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Plant extracts in agriculture and their applications in the treatment of seeds

Extratos vegetais na agricultura e suas aplicações no tratamento de sementes

ABSTRACT:

The harmful effects caused by the use of toxic substances in agriculture have led to the development of alternative solutions, and researchers have focused on understanding the effectiveness and potential of plant extracts in agriculture. The aim of this systematic review was to understand the situation of research and scientific dissemination, as well as how current science has approached the use of plant extracts in agriculture, especially in seed applications. There is potential on the use of plant extracts in agriculture, demonstrated by a high number of publications over the last ten years, especially in the years 2018, 2019 and 2020, and Brazil stands out as the main country on this research area. Control of phytopathogenic microorganisms, insect control, biostimulant effect, resistance induction and herbicide effect have been the main themes explored for use in agriculture. The direct application of plant extracts is centered on plants and seeds, being this latter mainly focused on the control of phytopathogenic organisms and biostimulating effect.

Key words:
biostimulant effects; insect control; phytopathogenic organisms; seed health

RESUMO:

Em resposta aos efeitos nocivos da utilização de substâncias toxicas na agricultura, a ciência tem avançado no desenvolvimento de soluções alternativas, visando compreender a eficácia e o potencial de extratos vegetais na agricultura. Objetivou-se com esta revisão sistematizada compreender a situação da pesquisa e divulgação científica, bem como a maneira que a ciência atual tem abordado o uso de extratos vegetais na agricultura, especialmente na aplicação em sementes. O uso de extratos vegetais na agricultura tem potencial demonstrado pelo elevado número de publicações nos últimos dez anos, com destaque para os anos de 2018, 2019 e 2020, sendo o Brasil o país de maior produção de trabalhos voltados à essa área de estudo. Os temas controle de microrganismos fitopatogênicos, controle de insetos, efeito bioestimulante, indução de resistência e efeito herbicida tem sido os principais temas explorados para uso na agricultura. A aplicação de extratos vegetais é centrada principalmente em organismos fitopatogênicos associados a plantas e sementes, sendo que, para a aplicação em sementes, o foco está no controle de organismos fitopatogênicos e efeito de promoção de crescimento.

Palavras-chave:
controle de insetos; promoção de crescimento; organismos fitopatogênicos; sanidade de sementes

INTRODUCTION:

The process of agriculture expansion and the greater demand for food in recent years led to the rise in the use of synthetic products that are toxic for the management of production fields, which has been triggering a set of problems to the environment, farmers and consumers (SCHÜTTE et al., 2017SCHÜTTE, G. et al. Herbicide resistance and biodiversity: agronomic and environmental aspects of genetically modified herbicide-resistant plants. Environmental Sciences Europe, [s.l.], v.29, no.1, p.5, 2017. Available from: <Available from: https://doi.org/10.1186/s12302-016-0100-y >. Accessed: Oct. 12, 2020. doi: 10.1186/s12302-016-0100-y.
https://doi.org/10.1186/s12302-016-0100-...
).

Given the need for the application of ecological strategies in agriculture, there is an increasing interest in research in different areas, which aim to explore the potentialities of the plant extracts in agriculture (ARSHAD et al., 2019ARSHAD, M. et al. Field evaluation of water plant extracts on sucking insect pests and their associated predators in transgenic Bt cotton. Egyptian Journal of Biological Pest Control, [s.l.], v.29, n.1, 2019. Available from: <Available from: https://doi.org/10.1186/s41938-019-0142-8 >. Accessed: Oct. 12, 2020. doi: 10.1186/s41938-019-0142-8.
https://doi.org/10.1186/s41938-019-0142-...
; AL-MOHMADI; AL-ANI, 2019AL-MOHMADI, S. Y. A.; AL-ANI, M. H. I. Effect of spraying with different concentration of licorice extract and plant densities in growth and yield of sorghum bicolor l. Iraqi Journal of Agricultural sciences, [s.l.], v.50, n.6, p.1478-1485, 2019. Available from: <Available from: https://doi.org/10.36103/ijas.v50i6.835 >. Accessed: Oct. 09, 2020. doi: 10.36103/ijas.v50i6.835.
https://doi.org/10.36103/ijas.v50i6.835...
). The plant extracts acts as inducers of resistance in plants (COSTA et al., 2019COSTA, A. P. et al. Aquosous extract and essential oil of ginger induce biochemical defense mechanisms in bean. Journal of Neotropical Agriculture, [s.l.], v.6, n.2, p.79-86, 2019. Available from: <10.32404/rean.v6i2.2721>. Accessed: Oct. 12, 2020. doi: 10.32404/rean.v6i2.2721.
https://doi.org/10.32404/rean.v6i2.2721....
), as biostimulants (COZZOLINO et al., 2020COZZOLINO, E. et al. Appraisal of biodegradable mulching films and vegetal-derived biostimulant application as eco-sustainable practices for enhancing lettuce crop performance and nutritive value. Agronomy , [s.l.], v.10, n.3, 2020. Available from: <Available from: https://doi.org/10.3390/agronomy10030427 >. Accessed: Oct. 12, 2020. doi: 10.3390/agronomy10030427.
https://doi.org/10.3390/agronomy10030427...
), have herbicide effect (ZAKA et al., 2019ZAKA, S. M. et al. Toxic effects of some insecticides, herbicides, and plant essential oils against Tribolium confusum Jacquelin du val (Insecta: Coleoptera: Tenebrionidae). Saudi Journal of Biological Sciences, [s.l.], v.26, no.7, p.1767-1771, 2019. Available from: <Available from: https://doi.org/10.1016/j.sjbs.2018.05.012 >. Accessed: Oct. 12, 2020. doi: 10.1016/j.sjbs.2018.05.012.
https://doi.org/10.1016/j.sjbs.2018.05.0...
; FINDURA et al., 2020FINDURA, P.. et al. Evaluation of the effects of allelopathic aqueous plant extracts, as potential preparations for seed dressing, on the modulation of cauliflower seed germination. Agriculture, [s.l.], v.10, n.4, 2020. Available from: <Available from: https://doi.org/10.3390/agriculture10040122 >. Accessed: Oct. 12, 2020. doi: 10.3390/agriculture10040122.
https://doi.org/10.3390/agriculture10040...
), nematicides (MÜLLER et al., 2016MÜLLER, M. A. et al. In vitro toxicity and control of Meloidogyne incognita in soybean by rosemary extract. Semina: Ciências Agrárias , [s.l.], v.37, no.1, p.103-110, 2016. Available from: <Available from: http://dx.doi.org/10.5433/1679-0359.2016v37n1p103 >. Accessed: Oct. 12, 2020. doi: 10.5433/1679-0359.2016v37n1p103.
http://dx.doi.org/10.5433/1679-0359.2016...
; COLTRO-RONCATO et al., 2016COLTRO-RONCATO, S. et al. Nematicidal activity of crambe extracts on Meloidogyne spp. Semina: Ciências Agrarias, [s.l.], v.37, n.4, p.1857-1870, 2016. ISSN: 16790359. Available from: <Available from: http://dx.doi.org/10.5433/1679-0359.2016v37n4p1857 >. Accessed: Oct. 12, 2020. doi: 10.5433/1679-0359.2016v37n4p1857.
http://dx.doi.org/10.5433/1679-0359.2016...
) and insecticides effects (PAVELA et al., 2018PAVELA, R. et al. Oviposition inhibitory activity of the Mexican sunflower Tithonia diversifolia (Asteraceae) polar extracts against the two-spotted spider mite Tetranychus urticae (Tetranychidae). Physiological and Molecular Plant Pathology, [s.l.], v.101, p.85-92, 2018. Available from: <Available from: https://doi.org/10.1016/j.pmpp.2016.11.002 >. Accessed: Oct. 12, 2020. doi: 10.1016/j.pmpp.2016.11.002.
https://doi.org/10.1016/j.pmpp.2016.11.0...
); and especially, fungicide effect for the control of phytopathogenic organisms (MEENA et al., 2020MEENA, R. P. et al. Efficacy of fungicides and plant extracts against Alternaria alternata causing leaf blight of chandrasur (Lepidium sativum). Indian Journal of Agricultural Sciences , [s.l.], v.90, n.2, p.337-340, 2020. Available from: <Available from: https://www.researchgate.net/publication/339677934_Efficacy_of_fungicides_and_plant_extracts_against_Alternaria_alternata_causing_leaf_blight_of_chandrasur_Lepidium_sativum >. Accessed: Oct. 12, 2020. ISSN: 00195022.
https://www.researchgate.net/publication...
; NCISE et al., 2020NCISE, W et al. Effects of light intensities and varying watering intervals on growth, tissue nutrient content and antifungal activity of hydroponic cultivated Tulbaghia violacea L. under greenhouse conditions. Heliyon, [s.l.], v.6, no.5, 2020. Available from: <Available from: https://doi.org/10.1016/j.heliyon.2020.e03906 >. Accessed: Oct. 12, 2020. doi: 10.1016/j.heliyon.2020.e03906.
https://doi.org/10.1016/j.heliyon.2020.e...
).

