Luiz Carlos Federizzi

Correlation and path analysis of yield and its components and plant traits in wheat

This study was aimed to characterize yield components and plant traits related to grain yield. Correlation and path analysis were carried out in wheat genotypes grown under irrigated and non-irrigated field conditions. In the path coefficient analysis, grain yield represented the dependent variable and the number of spikes m-2, number of grains spike-1, kernel weight, days to anthesis, above-ground biomass m-2 and plant height were the independent ones. In both years, periods without rain occurred from early milk to grain ripening and from flag leaf sheath opening to grain ripening for first and second sowing dates, respectively. Character associations were similar in both water regimes. Grain yield showed positive phenotypic correlation with above-ground biomass, number of spikes m-2 and number of grains per spike. Path analysis revealed positive direct effect and moderate correlation of number of spike m-2 and number of grains per spike with grain yield. These results indicated that the number of spikes m-2 and the number of grains per spike followed by the above-ground biomass were the traits related to higher grain yield, under irrigated and late season water stress conditions.

Inheritance of aluminum tolerance and its effects on grain yield and grain quality in oats (Avena sativa L.)

SummaryAluminum toxicity due to the cation Al+3 is a major factor limiting yields in acid soils. Wide genetic variability to aluminum tolerance is found in oat genotypes. The objectives of this study were to determine the number of genes controlling aluminum tolerance in oats and to verify if any detrimental effects were present of the aluminum tolerance genes on grain yield and grain quality in Al+3free soils. Aluminum tolerance was estimated as the average regrowth of the main root after exposure to toxic levels of Al+3 in a hydroponic solution under controlled conditions. The number of genes controlling that trait was estimated from the distribution of the average root regrowth frequencies in a population of 333 recombinant inbred lines (RILs) in generations F5:6 and F5:7. The effects on grain yield and grain quality were assessed in a subpopulation of 162 RILs chosen based on their aluminum tolerance response. Aluminum tolerance in the evaluated population was controlled by one dominant major gene with the tolerant genotypes carying AlaAla and the sensitive ones alaala alleles. No detrimental effects of the Ala allele on grain yield or grain quality were detected.

Inheritance of rice cold tolerance at the germination stage

Cold tolerance during germination is important for ensuring fast and uniform establishment of a rice crop early in the season. However, evaluation of this trait under field conditions is limited by environmental variation, which makes it difficult to identify genetically superior lines. Evaluation of cold tolerance under controlled temperature conditions may be performed by assessing percentage of reduction in coleoptile length and coleoptile growth. Our study determined the inheritance and heritability of cold tolerance at the germination stage in crosses between six rice genotypes. Diallel analysis showed that while both additive and non-additive gene action were involved, the non-additive action was relatively more important for percentage of reduction in coleoptile length and coleoptile growth. Our data shows that genotype Quilla 66304 would be the best parent in crosses aimed at increasing cold tolerance at the germination stage in rice due to its high general combining ability for both percentage of reduction in coleoptile length and coleoptile growth. Generation mean analysis was also performed for coleoptile growth in six cold-sensitive x cold-tolerant crosses and proved that non-additive effects were due to dominance and epistatic interactions. Though broad sense heritability values were high, the relative importance of the non-additive effects suggests that selection should be applied in advanced generations of the breeding program.

Molecular mapping and identification of QTL's associated to oat crown rust partial resistance

SummaryMolecular mapping is a promising strategy for studying and understanding traits with complex genetic control, such as partial resistance to oat crown rust. The objectives of this research were to develop molecular maps from the progenies of the cross UFRGS7 (susceptible) × UFRGS910906 (partially resistant) and to identify QTLs (quantitative trait loci) associated to partial resistance to oat crown rust in two generations of that population.DNA of 86 genotypes of the F2 and 90 genotypes of the F6 UFRGS7 × UFRGS910906 population were used to generate AFLP markers. Molecular maps were constructed using Mapmaker Exp. 3.0 and QTLs for partial resistance to oat crown rust were identified with Mapmaker/QTL software. Five hundred and fifty seven markers in the F2 and 243 markers in the F6 generations were identified. The F2 map integrated 250 markers in 37 linkage groups. The F6 map integrated 86 markers in 17 linkage groups.Five QTLs were identified for partial resistance to oat crown rust in the F2 generation and three QTLs in the F6. The QTL identified on F6 through the PaaaMctt340 AFLP marker showed consistency across two environments and two generations (F4 and F6), and appear to have potential for marker-assisted selection in oat.

