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The study aimed to select rice genotypes based on agronomic traits and commercial grain quality. The study was carried out in the 2014/15 and 2015/16 harvests in eight growing environments, located in the state of Rio Grande do Sul, Brazil. Fourteen rice genotypes were sown in each environment. The experiment was conducted in a randomized block design with four replications. The following agronomic traits were evaluated: number of days to flowering and grain yield as well as commercial grain quality traits: percentage of whole grains and percentage of chalky area in the grains. AMMI, GGE and MGIDI methodologies were used to select the best performing genotypes. Using the AMMI, GGE and MGDI methods, genotypes G9 and G1 performed close to the ideal ideotype for the number of days to grain flowering, yield and quality.

Abstract The objective of this work was to characterize chilling tolerance in rice mutant families of the M4 generation, at the seedling stage. Two experiments were carried out: chilling tolerance was evaluated in 43 mutant families, in the 'BRS Querência' original genotype, and in 19 commercial genotypes. In Experiment II, 8 mutant families from Experiment I, 'BRS Querência', and a mutant of the M5 generation were tested. In both experiments, seedlings were evaluated under two conditions: 10°C for seven days and 25°C for seven days. In Experiment I, the induced mutations in rice led to varied responses in chilling tolerance traits, with some M4 mutant families outperforming the original genotype. Experiment II highlighted the impact of mutations on chilling-tolerance, particularly in terms of leaf discoloration and plant recovery. Mutant families of the M4 generation differ from the original genotype 'BRS Querência' in chilling tolerance at the seedling stage. The mutant families M36, M54, and M56 and 'BRS Querência' show genetic similarity, indicating a lack of chilling tolerance during the seedling stage. The mutant families M17, M21, M22, and M26 are promising for rice breeding programs because they present chilling tolerance. The M30 mutant family exhibits the best performance for all analyzed traits, indicating chilling tolerance at the seedling stage.

Abstract The objective of this work was to map the chromosomal regions responsible for iron accumulation in rice grains, in Southern Brazil. Eighty-one rice accessions were genotyped and phenotyped for Fe accumulation. Single nucleotide polymorphisms were mapped in the whole grain on chromosomes 1, 5, 6, and 10, from which 13 candidate genes were identified. Some of the genes, such as O s10g040680 0, seem to have a relationship with Fe homeostasis, while others are related to other metabolic processes or have an unknown function.

Abstract The objective of this work was to determine the genetic correlations and the direct and indirect associations of agronomic traits and grain quality attributes with the percentage of whole grains in flood irrigated rice. The experiment was carried out in two environments, in a randomized complete block design with three replicates, using 23 irrigated rice genotypes. The evaluated traits were: percentage of whole grains, caryopsis length, caryopsis width, panicle length, panicle weight, 1,000 grain weight, days to flowering, percentage of chalky grains with white belly, total chalky area, total whiteness, vitreous whiteness, and defects in coloring. The percentage of grains with white belly and total chalky area were positively correlated, whereas the percentage of grains with white belly and vitreous whiteness were negatively correlated. The traits caryopsis width, percentage of chalky grains with white belly, panicle weight, and 1,000 grain weight showed indirect effects on whole-grain yield response according to total chalky area and total whiteness. Total chalky area and total whiteness are the factors that most negatively influence the percentage of whole grains according to the genotypic correlations and direct effects.

ABSTRACT Rice (Oryza sativa) is among the most important crops worldwide; however, rice crops demand high water consumption. Future projections indicate reduced water availability and severe drought events, which may affect rice crops as the cereal is highly sensitive to drought stress. Thus, cultivars with lower water demand for irrigation or drought escape capacities are among the strategies to address this issue. This study aimed to assess five mutant rice genotypes in terms of growth cycle length, other agronomic interest traits, and drought response in the reproductive stage. The mutant genotypes evaluated showed a shortening of the growth cycle compared to the original cultivar, BRS Pampeira, representing a drought escape strategy. In addition, mutations did not negatively affect plant height and crop yield. However, similar to the original cultivar, mutants are not tolerant to water deficit in the reproductive stage. The genotypes evaluated have potential to be released as early cycle cultivars, which can reduce water demand during the harvest season while presenting a drought escape strategy.

