Overcoming dormancy in jurubeba seeds (Solanum scuticum M. Nee)

Superação de dormência em sementes de jurubeba (Solanum scuticum M. Nee)

ABSTRACT:

Solanum scuticum M. Nee, known as pickled jurubeba, displays significant commercial and ecological interest. Low seed germination rates; however, have comprised an obstacle to this species conservation and commercial viability. In this sense, this study investigated the presence and type of dormancy present in jurubeba seeds sampled from both unripe and ripe fruits. Chemical scarification (H₂SO₄ for 5, 10, 15 and 20 min), washing under running water (2 and 5 min), washing under running water for 5 minutes plus immersion in a neutral detergent solution for 15 minutes, immersion in detergent solution for 5 min, and the application of gibberellic acid (GA₃) at different concentrations (500 and 1,000 ppm), and soaking times (24 and 48 hours) were all tested. Germination rates (%G), germination speed indices (GSI) and average germination times (AGT) were assessed. The GA₃ treatment at 500 ppm and 48 hours of soaking resulted in the highest percentage of germinated seeds, of up to 84.5% for seeds from ripe fruits. These findings indicated the presence of physiological dormancy in jurubeba seeds and highlighted the effectiveness of GA₃ in promoting the germination of ripe fruit seeds.

Key words:
bitter fruit; non-conventional food plants; germination test; native seeds; Gompertz; pre-germination treatments

RESUMO:

A espécie Solanum scuticum M. Nee, conhecida como jurubeba de conserva, possui grande interesse comercial e ecológico, no entanto, a baixa germinação das sementes tem sido um obstáculo para sua conservação e viabilidade comercial. Objetivou-se com este estudo investigar a presença e o tipo de dormência em sementes de jurubeba, amostradas em frutos verdes e maduros. Foram testados escarificação química (H₂SO₄ por 5, 10, 15 e 20 min); lavagem em água corrente (2 e 5 min); lavagem em água corrente por 5 min, mais imersão em solução de detergente neutro por 15 min; imersão em solução de detergente por 5 min; e aplicação de GA₃ em diferentes concentrações (500 e 1.000 ppm) e tempos (24 e 48 horas) de embebição. Os parâmetros avaliados foram: %G, IVG e TMG. O tratamento com GA₃ na concentração de 500 ppm e 48 horas de embebição resultou na maior porcentagem de sementes germinadas, 84,5% para sementes provenientes de frutos maduros. Os resultados indicaram a presença de dormência fisiológica nas sementes de jurubeba e destacaram a eficácia do uso de GA₃ para promover a germinação em sementes de frutos maduros.

Palavras-chave:
fruto amargo; PANC; teste de germinação; sementes nativas; Gompertz; tratamentos pré-germinativos

INTRODUCTION

Solanum scuticum M. Nee, belongs to the Solanaceae Family and is known as pickled jurubeba, juna, juína and joá manso, derived from the Brazilian indigenous Tupi language, where “yú” means thorn and “peba”, flat. Among the hundreds of species popularly known as jurubeba, Solanum scuticum M. Nee is the most appreciated in pickled form (MENDONÇA & LOPES, 2019).

Jurubeba fruits have aroused significant commercial interest in Brazil, appreciated in pickled and beverage form, as well as employed as herbal medicines (LORENZI & MATOS, 2022). Furthermore, jurubeba is considered a non-conventional food plant (NCFP) and culturally associated with different Brazilian regions (OLIVEIRA et al., 2023).

Studies have demonstrated that this species is resistant to several diseases that affect Solanaceae members, such as Verticillium dahliae (MIRANDA et al., 2010), Fusarium oxysporum (PEREIRA et al., 2018) and Ralstonia solanacearum (LOPES & MENDONÇA, 2016), in addition to root-knot nematodes (Meloidogyne javanica) (CARDOSO, 2019). Thus, a high potential for its use as a rootstock or for the transfer of genes of interest is noted. Low seed germination rates; however, comprise an obstacle towards the commercial use of this species (RIBEIRO & SANTOS, 2020).

