Search Results (41)

N. cadamba is a fast-growing and economically important tree species with significant industrial and medicinal values. Its spherical capitulum comprises hundreds of sessile florets densely aggregated on a receptacle. How this unique floral structure shapes the mating system of this species remains unknown, as this structure enhances the probabilities of both selfing and outcrossing. Here we clarify this question by investigating a natural population. We randomly sampled 11 half-sib families and 6 progenies per half-sib family and assayed samples with whole-genome resequencing. Population genomic analysis indicated that about 93.09% of 4,876,674 high-quality SNPs were under Hardy–Weinberg equilibrium, with a mean inbreeding coefficient of 0.0614 in the sample. Genome-wide nucleotide diversity (π) was 0.0024 on average. The linkage disequilibria ($r$²) decayed by half at approximately 2.31 kb between sites across genomes. Principal component analysis showed clear family structure among all samples. Analysis with independent SNPs and MLTR (Program for estimating multilocus outcrossing rate) showed that the multilocus outcrossing rate (t_m) and single-locus outcrossing rate (t_s) were 1.028 ± 0.048 and 1.015 ± 0.060, respectively, with an estimated difference between t_m and t_s of 0.013 ± 0.022. Analysis with BORICE (Bayesian outcrossing rate and inbreeding coefficient estimation) showed an outcrossing rate (t) of 0.948 ± 0.029 and an inbreeding coefficient (F) of 0.012 ± 0.010. Collectively, these results imply that N. cadamba could be essentially outcrossing, without selfing and biparental inbreeding. The potentially outcrossing system of N. cadamba implies differences from its close relative N. macrophylla (a mixed-mating system) in population structure, genome evolution, and natural geographical distribution. This finding also provided a useful reference for breeding and genetic improvement of this “miracle tree”. Full article

Flag leaf angle (FLA) in rice (Oryza sativa L.) is one of the important traits affecting F₁ seed production by mechanization. Here, we report the map-based cloning and functional characterization of the FLA1 (FLAG-LEAF-ANGLE 1) gene, which resides at a major-effect quantitative trait locus (QTL). Through cell morphological observations and exogenous hormone treatment assays, we demonstrate that gibberellin (GA) modulates rice FLA by altering both the number of cell layers and cell length. Combining genetic and molecular biological analyses with genetic complementation and gene overexpression assays, we elucidated and validated the biological function of FLA1. In addition, we found that FLA1 is constitutively expressed and encodes a protein localized to both the cell membrane and nucleus. Via RT-qPCR assays, we further demonstrated that the FLA1^fla-R allele from the rice accession fla-R enhances GA biosynthesis by upregulating the expression of CLA1 and GA20ox2. Furthermore, yeast two-hybrid assays revealed that auxin-repressed protein 1 (ARP1) interacts with FLA1, suggesting a potential role of this interaction in the modulation of rice FLA. Collectively, our results demonstrate that optimizing rice FLA via molecular manipulation of FLA1 can resolve the problem of flag leaf shearing during F₁ hybrid rice seed production without compromising F₁ hybrid seed yield, thereby facilitating mechanized F₁ hybrid rice seed production. Full article

Sonneratia ovata is an important tree species for ornamental, economic, ecological, and medicinal value and is identified as an endangered species. There are very few studies on the reproductive traits, genetic diversity, and population structure of S. ovata. Therefore, it is urgent to accurately understand its genetic background and reproductive status in order to better conserve and manage S. ovata. S. ovata has a mixed mating system, is partially self-compatible and needs pollinators, according to the outcrossing index, pollen–ovule ratio, pollination treatment results and outcrossing rate. Natural populations maintained high outcrossing coupled with inbreeding and low genetic diversity (H_e = 0.215), and the population DC was regarded as the center of genetic diversity. The Mantel test showed that there existed a positive correlation between geographic and genetic distance among populations, which was in line with the IBD model. Molecular variance was largely confined to within-population differences (75.4%), while inter-population differences accounted for 24.6%. Structure and PCoA analysis supported the UPGMA cluster. This study is the first to investigate reproductive traits, genetic diversity, and population structure through SSR. The results provide a scientific basis for cross breeding, conservation, and management of this species. In future, it is necessary to increase relevant research (human, environment, habitat factors, etc.) to better protect and utilize this species. Full article

