Allelopatic effects of Waltheria indica L.: Biocontrol potential in ecological restoration

Bruno Santos Francisco,Rafael Paranhos Martins,Bruna Santos Teração,Raquel Passaretti,Fatima Conceição Márquez Piña-Rodrigues,Emerson Viveiros,Felipe Bueno Dutra,Larissa Rocha,José Mauro Santana Da Silva,Lausanne Soraya De Almeida

doi:10.33448/rsd-v10i13.21263

Bruno Santos Francisco, Rafael Paranhos Martins + Show 8 more

Open Access

https://doi.org/10.33448/rsd-v10i13.21263

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Abstract

In Brazil, most degraded areas are occupied by exotic and invasive species, which require alternatives for their management. We evaluated the allelopathic effects of Waltheria indica in the laboratory from aqueous extracts of leaves and roots on the germination of the species Lactuca sativa L. (lettuce), Urochloa brizantha (Hochst. ex A.Rich.) RDWebster (brachiaria) and Handroanthus chrysotrichus (Mart. ex DC.) Mattos (yellow Ipe). We collected adult one-year-old Waltheria indica shrubs in ecological restoration areas by direct seeding. We used two treatments with aqueous extracts of leaves and roots and a control without extract, with ten repetitions of 10 seeds per treatment, totaling 600 seeds per test species. Germination and use of tetrazolium assays to evaluate the potential respiratory activity of the roots were used. The aqueous extract of W.indica leaves affected the number of germinated seeds of all test species, while the aqueous extract of roots affected only L. sativa and H. chrysotrichus. There were no significant differences between treatments (leaf and root extracts) in species germination. The aqueous extracts of Waltheria indica leaves and roots affected germination and cellular respiration of the studied species, mainly in Lactuca sativa. The identification of W. indica allelopathic compounds may be an initial step so that in the future new bioherbicides are produced from extracts of this species, or even that its seeds can be sown together with non-sensitive native species, aiming for control of exotic species in ecological restoration projects.

Highlights

Brazil is one of the five countries with the largest hotspot area in the world (Brancalion et al, 2019)
There is a significant reduction in the occurrence of brachiaria grass (Urochloa spp.), considered an invasive exotic species; native species appear to be growing normally. Based on these field observations, this study aimed to verify the allelopathic activity of aqueous extracts of leaves and roots of the species Waltheria indica on the germination of the species Lactuca sativa L., Urochloa brizantha (Hochst. ex A.Rich.) R.D.Webster, and Handroanthus chrysotrichus (Mart. ex DC.) Mattos
The aqueous extract of Waltheria indica leaves was found to affect the number of germinated seeds of all test species (Figure 1a), while the aqueous extract of W. indica roots affected only L. sativa and H. chrysotrichus (Figure 1b)

Summary

Introduction

Brazil is one of the five countries with the largest hotspot area in the world (Brancalion et al, 2019). Most areas intended for ecological restoration are highly uncharacterized from the point of view of the composition of native species, represented mostly by degraded pastures (Rodrigues et al, 2009). Many of these areas to be restored have strong coverage of exotic and invasive plants that end up hindering the establishment of native species, becoming a major cause of failure in ecological restoration (Cornish & Burgin, 2005; García-Orth & Martinéz-Ramos, 2011). Control can be achieved by applying preventive, biological, physical, and chemical methods, and integration between different methods is the most common and effective way to control exotic and invasive weeds (Silva et al, 2009; Brighenti and Oliveira, 2011; Passareti et al, 2020; Di Sacco et al, 2021)

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