Características de plantas de soja que conferem habilidade competitiva com plantas daninhas

In order to identify morphological characteristics in soybean plants that define greater competitive ability against weeds, two experiments were carried out. The first experiment was installed in Cruz Alta, RS, where soybean competed against forage radish (Raphanus sativus), and the other in Eldorado do Sul, RS, where the crop competed against beggar ticks (Bidens spp.) and arrow leaf sida (Sida rhombifolia). Results multiple linear regression and correlation analysis demonstrated that soybean plants holding with higher stem dry matter of (including leaves) at 45 days after emergency, higher dry matter of shoot at 60 days after emergency, and greater grain yield, granted superior competitiveness of soybean with forage radish. When competitors were weeds hairy beggarticks and arrowleaf sida, soybean stem dry matter (with the leaves), soil coverage by crop canopy, and grain yield, arose as the traits that conferred greater competitive ability to the crop. Plant height, branch number and branch length have also contributed for higher competition ability in soybean.

Rice cold tolerance at the reproductive stage in a controlled environment

A tolerância do arroz (Oryza sativa L.) ao frio no periodo reprodutivo e importante para garantir alto rendimento em ambientes com temperatura baixa. No entanto, a selecao em condicoes de campo nao permite identificar fontes adequadas de tolerância e limita a selecao de linhas segregantes devido a temperatura variavel. Este trabalho teve por objetivo definir uma metodologia capaz de distinguir genotipos de arroz quanto a sua tolerância ao frio no periodo reprodutivo quando avaliados sob temperatura controlada. O efeito do frio foi investigado em seis genotipos de arroz submetidos a 17°C por periodos variaveis de tempo (tres, cinco, sete e dez dias) em dois estadios do periodo reprodutivo (microsporogenese e antese). A tolerância ao frio foi avaliada por meio da porcentagem de reducao na exercao da panicula e na fertilidade de espiguetas. O resultados indicaram que avaliar a tolerância ao frio por meio da reducao na exercao da panicula nao permitiu separar genotipos tolerantes ao frio de genotipos sensiveis e, quando avaliada por meio da reducao na fertilidade de espiguetas, no minimo sete dias foram necessarios para diferenciar os genotipos quanto a tolerância ao frio. Eles foram mais sensiveis ao frio na antese que na microsporogenese e, como estes estadios foram altamente correlacionados, a selecao sob frio poderia ser feita somente neste estadio, que e de mais facil determinacao. Logo, a tolerância do arroz ao frio no periodo reprodutivo pode ser avaliada por meio da reducao na fertilidade de espiguetas devido a temperatura baixa (17°C) aplicada por sete dias no estadio de antese.

Resistência quantitativa à ferrugem da folha em genótipos de aveia branca: I - Caracterização da reação em condições de campo

Quantitative resistance to crown rust in white oat genotypes: I – Characterization of reaction in field conditions Among diseases that attack oat (Avena sativa) crop, crown rust, caused by Puccinia coronata f. sp. avenae, has been the most destructive, being responsible for a decrease in the quality and yield of grains. Control through qualitative resistance has been restricted by the capacity of the pathogen to overcome this resistance type. Seeking an alternative strategy for disease control, 31 white oat genotypes were investigated for the occurrence of quantitative resistance. Trials were accomplished from 1996 to 2000, in the Agronomic Experimental Station of UFRGS, in Eldorado do Sul, RS, Brazil. Disease progress was evaluated in the field for three years, and some genotypes were tested for five years. Weekly evaluations of rust severity in each plot were performed, providing data from which to determine the disease progress curves, and calculate the area under the disease progress curve (AUDPC), and the rate of development of disease (r). There was great variability among genotypes for all the years in regard to rust reaction, allowing the genotypes to be classified in four groups: resistant, moderately resistant, moderately susceptible and susceptible. The first two groups have good levels of quantitative resistance and can be used in the future as parents in breeding programs.

