Rodrigo Rodrigues Matiello

Resistência das plantas a moléstias fúngicas

Plant resistance to fungic diseases is due to their genetic constitution and environmental factors. In breeding programs, one of the main objectives is to obtain high grainyield potenlial plants with resistance to the prevalent diseases. Knowledge of genetic basis of resistance is importam to increase selection efficiency and due to the wide variability of fungi there is the necessity of using different strategies to reduce the probability of pathogen estabtishment in crops.

Controle genético da resistência à mancha-de-Phaeosphaeria em milho

The Phaeosphaeria leaf spot, of ample occurrence in Brazil, has been causing an expressive reduction in the corn yield in the country. Thus, the development of resistant hybrids to this disease is one of the main objectives of corn breeding programs. Information about the genetic control of resistance to the disease is necessary so that the programs can be efficient. The main goal of this study was to determine the genetic control of resistance to the Phaeosphaeria leaf spot in maize through the assessment of the generation means from two crossing between a resistant inbred line (DAS95 or DAS72) with a susceptible line (DAS21) under natural infection conditions of the disease. The experiment was carried out in Indianopolis (MG) in two sowen dates, October and November, 2000. The randomized blocks design with three repetitions was utilized. The evaluation to resistance was performed thirty days after the flowering using a diagrammatic scale of percentage of the total foliar tissue of the plant affected by the disease. Disease severity means of parental lines and generations F1, F2, RCP1 and RCP2 were analysed according to the model by MATHER & JINKS (1971). Genetic variation due to additive effects varied from 73% to 84% whilst dominant effects ranged from 13% to 23%. In both studied population, the predominance of gene additive over dominant effects was evidented. The inheritance values were high, varying from 61% to 88%. These results indicate favourable conditions to develop new resistance lines to Phaeosphaeria leaf spot with the studied populations.

Inheritance of resistance to anthracnose stalk rot (Colletotrichum graminicola) in tropical maize inbred lines

applied into the stalk. Internal lesion length was directly measured by opening the stalk thirty days after inoculation. Results indicated contrasting modes of inheritance. In one population, dominant gene effects predominated. Besides, additive x dominant and additive x additive interactions were also found. Intermediate values of heritability indicated a complex resistance inheritance probably conditioned by several genes of small effects. An additive-dominant genetic model sufficed to explain the varia tion in the second population, where additive gene effects predominated. Few genes of major effects control disease resistance in this cross. Heterosis widely differed between populations, which can be attributed to the genetic background of the parental resistant lines.

Comparison of yield damage of tropical maize hybrids caused by anthracnose stalk rot

The objective of this study was to estimate the reduction in yield caused by Colletotrichum graminicola in resistant and susceptible maize hybrids inoculated at different stages of development. Two trials were conducted in different environmental conditions in a randomized block design with treatments arranged as a 2 × 5 factorial scheme and three replications. Treatments consisted of two hybrids (H8664, resistant and H8621, susceptible) inoculated at three growing stages (8-leaf, 12-leaf and tasseling stage). Internal lesion length, adjusted yield, and yield components (length, diameter and ear weight) were evaluated 120 days after emergence. Significant differences in yield and ear weight were detected in the susceptible hybrid inoculated at the earliest stage: yield was reduced by 16.1 and 20.2% in the first and second experiment, respectively. Although lesion length in the susceptible hybrid was approximately three times greater than in the resistant, there were no significant differences in lesion length among treatments for each hybrid. However, there were differences in the number of dead plants and ear weight. It is suggested that damage caused by early infection with C. graminicola results mainly from plant death and reduction in ear weigh rather than from the extent of colonization of the stalk.

Characterization for plant height and flowering date in the biological species oat

4 ABSTRACT - The use of wild oat races in artificial hybridization with cultivated oat ( Avena sativa L.) has been used as a way of increasing the variability. This work aimed to identify the variability for plant height and flowering date of groups of cultivated oat genotypes, wild introductions of A. fatua L. and segregating populations of natural crosses between A. sativa and A. fatua. Wide genetic variability was observed for both traits in the groups and between them. The wild group of A. fatua L. showed high plants with early maturity, but in the segregating group there was reduced plant height and early maturity. The wild introductions of A. fatua L. studied in this work can be used in oat breeding programs to increase genetic variability by transferring specific characters into the cultivated germ plasm.