There are innumerable potentialities for plant extracts in agriculture. The application in seed treatment has been explored as an alternative (KARABÜYÜK& AYSAN, 2019KARABÜYÜK, F.; AYSAN, Y. Antibacterial effects of some plant extracts against tomato bacterial speck disease caused by Pseudomonas syringae pv. tomato. Journal of Tekirdag Agricultural Faculty, 2019. Available from: <Available from: https://doi.org/10.33462/jotaf.529499 >. Accessed: Oct. 12, 2020. doi: 10.33462/jotaf.529499.
https://doi.org/10.33462/jotaf.529499...
) for diverse purposes, especially in the control of phytopathogenic organisms linked to seeds. (MANGWENDE et al., 2019MANGWENDE, E. Control of Alternaria leaf spot of coenter in OrganicAgriculture . European Journal of Plant Pathology, [s.l.], v.154, n.3, p.575-584, 2019. ISSN: 0929-1873. Available from: <Available from: https://doi.org/10.1007/s10658-019-01682-6 >. Accessed: Oct. 12, 2020. doi: 10.1007/s10658-019-01682-6.
https://doi.org/10.1007/s10658-019-01682...
; CHANDEL & KUMAR, 2017CHANDEL, S.; KUMAR, V. Effect of plant extracts as pre-storage seed treatment on storage fungi, germination percentage and seedling vigour of pea (Pisum sativum). Indian Journal of Agricultural Sciences, [s.l.], v.87, n.11, p.1476-1481, 2017. Available from: <Available from: http://epubs.icar.org.in/.../75703 >. Accessed: Oct. 12, 2020. ISSN: 00195022.
http://epubs.icar.org.in/.../75703...
). Other purposes are biostimulant effect on germination and initial seedling establishment (RAFI et al., 2015RAFI, H et al. Seed priming with extracts of Acacia nilotica (L.) Willd. Ex delile and Sapindus mukorossi (L.) Plant parts in the control of root rot fungi and growth of plants. Pakistan Journal of Botany , [s.l.], v.47, no.3, p.1129-1135, 2015. Available from: <Available from: https://www.pakbs.org/pjbot/PDFs/47(3)/37.pdf >. Accessed: Oct. 12, 2020. ISSN: 0556-3321.
https://www.pakbs.org/pjbot/PDFs/47(3)/3...
), inducers of resistance in seedlings after emergence (ALSAHLI et al., 2018ALSAHLI, A. A. et al. Extract from Curcuma longa L. triggers the sunflower immune system and induces defence-related genes against Fusarium root rot. Phytopathologia Mediterranea, [s.l.], v.57, n.1, p.26-36, 2018. Available from:: <Available from:: https://doi.org/10.14601/Phytopathol_Mediterr-21176 >. Accessed: Oct. 09, 2020. doi: 10.14601/Phytopathol_Mediterr-21176.
https://doi.org/10.14601/Phytopathol_Med...
) and bioherbicides effect when related to the establishment of spontaneous plants (FINDURA et al., 2020FINDURA, P.. et al. Evaluation of the effects of allelopathic aqueous plant extracts, as potential preparations for seed dressing, on the modulation of cauliflower seed germination. Agriculture, [s.l.], v.10, n.4, 2020. Available from: <Available from: https://doi.org/10.3390/agriculture10040122 >. Accessed: Oct. 12, 2020. doi: 10.3390/agriculture10040122.
https://doi.org/10.3390/agriculture10040...
; KAAB et al., 2020KAAB, S. B. et al. Screening of Tunisian plant extracts for herbicidal activity and formulation of a bioherbicide based on Cynara cardunculus. South African Journal of Botany, [s.l.], v.128, p.67-76, 2020. Available from: <Available from: https://doi.org/10.1016/j.sajb.2019.10.018 >. Accessed: Oct. 12, 2020. doi: 10.1016/j.sajb.2019.10.018.
https://doi.org/10.1016/j.sajb.2019.10.0...
).