Abstract The objective of this work was to identify the quantitative trait loci (QTLs) associated with grain yield in a rice segregant population (GYP). A population of 245 inbred recombinant rice lines from the 'Epagri 108' (Oryza sativa subsp. indica) x 'IRAT 122' (O. sativa subsp. japonica) cross was evaluated at different locations and years and genotyped by single nucletide polymorphism (SNP) markers. A map of 1,592.8 cM was obtained from 9,831 SNPs, identifying 25 QTLs. The following nine SNPs showed stability between the different environments: M1.37719614 and M6.9563117 for GYP; M4.29340056, M5.25588710, M7.29115624, and M12.4534450 for 100-grain weight (HGW); and M1.38398157, M4.28368337, and M7.25991230 for plant height (PH). Six SNPs were not present in the linkage blocks: M6.9563117 and M4.1077080 for GYP; M5.25588710 and M6.8886398 for HGW; and M2.34471005 and M8.5955948 for PH. The M6.9563117 and M5.25588710 SNPs were considered environmentally stable and were not present in the linkage blocks, showing their high potential for use in marker-assisted selection for grain yield in Brazilian rice breeding programs.

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 The aim of this study was to characterise genetic variability to low-temperature tolerance in the emergence stage of irrigated-rice genotypes under controlled and field conditions. Thirty-seven genotypes were evaluated, interspersed with controls of different levels of low-temperature tolerance. The design used was of randomised blocks with three replications. The genotypes were submitted to germination and emergence in controlled-temperature trials at 13 ºC (Trial I) and 17 ºC (Trial II), and in field environments with no cover (Trial III) and with a cover of polyethylene (Trial IV), where the soil temperature was monitored. The evaluations were carried out daily by counting the emerged seedlings and later inferring the speed of emergence index (SEI). The results showed (experiment I to IV) that the SEI varied from 0.61 to 4.23, increasing by 0.4259 for each 1 ºC increase in soil temperature. The genotypes Ostiglia, Diamante, Baldo, Carnaroli, Selenio, Loto e Amarelo, of subspecies japonica, and Ringo Miara-AC and Arelate, of subspecies indica, are promising sources of genetic tolerance to low temperature. Temperatures of less than 17 ºC reduce the number of emerged seedlings and delay development in each of the rice genotypes under test, with a greater or lesser negative effect on the initial plant stand per unit area.

Abstract: The objective of this work was to estimate the effects of genotype x environment interaction and the genetic potential of flood-irrigated rice cultivars, released between 1972 and 2017, for the state of Rio Grande do Sul, Brazil. The experiments were carried out in the field, in all agroclimatic regions of flood-irrigated rice crop in the state, between the 2005/2006 and 2015/2016 crop years, totaling 60 environments (trials), with 1,961 experimental units. Twenty-five cultivars of irrigated rice were evaluated for the traits grain yield, plant height, days to flowering, and whole grain quality after milling. The values of adaptability and stability were estimated with the aid of mixed models. The rice cultivars BRS Pampa, BRS Pampeira, and BRSCIRAD 302 showed simultaneously high-genotypic grain yield, adaptability, stability, good agronomic traits, and good whole-grain yield after milling. 'BRSCIRAD 302' and 'BRS Pampa' show high-yield stability and can be recommended for all rice cultivation regions of Rio Grande do Sul. 'BRS Pampeira' is responsive to environmental improvements and is indicated for high-technology conditions.

