Effect of different pollination schemes on the fruit morphometric characteristic of Vanilla planifolia Jacks.

Efeito de diferentes esquemas de polinização nas características morfométricas dos frutos de Vanilla planifolia Jacks.

Abstract

Vanilla planifolia Jacks. is an orchid of great economic interest, classified as endangered. The limited genetic variation of this species has been primarily attributed to its clonal propagation. Genetic improvement through pollination schemes allows for improving the characteristics of fruits, seeds, and seedlings, increasing resistance to biotic and abiotic stress. Therefore, it was proposed to develop the present work to evaluate the effect of three pollination schemes at different times on the morphometric characteristics of the fruit. 65 flowers in the anthesis phase were randomly selected and subjected to the following treatments: 1) natural pollination with emasculated flowers, 2) manual pollination by autogamy, and 3) geitonogamy, in a vanilla plantation located in Mesa de Guadalupe, Veracruz, Mexico. The percentage of set and retained fruits, growth dynamics (length and diameter), weight, and shape index of the fruits were evaluated for each pollination scheme and on different days after pollination (DAP). Fruit formation by natural pollination was not observed, which shows the absence of apomixis and fertilization by any pollinating agent in this vanilla plantation. No differences were observed in the set and retention of fruits obtained by autogamy, and geitonogamy. The growth dynamics show that the fruits reach their maximum length at 40 DAP for both pollination schemes. Greater length, shape index, and weight were observed in the fruits obtained by geitonogamy at 40 DAP. These results show that inbreeding has no apparent effects on capsule production in V. planifolia but does influence its morphometric characteristics.

Keywords:
autogamy; geitonogamy; mating system; Orchidaceae; self-pollination

Resumo

Vanilla planifolia Jacks. é uma orquídea de grande interesse econômico, classificada como ameaçada de extinção. A limitada variação genética desta espécie foi atribuída principalmente à sua propagação clonal. O melhoramento genético por meio de esquemas de polinização permite melhorar as características de frutos, sementes e mudas, aumentando a resistência ao estresse biótico e abiótico. Assim, foi proposto que o presente trabalho fosse desenvolvido para avaliar o efeito de três esquemas de polinização diferentes momentos nas características morfométricas do fruto. Foram selecionadas aleatoriamente 65 flores em fase de antese e submetidas aos seguintes tratamentos: 1) polinização natural com flores emasculadas, 2) polinização manual por autogamia, e 3) geitonogamia, em plantação de baunilha localizada em Mesa de Guadalupe, Veracruz, México. A percentagem de frutos fixados e retidos, a dinâmica de crescimento (comprimento e diâmetro), o peso e o índice de forma dos frutos foram avaliados para cada esquema de polinização e em diferentes dias após a polinização (DAP). Não foi observada a formação de frutos por polinização natural, o que mostra a ausência de apomixia e de fertilização por qualquer agente polinizador nesta plantação de baunilha. Não foram observadas diferenças no pegamento e na retenção dos frutos obtidos por autogamia e geitonogamia. A dinâmica de crescimento mostra que os frutos atingem seu comprimento máximo aos 40 DAP para ambos os esquemas de polinização. Maior comprimento, índice de forma e peso foram observados nos frutos obtidos por geitonogamia aos 40 DAP. Estes resultados mostram que a endogamia não tem efeitos aparentes na produção de cápsulas em V. planifolia, mas influencia as suas características morfométricas.

Palavras-chave:
autogamia; autopolinização; geitonogamia; Orchidaceae; sistema de acasalamento

Introduction

Vanilla (Vanilla planifolia Jacks.), a member of the Orchidaceae family, is cultivated to obtain vanilla extract from its fruits, which is characterized by its flavor and fragrance derived from vanillin (4-hydroxy-3-methoxybenzaldehyde) (Arya et al., 2021). This compound has significant international economic value and is widely used in the food, cosmetic, pharmaceutical, and perfumery industries (Herrera-Cabrera et al., 2022).

One of the main reasons for the high demand for V. planifolia is due to its fruits having the most complete aromatic profile compared to other commercially available species (Peña-Barrientos et al., 2023). However, the species faces challenges in its sexual propagation due to low rates of pollination and seed germination (Hernández-Apolinar et al., 2016). As a result, asexual propagation through cuttings has become the preferer method, leading to a decrease in genetic variability and increased susceptibility to biotic and abiotic factors (Bautista-Aguilar et al., 2021). These factors have contributed to the species being classified as endangered (EN) by the International Union for Conservation of Nature (IUCN) (Vega et al., 2017).