Farmers consider jurubeba an invasive plant, due to its spontaneous growth, especially in recently deforested areas or degraded pastures (ASSUNÇÃO et al., 2006). Its elimination; therefore, leads to genetic erosion and increases the risk of extinction for this species (LEROY et al., 2018). Because of this, investigations concerning the presence and type of dormancy of jurubeba seeds are paramount for this species conservation and commercial use.

Knowledge concerning quick and uniform seed germination conditions is important for plant sowing purposes, as homogeneous seedling emergence enhances seedling development. This, in turn, promotes faster and more uniform growth in both plant nurseries and in the field, which is very desirable for farming activities (CARVALHO & NAKAGAWA, 2000). However, if a certain plant species presents any germination restrictions, probable dormancy causes should be evaluated. Dormancy comprises an adaptive characteristic that ensures plant survival in different ecosystems, contributing to species endurance (VIVIAN et al., 2008).

In this context, due to the lack of available information concerning the presence and type of dormancy in jurubeba seeds, this study investigated these featured in both green and ripe jurubeba fruits.

MATERIALS AND METHODS

Study area and sampling

Seeds were sampled from 14 jurubeba mother trees in the Juruena River Valley, in the municipality of Juína, Mato Grosso, Brazil. This municipality is in northwest Mato Grosso, 750 km from the state’s capital of Cuiabá. The local climate is equatorial hot and humid, averaging about 24 ºC during the entire year, with a three-month dry period, and average precipitation of 1,876 mm (IBGE, 2002).

Samplings were carried out between February and March 2022. Green and ripe fruits were collected in bulk for each mother tree. A minimum distance of 100 meters between trees was established, as well as the presence of green and ripe fruits.

Dormancy-breaking treatments

The treatments used to overcome seed dormancy were applied according to the Brazilian Rules for Seed Analysis (RAS) to identify different dormancy types, whether physical, chemical or physiological (BRASIL, 2009).

The seeds were extracted from the ripe and unripe fruits, manually selected and dried for 24 hours at room temperature (± 25 ºC). After drying, they were homogenized to form sample batches and subsequent water content determination were carried out by oven drying at 105 ºC for 24 hours (BRASIL, 2009 adapted). The average water content was determined as 8.8%.

The following four treatments were applied to assess physical dormancy: T1 - chemical scarification with H₂SO₄ (36 N for 5 min); T2 - chemical scarification with H₂SO₄ (36 N for 10 min); T3 - chemical scarification with H₂SO₄ (36 N for 15 min); T4 - chemical scarification with H₂SO₄ (36 N fir 20 min).

The following four treatments were applied to assess chemical dormancy: T5 - washing under running water for 2 min; T6 - washing under running water for 5 min; T7 - washing under running water for 5 min, followed by immersion in a neutral detergent solution (15 mL/100 mL H₂O) for 5 min; T8 - immersion in a neutral detergent solution (15 mL/100 mL H₂O) for 5 min.

The following five treatments were applied to assess the presence of physiological dormancy: T10 - gibberellic acid application (GA₃) at 500 ppm for 24 h; T11 - GA₃ application at 500 ppm for 48 h; T12 - GA₃ application at 1000 ppm for 24 h; T13 - GA₃ application at 1000 ppm for 48 h. Treatment T9 comprised the control group, in which seeds did not receive any special treatment.

The plots were composed of 50 seeds, placed on a germi test sheet moistened with distilled water 2.5 times the weight of the dry paper. A second sheet was placed over the seeds and the set was rolled up and placed in the BOD-type germination chamber under a 12-hour photoperiod at 30 ºC (BRASIL, 2009 adapted).

Evaluated parameters and experimental design

Assessments were carried out daily, recording the number of seeds emitting primary roots over 2 mm in length, from the 4^th day after beginning of the germination test. Germination percentages (%G), germination speed indices (GSI) (MAGUIRE, 1962), and average germination time (AGT) (LABOURIAU, 1983) were evaluated. A double factorial design was applied involving fruit maturation (encompassing two categories, green and ripe) and thirteen treatments to overcome physical, chemical, and physiological dormancies, comprising four replications each.

Statistical analyses

An analysis of variance was carried out at 5% significance, where %G, GSI and AGT were considered dependent variables, while the interaction between the type of treatments and degree of fruit ripeness comprised independent variables. The Scott-Knott multiple comparison procedure between means was applied at a significant level of 0.05. All analyses were performed using the R version 4.2.0 software.