Abstract: The objective of this work was to determine the genetic progress of grain quality attributes of flooded irrigated rice (Oryza sativa) cultivars in the state of Rio Grande do Sul, Brazil, between 1972 and 2016. The genetic estimates followed an approach based on the comparative analysis of 25 cultivars released by Embrapa’s breeding program over this period. The experiment was implemented in four producing regions of the state of Rio Grande do Sul: Sul, Campanha, Planície Costeira Interna, and Planície Costeira Externa. The following significant genetic gains were observed: 0.20% per year, for percentage of whole grains after processing; -1.38% per year, for percentage of chalky kernels and white-core grains; -0.77% per year, for total chalky area; -0.08% per year, for total whiteness; and -0.82% per year, for non-vitreous grain whiteness. Most cultivars released have high amylose content and a low gelatinization temperature. Therefore, the breeding program presented significant annual genetic progresses between 1972 and 2016 for the main attributes of grain quality, and made cultivars available according to the national demand for grain quality in the several segments of the rice production industry.

Objetivou-se nesse estudo estimar a distância genética com base em distintos caracteres fenotípicos e descritores agronômicos, em experimentos a campo, em casa de vegetação e análise conjunta de ambientes em arroz irrigado. Neste estudo foram avaliados 16 genótipos de arroz irrigado em experimentos a campo e em casa de vegetação. Nas duas condições experimentais foram mensurados 24 caracteres, sendo, 16 considerados quantitativos e oito considerados qualitativos. A partir dos dados fenotípicos foram obtidas três matrizes de distâncias de Mahalanobis (baseadas nos caracteres mensurados a campo, casa de vegetação e análise conjunta), que posteriormente originaram três dendrogramas, utilizando o método de agrupamento das médias das distâncias (UPGMA – Unweighted Pair Group Method using Arithmetic averages). A associação das matrizes de distância genética foi realizada pelo teste de Mantel. Assim, as estimativas da distância genética utilizadas, mostraram-se adequadas no agrupamento dos genótipos, evidenciando estreita distância genética entre as cultivares de arroz irrigado avaliadas. As matrizes de distância genética entre os genótipos com base nos caracteres qualitativos aferidos a campo, em casa de vegetação e a conjunta de ambos os ambientes, evidenciaram associação elevada entre si. Existe efeito do ambiente em caracteres de herança genética quantitativa.

O objetivo deste trabalho foi avaliar a produtividade e qualidade de grãos sob distintas densidades de semeadura em híbridos de arroz irrigado. Os experimentos foram conduzidos nos municípios de Capão do Leão e Capivari do Sul, no Rio Grande do Sul. Os híbridos BRSCIRAD 302 e BRSCIRAD AH703 CL foram analisados, nas densidades de semeadura de 10, 20, 30 e 40 kg ha-1, para os caracteres: produtividade e componentes de produção de grãos, características agronômicas, qualidade industrial e comercial de grãos de arroz irrigado. Os dados foram submetidos à análise de variância e ao teste F utilizando-se para a comparação dos híbridos o teste de Tukey nível de significância de 5% e para densidade de semeadura foi aplicada a análise de regressão. A partir da densidade de semeadura de 20 kg ha-1, não há efeito sobre a produtividade. A qualidade industrial de grãos dos híbridos não é influenciada pela variação na densidade de semeadura e a redução na densidade de semeadura para até 10 kg ha-1 não prejudica a qualidade comercial dos grãos. Assim, é possível recomendar o cultivo de híbridos de arroz irrigado com densidades reduzidas de semeadura, a partir de 20 kg ha-1, não afetando a produtividade de grãos e a qualidade dos grãos.

Indirect selection can be considered an interesting strategy for plant breeding, especially when an easily measurable/high heritability trait is highly correlated with a target trait which has a lower heritability in segregating populations. The objective of this study was to obtain estimates of phenotypic, genotypic and environmental correlations and to evaluate the partition of genotypic correlations in direct and indirect effects of agronomic variables on the GY variable, through the analysis of two cultivated environments in fifteen wheat segregating populations. The agronomic traits grain yield per plant (GY), number of grains per ear (NGE), grain weight per ear (GWE), thousand grain weight (TGW), number of fertile tillers (NFT), days from emergence to flowering (DEF), days from flowering to maturity (DFM), total development cycle (CYC), and percentage of lodging (LODG), were evaluated in F4 populations under two cropping systems (with and without flooding). In all populations, by means of simple correlations, the selection of more productive plants can be accomplished by indirect selection for NGE, GWE and NFT. Through path analysis, it was possible to identify an indirect effect on GY by NGE. Also, the effect of GWE, NFT, CYC and DEF on the correlation between other characters (NGE x GY, GY x WTG, DFM x GY, GY x CYC and GY x LODG), emphasizing that the NGE, GWE, NFT, DEF and CYC are the main characters to consider for increasing grain yield in wheat.

