Current issues

Table of contents: 2021

Research Article

Management of variability in germplasm banks is essential for genetic improvement, so that the breeder can estimate the genetic similarity between cultivars, as well as maintain genetic diversity in breeding programs. Elephant grass is a forage crop plant native to Africa of great socio-economic and environmental importance; it can be used for animal feed and for bioenergy production. Understanding the genetic variability of elephant grass is essential for breeding programs. In this context, we examined the genetic divergence of elephant grass accessions using the Gower algorithm. The experiment was conducted under field conditions in the municipality of Campos dos Goytacazes-RJ, Brazil. All 85 elephant grass accessions belonging to the Active Elephant Grass Germplasm Bank of Embrapa Gado de Leite were included. These genotypes are commercial varieties from various countries. They were evaluated for morphoagronomic, morphological  and phenological characteristics. The experimental design was randomized blocks with two repetitions. The plots were composed of 5.5-meter rows, with 2.0-meter spacing between the planting rows, totaling 11.0 m2. The useful area was a sample in the center of the plot. We generated an illustrative dendrogram, obtained by the UPGMA method and the Tocher clustering, based on the Gower algorithm. Data were examined by means of the GENES statistical programs and the R program. According to the dissimilarity matrices based on the Gower algorithm, the genetic distances varied between 0.08 and 0.56, and the mean distance of the 85 evaluated accessions was 0.25, suggesting, consequently, that there is wide genetic variability between the accessions. Of the 85 genotypes, seven presented genetic distances smaller than 0.1, being indicative of duplicates in the germplasm bank, which could be eliminated without risk of loss of genetic variability.

Genet. Mol. Res. 20(4): GMR18944
DOI: 10.4238/gmr18944
Research Article

The application in a single or split dose of nitrogen in wheat affects the expression of ear components. Models that simulate these effects can help predict yield. Our objective was to identify wheat ear components that are responsive to the forms of nitrogen supply in a single versus split dose d. This was achieved by testing variables in the construction of a multiple linear regression model for grain yield simulation in harvest simulation analysis. The study was carried out in 2018 and 2019, in a randomized block design with four replications in a 3 x 3 factorial scheme, for three doses of nitrogen (30, 60, 120 kg ha-1) and three forms of nutrient supply [ single dose (100%) at phenological stage V3 (third expanded leaf); split dose (70% and 30%) at phenological stage V3/V6 (third and sixth expanded leaf) and split dose (70% and 30%) at phenological stage V3/R1 (third expanded leaf and beginning of grain filling)] , respectively, in the soybean/wheat and corn/wheat succession systems. This form of fractionation of 70% and 30% is the form commonly used in commercial wheat crops. The wheat cultivar used was BRS Guamirim. Twenty ears of wheat per experimental unit were randomly collected, which were sent to the laboratory. Ear mass (EM, g), ear grain mass (EGM, g), ear grain number (EGN, n), ear length (EL, cm) and ear harvest index (EHI), given by the ratio of ear grain mass to ear mass, dry weight were measured. Nitrogen supplied in single and split doses modifies with greater intensity the wheat ear components ear mass and ear grain mass. The nitrogen in a single dose supplied at stage V3 provides significant superior grain yield compared to split doses, regardless of nutrient dose, crop season and succession system.

Genet. Mol. Res. 20(4): GMR18943
DOI: 10.4238/gmr18943
Research Article

The sweet and chili pepper species of the genus Capsicum are originally from America; however, currently they are grown worldwide. Although widely appreciated, especially in the Amazon region, there have been few studies about C. chinense. Characterization and classification studies can aid in pepper crop genetic breeding and development of new cultivars with characteristics of agronomic interest. Resistance to fruit abscission makes harvesting difficult, which today is essentially manual, so that development of cultivars with easy fruit abscission, allowing semi-mechanized and mechanized harvest is an important goal. Descriptions of genetic differences based on anatomical characters are rare in this genus. Along this line, we examined morphological characters and anatomical structures directly related to easy fruit abscission in C. chinense, through the evaluation of two genotypes contrasting for this character, maintained by the Embrapa Hortaliças Genetic Breeding Program, as well as an F1 hybrid. The morphological characterization of flowers and fruits was performed using 13 descriptors, eight defined by the International Plant Genetic Resources Institute and five adapted for this study. The anatomical characterization of the peduncle and flowers was carried out with the elaboration of plant slides to examine structures possibly linked to easy abscission of the fruit. Contrasting morphological polymorphisms were observed in immature fruit color, fruit shape, fruit position on the plant, abscission and fruit firmness, as well as fruit diameter, number of locules and seeds per loculus. Small differences were observed in the anatomical structures of peduncle and flower, such as the shape of the vascular system and lignification of the pericycle, but none were directly related to fruit abscission. Although there was no significant anatomical relationship with fruit abscission, the morphological characters evaluated in this study revealed great genetic variability for these genotypes, demonstrating potential of these genotypes in a breeding program for developing varieties with easy fruit abscission.