V. planifolia is a plant with hermaphrodite flowers and an allogamous reproduction system. Studies have been conducted on the pollination ecology of this species, and it has been reported that the bee Melipona beecheii Bennet is a pollinator (Dressler, 1981). However, there is currently no documented evidence of efficient pollination by Melipona bees for orchids (Lubinsky et al., 2006). It is worth noting that V. planifolia is rarely visited by any insect species, and recent research has shown that only Eulaema spp. and Euglossa spp. are involved in its pollination (Hernández-Apolinar et al., 2016).

Dressler (1981) has suggested that the excessive use of agrochemicals has led to a loss of interaction between these organisms and vanilla, resulting in a loss of its pollinator. Consequently, vanilla plantations rely on manual self-pollination to produce fruits. However, this method results in low percentages of in vitro germination (<10%) (Yeh et al., 2021). Inbreeding depression can lead to reduced seed quality, viability, and germination (Ross and Travers, 2015). The absence of endosperm in the seeds, along with their black, hard, and crusty testa, further inhibits germination (Yeh et al., 2021).

The genotypes of pollen have a significant impact on the development of the embryo and endosperm, as well as the physical characteristics of fruits (Saini et al., 2022). It is well-established that the origin of pollen affects fruit set rates, maturity, size, weight, shape, diameter, and composition (Deng et al., 2022), as well as the number of seeds produced (Hashemabadi et al., 2023).

Geitonogamy refers to the fertilization of ovules with pollen from a flower on the same plant or a genetically identical clone (Fattorini and Glover, 2020; Saini et al., 2022). This type of pollination results in greater genetic diversity compared to asexual reproduction (such as vegetative reproduction and apomixis) due to the potential for allele recombination during meiosis (Fattorini and Glover, 2020; Kundu and Karmakar, 2022). The effects of geitonogamy can have a significant impact on the size and shape of fruits, seed quality, germination capacity, and the expression of desirable traits (Saini et al., 2022).

Understanding how different pollination types affect fruit development and quality can greatly enhance production efficiency of V. planifolia. Likewise, studying reproductive strategies through various pollination schemes is crucial for developing genetic improvement programs. The objective of this study was to evaluate the effects of different pollination schemes (natural pollination, autogamy, and geitonogamy) on the morphometric characteristics of the fruits inV. planifolia.

Materials and methods

Study site

The study was conducted in a vanilla plantation located in “Mesa de Guadalupe”, Veracruz, Mexico. The coordinates of the site are 19.566607 latitude, 96.698592 longitude, and 841 meters above sea level. The plantation covers an area of 242 m² (11 x 22 m) and consists of 200 V. planifolia plants, spaced 1.5 m apart in rows and 0.5 m between plants. The crop was established under a 50% shade mesh, using mulatto sticks (Bursera simaruba L.) as stakes.

Pollination treatments

Three pollination schemes were carried out: 1) natural pollination, where the pollinia were manually removed from the flowers (emasculation); 2) autogamy, where the pollinia were placed on the stigma of the same flower; and 3) geitonogamy, where the pollinia were transferred to the stigma of another flower of a clone plant. For each treatment, 65 flowers in the anthesis phase were randomly selected from 30 plants (Fig. 1A). The pollination process was carried out manually (Fig. 1B), and the flowers in the autogamy and geitonogamy treatments were covered with tulle bags. Pollination took place in March during the early hours of the day (06:00 a.m.).

Fig. 1
Development of pollination schemes in V. planifolia. A) flowers in anthesis, B) manual pollination, C) unfertilized ovaries, and D) fruit formation at 40 Days After Pollination (DAP).

Evaluations

After 7 days after pollination (DAP), the percentage of fruits set by each pollination treatment was determined. Subsequently, at 35 DAP, the percentage of retained fruits was determined. The growth dynamics of the fruits in terms of length and diameter were evaluated on 55 fruits at 7, 21, 35, 40, and 45 DAP for each pollination scheme. The shape index (length/diameter) was determined using the data collected at 40 DAP. Additionally, eight fruits were randomly collected at 40 DAP for each pollination scheme and transferred to the laboratory to evaluate their weight.

