Jose Fernandes Barbosa Neto

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.

Combining ability of twelve maize populations

Genetic progress depends on germplasm quality and breeding methods. Twelve maize popu- lations and their crosses were evaluated to estimate combining ability and potential to be included as source populations in breeding programs. Plant height, point of insertion of the first ear, number of ears per plant, number of grains per ear, root and stalk lodging and grain yield were studied in two locations in Brazil, during the 1997/98 season. Genotype sum of squares was divided into general (GCA) and specific (SCA) combining ability. Results indicated the existence of genetic divergence for all traits analyzed, where additive effects were predominant. The high heterosis levels observed, mainly in Xanxere, suggested the environmental influence on the manifestation of this genetic phenomenon. Populations revealed potential to be used in breeding programs; however, those more intensively sub- mitted to selection could provide larger genetic progress, showing the importance of population im- provement for the increment of the heterosis in maize.

TOLERÂNCIA AO ALUMÍNIO EM PLÂNTULAS DE MILHO

A selecao para tolerância ao aluminio e complicada pela desuniformidade natural dos solos e pela dificuldade de avaliar danos na raiz. Assim sendo, e importante desenvolver metodos eficientes de caracterizacao da tolerância ao aluminio em condicoes controladas de ambiente. O presente trabalho teve por objetivo adequar o metodo de solucao minima para a avaliacao da tolerância ao aluminio em genotipos de milho. O trabalho consistiu de dois experimentos. O primeiro foi feito para ajustar o metodo de avaliacao atraves do emprego de solucao minima, e o segundo, para avaliar um conjunto de 22 genotipos de milho fornecidos pela Empresa Agroeste Sementes Ltda. A avaliacao dos genotipos foi realizada com uma solucao que continha diferentes concentracoes de aluminio e calcio. As medias para todas as variaveis analisadas mostraram a diferenca entre os hibridos e entre as concentracoes de aluminio empregadas. As concentracoes de 6mg-1 de aluminio e 40mg-1 de calcio foram consideradas mais eficientes para a discriminacao da tolerância ao aluminio, sendo posteriormente empregadas para o trabalho com as linhagens. No segundo experimento, os resultados possibilitaram identificar linhagens com tolerância ao aluminio.

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

Caracterização genética de Euphorbia heterophylla resistente a herbicidas inibidores da acetolactato sintase

The increase of the number of weed plants resistant to enzyme acetolactate sintase (ALS)-inhibiting herbicides of is a subject frequently discussed by farmers and scientific community. In Brazil, nine species were registered with such problem. The objective of this work was to determine the genetic diversity of wild poinsettia ( Euphorbia heterophylla L.) ALS-resistant populations. Forty populations deriving from seeds collected in areas of the State of Rio Grande do Sul, Brazil, with resistance suspicion, were selected from the previous application of herbicides in greenhouse. Twenty plants of each population were sampled for DNA extraction. Analysis of 30 random amplified poly- morphic DNA (RAPD) markers were performed. Each marker had 10 oligonucleotide of arbitrary sequence. On the grouping analysis, the overall coefficient of similarity was 40% and the populations were separated in seven groups. The populations of the counties of Pontao, Augusto Pestana and Nao-me-Toque were genetically different. There is genetic variability related to herbicide resistence among E. heterophylla populations from plateaus of the State of Rio Grande do Sul.

Marcadores moleculares e sua aplicação no melhoramento genético de plantas

Na implantacao de um programa de melhoramento, uma das principais necessidades do melhorista e a capacidade de identificar genotipos superiores em uma populacao segregante. O conhecimento das relacoes geneticas e a capacidade geral e especifica de combinacao entre os individuos e essencial para a selecao de genitores. Os marcadores geneticos poderao auxiliar na identificacao de individuos atraves de suas diferencas geneticas. Estes marcadores podem ser divididos em morfologicos e moleculares (enzimaticos e de DNA). Os marcadores de DNA como o RFLP e o RAPD poderao contribuir para incrementar a eficiencia do melhoramento de plantas atraves do mapeamento de especies de interesse e de caracteres agronomicos. Alem disto, diversos autores tem comprovado a sua eficiencia em caracterizar e agrupar genotipos diferentes de varias especies com bastante precisao.

