Outcrossing Rate Research Articles

Patterns of Pollen Dispersal in an Invasive Population of Solanum rostratum (Solanaceae) in China

Paternity analysis, carried out on 13 microsatellite loci, was used to investigate pollen dispersal and mating patterns in an invasive population of Solanum rostratum in China. We determined a high outcrossing rate (0.81 ± 0.02) and found that all 174 offspring for which the father could be identified were outcross progeny. The mean pollen dispersal distance was 13.66 m (range 0.41–71.67 m); however, 59.2% of effective pollination events occurred at <10 m. Our results indicate substantial near-neighbor pollen dispersal and imply that successful invasion of S. rostratum is facilitated by a high level of pollen flow within the population.

Optimization of GA3 and row ratio for seed yield of a promising hybrid rice variety

GA3 application at the rate of 225 g/ha with 12 rows of cytoplasmic male stenile (CMS) line and two rows of restorer lines appeared to be the optimum for highest yield of rice. This combination found results of per out crossing rate (OCR) (3.29 t/ha) for F1 seed production.

Characterization of the mating system of a native perennial tetraploid herb, Silene stellata

Nursery pollination systems can range from obligate to facultative. In a system where generalists provide substantial pollination service, an important question is whether the cost of seed predation outweighs the benefit provided by the nursery pollinator to cause the plant to evolve toward more generalized pollination. Using a facultative system native to North America, we tested whether nursery pollinator vs. strictly mutualistic generalists affect mating-system parameters of the host plant and explored the implications for long-term coevolution. We used paternity analyses with 11 microsatellite markers to characterize the mating system of Silene stellata when pollination service is primarily through the nursery pollinator Hadena ectypa and generalist moths. Our experimental population of S. stellata was predominantly outcrossing (average outcrossing rate t = 0.83), and mating-system parameters were similar between pollinator groups. We detected significant correlations in both selfing and outcrossed paternity at the fruit and maternal family level, corresponding to limited pollen dispersal (mean = 3.9 m). Among individuals, variation in anther-stigma separation was positively associated with outcrossing rate, which suggests the importance of herkogamy in preventing selfing. Correlated paternity suggests that seeds from the same fruit and/or plants are sired by a limited number of pollen donors, resulting from low pollen dispersal and potential male-male competition. The similar mating-system parameters of the two pollinator groups suggest that selection for higher outcrossing in S. stellata is likely to be through floral design rather than through increased pollinator specialization with H. ectypa.

The role of sexual and vegetative reproduction in the population maintenance of a monocarpic perennial herb,Cardiocrinum cordatumvar.glehnii

AbstractBecause monocarpic perennial plants have only one reproductive opportunity in their entire life, they need to ensure offspring production. Some plants reproduce both sexually and vegetatively, and vegetative reproduction could possibly compensate for seed production. Therefore, the role and significance of these reproductive modes is likely to differ between monocarps and polycarps, which can reproduce many times.Cardiocrinum cordatumvar.glehniiis a monocarpic perennial that reproduces both sexually and vegetatively (bulblet formation). Here, we investigated the characteristics and contribution to population maintenance of sexual and vegetative reproduction to reveal the significance of these two reproductive modes in this species. First, we found that bulblet formation occurred in plants after the three‐leaved rosette stage. Second, resource allocation experiments revealed that although resources were mainly invested in fruit maturation after the flowering season, resource allocation was switched from sexual reproduction to vegetative reproduction if seed production was insufficient. Third, the outcrossing rate in this species varied greatly according to the environment surrounding the population. However, reproductive assurance by selfing kept seed production stable even if flowers did not receive sufficient pollen for full seed setviaoutcross pollination, and moreover, there was no intensive inbreeding depression. Finally, genotypic identification of ramets suggested that daughter ramets derived from vegetative reproduction received the space that the mother flowering ramet had occupied until the previous year.

