Abstract Effective strategies for disease control are crucial for sustaining world food production and ensuring food security for the population. Wheat blast, a disease caused by the pathogen Magnaporthe oryzae pathotype Triticum, has been a concern for cereal producers and researchers due to its aggressiveness and rapid expansion. To solve this problem, the development of resistant varieties with durable resistance is an effective, economical and sustainable way to control the disease. Conventional breeding can be aided by several molecular tools to facilitate the mining of many sources of resistance, such as R genes and QTLs. The identification of new sources of resistance, whether in the wheat crop or in other cereals are an opportunity for efficient wheat breeding through the application of different techniques. Since this disease is still poorly studied in wheat, knowledge of the rice Magnaporthe pathotype may be adapted to control wheat blast. Thus, genetic mapping, molecular markers, transgenic approaches, and genomic editing are valuable technologies to fight wheat blast. This review aimed to compile the biotechnological alternatives available to accelerate the development of improved cultivars for resistance to wheat blast.

ABSTRACT The olive tree (Olea europaea L.) is a species of great importance in history and economic, with large phenotypic variability, represented through a wide range of cultivars spread throughout the world. There are several studies on the characterization of a large number of cultivars of the species. However, there is a need to uncover how these phenotypic traits are heritable, and how they can change when environmental conditions vary. For this reason, the objective here was to estimate the heritability coefficients for fruit characters in six commercial cultivars, analyzed under conditions in the state of Rio Grande do Sul, Brazil. The study was carried out in a single year, based on the analysis of fruit and oil traits on the cultivars Arbequina, Arbosana, Frantoio, Koroneiki, Manzanilla de Sevilla, and Picual, under environmental conditions in the state of Rio Grande do Sul. Phenotypic plasticity and broad-sense heritability were estimated in both inter and intra-cultivar comparisons. From the analyses of variance and heritability, it was observed that some cultivars such as Koroneiki or Picual had their characters mainly under genetic control, while Arbequina was more influenced by genotype-environment interaction. The information derived from this work can help guide the selection of cultivars that are best adapted under the local environments of the southern region of Brazil.

Resumo O objetivo deste trabalho foi analisar componentes de variâncias e herdabilidades, estimar o ganho de seleção e avaliar as diferentes pressões de seleção para atributos físicos de qualidade de grãos de famílias de gerações segregantes de arroz (Oryza sativa) irrigado, por meio da metodologia REML/BLUP. O experimento foi conduzido no Rio Grande do Sul, Brasil, onde foram realizadas seleções nas gerações segregantes F3, F4 e F5, nas safras 2015/2016, 2016/2017 e 2017/2018, em oito populações segregantes (famílias) oriundas de diferentes cruzamentos. Foram avaliados atributos físicos de qualidade intrínsecos, parâmetros genéticos e resposta à seleção, tendo-se utilizado diferentes pressões de seleção. Foram obtidas estimativas que apresentaram ganhos genéticos para os caracteres de qualidade dos grãos, principalmente para área calcárea total, alvura vítrea, alvura total, relação entre alvura vítrea e alvura total, e percentual de grãos inteiros e quebrados, em seleções nas primeiras gerações. As famílias utilizadas apresentam resultados satisfatórios, sendo superiores às cultivares-controle. Para a maioria dos caracteres, as estimativas de herdabilidade em sentido amplo são consideradas intermediárias, junto com os demais parâmetros, o que mostra a possibilidade de seleção genética para os atributos de qualidade do grão. A resposta à seleção com pressão de 10% é muito promissora para os atributos de qualidade de grãos de arroz.

Abstract The objective of this work was to analyze components of variances and heritabilities, estimate selection gain, and evaluate the different selection pressures for physical quality attributes of grains of families of segregating generations of irrigated rice (Oryza sativa), through the REML/BLUP methodology. The experiment was conducted in the state of Rio Grande do Sul, Brazil, where selections were made in the F3, F4, and F5 segregating generations, in the 2015/2016, 2016/2017, and 2017/2018 crop seasons, in eight segregating populations (families) from different crosses. Intrinsic physical quality attributes, genetic parameters, and response to selection were evaluated using different selection pressures. The obtained estimates showed genetic gains for the characters related to grain quality, mainly for total chalky area, vitreous whiteness, total whiteness, ratio between vitreous whiteness and total whiteness, and percentage of whole grains and broken grains, in selections in early generations. The used families show satisfactory results, being superior to the control cultivars. For most characters, the estimates of broad-sense heritability are considered intermediate, together with the other parameters, showing the possibility of genetic selection for grain quality attributes. The response to selection with a pressure of 10% is very promising for rice grain quality attributes.

