Scielo RSS <![CDATA[Scientia Agricola]]> vol. 73 num. 6 lang. es <![CDATA[SciELO Logo]]> <![CDATA[Impact of feeding cottonseed coproducts on reproductive system of male sheep during peripubertal period]]> ABSTRACT Cottonseed coproducts contain gossypol which can have specific effects upon the male reproductive system. We evaluated the reproductive development of male lambs close to puberty fed on three cotton coproducts. Twenty-four 5-month old male lambs received four diets: 20 % of dry matter intake of whole cottonseed (WCS), high oil cottonseed meal (CSC), cottonseed meal (CSM), and a control group (CTL) without any cottonseed coproducts. Free gossypol intake was 16.32, 6.98, 5.47 and 0 mg kg−1 BW−1 d−1 for WCS, CSC, CSM and CTL, respectively. Every 15 days, the animals were weighted and serum and semen samples were collected. After 95 days, testis samples were collected for analysis under light and transmission electron microscopes. The CTL group had higher testosterone concentrations than CSC at the end of the trial and lower total sperm defects, higher mass movement and higher scores for seminiferous epithelium than other treatments. The WCS and CSC groups showed higher levels of segmental aplasia lesion in sperm than other diets, which showed that high levels of gossypol led to higher occurrence of this lesion. Cottonseed coproducts had a negative impact on the reproductive system of pubertal lambs regardless of gossypol concentration. Therefore, the use of cottonseed coproducts to feed lambs earmarked for reproduction is not safe. <![CDATA[Substitution of rumen degradable nitrogen with urea in sheep fed low quality <em>Eragrostis curvula</em> hay]]> ABSTRACT The aim of the present study was to determine whether sunflower meal (SFM), a highly rumen degradable protein (RDP) source, can be substituted with non-protein nitrogen (NPN, urea) without impacting negatively on intake, digestibility, rumen fermentation and microbial nitrogen (N) synthesis (MNS) in wethers consuming low quality Eragrostis curvula hay. Five wethers were fed ad libitum, low quality hay and supplemented twice-daily in equal proportions, via the rumen cannulae, one of five iso-nitrogenous and iso-energetic supplements in a 5 × 5 Latin square design experiment. The supplements differed in the ratios of rumen degradable N (RDN) supplied by either SFM and/or urea and is presented as percentage of RDN supplied by urea: T0 (100 % SFM, 0 % urea); T15 (85 % SFM, 15 % urea); T30 (70 % SFM, 30 % urea); T45 (55 % SFM, 45 % urea) and T60 (40 % SFM, 60 % urea). Forage intake and total tract dry matter (DM) digestibility did not differ; however, higher forage neutral detergent fiber (NDF) digestibilities were observed in the sheep supplemented with the higher urea-treatments (T45 and T60) compared to T15. Neither rumen pH nor total rumen volatile fatty acid (VFA) concentraions differed. The mean rumen ammonia nitrogen (RAN) concentration of the sheep supplemented with T60 was higher than T30 (9.35 mg dL−1 vs. 7.41 mg dL−1); however, no differences were observed in MNS or efficiency of MNS among treatments. Results suggest that up to 60 % of RDN supplied by SFM can be substituted with urea, without affecting intake, digestibility or MNS in wethers fed a low quality tropical hay. <![CDATA[Communication between agricultural scientists and statisticians: a broken bridge?]]> ABSTRACT Modern agricultural research requires a lot of statistics. Unfortunately, most up-todate statistical methods need advanced knowledge, often out of reach for agricultural researchers. Thus, efficient communication between researchers and statisticians is important for the development of agricultural knowledge. Many agricultural researchers claim that communication with statisticians is difficult. On the other hand, many statisticians claim that communication with agricultural researchers is not easy either. This being true, such poor communication can be a barrier to efficient agricultural research. The aim of this research is to study this phenomenon. Do agricultural researchers and statisticians see problems in their communication? What kinds of problems are they? I will try to answer these questions based on a study among scientists representing both groups. <![CDATA[New opportunities for developing tomato varieties with enhanced carotenoid content]]> ABSTRACT The development of varieties with a high content of antioxidant compounds, such as carotenoids, has become a major focus in the marketing of tomato. Several mutants have been used in the development of high pigment varieties, but the significant influence of the environment on carotenoid content and the presence of negative side effects in vegetative growth and yield have limited the success of these variants. Consequently, the identification of alternative sources of variation in the quest for high carotenoid content is ongoing. In this study, 12 accessions of Solanum lycopersicum (including the former var cerasiforme) and S. pimpinelifolium have been evaluated in three different environments: open field and glasshouse cultivation