress, then the choice of female parent may be important. This issue is particularly relevant to the production of full-sib families from mass-supplementary pollination where there may be opportunities for seed producers to manipulate the directionality of the crossing done in seed orchards.

Aims

This study aimed to quantify the maternal versus paternal influence of seed sensitivity to high temperature stress during germination.

Methods

A diallel crossing scheme involving four genotypes was used to test the relative importance of male and female genetic influences on the germination and development of E. globulus seed and their response to high temperature stress. Seed was germinated at optimum (25°C) and supra-optimal (32°C and 37°C) temperatures, and six traits describing the proportion and rate of seed germination and early seedling development were assessed.

Results

Both paternal and maternal effects affected the germination response, arguing for at least some influence of the nuclear genotype of the embryo. However, the response to high temperature stress was more influenced by the maternal than paternal parent.

Conclusion

Both the male and female genotype may affect various aspects of seed germination and early seedling development independent of seed size; however, some facets of the germination response will be mainly affected by the female parent.     

Improving the estimation of landscape scale seed dispersal by integrating seedling recruitment

? Context

Dispersal and recruitment play a critical role in determining the abundance and the spatial structure of regeneration.

? Aim

In this study, we estimated landscape scale seed dispersal using the inverse modeling method by fitting seedling counts to seed tree location and fertility in the European silver fir Abies alba Miller.

? Methods

Seed trees and seedlings from three age cohorts were counted in 30 plots on Mont Ventoux (southeastern France) at elevations from 995 to 1,605?m, where the following ecological variables were measured: elevation, slope, aspect, light availability, and tree density. We developed and fitted a dispersal model, including a new parameter, recruitment rate, which depended both on the ecological characteristics of the plots and on seed production.

? Results

Elevation was the factor that affected seedling recruitment the most, with an optimum value at around 1,200?m. Estimated A. alba seed dispersal distances were short (median values for the three cohorts, respectively, 16.4?C13.2?C19.6?m).

? Discussion

We demonstrated that including the ecological characteristics of plots and post-dispersal recruitment processes realistically reduced estimates of seed dispersal distances which are otherwise grossly over-estimated using inverse modeling procedures.     

Pedigree and mating system analyses in a western larch (Larix occidentalis Nutt.) experimental population

?The mating pattern and gene flow in a western larch (Larix occidentalis Nutt.) experimental population was studied with the aid of microsatellite markers and a combination of paternity-mating system analysis. The commonly difficult to assess, male gametic contribution was determined with 95% confidence and its impact on genetic gain and diversity was determined.

? Male fertility success rate ranged between 0 and 11%. Male reproductive output parental imbalance was observed with 50% of the pollen being produced by the top 5% of males while the lower 39% males only produced 10% of the pollen.

? A significant difference was observed between male effective population size (genetic diversity) estimates from paternity assignment compared to those based on population’s census number (21 vs. 41); however, this difference did not affect estimates of genetic gain.

? A total of 221 full-fib families were identified (sample size range: 1–8) and were nested among the studied 14 seed-donors.

? A combination of paternity-mating system analysis is recommended to provide a better insight into seed orchards’ mating dynamics. While pollen flow tends to inflate mating system’s outcrossing rate, the paternity analysis effectively determined the rate and magnitude of contamination across receptive females.

     

Mast seeding in deciduous forests of the northern Apennines (Italy) and its influence on wild boar population dynamics

Context

Pulsed food resources may strongly affect the population dynamics of several consumer species, with consequences on the ecosystem. One of the most common pulsed resources is forest mast seeding.

Aims

We analysed mast seeding in deciduous forests in a mountainous area of northern Apennines and its effect on population dynamics of wild boar (Sus scrofa L.).

Methods

We performed a quantitative, 20-year analysis on annual seed production in Turkey oak (Quercus cerris L.), beech (Fagus sylvatica L.) and chestnut (Castanea sativa Mill.) forest stands using litter traps. The wild boar population density was estimated by means of drive censuses and hunting bag records. The role of other biotic (density of predators) and abiotic (climate) factors potentially affecting wild boar mortality was also investigated.

Results

Turkey oak and chestnut showed high levels of seed production, whereas lower levels were found in beech. The pulsed resources of chestnut and Turkey oak positively affected piglet density. Analyses also highlighted the influence of snow cover and wolves on wild boar population dynamics.

