Current issues

Table of contents: 2019

Research Article

The production of onion hybrids depends on the development of genetically pure lineages. Successive self-fertilization guarantees obtaining endogenous lines quickly. However, onion undergoes a strong process of inbreeding depression when self-fertilized for several generations, which reduces plant vigor, bulb size and seed production, increasing the cost to produce hybrid seed. An estimate of the genetic distance between genotypes is a way of predicting if genetic variability is being maintained. We evaluated possible negative effects in populations due to self-fertilization, compared to interbreeding between two or three plants. Eleven onion populations in different genetic segregation stages, obtained from generations that already had low or moderate inbreeding levels were included. The populations were from the breeding program of Bayer Vegetable Seeds. In order to assess the agronomic descriptors contribution for the genetic divergence, three types of crossing methods of populations were performed: self-fertilization of plants, crossing between two plants and crossings between three plants, during two consecutive years (2014 and 2015). Morphological differences were detected through dissimilarity measures. The traits bulbs/plot (28.32%), fruit fixation (13.12%) and seed weight/umbel (13.41%) together contributed 54.85% to the divergence of onion genotypes. The crosses between two and three plants provided greater divergence among the genotypes, compared to self-fertilization. Economically important traits such as bulb production per plot, fruit fixation, resistance to disease caused by Alternaria porri (Pleosporaceae) and seed weight per umbel can be measured to assess divergence for appropriate selection of onion lineages among segregant populations.

Genet. Mol. Res. 18(4): GMR18256
DOI: 10.4238/gmr18256
Research Article

We evaluated the performance of 25 soybean genotypes sown in the off-season, to identify the morphological attributes and yield determinants for seed yield in this period. The selected genotypes are commonly used among farmers and were purchased from seed traders. Sowing of soybeans during non-preferential times is common in the northern part of the state of Rio Grande do Sul where it is sown after maize as a late crop. The objective was to evaluate the most suitable genotypes for non-preferential cultivation. The experiment was conducted in the agricultural crop year of 2017/2018 in Tenente Portela - RS; the experimental design was a randomized block containing 25 soybean genotypes arranged in three replicates. Analysis of variance showed significance at 5% probability; there was variability for the first pod insertion height, plant height, number of pods on the main stem, number of pods in the branches, number of branches in the main stem, branch length, number of pods containing one seed, number of pods containing two seeds, number of pods containing three seeds, seed mass per fractional plant due to the pod of origin containing one, two and three seeds and seed yield. The genotypes with the highest seed yield in the off-season period in the Northwest of the state of Rio Grande do Sul were BS 2606 IPRO, BMX Magna RR and M 5947 IPRO. The productivity in kg per hectare was established with taller plants with superiority in the number of pods on the main stem, these pods being formed by two to three viable seeds.

Genet. Mol. Res. 18(4): GMR18230
DOI: 10.4238/gmr18230
Research Article

We evaluated the effects on the nutritional value of the forage of five genotypes of wheat with dual purpose submitted to different sowing densities, as well as different cutting managements. The experiments were carried out in the agricultural crop years of 2013 and 2014 in Frederico Westphalen, RS. The experimental design was a randomized block, organized in a factorial scheme with five genotypes of dual purpose wheat (BRS Tarumã, BRS Umbu, BRS Figueira, BRS Guatambu and BRS 277) x five sowing densities (75, 150, 225, 300 and 375 seeds per square meter) x three cutting managements (one, two and three cuttings), arranged in three replicates. The attributes of interest were obtained through the collection of all plants per experimental unit. These included percentage of crude protein, lipids, neutral detergent fiber and non-fibrous carbohydrates. The bromatological quality of forage from wheat with dual purpose depends on cutting management, genotype and sowing density. The maximum protein fraction and non-fibrous carbohydrates in the forage was obtained at intermediate sowing densities of 300 and 375 seeds per square meter, independent of the genotype for the largest number of cuts.