ABSTRACT Biochemical assays in a time-course were employed to evaluate stresses induced by glyphosate treatment in resistant and sensitive biotypes of Conyza bonariensis. Two experiments were conducted assessing glyphosate doses and time-course after treatment. The doses of glyphosate ranged from 0 to 11840 g ae·ha–1 and assessments performed until 552 h after glyphosate treatment (HAT). The objectives of this study were to evaluate the oxidative stress and differential antioxidant enzyme activity in glyphosate-resistant and -sensitive biotypes of hairy fleabane after glyphosate treatment. After treatment, both studied biotypes accumulated similar levels of shikimic-acid until 96 h. The sensitive biotype died at192 HAT. Shikimic-acid and hydrogen peroxide (H2O2) accumulation in glyphosate-resistant biotype were transient and did not differ from untreated plants at 288 and 500 HAT, respectively. In both glyphosate-resistant and -sensitive biotypes, a correlation analysis established a cause-and-effect relationship after glyphosate treatment, which leads to shikimic-acid and hydrogen peroxide accumulation, lipid peroxidation (indicates tissue damage) and an enhancement in the activity of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) enzyme. However, in the glyphosate-resistant biotype, the oxidative stress and tissue damage were lower, and antioxidant enzyme activities SOD, CAT, and APX were higher than in the -sensitive biotype. It indicates that antioxidant enzyme in glyphosate-resistant biotype might be related to the glyphosate-resistance process in Conyza bonariensis. This study is the first report of differential antioxidant enzyme activity in hairy fleabane.

Resumo: O objetivo deste trabalho foi avaliar o desempenho de híbridos de milho (Zea mays) intervarietais, a partir de cruzamentos topcross entre populações crioulas, além de confirmar se a dissimilaridade genética entre as populações é correlacionada à heterose dos híbridos intervarietais no campo. Nove híbridos topcross foram avaliados com seu testador 'BRS Planalto', e as seguintes populações crioulas foram utilizadas como genitores: Argentino Branco, Dente de Ouro, Amarelão, Criolão, Caiano Rajado, Branco Oito Carreiras, Branco Roxo Índio, Cateto Branco e Argentino Amarelo. O testador 'BRS Planalto' e os híbridos topcross Branco Oito Carreiras x 'BRS Planalto' e Criolão x 'BRS Planalto' apresentaram maior potencial per se quanto ao rendimento de grãos. O topcross Branco Oito Carreiras x 'BRS Planalto' apresentou melhor desempenho quanto a número de grãos por fileira, massa de grãos da espiga e diâmetro de espiga, enquanto o Criolão x 'BRS Planalto' apresentou melhor desempenho quanto a número de grãos por fileira e comprimento de espiga. As maiores estimativas de distância genética não implicaram, necessariamente, altos valores de heterose, e tiveram correlação apenas com o comprimento da espiga. Portanto, não é possível predizer os efeitos de alta heterose sobre o rendimento de grãos, com base na distância genética entre as populações envolvidas nos cruzamentos.

Abstract: The objective of this work was to evaluate the performance of intervarietal corn (Zea mays) hybrids with topcross crosses between landrace populations, and to confirm whether genetic dissimilarity between populations is correlated with the heterosis of the intervarietal hybrids in the field. Nine topcross hybrids were evaluated with their tester 'BRS Planalto', and the following landrace populations were used as parents: Argentino Branco, Dente de Ouro, Amarelão, Criolão, Caiano Rajado, Branco Oito Carreiras, Branco Roxo Índio, Cateto Branco, and Argentino Amarelo. The tester 'BRS Planalto' and the topcross hybrids Branco Oito Carreiras x 'BRS Planalto' and Criolão x 'BRS Planalto' showed higher per se potential for grain yield. The topcross hybrid Branco Oito Carreiras x 'BRS Planalto' showed a better performance for number of grains per row, grain weight, and ear diameter, whereas Criolão x 'BRS Planalto' displayed a better performance for the number of grains per row and ear length. Greater estimates of genetic distance did not necessarily result in greater heterosis values and were exclusively correlated with grain ear length. Therefore, it is not possible to predict the effects of high heterosis on grain yield, based on the genetic distance between the populations involved in the crosses.

