Metagenomic analysis reveals mechanisms of atrazine biodegradation promoted by tree species.

Metagenomics has provided the discovery of genes and metabolic pathways involved in the degradation of xenobiotics. Some microorganisms can metabolize these compounds, potentiating phytoremediation in association with plant. This study aimed to study the metagenome and the occurrence of atrazine degradation genes in rhizospheric soils of the phytoremediation species Inga striata and Caesalphinea ferrea. The genera of microorganisms predominant in the rhizospheric soils of I. striata and C. ferrea were Mycobacterium, Conexibacter, Bradyrhizobium, Solirubrobacter, Rhodoplanes, Streptomyces, Geothrix, Gaiella, Nitrospira, and Haliangium. The atzD, atzE, and atzF genes were detected in the rhizospheric soils of I. striata and atzE and atzF in the rhizospheric soils of C. ferrea. The rhizodegradation by both tree species accelerates the degradation of atrazine residues, eliminating toxic effects on plants highly sensitive to this herbicide. This is the first report for the species Agrobacterium rhizogenes and Candidatus Muproteobacteria bacterium and Micromonospora genera as atrazine degraders.

Phytoremediation by Eremanthus crotonoides and Inga striata decay atrazine and clomazone residues in the soil.

The atrazine and clomazone molecules have potential to contaminate environments, especially water resources. Phytoremediation decontamination can prevent or reduce the quantity of these products reaching watercourses. The objective was to evaluate the remedial potential and the physiological sensitivity of Eremanthus crotonoides (DC.) Sch. Bip and Inga striata Benth to atrazine and clomazone in soils contaminated with 0.0, 0.5, 1.0 and 2.0 times the recommended commercial dose of these herbicides. The photosynthesis, CO2 consumed stomatal conductance and transpiration of E. crotonoides and I. striata, in soils contaminated with atrazine and clomazone, were evaluated. The herbicide residues were detected by ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) 30 days after the last herbicide application. The photosynthesis rate and CO2 consumed by E. crotonoides and I. striata were lower in soils contaminated by atrazine and clomazone. Inga striata had lower stomatal conductance and transpiration in soil contaminated with clomazone. Eremanyhus crotonoides and I. striata reduced the residues of these herbicides. The atrazine and clomazone reduced the physiological variables of E. crotonoides and I. striata. These plants can be used to recover areas with residues of these herbicides, acting as filters that will decrease the amount of herbicides that would reach the watercourses.

Influence of 2,4-D residues on the soil microbial community and growth of tree species.

The 2,4-D (2,4-dichlorophenoxyacetic acid) has low half-life in the soil, but it is capable of altering the soil microbial community. The objective of this study was to evaluate the influence of 2,4-D residues on the structure of the soil microbial community and the growth of tree species. The tolerance and phytoremediation potential of tree species were evaluated. The microbial analysis was performed by T-RFLP. The 2,4-D herbicide reduced the plant height of K. lathrophyton, number of leaves of C. ferrea and K. lathrophyton and root dry matter allocation for C. brasiliense, I. striata, P. heptaphyllum, and T. guianensis. Cucumis sativus intoxication on soil contaminated with 2,4-D was not significant. The structure of Fungi community in the rhizospheric soils of C. ferrea was altered. The herbicide 2,4-D increased the diversity of Fungi in rhizospheric soils of P. heptahyllum and R. grandis. Most tree species were tolerant, and the evaluation time was sufficient to remedy 2,4-D. The structures of the microbial communities Archaea, Bacteria, and Fungi were little influenced by 2,4-D. The diversity of the Archaea domain was not affected, the diversity of the Bacteria in Inga striata decreased while the fungi increased in Protium heptaphyllum and Richeria grandis with 2,4-D.

Aspectos biológicos de Tetranychus ludeni Zacher, 1913 (Acari: Tetranychidae) alimentados com folhas de batata-doce pulverizadas com o 2,4-D / Biological aspects of Tetranychus ludeni Zacher, 1913 (Acari: Tetranychidae) fed on sweet potato leaves sprayed with 2,4-D

Batata-doce [Ipomoea batatas (L.) Lam.] apresenta grande versatilidade de usos no Brasil. Com a ampliação das áreas de cultivo, essa espécie estará sujeita à contaminação por herbicidas. Eventualmente, organismos não alvos podem ser expostos aos resíduos. O objetivo deste trabalho foi avaliar aspectos biológicos do ácaro Tetranychus ludeni alimentado com folhas de batata-doce pulverizadas com diferentes doses do herbicida 2,4-D. O experimento foi conduzido no Laboratório de Controle Biológico da Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM), em Diamantina, Minas Gerais. Foram utilizadas 175 fêmeas de T. ludeni e 6 doses de 2,4-D, em g.ha-1 (8,06; 20,15; 40,30; 80,60; 201,50; e 806,00), mais o tratamento-controle com água destilada. Adotou-se delineamento inteiramente casualizado, com sete tratamentos e cinco repetições, contendo cinco fêmeas de T. ludeni em cada repetição. Foram avaliados a mortalidade inicial do ácaro em 24 h, o número de ovos, as ninfas e a longevidade das fêmeas. Os dados foram submetidos à análise de variância, sendo as médias significativas analisadas pelo teste de Duncan. Observou-se que doses maiores desse herbicida podem aumentar a mortalidade e reduzir a longevidade das fêmeas de T. ludeni.(AU)

Sweet potato [Ipomoea batatas (L.) Lam.] presents great versatility of uses in Brazil. With the expansion of crop areas, this species is subject to contamination by herbicides. Eventually, non-target organisms can be exposed to residues . The aim of this study was to evaluate biological aspects of the mite Tetranychus ludeni fed on sweet potato leaves sprayed with different doses of the herbicide 2,4-D. The experiment was conducted at the Biological Control Laboratory of Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM), Diamantina, Minas Gerais, Brazil. Altogether, 175 females of T. ludeni and six doses of 2,4-D, in g.ha-1 (8.06, 20.15, 40.30, 80.60, 201.50, and 806,00) were used, plus the control done with distilled water. It was adopted a completely randomized design with seven treatments and five replications with five females each. Early mortality of T. ludeni (24 h), the number of eggs, nymphs and longevity of females were evaluated. Data were subjected to analysis of variance, being the significant mean analyzed by Duncan test. It was observed that high doses of the herbicide may increase the mortality and decrease longevity of females of T. ludeni.(AU)