Characterization of genetic diversity and structures in natural Glycine tomentella populations on the southeast islands of China

Glycine tomentella Hayata is a species of Glycine Willd. subgenus Glycine, and in China it is distributed along the southeast coast. In this study, 11 natural G. tomentella populations were collected and their genetic diversity levels and population structures were analyzed using 25 simple sequence repeat (SSR) markers. The number of alleles per locus averaged 7.16 and ranged from 2 to 17. The expected heterozygosity (He) per locus averaged 0.60, varying from 0.19 to 0.86. The G. tomentella populations on these Chinese islands showed a greater average genetic variation (60.96%) among populations and gene differentiation index (Gst= 0.607), and a lower average within-population genetic variation (33.47%) and gene flow (Nm= 0.162). In this study, these G. tomentella island populations were characterized by a relatively greater average multilocus outcrossing rate of 5.74%, which may the result of heterogeneity owing to the perennation of G. tomentella. A spatial autocorrelation analysis revealed that populations within a radius of approximately 30.45 km had positive and significant genetic relationships. The Neighbor-Joining (NJ) and STRUCTURE analyses strongly showed a pattern of ‘island differentiation’ for the populations on southeast islands of China and also suggested that some genetic interconnection occurred along the southeast coast of China. The F-statistics suggested that geographically different G. tomentella populations had specific population structures. We propose that when collecting this species as a genetic resource, every G. tomentella population should be sampled.

Micropropagation of Mespilus germanica L.

The data presented in this paper is supporting the research article “Variable seed behavior increases recruitment success of a hardwood tree, Zelkova serrata, in spatially heterogeneous forest environments” (Oyama et al., 2018) [1]. We provided the data of several ecological properties of the two types of the seeds (i.e. shoot seeds vs. single seeds) with distinctly different dispersal behaviors. We provide data of terminal velocity, which was measured by releasing 50 replicates of each seed type from a height of 5.0 m in dead air space in a gymnasium. We also show the data of germination cue [i.e. red:far-red (R:FR) ratios], which was examined in plant growth chambers that received three distinct R:FR ratios (0.1, 0.4, and 1.0; 16 h photoperiod) or no illumination. Further, we show the data of the rates of multi-locus outcrossing rates and biparental inbreeding in each of single- and shoot seeds. The mating system parameters were estimated by assaying a total of 80 shoot seeds and 70 single seeds that were randomly collected from Parent 1 and Parent 2 for five microsatellite loci. Finally, we show the data of hemispherical canopy photographs, which were taken at different distance from the adults using a digital camera equipped with a fisheye lens.

Implementation of directional simulation to estimate outcrossing rates in time‐variant reliability analysis of structures

AbstractTime‐dependent reliability analysis of structures by the use of an outcrossing approach normally requires the so‐called outcrossing rate to be estimated. A variety of methods has been recorded in the literature to evaluate this rate both for continues and discrete processes. Despite the availability of these methods, still more general and at the same time less sophisticated approaches are desired. In this paper, attempt is made to use the basic idea of “parallel system reliability formulation” to calculate the outcrossing rate for circumstances where the processes are continuous. These calculations are carried out by directional simulation. It is shown that this approach is simple to implement and may be used for the cases where the problem involves nonstationary processes and also for the cases where several limit state functions may have to be considered.

Why outcross? The abandon-ship hypothesis in a facultative outcrossing/selfing fungal species

Most species able to reproduce both sexually and asexually (facultative sexual species) invest more in sexual reproduction in stressful environment conditions. According to the abandon-ship hypothesis, plasticity for investment in sexual reproduction may have been selected in these species, allowing unfit genotypes to generate progeny carrying new advantageous allelic combinations. We tested this hypothesis in Aspergillus nidulans, a fungus able to reproduce asexually, or sexually, by outcrossing and/or haploid selfing (i.e. fusion of genetically identical haploid nuclei, causing immediate genome-wide homozygosity). We crossed various strains of A. nidulans in a non-stressful environment and a stressful environment containing a non-lethal dose of fungicide. Without stress, crosses preferentially generated haploselfed fruiting bodies, whereas stressful conditions significantly increased the outcrossing rate. Our results strongly support the abandon-ship hypothesis and suggest that, for parents with low fitness, the costs of investing in sexual reproduction may be compensated by the production of fitter progeny carrying beneficial allele combinations. Similarly, the progeny generated by outcrossing was less fit than that produced by haploid selfing in non-stressful environments, but fitter in stressful conditions, suggesting that outcrossing may have short-term advantages in stressful environments in A. nidulans.

