Anderson Luis Nunes

Bioensaios para identificação de biótipos de Euphorbia heterophylla com resistência múltipla a inibidores da ALS e da PROTOX

Four bioassays were developed under greenhouse and laboratory conditions to identify Euphorbia heterophylla (EPHHL) biotypes with multiple resistance to PROTOX and ALS-inhibiting herbicides. In the greenhouse bioassays, plants of a susceptible (S) biotype and of two biotypes suspected of multiple resistance (#4 and #23) were sprayed using different levels of the herbicides imazethapyr and fomesafen. The laboratory bioassays consisted of a comparative test between biotypes S and #4, exposed to germination in imazethapyr and fomesafen solutions. Dose-response relationships were adjusted using logistic and polynomial models, respectively, for data obtained from greenhouse and laboratory bioassays. For biotype #4, the resistance factor (RF) to imazethapyr was above 24, while for biotype #23 it was 15. FR to fomesafen were, respectively, 62 and 39, for the same biotypes. In the laboratory bioassay, a period of 144 hours was sufficient to discriminate differencial growth response to imazethapyr and fomesafen levels between R and S biotypes. The results confirm that both greenhouse and laboratory tests with Petri dishes are appropriate methodologies to discriminate S and multiple R EPHHL biotypes.

Manejo integrado de plantas daninhas na cultura do milho

ABSTRACTINTEGRATED WEED MANAGEMENT IN MAIZE CULTIVATION Strategies to weed control in maize cultivation can be combined with chemical control to provide reductionof herbicide use. The aim of this work was to evaluate integrated management of plant row reduction, use of cornhybrids with contrasting morphological characteristics and reduction of herbicide levels to weed control. Theexperiment was carried out in a completely randomized block design with four replications in a 2 x 2 x 5 factorial.The first factor was maize hybrids such as Penta (super-early season maize with flatter vertical leaf angle) and Flash(super-early season maize and more upright vertical leaf angle). The second factor was maize row width (0.45 and0.90 m) and the third factor was the weed management system (hoeing, no hoeing, and atrazine + foramsulfurom +iodosulfuron at 3000+45+3, 2250+33.8+2.3 and 1500+22.5+1.5 g a.i. ha -1 ). It was evalued the plant height and verticalleaf of corn plants, the number and dry matter of weeds per area. The vertical leaf angle of corn plants becameflatter with the adoption of reduced row spacing, but other characteristics of corn plants were involved in theperformance of spacing. The use of the narrow row spacing did not contribute to reducing levels of herbicides, butnarrow row spacing benefits ony the weed management and grain yield of hybrid Flash.Key words: Zea mays, population arrangement, chemical control.(

Persistência do herbicida S-metolachlor associado ao glyphosate ou paraquat em plantio direto

A associacao de herbicidas dessecantes com efeito residual e comum entre os agricultores no manejo das areas sob semeadura direta. Essa pratica permite a dessecacao da cultura de inverno a ser utilizada como cobertura morta e, tambem, evita a reinfestacao por plantas daninhas na cultura de verao durante parte de seu ciclo. O objetivo do presente trabalho foi determinar a persistencia do herbicida residual S-metolachlor, quando associado com os herbicidas dessecantes glyphosate ou paraquat, aplicados sobre cobertura vegetal. O trabalho foi realizado a campo na Estacao Experimental Agronomica da Universidade Federal do Rio Grande do Sul (EEA/UFRGS) e em câmara de crescimento da Faculdade de Agronomia da UFRGS, sob Argissolo Vermelho distrofico tipico, contendo 28% de argila. O delineamento experimental foi de blocos casualizados, com quatro repeticoes, sendo os tratamentos distribuidos em parcelas subdivididas. Nas parcelas principais, foram alocados os herbicidas dessecantes paraquat (600 g ha-1) ou glyphosate (720 g ha-1) e, nas subparcelas, o herbicida residual S-metolachlor (2.800 g ha-1) associado ou aplicado sequencialmente aos herbicidas dessecantes, alem de uma testemunha contendo apenas herbicida dessecante, sem aplicacao do herbicida residual. A persistencia do S-metolachlor e maior na presenca do paraquat do que na do glyphosate. Nao ha diferenca entre aplicacao simultânea e sequencial dos herbicidas dessecantes e residuais.