The aim of this study was to elucidate the reproductive strategy of Camellia luteoflora, an endangered evergreen endemic to karst ecosystems. We observed and recorded its flowering phenology and flower-visiting insects, observed pollen morphology, determined pollen viability, and assessed stigma receptivity. The results showed that the flowering period of C. luteoflora started from early September to late December, with the average flowering period of individual flowers being 10–12 days. The pollen morphology of C. luteoflora was subprolate and prolate, with three germinal apertures and the fossulate exine ornamentation. Pollen viability was the highest at the initial opening stage (80.30%). In the process of pollen in vitro, the order of influence on the germination rate and pollen tube length was temperature > sucrose > calcium chloride (CaCl₂) > boric acid (H₃BO₃). The best combination for the germination rate was 24 °C, 75 g/L sucrose, 0.2 g/L CaCl₂, 0.15 g/L H₃BO₃, while that for the pollen tube length was 24 °C, 100 g/L sucrose, 0.2 g/L CaCl₂, 0.25 g/L H₃BO₃. Stigma receptivity was the strongest at the full blooming stage. The pollen/ovule ratio (P/O) was 2240, suggesting a facultative outcrossing breeding system. The outcrossing index (OCI) was 4, suggesting that the exogamous breeding system is the cross-pollination type, partially self-compatible and insect pollinator-dependent. The flower-visiting insects included bees, weevils, and ants. In summary, C. luteoflora exhibits an extended flowering period, with a prolonged overlap of stable pollen viability and stigma receptivity, suggesting a potential strategy to cope with pollination uncertainty. However, field observations recorded only a few species of potential pollinators, while the occurrence frequency of non-pollinating insects was relatively high. It is thus hypothesized that this apparent lack of effective pollinators may act as a potential barrier to successful fertilization and natural regeneration, which might also be one of the factors contributing to its endangered status. Future studies, particularly pollinator exclusion and hand-pollination experiments, are critically needed to verify whether pollinator limitation is indeed a key factor. Full article

Nectar robbing typically reduces nectar availability to pollinators, damages flower structure, and/or induces secondary robbing. Consequently, it may reduce pollen deposition and seed set, increase pollination efficiency and outcrossing, and/or not affect reproduction in some species. However, spatiotemporal variations in nectar robbing and their effects on plant reproduction have received little attention. In this study, we assessed the effects of nectar robbing on floral visits, seed set, nectar volume and concentration, and flower longevity in two populations of Salvia castanea Diels (Lamiaceae) in the Himalayan region of Southwestern China in 2014–2020. We also examined whether one or a few visits by pollinators can result in the stigma receiving sufficient pollen to fertilize all ovules of S. castanea. We found that significant differences in the nectar robbing rate did not affect seed set in any of the years for either population of S. castanea. In the robbed and unrobbed flowers, nectar was consistently replenished every night at higher concentrations. Bagging, nectar robbing, and sufficient pollination did not affect flower longevity. Salvia castanea required only 5–10 pollen grains to achieve the maximum seed set. However, pollinators depositing more than 10 pollen grains after a single visit ensured a high seed set of >80%. Our results suggest that nectar availability, floral longevity maintenance, and sufficient pollen deposition mitigate the effects of nectar robbing on the reproductive success of S. castanea. These results are expected to further our understanding of plant–animal interactions and the ecological consequences of nectar robbing. Full article

The gene flow rate in rice (Oryza sativa L.) is a critical factor for establishing safe isolation distances between genetically modified (GM) and non-GM varieties and for ensuring varietal purity in rice breeding programs. This study refines existing gene flow models by disentangling two key components of rice pollen dynamics: quantitative pollen competition and genetic competitiveness. We define B as the proportion of GM pollen within mixed pollen, representing quantitative pollen competitiveness. The outcrossing parameter C_b reflects the likelihood of successful fertilization and seed development by foreign pollen, while the hybrid compatibility parameter C_p captures the relative fertilization success of GM versus non-GM pollen within the same pollen pool. Together, C_b and C_p characterize the genetic competitiveness of rice pollen. Our findings reveal a nonlinear relationship between B and the observed GM pollen rate G, which may exhibit either upward or downward curvature. A nonlinear model provides a significantly better fit to this relationship than a linear model, improving R² by 4.1–21.4% and reducing RMSE by 9.9–47.8%. The parameters C_b and C_p play central roles in determining gene flow; higher values correspond to stronger GM pollen competitiveness, resulting in higher gene flow rates and greater dispersal distances. Specifically, C_b sets the range of the B–G curve, while C_p determines its curvature. Full article