On the adaptive value of monomorphic versus dimorphic enantiostyly in Solanum rostratum.

Enantiostyly is a reproductive system with heteromorphic flowers characterized by asymmetrical deflection of the style, either to the left or to the right of the floral axis. There are two types of enantiostyly. In monomorphic enantiostyly, plants produce the two types of flowers in the same individual. Dimorphic enantiostyly is restricted to only seven species and their populations consist of individuals producing either the right or the left flower type. It is hypothesized that the dimorphic form is derived from monomorphic ancestors because it functions as an outcrossing mechanism. We tested this latter hypothesis and investigated if monomorphic enantiostyly is resistant to invasion by individuals with dimorphic enantiostyly, because it functions as a reproductive assurance mechanism. To determine the conditions favouring the invasion of dimorphic enantiostyly, measurements of reproductive success and outcrossing rates in 15 natural flowering patches of Solanum rostratum were made. To test if monomorphic enantiostyly provides a reproductive assurance mechanism, experimental plants with either manually created dimorphic or natural monomorphic reproductive systems were exposed to two different pollination scenarios (flower density treatments), and reproductive success and outcrossing rates were measured. Naturally flowering patches experienced severe pollination limitation, showed marked differences in reproductive success and had relatively high outcrossing rates. Plants in the experimental patches also showed pollination limitation and high outcrossing rates. Individuals with dimorphic enantiostyly expressed higher reproductive and outcrossing advantages under high-density conditions. These advantages disappeared in the low-density treatment, where the monomorphic form attained a higher reproductive success and no differences in outcrossing rates were detected. Monomorphic enantiostyly should be resistant to invasion of the dimorphic form because the prevalent ecological conditions favour the maintenance of geitonogamous individuals that are able to take advantage of ecological heterogeneity and generalized pollination limitation.

Mating consequences of contrasting hermaphroditic plant sexual systems.

For hermaphroditic angiosperms with multiple flowers, the sex roles can be exclusively combined in bisexual flowers (monocliny), strictly separated among different flowers (monoecy), or arrayed in mixtures of bisexual flowers with female flowers (gynomonoecy) or male flowers (andromonoecy). The hypothesized benefits favoring the evolution of these contrasting hermaphroditic sexual systems are typically examined individually, usually by assessing success through only one sex role. We tested predictions of most hypotheses experimentally with an andromonoecious species, Anticlea occidentalis (Melanthiaceae), based on the performance of intact plants (andromonoecy) and those with emasculated bisexual flowers (functionally monoecious) or emasculated male flowers (functionally monoclinous with sterile peripheral flowers). Andromonoecy in this species enables efficient, size-dependent resource allocation, emphasizing female function in large plants. Emasculation revealed that anthers in male flowers promote female mating quality (outcrossing rate and mate diversity), whereas anthers in bisexual flowers promote male mating quantity (pollen dispersal distance and probability of any siring success). Thus, different hermaphroditic sexual systems likely evolve to capitalize on suites of benefits, rather than just one, and provide compromises between quantitative and qualitative reproductive components. These compromises apparently maximize an individual's combined genetic contributions through female and male functions, rather than separate contributions through each sex role.

Short-distance pollen dispersal in a protogynous Annonaceae tree species from the Brazilian Cerrado

Annona crassiflora (Annonaceae) is a protogynous beetle-pollinated savannah tree species, widely distributed in the savannahs of the Cerrado biome. Studies on the mating system and pollen dispersal of protogynous species are very scarce. Here, we used six microsatellite loci to assess the mating system and pollen dispersal of A. crassiflora in a savannah remnant in Central Brazil. We mapped and sampled leaves of 112 adult trees and collected 74 fruits from 20 mother trees (1–4 fruits per plant) to obtain the seeds used (460) for mating system and parentage analyses. Annona crassiflora has predominantly allogamous mating systems, with a high multilocus outcrossing rate (tm = 0.974, SE = 0.011) that did not differ among mother trees (F = 1.32, p = 0.165). However, tm–ts was variable among seed trees, indicating that some seeds were produced by mating among relatives. Our results also showed multiple paternity within fruits. Multilocus correlation of outcrossed paternity was high (rp = 0.302, SE = 0.045), indicating that for each mother tree, the probability that the same pollen donor sired two random sibs was 30.2%, and the mean number of pollen donors per mother tree was high (6.3). We detected a maximum pollen dispersal distance of 360.7 m and an average of 124.3 m (SD = 80 m), but most pollination events (73%) occurred at shorter distances (< 160 m), indicating short-distance pollen dispersal, most likely due to the pollinator behaviour.