 

Genet. Mol. Res. 18(4): GMR18211
DOI: 10.4238/gmr18211
Research Article

Passion fruit is a native fruit of tropical America, with Brazil being the world's leading producer and consumer of this fruit, with an estimated annual production of 554,598 Mg, and yield of 13,500 kg.ha-1 Phenotyping through digital images has been used to evaluate morphological characteristics of seeds. Knowledge of the degree of genetic divergence plays an important role, as it assists in the adoption of appropriate strategies for improvement in passion fruit populations. . The objective of this work was to estimate the genetic divergence among full-sibling families of passion fruit through morphophysiological characteristics of seeds using the Ward-Modified Location Model (Ward-MLM) method. Seeds of 98 full-sibling families (FSF) of passion fruit from the breeding program of the Mato Grosso State University were evaluated considering physiological descriptors of seeds, using germination and vigor tests; and morphological descriptors of seeds, using a digital imaging seed analysis device and software. We found that the Ward-MLM method was efficient in detecting genetic divergence using seed morphological and physiological descriptors, simultaneously. The descriptors that contributed the most to the genetic divergence among FSF were those related to seed geometry. This method formed three heterotic groups. Group II had the largest mean emergence speed index (1.106) and seedling emergence percentage (65.8%), and Group III had the largest means of seedling dry weight (4.140 g), radicle length (6.30 mm), germination speed index (2.503), and seed germination percentage (90 %). We conclude that crosses between FSF groups II and III are a good option to improve seed characteristics.

Key words:
Genet. Mol. Res. 18(3): GMR18331
DOI: 10.4238/gmr18331
Research Article

The aim of this study was to perform a genome wide association study for the coefficient of adaptability, the heat tolerance coefficient, age at first calving and calving interval, using 58,868 and 57,482 single nucleotide polymorphisms obtained from 1262 Blanco Orejinegro and 742 Sanmartinero individuals, implementing a single-step-genomic-BLUP (ssGBLUP) methodology. A total of 25 and 11 genomic regions in BON and SM were associated with the traits evaluated. In these regions; several genes involved in the regulation of reproduction and adaptability were identified. Some of them, such as the RPTOR, TM2D1, RAB21 and ACOT13 genes, are involved in the physiological response to heat stress. SLC6A16, TMEM50A, NLRP9, KHDRBS2 and UBE2C are possibly associated to reproductive performance. The results of this study indicate an association between some genomic regions and reproductive and adaptability-related traits in Colombian cattle breeds. Several genes contained in these regions can potentially be used in animal breeding programs to select for adabtability within cattle production systems located in a tropical environment.

 

Genet. Mol. Res. 18(3): GMR18373
DOI: 10.4238/gmr18373
Research Article

Bassia indica is a natural herb of medical and economic importance with a worldwide distribution, including in various regions of Egypt. It is primarily used for healing and is also considered a green fodder and can be used to remediate salty soils. We investigated morphological and germination parameters as well as the karyotype and genetic variation of B. indica by DNA-RAPD. Three samples of this species were collected from various localities in Egypt¸ namely the Northern Coast, the Delta region and Upper Egypt, which each represent different ecosystems. The morphological analysis, which included several traits, showed no significant difference between the localities. However, germination varied among the different populations from the different localities. The chromosomes of this species were found to be diploid, being 2n=18 at all localities. Genetic distances based on DNA-RAPD ranged from 0.13 to 0.31 in the samples from the different localities. A dendrogram based on these distances showed close similarity between the B. indica populations collected from the Delta region and Upper Egypt, indicating that they are closely related to each other, while both these populations are quite distant from those from the Northern Coast. This study provides useful information for the classification, chromosomal identification, and germination of B. indica in these regions that have distinct soils and climate.

Genet. Mol. Res. 18(3): GMR18417
DOI: 10.4238/gmr18417
Research Article

An option into guide selection strategies in soybean breeding programs is to investigate associations between the main traits studied by breeders. A question that is faced is the possible influence of genotype x environment (GE) interactions on correlations among traits. Path analysis allows, in addition to measuring correlation, a more detailed study of cause / effect relationships among traits. We measured the effect of the GE interaction in the association between agronomic traits in soybeans. The experiments were carried out during two crop seasons, in three municipalities of Minas Gerais, Brazil, using a randomized complete blocks design, with 35 treatments. We evaluated number of grains, number of pods (NP), number of grains per pod, grain yield, weight of 100 grains, lodging score, plant height, height of first pod insertion, and full maturity. The data were submitted to variance analysis and path analysis. We also calculated the sum of ranks index in three ways, considering different economic weights. The correlation between grain yield and other traits, as well as direct and indirect effects, varied in magnitude and direction, considering individual and multi-environmental analyses, demonstrating the influence of the GE interaction. For example, considering the individual analysis for Lavras in 2015/16, the correlation between grain yield and NP was -0.0534 and was not significant at the 5% level by the Mantel test, and the direct effect of NP on grain yield was 0.1717, while in the joint analysis of all environments, the correlation between these traits was 0.3674 and was significant, and the direct effect of NP on grain yield was -0.0520.The direct effect as an economic weight in the sum of rank index can be more efficient in selecting cultivars when compared to a simple correlation; this could become a useful strategy for the selection of multiple traits.