The treatment presenting the best performance concerning %G was further analyzed by the Gompertz model, to assess the average behavior of this variable throughout the experiment, as follows:

$\%G={\beta }_1.e^{[-{\beta }_2.e\left(-{\beta }_3.time\right)]}$

Where β1 represents the maximum expected value of the response, i.e., the asymptotic value, β2 comprises an integration constant and β3, is the curve growth rate.

RESULTS AND DISCUSSION

A significant interaction was observed between fruit maturation (green and ripe) and all dormancy treatments for all variables. When evaluating the multiple comparison (Figure 1) concerning %G and GSI, the interaction between ripe fruits and the GA₃ treatment at 500 ppm for 48 h led to the best performance. For this treatment, %G from ripe fruit seeds was calculated at 84.5%, suggesting the presence of physiological dormancy in jurubeba seeds (Figure 1A). This became more evident when noting that the four treatments employed to overcome physiological dormancy (T11, T10, T12 and T13) resulted in the highest %G values. Furthermore, these were the only treatments that led to any positive response for green seeds, despite very low germinations rates, ranging from 3 to 4.5%. These findings, therefore, indicated the effectiveness of the GA₃ treatment at 500 ppm for germinating mature jurubeba seeds soaked for 48 hours. However, further morpho-histological and physiological studies are required to better elucidate the mechanisms underlying seed dormancy in this species.

Figure 1
Interaction between treatments and degree of fruit maturation for %G (A), GSI (B) and AGT (C) for Solanum scuticum. Means alongside capital letters followed by the same letter do not differ concerning degree of maturation (ripe and green); Medium lowercase letters followed by each other do not differ concerning treatment. Treatment 1: scarification with H₂SO₄ for 5 min; T2: scarification with H₂SO₄ for 10 min; T3: scarification with H₂SO₄ for 15 min; T4: scarification with H₂SO₄ for 20 min; T5: washing under running water for 2 min; T6: washing under running water for 5 min; T7: washing under running water for 5 minutes, plus immersion in a neutral detergent solution for 5 minutes; T8: immersion in a neutral detergent solution for 5 min; T9: control group; T10: GA₃ application at 500 ppm for 24 h; T11: GA₃ application at 500 ppm for 48 h; T12: GA₃ application at 1000 ppm for 24 h; T13: GA₃ application at 1000 ppm for 48 h.

Physiological dormancy is controlled by genetic factors and metabolic levels, and can be confirmed through dormancy overcoming tests, such as thermal stratification, or using GA₃ (CARDOSO, 2009). According to STENZEL et al. (2003) the exogenous application of GA₃ stimulates plant germination, promoting the synthesis of enzymes such as α and β-amylase. These enzymes are responsible for releasing the energy reserves present in the seed endosperm, resulting in the formation of nucleic acids, amino acids and, mainly, sugars. These compounds are then translocated to developing embryo regions, promoting cell elongation and tegument disruption at the root, leading to more uniform germination.

The chemical scarification treatments applied herein (T1, T2, T3, T4) resulted in low %G, ranging from zero to 2% for ripe fruit seeds, while no variations were noted for seeds from unripe fruits (Figure 1A). These germination rates were lower than those of the control group, suggesting that the applied chemical scarification treatments under the studied conditions may have damaged both the endosperm and the embryo. Although, chemical scarification can facilitate water entry in cases of physical (integumentary) dormancy and accelerate seed germination, prolonged seed exposure or high concentrations of germinating compounds can lead to low germination rates, such as those observed herein. Therefore, these treatments are not recommended at the H₂SO₄ concentration and seed exposure time employed in this study. Conversely, SILVA et al. (2020) reported a germination rate of 55% in mature Solanum paniculatum L. seeds subjected to an 11-to-12-minute immersion in H₂SO₄, attributed to integumentary seed dormancy.

Regarding the chemical dormancy treatments, T5 did not differ statistically from the control group, reaching a %G of 13%. T6 differed from the other treatments, resulting in a 4.5% %G, and differed from T5 only by the longer seed wash time under running water, although this variation did not increase %G. Similarly, T7 and T8, both employing a neutral detergent, resulted in a very low %G, from 0 to 0.5%. This indicated an antagonistic detergent effect on seed germination. Therefore, seed washing and neutral detergent use did not result in germination gains for jurubeba seeds.