Statistical analysis

A Chi-square test was performed to determine the differences between pollination schemes in the percentage of fruit set and retained fruit. Maximum fruit growth, length, and diameter were determined for each pollination scheme with a one-way analysis of variance (ANOVA) followed by a Duncan’s test (p ≤ 0.05). To compare fruit length, diameter, shape index, and weight variables between autogamy and geitonogamy at 40 DAP, Student t-tests were performed (p ≤ 0.05). These statistical analyses were performed with Statgraphics Centurion (version 19, for Windows), and SigmaPlot (version 12, for Windows) software.

Results

After 7 DAP, it was observed that the ovaries of the flowers from the natural pollination scheme did not increase in length or diameter (Fig. 1C). Subsequently, the tissue became necrotic, and at 21 DAP, it completely detached from the inflorescence. This indicates that neither an apomixis event nor fertilization by any pollinating agent occurred in this vanilla plantation. No significant differences were observed (X²= 0; G.L. = 1; p = 1) in the percentage of fruits set (Fig. 1D) by autogamy and geitonogamy. At 35 DAP, premature fruit drop was observed in both autogamy and geitonogamy crosses, but there were no statistically significant differences (X² = 1.878; G = 1; p = 0.1705) (Table 1).

Table 1
Relationship of the percentage of set fruits and retained fruits of V. planifolia under different pollination schemes.

Treatments	Set fruits (%)	Retained fruits (%)
Natural pollination	0	0
Autogamy	92.30 a	98.33 a
Geitonogamy	92.30 a	93.33 a

The Chi-square test was performed for all variables. Different letters represent statistically significant differences.

The growth dynamics, specifically the length of the fruits, showed a significant increase for both autogamy and geitonogamy to 40 DAP (Fig. 2), with average lengths of 16.40 and 17.38 cm, respectively (Fig. 3).

Fig. 2
Fruits obtained 40 days after pollination (DAP), A) geitonogamy and B) autogamy.

Fig. 3
Dynamics of growth in the fruit length of V. planifolia under different pollination schemes. Different letters represent statistically significant differences (Duncan, p ≤ 0.05). The data represents the mean values and the bars the standard error. Furthermore, it was observed that the fruit diameter increased over time, reaching an average of 1.06 cm and 1.04 cm for autogamy and geitonogamy, respectively, at 40 DAP (Fig. 4).

Fig. 4
Dynamics of fruit diameter growth in V. planifolia under different pollination schemes. Different letters represent statistically significant differences (Duncan, p ≤ 0.05). The data represents the mean values and the bars the standard error.

When comparing the length, diameter, shape index, and weight of the fruits obtained by autogamy and geitonogamy at 40 DAP using the student’s t-test, significant differences were found in the length, shape index, and weight, with higher values obtained by geitonogamy. For diameter, no significant differences were found (Fig. 5).

Fig. 5
Effects of autogamy and geitonogamy on fruit morphology. A) length, B) diameter, C) shape index (length/diameter), and D) weight of V. planifolia fruits collected at 40 Days After Pollination (DAP). A student’s t-test was performed, and significant differences (p > 0.05) were observed in length, shape index, and weight; no differences were found in the diameter of the fruits.

Discussion

V. planifolia, like many orchids, is a self-compatible species (Andriamihaja et al., 2020). However, pollination without the assistance of pollinators is challenging due to the presence of the rostellum, a floral structure that creates a physical barrier between the pollinia and the stigma, preventing their direct contact. As a result, both self-pollination and natural cross-pollination require a pollinating agent to transfer the pollinia to the stigma (Johnson and Edwards, 2000). In its native habitat, specific pollinators perform this important function. However, in areas where V. planifolia is commercially cultivated, far from its natural range, these native pollinators are often absent. This makes natural pollination impossible and necessitates human intervention to ensure the species’ reproduction (Pemberton et al., 2023).

In this study, no fruits were recorded as a result of natural pollination, which may indicate a decline in pollinator populations, as previously suggested by Dressler (1981). However, current scientific evidence does not definitively support this hypothesis (Lubinsky et al., 2006). Recent research has aimed to identify potential pollinators, with Pemberton et al. (2023) highlighting Euglossa dilemma, E. tridentata, and Apis mellifera as possible candidates. This finding opens new avenues for exploring the reproductive ecology of V. planifolia.

