Rodrigo Oliveira DeLima

Potencial genético da população de milho UFV 7 para o melhoramento em Minas Gerais

The objective was to assess the genetic potential of maize population UFV 7 for breeding in Minas Gerais, Brazil. Three experiments were installed with the maize population UFV 7 in the three regions of Minas Gerais, in the harvest of 2006/2007. There was genotype x environment interaction for all characters. It was observed genetic variability for grain yield, plant height and ear height in maize population UFV 7, in the three regions. The Southeast region was where the maize population UFV 7 had the highest parameters. The population UFV 7 presented high grain yield, 9 112kg ha-1 in the Southeast, average grain yield, 6 510kg ha-1 in the West and low, 4 572kg ha-1 in the Central Region. Heritability estimate and CVg / CVe for grain yield were higher than 60% and 1.00, respectively. Grain yield had significant and positive genetic correlation with plant height and ear height, in Western and Central, and the prolificacy in Central and Southeast. For maize population UFV 7 it was conclude that it has potential for extraction of lines in the Central Region; it has the potential for immediate use in the Southeast and for new cycles selection in the Western Region of Minas Gerais. The selection for PG provides an indirect increase in plant height and ear height, in the West and Central.

Factor analysis and SREG GGE biplot for the genotype × environment interaction stratification in maize

The objective of this study was to evaluate the use of SREG GGE biplot methodology and factor analysis to stratify the genotype×environment interaction in maize. Forty-nine early maize hybrids were evaluated in nine environments. The experimental design used was a 7×7 square lattice with two replicates. Each plot consisted of two 5m long rows spaced 0.90m apart. Grain yield data were used to perform the analysis. The results indicated the existence of two mega-environments in the State of Minas Gerais, Brazil, for early maize hybrids. The stratification of the environment by factor analysis was more selective to join the similarity the according with cultivar performance. However, this approach did not identify specific genotype x environment interactions, which is possible through SREG GGE biplot analysis.

Performance of testers with different genetic structure for evaluation of maize inbred lines

The objective of this study was to evaluate four maize testers for identification of superior inbreed lines in testcross. The four testers evaluated are cultivars with narrow or wide genetic base (single-cross hybrids and open pollinated varieties) and two kernel types (flint or dent). SynD and SynF testers are open pollinated varieties with dent and flint kernels, respectively, and FSH and DSH testers are single-cross hybrids with flint and dent kernels, respectively. SynD tester showed the biggest genetic variance among the maize inbreed lines in crosses. The effects of general combining ability (GCA) for lines and specific combining ability (SCA) for lines x testers were significant, whereas GCA effects for testers were not significant. SynD and SynF testers identified the largest number of lines with higher GCA. The DSH and FSH testers showed suitable to identify lines with high SCA. It was concluded that SynD and SynF testers are adequate to identify inbreed lines with high GCA effects, and its possible to identify new lines with high heterotic potential in each one of the four testers.

Genetic diversity and path analysis for nitrogen use efficiency in popcorn inbred lines

Popcorn inbred lines with more efficient nitrogen use are better able to uptake nitrogen from the soil and convert it into higher grain yield, resulting in lower environmental and economic impacts caused by nitrogen fertilization. The objectives of this study were to (i) identify inbred lines superior in nitrogen use (ii) assess the genetic diversity between popcorn inbred lines under high and low N conditions and (iii) investigate the causal effects of several traits in nitrogen use efficiency (NUE). We evaluated 25 popcorn inbred lines under high and low N, and several traits related to NUE and its components were measured. Efficient and inefficient inbred lines under both N levels were identified and can be useful for generating a segregating population for quantitative trait loci mapping. The genetic diversity assessment based on phenotypic traits grouped the inbred lines into four clusters under both N levels, and the efficient inbred lines were grouped together, as were the inefficient lines. The most divergent inbred lines under high N were classified as efficient and intermediate and can be useful to generate a divergent breeding population with a high frequency of favorable genes for NUE. Nitrogen uptake efficiency (NUpE) was considered the most important trait for NUE. To improve the accuracy of selection for NUE, a selection index involving the total root length (TRL), daily growth and NUpE traits under both N levels is recommended, as these traits had high correlations with and direct effects on NUE.