In desert plants, outcrossing is frequently limited by pollinator scarcity, leading to a certain percentage of self-fertilization. However, research on the ecological adaptations of self-fertilized seeds remains limited. Gymnocarpos przewalskii Maxim, a Tertiary relict plant in the arid deserts of Northwest China, exhibits pronounced self-pollination. In this study, the population of G. przewalskii from the fifth regiment of Alar City was selected to explore its self-pollination types, self-pollination percentages, and ecological adaptations. We found that artificially cross-pollinated G. przewalskii produced heavier seeds, faster germination, seedlings with greater biomass, and stronger environmental adaptability than self-pollination. However, the frequency of insect visits per flower was less than one. The fruit setting rate of natural pollination was 6.90%, while that of self-pollination was 4.43%, accounting for 64.20% of the natural fruit setting rate. Additionally, G. pzewalskii’s filaments elongated rapidly to make the anthers and stigma at the same height before flowering. These characteristics suggest that G. przewalskii is capable of autonomous self-pollination and is prior selfing. Gymnocarpos przewalskii likely produces a high proportion of the selfing merely to ensure population survival. These findings offer valuable insights into the adaptation of desert plants to the scarcity of pollinators. Full article

Tamarix chinensis Lour. is a halophytic shrub native to coastal China, commonly used in afforestation and ecological restoration due to its high tolerance to salinity and drought. To understand how this species maintains genetic variation and adapts to extreme environments, we examined the genetic diversity, mating system, and spatial genetic structure of a natural T. chinensis population on the geographically isolated and environmentally harsh Wudi Seashell Island. Using both SSR and ISSR markers, we observed high levels of genetic diversity despite the small population size and spatial fragmentation. SSR markers revealed an average of 11.75 alleles per locus, with an expected heterozygosity (He) of 0.754 and an observed heterozygosity (Ho) of 0.702. ISSR markers showed a polymorphic locus rate of 97.87%, with a mean He of 0.402. Parentage analysis revealed relatively long seed and pollen dispersal distances, with most dispersal occurring within 150 m and seeds and pollens occasionally reaching 948 m and 447 m, respectively. The species exhibited a mixed mating system, with a multilocus outcrossing rate of 0.554, contributing to gene flow and reducing inbreeding. A fine-scale spatial genetic structure was detected within 75 m, consistent across both SSR and ISSR markers, suggesting limited local gene dispersal. These findings provide new insights into the adaptive strategies of T. chinensis in marginal habitats and offer valuable guidance for conservation and restoration efforts in vulnerable coastal ecosystems. Full article

Many rapidly expanding food crops, including avocado (Persea americana Mill.), are dependent on animal pollination but there is a growing shortfall in global pollinator supply. Avocado flowers are insect-pollinated and yields of the main cultivar, ‘Hass’, are often pollen-limited, especially in the middle of single-cultivar orchard blocks, where there is limited deposition of cross-pollen from another cultivar. We analysed two avocado cultivars of alternate flowering types, ‘Maluma’ (Type A) and ‘Shepard’ (Type B), using SNP-based DNA markers to identify the pollen parent of fruit at different distances from the other cultivar. We aimed to determine whether the numbers of cross-fertilised fruit and tree yields decline at increasing distances from a cross-pollen source, and whether cross-fertilised fruit are larger than self-fertilised fruit. We found that the number of cross-fertilised fruit produced by each tree declined in the middle of the blocks of each cultivar. Trees in the middle of the ‘Maluma’ block compensated for low levels of cross-pollination by producing more self-fertilised fruit, and their yields did not appear to be pollen-limited. However, yields in the middle of the ‘Shepard’ block declined by 25% as a direct result of a 43% reduction in the number of cross-fertilised fruit produced by each tree. ‘Shepard’ trees did not compensate for poor cross-pollination by producing more self-fertilised fruit. Cross-fertilisation of ‘Maluma’ by ‘Shepard’ increased fruit mass by 8% and cross-fertilisation of ‘Shepard’ by ‘Hass’ increased fruit mass by 5%, compared with self-fertilisation. Our results confirm that yields of avocado trees are sometimes, but not always, pollen-limited. Low levels of both self-pollination and cross-pollination resulted in pollen limitation of yield in the middle of the ‘Shepard’ block, but high levels of self-pollination were sufficient to generate high yields in the middle of the ‘Maluma’ block. Closer interplanting of Type A and Type B avocado cultivars increases the opportunities for cross-pollination, which can often increase tree yield and fruit size, and improve the financial returns for growers. Improving the pollination efficiency of foraging insects by providing them with the optimal pollen genotypes is increasingly important as we experience a growing demand for managed pollinators and a declining abundance of wild pollinators. Full article