No fruit formation was observed without manual or natural pollination, indicating that reproduction through apomixis did not take place. This finding aligns with reports from other regions where vanilla is produced, where asexual reproduction has similarly not been documented (Pemberton et al., 2023). Apomixis has been proposed as an alternative reproductive strategy for species with high levels of polyploidization that are subjected to elevated stress conditions (Kaushal et al., 2018), such as V. planifolia (Borbolla-Pérez et al., 2017). However, the occurrence of this phenomenon is rare, which makes it challenging to evaluate (Reutemann et al., 2022).

In this study, there were no significant differences in the percentage of fruit set between autogamy and geitonogamy. Fruit set is influenced by various pollination factors, including the quantity, quality, and viability of pollen (Abbate et al., 2023), as well as the source of pollen and successful fertilization (Deng et al., 2022). Self-pollination can also result in poor fruit set due to gametophytic incompatibility (Deng et al., 2022); however, the Vanilla genus has been observed to have high self-compatibility (Andriamihaja et al., 2020). Generally, cross-pollination is known to increase fruit set (Deng et al., 2022). However, in several orchid species it has been reported that self-pollination by autogamy does not affect fruit set (Capó et al., 2022), results like those obtained in this work.

It has been noted that V. planifolia exhibits premature fruit abortion, with losses of up to 40% of the fruits (Borbolla-Pérez et al., 2017). In this study, we found that at 35 DAP, there were low percentages of premature fruit drop in both autogamy (1.67%) and geitonogamy (6.67%) pollination schemes. This phenomenon has been linked to various abiotic, biotic, metabolic, agronomic, and reproductive factors, including changes in temperature and low precipitation during fruit development (Borbolla-Pérez et al., 2017). Previous research has also suggested a correlation between low genetic diversity and premature fruit abortion in xenogamies plants like V. planifolia, as self-fertilization can result in the expression of deleterious recessive alleles during early seed development (Faast et al., 2011). However, our results do not support this hypothesis.

Yeh et al. (2021) reports that V. planifolia fruits typically reach their maximum length at 35 DAP. Additionally, our observations demonstrated that the fruits at 40 DAP reached their maximum length. However, while the diameter of the fruits can continue to increase up to 49 DAP (Yeh et al., 2021), our study found that the maximum diameter was reached at 40 DAP. Furthermore, significant differences were observed in the length (16.40 and 17.38 cm for autogamy and geitonogamy, respectively), shape index (15.38 and 16.62 for autogamy and geitonogamy, respectively), and weight (12.46 and 12.87 g for autogamy and geitonogamy, respectively) of the fruits obtained at 40 DAP in the different pollination schemes. These findings suggest that the source of pollen has an impact on fruit characteristics. Barreda-Castillo et al. (2023) discovered noteworthy variations in the length, diameter, weight, and shape index of V. planifolia fruits resulting from both self-pollination and inter- and intraspecific crosses with V. pompona, providing further evidence in support of this theory.

According to Abbate et al. (2023), there is a correlation between the production of smaller capsules and a decrease in the number of fertilized ovules and, therefore, in the number of seeds produced. In orchids, pollen aggregates to form two pollinia, with one pollinia often being enough to fertilize all the ovules in a flower (Johnson and Edwards, 2000). When pollinating vanilla, pollinia are transferred as a single unit, providing a consistent amount of pollen grains (Faast et al., 2011), so similar characteristics would be expected in all fruits. However, self-pollination and mating between closely related species have been found to increase the risk of inbreeding depression, which can lead to a reduction in seed number, viability, and germination capacity (Faast et al., 2011). In contrast, Travers et al. (2018) found that in the orchid Platanthera praeclara Sheviak & Bowles, autogamy (self-pollination) did not affect fruit size compared to allogamy (cross-pollination). However, they did observe that only 18% of the seeds obtained through autogamy were viable, compared to 92% viability in seeds obtained through cross-pollination. It is possible that other factors, such as resource availability and habitat environmental characteristics, may also play a role in seed production and viability (Faast et al., 2011). Further research is needed to fully understand this aspect.