The objective of this work was to evaluate the physiological changes that occur in different leaves during the early and late grain-filling stages of two rice genotypes (Oryza sativa subsp. indica , BRS Pelota cultivar, and O. sativa subsp. japonica , BRS Firmeza cultivar), which present differences in grain yield potential. The plants were cultivated in greenhouse. Pigment content, chlorophyll fluorescence, electron transport and oxygen evolution rate were determined in the grain-filling stage, from the first to the forth leaf (top to bottom). Pigment content, photochemical efficiency of photosystem II and electron transport decreased significantly according to the position of leaves in 'BRS Pelota'. The BRS Firmeza cultivar shows higher pigment content and higher activity of the photosynthetic apparatus in comparison to 'BRS Pelota' during the grain-filling stage.O objetivo deste trabalho foi avaliar as mudanças fisiológicas que ocorrem em diferentes folhas durante o início e o final do estádio de enchimento de grãos em dois genótipos de arroz (Oryza sativa subsp. indica cultivar BRS Pelota e O. sativa subsp. japonica cultivar BRS Firmeza) que apresentam diferenças no potencial de produção de grãos. As plantas foram cultivadas em casa de vegetação. Os teores de pigmentos, a fluorescência da clorofila e a taxa de liberação de oxigênio foram determinados no estádio de enchimento de grão da primeira à quarta folha (do topo à base). O teor de pigmentos, a eficiência fotoquímica do fotossistema II e o transporte de elétrons decresceram significativamente de acordo com a posição das folhas na cultivar BRS Pelota. A cultivar BRS Firmeza apresentou maior teor de pigmentos e maior atividade do aparato fotossintético em comparação à 'BRS Pelota' durante o estádio de enchimento de grão.

ABSTRACT There is an increasing demand for special types of rice that have black or red pericarp, low amylose (subspecie japonica) or aromatic. However, intense breeding process for obtaining and indicating genetically promising new cultivars and adapted to cultivation environments are demanded. In this sense, for evaluating the special types of irrigated rice genotypes, and determining the adaptability and stability of these using mixed models. First, a preliminary agronomic evaluation of genotypes for special types of irrigated rice was performed, and later, the agronomically promising genotypes were evaluated in multi-site trials, aiming at verifying the interactions with the environment. Statistical analyzes were performed considering mixed models, using the SELEGEN-REML/BLUP software. High genotypic variability among genotypes for special types of irrigated rice was observed, obtaining some agronomically promising and with good adaptability and stability, with high accuracy and selection efficiency using mixed models. The observed wide diversity and rice genetic variability presented new prospects and opportunities for producers for acquiring food of higher added value to consumer market.

RESUMO Considerando-se a necessidade de incremento de variabilidade genética dentro dos programas de melhoramento de arroz irrigado no Brasil, este trabalho objetivou caracterizar fenotipicamente acessos de arroz irrigado e estimar as suas distâncias genéticas com a utilização de análises multivariadas. Foram caracterizados fenotipicamente 92 acessos de arroz irrigado avaliados quanto a 35 descritores morfológicos, sendo, 21 caracteres de herança qualitativa e 14 caracteres de herança quantitativa. Os caracteres quantitativos discriminaram via distâncias genéticas os acessos em nove grupos distinguíveis entre si, principalmente pela distribuição das subespécies indica e japonica. Já para os caracteres qualitativos o dendrograma discriminou cinco grupos distintos, sendo evidenciadas a seleção e utilização de genótipos a nível mundial com arquitetura e padrões fenotípicos definidos. Logo, evidenciou-se pela caracterização fenotípica via análise multivariada que os genótipos cultivados no Rio Grande do Sul demonstraram estreita base genética. No entanto, existe variabilidade fenotípica para incremento desta base genética e consequente aumento da probabilidade de obtenção e seleção de progênies superiores geneticamente.

