Table of Contents | Genet. Mol. Res. 2021 (4)
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.
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.
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.
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.
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.