These results differed from those reported by GARCIA et al.,(2008) who evaluated ripe jurubeba (Solanum paniculatum L.) fruit seed germination rates. Germination rates of up to 65.6% were observed when the seeds were washed for five minutes and immersed in a detergent solution for another five minutes, followed by washing under running water for another two minutes. This %G values is much higher than that reported herein, suggesting different dormancy mechanisms for different jurubeba species.

The GSI and AGT parameters are associated to germination speeds, with higher GSI values and lower AGT values indicating higher germination speeds (SILVA et al., 2020). The T11 treatment, applied to seeds from ripe fruits, presented the highest GSI, of 5.68 seeds per day, followed by the other GA₃ treatments (T10 and T13) (Figure 1B). A significant increase in GSI was observed with longer seed immersion times in the GA₃ solution. No significant difference was observed between the treatments that resulted in green fruit seed germination.

Concerning AGT (Figure 1C), with the exception of T7, all treatments leading to %G above zero did not differ statistically from each other, presenting AGT values varying from 8.75 to 10.69 days for mature fruit. As noted for GSI, no significant difference was observed between treatments that resulted in green fruit seed germination.

Due to the best results observed for the interaction between ripe fruits and T11 concerning %G, this treatment was chosen to adjust the non-linear Gompertz model to explain the average behavior of this variable over time. Based on the estimated coefficients and the generated curve (Figure 2), the estimated β1 value is 78.94, which represents the maximum expected percentage of jurubeba seed germination rates following GA₃ treatment. This means that, under ideal conditions, around 78.95% of seeds are expected to germinate after applying this treatment.

Figure 2
Gompertz model adjusted to model percentage germination rates over time for Solanum scuticum using 500 ppm gibberellic acid (GA₃) for 48 hours.

The estimated coefficient β2 (17.11) influences the vertical position of the growth curve. Therefore, in the case of jurubeba seeds treated with GA₃, this value suggested that the germination curve begins to increase from an initial minimum value. Thus, seeds begin the germination process after the applied treatment, gradually reaching the estimated maximum percentage.

Finally, the estimated parameter β3 (0.50) represents the growth rate of the germination curve. In this context, the 0.50 value indicates a moderate germination rate increase over time, without following an exponential pattern. This trend is depicted in figure 2, where the germination percentage stabilizes from the 15^th day after GA₃ application.

CONCLUSION

Seeds from both ripe and unripe jurubeba seeds present dormancies, indicating a physiological phenomenon. Seeds from green fruits did not exhibit satisfactory germination rates, even after different treatments applied to overcome dormancy. The use of GA₃ at 500 ppm and 48 hours of soaking is recommended for ripe fruit seeds to overcome dormancy.

ACKNOWLEDGEMENTS

The authors would like to thank Instituto Federal de Educação Ciência e Tecnologia de Mato Grosso (IFMT) campus Juína and Instituto Federal Goiano (IF Goiano) campus Rio Verde, for providing financial support. This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES).