Conclusion

Wild boar can be considered a pulse rate species, the management of which can be improved by annual monitoring of seed production.     

Optimal seed water content and storage temperature for preservation of Populus nigra L. germplasm

Context

Black poplar (Populus nigra L.) is an alluvial forest tree species whose genetic pool is decreasing in Europe. Poplar trees produce short-lived seeds that do not store well.

Aim

The feasibility of seed storage in conventional and cryogenic conditions after their desiccation from water content (WC) of 0.15 to 0.07 g H₂O g^?1 dry mass (g g^?1) was investigated.

Methods

Seed germinability was evaluated (seeds with a radicle and green cotyledons were counted) after storage of seeds for a period of 3 to 24 months at different temperatures: 20°, 10°, 3°, ?3°, ?10°, ?20° or ?196°C.

Results

Seeds desiccated to a 0.07 g g^?1 WC can be stored successfully at ?10 °C and ?20 °C for at least 2 years. A significant decrease in germination was observed only after 12 months of seed storage (WC 0.15 g g^?1) at temperatures above 0 °C. We demonstrated that both fresh (0.15 g g^?1 WC) and desiccated (0.07 g g^?1 WC) seeds can be preserved at ?196 °C for at least 2 years.

Conclusions

Seed storage temperature and time of storage were statistically significant factors affecting seed storability. The presented data provide a foundation for the successful gene banking of P. nigra seeds.     

Fire severity as a key factor in post-fire regeneration of Pinus pinaster (Ait.) in Central Portugal

Context

Mediterranean pine woodlands are strongly affected by wildfires; however, there are knowledge gaps in the role of fire severity on Pinus pinaster Ait. regeneration.

Objectives

The principal questions were: (a) does post-fire regeneration of Maritime Pine differ where canopies were consumed to a low vs. high degree and (b) which factors, besides fire severity, could explain these differences.

Methods

Pine recruitment was monitored from 2 to 36?months after a summer wildfire in 18 25?m² plots, equally divided over two fire severity classes based on crown consumption. Besides the degree of crown consumption, three quantitative fire severity indices as well as post-fire site conditions, seed input and understory vegetation recovery were measured.

Results

Pine seedling densities were consistently higher in the plots with low than high crown consumption but due to marked spatial variability, they were only significantly different at two out of the eight sampling occasions. This variability could be explained by a quantitative index based on the diameter of twigs, as well as by seed input and post-fire site conditions (ash and litter cover).

Conclusion

Fire severity was found to strongly affect the pine recruitment following wildfire, using both a qualitative visual severity index and a quantitative, more labour-intensive one.     

Genotypic parameters of wood density and fiber traits in triploid hybrid clones of Populus tomentosa at five clonal trials

? Context

A clear understanding of the genetic control of wood properties is a prerequisite for breeding for higher wood quality in Populus tomentosa Carr. hybrid clones.

? Aims

The experiments aimed at unraveling genetic and environmental effects on wood properties among triploid hybrid clones of P. tomentosa.

? Methods

We used 5-year-old clonal trials established in Northern China to assess the heritability of wood density and fiber traits. Two hundred seventy trees from nine clones were sampled in five sites.

? Results

Site had a very significant effect on all recorded traits. Despite this large site effect, a tight genetic control was detected and clonal repeatability varied between 0.53 and 0.95. Significant genotype?×?environment interactions were detected for most of the traits. Moderate to tight correlation were evidenced among traits but they were not consistent with that in several cases that were site-dependent.

? Conclusions

Our results revealed a tight genetic control over several wood properties and therefore breeding programs might be able to improve wood density, fiber length, and coarseness in these hybrids.     

Seedling resistance to Phytophthora cinnamomi in the genus Abies

? Context

Root rot and stem canker caused by Oomycete species belonging to the genus Phytophthora often seriously limit culture of true firs (Abies spp.)

? Aim

An investigation of the variation of resistance among Abies species to Phytophthor a cinnamomi was carried out to identify potential sources of resistance in the genus.