Genet. Mol. Res. 20(4): GMR18887
DOI: 10.4238/gmr18887
Research Article

The species Nicotiana tabacum, known as tobacco, is one of the crops with the highest economic value in the world among non-food species. Since 2000, Brazil has become the world’s second largest tobacco producer. Brazilian production is mainly concentrated in the South region. The main tobacco types are produced in Brazil, such as Dark, which, despite representing a small percentage of the total production in Brazil, is economically important because of a high added value. Until now the only available cultivar is a line that despite having a desirable alkaloid content, has low productivity. In an effort to help improve production, we estimated the heterosis of diallel crosses involving tobacco lines of the Dark tobacco type. A complete diallel cross was made involving 10 lines from the British American Tobacco company breeding program. The 45 hybrid combinations, together with the 10 parental lines and nine other commercial controls, were evaluated at four sites in Southern Brazil, using a triple lattice experimental design (8 x 8). The characteristics evaluated included: green leaf mass (Productivity - YLD), and total alkaloid content (ALK), and the selection index was obtained by the sum of standardized variables (SSV), considering a weight of 70% for YLD and 30% for ALK. Estimated correlation between YLD and the ALK was -0.66. The use of the selection index allowed simultaneous gains in both traits, although they were of less magnitude than selection for each characteristic individually. The average heterosis was 8.6% for productivity, -1.4% for the total alkaloid content, and 5.3% for the selection index. However, considering the selection index, hybrids were obtained with an average heterosis greater than 10%. Under these conditions, the use of hybrids should be encouraged not only to combine favorable phenotypes, but also to explore the beneficial effects of heterosis.

Genet. Mol. Res. 20(4): GMR18929
DOI: 10.4238/gmr18929
Research Article

Carrot is a vegetable of worldwide importance due to its high nutritional quality and wide application in food. The adjustment of plant arrangement in carrot cultivars is decisive for the productivity and quality of roots; in a conventional system, a spacing between rows of 20 cm is indicated. However, few studies address the interaction cultivar versus row spacing in an agro-ecological cropping system, suitable for production without pesticides and fertilizers. We examined the performance of carrot cultivars at different spacing between rows on the yield and quality of roots in an agro-ecological system, with the objective of greater sustainability of food security cultivation. This experiment was carried out in Augusto Pestana, RS, Brazil, from February to June, in 2019 and 2020. The design was a randomized block with three replications in a 5x3 factorial scheme, for five carrot cultivars (Danvers, Brasília Calibrada Media, Nantes, Esplanada and Brasília Nina) and three spacings between lines (10, 15 and 20 cm), respectively. The cultivars used are the most used accepted genotypes for cultivation in Brazil. In the study, the indicators of productivity and quality of roots were evaluated. The Brasília Nina carrot cultivar showed high performance in root yield and quality, mainly in the 15 cm spacing between rows in an agro-ecological system. The production of carrot roots with quality and free from toxic contaminants, contributes to the valorization of the product for commercialization and the production of food with greater sustainability and food safety.

Genet. Mol. Res. 20(4): GMR18941
DOI: 10.4238/gmr18941
Research Article

ABSTRACT.  Common bean yield is directly related to climate conditions, and water deficit is one of the main limiting factors. One way of getting around this problem is increasing the frequency of alleles favorable to drought tolerance by the recurrent selection method. We estimated the morphophysiological and agronomic gains achieved in two recurrent selection cycles for drought tolerance and evaluated the genetic potential of the progenies obtained in each cycle. The first recurrent selection cycle was obtained by intercrossing 10 genotypes. This cycle was followed by physiological, morphophysiological, and agronomic evaluations, resulting in selection of 17 progenies. The second cycle was obtained by intercrossing the 17 selected progenies, followed by the same evaluations, resulting in 20 selected progenies. A randomized block experimental design was used for both selection cycles, with split plots and three replications. The plots consisted of two water treatments (irrigated and water deficit), and the subplots consisted of the progenies under evaluation. To select the progenies and estimate the genetic parameters, only the treatment under water deficit was considered, in randomized blocks with three replications. Irrigation was suspended at the R5 stage. Under these conditions, the following traits were evaluated: stomatal conductance, leaf temperature, relative chlorophyll index, leaf area, leaf dry matter, and shoot dry matter. After that, irrigation was reestablished and the following determinations were made: plant height, number of pods per plant, number of seeds per plant, number of seeds per pod, 100-seed weight, and grain yield. Recurrent selection was effective for selection of drought-tolerant plants, with gain from selection for grain yield of 231.94 kg ha-1 in the first cycle and 387.71 kg ha-1 in the second. Three progenies in the first selection cycle and 19 in the second selection cycle were identified as having better performance under water deficit conditions, which allowed drought-tolerant progenies to be chosen for use in breeding programs.