Different rice cultivars have been developed in order to obtain grains with optimal cultivation and compositional characteristics, which affect their potential applications. Therefore, the characterization of these different rice cultivars is required. In the present study, white rice and rice bran from the cultivars BRS AG, BRS Pampa, and BRS 358 provided by EMBRAPA were characterized by physicochemical means, infrared spectroscopy (FTIR-ATR), and thermal analyses. The moisture, lipid, and ash contents did not differ among the white rice cultivars. The cultivar BRS Pampa exhibited the highest protein and lowest total carbohydrate contents. Both BRS Pampa and BRS 358 showed a higher phytic acid content than BRS AG. The highest total carbohydrate content was observed in BRS AG white rice samples, which confirmed its suitability for use in ethanol production. Among the rice bran samples, BRS 358 demonstrated the highest contents of lipid, protein, and phytic acid, and the lowest total carbohydrate content. FTIR-ATR and thermal analyses were suitable for correlating the physicochemical properties of white rice and rice bran with the molecular composition in the respective cultivars studied. Both white rice and rice bran exhibited a thermal degradation temperature at 300 °C. Lipids, protein, ash and phytic acid were considerably higher in rice bran than white rice in all cultivars studied, which demonstrates the importance of the use of this by-product.

Techniques used to induce mutations, such as ionizing radiation, are an effective tool in increasing genetic variability in breeding programs of species of economic interest. This study aimed to evaluate the effect of different doses of Co60 gamma radiation on previously soaked seeds on the emergence and early growth of seedlings of two rice cultivars. To do this, seeds (25% moisture) of BRS Querência and BRS Fronteira were irradiated with zero (control), 50, 100, 150 and 200 Gy, and then sown in trays containing soil and kept in a greenhouse. The results showed that gamma radiation affected seedling development, where the highest dose tested (200 Gy) significantly reduced the emergence and the index of emergence speed. Growth parameters were reduced greater reduction in cv. BRS Querência. For antioxidant enzymes, superoxide dismutase expressed little variation for the periods evaluated. Already ascorbate peroxidase and catalase showed a significant increase in horsepower cv. BRS Fronteira at 14 DAS, followed by an increase in both cultivars ascorbate peroxidase activity at 28 DAS. The highest antioxidant capacity observed in cv. BRS Fronteira conferred greater tolerance to stress caused by gamma radiation.Técnicas como radiações ionizantes, utilizadas para induzir mutações constituem ferramenta eficaz no aumento de variabilidade genética em programas de melhoramento de espécies de interesse econômico. Neste trabalho, objetivou-se verificar o efeito de diferentes doses de radiação gama Co60 em sementes previamente embebidas sobre a emergência e o crescimento inicial de plântulas de duas cultivares de arroz. Lotes de sementes com 25% de umidade das cultivares BRS Querência e BRS Fronteira foram irradiados com doses de zero (controle), 50, 100, 150 e 200 Gy, sendo, em seguida, semeadas em bandejas contendo solo e mantidas em casa de vegetação. Os resultados mostraram que a radiação gama afetou o desenvolvimento das plântulas, sendo que a maior dose testada (200 Gy) reduziu, significativamente, a emergência e o índice de velocidade de emergência. Os parâmetros de crescimento apresentaram maior redução na cv. BRS Querência. Na atividade das enzimas antioxidantes, a superóxido dismutase expressou pouca variação para os períodos avaliados. Já, a ascorbato peroxidase e catalase mostraram expressivo aumento na cv. BRS Fronteira aos 14 DAS, seguidas de incremento para as duas cultivares na atividade da ascorbato peroxidase aos 28 DAS. A maior capacidade antioxidante observada na cv. BRS Fronteira conferiu uma maior tolerância ao estresse causado pela radiação gama.

