Current issues

Table of contents: 2021

Research Article

There is a lack of information regarding variables that regulate the expression of the yield potential of maize. We studied yield components of maize under different arrangements on field, in the southwest region of the state of Goiás, Brazil. The soil of the experimental area is classified as Typic Orthotic. The experimental design was randomized blocks, in a 9x2 factorial scheme, with nine maize hybrids [30F53, 30F35, P3630, P3898, P3779, AG7098, DKB 310, CD 3612 and SHS 7990] and two spatial arrangements (single rows (45x45 cm) and twin rows (45x90x45 cm), with four replicates. The seeding was made with a one row sowing machine, and soil fertilizing carried out according to technical recommendations. Pest and weed control was employed when required, using an integrated management. The results were submitted to variance analysis, using a means comparison by Scott-Knot test and by multivariate models. The results of the interactions of maize hybrids and spatial arrangements were significant for all the variables with exception of the foliar area index. There were differences in correlations between the variables, with distinct canonical correlations and cultivar groupings. The maize hybrids DKB310 and P3839 stood out, showing satisfactory yield in both spatial arrangements. The modeling of spatial arrangements influenced the behavior of maize hybrids, especially DKB310 and P3898, which showed satisfactory yields in both spatial arrangements.

Key words:
Genet. Mol. Res. 20(1): GMR18425
DOI: 10.4238/gmr18425
Research Article

Polymorphisms of the transcription factor 7–like 2 (TCF7L2) gene have been associated with susceptibility to type 2 diabetes (T2D) in various ethnic populations, but have not been previously studied in a Nigerian population. We investigated the relationship between the TCF7L2 rs12255372 (G/T) polymorphism and type 2 diabetes (T2D) in a Nigerian population. This was a preliminary case–control study that included 73 T2D patients and 75 non-diabetic (ND) controls. Following blood collection, fasting blood glucose (FBG), triglyceride (TG), total cholesterol (TC), high density lipoprotein-cholesterol (HDL-c) and low density lipoprotein-cholesterol (LDL-c) were assayed. PCR-Restriction Fragment Length Polymorphism (RFLP) was employed to molecularly genotype for the TCF7L2 G/T polymorphism using the MluCI restriction enzyme. The GG homozygote genotype was more frequent in ND controls (38.5%) than in T2D patients (23%) while the TT genotype was more frequent in T2D patients (25.7%) than in ND controls (11.5%). Thus, the TCF7L2 G/T polymorphism was associated (P < 0.05) with T2D. The recessive model showed the greatest risk of T2D when the TT genotype was compared to the GX (GG+GT) genotype (odds ratio (OR): 3.91; 95% confidence interval (CI): 1.93-7.96, P < 0.001). The FBG and HDL-c were significantly different (P < 0.05) in subjects with the mutant (GT and TT) genotypes compared to the GG genotype. In conclusion, the TCF7L2 G/T polymorphism was associated with increased risk of T2D in a Nigerian population. This variant could affect pathophysiological markers associated with risk of T2D. Further studies are needed in other populations in Nigeria to confirm the effects of this polymorphism on pathophysiological markers of T2D.

Genet. Mol. Res. 20(1): GMR18662
DOI: 10.4238/gmr18662
Research Article

The woodiness disease induced by the Cowpea aphid-borne mosaic virus (CABMV) is regarded as a limiting factor for passion fruit production. We estimated genetic parameters for resistance and agronomic performance-related traits and selected genotypes resistant to CABMV in segregating populations of passion fruit. The experiment was a randomized-block design with four replicates, consisting of six full-sibling first backcross genotype families, in which 319 genotypes were evaluated. The disease symptoms were evaluated based on spontaneous occurrence of CABMV, using a scale of scores in young leaves, plant and fruits. Based on these scores, we estimated the area under the disease progress curve (MAUDPC). Agronomic traits were also assessed: fruit weight per plant and number of fruits per plant. The variance components and genetic value of each genotype were estimated for each variable via mixed models. The MAUDPC values ranged from 401.25 to 1192.5, indicating considerable genetic variability. The high individual narrow-sense heritability value for the MAUDPC trait (0.95) indicates the possibility of genotypic selection within CABMV-resistant families. For the production-related traits, even with low heritability values, it was possible to obtain genetic gains in individual selection, which ranged from 4.99 to 6.24% for fruit weight and 22.64 to 28.70% for number of fruits. The genotypes chosen to compose the next backcross generation should be selected based on resistance to CABMV, which is the main objective of the program, since agronomic traits can be recovered from backcrosses. Of the 30 individuals ranked for CABMV tolerance, genotypes 501, 506, and 597 were selected to compose the next generation of backcrosses. These had the lowest values for MAUDPC.