In agriculture, the seed has an important role, since it corresponds to the beginning of the stage of formation of an agricultural production field, and its quality can be affected by the presence of phytopathogenic organisms and pests (MAXIMIANO et al., 2018MAXIMIANO, C. V et al. Physiological and sanitary quality of maize seeds preconditioned in ozonated water. Revista Brasileira de Engenharia Agrícola e Ambiental, [s.l.], v.22, n.5, p.360-365, 2018. Available from: <Available from: http://dx.doi.org/10.1590/1807-1929/agriambi.v22n5p360-365 >. Accessed: Oct. 12, 2020. doi: 10.1590/1807-1929/agriambi.v22n5p360-365.
http://dx.doi.org/10.1590/1807-1929/agri...
; PARIKH et al., 2018PARIKH, L. et al. Identification and pathogenicity of Fusarium spp. in row crops in Nebraska. Crop Protection , [s.l.], v.108, no September 2017, p.120-127, 2018. Available from: <Available from: https://doi.org/10.1016/j.cropro.2018.02.019 >. Accessed: Oct. 12, 2020. doi: 10.1016/j.cropro.2018.02.019.
https://doi.org/10.1016/j.cropro.2018.02...
) which can damage the seeds during storage (WORDELL FILHO et al., 2016WORDELL FILHO, J. A. et al. Pragas e doenças do milho: Diagnose, danos e estratégias de manejo. Empresa de Pesquisa Agropecuária e Extensão Rural de Santa Catarina, [s.l.], p.82, 2016. Available from: <Available from: https://publicacoes.epagri.sc.gov.br/BT/article/view/430/325 >. Accessed: Oct. 12, 2020.
https://publicacoes.epagri.sc.gov.br/BT/...
). Therefore, searching for a more sustainable agriculture, plant extracts have also been tested as an important tool for seed treatment (KAMRAN et al., 2013KAMRAN, M. et al. Effect of plant extracted smoke and reversion of abscisic acid stress on lettuce. Pakistan Journal of Botany , [s.l.], v.45, n.5, p.1541-1549, 2013. Available from: <Available from: https://www.researchgate.net/publication/256465190_Effect_of_plant_extracted_smoke_and_reversion_of_abscisic_acid_stress_on_lettuce >. Accessed: Oct. 12, 2020. ISSN: 05563321.
https://www.researchgate.net/publication...
; CHANDEL & KUMAR, 2017CHANDEL, S.; KUMAR, V. Effect of plant extracts as pre-storage seed treatment on storage fungi, germination percentage and seedling vigour of pea (Pisum sativum). Indian Journal of Agricultural Sciences, [s.l.], v.87, n.11, p.1476-1481, 2017. Available from: <Available from: http://epubs.icar.org.in/.../75703 >. Accessed: Oct. 12, 2020. ISSN: 00195022.
http://epubs.icar.org.in/.../75703...
; OJO et al., 2020OJO, D. O. et al. Effects of Cleistopholis patens (Benth) extracts on cowpea seed beetle, Callosobruchus maculatus (Fab.) (Coleoptera: Chrysomelidae) infesting cowpea seeds in storage. International Journal of Tropical Insect Science, [s.l.], 2020. Available from: <Available from: https://doi.org/10.1007/s42690-020-00194-9 >. Accessed: Oct. 12, 2020. doi: 10.1007/s42690-020-00194-9.
https://doi.org/10.1007/s42690-020-00194...
).

Despite the intensification in the number of studies that aim to understand the efficacy and potential of plant extracts, this information is still very specific to the biological systems analyzed, without encompassing the production systems and all potentialities of application, generating gaps that need to be better understood. For this, in addition to the application of plant extracts, it becomes necessary to understand how and where the research in this field has been performed and disseminated, generating useful information for planning, executing and publishing future research directed to the use of plant extracts in agriculture, focusing on the application in seeds.

Given the above, the aim of this research was to understand, by a systematic review, the situation of research and scientific dissemination, as well as how current Science has been approaching the topic of the use of plant extracts in agriculture, especially the application in seeds.

DEVELOPMENT

For the accomplishment and constitution of the scope of this systematic review, articles indexed in the database Web of Science were selected, since it is the main worldwide database for the indexing of articles linked to journals with high international visibility.

For a better definition of the terms for the search, previous searches were performed using different strategies based on boolean operators, using basic search, with a time frame from 2010 to August 2020. After the analysis of this search and evaluating the articles aligned with the topic of the review, the following set of key terms was defined: “plant* extract*” and agriculture; “plant* extract*” and “seed* treatment*”; “plant* extract* and “alternative control”; “plant* extract*” and “seed germination” and “plant* extract*” and seed fungi. The inclusion criterion was defined as only those studies applied and directly related to the use of plant extracts in agriculture and; therefore, articles of review, and of the fields of zootechnics, medicine, fishing engineering, veterinary and researches that were not related to the subject in question were not selected.

Therefore, 283 articles were selected, which were dealing with and making reference to the subject of study of this review. They were once more evaluated, excluding 82 duplicated, totalizing 201 studies in the final scope of the systematic review that were identified in relation to the year of publication, associated journal and countries in which the research was developed.

Subsequently, the guiding criteria and topics for data analysis were defined, namely: 1st Use in agriculture: (A) Insects: control of insect pests/effect on the biology of insects/insect repellency; (B) Phytopathogenic organisms: control of diseases/effect on the biology of fungi/bacteria/nematodes (in vitro/in vivo/both); (C) Herbicide effect: allelopathic effect/control of plants; (D) Resistance induction: resistance to insects/pathogens/abiotic factors; (E) Biostimulant effect: growth promotion effect/production; (F) Others; 2nd Application: (A) Plant (in vitro/in vivo/both); (B) Postharvest (in vitro/in vivo/both); (C) Seeds (in vitro/in vivo/both) and (D) Others. 3rd Use intended for application in seeds: (A) Phytopathogenic organisms; (B) Pests; (C) Resistance; (D) Biostimulant and (E) Others.