A time-dependent uncertainty design and optimization strategy using an enhanced Kriging surrogate model

Uncertainties exist widely in the time-dependent performance degeneration processes of engineering systems in practice. Generally, in order to simplify the calculation, the random processes of uncertainty information are usually treated as time-independent or monotonic processes. The corresponding uncertainty analysis approaches are time independent. However, in this situation, the failure probabilities of performance can only be considered at the end of structure lifetime. To deal with the above challenge, an enhanced outcrossing rate method using the Kriging interpolation method is proposed in this study. The proposed method can utilize the correlation information between two design variables to predict the stress level and describe the time-dependent degeneration process. An uncertainty-based design and optimization problem of machine tool spindle is utilized to illustrate the effectiveness of the proposed strategy.

Sequential decline in fruit resource allocation within inflorescences of Sagittaria trifolia: a test of non‐uniform pollination hypothesis

AbstractFlowering plants often exhibit declining resource investment to floral organs, fruits and seeds temporally or spatially in an inflorescence. To account for such variances, non‐uniform pollination hypothesis, which highlights various mating environments each flower experiences, provides adaptive significance for allocation patterns but with controversial supports. Sagittaria trifolia (Alismataceae) was used to examine differences in seed number, seed weight and germination rate among sequential fruits within inflorescences. Ovule number was also investigated to evaluate allocation patterns in the floral stage. To test the non‐uniform pollination hypothesis, we used three polymorphic microsatellite loci of S. trifolia to estimate the seed outcrossing rate in proximal and distal fruits. The results showed that the seed number, average seed weight and seed germination rate of S. trifolia gradually decreased from proximal to distal fruits within inflorescences. The percent of decrease in seed number between two contiguous fruits was 14.68 ± 3.22%, which was much stronger than the percent of decrease in ovule number at 6.95 ± 1.60%. Both proximal and distal fruits within inflorescences had high outcrossing rates (81.5 ± 5.0%, proximal; 82.3 ± 6.9%, distal) and they did not differ significantly. Overall, there was an acropetal decline of resource allocation to fruits within inflorescences of S. trifolia. Allocation pattern to ovules was not a limiting factor for seed production. The lack of difference in outcrossing rate between proximal and distal fruits indicated that the allocation strategy was probably not caused by non‐uniform pollination, but more likely position effects.

Long-distance pollen and seed dispersal and inbreeding depression in Hymenaea stigonocarpa (Fabaceae: Caesalpinioideae) in the Brazilian savannah.

Hymenaea stigonocarpa is a neotropical tree that is economically important due to its high‐quality wood; however, because it has been exploited extensively, it is currently considered threatened. Microsatellite loci were used to investigate the pollen and seed dispersal, mating patterns, spatial genetic structure (SGS), genetic diversity, and inbreeding depression in H. stigonocarpa adults, juveniles, and open‐pollinated seeds, which were sampled from isolated trees in a pasture and trees within a forest fragment in the Brazilian savannah. We found that the species presented a mixed mating system, with population and individual variations in the outcrossing rate (0.53–1.0). The studied populations were not genetically isolated due to pollen and seed flow between the studied populations and between the populations and individuals located outside of the study area. Pollen and seed dispersal occurred over long distances (>8 km); however, the dispersal patterns were isolated by distance, with a high frequency of mating occurring between near‐neighbor trees and seeds dispersed near the parent trees. The correlated mating for individual seed trees was higher within than among fruits, indicating that fruits present a high proportion of full‐sibs. Genetic diversity and SGS were similar among the populations, but offspring showed evidence of inbreeding, mainly originating from mating among related trees, which suggests inbreeding depression between the seed and adult stages. Selfing resulted in a higher inbreeding depression than mating among relatives, as assessed through survival and height. As the populations are not genetically isolated, both are important targets for in situ conservation to maintain their genetic diversity; for ex situ conservation, seeds can be collected from at least 78 trees in both populations separated by at least 250 m.