at two sites. Three accessions (BGV6195 of S. pimpinellifolium, LA1423 of the former var cerasiforme and LA3633 a possible hybrid between S. pimpinellifolium and S. lycopersicum) showed outstanding and stable lycopene content, that doubled in all three environments the content of the positive control LA3538, with the high pigment-1 mutation (hp1). In addition, accession CATIE14812 would also be interesting as regards improvement of β-carotene content. These materials offer new opportunities in the development of tomato varieties with enriched and reliable carotenoid content and the close taxonomic relationship of these accessions with cultivated tomato will facilitate their use in breeding programs. <![CDATA[Crop losses in Brazilian cassava varieties induced by the <em>Cassava common</em> mosaic virus]]> ABSTRACT Despite the widespread distribution of the Cassava common mosaic virus (CsCMV) in Brazil, little is known about the losses it causes in yield. The effect of CsCMV on different varieties was evaluated by reference to several agronomic traits. Four field trials were established in 2012/2013 and 2013/2014 using six varieties of cassava. Following mechanical inoculation with CsCMV, the presence of the virus was confirmed using the ELISA assay. The evaluated traits were plant height (PH), dry matter content (DMC), harvest index (HI), aerial part yield (APY), root yield (RoY), and starch yield (StY) in both inoculated and non-inoculated plants. Overall, the presence of the virus contributed little to the reduction in PH, HI, and DMC across the varieties, with PH being significantly reduced by 9.2 and 7.0 % in the BGM0212 and BRS Kiriris varieties, respectively. In contrast, APY, RoY, and StY were reduced by 30.2, 29.3, and 30.0 %, in the virus-infected plants respectively. While the BRS Kiriris and BRS Jari varieties suffered the highest reductions overall and were considered highly susceptible to CsCMV, none of the traits suffered reductions in the inoculated BRS Formosa plants. Although RoY and StY were reduced in inoculated plants of BRS Tapioqueira, crop yield for this variety was the highest. Thus, BRS Formosa and BRS Tapioqueira exhibited tolerance against CsCMV, which warrants further investigation. <![CDATA[Pedotransfer functions to estimate bulk density from soil properties and environmental covariates: Rio Doce basin]]> ABSTRACT Soil bulk density (ρb) data are needed for a wide range of environmental studies. However, ρb is rarely reported in soil surveys. An alternative to obtain ρb for data-scarce regions, such as the Rio Doce basin in southeastern Brazil, is indirect estimation from less costly covariates using pedotransfer functions (PTF). This study primarily aims to develop region-specific PTFs for ρb using multiple linear regressions (MLR) and random forests (RF). Secondly, it assessed the accuracy of PTFs for data grouped into soil horizons and soil classes. For that purpose, we compared the performance of PTFs compiled from the literature with those developed here. Two groups of data were evaluated as covariates: 1) readily available soil properties and 2) maps derived from a digital elevation model and MODIS satellite imagery, jointly with lithological and pedological maps. The MLR model was applied step-wise to select significant predictors and its accuracy assessed by means of cross-validation. The PTFs developed using all data estimated ρb from soil properties by MLR and RF, with R2 of 0.41 and 0.51, respectively. Alternatively, using environmental covariates, RF predicted ρb with R2 of 0.41. Grouping criteria did not lead to a significant increase in the estimates of ρb. The accuracy of the ‘regional’ PTFs developed for this study was greater than that found with the ‘compiled’ PTFs. The best PTF will be firstly used to assess soil carbon stocks and changes in the Rio Doce basin. <![CDATA[Relationships between labile soil organic carbon fractions under different soil management systems]]> ABSTRACT The study of labile carbon fractions (LCF) provides an understanding of the behavior of soil organic matter (SOM) under different soil management systems and cover crops. The aim of this study was to assess the effect of different soil management systems with respect to tillage, cover crop and phosphate fertilization on the amount of the LCF of SOM. Treatments consisted of conventional tillage (CT) and no-tillage (NT) with millet as the cover crop and a no-tillage system with velvet bean at two phosphorus dosages. Soil samples were collected and analyzed for organic carbon (OC), C oxidizable by KMnO4 (C-KMnO4), particulate OC (POC), microbial biomass carbon and light SOM in the 0.0-0.05, 0.05-0.10 and 0.10-0.20 m soil layers. The Carbon Management Index (CMI) was calculated to evaluate the impacts of soil management treatments on the quality of the SOM. The different LCFs are sensitive to different soil management systems, and there are significant correlations between them. C-KMnO4 is considered the best indicator of OC carbon lability. In the soil surface layers, the CT reduced the carbon content