The quali-quantitative analysis of the selected articles was performed using the bibliometric indicators, with the discrimination of the following items: title, year of publication, journal, country of research, topic in agriculture, application, and application in seeds. The data were subjected to analysis in Rstudio version 2020, and graphs and word clouds were created.

Regarding the year of publication, the highest frequency was verified in 2019, followed by 2018. A great number of publications was observed until August 2020, with the prediction that, until the end of the year, they would outnumber those of 2019. On the other hand, between years 2010 and 2017, a stability was observed in relation to the number of articles published on this topic (Figure 1).

Figure 1
Number of articles published on the use of plant extracts in agriculture and application in seeds between January 2010 and August 2020, indexed at the Web of Science.

In recent years, one of the main demands of the population and a challenge faced by the agricultural sector is the need for safer and more sustainable approaches regarding the management of agricultural production systems in view of the harmful effects generated by the high toxicity and low biodegradability of diverse synthetic agrochemicals used (BOITEUX et al., 2019BOITEUX, J. et al. ECo-friendly postharvest protection: Larrea cuneifolia-nades extract against Botrytis cinerea. Revista de la Facultad de Ciencias Agrarias UNCuyo, 51(2), 427-437, 2019. Available from: <Available from: http://revistas.uncuyo.edu.ar/ojs/index.php/RFCA/article/view/2729 >. Accessed: Oct. 12, 2020.
http://revistas.uncuyo.edu.ar/ojs/index....
). An increase in the visibility of researches using plant extracts in agriculture is then perceived, demonstrating potential alternatives for application in production systems (KHAN et al., 2020KHAN, I. A. et al. Effect of different herbicides, plant extracts and mulches on yield and yield components of maize. Planta Daninha, [s.l.], v.38, 2020. Available from: <Available from: https://doi.org/10.1590/s0100-83582020380100028 >. Accessed: Oct. 12, 2020. doi: 10.1590/s0100-83582020380100028.
https://doi.org/10.1590/s0100-8358202038...
; CONFORTIN et al., 2019CONFORTIN, T. C. et al. Extracts from Lupinus albescens: antioxidant power and antifungal activity in vitro against phytopathogenic fungi. Environmental Technology (United Kingdom), [s.l.], v.40, n.13, p.1668-1675, 2019. Available from: <Available from: https://doi.org/10.1080/09593330.2018.1427800 >. Accessed: Oct. 12, 2020. doi: 10.1080/09593330.2018.1427800.
https://doi.org/10.1080/09593330.2018.14...
).

A total of 133 journals were identified publishing articles on the use of plant extracts in agriculture, with Crop Protection presenting the highest frequency of publications, followed by the journals European Journal of Plant Pathology, Pakistan Journal of Botany and Semina-Ciências Agrárias (Figure 2).

Figure 2
Main journals disseminating publications on the potential use of plant extracts in agriculture and application in seeds between January 2010 and August 2020, indexed at the Web of Science.

These journals present international impact and visibility; nevertheless, 13.9% were Brazilian journals and 86.06% were journals published in other countries. The national journals present major importance not only in the dissemination of national studies, since they connect a great number of studies generated and developed in other countries on the topic of plant extracts in agriculture and in the treatment of seeds.

It was observed that, among the countries which presented the greatest frequency of publications referring to the potentialities of the use of plant extracts in agriculture and application in seeds over the past ten years are Brazil (20.4%), India (11.44%) and Pakistan (9.4%) (Figure 3A and 3B). In Latin America, Brazil leads the ranking of investments in agricultural research exactly for having a well-defined vocation and agricultural profile, with many Universities and Research Centers exclusively dedicated to scientific development in the field of Agrarian Sciences.

Figure 3
(A) Percentage of articles published per country, about the potential use of plant extracts in agriculture and application in seeds, between January 2010 and August 2020, indexed at the Web of Science; (B) Main countries in the publication of articles on the potential use of plant extracts in agriculture and application in seeds.

The Brazilian productive leadership is related, primarily, to technological aspects, but also to the edaphoclimatic characteristics and; especially, to the availability of production fields. Nonetheless, a great part of this production is still based on the use of pesticides (SOARES et al., 2019SOARES, M. A. et al. Botanical insecticide and natural enemies: a potential combination for pest management against Tuta absoluta. Journal of Pest Science, [s.l.], v.92, no.4, p.1445, 2019. Available from: <Available from: https://doi.org/10.1007/s10340-019-01102-y >. Accessed: Oct. 12, 2020. doi: 10.1007/s10340-019-01102-y.
https://doi.org/10.1007/s10340-019-01102...
), boosting investments in research on alternative technologies and ecological strategies aimed at agriculture (PEREIRA et al., 2018PEREIRA, A. J. et al. Control of Brevicoryne brassicae (Hemiptera: Aphididae) with extracts of Agave americana var. Marginata Trel. in Brassica oleracea crops. Annals of Applied Biology, [s.l.], v.174, no.1, p.14-19, 2018. Available from: <Available from: https://doi.org/10.1111/aab.12471 >. Accessed: Oct. 12, 2020. doi: 10.1111/aab.12471.
https://doi.org/10.1111/aab.12471...
).

Another relevant factor is that in Brazil, great part of food production is derived from family agriculture or of small rural producers, who in turn have also practiced an agroecological-based agriculture (PEREIRA et al., 2018PEREIRA, A. J. et al. Control of Brevicoryne brassicae (Hemiptera: Aphididae) with extracts of Agave americana var. Marginata Trel. in Brassica oleracea crops. Annals of Applied Biology, [s.l.], v.174, no.1, p.14-19, 2018. Available from: <Available from: https://doi.org/10.1111/aab.12471 >. Accessed: Oct. 12, 2020. doi: 10.1111/aab.12471.
https://doi.org/10.1111/aab.12471...
), using alternative sources for the control and management of pests and diseases, including the use of plant extracts (BARBOSA et al., 2015BARBOSA, W. F et al. Pesticides and reduced-risk insecticides, native bees and pantropical stingless bees: Pitfalls and perspectives. Pest Management Science, [s.l.], v.71, n.8, p.1049-1053, 2015. Available from: <Available from: https://doi.org/10.1002/ps.4025 >. Accessed: Oct. 12, 2020. doi: 10.1002/ps.4025.
https://doi.org/10.1002/ps.4025...
).