? Methods

Thirty-two Abies species were grown in a greenhouse for 2 and/or 3?years from seed. Seedlings were moved to an outdoor lath house, inoculated with rice grains colonized with P. cinnamomi, and subsequent mortality was assessed biweekly for 16?weeks.

? Results

Disease developed rapidly resulting in 88.1?% overall mortality 16?weeks after inoculation. Mortality was less in two of the eight taxonomic sections of the genus evaluated, Momi (0.65?±?0.0252) and Abies (0.79?±?0.0193). Mortality in all other sections exceeded 93?%. Final species mortality ranged from 10.6?% (Abies firma) to 100.0?% (several species).

? Conclusions

Although several caveats apply, results have identified potential sources of Abies to be used as (1) resistant planting stock, (2) grafting rootstock, and (3) parents in hybridization/backcrossing programs in order to mitigate losses caused by P. cinnamomi.     

Clonal variations in nutritional components of <Emphasis Type="Italic">Pinus koreansis</Emphasis> seeds collected from seed orchards in Northeastern China

From four Korean pine (Pinus koraiensis) orchards, 60 clones were selected and analyzed for the fatty acid and amino acid components of the seeds to reveal the variations and correlations of the seed characteristics among the clonal source orchards and clones. The nutritional components of the seeds of the P. koraiensis trees exhibited rich genetic variation; the variation coefficient of the fatty acids was 2.24–66.83 %, while the variation coefficient of the amino acids was 14.70–38.88 %. Relatively high genetic-improvement potential exists for the nutritional components of the seeds. The phenotypic differentiation of the fatty acid and amino acid components reveals that variation within the population (85.18 %) was the primary source for the variation of the fatty acid components; variation among the orchards (63.08 %) was the primary source of the variation of the amino acid components. Data drawn from various clonal source orchards all showed that the seed characteristics were highly controlled by heritability (h² > 80 %), and the seed characteristics of the P. koraiensis trees exhibited a similar genetic gain trend. The principal components were analyzed to obtain the comprehensive principal component value for each clonal seed orchard. Twelve clones were selected based on a clonal selection rate of 20 %. Correlation and multiple stepwise-regression analyses were conducted, considering different location conditions, to reveal the stable correlations between the seed characteristics to facilitate improvements of the seed yield of P. koraiensis trees and the clonal selection. Species of real characteristics in P. koraiensis were controlled by higher heritability. Genetic gain was obtained by selecting of superior clones.     

Genetics of wood quality attributes in Western Larch

Context

Wood quality traits are important to balance the negative decline of wood quality associated with selection for growth attributes in gymnosperm breeding programs. Obtaining wood quality estimates quickly is crucial for successful incorporation in breeding programs.

Aims

The aims of this paper are to: (1) Estimate genetic and phenotypic correlations between growth and wood quality attributes, (2) Estimate heritability of the studied traits, and (3) Assess the accuracy of in situ non-destructive tools as a representative of actual wood density.

Methods

Wood density (X-ray densitometry), tree height, diameter, volume, resistance drilling, acoustic velocity, and dynamic modulus of elasticity were estimated, along with their genetic parameters, for 1,200, 20-year-old trees from 25 open-pollinated families.

Results

Individual tree level heritabilities for non-destructive evaluation attributes were moderate ( $ {\widehat{h}}_i^2=0.37-0.42 $ ), wood density and growth traits were lower ( $ {\widehat{h}}_i^2=0.23-0.35 $ ). Favorable genetic and phenotypic correlations between growth traits, wood density, and non-destructive evaluation traits were observed. A perfect genetic correlation was found between resistance drilling and wood density (r _G ?=?1.00?±?0.07), while acoustic velocity and dynamic modulus of elasticity showed weaker genetic correlations with wood density (r _G ?=?0.25?±?0.24;?0.46?±?0.21, respectively).

Conclusion

This study confirmed that resistance drilling is a reliable predictor of wood density in western larch, while the weak genetic correlations displayed by acoustic velocity and dynamic modulus of elasticity suggest limited dependability for their use as fast in situ wood density assessment methods in this species.     

