Uma das limitações para sustentabilidade do sistema de cultivo em plantio direto é a rápida decomposição da matéria seca. Um dos mecanismos conhecidos para minimizar este processo e potencializar a permanência da palhada no solo é alterar as vias metabólicas dos polímeros de lignina com aplicação de subdoses de herbicida, interferindo diretamente na resistência à degradação dos restos vegetais pelos microrganismos. Com este objetivo, o herbicida Verdict*R (haloxyfop-methyl) foi aplicado em subdoses nas plantas de aveia-preta e o efeito correlacionado com a altura das plantas, produtividade da matéria seca e metabolismo de lignina. Ensaios preliminares em casa de vegetação foram realizados para determinar as faixas de subdoses a serem aplicadas no experimento definitivo em campo. Os resultados obtidos demonstraram aumento de 24% na produtividade de matéria seca dos experimentos conduzidos em casa de vegetação com a aplicação de 3,125g do ingrediente ativo de haloxyfop-methyl por hectare (i.a. ha-1) nesta subdose, não foram observadas alterações na altura e no metabolismo de lignina nas plantas de aveia-preta. No campo, a concentração de 2,5g i. a. ha-1 do haloxyfop-methyl já foi suficiente para reduzir em 9% a taxa de lignificação sem interferir na altura e produtividade das plantas, sendo este resultado favorável à velocidade de degradação da palhada no plantio direto

One of the major constraints to sustainable of the tillage is the rapid decomposition of dry the matter. One of the mechanisms known to facilitate this process is the interference in pathways of polymers of lignin from tests of application of low doses of herbicide based on the relation that higher the content of the lignin greater the resistance to degradation. With this purpose, the herbicide Verdict * R (haloxyfop-methyl) was used to verify the effect of low doses at the height of the plants, productivity of dry matter and in the metabolism of the lignin in plants of black oat. Preliminary tests in the greenhouse were realized for adjustments to the best low doses to be applied in the definitive experiment in the production area. The results obtained were 24% of increase in productivity in the experiments conducted in greenhouse, from the application of 3.125g of the active ingredient of the haloxyfop-methyl per hectare, in this subdose no changes was observed in growth and content of lignin in plants of black oat. In the field, the concentration of 2.5g i. a. ha-1 of haloxyfop-methyl decreased in 9% the lignification rate without interfering with the height and productivity of the plants, this being favorable to the degradation rate of stubble tillage on outcome

Herbicides inhibit enzymatic systems of plants. Acetolactate synthase (ALS, EC = 4.1.3.18) and 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS, EC 2.5.1.19) are key enzymes for herbicide action. Hundreds of compounds inhibit ALS. This enzyme is highly variable, enabling the selective control of weeds in a number of crops. Glyphosate, the only commercial herbicide inhibiting EPSPS is widely used for non-selective control of weeds in many crops. Recently, transgenic crops resistant to glyphosate were developed and have been used by farmers. The aim of this study was the data mining of eucalypt expressed sequence tags (ESTs) in the FORESTs Genome Project database (<A HREF="https://forests.esalq.usp.br">https://forests.esalq.usp.br</A>) related to these enzymes. Representative amino acid sequences from the NCBI database associated with ALS and EPSPS were blasted with ESTs from the FORESTs database using the tBLASTx option of the blast tool. The best blasting reads and clusters from FORESTs, represented as nucleotide sequences, were blasted back with the NCBI database to evaluate the level of similarity with available sequences from different species. One and seven clusters were identified as showing high similarity with EPSPS and ALS sequences from the literature, respectively. The alignment of EPSPS sequences allowed the identification of conserved regions that can be used to design specific primers for additional sequencings.

This work was aimed at locating Eucalyptus ESTs corresponding to the GS enzyme (Glutamine Synthetase, EC = 6.3.1.2) and to the D1 protein, which are directly related to resistance to herbicides that promote oxidative stress. Glutamine Synthetase corresponds to the site of action of the herbicide glufosinate. Herbicides that belong to groups such as ureas, uracils, triazines and triazinones act on the D1-Qb complex (receptor of electrons from the Photosystem II) by inactivating it. The clusters EGEQRT3302E01.g, EGEQRT3001F12.b; EGEZLV1203B04.g; EGBGFB1211H06.g and EGEZLV1205F09.g enclosed complete sequences (with 356 amino acids) of the Glutamine Synthetase enzyme. The cluster EGEQSL1054G06.g is a consensus of four reads and enclosed a complete sequence of D1 Protein (with 353 amino acids). The comparison of the sequences of Protein D1 from different species showed that the substitutions of serine (S) by glycine (G) or serine (S) by threonine (T) at the position 264 could produce plants resistant to herbicides that act on electron flow on Photosystem II. The sequence of amino acids corresponding to the cluster EGEQSL1054G06.g had a serine in position 264 indicating sensitivity of the Eucalyptus plants to herbicides that act on this site.

This work was aimed at locating Eucalyptus ESTs corresponding to the PROTOX or PPO enzyme (Protoporphyrinogen IX oxidase, E.C. 1.3.3.4) directly related to resistance to herbicides that promote oxidative stress, changing the functionality of this enzyme. PROTOX, which is the site of action of diphenyl-ether (oxyfluorfen, lactofen, fomesafen), oxadiazole (oxadiazon and oxadiargyl), and aryl triazolinone (sulfentrazone and carfentrazone) herbicides, acts on the synthesis route of porphyrins which is associated with the production of chlorophyll a, catalases, and peroxidases. One cluster and one single read were located, with e-values better than e-70, associated to PROTOX. The alignment results between amino acid sequences indicated that this enzyme is adequately represented in the ESTs database of the FORESTs project.