A similar situation is observed in India and in Pakistan (LAKSHMEESHA et al., 2019LAKSHMEESHA, T.R. et al. Biofabrication of zinc oxide nanoparticles with Syzygium aromaticum flower buds extract and finding its novel application in controlling the growth and mycotoxins of Fusarium graminearum. Frontiers in Microbiology, 2019. Available from: <Available from: https://doi.org/10.3389/fmicb.2019.01244 >. Accessed: Oct. 12, 2020. doi: 10.3389/fmicb.2019.01244.
https://doi.org/10.3389/fmicb.2019.01244...
; KHAN et al., 2020KHAN, I. A. et al. Effect of different herbicides, plant extracts and mulches on yield and yield components of maize. Planta Daninha, [s.l.], v.38, 2020. Available from: <Available from: https://doi.org/10.1590/s0100-83582020380100028 >. Accessed: Oct. 12, 2020. doi: 10.1590/s0100-83582020380100028.
https://doi.org/10.1590/s0100-8358202038...
), with researches aiming the use of plant extracts in agriculture for the control of phytopathogenic organisms (MEENA et al., 2020MEENA, R. P. et al. Efficacy of fungicides and plant extracts against Alternaria alternata causing leaf blight of chandrasur (Lepidium sativum). Indian Journal of Agricultural Sciences , [s.l.], v.90, n.2, p.337-340, 2020. Available from: <Available from: https://www.researchgate.net/publication/339677934_Efficacy_of_fungicides_and_plant_extracts_against_Alternaria_alternata_causing_leaf_blight_of_chandrasur_Lepidium_sativum >. Accessed: Oct. 12, 2020. ISSN: 00195022.
https://www.researchgate.net/publication...
), insects (ZAKA et al., 2019ZAKA, S. M. et al. Toxic effects of some insecticides, herbicides, and plant essential oils against Tribolium confusum Jacquelin du val (Insecta: Coleoptera: Tenebrionidae). Saudi Journal of Biological Sciences, [s.l.], v.26, no.7, p.1767-1771, 2019. Available from: <Available from: https://doi.org/10.1016/j.sjbs.2018.05.012 >. Accessed: Oct. 12, 2020. doi: 10.1016/j.sjbs.2018.05.012.
https://doi.org/10.1016/j.sjbs.2018.05.0...
), treatment of seeds (ATRI & TIWANA, 2019ATRI, A.; TIWANA, U. S. Effect of seed treatment and foliar spray on leaf blight of fodder oat in Punjab. Phytoparasitica, 47, 723-731, 2019. Available from: <Available from: https://doi.org/10.1007/s12600-019-00758-7 >. Accessed: Oct. 12, 2020. doi: 10.1007/s12600-019-00758-7.
https://doi.org/10.1007/s12600-019-00758...
) and resistance induction (NARASIMHAMURTHY et al., 2019NARASIMHAMURTHY, K. et al. Elicitation of innate immunity in tomato by salicylic acid and Amomum nilgiricum against Ralstonia solanacearum. Biocatalysis and Agricultural Biotechnology, [s.l.], v.22, no July, p.101414, 2019. Available from: <Available from: https://doi.org/10.1016/j.bcab.2019.101414 >. Accessed: Oct. 12, 2020. doi: 10.1016/j.bcab.2019.101414.
https://doi.org/10.1016/j.bcab.2019.1014...
). Similar to what occurs in Brazil, family farming has great relevance in these two countries, making possible the use of alternative methods, such as plant extracts, for the management of the agroecosystem.

Considering the topic in agriculture, approximately 58.7% of the works explored the potential of plant extracts on phytopathogenic organisms, either in the control of diseases in plants, as the effects on the biology of fungi (SILVA et al., 2020SILVA, L. G.; ANDRADE, C. A.; BETTIOL, W. Biochar amendment increases soil microbial biomass and plant growth and suppresses Fusarium wilt in tomato. Tropical Plant Pathology , [S.L.], v.45, n.1, p.73-83, 2020. Available form: <Available form: http://dx.doi.org/10.1007/s40858-020-00332-1 >. Accessed: Oct. 12, 2020. doi: 10.1007/s40858-020-00332-1.
http://dx.doi.org/10.1007/s40858-020-003...
), of bacteria (KARABÜYÜK & AYSAN, 2019KARABÜYÜK, F.; AYSAN, Y. Antibacterial effects of some plant extracts against tomato bacterial speck disease caused by Pseudomonas syringae pv. tomato. Journal of Tekirdag Agricultural Faculty, 2019. Available from: <Available from: https://doi.org/10.33462/jotaf.529499 >. Accessed: Oct. 12, 2020. doi: 10.33462/jotaf.529499.
https://doi.org/10.33462/jotaf.529499...
) or nematodes (SAHAYARAJ et al., 2018SAHAYARAJ, K et al. Compatibility of entomopathogenic fungi with extracts of plants and commercial botanicals. African Journal of Biotechnology, [s.l.], v.10, no.6, p.933-938, 2018. Available from: <Available from: https://doi.org/10.5897/AJB10.252 >. Accessed: Oct. 12, 2020. doi: 10.5897/AJB10.252.
https://doi.org/10.5897/AJB10.252...
) (Figure 4A). Furthermore, it is observed that approximately 20% of the researches aimed the use for control, biology or repellency of insects (ZAKA et al., 2019ZAKA, S. M. et al. Toxic effects of some insecticides, herbicides, and plant essential oils against Tribolium confusum Jacquelin du val (Insecta: Coleoptera: Tenebrionidae). Saudi Journal of Biological Sciences, [s.l.], v.26, no.7, p.1767-1771, 2019. Available from: <Available from: https://doi.org/10.1016/j.sjbs.2018.05.012 >. Accessed: Oct. 12, 2020. doi: 10.1016/j.sjbs.2018.05.012.
https://doi.org/10.1016/j.sjbs.2018.05.0...
; OJO et al., 2020OJO, D. O. et al. Effects of Cleistopholis patens (Benth) extracts on cowpea seed beetle, Callosobruchus maculatus (Fab.) (Coleoptera: Chrysomelidae) infesting cowpea seeds in storage. International Journal of Tropical Insect Science, [s.l.], 2020. Available from: <Available from: https://doi.org/10.1007/s42690-020-00194-9 >. Accessed: Oct. 12, 2020. doi: 10.1007/s42690-020-00194-9.
https://doi.org/10.1007/s42690-020-00194...
), 12.43% of the researches explored the biostimulant effect in plants (COZZOLINO et al., 2020COZZOLINO, E. et al. Appraisal of biodegradable mulching films and vegetal-derived biostimulant application as eco-sustainable practices for enhancing lettuce crop performance and nutritive value. Agronomy , [s.l.], v.10, n.3, 2020. Available from: <Available from: https://doi.org/10.3390/agronomy10030427 >. Accessed: Oct. 12, 2020. doi: 10.3390/agronomy10030427.
https://doi.org/10.3390/agronomy10030427...
; MOLA et al., 2019MOLA, I. Di et al. Effect of vegetal- And seaweed extract-based biostimulants on agronomical and leaf quality traits of plastic tunnel-grown baby lettuce under four regimes of nitrogen fertilization. Agronomy , [s.l.], v.9, n.10, 2019. Available from: <Available from: https://doi.org/10.3390/agronomy9100571 >. Accessed: Oct. 12, 2020. doi: 10.3390/agronomy9100571.
https://doi.org/10.3390/agronomy9100571...
), demonstrating a potential use in agriculture still little explored.