Genetic variation and genotype by environment interaction in the susceptibility of <Emphasis Type="Italic">Abies nordmanniana</Emphasis> (Steven) Spach to the fungus <Emphasis Type="Italic">Neonectria neomacrospora</Emphasis> (Booth &amp; Samuels) Mantiri &amp; Samuels

Key message

Pronounced clonal variation and moderate to high broad-sense heritability estimates of susceptibility to Neonectria neomacrospora were found in Abies nordmanniana in three sites. Significant genotype by environment (G × E) interaction was detected across sites.

Context

Nordmann fir, a widely used Christmas tree species in Europe, has, since 2011, been increasingly damaged by a canker disease caused by Neonectria neomacrospora.

Aims

The objective was to study the genetic variation and genotype by environment interaction in the susceptibility of Nordmann fir to N. neomacrospora.

Methods

Damage caused by N. neomacrospora was evaluated using a visual scale in three Nordmann fir clonal seed orchards in Denmark, partly containing the same clones.

Results

Damage due to N. neomacrospora was substantial at all three sites, and no clone was completely resistant to N. neomacrospora, but a large genetic variation in the susceptibility was detected among clones. Estimates of single-site individual broad-sense heritability for susceptibility varied between 0.38 and 0.47. The average type-B genetic correlation for damage score across sites was 0.34.

Conclusion

Genetic variation was very pronounced, and significant G × E interactions were detected for susceptibility. Further investigations of narrow-sense heritability, expression of the trait in younger material, and identification of the cause of G × E for N. neomacrospora susceptibility in Nordmann fir across different sites are recommended.

     

Genetic structures of Calophyllum inophyllum L., a tree employing sea-drift seed dispersal in the northern extreme of its distribution

? Context

Little is known about the potential of gene flow and resulting genetic structures of trees employing sea-drifting seed dispersal in island populations.

? Aims

Current genetic structure and the magnitude of historical gene flow were estimated in island populations of Calophyllum inophyllum L., a typical plant employing sea-drifting seed dispersal.

? Methods

Samples were collected from the northern extreme of the species’ distribution (Taiwan and the Sakishima, Daito, and Ogasawara Islands, Japan) and genotyped using 15 EST-SSR markers. Genetic differentiation (F _ST and AMOVA), genetic structure (STRUCTRE analysis), and historical gene flow (assignment testing) were determined.

? Results

Frequent gene flow within and rare gene flow among island groups was determined using assignment testing. Clear genetic structures were also detected using the STRUCTURE analysis, which demonstrated differentiation between dominant clusters among geographically constructed island groups.

? Conclusions

The potential for gene flow via sea-drifting seed dispersal was high, and this was possible even among small islands. However, the extent and frequency of gene flow were not great enough to prevent genetic differentiation in a range of over a few hundred kilometers.     

The role of cold storage and seed source in the germination of three Mediterranean shrub species with contrasting dormancy types

Context

The use of native species in ecological restoration is highly recommended but, in practice, it is often impaired by knowledge gaps in the germination ecology of suitable species.

Aims

This study aimed to assess the role of storage conditions and seed source on the germination of three Mediterranean shrub species with contrasting types of dormancy.

Methods

Ripe fruits were harvested at two or three distant locations in mainland Portugal. Seeds were subjected to three treatments consisting in different storage conditions: cold storage at low and high moisture conditions, plus a control. Five replicates of up to 30 seeds were placed under constant temperature conditions and germination was monitored weekly during 14 weeks.

Results

The effect of cold storage at high moisture on germination differed between the three species and seed source played a significant role in the germination of all three species. In the case of the species with dormancy, the observed differences in germination could reflect changes in the species’ dormancy degree or sensitivity to dormancy breaking factors across their geographical range. In the case of Pistacia lentiscus (no dormancy), the results suggested a possible adaptation of the northern seed source to high moisture conditions.

Conclusions

The observed differences between species agreed well with their dormancy types, and the seed source-related differences could be adaptive features, as they seemed related with local climate conditions.     

Genetic parameters for grain angle in 28-year-old Norway spruce progeny trials and their parent seed orchard

? Sawn wood which acquires twist during drying is a substantial problem for the sawmill industry and is to a large extent caused by spiralled grain in the tree.

? In this study, the feasibility of using spiral grain angles as a selection trait in Norway spruce (Picea abies (L.) Karst) tree breeding and the extent of grain angle and its breeding values were investigated. Grain angles under bark and diameter were measured at breast height in three 28-year-old Norway spruce progeny trials and in their parent seed orchard.

