Scielo RSS <![CDATA[Bragantia]]> vol. 76 num. 4 lang. es <![CDATA[SciELO Logo]]> <![CDATA[Cytomolecular characterization of cultivars and landraces of wheat tolerant and sensitive to aluminum toxicity]]> ABSTRACT Karyotyping and chromosome complement knowledge are a prerequisite for cytogenetic mapping. The aim of this study was to characterize 1 common wheat cultivar (BH 1146) and 4 durum wheat genotypes (IAC 1003, Langdon, P19 and P33) from the breeding program of the Agronomic Institute of Campinas (IAC), using karyotype analysis together with Chromomycin A3/4’-6-Diamidino-2-phenylindole (CMA/DAPI) banding techniques for longitudinal characterization of chromosomes and fluorescence in situ hybridization (FISH) in the mapping of the 45S rDNA region. Durum wheat chromosome complement number was 2n = 4x = 28 with the following karyotype formula: 22m + 6sm. Common wheat chromosome complement number was 2n = 6x = 42 with the following karyotype formula: 34m + 8sm. Tetraploid and hexaploid genomes presented 2 pairs of chromosomes with secondary constriction and terminal satellites. All 5 wheat genotypes exhibited CMA and DAPI bands and signals in the 45S rDNA regions (FISH-probe pTa71) which varied in number and location on the chromosome complement. All lines showed greater amount of DAPI bands than CMA bands. The FISH-rDNA 45S in situ hybridization signals, related to the nucleolar organizing regions (NORs), were observed in common wheat, presenting signals for the 45S rDNA sequence in 3 pairs of chromosomes. Durum wheat presented signals in 2 pairs. The CMA bands coincided with the location of 45S rDNA region in the chromosomes of durum wheat. The techniques were efficient for chromosomal characterization of all 5 genotypes. <![CDATA[Morning glory species interference on the development and yield of soybeans]]> ABSTRACT Plants from the genus ipomoea are among the most important weeds in Brazil. The objective of this study was to determine the impact of different densities of 2 species of Ipomoea (I. grandifolia and I. purpurea) under different environments (counties of Pato Branco and Renascença, Paraná state, Brazil) on soybean biometric variables, yield components and crop yield loss. Field experiments in 2 distinct places were conducted in a randomized block design, where 1 factor consisted of 8 plant densities (0, 2, 4, 6, 8, 10, 15 and 20 plants∙m−2), whereas the other factor consisted of the 2 Ipomoea species. Joint analysis of the data was performed considering the factors environment, Ipomoea densities and species. The impact of one Ipomoea plant∙m−2 was very high, reaching 26%, on average, of species and environments. The maximum soybean yield loss experienced with the Ipomoea density of 20 plants∙m−2 was close to 80%. The impact of Ipomoea density was more important than the species and environment. This result highlights the importance of correct management of plants of these weed species in soybean crop. <![CDATA[Morphological analysis and DNA methylation in <em>Conyza bonariensis</em> L. cronquist (Asteraceae) phenotypes]]> ABSTRACT The species Conyza bonariensis (L.) cause losses in agriculture due to their invasive capacity and resistance to herbicides like glyphosate. The species of this genus exhibit phenotypic plasticity, which complicates their identification and characterization. Thus, experiments were performed with 2 extreme C. bonariensis phenotypes (called broad leaf and narrow leaf) in greenhouse conditions and in the laboratory, in order to verify if the morphological differences among these phenotypes are a genetic character or result from environmental effects. In addition to the comparative morphological analysis, assessment of DNA methylation profile was performed to detect the occurrence, or not, of differences in the epigenetic level. The morphological characteristics evaluated were length, width, shape, margin and leaves indument; plant height and stem indument; the number of capitula, flowers and seeds. The Methylation Sensitive Amplified Polymorphism technique was used to investigate the methylation levels. The morphological differences of phenotypes supposed to be C. bonariensis are probably genetic in origin and not the result of environmental effects, since, after 6 crop cycles in a greenhouse under the same environmental conditions, these phenotypes remained with the same morphological characteristics and seed production in relation to the original phenotypes found in the collection site. The different phenotypes did not show differences corresponding to DNA methylation patterns that could indicate an epigenetic effect as the cause of the differences between the 2 phenotypes. The results of morphological analysis and methylation probably indicate that maybe they are individuals of populations from different taxa not registered yet in the literature. <![CDATA[Genetic parameters estimates and visual selection for leaves production in <em>Ilex paraguariensis</em>]]> ABSTRACT The selection of yerba mate superior genotypes, based on each plant leaf weight, is based on genetic parameters obtained from experimental plantations and it is practically