On the other hand, mating systems have a significant impact on the levels of diversity and genetic structure of populations, which are important factors to consider in conservation efforts (Faast et al., 2011). Cross-pollination is the primary source of genetic variation in offspring, while self-pollination results in greater variation compared to asexual reproduction (such as vegetative reproduction and apomixis) due to the potential for recombination of alleles during meiosis (Fattorini and Glover, 2020). However, self-pollination still results in less variation than cross-pollination (Kundu and Karmakar, 2022). Negative effects of self-pollination by geitonogamy have been reported, but these effects depend on the directionality of pollination (within inflorescences, between inflorescences, and between clones) (Eckert, 2000) and the degree of clonality (Hu et al., 2015). In contrast, geitonogamy has been shown to increase fruit set and seed germination compared to autogamy and even xenogamy (Johnson et al., 2009).

As is well known, the prevailing opinion is that clonality reduces genetic diversity (Franklin et al., 2021). However, other authors have suggested that clonal populations may have comparable or even greater genetic variation than non-clonal ones (Ellestad et al., 2022). Recent studies have even reported higher levels of heterozygosity in cultivated V. planifolia compared to wild specimens (Favre et al., 2022). This increased heterogeneity in V. planifolia plantations can be attributed to various factors, such as point mutations (Favre et al., 2022), hybridization, polyploidy (Ellestad et al., 2022), and a high level of epigenetic variation that may have developed in response to adverse environmental conditions (Rajpal et al., 2022).

Both genetic variation and epigenetic regulation can be inherited through meiosis and/or mitosis, although they are not directly related (Rajpal et al., 2022). This indicates that self-pollination via geitonogamy may offer advantages over autogamy by producing fruits and seeds with superior traits due to potential genetic and epigenetic variations present in clonal plants. Furthermore, this type of pollination may enhance fruit set, improve fruit retention, and increase fertilization efficiency. The data obtained in this study shows that V. planifolia can produce fruits under different pollination methods, provided that the pollination is done manually. It was observed that fruits reach their maximum length and diameter 40 days after pollination, and the pollination method significantly influences the morphometric characteristics of the fruit, including weight, length, and shape index.

Conclusions

The results of this study demonstrate that the pollen source has a significant impact on certain morphological characteristics of vanilla fruits, specifically their length, shape index, and weight. Notably, fruits produced through geitonogamy pollination exhibited better morphometric traits compared to those resulting from autogamy. This enhancement indicates improved seed viability and germination capacity, marking a significant advancement in the sexual propagation of this species. These findings present new opportunities for the strategic use of pollination methods in agriculture and for genetic improvement programs focused on V. planifolia.

Acknowledgments

The authors would like to express their gratitude to the Institute of Biotechnology and Applied Ecology of Veracruz University for their support in making this study possible. We would especially like to thank the Secretariat of Science, Humanities, Technology, and Innovation (SECIHTI, Mexico) for financing the master’s program of ZEFV and BGCR.

Data availability statement

Data will be made available upon request to the authors.