Effects of wildfire on floral display size and pollinator community reduce outcrossing rate in a plant with a mixed mating system.

Wildfire changes the demography, morphology, and behavior of plants, and may alter the pollinator community. Such trait changes may drastically alter the outcome of pollination mutualisms on plants; however, the direct role of fire on these mutualisms is poorly known. Following a pair of fires in the northern California coast range chaparral, we censused floral visitor communities of Trichostema laxum (Lamiaceae), quantified visiting bee behavior, and estimated outcrossing rates using a widespread Mendelian recessive floral polymorphism across a matrix of populations in burned and unburned sites. We also compared pre- and postfire floral visitation in two populations. Outcrossing rates were significantly lower in burned areas; however, our data suggest that the much larger size of plants in burned areas, not burn status itself, drove this pattern. Large-bodied bees dominated floral visitor communities after fire, likely recruiting to the abundant postfire floral resources. These bees visited more flowers per plant than did the smaller bees prevalent before fire and in unburned areas, likely increasing selfing through geitonogamy (within-plant pollination), an effect made possible by the far larger size of plants in burned areas. Outcrossing rates dropped substantially after wildfires because of changes in the pollinators, plant display size, and their interactions. Reductions in outcrossing following fire may have important implications for population resilience and evolution in a changing climate with more frequent fires.

Investigation of the Breeding Mechanism of African Yam Bean [Fabaceae] (Sphenostylis stenocarpa Hochst. Ex. A. Rich) Harms

The many reported inherent nutritional potential in African yam bean (Sphenostylis stenocarpa (Hochst. Ex. A. Rich.) Harms) seem to provide platform for the need of its genetic improvement. A good understanding of the breeding system of the crop species is a needed criterion in plant breeding program. Four accessions of African yam bean (AYB) collected from the Genetic Resources Centre of the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria were grown out in a fifteen plants/accession row on a field at IITA, Ibadan (7.5°N, 3.9°E), Nigeria. Five pollination mechanisms were investigated as treatments on the four accessions. The four accessions set fruits and seeds in four treatments: plants left to open-pollination (A), plants isolated with fine net mesh (B), artificially selfed flowers (C) and inter-varietal cross-pollination (D). Emasculated flowers which were not pollinated (treatment E) produced neither fruit nor seed. Treatment A differed significantly (P&lt;0.05) from B, likewise C and D. Fruit set percentage was higher in A (19.7-21.2) than B (18.3–18.7). Higher pollination/fertilization success (46.5%) was obtained in C compared to 32.3% in D. More seeds (88.6%) were set by self-pollination. The four accessions had a mean selfing rate of 89.8% and an outcrossing rate of 10.17%. The observed 1:9 allogamy: autogamy in this study could form the basis for developing the breeding strategy for the genetic improvement of AYB via hybridization.

A risk‐based life cycle cost strategy for optimal design and evaluation of control methods for nonlinear structures

SummaryThe lack of direct correspondence between control objectives and hazard risks over the lifetime of systems is a key shortcoming of current control techniques. This along with the inability to objectively analyze the benefits and costs of control solutions compared with conventional methods has hindered widespread application of control systems in seismic regions. To address these gaps, this paper offers 2 new contributions. First, it introduces risk‐based life cycle–cost (LCC) optimal control algorithms, where LCC is incorporated as the performance objective in the control design. Two strategies called risk‐based linear quadratic regulator and unconstrained risk‐based regulator are subsequently proposed. The considered costs include the initial cost of the structure and control system, LCC of maintenance, and probabilistically derived estimates of seismic‐induced repair costs and losses associated with downtime, injuries, and casualties throughout the life of the structure. This risk‐based framework accounts for uncertainties in both system properties and hazard excitations and uses outcrossing rate theory to estimate fragilities for various damage states. The second contribution of this work is a risk‐based probabilistic framework for LCC analysis of existing and proposed control strategies. The proposed control designs are applied to the nonlinear model of a 4‐story building subjected to seismic excitations. Results show that these control methods reduce the LCC of the structure significantly compared with the status quo option (benefits of up to $1 351 000). The advancements offered in this paper enhance the cost‐effectiveness of control systems and objectively showcase their benefits for risk‐informed decision making.