Resumo: O objetivo deste trabalho foi comparar o uso de métodos biométricos uni e multivariados na avaliação da adaptabilidade e da estabilidade de um importante grupo de cultivares de aveia-branca (Avena sativa), cultivadas no Sul do Brasil. Utilizou-se o delineamento experimental de blocos ao acaso, em arranjo fatorial 12 ambientes x 7 cultivares, com três repetições. A análise de variância e os métodos de Eberhart & Russel, de Annicchiarico e da média harmônica do desempenho relativo dos valores genéticos preditos (MHPRVG) foram avaliados. Na comparação geral dos métodos, os genótipos 'UPFA Gaudéria' e 'URS Guapa' foram os mais estáveis em relação à produtividade de grãos. Os genótipos 'UPFA Gaudéria' e 'URS-21' destacaram-se em peso do hectolitro, tendo apresentado as melhores respostas pelo método de Annicchiarico e da MHPRVG. Para a massa de mil grãos, todos os métodos apresentaram resultados semelhantes, o que indica que o genótipo 'UPFA Gaudéria' apresentou os melhores resultados. O genótipo 'URS Guapa' foi superior quando foram utilizados os métodos de Eberhart & Russel, de Annicchiarico e da MHPRVG. Os métodos uni e multivariados avaliados são adequados para estimar com confiança a adaptabilidade e a estabilidade das cultivares para cada objetivo de produção, rendimento e qualidade de grãos.

Abstract: The objective of this work was to compare uni- and multivariate biometric methods to evaluate the adaptability and stability of an important group of white oat (Avena sativa) cultivars grown in Southern Brazil. The used experimental design was a randomized complete block, in a factorial arrangement of 12 environments x 7 cultivars, with three replicates. The analysis of variance and the methods of Eberhart & Russel, Annicchiarico, and the harmonic mean of the relative performance of predicted genetic values (MHPRVG) were assessed. In the general comparison of the methods, the 'UPFA Gaudéria' and 'URS Guapa' genotypes were more stable regarding grain yield. The 'UPFA Gaudéria' and 'URS-21' genotypes stood out for hectoliter weight, presenting the best performances by the methods of Annicchiarico and the MHPRVG. For thousand-grain weight, all methods showed similar results, indicating that the 'UPFA Gaudéria' genotype presented the best results. The 'URS Guapa' genotype was superior when using the methods of Eberhart & Russel, Annicchiarico, and the MHPRVG. The uni- and multivariate methods evaluated are suitable to estimate with high confidence the adaptability and stability of cultivars for each targeted grain production, yield, and quality.

Abstract WRKY transcription factors (TFs) are responsible for the regulation of genes responsive to many plant growth and developmental cues, as well as to biotic and abiotic stresses. The modulation of gene expression by WRKY proteins primarily occurs by DNA binding at specific cis-regulatory elements, the W-box elements, which are short sequences located in the promoter region of certain genes. In addition, their action can occur through interaction with other TFs and the cellular transcription machinery. The current genome sequences available reveal a relatively large number of WRKY genes, reaching hundreds of copies. Recently, functional genomics studies in model plants have enabled the identification of function and mechanism of action of several WRKY TFs in plants. This review addresses the more recent studies in plants regarding the function of WRKY TFs in both model and crop plants for coping with environmental challenges, including a wide variety of abiotic and biotic stresses.

Resumo: O objetivo deste trabalho foi avaliar a consistência dos métodos de Annicchiarico, Lin & Binns, Wricke e de análise fatorial na identificação de clones de eucalipto com estabilidade, adaptabilidade e alto potencial produtivo. Foram utilizados 84 clones, com três anos de idade, provenientes do programa de melhoramento genético da empresa CMPC Celulose Riograndense. Três experimentos de campo foram realizados em delineamento de blocos ao acaso, em arranjo fatorial 84x3, com 20 repetições de uma planta por parcela. Os clones foram avaliados quanto a diâmetro à altura do peito, altura da planta e volume de madeira. Os métodos de Annicchiarico e Lin & Binns são altamente correlacionados entre si, e seu uso em conjunto com o método de Wricke é uma estratégia apropriada para avaliação de clones de eucalipto. A análise fatorial identificou clones amplamente adaptáveis, e alguns deles foram os mesmos identificados pelos métodos de Annicchiarico e Lin & Binns. O uso da classificação média dos clones, juntamente com a análise fatorial, é eficiente para identificar os mais adaptados, estáveis e produtivos, entre um elevado número de genótipos.