References

• ABBATE, A.; CAMPBELL. J.; WILLIAMS, G. Artificial pollination of kiwifruit (Actinidia chinensisPlanch. var.chinensis) (Ericales: Actinidiaceae) results in greater fruit set compared to flowers pollinated by managed bees (Apis melliferaL. (Hymenoptera: Apidae) andBombus impatiensCresson (Hymenoptera: Apidae). Journal of Economic Entomology, v.116, n.3, p.674-685, 2023. https://doi.org/10.1093/jee/toad044
  » https://doi.org/10.1093/jee/toad044
• ANDRIAMIHAJA, C.F.; RAMAROSANDRATANA, A.V.; GRISONI, M.; JEANNODA, V.; BESSE, P. The leaflessVanillaspecies-complex from the South-West Indian Ocean Region: A taxonomic puzzle and a model for orchid evolution and conservation research. Diversity, v.12, n.12, p.443, 2020. https://doi.org/10.3390/d12120443
  » https://doi.org/10.3390/d12120443
• ARYA, S.S.; ROOKES, J.E.; CAHILL, D.M.; LENKA, S.K. Vanillin: a review on the therapeutic prospects of a popular flavouring molecule. Advances in Traditional Medicine, v.21, p.1-17, 2021. https://doi.org/10.1007/s13596-020-00531-w
  » https://doi.org/10.1007/s13596-020-00531-w
• BARREDA-CASTILLO, J.M.; MENCHACA-GARCÍA, R.A.; MORALES-RUIZ, V. Presencia de metaxenia en frutos de 40 días pospolinización em Vanilla planifolia Andrews y V. pompona Schiede. Revista Mexicana de Ciencias Agrícolas, v.14, n.2, p.289-293, 2023. https://doi.org/10.29312/remexca.v14i2.2973
  » https://doi.org/10.29312/remexca.v14i2.2973
• BAUTISTA-AGUILAR, J.R.; IGLESIAS-ANDREU, L.G.; MARTÍNEZ-CASTILLO, J.; RAMÍREZ-MOSQUEDA, M.A.; ORTIZ-GARCÍA, M.M. In Vitro conservation and genetic stability in Vanilla planifolia Jacks. HortScience, v.56, n.12, p.1494-1498, 2021.https://doi.org/10.21273/HORTSCI16118-21
  » https://doi.org/10.21273/HORTSCI16118-21
• BORBOLLA-PÉREZ, V.; IGLESIAS-ANDREU, L.G.; ESCALANTE-MANZANO, E.A.; MARTÍNEZ-CASTILLO, J.; ORTIZ-GARCÍA, M.M.; OCTAVIO-AGUILAR, P. Molecular and microclimatic characterization of two plantations of Vanilla planifolia (Jacks ex Andrews) with divergent backgrounds of premature fruit abortion. Scientia Horticulturae, v.212, p.240-250, 2016. https://doi.org/10.1016/j.scienta.2016.10.002
  » https://doi.org/10.1016/j.scienta.2016.10.002
• CAPÓ, M.; PERELLÓ-SUAU, S.; RITA, J. Preventing inbreeding depression in Anacamptis coriophora (Orchidaceae) as a model of food-rewarding orchid. Plant Ecology, v.223, p.423-436, 2022. https://doi.org/10.1007/s11258-022-01221-0
  » https://doi.org/10.1007/s11258-022-01221-0
• DENG, L.; WANG, T.; HU, J.; YANG, X.; YAO, Y.; JIN, Z.; HUANG, Z.; SUN, G.; XIONG, B.; LIAO, L.; WANG Z. Effects of pollen sources on fruit set and fruit characteristics of ‘Fengtangli’ Plum (Prunus salicinaLindl.) based on microscopic and transcriptomic analysis. International Journal of Molecular Sciences, v.23, n.21, p.12959, 2022. https://doi.org/10.3390/ijms232112959
  » https://doi.org/10.3390/ijms232112959
• DRESSLER, I.R. The Orchids: Natural History and Classification. Cambridge: Harvard University Press, 1981. 352p.
• ECKERT, C.G. Contributions of autogamy and geitonogamy to self-fertilization in a mass-flowering, clonal plant. Ecology, v.81, n.2, p.532-542, 2000.https://doi.org/10.2307/177446
  » https://doi.org/10.2307/177446
• ELLESTAD, P.; PÉREZ-FARRERA, M.A.; BUERKI, S. Genomic insights into cultivated MexicanVanilla planifoliareveal high levels of heterozygosity stemming from hybridization. Plants, v.11, n.16, p.2090, 2022. https://doi.org/10.3390/plants11162090
  » https://doi.org/10.3390/plants11162090