impossible from the fourth year of age. Therefore, we estimate genetic parameters and check the feasibility of selection through notes and weight estimates of each tree at 18.5 years of age. The genetic material consists of a combined trial of provenances and progenies of half-sibs with 140 progenies from 7 provenances, installed in Ivaí, Paraná, Brazil, in a randomized block design with 10 repetitions. The genetic control of leaf production is of low magnitude (ĥ2a= 0.175042 ± 0.0393) revealing high influence of the environment. The additive genetic correlations between the real weight of leaves × notes and real weight of leaves × visually estimated weight were of high magnitude (higher than 88%). Thus, the selection based on the leaves weight can be carried out without major losses in genetic gains by both methodologies when the purpose is the sexual selection, in which case the sort order has no importance. In the case of vegetative propagation, aiming clonal plantations, in which only the plants with the highest genotypic values should be selected, the selection by means of notes and leaves weight estimates proved to be inefficient. <![CDATA[Sunki mandarin and Swingle citrumelo as rootstocks for rain-fed cultivation of late-season sweet orange selections in northern São Paulo state, Brazil]]> ABSTRACT In Brazilian regions affected by the citrus sudden death disease, sweet orange cultivation depends on the use of resistant rootstocks. Rangpur lime was mainly replaced by Swingle citrumelo and Sunki mandarin rootstocks, more drought-sensitive ones. The diversification of scion selections is also desirable aiming at the increasing demand for not from concentrate orange juice (NFC) that requires high-quality fruits. In this work, we evaluated the performance of 6 selections of Valencia (IAC, Dom João, Late Burjasot IVIA 35-2, Rhode Red SRA 360, Temprana IVIA 25 and Campbell) and Natal IAC sweet oranges grafted onto Swingle citrumelo and Sunki mandarin. The planting occurred in 2001 under rain-fed cultivation in Bebedouro, northern São Paulo state, Brazil. The outline was made through randomized blocks in a 7 × 2 factorial design (selections × rootstock), with 4 replications and 2 trees in unit. Both rootstocks performed well in the region. Sunki mandarin rootstock induced greater tree size and production per plant to the scion selections, 38 and 21%, respectively, plus higher precocity of production compared to Swingle citrumelo. The later determined a greater productive efficiency, as well as a greater percentage of juice in general, albeit with lower concentrations of soluble solids and acidity. Natal IAC, Valencia IAC and Rhode Red Valencia selections presented a higher accumulated production, on average, 218.6 kg∙plant−1 (2004 – 2008), and a higher productive efficiency (kg fruit∙m−3 of canopy) due to their smaller tree size. All assessed selections produced fruits with high soluble solids content that were suitable for juice processing. <![CDATA[Plot size and number of replications to evaluate the grain yield in oat cultivars]]> ABSTRACT The objectives of this study were to determine the optimum plot size (Xo) and the number of replications to evaluate grain yield and verify the variability of Xo among oat cultivars. Thirtytwo uniformity trials of 3 × 3 m were performed, being 8 from each cultivar (URS Charrua, URS Taura, URS Estampa, and URS Corona). Each uniformity trial was divided in 36 basic experimental units (BEU) of 0.5 × 0.5 m. Grain yield was determined in each BEU. The Xo was determined by the method of maximum curvature of the coefficient of variation model. Mean comparisons among cultivars were performed by the Scott-Knott test via bootstrap. The number of replications was calculated by an iterative process until convergence for experiments in completely randomized design (CRD) and randomized block design (RBD). Scenarios formed by i combinations (i = 3, 4, …, 50) treatments — with d least differences among treatment means to be detected as significant at 5% probability of type I error by Tukey test, expressed as a percentage of the overall experimental mean (d = 10%, 15%, 20%, 25%, 30%, 35%, 40%, and 45%) — were planned. The Xo of 1.57 m2 is enough to evaluate the grain yield in these 4 oat cultivars. Four replications to evaluate grain yield with up to 50 treatments in the experimental designs of CRD and RBD are enough to identify significant differences among treatment means of 40.53% of the overall experimental mean, by Tukey test at 5% probability of type I error. <![CDATA[Potassium-modulated physiological performance of mango plants infected by <em>Ceratocystis fimbriata</em>]]> ABSTRACT Mango wilt, caused by the fungus Ceratocystis fimbriata, is an important disease affecting mango production. In view of the beneficial effects of potassium (K) in other profitable crops and the lack of information about the effect of macronutrients on mango wilt development, the present study aimed to evaluate how mango plants supplied with K respond physiologically when infected by C. fimbriata. Mango plants (» 3 years old) from cultivar Ubá were grown in plastic