Genet. Mol. Res. 20(3): GMR18902
DOI: 10.4238/gmr18902
Research Article

Staphylococcus aureus is one of the main pathogens of importance in health care. Distributed worldwide, it has considerable impact on community and nosocomial infections. This bacteria has the tst and lukS-F PV genes that code for the TSST-1 toxin and leucocidin. These pathogenic microorganisms have the ability to survive for long periods on inert surfaces such as mobile phone screens. Senior dentistry students work in clinics and use their cell phones often, which could potentially spread this pathogen. We looked for the tst and lukS-F PV genes in S. aureus isolated from mobile phone screens of final year dentistry students. This was a descriptive cross-sectional observational study using 92 samples from the mobile phone screens of dental students, among which 16 were positive for S. aureus. They were identified by means of culture methods and detection of the nuc, nucA and femB genes.  The DNA was extracted using the alkaline lysis method; PCR was used in the molecular identification of the tst and lukS-F PV genes. Nine of the 16 S. aureus isolates had the tst gene, and 1/16 the lukS-F PV gene. This study shows the high frequency of virulent S. aureus on the mobile phone screens of dental students, which may contribute to the spread of this important pathogen.

Genet. Mol. Res. 20(3): GMR18928
DOI: 10.4238/gmr18928
Research Article

Water stress triggers various cellular responses in plants, altering normal metabolic flow. Pyruvate, an important component of the glycolysis pathway, is directly involved in cell processes, triggering genes that influence drought tolerance. Research with Arabidopsis has shown that synthetic pyruvate relieves drought damage. We evaluated the effects of exogenous pyruvate at 100 and 50,000 µM on mitigation of drought stress in two peanut cultivars submitted to water restriction. The evaluations were based on growth, gas exchange, and photosynthesis rate analyses. In addition, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) enzymes, and free proline were also assayed. In general, exogenous application of pyruvate contributed to mitigate the effects of water stress in the cultivar IAC Caiapó (sensitive to drought), based on gas exchange and instantaneous efficiency of water use. Exogenous pyruvate contributed to restore the action of antioxidative enzymes in BR 1 (tolerant to drought), based on measures of SOD (45%), CAT (129%) and APX (60%) in stressed plants, and full recovery at 50,000 µM. When treated with proline, stress attenuation was found only at 100 µM in both cultivars; the excess seemed to have a negative effect on stressed plants, probably affecting the cell environment.

Genet. Mol. Res. 20(3): GMR18907
DOI: 10.4238/gmr18907
Research Article

Currently, the use of cell phones is booming within the health system. Since they are frequently used, they have become an important vehicle for nosocomial infections, with Staphylococcus aureus being the most commonly found pathogen. We tested for resistance to beta-lactams in S. aureus isolated from phone screens of senior dentistry students who were involved in pre-professional clinical practice. Out of a total of 220 students, 92 participated in the study, from which 16 S. aureus positive samples were obtained; these samples are relevant due to the fact that the participants were in contact with patients. The S. aureus genes were identified by means of a PCR and the antibiotic resistance by using the Kirby Bauer's diffusion technique. All 16 isolated strains contained the blaZ gene; in seven the mecA gene was identified. Phenotypic resistance to penicillin and oxacillin manifested in 12 and 7 strains, respectively. We conclude that dental professional cell phones have potential as a nosocomial risk for pathogenic bacterial contamination.


Genet. Mol. Res. 20(3): GMR18931
DOI: 10.4238/gmr18931
Research Article

Canine distemper is a highly infectious disease, distributed throughout the world. It is characterized by lymphotropism, neurotropism, and epitheliotropism, resulting in severe clinical changes and death. We report on the clinical and hematological findings of dogs with neurological distemper. Thirty-two mixed breed dogs of both sexes and of various age groups with clinical presentation suggestive of distemper with neurological involvement were evaluated. Blood and urine samples were collected for hematological and PCR analysis. Of the 32 animals evaluated by the RT-PCR technique, 22 were positive for the distemper virus. In the clinical presentation of distemper positive animals, neurological disorders stood out, with myoclonus being the most prevalent (18/22). In the hematological evaluation, erythrocytes and leukocytes were within the reference range; thrombocytopenia and lymphopenia were the most relevant findings in dogs with neurological involvement and could be used by veterinary clinicians as auxiliary diagnostic parameters.