Eficiência na absorção e utilização de nitrogênio e atividade enzimática em genótipos de milho

The aim of this study was to investigate the employment of components of the nitrogen efficiency use (NUE), and of the activities of the nitrate reductase and glutamine synthetase enzymes in the selection of nitrogen use efficient maize genotypes of maize. Ten maize genotypes at V4 stage were evaluated under high and low N. The experiment consisted of a 2 x 10 factorial (two levels of N and ten maize genotypes), in a randomized complete block design with three replicates. The following traits were evaluated: N uptake efficiency (NUpE), N utilization efficiency (NUtE) and N use efficiency (NUE), and activities of the glutamine synthetase (GS) and nitrate reductase (NR) enzymes. For traits which the effect of genotype was significant (p<0.05) in the variance analysis for level of N, the mean were compared using the t test (p<0.05). The indirect gains in NUE and their components with selection over the activities of the enzymes NR and GS were estimated under low N. We conclude that: under high N, NupE is efficient to differentiate nitrogen use efficient maize genotypes; under low N, NupE and NUtE efficient to differentiate nitrogen use efficient maize genotypes, the activity of NR enzyme is not a good physiological parameter for differentiate nitrogen use efficient maize genotypes, and selection over activity of GS enzyme enables the indirect selection of nitrogen use efficient maize genotypes.

Breeding for Water Use Efficiency

Among environmental factors, drought is the principal factor that limits global agricultural production. Many global agricultural regions are already suffering serious problems with water shortage and this scenario suggests that greater efforts are required in the development of alternatives for sustainable agriculture, such as the selection of cultivars that are efficient in the use of water. Water use efficiency (WUE) is the most important component of drought adaptation. In this chapter, WUE will be emphasized because of its greater importance and the possibility of obtaining genotypes that respond to environmental improvement or to the availability of water when it occurs. For this purpose the following topics will be addressed: germplasm, genetic variability, relationship between characteristics, inheritance and maternal effect, oxidative stress, stress induction, selection strategies and breeding methods, and biotechnology applied to the breeding of WUE.

Inferring tropical popcorn gene pools based on molecular and phenotypic data

Studies on tropical popcorn (Zea mays L. ssp. mays) gene pools are still scarce. The objective of this study was to infer tropical popcorn gene pools by employing molecular and phenotypic information. Forty-eight inbred lines and 140 individuals belonging to the Viçosa and Beija-Flor popcorn populations were genotyped using 90 simple sequence repeat (SSR) and 93 single nucleotide polymorphism (SNP) markers, respectively. Grain yield and expansion volume were analyzed for the inbred lines and the hybrids obtained from intra- and interpopulation diallels. The cluster analysis based on SSR markers grouped 46 inbred lines into two groups according to their origin population. Principal coordinate and population structure analyses based on SSR and SNP markers confirmed the results from the clustering. For grain yield, midparent heterosis was greater in the interpopulation hybrids than in the intrapopulation hybrids. The genetic distance did not correlate with the specific combining ability effects and showed a week to intermediate correlation with hybrid performance and midparent heterosis. Based on the results from clustering, population structure, genetic diversity, heterosis and diallel analyses, Viçosa and Beija-Flor populations belong to distinct gene pools. Furthermore, inferring tropical popcorn gene pools might be more efficient if molecular marker and phenotypic data are combined.

