Crops with potential for diclosulam remediation and concomitant bioenergy production.

The objective of this work was to evaluate crops for their ability to phytoremediate diclosulam residues in the soil and produce lignocellulosic ethanol. Physiological characteristics, biomass production, soil cover rate, fermentable sugar production and lignocellulosic ethanol production potential of the crops were evaluated in soil with diclosulam residues. The experimental design was a randomized block with four replications. The treatments were arranged in a 4 × 2 factorial scheme with the following crops as the first factor: Avena sativa, Canavalia ensiformis, Mucuna aterrima, and Pennisetum glaucum. The second factor was the presence or absence of the herbicide diclosulam in the soil (30 g ha-1). The physiological variables of the plant species were not affected by the presence of diclosulam; the soil cover of P. glaucum was lower in the area with diclosulam, with a value of 26%. The levels of glucose were not affected by the presence of diclosulam in A. sativa, C. ensiformis, and M. aterrima, indicate not change the estimated yield of ethanol for this species. Avena sativa and Pennisetum glaucum have the potential to phytoremediate soils containing diclosulam residues, with concomitant lignocellulosic ethanol production ability.

Phytoremediation of soils with herbicide residues is a viable tool and has been increasingly widespread throughout the world. The use of plant species capable of making the soil feasible for successive plantings sensitive to previously applied residual herbicides is a way to optimize agricultural production. However, there are few studies in which vegetable biomass used in the phytoremediation process is used. Thus, our study is innovative because it seeks to combine phytoremediation with the production of bioethanol, ensuring even more sustainable agriculture.

Alkaline extract from vermicompost reduced the stress promoted by As on maize plants and increase their phytoextraction capacity.

Arsenic (As) represents an environmental risk and phytoremediation has been identified as a good technique to recover contaminated soils. Plants defense mechanisms needed to be enhanced against As stress-promoting action by biostimulants such as humic materials. This work sought to determine the effectiveness of an alkaline vermicompost extract (AEV) and in mitigating stresses promoted by As in maize plants, increasing their potential use for phytoextraction. The AEV were extracted from vermicompost and two preliminary assays in Leonard pots were carried out: the first one to define the best AEV concentration-response dose and the second to point out the toxic As concentration. The second step was to set up a 28-day long experiment with the following four treatments: control, AEV, As, As + AEV. AEV attenuated As-induced stress in maize plants. Maize dry biomass was reduced in the As treatment and rebalanced to values similar to the control in the As + HS treatment while the plants treated only with HS showed the highest biomass among the treatments. The concentrations of P, Fe, Cu, Mn and Ni, and catalase (CAT), ascorbate peroxidase (APX) and superoxide dismutase (SOD) antioxidant activity increased in the As treatment and decreased in the As + AEV treatment. The rate of photosynthesis decreased, and the internal CO2 concentration increased with stress induced by As, where both effects were attenuated by AEV. Our results show the positive effect of the AEV in alleviating As abiotic stress on maize growth, offering new options of employment of humic substances in phytoremediation process.

Remedial capacity of diclosulam by cover plants in different edaphoclimatic conditions.

Pre-emergent herbicides have been developed for their long residual effect; however, they can make sensitive successor cultures unfeasible. Waste remediation techniques are needed for sustainable agricultural systems; for this, the edaphoclimatic asymmetries in the country must be considered. This study aimed to evaluate the remedial capacity of the herbicide diclosulam by covering crops under different edaphoclimatic conditions. Treatments were arranged in an n × 2 factorial scheme, the first factor being the number of plant species in each location and the second being the presence or absence of diclosulam in the soil. The physiological and growth characteristics of 15 potential phytoremediation species were evaluated. Herbicide residues in the environment were positively correlated with the soil pH; organic matter, aluminum, and silt contents; and aluminum saturation. The effectiveness of phytoremediation varied between species and between regions. Plant species suitable for efficient phytoremidation systems of diclosulam residues were Canavalia ensiformis for Couto Magalhães de Minas, Cajanus cajan and Canavalia ensiformis for Diamantina, Raphanus sativus for Erechim and Cajanus cajan for São João Evangelista.