REFERENCES

• ASSUNÇÃO, I. P. et al. Occurrence of Curvularia lunata on “Jurubeba” in Alagoas State, Brazil. Summa Phytopathologica, Botucatu, v.32, n.04, set. p.386-387, 2006. Available from: <Available from: https://www.scielo.br/j/sp/a/Cnx8pGffhcM9Q54Mr6sqs4C/?lang=pt#:~:text=Esse%20estudo%20relata%20a%20ocorr%C3%AAncia,como%20tomate%2C%20fumo%20e%20pimenta. >. Accessed: Jul. 15, 2023. doi: 10.1590/S0100-54052006000400014.
  » https://www.scielo.br/j/sp/a/Cnx8pGffhcM9Q54Mr6sqs4C/?lang=pt#:~:text=Esse%20estudo%20relata%20a%20ocorr%C3%AAncia,como%20tomate%2C%20fumo%20e%20pimenta.
• BRASIL. Regras para análise de sementes. 1. ed. Brasília: MINISTÉRIO DA AGRICULTURA, PECUÁRIA E ABASTECIMENTO, 2009. 399 p.
• CARDOSO, J. et al. Reaction of wild Solanaceae rootstocks to the parasitism of (Meloidogyne javanica). Horticultura Brasileira, v.1, p.17-21, 2019. Available from: <Available from: https://www.scielo.br/j/hb/a/tD9KN4YGJgbRpBGFxwfRckS/?lang=en >. Accessed: Jul. 15, 2023. doi: 10.1590/s0102-053620190102.
  » https://doi.org/10.1590/s0102-053620190102.» https://www.scielo.br/j/hb/a/tD9KN4YGJgbRpBGFxwfRckS/?lang=en
• CARDOSO, V. J. M. Concepts and classification systems in seed dormancy. Oecologia Brasiliensis, v.4, p.619-631, 2009. Available from: <Available from: https://revistas.ufrj.br/index.php/oa/article/view/5770 >. Accessed: Jul. 15, 2023. doi: 10.4257/oeco.2009.1304.06.
  » https://doi.org/10.4257/oeco.2009.1304.06.» https://revistas.ufrj.br/index.php/oa/article/view/5770
• CARVALHO, N. M.; NAKAGAWA, J. Sementes: ciência, tecnologia e produção. 4.ed. Jaboticabal: FUNEP, 2000. 588p.
• GARCIA, J. et al. Effectiveness of methods to increase. Pesquisa Agropecuária Tropical, Goiânia, v.38, n.3, p.223-226, 2008. Available from: <Available from: https://www.redalyc.org/pdf/2530/253020408012.pdf >. Accessed: Jul. 12, 2023. doi: 10.5216/pat.v38i3.4846.
  » https://doi.org/10.5216/pat.v38i3.4846.» https://www.redalyc.org/pdf/2530/253020408012.pdf
• IBGE. Mapa de clima do Brasil. Direção de Geociências. Escala 1:5000000. Instituto Brasileiro de Geografia e Estatística. Rio de Janeiro. 2002.
• LABOURIAU, L. G. A germinação das sementes. Washington: Secretaria Geral da Organização dos Estados Americanos, 1983. 174p.
• LEROY, G. et al. Next-generation metrics for monitoring genetic erosion within populations of conservation concern. Evolutionary Applications, v.11, n.07, p.1066-1083, 2018. Available from: <Available from: https://onlinelibrary.wiley.com/doi/full/10.1111/eva.12564 >. Accessed: Jul. 12, 2023. doi: 10.1111/eva.12564.
  » https://doi.org/10.1111/eva.12564.» https://onlinelibrary.wiley.com/doi/full/10.1111/eva.12564
• LOPES, C. A.; MENDONÇA, J. L . Reactionof accessions of two species of “jurubeba” as rootstocks to protect tomato plants against bacterial wilt. Horticultura Brasileira, v.34, p.356-360, . 2016Available from: <Available from: https://www.scielo.br/j/hb/a/rwW65N489NPKStWSLJvncnC/?lang=pt >. Accessed: Jul. 15, 2023. doi: 10.1590/S0102-05362016003008.
  » https://doi.org/10.1590/S0102-05362016003008.» https://www.scielo.br/j/hb/a/rwW65N489NPKStWSLJvncnC/?lang=pt
• LORENZI, H.; MATOS, F. J. Plantas medicinais no Brasil: nativas e exóticas cultivadas. [S.l.]: Nova Odessa, 2022.
• MAGUIRE, J. D. Speed of germination aid in selection and evaluation for seeding emergence and vigor. Crop Science, v.2, n.2, p.76-177, 1962. Available from: <Available from: https://acsess.onlinelibrary.wiley.com/doi/epdf/10.2135/cropsci1962.0011183X000200020033x >. Accessed: Jul. 12, 2023. doi: 10.2135/cropsci1962.0011183X000200020033x.