Mating system and progeny genetic diversity of Camellia oleifera ‘Ruan Zhi’

Camellia oleifera Abel. is an important economic tree species of southern China. In this study, we evaluated the mating system and genetic diversity of a series of cultivars of C. oleifera ‘Ruan Zhi’. A total of 159 individuals from the progenies of four cultivars were tested by simple sequence repeat molecular markers. Results reveal that 11 pairs of primers showed polymorphism and their polymorphism information content value was greater than 0.73, suggesting that these primers could be used to identify the genetic diversity of open-pollinated populations. The average number of effective alleles (Ne = 4.88) was significantly different from the average number of alleles (Na = 12.18), and their distribution in the sample population was not uniform. The average observed heterozygosity (Ho = 0.96) was greater than the average expected heterozygosity (He = 0.79), and the population heterozygote was excessive. Shannon index was 1.84 and populations showed high genetic diversity. As regards to the mating system, the multilocus outcrossing rate was 0.996, and the single locus 0.866. These results indicate a high degree of outcrossing by C. oleifera ‘Ruan Zhi’. We recommend selecting individuals for high genetic gain from the progenies of cultivars because of outcrossing characteristics and genetic diversity for application to germplasm conservation and promotion.

Equipped for Migrations Across High Latitude Regions? Reduced Spur Length and Outcrossing Rate in a Biennial Halenia elliptica (Gentianaceae) With Mixed Mating System Along a Latitude Gradient.

Halenia (Gentianaceae) originated from the mountain regions of East Asia, and diversified in America following long migrations via Beringia. While Halenia elliptica, one species of the genus in China, migrated toward high latitudes in China. Spur length of H. elliptica is highly variable. We examined the relationship between spur length and mating pattern along a latitude gradient. Field experiments were performed in two populations of H. elliptica, and we found that this species could produce seeds via both autonomous selfing and the aid of pollinators, suggesting a mixed mating system. In seven populations of H. elliptica along a latitudinal gradient, we found a trend of decrease in spur length with the increase of latitude. Based on molecular data from 11 microsatellite loci, we found that multilocus outcrossing rate decreased with the increase of latitude while the estimated inbreeding depression increased significantly, indicating that a high degree of inbreeding depression might have prevented evolution toward complete selfing in the high latitude populations with short spur length, and thus maintained mixed mating system of H. elliptica. Our results suggest that the mixed mating system of this species might be helpful in overcoming pollinator scarcity in newly colonized populations toward high latitudes after its origination in the mountain regions of China, and the decrease of spur length in the high latitude populations could result from reduced resource allocation to pollinator associated traits.

Spontaneous outcrossing in tomato depends on cultivar and environment and varies between individual flowers

AbstractKnowledge about the degree of spontaneous outcrossing of diverse genotypes is essential for breeding programmes, maintenance breeding, and seed production. For tomato (Lycopersicon esculentum Mill.), very limited scientific evidence for genotypic differences is available and evidence from Europe is scarce. To close this knowledge gap, six cultivars were investigated in three Central European locations as part of the Organic Outdoor Tomato Project. To determine outcrossing rates, the monogenetic “cut‐leaf” trait, which is dominant over the “potato‐leaf” trait, was used as morphological marker. The observed range of outcrossing was 0.0%–5.2%. Outcrossing was significantly influenced by cultivar and environment. The outcrossing rate of individual flowers varied within cultivars ranging from 0% to 37%. The potential of newly opened flowers to accept foreign pollen varied largely with the cultivar. Genotypic differences could partly be linked to flower morphology traits. The potential for recombination between tomato genotypes is generally very low but can be a source for new variation in on‐farm management.