Figure 4
(A) Main topics addressed in the articles on the application of plant extracts in agriculture; (B) Main applications of plant extracts in agriculture performed in the published articles and (C) Purpose applications of plant extracts in the treatment of seeds, in the articles published between January 2010 and August 2020 at the Web of Science.

Other two applications also discussed in some articles; although, in smaller volume, were the use of plant compounds as a triggering source of natural resistance-inducing genes against phytopathogenic organisms, resistance to insects and abiotic factors (6.46%) (ALSAHLI et al., 2018ALSAHLI, A. A. et al. Extract from Curcuma longa L. triggers the sunflower immune system and induces defence-related genes against Fusarium root rot. Phytopathologia Mediterranea, [s.l.], v.57, n.1, p.26-36, 2018. Available from:: <Available from:: https://doi.org/10.14601/Phytopathol_Mediterr-21176 >. Accessed: Oct. 09, 2020. doi: 10.14601/Phytopathol_Mediterr-21176.
https://doi.org/10.14601/Phytopathol_Med...
) and herbicide or allelopathic effect on plant control (4.97%) (FINDURA et al., 2020FINDURA, P.. et al. Evaluation of the effects of allelopathic aqueous plant extracts, as potential preparations for seed dressing, on the modulation of cauliflower seed germination. Agriculture, [s.l.], v.10, n.4, 2020. Available from: <Available from: https://doi.org/10.3390/agriculture10040122 >. Accessed: Oct. 12, 2020. doi: 10.3390/agriculture10040122.
https://doi.org/10.3390/agriculture10040...
), especially in the management of spontaneous plants in horticulture (CASER et al., 2020CASER, M. et al. Activity of Ailanthus altissima (Mill.) swingle extract as a potential bioherbicide for sustainable weed management in horticulture. Agronomy, [s.l.], v.10, n.7, p.965, 2020. Available from: <Available from: https://doi.org/10.3390/agronomy10070965 >. Accessed: Oct. 12, 2020. doi: 10.3390/agronomy10070965.
https://doi.org/10.3390/agronomy10070965...
).

Considering the application in agriculture, 34.84% of the studies evaluated the potential of the application directly in plants, being 23.9% under conditions in vivo and 10.9% under conditions in vivo and in vitro (Figure 4B). This evidenced the importance of understanding the direct application of plant compounds as potential alternative sources in agriculture for interactions plant/plant extracts and plant/plant extracts/phytopathogenic organisms. AL-MOHMADI and AL-ANI (2019AL-MOHMADI, S. Y. A.; AL-ANI, M. H. I. Effect of spraying with different concentration of licorice extract and plant densities in growth and yield of sorghum bicolor l. Iraqi Journal of Agricultural sciences, [s.l.], v.50, n.6, p.1478-1485, 2019. Available from: <Available from: https://doi.org/10.36103/ijas.v50i6.835 >. Accessed: Oct. 09, 2020. doi: 10.36103/ijas.v50i6.835.
https://doi.org/10.36103/ijas.v50i6.835...
) evaluated the effect of direct leaf application of licorice (Glycyrrhiza glabra L.) extract on the growth and productivity of grains of Sorghum cv. Rabih, and reported an increase in plant height and in the productivity of grains in the period of Spring and Fall, when the sorghum plants were sown at high density.

The potential of the direct application of plant compounds has also been explored in vegetables, such as, for instance, in the study of JANG and KUK (2019JANG, S. J; KUK, Y. I. Growth promotion effects of plant extracts on various leafy vegetable crops. Horticultural Science and Technology, [s.l.], v.37, n.3, p.322-336, 2019. Available from: <Available from: https://doi.org/10.7235/HORT.20190033 >. Accessed: Oct. 12, 2020. doi: 10.7235/HORT.20190033.
https://doi.org/10.7235/HORT.20190033...
), who evaluated the effect on the growth of lettuce, broccoli, endive and kale subjected to leaf spraying of 31 plant extracts from agricultural materials. These authors verified an increment from 31 to 45% in the fresh weight of lettuce sprayed with aqueous extract of Allium tuberosum, aqueous extract of Glycine max (cvs. Daewon and Haepum) leaves, fermented, aqueous and ethanolic extract of soybean (cv. Daewon) stems at the concentration of 5% when compared to the application of urea at 0.6, 0.8 and 1%.