Genet. Mol. Res. 18(3): GMR18099
DOI: 10.4238/gmr18099
Research Article

Soybean rust is considered a highly aggressive disease in soybean crops. Most research has focused on obtaining resistant genotypes based on dominant or recessive alleles, which provide vertical resistance. The identification of promising crosses that may be used to develop genotypes with horizontal resistance from IAC 100 may help to increase the longevity of the recommended cultivars. However, this type of resistance is limited by environmental variables that may hinder selection. We ranked crosses based on their response to soybean rust using genetic estimates and predicted gains. It was also an objective to identify quantitative trait loci (QTLs) associated with resistance to soybean rust in two generations derived from the same cross. Eighty-seven F4 progenies from IAC 100 (partial resistance) x BRS Caiapônia (susceptible) cross were field phenotyped. The data divided the DNA samples into two groups for bulked segregant analysis, which was carried out using simple sequence repeat (SSR) primers. A linkage map for the F4 generation was obtained based on 29 SSR markers, which were distributed into nine linkage groups, covering 285.9 cM of the genome. Six QTLs were mapped in four of these groups and two of them were responsible for 39% of the phenotypic variance in resistance to soybean rust. The linkage map generated for the F7 generation was similar to that of the F4 generation, covering 266 cM. Four of the six QTLs mapped in the F4 generation were also identified in the F7 generation, showing that the genomic regions contributing to horizontal resistance to soybean rust are stable.

 

Genet. Mol. Res. 18(3): GMR18249
DOI: 10.4238/gmr18249
Research Article

Dual purpose wheat could be a good alternative for helping overcome the need to import this cereal in Brazil. To achieve this, development of cultivars with high yield is necessary. The contribution of genetics in defining traits is very important for directing breeding programs for the development of cultivars that provide the desired agronomic ideotype. We estimated heritability for 36 characters of agronomic importance in dual-purpose wheat. The inheritable genetic patterns were examined using linear trends, a Euclidean algorithm, factor analysis and artificial neural networks. The study was carried out during the crop seasons of 2011, 2012 and 2013. The experimental design was randomized block, arranged in a factorial scheme with three growing seasons (2011, 2012 and 2013) and five dual-purpose wheat genotypes (BRS Tarumã, BRS Umbu, BRS Figueira, BRS Guatambu and BRS 277) x three cuttings (first cutting, second cutting and third cutting), with three replicates. Deviance analysis or maximum likelihood was significant for the 36 characters. The length of the head of the main plant, plant height before the first second cutting and dry mass of the seedlings showed high variability. The 36 characters expressed linear genetic dependence based on the Euclidean Algorithm; similar to what was found with the Tocher Optimized Clustering and Artificial Neural Networks K-means methods. Similar genetic trends for heritability profiles were obtained with factor analysis and Artificial Neural Networks by the Kohonem method. The use of Artificial Neural Networks through the Kohonem method gave the greatest efficacy in the definition of the genetic profiles needed to develop the recommended agronomic ideotype for the improvement of dual-purpose wheat.

 