The objective of this work was to develop new irrigated rice lines tolerant to imidazolinone herbicides. The backcross breeding procedure was used to transfer the imidazolinone tolerance allele from mutant 93AS3510 to the recurrent parents 'BRS 7 Taim' and 'BRS Pelota'. Individual herbicide-tolerant plants were selected in each generation, for three backcrossings (RC1 to RC3), followed by three selfing generations (RC3F1 to RC3F3). The best four RC3F3 lines for agronomic traits were genotyped with 44 microsatellite markers. The observed conversion index of the new imidazolinone-tolerant lines varied from 91.86 to 97.67%. Pairwise genetic distance analysis between these lines and 22 accessions from the Embrapa's Rice Germplasm Bank clustered the new lines with their respective recurrent parents, but not with 'IRGA 417', which was originally used as recurrent parent to derive IRGA 422 CL, the only imidazolinone-tolerant irrigated rice cultivar recommended for cultivation in Brazil. Therefore, these lines represent new options of genetically diverse imidazolinone-tolerant rice accessions. Lines CNA10756 ('BRS Sinuelo CL') and CNA10757 will be released for cultivation in the Clearfield irrigated rice production system in Rio Grande do Sul, Brazil.O objetivo deste trabalho foi desenvolver novas linhagens de arroz irrigado tolerantes ao herbicida imidazolinona. O método de retrocruzamento foi usado para transferir o alelo de tolerância à imidazolinona do mutante 93AS3510 para os genitores recorrentes 'BRS 7 Taim' e 'BRS Pelota'. Indivíduos tolerantes ao herbicida foram selecionados em cada geração, por três gerações de retrocruzamento (RC1 a RC3), seguidas por três gerações de autofecundação (RC3F1 a RC3F3). As quatro melhores linhagens RC3F3 quanto às características agronômicas foram genotipadas com 44 marcadores microssatélites. O índice de conversão observado nas novas linhagens tolerantes à imidazolinona variou de 91,86 a 97,67%. A análise de distância genética par-a-par, entre estas linhagens e 22 acessos do banco de germoplasma de arroz da Embrapa, agrupou-as com os seus respectivos genitores recorrentes, mas não com 'IRGA 417', que foi originalmente usada como genitor para derivar a IRGA 422 CL, única cultivar tolerante ao herbicida imidazolinona recomendada para cultivo no Brasil. Portanto, estas linhagens representam novas opções de acessos geneticamente diversos de arroz irrigado com tolerância ao herbicida imidazolinona. As linhagens CNA10756 ('BRS Sinuelo' CL) e CNA10757 serão lançadas para cultivo no sistema de produção "Clearfield" no Rio Grande do Sul, Brasil.

As plantas em condições naturais estão expostas a vários estresses ambientais que afetam seu metabolismo. Dentre esses, a salinidade dos solos e da água de irrigação é um dos mais sérios problemas para a agricultura irrigada. O objetivo deste trabalho foi identificar, por meio de caracteres morfológicos, a variabilidade genética de 10 genótipos de arroz, cultivados in vitro, e agrupar esses genótipos para o caráter tolerância à salinidade. Os tratamentos foram constituídos por 10 genótipos e quatro concentrações de NaCl (0, 4, 8 e 12 mg L-1) acrescidas ao meio de cultura MS. Após 21 dias, foram avaliados diversos caracteres morfológicos, para os quais foram realizados cálculos percentuais de desempenho relativo (aumento ou redução), considerando-se o valor absoluto do tratamento-controle (0 mg L-1). Todos os caracteres mensurados tiveram seu desenvolvimento reduzido em substrato salino, sendo os correspondentes à biomassa média da parte aérea e do sistema radicular os mais sensíveis ao NaCl. Observou-se dissimilaridade entre os genótipos estudados para tolerância à salinidade, verificada pela formação de três grupos distintos pelo método hierárquico UPGMA e dois grupos pelo método de Tocher, sendo o genótipo BRS Bojuru o mais tolerante e BRS "7" Taim e BRS Ligeirinho os mais sensíveis à salinidade.