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The objective of this work was to investigate the interaction of irrigated rice genotypes in different environments, based on the genotypic evaluation of grain quality traits, through the adaptability and stability analysed by mixed models. These parameters were obtained from cultivation trials in eight cultivation environments of irrigated rice in Southern Brazil. The experimental design was randomized complete blocks, with 14 genotypes for each one and four repetitions. The genotypic values were estimated using REML/BLUP, based on the harmonic mean methods of the genotypic values, the relative performance of the predicted genotypic values through the environments and the harmonic mean of the relative performance of the genotypic values. The high accuracy values obtained for the most studied variables, show a great experimental quality and safety in the selection of these traits. The lines AB11502 and AB10501 showed a better agronomic performance in the milling yield. AB13008, AB13002 and AB13003 stood out for plaster traits, showing higher adaptability and stability. These inbred lines revealed high potential for grain quality attributes, and have potential to be released.

Embrapa has led breeding programs for irrigated and upland rice (Oryza sativa L.) since 1977, generating a large amount of pedigree and phenotypic data. However, there were no systematic standards for data recording nor long-term data preservation and reuse strategies. With the new aim of making data reuse practical, we recovered all data available and structured it into the Embrapa Rice Breeding Dataset (ERBD). In its current version, the ERBD includes 20,504 crosses involving 9,974 parents, the pedigrees of most of the 4,532 inbred lines that took part in advanced field trials, and phenotypic data from 2,711 field trials (1,118 irrigated, 1,593 upland trials), representing 226,458 field plots. Those trials were conducted over 38 years (1982-2019), in 247 locations, in latitudes ranging from 3°N to 33°S. Phenotypic traits included grain yield, days to flowering, plant height, canopy lodging, and five important fungal diseases: leaf blast, panicle blast, brown spot, leaf scald, and grain discoloration. The total number of data points surpasses 1.27 million. Descriptive statistics were computed over the dataset, split by cropping systems (irrigated or upland). The mean heritability of grain yield was high for both systems, at around .7, whereas the mean coefficient of variation was 13.9% for irrigated trials and 18.7% for upland trials. The ERBD offers the possibility of conducting studies on different aspects of rice breeding and genetics, including genetic gain, G×E analysis, genome-wide association studies and genomic prediction. Made available in DSpace on 2021-11-30T12:00:26Z (GMT). No. of bitstreams: 1 cropscience-2021.pdf: 1682169 bytes, checksum: e47084fb3060926dd37ca8419b8936da (MD5) Previous issue date: 2021

Genes of tolerance for herbicide has become one of the options more used in world level for the weed control. This study had as objective to evaluated crosses between tolerant irrigated rice plants and sensitive to herbicides of the imidazolinone chemical group, through the evaluation of F2 populations. Five genotypes of irrigated rice were crossed. Three of these parents are sensitive to the herbicide: BRS Querencia, BRS Fronteira and BRS Pampa and two genotypes, BRS Sinuelo CL and Puita INTA CL, tolerant to the herbicide. F1 seeds were obtained in greenhouse, and generation advance was performed in Embrapa Rice and Beans, resulting in the F2 population. F2 plants in the stage V4 received herbicide applications of (Only®) at a dose of 75 and 25 g a.i. L−1, and Dash® in dose of 0.5% v/v. A second application was performed after one week. The degree of phytotoxicity was scored as dead leaves and phytotoxicity intensity, percent survival of leaves and the relative growth. The results showed that the F2 hybrids, resulting of the crosses between the cultivars carriers of the gene of herbicide tolerance of the imidazolinone (Only®) class and conventional irrigated rice cultivars, are viable, thus enabling the establishment of herbicide-tolerant irrigated rice populations, with greater capacity to fight the red rice and with characteristics of agronomic interest. F2 progenies descending from crosses with the cultivar Puita INTA CL presented more tolerance when compared with progenies descending from crosses with the cultivar BRS Sinuelo CL.

BRS Pampa CL is a rice cultivar developed by Embrapa, recommended for irrigated cultivation in Rio Grande do Sul State, Brazil. It shows modern architecture, high tiller ing, early cycle, and tolerance to the imidazolinone herbicide Kifix®. It stands out for its high yield potential and excellent grain quality.

