RESUMO

Research and commercial production of bioherbicides occur to a lesser extent compared to bioinsecticides and biofungicides. In order to contribute to developing new bioherbicides with low environmental impact, this study aimed to increase the phytotoxicity of metabolites of the fungus Mycoleptodiscus indicus UFSM 54 by optimizing solid and submerged fermentation and evaluate the ecotoxicological effects on earthworms (Eisenia andrei). The Plackett-Burman and central composite rotatable designs were used to optimize metabolite phytotoxicity. The variables optimized in the fermentation were temperature, agitation, pH, water volume in the culture medium, glucose concentration, and yeast extract. The fungus was grown on sugarcane bagasse substrate, and its metabolites were applied to detached Cucumis sativus, Conyza sp., and Sorghum bicolor leaves and used in an avoidance test and acute exposure to earthworms. Metabolite phytotoxicity in submerged fermentation was optimized at 35 °C, 50 rpm, and 1.5 g l-1 of glucose and in solid fermentation at 30-37 °C and in 14-32 ml of water. The metabolites severely damaged germination, initial growth, and leaves of the three plants, and at the doses tested (maximum of 113.92 ml kg-1), the metabolites of M. indicus UFSM 54 were not toxic to earthworms.

Assuntos

RESUMO

Weeds represent one of the most challenging biotic factors for the agricultural sector, responsible for causing significant losses in important agricultural crops. Traditional herbicides have managed to keep weeds at bay, but overuse has resulted in negative environmental and toxicological impacts, including the increase of herbicide-resistant species. Within this context, the use of biologically derived (bio-)herbicides represents a promising solution because they are able to provide the desired phytotoxic effects while causing less toxic environmental damage. In recent years, bioactive secondary metabolites, in particular those bio-synthesized by endophytic fungi, have been shown to be promising sources of novel compounds that can be exploited in agriculture, including their use in weed control. Endophytic fungi have the ability to produce volatile and nonvolatile compounds with broad phytotoxic activity. In addition, as a result of the beneficial relationships they establish with their host plants, they are part of the colonization mechanism and can provide protection for their hosts. As such, endophytic fungi can be exploited as bioherbicides and as research tools. In this review, we cover 100 nonvolatile secondary metabolites with phytotoxic activity and more than 20 volatile organic compounds in a mixture, produced by 28 isolates of endophytic fungi from 21 host plant families, collected in 8 countries. This information can form the basis for the application of endophytic fungal compounds in weed control. KEY POINTS: • Endophytic fungi produce a wide variety of secondary metabolites with unique and complex structures. • Fungal endophytes produce volatile and nonvolatile compounds with promising phytotoxic activity. • Endophytic fungi are a promising source of useful bioherbicides.

Assuntos

RESUMO

The application of glyphosate to coffee crops can cause injuries to plants. Fertiactyl® foliar fertilizer reduces injuries when mixed with glyphosate; however, it is important to establish which mechanisms are responsible for this protective action. This study aimed to evaluate the absorption and translocation of glyphosate applied separately and in mixture with Fertiactyl® in coffee seedlings. Absorption and translocation were performed with 14C-glyphosate applied separately and in mixture with Fertiactyl® at 0, 6, 12, 24, 48, 96, and 144 hours after application (HAA). Most of the 14C-glyphosate applied to coffee seedlings was not absorbed. The 14C-glyphosate applied separately had a higher absorption by coffee seedlings (6.5%) than in a mixture with Fertiactyl® (2.7%) at 144 HAA. The maximum translocation of the 14C-glyphosate applied separately was 0.69% at 81.2 HAA and in mixture with Fertiactyl® was 0.41% at 41.2 HAA. The treated leaves retained a higher percentage of 14C-glyphosate when applied separately (5.6% at 144 HAA) than in a mixture with Fertiactyl® (2.2% at 144 HAA). Low translocation (<1%) for the rest of the plant shoots was observed both for the 14C-glyphosate applied separately and in combination with Fertiactyl®. Therefore, Fertiactyl® decreased the absorption and translocation of 14C-glyphosate in coffee seedlings.