Abstract: The objective of this work was to evaluate the consistency of the methods of Annicchiarico, Lin & Binns, Wricke, and factor analysis in identifying eucalyptus clones with stability, adaptability, and high productive potential. Eight-four clones, with three years of age, from the genetic breeding program of the company CMPC Celulose Riograndense were used. Three field experiments were carried out in a randomized complete block design, in an 84x3 factorial arragement, with 20 replicates of one plant per plot. The clones were evaluated as to diameter at breast height, plant height, and volume of wood. The methods of Annicchiarico and Lin & Binns are highly correlated with each other, and their use together with the method of Wricke is a sound strategy for the evaluation of eucalyptus clones. The factor analysis identified broadly adaptable clones, and some of them were the same ones identified by the methods of Annicchiarico and Lin & Binns. The use of the mean classification of the clones, along with the factor analysis, is efficient to identify the most adapted, stable, and productive ones among a high number of genotypes.

RESUMO: O caráter stay-green tem sido relacionado à maior tolerância a estresses e a produtividade pela manutenção mais prolongada do aparato fotossintético. A relação deste caráter com a produtividade de grãos talvez esteja associada a uma rede de características que não somente a massa de grãos. O objetivo do estudo é trazer à luz a real contribuição do caráter stay-green em trigos brasileiros, na relação entre os caracteres definidores da produtividade de grãos, em diferentes condições de ambiente. O experimento foi conduzido em delineamento experimental de blocos casualizados com três repetições, nos anos de 2003, 2004 e 2005. Foram avaliadas linhagens-irmãs com presença e ausência do caráter stay-green, analisando a correlação fenotípica e trilha separadamente por ano e grupo de maturação. Em condições favoráveis de cultivo, a contribuição do caráter stay-green em trigo se dá pelo aumento da fertilidade de espiga, incrementando o número de grãos. Num cenário mais restritivo, favorece a massa de grãos pelo maior tempo de enchimento no final do ciclo.

ABSTRACT: The stay-green character has been related to greater stress tolerance and yield through longer activity of the photosynthetic apparatus. Association of this character with grain yield may be linked to a network of features other than the grain mass. This study aimed to shed light on the actual contribution of stay-green character in Brazilian wheats and the associations between grain yield components in different environmental conditions. The experiment was conducted in a randomized block design with three replications in the years 2003, 2004 and 2005. Sibling lines with and without the stay-green character were evaluated analyzing the phenotypic correlation and path analysis separately by year and maturity group. Under favorable growing conditions, the contribution of stay-green character in wheat is obtained by the increased ear fertility and number of grains. In a more restrictive scenario, it favors an increase in grain mass by longer filling time at the end of the cycle.

ABSTRACT Drought stress affects crop quality and productivity. The challenge of increasing food availability for a growing worldwide demand relies on the development of tolerant cultivars that will need to be adapted to arid and semi-arid areas. In order to help the understanding of rice response to stress, the phenotypic response of 6 Brazilian rice cultivars and 2 different crosses between them were characterized under drought conditions. Since gene regulation is an important part of root morphological responses to stressful conditions, 4 genes related to auxin response and root modifications (OsGNOM1 CRL4, OsIAA1, OsCAND1 and OsRAA1) were evaluated. The expression of these genes was analyzed in stressed rice using public available microarray data and then through real-time quantitative polymerase chain reaction (RT-qPCR), in the 6 phenotypically evaluated Brazilian genotypes under standard conditions (absence of stress). Our results show that all genotypes lengthened its roots in response to drought, specially the 2 hybrids. The expression of these genes is modified in response to stress, and OsRAA1 has a very special behavior, constituting a target for future studies. Further steps include the study of polymorphisms in these genotypes in order to understand if differences in these genes or in regulatory regions can be associated with differences in root system architecture and/or stress tolerance.

ABSTRACT Improvement of quality-related traits of grains is a constant concern in white oat breeding programs, which challenges breeders to understand their dynamics. The performance of different genetic combinations must be thoroughly evaluated to make high nutritional quality cultivars available. This study aimed to estimate the heterosis on F1 and F2 generations, vigor loss, due to inbreeding, and correlation between the grain chemical components to understand the dynamics of these traits, considering two segregating oat progenies. The populations Albasul × UPF 15 (population 1) and IAC 7 × UFRGS 19 (population 2) were developed. Both populations showed transgressive segregant individuals. The combination Albasul × UPF 15 provided significant heterosis for traits β-glucan total and soluble fiber contents, while the population obtained by crossing IAC 7 × UFRGS 19 generated significant gain by heterosis for total fiber, insoluble fibers and non-structural carbohydrate contents. Considering the F2 average for each population, one can observe that population 1 presents higher β-glucan and lipid contents than population 2. On the other hand, population 2 has higher protein content than population 1. In both populations, the non-structural carbohydrate content is strongly and negatively correlated whith protein, total and insoluble fibers. Correlations between total fibers and lipids and between total fibers and insoluble fibers were both positive and high in both populations.