Genet. Mol. Res. 20(3): GMR18884
DOI: 10.4238/gmr18884
Research Article

The study of genetic diversity of a population is one of the pillars to make selection in a breeding program successful. There are several techniques capable of estimating genetic divergence. Among them, those based on multivariate statistics deserve attention. Recently, methodologies based on Artificial Neural Networks (ANN) have been used to study the genetic diversity of a population. One of the strategies within ANN is Kohonen’s self-organizing maps (SOMs), which allows the organization of genetic diversity.  We estimated and organized the genetic divergence of pepper and chili genotypes Capsicum annum) for selection of diallel crosses. The experiment was conducted in a greenhouse in a completely randomized design with four replications. Nine commercially important genotypes of C. annum were evaluated, based on seven quantitative characters of the fruit. Univariate analysis was performed by analysis of variance and cluster mean. Multivariate [unweighted pair group method with arithmetic means (UPGMA) and Tocher)] and machine-learning techniques [SOMs] were employed. The genotypes showed high genetic variability for all traits. The traits total mass of raw fruit and fresh fruit length contributed the most to genetic diversity. UPGMA and Tocher classified the genotypes into two and four clusters, respectively. Through SOMs, it was observed that the neighborhood pattern between chili and pepper was obtained in only seven of the 12 neurons previously established. Overall, the use of SOM allowed the organization of genetic diversity among the genotypes. Specifically, SOM did not recommend crossing genotypes from the Cascadura Ikeda chili x Giant Ruby chili, Spicy for Pot pepper x Yellow Jamaica pepper, and Volcano pepper x Peter Pepper for variability exploration.

Genet. Mol. Res. 20(3): GMR18888
DOI: 10.4238/gmr18888
Research Article

Colombian creole breeds Blanco Orejinegro (BON) and Sanmartinero (SM) are widely used as pure breeds and in crossbreeding programs due to their excellent performance in the double ability of milk and meat production. We examined genomic regions and genes that from generation to generation have been selected by positive natural selection in favor of the adaptability and reproductive performance of these two Colombian creole breeds. Natural selection of genomics region and genes is one of the main evolutive changes resulting in phenotypic adaptations. The selected genomic regions can be detected by comparing differences in regional linkage disequilibrium (LD) between cattle populations with potential adaptations for economic traits. In this study, we used 58,868 single nucleotide polymorphisms (SNPs) from BON and 57482 SNPs from SM, using genotyping data from 1262 BON and 742 SM animals to estimate the variation of genome-wide LD between populations using the VARLD program. The top 0.1 and 0.01th percentiles of standardized VarLD scores were used as a criterion for all comparisons. A total of 10 selection signatures on chromosomes 3, 5, 11, 15, 18, 21, 22, 23, 25 and 29 were identified in all populations. These signatures overlapped with quantitative trait loci for adaptability and reproductive performance in both breeds. Within the signature located between 23,903,882 and 23,955,588 bp on chromosome 18, we identified the SLC6A2 gene involved in the response to high stress. Also, we identified the genes CTDSP2, CES1, CFAP161, CLEC14A, HIPK1, RBM4, SSTR involved in the expressions of economic traits (meat and milk production), KDMID, OLFML3 genes involved in reproductive traits (age at first calving and calving interval), and ATP23, LRRTM1, SLC6A2, DEK, SYT6, KDMID genes involved in cellular stress response and response to important environmental changes such as high temperature. We conclude that these genomic regions seem to point toward a recent selection in BON and SM populations. These regions can be used in selection and conservation programs.