pots containing 58 mg of K·dm−3 (original K level based on the chemical analysis of the substrate) or in plastic pots with substrate amended with a solution of 0.5 M potassium chloride (KCl) to achieve the rate of 240 mg K·dm−3. Disease symptoms were more pronounced in inoculated plants grown at the lower K level. Substantial declines in stomatal conductance, in line with decreases in the internal-to-ambient CO2 concentration ratio and the absence of detectable changes in the chlorophyll a fluorescence parameters, suggest that the decrease in the net carbon assimilation rate is due, at least initially, to stomatal limitations. High concentrations of K and manganese were found in the stem tissues of inoculated plants and supplied with the highest K rate, most likely due to the involvement of these tissues in the local development of defense mechanisms. The results of this study suggest that the supply of K favored the physiological performance of mango plants and their resistance against C. fimbriata infection. <![CDATA[Contribution of non-target-site resistance in imidazolinone-resistant Imisun sunflower]]> ABSTRACT The first commercial herbicide-resistant trait in sunflower (Helianthus annuus L.) is known as ‘Imisun’. Imidazolinone resistance in Imisun cultivars has been reported to be genetically controlled by a major gene (known as Imr1 or Ahasl1-1) and modifier genes. Imr1 is an allelic variant of the Ahasl1 locus that codes for the acetohydroxyacid synthase, which is the target site of these herbicides. The mechanism of resistance endowed by modifier genes has not been characterized and it could be related to non-target-site resistance. The objective of this study was to evaluate the role of cytochrome P450 monooxygenases (P450s) in Imisun resistance. The response to imazapyr herbicide in combination with P450s inhibitor malathion was evaluated in 2 Imisun lines, IMI-1 and RHA426. Malathion reduced herbicide efficacy in both lines, but IMI-1 was affected in a greater extent. A significant reduction in plant growth in response to P450s inhibitors 1-aminobenzotriazole and piperonyl butoxide treatment was detected in the Imisun line HA425. The increased susceptibility to imazapyr after P450s-inhibitor treatment indicates that herbicide metabolism by P450s is a mechanism involved in Imisun resistance. These results also suggest the involvement of different P450s isozymes in endowing resistance to imazapyr in Imisun cultivars. <![CDATA[First report of mixed infection by <em>Pseudomonas syringae</em> pathovars <em>garcae</em> and <em>tabaci</em> on coffee plantations]]> ABSTRACT The bacterial-halo-blight (Pseudomonas syringae pv. garcae) is disseminated by the main coffee areas in the producing states of Brazil. On the other hand, the disease bacterial-leaf-spot (Pseudomonas syringae pv. tabaci) was reported only once in coffee seedlings in a sample collected in the State of São Paulo. In mid-2015, samples of coffee leaves with symptoms of foliar lesions surrounded by yellow halo, were collected in coffee plantations in the State of Paraná and fluorescent bacteria producing or not brown pigment in culture medium were isolated and determined as belonging to the Group I of P. syringae. Through biochemical, serological and pathogenicity tests, the pathogens were identified as P. syringae pv. garcae and P. syringae pv. tabaci, with prevalence of isolates belonging to pathovar tabaci and, as well as in certain samples, it was identified simultaneous infection by both etiological agents. Then, this is the first report of associated occurrence of garcae and tabaci pathovars of P. syringae and of the incidence of “bacterial-leaf-spot” under field conditions and in the State of Paraná. <![CDATA[Soil structural quality degradation by the increase in grazing intensity in integrated crop-livestock system]]> ABSTRACT The intensification of soil use, as in integrated croplivestock system (ICLS), might promote soil structural degradation. A field method to evaluate the soil structural quality is the Visual Evaluation of Soil Structure (VESS). Studies on the application of this method to ICLS are few. This work aimed to evaluate the structural quality of a Dystrudept under ICLS and different grazing intensities through VESS. Thus, the soil structure was evaluated in light grazing (LG) and heavy grazing (HG) in comparison to a neighboring native forest (NF) as reference area. After the grazing period, 10 trenches were dug in each area to collect soil monoliths. The identification of structural differences and the attribution of visual scores were carried out according to the VESS. In NF and HG soils, up to 30 cm deep, it was possible to identify 2 layers with distinct structures, while, in the LG, up to 3 layers were identified. The NF soil presented the best structural quality. Regarding both grazing intensities, there was degradation of the structural quality between soil layers when compared to the NF. The increase in grazing intensity in ICLS promoted in-depth degradation of the soil structural quality. The VESS method was shown suitable to evaluate soils under ICLS management with LG and HG.