Eficácia de controle de plantas daninhas e toxicidade ao milho da mistura de foramsulfuron e Iodosulfuron isoladamente ou em associação com atrazine e/ou clorpirifós

Two trials evaluated corn toxicity and weed control efficacy of the herbicides atrazine, foramsulfuron, and iodosulfuron and the insecticide chlorpyriphos applied at postemergence alone or in mixture. A randomized complete block design was used with four replications. In the first trial, the treatments (weed free throughout cultivation) were: atrazine (3000g ha-1 of a.i.); atrazine + clorpyriphos (3000 + 225g ha-1 of a.i.), atrazine + foramsulfuron + iodosulfuron + chlorpyriphos (2,250 + 15 + 1+ 225; 1,500 + 22.5 + 1.5 + 225 and 750 + 30 + 2 + 225 g ha-1 of a.i.); foramsulfuron+ iodosulfuron (45 + 3 g ha-1 of a.i.); foramsulfuron + iodosulfuron + chlorpyriphos (45 + 3 + 225 g ha1 of a.i.), and a check without herbicides. In the second trial, the same treatments were used, except for atrazine + foramsulfuron + iodosulfuron + chlorpyriphos (750 + 30 + 2 + 225 g ha-1 of a.i.), besides the same treatments above without weed cultivation. AG 3010 cultivar, a short-cycle double hybrid, tolerant to ALS herbicides, was used. During the 2002/2003 agricultural season, corn toxicity and grain yield were evaluated, while during 2003/2004 ,weed control efficacy was also evaluated. Atrazine alone or mixed with chlorpyriphos did not cause any toxicity to the corn plants. Chlorpiryphos + foramsulfuron and iodosulfuron association can increase corn plant injury. The inclusion of atrazine concomitant to foramsulfuron and iodosulfuron reduction allowed partial reduction of corn plant injury, maintaining BRAPL control and enhancing the level of EPHHL control.

Isolamento do gene ALS e investigação do mecanismo de resistência a herbicidas em Sagittaria montevidensis

California arrowhead (Sagittaria montevidensis Cham. & Schlecht) is an aquatic weed often found in rice paddy fields. Several biotypes of California arrowhead resistant to ALS-inhibiting herbicides were found in Brazil and in several rice fields worldwide. The objective of this study was to sequence the ALS gene of California arrowhead and to identify the occurrence of mutations related to target site insensitivity as the mechanism of herbicide resistance. The plant material consisted of seeds collected in rice paddy fields located in the state of Santa Catarina, Brazil. Nine pairs of primers were designed for the amplification of the domains C, A and D of the ALS gene. PCR reactions with four pairs of primers resulted in amplification of fragments with size close to expected, ranging from 360 to 393 nucleotides. These sequences showed high homology to the standard ALS gene Arabdopsis thaliana and rice having only three point mutations. One of these mutations was Pro 197 Phe that is related with herbicide resistance in several weeds. The sequences obtained indicated that the ALS gene evaluated was heterozygous. These results suggest the occurrence of insensitivity of the site of action as the mechanism of resistance to ALS-inhibitors herbicides in California arrowhead. The prevention and control of resistance to ALSinhibitors in California arrowhead should be based on the rotation of herbicides with different mechanisms of action.

Efeito de cargas aplicadas e profundidades de semeadura no desenvolvimento da cultura do feijão em sistema plantio direto

Dentre os fatores primordiais para a germinacao estao a umidade, a temperatura e a aeracao do solo. E importante citar que esses fatores sao diretamente influenciados pelo estado de compactacao do solo ao redor da semente. Objetivou-se, neste trabalho, estudar os efeitos da combinacao entre profundidades de semeadura e cargas aplicadas pela roda compactadora da semeadora-adubadora sobre o desenvolvimento da cultura do feijao, em sistema plantio direto. Foi utilizado o esquema fatorial no delineamento em blocos ao acaso, composto por doze tratamentos (tres profundidades de semeadura e quatro niveis de cargas aplicadas pela roda compactadora) e quatro repeticoes. Os resultados mostraram que a profundidade de semeadura influenciou, significativamente, o indice de velocidade de emergencia, os estandes inicial e final de plantas e o rendimento da cultura. As diferentes cargas aplicadas pela roda compactadora nao influenciaram significativamente as variaveis avaliadas.