? The mean grain angle value was 1.76° in the progeny trials and 1.84° in the seed orchard. Estimated genetic standard deviations for grain angle were almost 1°. Progeny trial heritabilities (H ² > 0.3) were larger than the seed orchard heritability (H ² = 0.24). Genotype by environment interaction among the progeny trials was negligible for grain angle. Progeny trial grain angles exhibited genetic correlation with seed orchard grain angles in the range 0.66 to 0.84.

? Thus, mature wood grain angles are also under considerable genetic control, raising the opportunity to reduce the occurence of left-grained trees, which are prone to producing twisted wood.

     

Is there a risk-dilution effect of naturally fallen fruits on post-dispersal seed predation by wood mice?

Aims

The aim of this study was to test the hypothesis that heavy predation of fallen fruits reduces the predation of neighboring post-dispersed seeds.

Methods

We performed a seed/fruit removal cafeteria experiment to assess the effects of seed species, of fruit species, and of density of fallen fruits on seed predation by wood mice (Apodemus sp.). In total, 6,930 seeds and 9,660 fruits from seven species were used. A generalized linear mixed model procedure was used to test these effects.

Results

Seed predation was significantly affected by the species of both seeds and neighboring fruits, but not by their density. Multiple comparison tests showed that most of treatments tested had no significant effects of species and density of neighboring fruits on seed removal. However, seed removal was significantly lower in some treatments with fruits than in the treatments without fruits for one of the seven seed species tested. Seed removal of two species tested was significantly differed among some treatments with different fruit species.

Conclusion

Most of the results in this study do not support our overall hypothesis. However, a part of results supported our hypothesis, suggesting that seed removal is affected by complex interactions between the preference of wood mice for fruits and fruiting environment.     

Plasticity of reproductive allocation of a woody species (Ulex europaeus) in response to variation in resource availability

Context

While many woody perennials grow and reproduce in varying environments, their ability to modify their reproductive allocation under varying resource availability is unclear.

Aims

This study aimed to demonstrate the occurrence of plasticity of reproductive allocation in a pioneer woody species (Ulex europaeus).

Methods

We studied seed production in 144 plants under different irradiance and population densities. We measured their basal area, their whole shoot biomass and photosynthetic biomass, and their reproductive output (number of fruits per individual and number of seeds per fruit).

Results

We found that newly produced photosynthetic biomass was influenced by environmental variation, which in turn determined its reproductive output. In addition, in low light conditions investment in reproduction was more reduced than investment in growth indicating plasticity of reproductive allocation.

Conclusion

These results provide the first evidence for plasticity of reproductive allocation of a woody plant. It may lead to the ability of this pioneer species to survive and to continue to reproduce even at low rates in non-optimal shady habitats and to maintain a non-empty seed bank in forest systems with long unfavourable periods between two disturbances.     

‘Climatic factors control rodent seed predation in Pinus pinea L. stands in Central Spain’

? Context

Pinus pinea L. presents serious problems of natural regeneration in managed forest of Central Spain. The species exhibits specific traits linked to frugivore activity. Therefore, information on plant–animal interactions may be crucial to understand regeneration failure.

? Aims

Determining the spatio-temporal pattern of P. pinea seed predation by Apodemus sylvaticus L. and the factors involved. Exploring the importance of A. sylvaticus L. as a disperser of P. pinea. Identifying other frugivores and their seasonal patterns.

? Methods

An intensive 24-month seed predation trial was carried out. The probability of seeds escaping predation was modelled through a zero-inflated binomial mixed model. Experiments on seed dispersal by A. sylvaticus were conducted. Cameras were set up to identify other potential frugivores.

? Results

Decreasing rodent population in summer and masting enhances seed survival. Seeds were exploited more rapidly nearby parent trees and shelters. A. sylvaticus dispersal activity was found to be scarce. Corvids marginally preyed upon P. pinea seeds.

? Conclusions

Survival of P. pinea seeds is climate-controlled through the timing of the dry period together with masting occurrence. Should germination not take place during the survival period, establishment may be limited. A. sylvaticus-mediated dispersal does not modify the seed shadow. Seasonality of corvid activity points to a role of corvids in dispersal.     