Genet. Mol. Res. 20(3): GMR18882
DOI: 10.4238/gmr18882
Research Article

The Colombian Creole bovine breeds Blanco Orejinegro (BON) and Sanmartinero (SM) are the most important of the Creole breeds in Colombia because they are the most numerous, the most widely used in their pure form or in crosses with foreign breeds, and because they are dual-purpose producers of milk and meat. We estimated heritability for adaptability (coefficient of adaptability-CA and heat tolerance coefficient-HTC), and reproductive traits (age at first calving-AFC and calving interval-CI) using genomic and genealogical records. Variance components were estimated using the AIREMLF90 program under a mixed single-trait model to calculate genealogical and genomic heritability, based on genealogical, phenotypic, and genomic information.  Genomic information was obtained for 1,262 BON and 742 SM genotyped animals, with a total of 58,868 single nucleotide polymorphisms-SNPs in BON, and 57,482 SNPs in SM. Genealogical heritability values in BON for CA and HTC were 0.05 and 0.13, and 0.06 and 0.13 for AFC and CI, respectively. For the SM breed, genealogical heritability values ​​for CA and HTC were 0.08 and 0.09, and 0.20 and 0.07 for AFC and CI, respectively. Genomic heritability values in the BON breed ​​for CA and HTC were 0.06 and 0.16, and 0.07 and 0.14 for AFC and CI, respectively. For the SM breed, genomic heritability values ​​for CA and HTC were 0.10 and 0.11, and 0.20 and 0.07 for AFC and CI, respectively. Heritabilities for adaptability traits in both BON and SM were of medium to low magnitude, indicating the possibility of using these variables in selection schemes for adaptation-related characteristics.

Genet. Mol. Res. 20(3): GMR18878
DOI: 10.4238/gmr18878
Research Article

The management of nitrogen in wheat based on biological and environmental indicators can ensure productivity with a reduction in environmental impact. The objective of the study was to develop a more sustainable management of nitrogen use in wheat, considering the dose as a fraction of the total supply based on an estimate of the maximum technical and economic efficiency, and expected grain yield, in systems of succession of high and reduced release of N-residual, during acceptable and unfavorable crop years. The study was conducted from 2012 to 2018, in Augusto Pestana, RS, Brazil. Two experiments were conducted in each agricultural year and in each rotation system (soybean/wheat and corn/wheat), one to quantify the biomass yield and the other to determine grain yield. The experimental design was a randomized block with four repetitions in a 5 x 3 factorial, for doses of N-fertilizer (0, 30, 60, 90, 120 kg ha-1) and ways of supplying the nutrient [full condition (100%) at the phenological stage V3 (third expanded leaf); fractionated (70%/30%) at phenological stage V3/V6 (third and sixth expanded leaf) and fractionated (70%/30%) at phenological stage V3/R1 (third expanded leaf and ear differentiation)], in the soybean/wheat and corn/wheat succession systems with high and reduced N-residual release, respectively. More efficient use of nitrogen was obtained based on wheat grain productivity when applied at the full dose at the third expanded leaf stage. The supply of the maximum dose of nitrogen with an expectation of 3 t ha-1 ensures satisfactory productivity with reduced nutrient losses to the environment, especially in unfavorable years for cultivation, regardless of the succession system.

Genet. Mol. Res. 20(3): GMR18903
DOI: 10.4238/gmr18903
Research Article

Avena sativa is the sixth most produced cereal in the world. It is widely used for human consumption. Due to the bromatological quality of its forage, it is used for direct grazing, hay and silage. Due to the large number of interesting characteristics of forage white oats, the selection of unique characteristics becomes difficult and expensive for breeders. In this sense, the use of analysis with multiple characteristics can facilitate the process. Therefore, the objective of this work was to estimate genetic parameters of morphological characteristics, productivity, and quality of forages, as well as to define multiple characteristics that assist in the selection of promising white oat genotypes with forage profile through factor analysis. Field trials were carried out during the agricultural year of 2013 in the municipality of Capão do Leão, RS. The experimental design was in randomized blocks, with treatments arranged in four replications. The treatments corresponded to the genotypes CHIARASUL (G1), FAEM006 (G2), BARBARASUL (G3), BRISASUL, (G4) CGF03006 (G5), CGF07023-1 (G6), CGF07-74 027-1 (G7), CGF07033 (G8), CGF07033-1 (G9), CGF07041 (G10), CGF0705-7 (G11), CGF07060-2 (G12) and CGF07060-3 (G13). The characteristics analyzed were: plant height, leaf area, weight of fresh plants, weight of dry plants, number of tillers and levels of nitrogen, crude protein, phosphorus, potassium, calcium, magnesium, copper, zinc, manganese and iron. The data were submitted to the normality test and to various components of variance. Statistical analyses were performed using Selegen®, SAS® and Genes® software. The white oat genotypes expressed high genetic variability and possibility of selection for leaf area, fresh forage mass, dry forage mass, number of tillers and calcium content. Simultaneously the magnesium content with multiple traits + zinc content, dry matter + fresh mass, nitrogen content + calcium content, crude protein + potassium content and number of tillers, showing potential to select genotypes of interest for genetic improvement.

Genet. Mol. Res. 20(3): GMR18451
DOI: 10.4238/gmr18451