Otimização da utilização de marcadores moleculares microssatélites e sua aplicação em estudos com plantas daninhas

Although more specific molecular markers have been developed, micro-satellite markers have a great potential to be used in weed science, because of their increasing availability to other species and quality of the information provided. The conventional use of micro-satellite molecular markers is laborious and expensive. The objective of this study was to describe the M13 tailed primer method for the optimization of the use of micro-satellite molecular markers, using as example, a study of hybrid identification between cultivated rice and red rice. Cultivated rice and red rice plants, as well as a hybrid originated from the artificial crossing of these plants were used as model. The M13 tailed primer method consists in the synthesis of the forward primer with the desired sequence and the addition of the sequence of a universal primer which corresponds to the tail. Amplification detection is performed on automated capillary electrophoresis equipment by using a labeled universal primer in the PCR. The system developed was effective in identifying the hybridization between the cultivated rice and red rice and it was useful, for example, in studies of gene flow of resistance to herbicides and introgression of traits related to the adaptation between these plants. The M13 tailed primer method allowed the use of several micro-satellite molecular markers from a single fluorescent marker and made multiplex analyses possible. The increased availability and knowledge of molecular techniques can provide better results in several studies related to weed species with little availability of specific molecular markers.

Interações entre herbicidas e protetores para o controle de capim-annoni em pastagem natural

The botanical similarity of the invasive weed Eragrostis plana Nees (South African lovegrass) difficult its selective control in natural pastures. The aim of this study was to evaluate the effect of the association between herbicides and safeners on the control of E. plana and on the selectivity to the natural pastures. Two experiments were conducted at field conditions in area of natural grassland of the Biome Pampa where several herbicides were evaluated in pre and post-emergence. A third experiment was carried out in greenhouse evaluating the herbicides glufosinate-ammonium and imazethapyr and the species E. plana and Paspalum notatum. In both experiments, the herbicides were evaluated isolated and in association with the safeners anhydride naphtalic, dietholate and fluxofenim. The field experiments indicated that the evaluated safeners did not increase E. plana control and native grassland selectively. The greenhouse experiment indicated the occurrence of synergism on E. plana for the herbicide glufosinate-ammonium in mixture with the safeners anhydride naphtalic, dietholate and fluxofenim. The different results in the field and greenhouse experiments are related to the plant stage and density. The use of herbicides in association with safeners indicated a potentiality for selective control of E. plana when applied to plants in the early stages of development.

Persistência do herbicida imazaquin associado ao glyphosate ou paraquat em plantio direto

The practice of associating non-selective and residual herbicides is becoming increasingly used as it may mitigate problems related to weed resistance to herbicides. This work aimed to evaluate the persistence of the residual herbicide imazaquin when applied simultaneously or in sequence to the non-selective herbicides paraquat and glyphosate, under field conditions and growing chamber, respectively. The experiment was carried out the Agronomic Experimental Station of the Universidade Federal do Rio Grande do Sul (EEA/UFRGS), and at the School of Agronomy of the UFRGS using typical Dystrophic Red Argisol (Ultisol) composed by 28% of clay. The experiments were arranged in a randomized block design, in split-plots with four replications. The non-selective herbicides (paraquat, 600 g ha-1 or glyphosate 720 g ha-1) were applied on the main plots and the residual herbicide imazaquin (300 g ha-1) on the subplots,sequentially or in association with the non-selective herbicides, plus a control, where only a non-selective herbicide was applied. The persistence of imazaquin is longer in the presence of glyphosate when compared to paraquat. No difference was found between simultaneous and sequential application of the non-selective and residual herbicides.