• FAAST, R.; FACELLI, M.; AUSTIN, A.D. Seed viability in declining populations of Caladenia rigida (Orchidaceae): are small populations doomed. Plant Biology, v.13, n.1, p.86-95, 2011. https://doi.org/10.1111/j.1438-8677.2010.00367.x
  » https://doi.org/10.1111/j.1438-8677.2010.00367.x
• FATTORINI, R.; GLOVER, B.J. Molecular Mechanisms of Pollination Biology. Annual Reviews of Plant Biology, v.71, p.487-515, 2020. https://doi.org/10.1146/annurev-arplant-081519-040003
  » https://doi.org/10.1146/annurev-arplant-081519-040003
• FAVRE, F.; JOURDA, C.; GRISONI, M.; PIET, Q.; RIVALLAN, R.; DIJOUX, J.B.; HASCOAT, J.; LEPERS-ANDRZEJEWSKI, S.; BESSE, P.; CHARRON, C. A genome-wide assessment of the genetic diversity, evolution and relationships with allied species of the clonally propagated cropVanilla planifoliaJacks. ex Andrews. Genetic Resources and Crop Evolution, v.69, p.2125-2139, 2022. https://doi.org/10.1007/s10722-022-01362-1
  » https://doi.org/10.1007/s10722-022-01362-1
• FRANKLIN, S.; ALPERT, P.; SALGUERO-GÓMEZ, R.; JANOVSKÝ, Z.; HERBEN, T.; KLIMEŠOVÁ, J.; DOUHOVNIKOFF, V. Next-gen plant clonal ecology. Perspectives in Plant Ecology, Evolution and Systematics, v.49, p.125601, 2021. https://doi.org/10.1016/j.ppees.2021.125601
  » https://doi.org/10.1016/j.ppees.2021.125601
• HASHEMABADI, D.; KAVIANI, B.; GHOLIPOUR, H.; GHASEMI, M.; KHORRAMI-RAAD, M. Reduction of seed number in ‘Yashar’ mandarin by application of copper sulfate and different pollen grains sources. Revista Chapingo Serie Horticultura, v.29, n.2, p.5-20, 2023. https://doi.org/10.5154/r.rchsh.2022.05.007
  » https://doi.org/10.5154/r.rchsh.2022.05.007
• HERNÁNDEZ-APOLINAR, M. Identificación de polinizadores naturales de Vanilla planifolia Jacks. ex Andrews. Agroproductividad, v.9, n.11-B, p.21-22, 2016.
• HERRERA-CABRERA, B.E.; SALGADO-GARCIGLIA, R.; OCAÑO-HIGUERA, V.M.; BARRALES-CUREÑO, H.; DELGADO-ALVARO, A.; MONTIEL-MONTOYA, J.; DÍAZ-BAUTISTA, M.; ALMORIN-ALBINO, R.; REYES, C. Producción y caracterización de vainilla (Vanilla planifolia) en función de la concentración de vainillina. Revista Iberoamericana de Ciencias, v.9, n.2, p.46-62, 2022.
• HU, Y.; BARRETT, S.C.H.; ZHANG, D.Y.; LIAO, W.J. Experimental analysis of mating patterns in a clonal plant reveals contrasting modes of self-pollination. Ecology and Evolution, v.5, n.22, p.5423-5431, 2015. https://doi.org/10.1002/ece3.1801
  » https://doi.org/10.1002/ece3.1801
• JOHNSON, S.D.; EDWARDS, T.J. The structure and function of orchid pollinaria. Plant Systematics and Evolution, v.222, p.243-269, 2000. https://doi.org/10.1007/BF00984105
  » https://doi.org/10.1007/BF00984105
• JOHNSON, T.R.; STEWART, S.L.; KAUTH, P.; KANE, M.E.; PHILMAN, N. Confronting assumptions about spontaneous autogamy in populations of Eulophia alta (Orchidaceae) in south Florida: assessing the effect of pollination treatments on seed formation, seed germination and seedling development. Botanical Journal of the Linnean Society, v.161, n.1, p.78-88, 2009. https://doi.org/10.1111/j.1095-8339.2009.00992.x
  » https://doi.org/10.1111/j.1095-8339.2009.00992.x
• KAUSHAL, P.; DWIVEDI, K.K.; RADHAKRISHNA, A.; SAXENA, S.; PAUL, S.; SRIVASTAVA, M.K.; BAIG, M.J.; ROY, A.K.; MALAVIYA, D.R. Ploidy dependent expression of apomixis and its components in guinea grass (Panicum maximum Jacq.). Euphytica, v.214, n.152, 2018. https://doi.org/10.1007/s10681-018-2232-1
  » https://doi.org/10.1007/s10681-018-2232-1