ABSTRACT O incremento do potencial produtivo nas novas variedades de arroz (Oryza sativa L.) tem sido um dos principais desafios para o melhoramento genético. A geração de mutantes, seguida da sua caracterização, constitui-se em uma ótima possibilidade para isolar e selecionar genes e genótipos que apresentem caracteres agronômicos de interesse. Este trabalho teve como objetivo avaliar o efeito do mutagênico químico etilmetanossulfonato (EMS) sobre caracteres agronômicos em 340 famílias M3 de arroz, derivadas da cultivar BRS Querência. As sementes de cada família e da testemunha BRS Querência foram semeadas a campo e posteriormente avaliadas para os caracteres comprimento da panícula principal, peso da panícula principal, massa de grãos da panícula principal, largura da folha bandeira e estatura de planta. Os dados foram submetidos à análise de variância (p ≤ 0,05), e a comparação entre as médias foi realizada pelo teste de Dunnett a 5% de significância. Os resultados obtidos mostram que existe variabilidade genética entre as famílias mutantes de arroz e que a indução de mutação com EMS a 1,5% é eficiente na geração de mutantes de arroz para todos os caracteres avaliados. Dentre esses, a estatura das plantas foi a mais afetada pelo agente mutagênico, o qual proporcionou o incremento do caráter. Para o caráter comprimento da panícula principal, sete famílias obtiveram médias superiores à testemunha; já para os caracteres peso e massa de grãos da panícula principal, foram observadas quatro e seis famílias mutantes, respectivamente, com desempenho superior ao da testemunha.

ABSTRACT The increase of yield potential in new rice (Oryza sativa L.) varieties has been a major challenge for genetic improvement. The generation of mutants, followed by their characterization, constitutes a great possibility to isolate and select genes and genotypes that present agronomic traits of interest. This study aimed to evaluate the effect of chemical mutagen ethyl methane sulphonate (EMS) on agronomic traits in 340 M3 families of rice derived from BRS Querência cultivar. Seeds from each family and the original genotype BRS Querência were sown in the experimental field, and the characters main panicle length, main panicle weight, main panicle grain weight, flag leaf width and plant height were evaluated. Data were subjected to analysis of variance (p ≤ 0.05), and a comparison of means was carried out by Dunnett's test at 5% significance. The results show that there is genetic variability among the mutant families, suggesting that the mutagen EMS at 1.5% is effective for generating mutants for all assessed traits. Among the characters, plant height was the most affected by the mutagen, which provided an increase in the character. For the main panicle length character, seven families showed means above the control; for main panicle weight and grain weight, four and six mutant families were observed, respectively, with a superior performance in comparison to the control.

Observando as novas demandas do cenário agrícola mundial, a busca por genótipos mais produtivos, eficientes e adaptados a estresses tem chamado a atenção de melhoristas de plantas na análise de plantas com melhores características fisiológicas. Nesse contexto, o caráter stay-green vem tomando destaque, como uma importante estratégia em superar os atuais tetos de produtividade, aliados à adaptabilidade e estabilidade. Esta revisão tem com objetivo trazer à luz os principais aspectos relacionados ao caráter stay-green, mostrando suas potencialidades de emprego no melhoramento genético de plantas.

Looking at the new demands of the global agricultural scenario, the search for more productive, efficient and stress adapted genotypes has attracted attention of plant breeders regarding plants with improved physiological characteristics. Therefore, the stay-green trait has taken proeminence as an important strategy to overcome the current yield plateaus allied with yield adaptability and stability. This review has aimed to bring light the main aspects of the stay-green character, showing their employment potential of plant breeding.