in all of the labile fractions of the SOM. The use of phosphorus led to the accumulation of OC and carbon in the different soil fractions regardless of the tillage system or cover crop. The application of phosphate fertilizer improved the ability of the NTsystem to promote soil quality, as assessed by the CMI. <![CDATA[Soil management of sugarcane fields affecting CO<sub>2</sub> fluxes]]> ABSTRACT The harvesting system of green sugarcane, characterized by mechanized harvesting and no crop burning, affects soil quality by increasing the remaining straw left on the soil surface after harvesting, thus, contributing to the improvement of physical, chemical, and microbiological soil attributes, influencing CO2 fluxes. This study aimed to evaluate CO2 fluxes and their relation to soil properties in sugarcane crops under different harvesting managements: burned (B), Green harvesting for 5 years (G-5) and Green harvesting for ten years (G-10). For this, a 1 ha sampling grid with 30 points was installed in each area, all located in the Northeast of São Paulo State, Brazil. In each point, CO2 fluxes were measured and the soil was sampled to analyze the microbial biomass, physical (soil moisture and temperature, mean weight diameter, bulk density, clay, macroporosity and microporosity) and chemical characterization (pH, organic C, base saturation and P). The CO2 fluxes were divided into four quantitative criteria: high, moderate, low and very low from the Statistical Division (mean, first quartile, median and third quartile) and the other data were classified according this criterion. The Principal Component Analysis (PCA) was used to identify the main soil attributes that influence CO2 fluxes. The results showed that G-10 CO2 fluxes were 28 and 41 % higher than those in the G-5 and B treatments, respectively. The PCA analysis showed that macroporosity was the main soil attribute that influenced the high CO2 fluxes. <![CDATA[Closely-related <em>Xanthomonas citri</em> subsp. <em>citri</em> isolates trigger distinct histological and transcriptional responses in <em>Citrus limon</em>]]> ABSTRACT Citrus canker, caused by Xanthomonas citri subsp. citri (Xcc), has an important economic impact on the citrus industry. Extensive information is available about the disease but, nevertheless, the study of plant-pathogen interactions could provide new information in the understanding of citrus canker disease. A new isolate has been identified, Xcc AT, which has a high genetic similarity (&gt; 90 %) to the virulent Xcc T strain based on genetic clustering analyses of the rep-PCR fingerprinting patterns, but it does not produce cankerous lesions in Citrus limon. In this study, we compared C. limon responses to Xcc AT and to the virulent Xcc T strain at both histological and transcriptional levels. Histologically, leaves inoculated with Xcc AT exhibited neither a typical disordering of the spongy mesophyll, nor a swelling of epidermis. A particular content (undetermined) was also found in mesophyll cells near the stomata, together with increased starch accumulation. The transcriptomic profiles were compared by cDNA-AFLP technique. A total of 121 fragments derived from transcript (TDF) were either specifically induced or repressed by the isolates, and 62 were sequenced. Analysis of global expression identified different classes of genes known to be involved in plant-pathogen interactions. This study constitutes the first approach of the specific interaction between the avirulent Xcc AT isolate and C. limon. <![CDATA[Comparison of beat cloth and entomological net methods for determining faunistic indices of soybean in Rio Grande do Sul, Brazil]]> ABSTRACT Estimates of diversity indices provide information on distribution, richness and abundance of species within a community. The aim of the current study was to estimate faunistic indices (richness, constancy, dominance and abundance) of the species collected by beat cloth and entomological net sampling methods in different soybean crops and to determine the sample size necessary to estimate faunistic indices. Fauna density from 100 soybeans crops located in nine municipalities in Rio Grande do Sul, Brazil, were evaluated. Thirty points, 20 meters apart from one another, were marked in the crops. At each point, insect pests and natural enemies were collected using the two sampling methods. Faunistic indices, including the average and interval estimates carried out by the resampling method, were calculated for each soybean crop. In the samplings using the beat cloth, richness &gt; dominance = abundance &gt; constancy, and using the entomological nets, richness &gt; dominance &gt; abundance &gt; constancy. All faunistic indices other than dominance were greater when using the beat cloth method than those estimated by the entomological net method. The sample sizes required to estimate richness, constancy, dominance and abundance indices were 38, 78, 47 and more than 300, respectively, with an estimation error of 20 % of the average (p = 0.05). Higher values were observed when entomological net was used.