Plant traits to complement selection based on yield components in wheat

The aim of the present study was to investigate the relationship between plant traits and yield per spike in wheat genotypes. The measured plant traits were: length of flag leaf blade, peduncle extrusion, peduncle, spike and sheath, culm diameter and plant height. Data were analyzed with correlation and path coefficient analysis. Yield per spike correlated positively with spike length and culm diameter. Path coefficient analysis indicated that, under irrigated condition, yield per spike had a positive direct effect and a positive correlation with spike length and culm diameter and, under non-irrigated condition, yield per spike showed a positive direct effect and a positive correlation with culm diameter, spike length and plant height. Culm diameter and spike length, under irrigated condition, and also plant height, under late season water stress condition, were the plant traits most related to higher grain yield per spike in wheat.

Herança da resistência à mancha-foliar de feosféria em milho

Phaeosphaeria leaf spot (PLS) has caused an expressive reduction in the corn grain yield in Brazil. The increment in sowing date amplitude, conjugated with the use of irrigated areas and zero tillage, had major contribution in the increase of phaeosphaeria leaf spot (PLS) incidence and severity. For this reason, it is important to develop resistant genotypes to this disease; however, an efficient selection depends upon the understanding of the genetic variability and inheritance of the resistance. Aiming to determine combining ability and the mode of inheritance for PLS, seven corn inbreds were crossed for diallel and generation mean analysis. The experiments were conducted in Xanxere, SC. Percentage of foliar area affected by the disease was evaluated 30 days after flowering. The genotypes presented amplitude of 4.3% to 67.0% of foliar area affected by PLS. The LA06 and its hybrids showed high level of resistance. Results indicated that selection for PLS resistant genotypes could be success- fully accomplished in corn breeding programs. At least two major independent genes were identified with a preponderant participation of addictive effects in the inheritance of the trait.

Plant height reduction in populations of triticale (X triticosecale Wittmack) by induced mutations and artificial crosses

Induced mutations by gamma radiation (0, 5, 10, 20 and 40 kR doses) and reciprocal crosses were tested as mechanisms of enhancing genetic variability for plant height in two triticale cultivars, BR4 and EMBRAPA18. The reciprocal crosses and all doses of radiation showed similar increase in genetic amplitude for this trait, being suitable for increasing variability in breeding programs. Genotypes showed different responses as the gamma ray doses were increased, expressing shorter plant height. The decision of using induced mutations or artificial crosses depends on the resources available and the selection method to be used

Capacidade combinatória de genótipos de milho para tolerância ao encharcamento do solo

In southern Brazil, corn could be an alternative for cultivation in flooded areas. However, the development of genotypes tolerant to flooding is fundamental to make this option economically feasible. The objective of this paper was to determine the general and specific combining ability and reciprocal effect for flooding tolerance in corn genotypes. The analysis was based on a diallel cross among four inbreds: two flooding tolerant (CT954280 and CT954330) and two sensitive inbreds (CT966200 and CT966208). The experiment was conducted in 2000 and 2001 under greenhouse conditions at Embrapa Clima Temperado, Pelotas, RS. Root dry matter, plant dry matter, plant high, root length, and leaf chlorophyll content were measured. Genetic variability among the inbreds was detected. Both additive and non-additive effects were important in the determination of the inheritance of flooding tolerance in corn. The correct choice of the female parent is fundamental for tolerant hybrids production, since maternal effects were relevant. Among the analyzed genotypes, the inbred CT954330 presented the highest GCA and may be indicated as a preferential progenitor in crossings that aim to increase flooding tolerance.