KARABÜYÜK & AYSAN (2019KARABÜYÜK, F.; AYSAN, Y. Antibacterial effects of some plant extracts against tomato bacterial speck disease caused by Pseudomonas syringae pv. tomato. Journal of Tekirdag Agricultural Faculty, 2019. Available from: <Available from: https://doi.org/10.33462/jotaf.529499 >. Accessed: Oct. 12, 2020. doi: 10.33462/jotaf.529499.
https://doi.org/10.33462/jotaf.529499...
) evaluated the effect of the treatment of seeds and the pulverization of tomato plants with twenty-nine plant extracts against the bacterial spot caused by Pseudomonas syringae pv.. Leaf pulverization at the concentration of 4.25 µl/ml of Allium sativum, Eucalyptus camaldulensis, Origanum onites and Zingiber officinale extracts reduced the incidence of the disease in 96-99% for all extracts, and when applied to the root, it was suppressed in 80-100% without promoting negative effects on the germination.

In a broader approach, SINGH et al. (2019SINGH, S. et al. Evaluation of components of IPM for basmati rice against rice root-knot nematode, Meloidogyne graminicola. Indian Journal of Agricultural Sciences , [s.l.], 2019. Available from: <Available from: https://www.cabdirect.org/cabdirect/abstract/20203531107 >. Accessed: Oct. 12, 2020. ISSN: 00195022.
https://www.cabdirect.org/cabdirect/abst...
) performed the treatment of seeds and plants of basmati rice with carbendazim, Trichoderma harzianum, Pseudomonas fluorescens and extract of Sesbania punicea (Cav.) Benth. against Meloidogyne graminicola, and verified that all treatments were efficient in the reduction of the population of nematodes; nevertheless, when applied in vivo, the extract of Sesbania increased the biomass of the rice plant in up to 68% in comparison with the other treatments. In addition to providing greater tolerance of the plant to M. graminicola, with a 37.7% reduction in the population of nematodes.

It is worth pointing out that, for other applications in agriculture, as well as for the topic in agriculture from the articles analyzed, there is a higher predominance of studies analyzing the direct effect in phytopathogenic organisms in vitro (OJO et al., 2020OJO, D. O. et al. Effects of Cleistopholis patens (Benth) extracts on cowpea seed beetle, Callosobruchus maculatus (Fab.) (Coleoptera: Chrysomelidae) infesting cowpea seeds in storage. International Journal of Tropical Insect Science, [s.l.], 2020. Available from: <Available from: https://doi.org/10.1007/s42690-020-00194-9 >. Accessed: Oct. 12, 2020. doi: 10.1007/s42690-020-00194-9.
https://doi.org/10.1007/s42690-020-00194...
). Furthermore, 3.98% of the researches evaluated the potential of application in the postharvest sector, especially as organic coating and treatment of fruits (KOLTZ et al., 2020KOLTZ, E. A. et al. Combining Brassica sachets and extracts with thermotherapy against postharvest green mold of orange. Scientia Horticulturae , [s.l.], v.268, no.December 2019, p.109389, 2020. Available from: <Available from: https://doi.org/10.1016/j.scienta.2020.109389 >. Accessed: Oct. 12, 2020. doi: 10.1016/j.scienta.2020.109389.
https://doi.org/10.1016/j.scienta.2020.1...
; BOITEUX et al., 2019BOITEUX, J. et al. ECo-friendly postharvest protection: Larrea cuneifolia-nades extract against Botrytis cinerea. Revista de la Facultad de Ciencias Agrarias UNCuyo, 51(2), 427-437, 2019. Available from: <Available from: http://revistas.uncuyo.edu.ar/ojs/index.php/RFCA/article/view/2729 >. Accessed: Oct. 12, 2020.
http://revistas.uncuyo.edu.ar/ojs/index....
; HERNÁNDEZ-GUERRERO et al., 2020HERNÁNDEZ-GUERRERO, S. E. et al. Identification of fungal pathogens of mango and soursop fruits using morphological and molecular tools and their control using papaya and soursop leaf and seed extracts. International Journal of Agronomy , [s.l.], v.2020, 2020. Available from: <Available from: https://doi.org/10.1155/2020/8962328 >. Accessed: Oct. 12, 2020. doi: 10.1155/2020/8962328.
https://doi.org/10.1155/2020/8962328...
).

The application of plant extracts in the treatment of seeds is also highlighted with 26.86% of the total of published articles (Figure 4B). Of them, as in the studies of application in plants, more than 68.5% have been performed under conditions in vitro + in vivo, 10.76% in vivo and 18.5% under condition in vitro.

Phytopathogenic organisms directly interfere in seed quality, affecting the initial development of seedlings and the final establishment of production fields (ROCHA et al., 2020ROCHA, C. H. D et al. Psidium cattleyanumessential oil to control plant pathogens in bean seeds. Revista Verde de Agroecologia e Desenvolvimento Sustentável, [s.l.], v.15, no.1, p.14-19, 2020. Available from: <Available from: https://doi.org/10.18378/rvads.v15i1.7365 >. Accessed: Oct. 12, 2020. doi: 10.18378/rvads.v15i1.7365.
https://doi.org/10.18378/rvads.v15i1.736...
). Additionally, great part of the diseases that occur in adult plants derived from causal agents associated with seeds, making preventive management extremely important. This is reflected on the highest percentage of articles with this purpose (69.29%) among the total of researches that address the use of plant extracts in seeds (Figure 4C). Other applications of the plant extracts in seeds include the use as biostimulant (26.92%), in resistance induction (5.76%) and in pest control (3.84%).

Regarding the management of fungi associated with the seeds, CHANDEL and KUMAR (2017CHANDEL, S.; KUMAR, V. Effect of plant extracts as pre-storage seed treatment on storage fungi, germination percentage and seedling vigour of pea (Pisum sativum). Indian Journal of Agricultural Sciences, [s.l.], v.87, n.11, p.1476-1481, 2017. Available from: <Available from: http://epubs.icar.org.in/.../75703 >. Accessed: Oct. 12, 2020. ISSN: 00195022.
http://epubs.icar.org.in/.../75703...
) studied the effect of eleven plant extracts on rot fungi of storage Aspergiluss sp., and of field Alternaria alternata, A. solani, Phoma sp and Fusarium spp. and on the parameters of germination and vigor in pea (Pisum sativa) seeds and seedlings. The use of Vitex negundo and Melia azadiractha extracts at the concentration of 30% presented minimum rot of 1.94% compared to the untreated seeds (13.84%), with maximum germination superior to 96.41% for extracts of Mentha piperata and Tagetes erecta.