Resumo:O objetivo deste trabalho foi caracterizar o desempenho de genótipos elite de trigo de diferentes programas de melhoramento do Brasil, para caracteres associados à produtividade de grãos e à germinação na pré-colheita. O estudo foi conduzido em 2010 e 2011 no Município de Capão do Leão, RS, em delineamento experimental de blocos ao acaso, com três repetições. Foram avaliados 33 genótipos de trigo quanto aos caracteres relacionados à germinação em pré-colheita e ao rendimento de grãos. A estimativa da distância genética foi utilizada para predizer combinações potenciais na seleção de plantas com alta produtividade de grãos e tolerância à germinação na pré-colheita. A análise combinada de grãos germinados e número de queda mostra que os genótipos TBIO Alvorada, TBIO Mestre, Frontana, Fundacep Raízes, Fundacep Cristalino e BRS Guamirim apresentam tolerância à germinação em pré-colheita. As combinações de TBIO Alvorada e TBIO Mestre com Fundacep Cristalino mostram alto potencial na recuperação de genótipos superiores para elevada produtividade de grãos e tolerância à germinação em pré-colheita.

Abstract:The objective of this work was to characterize the performance of elite wheat genotypes from different Brazilian breeding programs for traits associated with grain yield and preharvest sprouting. The study was conducted in 2010 and 2011 in the municipality of Capão do Leão, in the state of Rio Grande do Sul, Brazil, in a randomized complete block design with three replicates. Thirty-three wheat genotypes were evaluated for traits related to preharvest sprouting and grain yield. The estimate of genetic distance was used to predict potential combinations for selection of plants with high grain yield and tolerance to preharvest sprouting. The combined analysis of sprouted grains and falling number shows that the TBIO Alvorada, TBIO Mestre, Frontana, Fundacep Raízes, Fundacep Cristalino, and BRS Guamirim genotypes are tolerant to preharvest sprouting. Combinations of TBIO Alvorada and TBIO Mestre with Fundacep Cristalino show high potential for recovering superior genotypes for high grain yield and tolerance to preharvest sprouting.

A aveia branca é uma excelente opção como cultura de inverno em sistemas de sucessão de culturas. A decomposição do material orgânico, mantido na superfície do solo no plantio direto, associado a condições de má drenagem ou umidade excessiva, acentua a formação de ácidos orgânicos. Dentre estes, os ácidos acéticos e butírico apresentam grande potencial fitotóxico. O objetivo do trabalho foi avaliar o efeito dos ácidos acético e butírico na germinação e no desenvolvimento inicial de plântulas de diferentes cultivares de aveia branca. O experimento foi conduzido em blocos completamente casualizados, onde sementes das cultivares Afrodite, Albasul, Brisasul, FAEM 06, IAC 7, URS 21 e URS Taura foram embebidas em quatro doses de ácido acético (0, 4, 8 e 12 mM) e butírico (0, 3, 6 e 9 mM). As sementes foram mantidas em câmera de germinação por dez dias. Foram avaliados os caracteres comprimento da parte aérea (CPA), comprimento de raiz (CR) e a porcentagem de germinação (% GER). O ácido butírico demonstrou-se mais fitotóxico que o ácido acético, sendo o desenvolvimento das raízes mais afetado que a parte aérea. As cultivares IAC 7 e Brisasul demonstraram-se mais sensíveis e as cultivares URS Taura e Afrodite demonstraram-se menos afetadas pelos ácidos orgânicos em estudo. Sem a adição de ácidos e na dose de 12 mM de ácido acético, verificou-se a correlação entre % GER e CR. Existe grande variabilidade entre as cultivares estudadas, em resposta aos ácidos acético e butírico.

The white oat is an excellent winter cropchoice in crop succession systems. The decomposition of organic matter sustained on the soil surface in no tillage conditions associated with poor drainage or excessive moisture increase the formation of organic acids. Among these, acetic and butyric acids have great phytotoxic potential. The objective of this study was to evaluate the effect of acetic and butyric acids on germination and early seedling development of different oat cultivars. The experiment was conducted in a completely randomized block design, where seeds of cultivars Afrodite, Albasul, Brisasul, FAEM 06, IAC 7, URS 21 and URS Taura, were subjected to four doses of acetic (0, 4, 8 and 12 mM ) and butyric ( 0, 3, 6 and 9 mM)acid. The seeds were kept in germination chamber for ten days. The characters evaluated wereshoot length (CPA), root length (CR), and the percentage of germination (% GER). The toxicity of butyric acid was higher than acetic acid, damaging root development more than shoot length. Cultivars IAC 7 and Brisasul were sensitive and cultivars URS Taura and Afrodite were tolerant tothe organic acids studied. In control and 12 mM acetic acid, there was a correlation between CR and % GER. There is great variation among cultivars in response to acetic and butyric acids.