  » https://doi.org/10.2135/cropsci1962.0011183X000200020033x.» https://acsess.onlinelibrary.wiley.com/doi/epdf/10.2135/cropsci1962.0011183X000200020033x
• MENDONÇA, J. L. D.; LOPES, J. F. Coleção de germoplasma de espécies silvestres de Solanum da Embrapa. 1º. ed. BRASÍLIA: EMBRAPA, v.168, 2019.
• MIRANDA, B. E. C. D. et al. Sources of resistance to Verticillium dahliae races 1 and 2 in accessions of Solanum (section Lycopersicon). Horticultura Brasileira, 28, n.04, dezembro, p.458-465, 2010. Available from: <Available from: https://www.scielo.br/j/hb/a/X79j5gLxschB5WrMMNwzjZk/ >. Accessed: Jul. 15, 2023. doi: 10.1590/S0102-05362010000400014.
  » https://doi.org/10.1590/S0102-05362010000400014.» https://www.scielo.br/j/hb/a/X79j5gLxschB5WrMMNwzjZk/
• OLIVEIRA, A. C. M. et al. Tea knowledge exchange in Diamantina (MG) and region. Brazilian Journal of Development, Curitiba, 09, n.03, mar, p.11541-11561, 2023. Available from: <Available from: https://ojs.brazilianjournals.com.br/ojs/index.php/BRJD/article/view/57771 >. Accessed: Jul. 14, 2023. doi: 10.34117/bjdv9n3-036.
  » https://doi.org/10.34117/bjdv9n3-036.» https://ojs.brazilianjournals.com.br/ojs/index.php/BRJD/article/view/57771
• PEREIRA, R. B. et al. Evaluation of resistance of Solanum scuticum accessions to soil-borne pathogens in tomato crops in Brazil. Acta Horticulturae, p.55-62, 2018. Available from: <Available from: https://www.actahort.org/books/1207/1207_7.htm >. Accessed: Jul. 12, 2023. doi: 10.17660/ActaHortic.2018.1207.7.
  » https://doi.org/10.17660/ActaHortic.2018.1207.7» https://www.actahort.org/books/1207/1207_7.htm
• RIBEIRO, J. C.; SANTOS, C. A. D. Competência técnica e responsabilidade social e ambiental nas ciências agrárias 2. Ponta Grossa - PR: Atenas, 2020.
• SILVA, E. J. S. D. et al. Biometric characterization of Solanum paniculatum L. seeds and germinative performance after dormancy overcoming. Colloquium Agrariae, 16, jul, p.29-37, 2020. Available from: <Available from: https://revistas.unoeste.br/index.php/ca/article/view/3385 >. Accessed: Jul. 14, 2023. doi: 10.5747/ca.2020.v16.n4.a380.
  » https://doi.org/10.5747/ca.2020.v16.n4.a380.» https://revistas.unoeste.br/index.php/ca/article/view/3385
• STENZEL, N. M. C. et al. Overcoming atemoya and custard apple seed dormancy. Revista Brasileira de Fruticultura, Jaboticabal, v.25, n.2, p.305-308, 2003. Available from: <Available from: https://www.scielo.br/j/rbf/a/FYgT3S54yJPv4cj9ggvPxdn/abstract/?lang=en >. Accessed: Jul. 11, 2023. doi: 10.1590/S0100-29452003000200031.
  » https://doi.org/10.1590/S0100-29452003000200031.» https://www.scielo.br/j/rbf/a/FYgT3S54yJPv4cj9ggvPxdn/abstract/?lang=en
• VIVIAN, R. et al. Weed seed dormancy as a survival mechanism: brief review. Planta Daninha, v.26, n.3, p.695-706, 2008. Available from: <Available from: https://www.scielo.br/j/pd/a/8PjyFPGMR7SWnCvjyFDfWDM/ >. Accessed: Jul. 11, 2023. doi: 10.1590/S0100-83582008000300026.
  » https://doi.org/10.1590/S0100-83582008000300026.» https://www.scielo.br/j/pd/a/8PjyFPGMR7SWnCvjyFDfWDM/

• CR-2023-0301.R2

Edited by

• Editors
  Leandro Souza da Silva (0000-0002-1636-6643) Marcos Meiado (0000-0002-9334-5985)

Publication Dates

• Publication in this collection
  09 May 2025
• Date of issue
  2025

History

• Received
  10 Nov 2023
• Accepted
  28 Oct 2024
• Reviewed
  30 Jan 2025