Interspecific differences in the oleoresin production of Copaifera L. (Fabaceae) in the Amazon rainforest

? Context

Copaifera species produce an oleoresin of commercial importance that is widely extracted in Amazon communities.

? Aims

This paper addresses two questions. (1) What are the morphological characteristics of Copaifera species that influence oleoresin production? (2) How do different Copaifera species respond to repeated harvests?

? Methods

We performed a large-scale experiment in the Brazilian Amazon. We tapped 110 Copaifera trees belonging to four species, and several morphological tree characteristics were measured to determine their effect on oleoresin production.

? Results

The proportion of Copaifera reticulata and Copaifera paupera trees that yielded more than 1 ml oleoresin was higher than the other species. The oleoresin volumes from yielding Copaifera pubiflora trees were significantly higher than those from C. reticulata and C. paupera, with Copaifera multijuga yielding intermediate values. Interestingly, none of the studied morphological tree characteristics had a significant effect on the proportion of yielding trees. Hollowed trees yielded significantly smaller volumes than non-hollowed trees. Both the proportion of yielding trees and oleoresin volumes decreased from the first to the second harvests for C. reticulata and C. paupera; however, the opposite pattern was observed for C. pubiflora.

? Conclusions

Oleoresin production capacity varies by species, and management protocols should account for these differences.     

High negative genetic correlations between growth traits and wood properties suggest incorporating multiple traits selection including economic weights for the future Scots pine breeding programs

Context

The development of multiple trait selection indices for solid (structure) wood production in the Scots pine (Pinus sylvestris L.) breeding program requires genetic variances and covariances estimated among wood quality traits including stiffness.

Aims

Genetic control and relationships among Scots pine growth, fiber, and wood quality traits were assessed by estimating heritability, phenotypic and genetic correlation using a Scots pine full-sib family trial.

Method

Wood quality traits including clearwood and dynamic acoustic stiffness were measured using SilviScan and Hitman in a 40-year-old progeny trial and by sampling increment cores of 778 trees of 120 families. Genetic parameters were estimated using the mixed model by the ASReml software.

Results

Heritability ranged from 0.147 to 0.306 for growth, earlywood, transition wood and latewood proportion traits and from 0.260 to 0.524 for fiber dimension, wood density, MFA and stiffness traits. The highly unfavorable genetic correlation between diameter and whole core density (?0.479) and clearwood stiffness (?0.506) and dynamic acoustic stiffness (?0.382) was observed in this study.

Conclusion

The unfavorable genetic correlations between growth traits and stiffness indicate that multiple traits selection using optimal economic weights and optimal breeding strategies are recommended for the advanced Scots pine breeding program.     

A new approach for tracking seed dispersal of large plants: soaking seeds with 15N-urea

Context

Although various tracking methods have been used in many ecosystems to investigate seed dispersal and seedling recruitment, it is still difficult to measure seed dispersal patterns due to methodological challenges in tracking seed movement away from parent trees and in finding the locations of seedlings.

Aim

Here, we aimed to develop a new approach to track seed dispersal by animals in the field.

Methods

Our approach involves soaking seeds directly into ¹⁵N-urea solutions with different dosages to enrich them isotopically. This new method is expected to create a reliable differentiation between the enriched seeds and natural ones and consequently between the corresponding seedlings.

Results

We showed that acorns of Quercus variabilis and Cyclobalanopsis glauca and seeds of Pinus koraiensis soaked in ¹⁵N-urea solutions were successfully enriched. We did not find that δ ¹⁵N value of seeds was a linear function of ¹⁵N-urea soaking duration. However, with high urea dosage and extending soaking duration, the δ ¹⁵N values in seedlings of Q. variabilis and P. koraiensis were higher than those of normal plants. As expected, ¹⁵N isotope was significantly diluted in the growing seedlings germinated from ¹⁵N-enriched seeds. Using the ¹⁵N-urea soaking method, we successfully located five seedlings of Q. variabilis germinated from the enriched acorns in the field.

Discussion

The ¹⁵N-urea soaking technique is powerful in tracking seed dispersal and seedling recruitment. This new method solves some of the problems inherent in traditional methods for tracking secondary seed dispersal and could further improve the study of seed dispersal ecology.