Faba bean (Vicia faba L.) is a globally significant legume valued for its applications in food, vegetables, and green manure, yet its high outcrossing rate (30–80%) poses challenges for production development. A rare short-winged trait identified in Yunnan, China, offers promise for developing low-outcrossing varieties, reducing outcrossing rates to below 5%. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses revealed that the epidermal cells of normal wing petals are conical, while those of short-wing petals are tubular. This study examined 200 F₂ lines from crosses between ‘K0692’ (short-winged) and ‘Yundou 1183’, as well as ‘Yundoulvxin 1’ (short-winged) and ‘Yundou 1183’. The GWASs identified 10 SNP loci across chromosomes 2, 3, 4, and 5, with SNP_chr4::1013887633 explaining 22.20% of the wing trait variation. Key candidate genes were identified, such as VFH_III145120, which influences floral identity; and VFH_III149200, associated with epidermal differentiation. GO enrichment analysis demonstrated significant gene involvement in RNA localization, ribosome biogenesis, and preribosome metabolism, while KEGG analysis linked these genes to pathways in amino acid, nucleotide, and purine metabolism; ubiquitin-mediated proteolysis; and protein processing in the endoplasmic reticulum. These findings lay a foundation for breeding low-outcrossing faba bean varieties and enhancing sustainable faba bean cultivation. Full article

The research aimed to investigate the reproductive biology of M. Savatieri (Monochasma savatieri Franch. ex Maxim.), focusing on its floral structure, developmental stages, flowering dynamics, pollen dispersal characteristics, stigma development, and longevity, as well as self-crossing affinity in both indoor and outdoor cultivation conditions. The study divided the flower development process into four distinct stages: the bud stage (1–3 days), the present bud stage (4–8 days), the pollination stage (9–14 days), and the fruiting stage (15–35 days). Pollen dispersal begins one hour after flowering during the pollination stage and ends within five hours under both indoor and outdoor sunny conditions. Pollen remains highly viable for up to 60 days. Stigma receptivity reaches its maximum at 94.44% on the first day of flowering, decreases to 68.2% by the fourth day, and further declines to 16.7% on the fifth day. The plant, with an outcrossing index (OCI) of 3, shows a 28.80% outcrossing rate in indoor environments and 9.57% in outdoor conditions. It primarily relies on heterogamous pollination while being capable of both self-pollination and artificial pollination. The results provide significant insights into the breeding and production of M. savatieri. Full article

The adoption of grain amaranth (Amaranthus hypochondriacus L.) as a climate-smart crop due to its hardiness and drought escape mechanisms in sub-Saharan Africa is under threat from the lack of pure seed due to contamination by weedy relatives, such as pigweed (A. hybridus L.). Due to limited land availability, proper isolation distances to attain seed purity in the small-scale farming sector are impossible. A study investigating the cross-pollination rate between grain amaranth and pigweed at distances between 3 and 150 m was conducted at three sites in Zimbabwe during the 2020/2021 and 2021/2022 rainy seasons. Grain amaranth was planted at radial distances of 3 to 150 m from the pure pigweed plot. Meteorological conditions, such as temperature and wind speed and direction, were measured during the anthesis period. The cross-pollination rate in grain amaranth was influenced by distance from the pollen source. A maximum cross-pollination rate of 12.9% was observed within a 10 m radius from the pollen donor plot, and a minimum outcrossing rate of 0.45% was recorded at 150 m. The complete removal of weedy relatives within an extrapolated distance of 325 m is recommended to maintain the genetic purity of grain amaranth in small-scale farming systems. Full article