Genet. Mol. Res. 18(3): GMR18266
DOI: 10.4238/gmr18266
Research Article

Highly heterotic onion hybrids exhibit high yield and superior post-harvest quality. In general, to develop heterotic hybrids, it is first necessary to develop inbred lines with high genetic divergence and good specific combining ability (SCA). We investigated the correlation between SCA, heterosis, and genetic divergence of inbred onion lines. Two groups of inbred onion lines were used as parentals in a partial (6x5) diallel cross. Group I included six S3 male-sterile lines of the “Super Precoce” pedigree (L4827, L4830, L4833, L4835, L4837, and L4839), and group II included five S2 fertile lines of the “Hiper Precoce” pedigree, Granex type with some inter-crosses (L4741, L4742, L4743, L4744, and L4746). Genetic divergence among the parental lines was estimated on the basis of seven morpho-agronomic characters and 10 inter-simple sequence repeat (ISSR) markers. Pearson and Spearmann correlations between morphology-based genetic dissimilarity, ISSR-based genetic dissimilarity, heterosis, and SCA were evaluated. Five characters (number of leaves, bulb yield, bulb diameter, soluble solids content, and dry mass) accounted for 82.8% of the genetic variation present in the genotypes. The greatest genetic dissimilarity, as indicated by both ISSR data (80.4%) and morpho-agronomic data (92.5%), was calculated for L4742 and L4744, which demonstrated that these onion inbred lines were genetically divergent. Based on estimates of SCA and heterosis, L4742 was identified as the most promising lineage for developing superior onion hybrids. None of the correlations between SCA, heterosis, and genetic dissimilarity (morpho-agronomic or ISSR) were significant, thereby indicating that genetic dissimilarity cannot be used directly to select parental lines or to predict the best crosses for all characters. However, the genetic dissimilarities estimated using morpho-agronomic characters and ISSR profiles were useful for identifying the best crosses for bulb yield and bulb diameter.

Genet. Mol. Res. 18(3): GMR18316
DOI: 10.4238/gmr18316
Research Article

Sweet corn (Zea mays subsp. saccharata) is considered a special vegetable of high nutritional value. One of the barriers encountered by breeders has been a lack of adequate genetic variability of sweet corn, coupled with a need for appropriate methodologies to evaluate the existing genetic diversity. Our objective was to determine the best method to identify promising genotypes to improve sweet corn production. We used data from 181 open-pollinated sweet corn genotypes, cultivated during 2016 and 2017. Multivariate analyses were carried out to determine the genetic dissimilarity between the genotypes, obtaining the matrix of dissimilarity by Euclidean distance. Prior to calculating the distance between matrices, two data standardizations (Z1 and Z2) were performed for comparison. Genetic divergence was analyzed by four distinct hierarchical methods: Unweighted Pair-Group Method Using Arithmetic Averages (UPGMA), Ward, Weighted Pair-Group Method Using Arithmetic Averages (WPGMA) and Single Linkage. Tocher’s optimization method was also used. The Simple Linkage and UPGMA methods presented similar groupings, consistent with breeding program aims and with the highest values of co-phenetic correlation coefficient (CCC). The Ward’s method was not efficient, because it produced several clusters without isolating different genotypes. Furthermore, it was the method with the lowest CCC for both matrices. The standardized Z2 matrix should be avoided, especially when a large number of genetic traits are measured, in order to prevent possible overlapping between traits, a variables with higher standard variations could contribute more to the clustering.

 

Genet. Mol. Res. 18(3): GMR18384
DOI: 10.4238/gmr18384
Brief Note

Type 1 diabetes mellitus (T1D) is considered a polygenic disease that is influenced by environmental factors and autoimmune responses to autoantibodies, resulting in metabolic abnormalities. Tyrosine kinase 2 (TYK2) is involved in type I interferon signaling in beta cells, and TYK2 polymorphism rs2304256 has been associated with T1D. We investigated polymorphism rs2304256 (TYK2) in a case-control study of Euro-Brazilians with T1D manifested during childhood and adulthood. We studied 307 individuals manifesting clinical signs of type 1 diabetes (151 children below 14 years of age and 156 adults with diagnosis after 18 years of age). The control samples consisted of 169 healthy children and 150 healthy adult subjects. T1D groups had inadequate glycemic control because fasting glucose and mean HbA1C concentrations were significantly higher than in the control groups. Real-time PCR with TaqMan® fluorescent probes was applied for genotyping. The studied polymorphisms were in Hardy–Weinberg equilibrium. The minor allele frequency (A-allele) for children in the T1D and control groups was 24.2% (95% CI, 18 - 32) and 23.4% (95% CI, 17 - 30), respectively (P = 0.812), while for adults in the T1D and control groups values were 19.6% (95% CI, 14 - 27) and 24.7% (95% CI, 20 - 35), respectively (P = 0.127). There was no significant difference in genotypes or allelic frequencies of the polymorphism in the groups. The frequency of the minor allele of the polymorphism was similar to that found in other Caucasian populations, and different than that found in Eastern populations. In conclusion, the polymorphism rs2304256 was not associated with T1D in either group.