BRS 901 and BRS 902 are red pericarp rice cultivars developed by Embrapa for irrigated and rainfed lowland production systems in Brazil. These cultivars have medium and early maturation cycles, respectively, and both have high grain yield potential, good lodging tolerance and short to medium length grains.

Currently, agronomic practices needed to improve the water efficiency use in irrigated rice crops. The study aimed to evaluate rice cultivars in flood and sprinkler-irrigated system with linear pivot. The experiment was conducted at Embrapa, in Capao do Leao, Rio Grande do Sul (31o48’49”S, 52o28’20”W), in 2011/12 and 2013/14 crop season. It was implemented in the permanent flood-irrigation systems with water blade and sprinkler-irrigation system with linear pivot. Were evaluated the genotypes BRS Atalanta, BRS Querencia, BRS Pampa, BR IRGA 410, BR IRGA 409, BRS Sinuelo CL, BRS Fronteira, BRS 7 ‘Taim’, BRS Pampeira and AB 10101 CL. The parameters evaluated were: grain yield, days to flowering, plant height and percentage of entire grains after industrial processing. The cultivar BRS Pampa stands out in sprinkler-irrigation, while in the flood-irrigation system the cultivar BRS Pampeira presents greater yield potential. The sprinkler-irrigation system with the linear pivot results in an increase in cycle to flowering, reduction in plant height and a 32% reduction in a grain yield compared to flood-irrigation in irrigated rice.

Arsenic (As) mitigation strategies are necessary to decrease As in rice grains. Polishing and washing are important methods to achieve the Codex Alimentarius limits for As. This investigation evaluated a procedure for As-mitigation by removing it from rice grains by polishing and washing for potential implementation in food-industries. It was evaluated the conditions of washing-time, rice:water ratio, temperature, and pH, in which the values were 8 h, 1:2, 35 °C, and 6, respectively. The benefits of the processes, polishing and polishing+washing, were the removal of 13.8/40.5%, 15.6/37.9%, and 41.3/54.6% of As in grains polished during 20s, 40s, and 60s, respectively. Approximately 38.8% of As was removed from the husked grains by simple washing. The As-speciation showed a maximum elimination of inorganic As for grains washed+polished 60s. Regarding Cd and Pb, by comparing non-washed husked grains and washed+polished 60s, the removals were 17% and 66%, respectively. The cost of this procedure was the removal of essential elements. Approximately 83%, 95%, 78%, 58%, 45%, and 33% of Mn, Fe, Co, Cu, Zn, and Se, respectively, were removed. Therefore, it is necessary a balance between benefit and cost when using polishing and washing for As-mitigation, especially for populations that have high rice consumption.

Introduction: The development of tolerant rice genotypes is the main tool to minimize the problem caused by the excess of iron in the soil. Aims: The study aims to evaluate the response of genotypes of the Embrapa breeding program of irrigated rice against iron stress, as well as to envision the relationship of the effect of this disorder on leaf mass production in different phenological phases of the plant. Study Design: The trial was established in a randomized block design with additional controls, with the plots consisting of four rows 3 m long with 0.20 m spacing between rows. Place and Duration of Study: The experiment was conducted in the experimental field of Embrapa Temperate Climate Lowlands Station, in a period of nine years, consisting of the harvest of 2006/2007 until 2014/2015. Methodology: It was evaluated 255 lines along with 4 additional control cultivars with known tolerance levels. The symptoms were evaluated at 40, 70 and 100 days after plant emergence through a visual assessment in the field, based on the standard evaluation system for rice. In addition to the determination of the average toxicity levels of genotypes, the mass was collected, constituted by the dry matter of shoot, for the detection of interrelationships through their correlations. Results: It was found that 58.82% of the developed irrigated rice lines show good tolerance to toxicity by excess iron. The association of the content of dry matter of shoots and the levels of indirect toxicity of iron showed a significant negative correlation (-0.6848), being that the highest magnitude of negative correlation was at 70 DAE (-0.6161). Conclusion: There is variability for tolerance to indirect iron toxicity between the irrigated rice genotypes assessed. The breeding program of irrigated rice of Embrapa has been effective in developing genotypes with tolerance by excess iron in the soil over nine years. There is a negative association between the content of dry matter of shoots and the levels of indirect iron toxicity.

