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-The objective of the present work was to induce chromosome doubling in genotypes of Brachiaria ruziziensis with potential for production of good-quality biomass and tolerance/resistance to stress caused by aluminum and spittlebugs. Germinated seeds of B. ruziziensis were immersed in 0.1% colchicine solution for 2 or 3 hours. Ploidy level was determined by flow cytometry and confirmed by chromosome count. Fertility of the tetraploid plants was assessed through evaluation of pollen viability by staining. There was no statistical difference with regard to seedling survival and number of duplicate seedlings between the treatments. Survival rate was 8%, of which 11.45% were tetraploid genotypes. The mean viability of pollen grains from the evaluated tetraploid plants ranged from 51.75 to 55.50%. So, the tetraploids plants obtained from genotypes of a bred population of ruzigrass produce fertile pollen, in percentages that render crosses viable in genetic breeding programs.

ABSTRACT.Tannase is an industrially important enzyme produced by a large number of microorganisms. This study analyzed the production of tannase by Aspergillus sp. GM4 under solid-state fermentation (SSF) using different vegetable leaves (mango, jamun and coffee) and agricultural residues (coffee husks, rice husks and wheat bran). Among the substrates used jamun leaves yielded high tannase production. The Plackett-Burman design was conducted to evaluate the effects of 12 independent variables on the production of tannase under SSF using jamun leaves as substrate. Among these variables, incubation time, potassium nitrate and tannic acid had significant effects on enzyme production. A lower incubation time was fixed and supplementation with potassium nitrate and tannic acid were optimized using the Central Composite Design. The best conditions for tannase production were: incubation time of 2 days; tannic acid at 1.53% (w w -1 ) and potassium nitrate at 2.71% (w w -1 ). After the optimization process, tannase production increased 4.65-fold, which showed that the statistical experimental design offers a practicable approach to the implementation of optimization of tannase production.

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