Genet. Mol. Res. 20(1): GMR18668
DOI: 10.4238/gmr18668
Research Article

Knowledge of lactation curves in dairy cattle is essential for understanding the animal production in milk production systems. Genomic prediction of lactation curves represents the genetic pattern of milk production of the animals in the herd. In this context, we made genomic predictions of lactation curves through genome-wide selection (GWS) to characterize the genetic pattern of lactation traits in Girolando cattle based on parameters estimated by nonlinear mixed effects (NLME) models. Data of 1,822 milk control records from 226 Girolando animals genotyped for 37,673 single nucleotide polymorphisms were analyzed. Nine NLME models were compared to identify the equation with the best fit. The lactation traits estimated by the best model were submitted to GWS analysis, using the Bayesian LASSO method. Then, based on the genomic estimated breeding values (GEBVs) obtained, genomic predictions of lactation curves were constructed, and the genetic parameters were calculated. Wood's equation showed the best fit among the evaluated models. Heritabilities ranged from 0.09 to 0.29 for the seven lactation variables (initial production, rates of increase and decline, lactation peak, time to peak yield, persistence and total production). The correlations among GEBVs ranged from -0.85 to 0.98. The concordances between the best animals selected according to the selected traits were greater when the correlations between GEBVs for these traits were also high. Consequently, the methodology allowed us to identify the best nonlinear model and to construct the genetic lactation curves of a Girolando cattle population, as well as to assess the differences between animals and the association between lactation variables.

Genet. Mol. Res. 20(1): GMR18691
DOI: 10.4238/gmr18691
Research Article

Peach is a temperate fruit species that is cultivated under various edaphoclimatic conditions all over the world. In Brazil, in the early 1950s, peaches were planted only in São Paulo state and in the Southern states, and the harvest period was restricted to 15 days. Currently, mainly due to peach breeding programs, it is cultivated in subtropical areas and even in high altitude tropical areas, with a harvest period of over 100 days. Knowledge of genetic, phenotypic and environmental parameters that influence characters of economic importance is crucial for guiding breeding programs. The objectives of this study were to estimate the heritability of phenological characters, to evaluate their distribution within populations, to test the possible existence of maternal effect and to evaluate the relationship of these traits with brown rot incidence (Monilinia fructicola). The study was performed in Pelotas, RS, Brazil during 2015-2016 to 2017-2018 seasons. Sixteen first generation (F1) progenies were evaluated, 10 of them being reciprocal crosses. All genotypes were cultivated in the same area, under the same cultural practices (without fungicide application). Full bloom was considered when more than 50% of flowers were open, and the harvest, when more than 10 fruits reached commercial maturity, the fruit development period being calculated by the difference between full bloom and harvest dates. Brown rot incidence was estimated by the percentage of fruits with symptoms. Broad-sense heritability estimates for full bloom date, harvest date, and fruit development period were high (95 to 98%), and narrow-sense heritabilities were medium to high (65 to 72%). A segregation study of these traits suggests a maternal effect on their heritability, mainly for full bloom and harvest date. The three phenological characters were significantly correlated, and only harvest date had a negative and significant correlation (-0.12) with brown rot incidence.

Genet. Mol. Res. 20(1): GMR18684
DOI: 10.4238/gmr18684