Igor Pirez Valério

Seeding density in wheat genotypes as a function of tillering potential

Seeding density adjustments is one of the practices that most influence grain yield, as well as other agronomic traits. Therefore, the objective of this study was to determine the ideal plant stand to achieve the maximum grain yield in genotypes showing differential tillering ability. Also, to establish the associations between the genotypes used with tillering and other agronomically important traits as weight of a thousand grains. Two experiments were conducted in 2005 and 2006 in Capao do Leao, Rio Grande do Sul state, Brazil. Five low (JURITI, BR 18, CEP 29, BR 18 and CD 108) and five high (CD 114, SAFIRA, FIGUEIRA, BRS 177 and UMBU) tillering potential wheat cultivars were tested for two years on a split-plot design. The results indicate the need for recommending cultivars based on more than one year of cultivation, especially when dealing with contrasting genotypes for the trait fertile tillers. Regarding the ideal plant stand, seeding density of low tillering ability genotypes ranges from 417 to 555 seeds m-2, in order to obtain maximum yield and grain weight. On the other hand, for high tillering ability genotypes, the ideal stand ranges from 221 to 422 seeds m-2. These results were year independent. Furthermore, low tillering ability genotypes showed a closer association of number of fertile tillers with grain yield. However, an inverse association was found between number of fertile tillers and weight of a thousand grains.

Morphological, pedigree, and molecular distances and their association with hybrid wheat performance

The objectives of this work were to estimate the genetic distance among wheat genotypes using morphological, pedigree, molecular, and combined morphological and molecular measures, to determine the correlations between these measures, and to evaluate the combining ability of the genotypes. Three generations and two planting designs were studied. Six wheat genotypes were crossed using a diallel design. The F1, F2 and F3generations were evaluated in the field, in the crop seasons of 2003, 2004 and 2005, under spaced plant and full-row planting designs. The estimated general and specific combining abilities of tested hybrids were influenced both by the generation and the planting design. The correlation coefficients among the distance measures and between these measures and genotype performances of different generations for the two planting designs were low to moderate. In order to obtain a more precise estimate of the genetic distance among cultivars and its association with the hybrid performance, more than one generation, planting design, and genetic distance estimation technique should be employed.

Desenvolvimento de afilhos e componentes do rendimento em genótipos de trigo sob diferentes densidades de semeadura

O objetivo deste trabalho foi determinar o padrao de desenvolvimento de afilhos em genotipos de trigo contrastantes para esse carater, em diferentes densidades de semeadura, bem como seus efeitos sobre os componentes do rendimento de graos. O experimento foi conduzido no Municipio de Capao do Leao, RS, em 2006. Dez cultivares de trigo, selecionadas com base na capacidade de afilhamento, foram utilizadas em delineamento de parcelas divididas, com a parcela composta pelo fator cultivar, e as subparcelas pelas densidades de semeadura, com 50, 200, 350, 500 e 650 sementes aptas por metro quadrado. Observou-se que a senescencia de afilhos esteve diretamente relacionada ao potencial de afilhamento dos genotipos. Os genotipos com elevada capacidade de afilhamento apresentaram efeito mais pronunciado da senescencia, com o aumento da densidade de semeadura. O melhor ajuste dos componentes do rendimento foi obtido por meio da adequada densidade de semeadura, que deve ser realizada com base no potencial de afilhamento dos genotipos. Alem disto, o efeito compensatorio de genotipos com reduzido potencial de afilhamento e resultante de maior massa de graos por espiga, em detrimento do numero de espigas por unidade de area.

Seeding density in wheat: the more, the merrier?

Adjustment of seeding schemes is one of the crop management techniques that most influences grain yield components. This work aimed to characterize the potential grain yield and its components in wheat (Triticum aestivum L.) genotypes with contrasting tillering ability under different seeding densities and environments. Five experiments were conducted in split-plot design, each with ten cultivars (main plot), sown in five distinct seeding densities (subplots). Experiments were sown in three locations in southern Brazil in the years 2005, 2006 and 2007. The grain yield per plot and its yield components: number of fertile tillers, weight of 1,000 grains, ear weight and number of grains per ear were evaluated. Genotypes with reduced tillering ability expressed an increase in grain yield with an increase in seeding densities, however showing a reduction in ear weight. The number of grains per ear did not affect grain yield but was highly influenced by seeding densities. The compensatory effect was expressed by the weight of a thousand grains as a function of the experimental conditions in which the genotypes were evaluated, regardless of seeding densities used. Results pointed to differences among cultivars tested in specific locations and years.

Efeito da densidade de semeadura e potencial de afilhamento sobre a adaptabilidade e estabilidade em trigo

The objectives of this work were to determine the grain yield adaptability and stability of ten wheat genotypes (Triticum aestivum L.), contrasting for the character tillering potential, conducted in different seeding densities. The experiments were conducted in the years 2005, 2006 and 2007 in Capao do Leao -RS and in Pato Branco-PR and Ijui-RS in the year 2007. A split-plot design was used considering the genotype as the plot and seeding density as the sub-plot. The seeding densities used were 50, 200, 350, 500 and 650 viable seeds m-2. The analyses of adaptability and stability were performed using the method proposed by Eberhart and Russell. The changes in seeding density and location intensely influenced the adaptability and stability parameters for grain yield. Genotypes adapted to various seeding densities were found (FUNDACEP 29 - except for 650 seeds m-2), as well as those with specific adaptability and a predictable performance only in favorable (CD 114) and unfavorable (CD 108) environments, indicating the need of an adequate fitting of seeding density to the performance predictability for grain yield in wheat.