As global food demand continues to grow, enhancing rice seed-setting rate and yield has emerged as a crucial research topic. The stigma exsertion rate in rice, a pivotal determinant of the outcrossing seed-setting rate in sterility lines, is essential for facilitating the propagation and efficient seed production of hybrid rice varieties. This article reviews the research progress on stigma exertion rate in rice, systematically analyzing the latest molecular biology and genetics findings to uncover the key genes and molecular mechanisms regulating stigma exertion. Furthermore, it explores the application of molecular marker-assisted selection technology in rice breeding, aiming to optimize stigma exertion traits to enhance the stigma exertion rate and outcrossing habits of rice sterility lines. By integrating existing research outcomes, this article not only provides researchers with a theoretical foundation for a deeper understanding of the regulatory mechanisms of stigma exertion but also offers practical strategies for rice breeding practices. Full article

Wheat hybrids have been widely demonstrated to have remarkable heterosis or hybrid vigor in increasing yield potential and stability since the 1960s. Two-line hybrid wheat can achieve higher yields than local varieties, especially in marginal environments. However, the commercial application of hybrid wheat is hindered by higher seed costs, primarily due to lower yields in hybrid seed production. Stigma exsertion has been verified as a decisive factor in increasing rice’s hybrid seed yield, but more investigation is needed in hybrid wheat breeding and production. In this study, four thermo-photo-sensitive genic male sterile lines, including K41S, K64S, K66S, and K68S, with different stigma exsertion rates (SERs) were used to compare the differences in floral architecture relative to stigma exsertion over two growing seasons. The results revealed that the K41S and K64S exhibited a relatively higher SER at 21.87% and 22.81%, respectively. No exserted stigma was observed in K66S, and K68S had an SER of only 0.82%. This study found that the stigma length, glume width and the length–width ratio of the glume were significantly correlated with the SER, with correlation coefficients of 0.46, −0.46 and 0.60, respectively. Other stigma features such as the branch angle, stretch width and hairbrush length, as well as the glume length, also had a weakly positive correlation with SER (r = 0.09–0.27). For K41S and K64S, the SER was significantly affected by the differences in the stigma branch angle and stigma stretch width among florets. A cross-pollination survey showed that the out-crossing ability of florets with an exserted stigma was about three times as high as that of florets with a non-exserted stigma. As a result, the stigma-exserted florets that accounted for 21.87% and 22.81% of the total florets in K41S and K64S produced 46.80% and 48.53% of the total cross-pollinated seeds in both sterile lines. These findings suggest that a longer stigma combined with a slender glume appears to be the essential floral feature of stigma exsertion in sterile wheat lines. It is expected that breeding and utilizing sterile lines with a higher SER would be a promising solution to cost-effective hybrid wheat seed production. Full article

Revealing the relationship between the mating system (i.e., the outcrossing/inbreeding degree) and the fitness of seeds in tree species under wild conditions is essential for understanding the ecological adaptability and evolutionary stability of the species. This study collected open-pollinated seeds from seven wild populations of Pinus yunnanensis var. tenuifolia that exhibited fragmentation in the Nanpan–Hongshui River basin, an ecologically fragile area in China. The seeds and sprouts (germinated seeds) from 20 families were genotyped (24 seeds and 24 sprouts per family) using twelve microsatellite loci to reveal the genetic diversity, mating status, and effect of inbreeding on the three seed quality indicators (thousand-seed weight, germination rate, and germination potential). The three seed quality indicators differed significantly between families (p < 0.001). Higher values of genetic diversity (except the observed heterozygosity) were observed in the sprout group than those in the seed group. Families from different populations showed a notable genetic differentiation (Φst = 0.12), and a large part of families from the common populations had a high degree of coancestry, which signified that the current habitat fragmentation is limiting gene flow between populations. High levels of outcrossing rates (tm) were observed in both the seed group (t_m = 0.974) and the sprout group (t_m = 0.978), indicating that a low proportion of seeds were self-fertilized. Although there was a slightly higher single outcrossing rate (t_s = 0.888) and a lower proportion of biparental inbreeding (t_m − t_s = 0.077) in sprouts compared to the seeds (t_s = 0.871, t_m − t_s = 0.091), indicating that a part of inbred seeds were purged during the germination stage, curve fitting between the outcrossing rate and seed quality indicators showed that a certain degree of biparental inbreeding (t_s between 0.89 and 0.91 and t_m − t_s between 0.09 and 0.11) did have a positive effect on seed germination ability. This highlights that excessive inbreeding or outbreeding seems to be unfavorable to seed viability. The peculiar relationship between seed viability and the mating system in P. yunnanensis var. tenuifolia was likely an evolutionary consequence of a trade-off between the nature of mixed mating and its specific ecological niche. Full article