Claudir Lorencetti

Genetic Basis of Stay-Green Trait in Bread Wheat

ABSTRACT The stay-green trait is responsible for the preservation of green coloration in the stem and leaf, during physiological maturity. It has also been shown to play an important role in the increase of grain size. The knowledge of the inheritance of this trait can constitute valuable information to plant breeders in the developing new wheat (Triti-cum aestivum L.) varieties. This study was conducted in two environments, during the years of 1997 and 1998, to verify the genetic basis of the stay-green trait among crosses of four different genotypes in the field and three in the greenhouse. The analysis was based on three fixed (P1, P2 and F1) and three segregating (F2, BC1F1 and BC2F1) generations. Means and variances were computed for every generation for each cross and the nature of the gene and its effects were estimated. Change in stem color was used as the criterion for the stay-green trait in three phases of development in wheat, based on scores obtained from visual analysis, on a scale of 1 to 10. The results presented in the 2nd observation phase, suggest that the stay-green trait is controlled by only one gene with two alleles and gene activity with high predominance of additive effects and to a lesser degree, a partial dominance for stay green.

Comparações entre medidas de dissimilaridade e estatísticas multivariadas como critérios no direcionamento de hibridações em aveia

Genetic dissimilarity measures are commonly used by plant breeders to identify different genotypes to get desired segregant populations. This study was proposed to establish the relationship between different multivariate techniques to estimate divergence. The experiment was performed during the growing season of 2001, where twelve oat cultivars were tested for seven agronomic traits, using the random blocks experimental design with four replications. Euclidian and Mahalanobis distances showed low correlation (0.529) and when used to build dendrograms did not show similar clustering. The graphic techniques analysis through principal components and canonical variables also showed distinct spreading patterns. However, in spite of the observed discrepancies among the methodology analyzed, it was possible to recognize dissimilar genotypes with high average that can be used with large success probability in selected artificial hybridizations in oats.

Adaptabilidade e estabilidade em aveia em ambientes estratificados

Twenty oat genotypes (Avena sativa L.) were evaluated for grain yield in the crop year of 2001 and 2002 in nine different locations in Parana, Rio Grande do Sul and Sao Paulo states, Brazil. The objectives of this work were to obtain adaptability and stability parameters estimates in favorable and unfavorable environments with and without fungicide application. The methodology of EBERHART & RUSSELL (1966) was applied. The significance for years, genotypes, fungicides and locals indicated a differential behavior of genotypes in favorable and unfavorable environments with and without fungicide application. Data analysis shows that fungicide application and the favorable and unfavorable environment affected intensely the parameters of adaptability (b1) and stability (s2di), indicating that these estimates must be performed in stratified environmental conditions, despite the fact that no ideal biotype was found, as predicted by the adopted model.

Dissimilaridade genética entre genótipos de aveia

Dezoito genotipos de aveia foram testados quanto a dissimilaridade genetica, com e sem o controle de molestias da parte aerea. As variaveis avaliadas foram rendimento de graos desaristados, peso de mil graos, peso do hectolitro, estatura de planta e dias da emergencia a floracao. Foram empregados analises por variaveis canonicas e tecnicas de agrupamento por meio dos metodos de otimizacao de Tocher e o metodo hierarquico do vizinho mais proximo, tendo como medida de dissimilaridade a distância generalizada de Mahalanobis. Pelos resultados, constatou-se significativa dissimilaridade genetica entre os genotipos, indicando a existencia de variabilidade para os caracteres avaliados. O metodo de Tocher e o metodo do vizinho mais proximo permitiram a separacao dos genotipos em grupos distintos, possibilitando a identificacao de futuros genitores que possam ser utilizados em cruzamentos artificiais que produzam progenies com maior heterose. Os caracteres que mais contribuiram para a dissimilaridade genetica foram o peso do hectolitro e a estatura de planta.

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).

Implicações da aplicação de fungicida na adaptabilidade e estabilidade de rendimento de grãos em aveia branca

Twenty oat genotypes (Avena sativa L.) tested in thirteen environments were submitted to adaptability and stability analyses aiming at evaluating the effects of fungicide utilization following the segmented regression model of CRUZ et al. (1989). Fungicide application affected the parameters of adaptability (b 1 ), responsiveness (b1 + b2) and stability ( ) indicating that estimatives must be performed individually in environments with and without fungicide. Fungicide application had a favorable effect on the stability of grain yield, inasmuch as four of the tested genotypes were shown to be stable (UPF 19, UPF 20, OR-3 e OR-4); however, all genotypes revealed instability of grain yield in the absence of fungicide. No tested cultivar showed characteristics of the ideal genotype, as predicted by the adopted model.

Efeito de níveis de severidade e incidência da ferrugem-da-folha e ferrugem-do-colmo no rendimento de linhagens de aveia

Germoplasm introduction represents an alternative to increase oat (Avena sativaL.) variability, favoring selection. The objectives of this study were: a)to select oat lines with high grain yield and adaptation to State conditions; b)to determine the relationship between crown and stem rust with grain yield; c)to estimate the relationship between severity and incidence rules as tools to diagnose disease intensity. Fifty seven oat lines were evaluated for grain yield and other characters. The lines were classified using the mean standard deviation and the data was submitted to correlation and regression analyses. Only three introduced lines looked promising. The correlation between crown rust and grain yield was significant, differently from stem rust. Severity to incidence regression of diseases showed quadratic behaviour, although linear relations were observed in low incidence levels. From disease reaction type, the selected lines are valuable to oat breeding programs. Incidence rule can efficiently replace the severity rule at low epidemic levels, facilitating field diagnostics.

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.

Uma proposta de seleção para caracteres quantitativos e qualitativos em aveia

In oat (Avena sativa L.) techniques that minimize environmental effects on the expression of phenotype and facilitate the identification of high yielding genotypes are useful. Short stature and tolerance to toxic aluminum are important for the development of cultivars with adaptability to marginal areas. Thus, genotypes selected by the honeycomb method, in three different crosses, were subjected to simultaneous tests for aluminum tolerance (Al+3) and insensibility to gibberelic acid (AG3), aiming the identification of superior genotypes. This technique enabled the selection of high yielding, short stature and Al+3 tolerant genotypes and could be applied in plant breeding programs involving cultivated hexaploid oat.

Comparação entre mutagênicos químico e físico em populações de aveia

Hexaploid oat genetic variability was compared in populations treated with physical and chemical mutagens by making a field evaluation of vegetative cycle. Experiments were carried out in two agricultural years in Pelotas, RS (1997/98 and 1998/99). Seeds were irradiated at the UFPel OncoloGy Center, with a dose rate of 0.25Gy min-1. The total absorbed doses for the physical mutagen were 100, 200 and 400Gy and, for the chemical mutagen 0.5, 1.5 and 3.0% per treatment of 1,200 seeds, in each evaluated genotype. A difference in efficiency between mutagens was detected. The physical mutagen was always superior to the chemical mutagen, regardless the generation evaluated, providing a higher increase in the number of phenotypic classes, either leading to a reduction or increase in the number of days between emergence and flowering. The genotypes showed a differential sensitivity to the doses of tested mutagens, indicating a range of treatment efficiency in altering the genetic variability either for early or late vegetative cycle. In general, the results pointed to a decrease in the character vegetative cycle when an increase in the mutagen dose was applied. The study of populations UPF 16 on the doses 100 and 200Gy subjected to treatment with the physical mutagen pointed to a higher degree of genetic divergence and dominance for the character vegetative cycle.