Genotypic value in hybrid progenies of Panicum maximum Jacq / Valor genotípico de progênies híbridas de Panicum maximum Jacq

ABSTRACT: Genetic breeding of forage plants has increasingly contributed to the release of more productive plants. In this regard, evaluating the genotypic value is essential when aiming to rank genotypes based on the mean free of environmental factors. Therefore, this study aimed to predict the genotypic value of agronomic and nutritive value characters of three progenies of Panicum maximum. Hybrids were evaluated in a clonal test in an incomplete-randomized design with three treatments (progenies 1, 2, and 3) and two replications (clones). Six harvests were performed at 25cm from the ground level throughout one year. Progeny 2 provided better results for total and leaf dry mass yield, regrowth, and height, and lower incidence of leaf spot. Progenies 1 and 3 had a better response for qualitative characters such as higher crude protein and digestibility and lower lignin and fiber content. Hybrid progenies of P. maximum have forage characters of interest for breeding, and when using 'Mombaça' grass as parents, the progeny stands out for leaf production and resistance to leaf spot and for 'Tanzania' grass as parent has resulted in better forage quality.

RESUMO: O lançamento de forrageiras resultantes de programas de melhoramento genético tem sido importante fonte de liberação de novas forrageiras mais adaptadas e competitivas. Nessas situações, a avaliação do valor genético é essencial quando se objetiva ranquear os genótipos com base no valor genotípico, isento dos efeitos ambientais. O objetivo com este trabalho foi estimar e avaliar o valor genotípico de características agronômicas e de valor nutritivo de três progênies de P. maximum, resultantes do cruzamento entre duas progenitoras sexuais e as cultivares 'Mombaça' e 'Tanzânia'. O experimento foi implantado em teste clonal no delineamento em blocos incompletos com três tratamentos (progênies 1, 2 e 3) com duas repetições (clones). Os híbridos foram manejados por meio de cortes na altura de 25cm do nível do solo por um ano, realizando seis cortes. A progênie 2 proporcionou melhores resultados para produção de folhas, rebrota, altura de planta e baixa incidência de mancha foliar causada por Bipolaris maydis. As progênies 1 e 3 apresentaram, em média, melhores resultados para características qualitativas como proteína bruta e digestibilidade e menor teor de lignina. As progênies híbridas de P. maximum apresentam características forrageiras de interesse para o melhoramento, sendo que a utilização do capim-mombaça como parental proporciona maior produção de folhas e resistência à mancha foliar, ao passo que o capim-tanzânia como parental proporciona melhoria da qualidade da forragem.

Susceptibility and physiological responses of Jatropha curcas accessions to broad mite infestation.

The broad mite Polyphagotarsonemus latus is a key pest of physic nut (Jatropha curcas L.). The purpose of this study was to identify physic nut accessions that are less susceptible to P. latus, in support of the breeding program of J. curcas. We first evaluated population growth rate and injury symptoms of P. latus on different J. curcas accessions and then carried out physiological analyses on P. latus-infested and uninfested accessions. From the germplasm bank of the Federal University of Viçosa, 15 physic nut accessions with high seed oil content, with different genetic background, were tested. The following traits were evaluated: instantaneous population growth rate of P. latus (r i ), injury symptoms, relative leaf water content, specific leaf area, gas exchange, photosynthetic pigments, nitrogen and biomass of the aerial part. Significant differences were observed for P. latus population growth rate and injury symptoms among accessions. A positive correlation between P. latus growth rate and injury was found. The UFVJC72 accession stood out as the more resistant, considering P. latus growth rate and injury symptoms, compared with most accessions. Physiological responses did not vary among accessions, but did between infested and uninfested plants. In P. latus-infested plants, net photosynthesis was on average 50.5 % lower than in uninfested plants, whereas stomatal conductance and transpiration decreased by 46.2 and 51.6 %, respectively.