Genet. Mol. Res. 18(3): GMR18356
DOI: 10.4238/gmr18356
Research Article

The selection of southern rust-resistant genotypes caused by Puccinia polysora (Pucciniaceae) is considered an efficient way to control this disease, which causes high crop losses in popcorn. To help choose adequate cultivars, we examined the combining ability of lines and the agronomic performance of popcorn hybrids for rust resistance. Eight S7 popcorn lines were used, which were crossed in a complete diallel mating scheme, resulting in 56 hybrids. The disease incidence on the whole plant (INC), severity on a leaf of the main ear (SEV), grain yield (GY), popping expansion (PE) and volume of expanded popcorn per hectare (PV) were evaluated. Analysis of variance was performed and the means were grouped by the Scott-Knott algorithm. The analysis diallel was performed by the method of Griffing, using the Diallel I method. The hybrids L76xP8, P8xL70, L77xP8, P8xP1 and L55xL76 stood out with a GY of >3000 kg.ha-1 and PE of >30 mL.g-1. For the traits GY and VP, the non-additive effects were predominant, and the heterosis effects high. For the trait expression of INC, SEV and PE, the additive effects were more relevant. The estimates of general combining ability of lines L70, L61, P1 and L76 were negative for INC and SEV. For commercial cultivation, L77xL76, L76xP1, L77xL70, L76xL70, L70xL76 and L77xP1 are recommended, in view of their excellent agronomic performance and superior resistance to rust.

Genet. Mol. Res. 18(3): GMR18330
DOI: 10.4238/gmr18330
Research Article

The commerce of potted ornamental plants has grown in Brazil, and ornamental pepper stands out due to a profusion of colors and forms, as well as due to its easy cultivation. However, few studies have been carried out with ornamental pepper for genetic improvement of fruit production, plant size and precocity. Thus, in order to conduct a genetic improvement program, we evaluated the general and specific combining abilities, as well as reciprocal effects in a complete diallel with eight progenitors and 56 ornamental pepper hybrids. Thirteen features related to plant and fruits were evaluated. Significant variation was observed among parents and ornamental pepper hybrids by Scott-Knott criterion at 1% probability. There was predominance of additive effects in control of all characteristics except for fruit mass, since the ratio between quadratic components of the general combining ability and the specific combining ability was close to or greater than one. Reciprocal effects were highly significant for all traits, except for days to flowering and fruiting. The predominance of overall combining ability for most features suggests that simple genetic improvement methods, such as the pedigree method, can be successfully used. Based on good classification of UFSJ 1 and UFSJ 6 progenitors in relation to specific combining abilities, favorable reciprocal effects for at least three characteristics simultaneously and at least one of the parents with good general combining ability, UFSJ 4 X UFSJ 1 and UFSJ 6 X UFSJ 1 hybrids were recommended for ornamental cultivation purposes.

Genet. Mol. Res. 18(3): GMR18415
DOI: 10.4238/gmr18415
Research Article

Mate (Ilex paraguariensis) leaves are popular for consumption as an infusion, which provides various health benefits due to its nutraceutical properties. Leaf samples oxidize after harvesting, requiring special handling to avoid DNA damage or degradation by enzymatic or oxidative activities. The objectives of this work were to evaluate several methods for sample storage and DNA extraction to identify practical and efficient protocols to guarantee the DNA quantity and integrity for molecular studies of mate. Total DNA was extracted from fresh leaves and compared with DNA extracted from leaves stored in silica gel at room temperature for 14 days or in CTAB (cetyltrimethylammonium bromide) buffer. The leaves were cleaned with absorbent paper and stored in 50 mL Falcon tubes containing approximately 25 g of silica gel or in 2 mL Eppendorf tubes containing approximately 1 mL of CTAB buffer. Samples treated with silica gel were stored at room temperature for 14 days, and the ones with CTAB buffer were stored either at 4°C for 14 and 90 days or at room temperature for 90 days. The DNA was quantified using a Nanodrop spectrophotometer and agarose gel electrophoresis. DNA purity (with regard to the presence of enzyme inhibitors) was tested by PCR amplification of fragments of the plastid gene, trnL-trnF. Samples of mate leaves can be stored on silica gel or in CTAB buffer for up to 90 days at room temperature without reduction in DNA quality. Samples stored in CTAB buffer can be refrigerated at 4ºC to minimize oxidation of phenolic compounds. The improved methods for sample storage and DNA extraction with CTAB maintain quantity and integrity for conducting molecular studies of mate.

Genet. Mol. Res. 18(3): GMR18390
DOI: 10.4238/gmr18390

Pages