Aplicability of phenotypic and canonic correlations and path coefficients in the selection of oat genotypes

Indirect selection through traits of higher heritability and of case measurements can result in larger genetic progress compared to using direct selection. This work was performed with the following objectives: (1) to estimative the phenotypic correlations between individual plant grain yield and agronomic traits of importance in the selection of white oat (Avena sativa L.) genotypes; (2) to identify traits that have the higher direct and indirect effects on grain yield; (3) to determine the intensity of association between primary and secondary components of grain yield; and, (4) to evaluate the consistency of these estimates using five oat genotypes crossed in a diallel format. The number of panicles per plant (NPP) showed to be the trait highest correlated with individual plant grain yield (GY) both through single correlations and through direct effects on grain yields. For weight of a thousand grains (WTG) ´ GY, in most crosses there was no detected association, leading to possible troubles for breeders, since larger grains were not associated to higher yield, except for the crosses UPF16 ´ UFRGS17 and UFRGS17 ´ URPel95/015. The trait number of grains per plant (NGP) was directly correlated with GY in all crosses, although the direct effects estimates on GY were negative for the crosses UPF16 ´ UPF18, UPF16 ´ URPel95/015, UPF18 ´ UFRGS17 and UFRGS7 ´ URPel95/015, indicating that correlations are not the main causes altering GY, which could be explained, in the present work, by indirect effects via NPP and mainly via panicle weight (PW).

Variabilidade genética em trigos brasileiros a partir de caracteres componentes da qualidade industrial e produção de grãos

The breeding for wheat bread making quality represents a great opportunity to incorporate commercial value to agricultural products. Wheat has one of the best relationship between end product quality and farmer earnings. Genetic variability among 22 different genotypes based on bread making quality traits and grain yield and the degree of their association was assessed. This research was performed at Centro Agropecuario da Palma experimental field of Universidade Federal de Pelotas, Capao do Leao (RS), Brazil. The results indicated that it is likely the existence of genetic variability for the assessed traits. BRS 208, Rubi and Safira were the best genotypes for breeding programs aiming at high grain yield and bread making quality. Grain yield showed negative correlation with flour protein content. Thus, grain yield improvement can negatively affect protein content. However, the total protein content did not show a significant correlation with gluten strength, suggesting that the protein in the flour is not efficient for predicting bread making quality. Therefore, selection for grain yield can be performed without affecting bread making quality.

Retrocruzamento como uma estratégia de identificar genótipos e desenvolver populações segregantes promissoras em aveia

The objective of this work was to develop the use of backcrosses among elite parental lines and to identify the parents with higher probability of developing superior progenies when used in crossing blocks. The following traits were analyzed: number of panicles per plant and plant grain yield in kg. ha-1. Five oat genotypes (UPF 16, UPF 18, UFRGS 7, UFRGS 17 and URPel 95/015) were crossed on a diallel design not considering reciprocal crosses. F1 populations were obtained from the cross of parental lines. These populations were either backcrossed to obtain the populations BC1P1, BC1P2, BC1P1F2, BC1P2F2, BC2P1 and BC2P2, or selfed to obtain F2 and F3 generations. The F1 hybrids, the F3 populations and the backcrosses were field evaluated during a 2003 winter season. A cross dependent superiority was observed for backcrosses, when compared to the F3 population. An improvement in progeny superiority was observed when the background was increased for the genotypes UPF 16, UFRGS 7 and UFRGS 17. These results were observed in 75% of the crosses, in which those genotypes were present as parental lines UPF 18 and URPEL 95/015 presented less favorable genes to increase grain yield, showing a tendency to reduce the performance of progenies when of their genetic background was increased in the tested combinations.

Padrão de resistência de genótipos de aveia à ferrugem-da-folha na definição de hibridações

Abstract – The objectives of this work were: to determine the resistance/susceptibility pattern of 20 elite oatgenotypes to 40 isolates of Puccinia coronata f. sp. avenae ; to determine the pattern of virulence/avirulence ofisolates collected in three counties of Rio Grande do Sul to the oat genotypes studied; and to indicate potentialparents for the generation of populations with high crown rust resistance. The resistance pattern of oat genotypesand the virulence/avirulence of the fungi were determined by the analysis of the reaction incited by the inoculationof Puccinia coronata f. sp. avenae isolates into seedlings of oat genotypes. The selection of genitors wasbased on the cultivar complementation index proposed in this work. Genotypes expressing resistance to thelarger number of isolates were FAPA6, URS20, UPFA20, CFT1 and FAPA5, while UFRGS15, UPF15, UPF18,UPF19 and UPF16 were susceptible to a higher number of isolates. The following crosses are indicated:FAPA6 x Albasul, URS22 x FAPA6, CFT1 x URPEL15 and CFT1 x UFRGS19.Index terms:

Estimativa do desempenho de progênies F2 e F3 com base no comportamento dos genitores e dos híbridos F1 em aveia

ESTIMATION OF PERFORMANCE OF F2 AND F3 OAT PROGENIES BASED ON THEIR PARENTS AND F1 HYBRIDS Many techniques have been proposed to increase the probability of obtaining superior segregating populations, and major efforts have been invested by researchers worldwide. In this sense, the present work had as objective to verify the efficiency of using parental average, F1 heterosis and heterobeltiosis and the morphological and molecular genetic distance in the prediction of grain yield in oat. Grain yield and its primary components, were measured in F2 and F3 generations originated from the diallel cross involving five parents. Data were obtained from two experiments carried out in the Centro Agropecuario da Palma, in Capao do Leao County, RS, Brazil, in 2002 and 2003. The results indicate that the performance F2 and F3 populations can not be adequately predicted on the basis of the performance of F1 generation. Grain yield of F2 and F3 populations could not be predicted by the genetic distance calculated by morphology or molecular markers. Crosses of high-yielding genotypes did not always yield offsprings with positive transgressive segregation.