V. L. Silva-Lobo

Qualidade de farelos de arroz cru, extrusado e parboilizado

Rice is the second most consumed cereal in the world, having reached a global production of 661.3 millions of tons, in 2008. Rice bran, resulted from grain milling to obtain white rice or polished parboiled rice, has significant amounts of carbohydrates, proteins, lipids, soluble fiber, vitamins, and minerals. This study had the objective of evaluating some physicochemical and microbiological characteristics of raw rice bran (RRB), extruded rice bran (ERB), and parboiled rice bran (PRB). All the analyses were done according to standardized methods recommended by the Brazilian National Health Vigilance and International Association of Official Analytical Chemists. The PRB presented the highest contents of protein (17.17 g 100 g -1 ), lipids (36.03 g 100 g -1 ), dietary fiber (34.06 g 100 g -1 ), calcium (99.45 mg 100 g -1 ), zinc (15.58 mg 100 g -1 ), cupper (1.45 g 100 g -1 ), and manganese (17.81 g 100 g -1 ), and the lowest levels of carbohydrate (5.73 g 100 g -1 ), ash (7.01 g 100 g -1 ), potassium (507.55 mg 100 g -1 ), and iron (6.83 mg 100 g -1 ). All the rice bran samples showed Aspergillus sp. contamination, but ERB had the lowest colonies counting. All samples showed acceptable microbiological patterns for coliforms at 45oC and Bacillus cereus , and Salmonella sp. absence, according to the Brazilian legislation. The RRB, ERB, and PRB have high nutritive value, being considered good sources of proteins, lipids, dietary fiber, and minerals. KEY-WORDS: Oryza sativa L.; macronutrients; minerals; fungi.

Increased enzymatic activity in rice leaf blast suppression by crude extract of Epicoccum sp

Epicoccum sp. showed in vitro antagonism to the rice pathogens Magnaporthe oryzae, Rhizoctonia solani, Sarocladium oryzae, Monographella albescens and Cochliobolus miyabeanus in dual culture. The colony growth of the rice blast fungus, M. oryzae, was reduced by 42.50%. The lethal doses (LD50) determined based on probit-log dosage response curves at 3 and 6 hours after germination were 393.0 and 326.6 ppm, respectively. The crude extract (600 ppm) reduced appressorial formation by 95.68%. A greenhouse experiment comparing the relative efficiency of conidial suspension and crude extract of Epicoccum sp. in the suppression of leaf blast showed no statistical difference between both application methods. However, the crude extract of Epicoccum sp. (4000 ppm) 48 hours before the application of M. oryzae induced resistance and suppressed leaf blast by 97.6%. Scanning electron microscopy of rice leaves inoculated with crude extract of Epicoccum sp. and challenged with M. oryzae showed appressorial deformation on penetration phase. Peroxidase and β-1,3-glucanase activities increased in plants sprayed with crude extract of Epicoccum sp., 24 hours after the application of the challenger. PAL as well as chitinase activities increased 72 hours after challenge inoculation. Epicoccum sp. was shown to be a potential antagonist and inducer of resistance against M. oryzae.

Relação entre o teor de clorofila nas folhas e a severidade de brusone nas panículas em arroz de terras altas

Relationship between chlorophyll content in leaves and panicle blast in upland rice Rice blast (Magnaporthe oryzae) is the most important yield limiting factor of upland rice in Brazil. The nitrogen application rate and planting date determine the level of panicle blast severity. A field experiment was conducted with the cultivar BRS Bonanca to establish the relationship between chlorophyll content in leaves and panicle blast severity. The layout was a randomized split plot design with three replications. The treatments included 12 planting dates at weekly intervals and five rates of nitrogen (0, 30, 60, 120 and 240 kg ha-1 of N). The chlorophyll content was measured on flag leaf with a chlorophyll meter. Panicle blast severity increased significantly with the increase in nitrogen fertilization. The correlation between nitrogen rate and chlorophyll content in flag leaf was positive and significant (r=0.98; p ≤ 0.01). The relationship between panicle blast severity and chlorophyll content was linear and positive (r= 0.99; p ≤ 0.01). The chlorophyll content in the flag leaf can be included as independent variable in the development of a mathematical model for panicle blast forecasting.

Influência da adubação nitrogenada, época de plantio e aerosporos sobre a severidade da mancha de grãos em arroz de terras altas

Grain discoloration (GD) is ranked second among the most economically important rice diseases. The influence of nitrogen levels, planting date and air spora concentration on the disease severity was studied in the field. GD severity in the rice cultivar BRS Bonanca was assessed on two planting dates (30/11/2006 and 21/12/2006), using five nitrogen levels (0, 30, 60, 120 and 240 kg of N.ha-1) and a randomized split plot block design with three replicates. The effect of N level on GD severity was not significant. The correlation between GD severity and empty spikelets was positive and significant. The fungus population in the air (air spora) was quantified using the volumetric trap Rotorod Sampler from panicle emergence to maturation. Grain discoloration linearly increased with time (r = 0.98; P < 0.01), but the same did not occur with the total number of fungi, which varied from 0.23 to 2.97 spores/liter of air/minute. The fungi present in the air in decreasing order of spore concentration were Nigrospora sp., Pyricularia oryzae, Pithomyces sp., Alternaria sp., Cercospora sp., Fusarium sp., Curvularia sp. and Bipolaris sp. These fungi, Phoma sp. and others were also detected in the seed health testing. The correlation between the quantity of spores of P. oryzae and other fungi was linear and positive (r=0.80, P < 0.01). The number of spores increased with the increase in relative humidity and exponentially decreased with the increase in maximum temperature.

Mal-do-pé do arroz: hospedeiros e resistência varietal a Gaeumannomyces graminis var. graminis

Diversas gramineas que ocorrem em lavouras de arroz apresentam sintomas do mal-do-pe, causado por Gaeumannomyces graminis var. graminis (Ggg), em condicoes naturais de infeccao. Com o objetivo de obter informacoes sobre hospedeiros e resistencia de genotipos de arroz ao mal-do-pe, foi estudada a patogenicidade do isolado Ggg-a 01, coletado de arroz, em sete especies de capim e oito de cereais, em casa-de-vegetacao. Os testes de inoculacao mostraram que o isolado de arroz foi patogenico as plantas daninhas de capim arroz (Echinochloa crusgalli), aviao (Pennisetum setosum), braquiaria (Brachiaria sp.), digitaria (Digitaria horizontalis), marmelada (Brachiaria plantaginea), pe-de-galinha (Eleusine indica) e timbete (Cenchrus echinatus) e que essas especies constituem hospedeiros potenciais do patogeno. Cereais de inverno, como o trigo, aveia, centeio, cevada e triticale, bem como o sorgo, milho e milheto, apresentaram diferentes graus de suscetibilidade ao isolado Ggg-a 01. As diferencas foram significativas, quanto a altura da lesao e a producao de hifopodios e de peritecios nos colmos. Nao foram observados peritecios em milheto, sorgo, timbete e milho. A resistencia de 58 genotipos de arroz de terras altas ao isolado foi avaliada e os genotipos SCIA16 e SCIA08 apresentaram altura de lesao significativamente menor, sendo considerados resistentes, em relacao ao genotipo CNAS10351, altamente suscetivel.