Considering that the first signs of defense in the plants are triggered still in the seed, by the activation of preventive local and systemic defense mechanisms in plants against pathogens, ALSAHLI et al. (2018ALSAHLI, A. A. et al. Extract from Curcuma longa L. triggers the sunflower immune system and induces defence-related genes against Fusarium root rot. Phytopathologia Mediterranea, [s.l.], v.57, n.1, p.26-36, 2018. Available from:: <Available from:: https://doi.org/10.14601/Phytopathol_Mediterr-21176 >. Accessed: Oct. 09, 2020. doi: 10.14601/Phytopathol_Mediterr-21176.
https://doi.org/10.14601/Phytopathol_Med...
) verified higher enzyme activity of guaiacol peroxidase (POX), phenylalanine ammonia lyase (PAL) and genes coding for defense in sunflower plants after the treatment of seeds with Curcuma longa L. extracts at the concentration of 10% against Fusarium solani. CHANDRASHEKHARA, S et al. (2010CHANDRASHEKHARA, S. et al. Seed treatment with aqueous extract of Viscum album induces resistance to pearl millet downy mildew pathogen. Journal of Plant Interactions, [s.l.], v.5, n.4, p.283-291, 2010. Available from: <Available from: https://doi.org/10.1080/17429140903556539 >. Accessed: Oct. 12, 2020. doi: 10.1080/17429140903556539.
https://doi.org/10.1080/1742914090355653...
) verified significant increases in the parameters of quality and induction of resistance to mildew (Sclerospora graminicola [Sacc.] Schroe) in millet seeds (Pennisetum galaucum R. Br.) subjected to the treatment with extracts of Azadirachta indica, Argemone mexicana, Commiphora caudata, Mentha piperita, Emblica officinales and Viscum album.

The occurrence of pests in seeds during storage is another factor of great relevance for the agricultural sector. OJO et al. (2020OJO, D. O. et al. Effects of Cleistopholis patens (Benth) extracts on cowpea seed beetle, Callosobruchus maculatus (Fab.) (Coleoptera: Chrysomelidae) infesting cowpea seeds in storage. International Journal of Tropical Insect Science, [s.l.], 2020. Available from: <Available from: https://doi.org/10.1007/s42690-020-00194-9 >. Accessed: Oct. 12, 2020. doi: 10.1007/s42690-020-00194-9.
https://doi.org/10.1007/s42690-020-00194...
) evaluated the efficiency of root and stem extracts of Cleistopholis patens (Benth) in the protection of cowpea seeds against infestation by Callosobruchus maculatus during storage and they reported mortality of 77.05% of the insects for a dose of 5% in a period of 24 hours after application for stem extract, at the same time that there were 50 and 95% of mortality of the insects subjected to root extract, as well as a reduction in oviposition and emergence of adults, at the same concentration.

Considering the various applications that have been explored in the studies with plant extracts, the use in the treatment of agricultural soils and potential natural sources of nitrification inhibitors can also be highlighted (MUÑOZ et al., 2014MUÑOZ, C et al. Evaluation of biochar-plant extracts complexes on soil nitrogen dynamics. Journal of Biobased Materials and Bioenergy, [s.l.], v.8, no.3, p.377-385, 2014. Available from: <Available from: https://doi.org/10.1166/jbmb.2014.1448 >. Accessed: Oct. 12, 2020. doi: 10.1166/jbmb.2014.1448.
https://doi.org/10.1166/jbmb.2014.1448...
).

Among the main species and genera of plants used with potentialities of application in agriculture and in the treatment of seeds, Azadirachta indica A. Juss. (11.94%), Allium sativum L. (7.46%) and Eucalyptus sp. (4.97%) were the most frequently studied (Table 1).

Table 1
Main species/genera used in studies on the potential of application of plant extracts in agriculture and in the treatment of seeds, in the articles published between January 4th 2010 and August 2020 at the Web of Science.

The genera Acacia sp., Brassica sp. and the species Melia azedarach L., Rosmarinus officinalis L. and Zingiber officinale R. were identified in 2.48% of the analyzed researches (Table 1 and 2), whereas the genera Citrus sp., Piper sp., Capsicum sp., Cinnamomum sp. and the species Punica granatum L., Ocimum basilicum L., Nicotiana tabacum L. and Carica papaya L. were represented in 1.99% of the studies with applications in agriculture and in the treatments of seeds (Table 2).

Table 2
Species/genera used in studies on the potential of application of plant extracts in agriculture and in the treatment of seeds, in the articles published between January 4th 2010 and August 2020 at the Web of Science.

The data indicated an increasing trend in the search for more sustainable strategies and with potential application in agriculture for different purposes, especially in the treatment of seeds. Among these strategies, plant extracts are indicated as viable alternatives to conventional treatments, promoting the rise in quality and reduction in the costs of the agricultural cultivations, minimizing the impacts in the ecosystems. Furthermore, it is important to highlight that the proper use of plant extracts will depend on the methodology for making the extracts, the use of appropriate concentration and the number of applications for each expected objective.

CONCLUSION:

The use of plant extracts in agriculture has a potential, demonstrated by the high number of publications, especially in the years 2018, 2019 and 2020, with Brazil being the country with the highest production of research directed to this field of study. Control of phytopathogenic organisms, effect in insects, biostimulant effect, induction of resistance and herbicide effect have been the main topics explored for use in agriculture. The direct application of plant extracts is mainly centered in plants and seeds and, for the application in seeds, the focus is the control of phytopathogenic organisms and biostimulant effect.

ACKNOWLEDGEMENTS

The present research was performed with support of the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brazil (CAPES)- Finance Code 001.

REFERENCES

  • CR-2021-0245.R1

Edited by

Editors: Leandro Souza da Silva
Nelson Barbosa Machado-Neto

Publication Dates

  • Publication in this collection
    15 Oct 2021
  • Date of issue
    2022

History

  • Received
    26 Mar 2021
  • Accepted
    07 July 2021
  • Reviewed
    24 Aug 2021
Universidade Federal de Santa Maria Universidade Federal de Santa Maria, Centro de Ciências Rurais , 97105-900 Santa Maria RS Brazil , Tel.: +55 55 3220-8698 , Fax: +55 55 3220-8695 - Santa Maria - RS - Brazil
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