Assuntos

RESUMO

This work aimed the evaluation of the selectivity of nicosulfuron and foramsulfuron + iodosulfuron methyl sodium herbicides to different Agroeste corn hybrids (AS 1545, AS 1548, S2 709, AS 32, AS 3466 and AS 1533). The trials were arranged in a randomized complete block design with 7 treatments and 5 replications for each hybrid. Herbicides rates (in g i.a. ha-1) were: foramsulfuron + iodosulfuron methyl sodium: 22.5 + 1.5; 45.0 + 3.0 and 90.0 + 6.0 and nicosulfuron: 30, 60 and 90. Phytotoxicity and the parameters relative to the components of crop production and yield were evaluated. The corn cultivars had differential tolerance to the herbicides; S2 709 hybrid had its yield decreased when foramsulfuron + iodosulfuron methyl sodium was applied at 45.0 + 3.0 and 90.0 + 6.0 g i.a. ha-1; the AS 1533 hybrid had its yield reduced when foramsulfuron + iodosulfuron methyl sodium and nicosulfuron were applied at 90.0 + 6.0 g i.a. ha-1 and 120.0 g i.a. ha-1 respectively.

O objetivo do presente trabalho foi avaliar a seletividade dos herbicidas nicosulfuron e a mistura de foramsulfuron + iodosulfuron methyl sodium a diferentes híbridos de milho Agroeste (AS 1545, AS 1548, S2 709, AS 32, AS 3466 e AS 1533). O delineamento experimental utilizado foi o de blocos ao acaso, com 7 tratamentos e 5 repetições para cada híbrido. As doses dos herbicidas (em g i.a. ha -1) foram: foramsulfuron + iodosulfuron methyl sodium: 22,5 + 1,5; 45,0 + 3,0 e 90,0 + 6,0 e nicosulfuron: 30, 60 e 90. Avaliou-se a fitotoxicidade, além de parâmetros relativos aos componentes de produção da cultura e produtividade. Os cultivares de milho testados possuem tolerância diferencial aos herbicidas utilizados; o híbrido S2 709 teve sua produtividade diminuída quando o herbicida foramsulfuron + iodosulfuron methyl sodium foi aplicado nas doses de 45,0 + 3,0 e 90,0 + 6,0 g i.a. ha -1; o híbrido AS 1533 teve sua produtividade reduzida quando os herbicidas foramsulfuron + iodosulfuron methyl sodium e nicosulfuron foram aplicados nas doses de 90,0 + 6,0 g i.a. ha-1 e 120 g i.a. ha -1, respectivamente.   

RESUMO

This work aimed the evaluation of the selectivity of nicosulfuron and foramsulfuron + iodosulfuron methyl sodium herbicides to different Agroeste corn hybrids (AS 1545, AS 1548, S2 709, AS 32, AS 3466 and AS 1533). The trials were arranged in a randomized complete block design with 7 treatments and 5 replications for each hybrid. Herbicides rates (in g i.a. ha-1) were: foramsulfuron + iodosulfuron methyl sodium: 22.5 + 1.5; 45.0 + 3.0 and 90.0 + 6.0 and nicosulfuron: 30, 60 and 90. Phytotoxicity and the parameters relative to the components of crop production and yield were evaluated. The corn cultivars had differential tolerance to the herbicides; S2 709 hybrid had its yield decreased when foramsulfuron + iodosulfuron methyl sodium was applied at 45.0 + 3.0 and 90.0 + 6.0 g i.a. ha-1; the AS 1533 hybrid had its yield reduced when foramsulfuron + iodosulfuron methyl sodium and nicosulfuron were applied at 90.0 + 6.0 g i.a. ha-1 and 120.0 g i.a. ha-1 respectively.

O objetivo do presente trabalho foi avaliar a seletividade dos herbicidas nicosulfuron e a mistura de foramsulfuron + iodosulfuron methyl sodium a diferentes híbridos de milho Agroeste (AS 1545, AS 1548, S2 709, AS 32, AS 3466 e AS 1533). O delineamento experimental utilizado foi o de blocos ao acaso, com 7 tratamentos e 5 repetições para cada híbrido. As doses dos herbicidas (em g i.a. ha -1) foram: foramsulfuron + iodosulfuron methyl sodium: 22,5 + 1,5; 45,0 + 3,0 e 90,0 + 6,0 e nicosulfuron: 30, 60 e 90. Avaliou-se a fitotoxicidade, além de parâmetros relativos aos componentes de produção da cultura e produtividade. Os cultivares de milho testados possuem tolerância diferencial aos herbicidas utilizados; o híbrido S2 709 teve sua produtividade diminuída quando o herbicida foramsulfuron + iodosulfuron methyl sodium foi aplicado nas doses de 45,0 + 3,0 e 90,0 + 6,0 g i.a. ha -1; o híbrido AS 1533 teve sua produtividade reduzida quando os herbicidas foramsulfuron + iodosulfuron methyl sodium e nicosulfuron foram aplicados nas doses de 90,0 + 6,0 g i.a. ha-1 e 120 g i.a. ha -1, respectivamente.