Variabilidade genética para teor de proteína bruta em grãos de aveia

The increased use of oat grains as human food has stimulated plant breeders to select genotypes with high grain quality. This work aimed to identify and characterize genetic variability for total grain protein in cultivated oat and introductions of A. fatua L., A. sterilis L. and hybrid populations from A. sativa L. x A. sterilis L.. The results showed a large genetic variability for the trait in the studied groups. Differences among cultivated oat genotypes may be attributed to different genetic constitution. A. sterilis L. group showed high protein content specially with the introduction of I-325. Genotypes from A. fatua L. showed similar low levels of protein probably because the narrow range of regions sampled in this study. Some hybrids from A. sativa L. x A. sterilis L. showed high protein content and acceptable agronomic traits.

Progeny evaluation for resistance to Phaeosphaeria leaf spot in tropical maize

Abstract Maize breeding programmes in Brazil and elsewhere seek reliable methods to identify genotypes resistant to Phaeosphaeria leaf spot. The area under the disease progress curve (AUDPC) is an accurate method to evaluate the severity of foliar diseases. However, at least three data points are required to calculate the AUDPC, which is unfeasible when there are thousands of genotypes to be assessed. The aim of this work was to estimate the heritability of disease resistance, evaluate disease severity at different times using a nine-point scale in comparison to the AUDPC, and establish the most suitable phenological period for disease assessment. A repeated experiment was conducted in a 11 × 11 lattice experimental design with three replications. Disease assessments were carried out at flowering, 15 and 30 days post-anthesis for the parental lines DS95, DAS21, the F1 generation and 118 F2:3 progenies. Then, the AUDPC was obtained and results compared with the single-point evaluations used to calculate it. Individual and joint analyses of variance were conducted to obtain heritabiliy estimates. The assessments performed after the flowering stage gave higher estimates of heritability and correlation with AUDPC. We concluded that one assessment between the 15th and 30th day after flowering could provide enough information to distinguish maize genotypes for their resistance to Phaeosphaeria leaf spot under tropical conditions.

Variabilidade genética para peso de grão e número deespiguetas por panícula em Avena sativa l. e Avena fatua l.

Raising oat grain yield has been one of the main goals of breeding programs. The search for genetic variability in yield components is considered a strategy to increase yield potential. The present study was done aiming to identify genetic variability for morpho-physiological traits (grain weight and number of spikelet /panicle) in cultivated oat genotypes (Avena sativa L.), wild introductions of A. fatua L. and natural hybrid populations of A. sativa L. x A. fatua L. Wide genetic variability was detected among groups and within them for the evaluated traits. Genotypes in the cultivated group (Avena sativa L.) revealed a higher grain weight and low number of spikelet/panicle. A. fatua L. wild introductions showed low grain weight and low number spikelet/panicle. However, some hybrid F2 populations revealed high grain weight and low spikelet number/panicle, being able to be used in the breeding program.

Dissimilaridade genética e definição de grupos de recombinação em progênies de meios-irmãos de milho-verde

The present study aimed to estimate the genetic divergence among corn half-sib progenies seeking to direct recombination between contrasting and superior progenies for green corn production. Ninety-six progenies were evaluated in a randomized block design with 3 replications, and 18 characteristics associated with agronomic adaptation and green corn yield were measured. The genetic divergence was estimated using generalized square Mahalanobis distance and the progenies grouped by UPGMA and Tocher’s methods. The joint analysis of variance showed genetic variability among the progenies for the characteristics evaluated. The UPGMA method was more sensitive than Tocher’s, since it led to the formation of 11 groups genetically dissimilar compared to the 5 ones of Tocher’s method. The grouping allowed to identify superior and contrasting progenies for green corn production. The recombination of these progenies allows increasing genetic variability and the frequency of alleles favorable to the green corn production.Bragantia, Campinas, v. 75, n. 4, p.401-410, 2016 AbstrAct: The present study aimed to estimate the genetic divergence among corn half-sib progenies seeking to direct recombination between contrasting and superior progenies for green corn production. Ninety-six progenies were evaluated in a randomized block design with 3 replications, and 18 characteristics associated with agronomic adaptation and green corn yield were measured. The genetic divergence was estimated using generalized square Mahalanobis distance and the progenies grouped by UPGMA and Tocher’s methods. The joint analysis PlAnt breeding Article