Grain yield stability of wheat genotypes under irrigated and non-irrigated conditions

ABSTRACT Analyses of genotype by environment interactions were carried out for wheat genotypes grown under irrigated andnon-irrigated field conditions, in two sowing dates during three years. The linear regression method was used toanalyze the stability of grain yield. Genotype by environment interactions was observed for grain yield in all groupsof environments. Nesser was the most productive and stable genotype in all groups of environments, followed byIAPAR 17-Caete. In the late sowing, better yield performances were observed for the cultivars OCEPAR 7-Batuira,IAPAR 17-Caete and Nesser, under irrigated condition, and Nesser and IAPAR 28-Igapo, under non-irrigatedcondition. The results indicated that Nesser gave high grain yield with superior adaptability and stability, andcould thus be considered as the most suitable genotype for late sowing and water stress condition at the end ofplant cycle. Key words: Drought tolerance, genotype by environment interaction, water stress * Auth or f cr espond n

Relação entre distância geográfica e variabilidade genética de uma população de Bidens spp. com resistência aos herbicidas inibidores de ALS

Weed species present high genetic variability among plants within a population and show potential to adapt to control tactics. Seeds of Bidens spp. (BIDSS) were collected in a 60 ha rectangular area, in a property located in Almirante Tamandare do Sul, RS, with suspected ALS resistance, and cultivated with soybean during approximately 20 years. The objectives of this work were to evaluate the genetic variability of accesses of Bidens spp. collected in only one property, to verify resistance dispersion and to determine the relation between the coefficient of genetic similarity and the geographic distance among accesses of the same population. The area was divided into 100 geo-referenced points of seed samplings, among which only 40 points had BIDSS plants. These seeds had been placed in plastic pots with capacity of 300 mL and when seedlings presented two leaves, they were sprayed with chlorimuron at a dose of 200 of g ha-1 for resistance confirmation. DNA extraction was conducted according to the literature protocols. Twenty plants from each sampled site were used for the formation of DNA bulk. Twenty and six primers of the operon kit were also used. The BIDSS accesses presented great genetic variability within the population. RAPD analysis did not allow the separation of the species Bidens pilosa and Bidens subalternans. The resistance to the ALS inhibitors was spread in all the sampled area inside the property. No relation was verified between geographic distance and genetic similarity, suggesting no founder effect occurred in the area.

Resistência Quantitativa à Ferrugem da Folha em Genótipos de Aveia Branca: II - Avaliação de Componentes de Resistência*

Quantitative resistance to crown rust in white oat genotypes: II - Evaluation of resistance components The use of quantitative resistance as a form to control oat (Avena sativa) crown rust can be a viable alternative, once there is differentiated reaction among oat genotypes in field, which shows great variation. The slow disease progress observed in the field is the result of combined effects of resistance components as low infection efficiency, longer latent period, low number of spores per pustule and little pustules size. This work was accomplished in 1999 and 2000, and its objective was to quantify the resistance components above mentioned in 31 white oat genotypes. The reaction of these genotypes was evaluated in the field, from 1996 to 2000, and they were classified in four groups. Evaluation of resistance components was accomplished in seedlings and adult plants maintained in controlled conditions, and the last two components were also quantified in leaves collected in the field trials. Genotypes showed variability for all measured characteristics, except for latent period in seedlings, and those genotypes classified as resistant in the field presented the best combination of desirable components.