• KUNDU, A.; KARMAKAR, P. Pollination ecology and breeding system of Ecbolium ligustrinum (Acanthaceae): a transition from autogamy to xenogamy through specialised plant-pollinator interactions. Acta Botanica Hungarica, v.64, n.1-2, p.137-155, 2022.https://doi.org/10.1556/034.64.2022.1-2.7
  » https://doi.org/10.1556/034.64.2022.1-2.7
• LUBINSKY, P.; VAN-DAM, M.; VAN-DAM, A. Pollination of Vanilla and evolution in the Orchidaceae. Lindleyana, v.75, p.926-929, 2006.
• PEMBERTON, R.W.; WHEELER, G.S.; MADEIRA, P.T. Bee (Hymenoptera: Apidae) pollination of Vanilla planifolia in Florida and their potential in commercial production. Florida Entomologist, v.106, n.4, p.230-237, 2023. https://doi.org/10.1653/024.106.0404
  » https://doi.org/10.1653/024.106.0404
• PEÑA-BARRIENTOS, A.; PEREA-FLORES, M.J.; MARTÍNEZ-GUTIÉRREZ, H.; PATRÓN-SOBERANO, O.A.; GONZÁLEZ-JIMÉNEZ, F.E.; VEGA-CUELLAR, M.Á.; DÁVILA-ORTIZ, G. Physicochemical, microbiological, and structural relationship of vanilla beans (Vanilla planifoliaAndrews) during traditional curing process and use of its waste. Journal of Applied Research on Medicinal and Aromatic Plants, v.32, p.100445, 2023. https://doi.org/10.1016/j.jarmap.2022.100445
  » https://doi.org/10.1016/j.jarmap.2022.100445
• RAJPAL, V.R.; RATHORE, P.; MEHTA, S.; WADHWA, N.; YADAV, P.; BERRY, E.; GOEL, S.; BHAT, V.; RAINA, S.N. Epigenetic variation: A major player in facilitating plant fitness under changing environmental conditions. Frontiers in Cell and Developmental Biology, v.10, p.1020958, 2022. https://doi.org/10.3389/fcell.2022.1020958
  » https://doi.org/10.3389/fcell.2022.1020958
• REUTEMANN, A.V.; HONFI, A.I.; KARUNARATHNE, P.; ECKERS, F.; HOJSGAARD, D.H.; MARTÍNEZ, E.J. Variation of residual sexuality rates along reproductive development in apomictic tetraploids of Paspalum Plants, v.11, n.13, p.1639, 2022. https://doi.org/10.3390/plants11131639
  » https://doi.org/10.3390/plants11131639
• ROSS, A.A.; TRAVERS, S.E. The genetic consequences of rarity in the western prairie fringed orchid (Platanthera praeclara). Conservation Genetics, v.17, p.69-77, 2015. https://doi.org/10.1007/s10592-015-0761-x
  » https://doi.org/10.1007/s10592-015-0761-x
• SAINI, S.; SAGORE, B.; JAIN, S.; MAURYA, P. Advances in the exploration of xenia and metaxenia in fruit and nut crops. In: SAHU, J.K.; DIWAN, G. Advances in horticulture crops and their challenges. Kalwakurthy: SR edu publications, 2022. p.50-64.
• TRAVERS, S.E.; ANDERSON, K.; VITT, P.; HARRIS, M.O. Breeding system and inbreeding depression in the rare orchid Platanthera praeclara in a fragmented grassland landscape. Botany, v.96, n.3, p.151-159, 2018. https://doi.org/10.1139/cjb-2017-0104
  » https://doi.org/10.1139/cjb-2017-0104
• VEGA, M.; HERNÁNDEZ, M.; HERRERA-CABRERA, B.E.; WEGIER, A. 2017. Vanilla planifolia: The IUCN Red List of Threatened Species. Available in: <Available in: https://www.iucnredlist.org/species/103090930/172970359 > Accessed on: July 4th 2024.
  » https://www.iucnredlist.org/species/103090930/172970359
• YEH, C.H.; CHEN, K.Y.; LEE, Y.I. Asymbiotic germination ofVanilla planifoliain relation to the timing of seed collection and seed pretreatments. Botanical Studies, v.62, p.6, 2021. https://doi.org/10.1186/s40529-021-00311-y
  » https://doi.org/10.1186/s40529-021-00311-y

Edited by

• Editor:
  Michele Carla Nadal (Universidad Viña del Mar, Chile)

Publication Dates

• Publication in this collection
  28 July 2025
• Date of issue
  2025

History

• Received
  30 Sept 2024
• Accepted
  26 May 2025
• Published
  30 June 2025