Evidence for photolytic and microbial degradation processes in the dissipation of leptospermone, a natural β-triketone herbicide

Abstract

Bioherbicides appear as an ecofriendly alternative to synthetic herbicides, generally used for weed management, because they are supposed to have low side on human health and ecosystems. In this context, our work aims to study abiotic (i.e., photolysis) and biotic (i.e,. biodegradation) processes involved in the fate of leptospermone, a natural β-triketone herbicide, by combining chemical and microbiological approaches. Under controlled conditions, the photolysis of leptospermone was sensitive to pH. Leptospermone has a half-life of 72 h under simulated solar light irradiations. Several transformation products, including hydroxy-leptospermone, were identified. For the first time, a bacterial strain able to degrade leptospermone was isolated from an arable soil. Based on its 16S ribosomal RNA (rRNA) gene sequence, it was affiliated to the Methylophilus group and was accordingly named as Methylophilus sp. LS1. Interestingly, we report that the abundance of OTUs, similar to the 16S rRNA gene sequence of Methylophilus sp. LS1, was strongly increased in soil treated with leptospermone. The leptospermone was completely dissipated by this bacteria, with a half-life time of 6 days, allowing concomitantly its growth. Hydroxy-leptospermone was identified in the bacterial culture as a major transformation product, allowing us to propose a pathway of transformation of leptospermone including both abiotic and biotic processes.

Screening and efficacy evaluation of antagonistic fungi against Phytophthora infestans and combination with arbuscular mycorrhizal fungi for biocontrol of late blight in potato

“…reported that roflamycoin, an antifungal metabolite produced by Streptomyces roseoflavus, was degraded under the sunlight as well as under fluorescent light. Photo-oxidation of natural compounds by UV, including biocontrol products, has been reported by Ahonsi et al (2006) and Romdhane et al (2018). Plant parameters may also be involved in the differences observed between both experiments.…”

Óleos essenciais de Leptospermum scoparium, Origanum vulgare e Litsea cubeba sobre Rhipicephalus microplus: atividade acaricida, influência dos solventes e busca por frações com maior bioatividade

“…Com a grande comercialização desses compostos como herbicidas, vários estudos já foram realizados para avaliar o impacto ecotoxicológico de β-tricetonas naturais e sintéticas na diversidade da comunidade bacteriana, sendo demonstrado que a dissipação da leptospermona e sulcotriona ocorre dentro de 45 dias no solo (CALVAYRAC et al, 2012;ROMDHANE et al, 2016;ROMDHANE et al, 2019). Nesse mesmo sentido, Romdhane et al ( 2019) afirmam também que a leptospermona e sulcotriona apresentaram meia-vida semelhante quando usadas em dose agronômica, enquanto que ao usar uma dose mais alta, a leptospermona apresentou uma meia-vida mais curta que sulcotriona, confirmando que um composto natural é mais facilmente biodegradável do que um sintético (ROMDHANE et al, 2018).…”