Genetic Parameters and Predictive Genetic Gain in Maize with Modified Recurrent Selection Method

El metodo de seleccion recurrente modificado sugiere el uso de una poblacion menos productiva para probar otra poblacion mas productiva y a si misma que difiere del metodo de seleccion recurrente tradicional en que usa una poblacion para testar otra. Los objetivos de este trabajo fueron estimar los componentes geneticos, predecir y evaluar los avances de la ganancia genetica y las poblaciones SynFlint y Syndent de maiz (Zea mays L.) con un metodo modificado de seleccion recurrente. Dos ciclos de recombinacion fueron realizados con 144 S1 progenies por ciclo obtenidas de cruzamiento con SynFlint, generando una poblacion SynFlint x Syndent y otra SynFlint x SynFlint. Las progenies se evaluaron en cinco ambientes en el primer ciclo de seleccion y en tres en el segundo ciclo de seleccion, en un lattice 12 x 12. La variabilidad genetica fue significativa para la altura de la planta y altura de mazorca, peso de mazorca y prolificidad en el primer ciclo de seleccion y en altura de la planta y altura de insercion de mazorca en el segundo ciclo. La intensidad de la seleccion practicada en el primer ciclo acabo con la variabilidad genetica del peso de mazorca y de prolificidad. Se puede concluir que las dos poblaciones de maiz evaluadas no muestran niveles adecuados de variabilidad genetica ni estimaciones de ganancias geneticas predichas para permitir su uso en programas de mejoramiento genetico para obtener lineas e hibridos superiores; y que el metodo modificado de seleccion recurrente es ineficaz para aumentar el rendimiento en la poblacion por si y entre las poblaciones.

Generation mean analysis for nitrogen and phosphorus uptake, utilization, and translocation indexes at vegetative stage in tropical popcorn

Understanding the genetic control of the nitrogen (N) and phosphorus (P) uptake, utilization, and translocation is essential to develop superior popcorn genotypes with high N and P use efficiency. The main objective of this study was to determine the genetic control for N and P uptake, utilization, and translocation efficiency indexes and shoot and root traits under low-N and -P conditions at early vegetative stage in tropical popcorn. We estimated linear and quadratic genetic components from replicated early evaluation (V6 stage) of six generations derived from two crosses involving contrasting inbred lines for N and P uptake and translocation efficiency indexes under low-N and -P conditions. In general, the linear non-additive components were greater than the additive component. Dominance effect was important for increasing N uptake and translocation, while for P uptake and translocation both dominance and epistatic genetic effects were important. For most of the shoot and root traits, dominance and epistatic effects were important as well. Excepting P uptake efficiency, the average degree of dominance indicated partial dominance for several of the measured traits. Efficient direct selection for early N efficiency can be achieved and also provides indirect gains in several shoot and root traits via N uptake. Concerning the early P efficiency, efficient selection can be achieved for P uptake via shoot dry weight and root surface area. Our results evidenced that reciprocal recurrent selection based on early evaluation of progeny might be useful to develop popcorn genotypes with superior N and P efficiency under low-nutrient conditions.

Best linear unbiased prediction for genetic evaluation in reciprocal recurrent selection with popcorn populations

SUMMARY The objective of the present study was to present the theory and application of best linear unbiased prediction (BLUP) in reciprocal recurrent selection (RRS). Seven progeny tests from two RRS programmes with popcorn (Zea mays L. ssp. mays [syn. Zea mays L. ssp. everta (Sturtev.) Zhuk.]) populations were conducted and analysed for expansion volume and grain yield. The interpopulation half- and full-sib family models were fitted using ASReml software. Half-sib selection is equivalent to selection for the general combining ability (GCA) of the common parents. With inbred full-sib progeny and BLUP analysis, it is possible to predict the general and specific combining ability effects. The standard error of prediction of the progeny effect was lower than the standard deviation of the best linear unbiased estimation (BLUE) estimate. For half- and full-sib RRS, the BLUE and BLUP provided highly correlated estimates of progeny genotypic values. The coincidence between selected parents ranged from 64 to 95%. With inbred full-sib progeny, the correlations between the BLUE of progeny genotypic values and the BLUP of GCA effects were lower. Consequently, the coincidence between selected parents was lower, ranging from 0 to 57%. The percentage of common selected inbred progeny based on the BLUE and BLUP of the progeny genotypic value ranged from 57 to 100%.