Bacteria of the genus Bacillus can colonize endophytically and benefit several crops including the control of some pest orders. In view of the benefits provided by these microorganisms and in order to find out an efficient biotechnological control for the giant borer, our interest in studying the microorganisms in symbiosis with sugarcane and the giant borer has arisen, since there is no efficient chemical or biological control method for this pest. Therefore, endophytic Bacillus strains were isolated from three sugarcane niches (apoplast fluid, central internode cylinder and roots) and also from the giant borer larvae living inside sugarcane varieties grown in the Northeast region of Brazil. The taxonomical characterization (16S rRNA) of 157 Gram-positive isolates showed that 138 strains belonged to the Bacillus genus. The most representative species were phylogenetically closely related to B. megaterium (11.5%) followed by B. safensis (10.8%), B. cereus (8.9%), B. oleronius (8.9%), B. amyloliquefaciens (7.0%), and B. pacificus (6.4%). BOX-PCR analyses showed very distinct band pattern profiles suggesting a great diversity of Bacillus species within the sugarcane niches and the digestive tract, while the B. cereus group remained very closely clustered in the dendrogram. According to XRE biomarker analysis, eleven strains (FORCN005, 007, 008, 011, 012, 014, 067, 076, 092, 093, and 135) correspond to B. thuringiensis species. Additional studies using conserved genes (glp, gmk, pta, and tpi) indicated that most of these strains were phylogenetically closely related to B. thuringiensis and may be considered different subspecies. In conclusion, this study suggests that the culturable Bacillus species are greatly diversified within the plant niches and showed Bacillus species in the digestive tract of the giant borer for the first time. These results open new perspectives to understand the role and functions played by these microorganisms in symbiosis with this pest and also the possibility of developing an efficient biological control method for the giant borer using strains identified as the B. thuringiensis species.
In this study the effect of different cropping systems and crop successions was evaluated on natural Fusarium sp. contamination and fumonisin levels in corn. The cropping systems consisted of a conventional and no-tillage area cultivated with corn in the summer following either oats or fallow in the winter (2006 and 2007 growing seasons). In addition, the effect of applying nitrogen fertilizer (0, 22.5, 45.0, 90.0 and 90.0 kg ha −1 nitrogen supplemented with potassium oxide) on fumonisin contamination was evaluated in the 2006 growing season. Fusarium sp. was detected in 90% samples in 2006 and in 100% samples in 2007. In both growing seasons, no-till corn following oats showed the highest mean fumonisin levels and differed significantly (P<0.05) from all the others (2006) and from conventional till corn following either oats or fallow in the winter (2007). Fumonisin levels ranged from 0.13 to 19.52 μg g −1 (mean 6.97 μg g −1 ) and from 3.70 to 7.75 μg g −1 (mean 6.29 μg g −1 ) in no-till corn following oats from the 2006 and 2007 growing seasons, respectively. Plots treated with 0 kg ha −1 and 22.5 kg ha −1 nitrogen showed the highest mean fumonisin levels and differed significantly from those with 45.0 and 90 kg ha −1 nitrogen. Fumonisin levels correlated negatively (P<0.05) with the nitrogen fertilization rates. Although no-till is advantageous from a soil conservation standpoint, it may enhance the potential for fumonisin contamination in corn.
The degree of exposure of broilers to ochratoxin A (OTA) in naturally contaminated feed and the hygienic quality of feeds were evaluated. Thus, total fungal count and OTA occurrence were evaluated in four feed types (pre-starter, starter, grower and finisher) intended for broilers from a poultry breeding farm in Paran a State, Brazil. In most feed samples the total mold and yeast count were below 1.0 3 10 4 CFU/g, the maximum limit tolerated to assure good hygienic quality of the feed. OTA was detected in 19.1% samples at levels ranging from 0.1 to 8.26 lg/kg. The estimated daily intake of OTA was 0.015 mg/kg body weight (bw)/day (pre-starter), 0.005 (starter), 0.028 (grower) and 0.015 mg/kg bw/day for finisher feed samples. These results indicated that the exposure degree of broilers and the risk of OTA carry-over to human food (broiler meat) would be very low. Practical applicationsThe risk of mycotoxin contamination in grains and feed is an important food safety concern. OTA is one of the most important mycotoxins contaminating broiler feed because of its potential toxic effects to humans and animals. OTA is heat stable and cannot be removed by industrial processing; therefore carry-over of OTA to kidney, liver and muscle increase the human hazard exposure.Evaluation of the exposure degree is one of the most important parameters for the risk assessment of mycotoxins. Considering the world globalization, this study is essential because Brazil is the third largest producer of broilers worldwide and the leading exporter of chicken meat supplying 158 countries. The results of this study showed that the exposure degree of broilers and the risk of OTA carry-over to human food (broiler meat) would be very low, indicating that the meat exported by Brazil would be safe for consumption concerning OTA. K E Y W O R D Sbroiler meat, carry-over, food safety, mycotoxins, natural toxins
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