Narrowing of genetic diversity and the quantitative nature of most agronomic traits is a challenge for rice breeding. Genome-wide association studies have a great potential to identify important variation in loci underlying quantitative and complex traits; however, before performing the analysis, it is important to assess parameters of the genotypic data and population under study, to improve the accuracy of the genotype-phenotype associations. The aim of this study was to access the genetic diversity, linkage disequilibrium, and population structure of a working panel of Brazilian and several introduced rice accessions, which are currently being phenotyped for a vast number of traits to undergo association mapping. Ninety-four accessions were genotyped with 7098 SNPs, and after filtering for higher call rates and removing rare variants, 93 accessions and 4973 high-quality SNPs remained for subsequent analyses and association studies. The overall mean of the polymorphic information content, heterozygosity, and gene diversity of the SNPs was comparable to other rice panels. The r2 measure of linkage disequilibrium decayed to 0.25 in approximately 150 kb, a slow decay, explained by the autogamous nature of rice and the small size of the panel. Regarding population structure, eight groups were formed according to Bayesian clustering. Principle components and neighbor-joining analyses were able to distinguish part of the groups formed, mainly regarding the sub-species indica and japonica. Our results demonstrate that the population and SNPs are of high quality for association mapping.

A pesquisa recomenda que o manejo seja realizado de acordo com os estádios de desenvolvimento da planta (EDP). Em geral, a data de ocorrência dos EDP é determinada em experimentos de campo utilizando-se de uma escala fenológica. O objetivo deste trabalho foi determinar o número de dias (ND) para atingir seis EDP, de sete subgrupos de cultivares de arroz irrigado, visando o manejo da cultura. Experimentos de campo foram conduzidos na Embrapa Clima Temperado (ETB), município de Capão do Leão, RS, durante doze safras, utilizando-se seis épocas de semeadura por safra. Dez plantas de cada cultivar foram marcadas e tiveram os EDP determinados durante o ciclo. Os resultados indicaram que o ND para atingir os EDP variou de acordo com os subgrupos sendo que, para alguns estádios, excetuando-se o de quatro folhas (V4), houve diferença estatística entre os subgrupos. O período vegetativo (da emergência-E ao estádio de diferenciação da panícula-R1) representa em torno de 50% do ciclo total, e é o que apresenta as maiores diferenças entre os sete subgrupos de cultivares estudados quando comparado ao período reprodutivo 1 (do estádio R1 à antese-R4) e ao período reprodutivo 2 (do estádio R4 à maturidade completa dos grãos da panícula-R9).

A pesquisa recomenda que o manejo seja realizado de acordo com os estádios de desenvolvimento da planta (EDP). Por serem influenciados pela temperatura, e especialmente o estádio R1 (diferenciação da panícula), recomenda-se expressar os EDP em dias, porém estimados por meio de graus-dia (GD). O objetivo deste trabalho foi determinar os graus-dia necessários para atingir seis EDP de sete subgrupos de cultivares de arroz irrigado. Experimentos de campo foram conduzidos na Embrapa Clima Temperado (ETB), município de Capão do Leão, RS, durante 12 safras, utilizando-se seis épocas de semeadura por safra. Dez plantas de cada cultivar foram marcadas e tiveram os EDP determinados durante o ciclo. Os GD (°C dia) foram calculados por meio do somatório da diferença entre a temperatura média diária do ar (Tm) e a temperatura base (Tb=11°C), da emergência até a data de cada estádio. Os resultados indicaram que os GD para atingir o estádio R1 representaram cerca de 48% do ciclo total (R9), na média dos sete subgrupos, variando de 42% para o subgrupo Muito Precoce 1 a 57% para o subgrupo Tardio. Os GD para atingir cada um dos seis EDP, exceto da emergência ao estádio de quatro folhas (E-V4), variam de acordo com o ciclo das cultivares.

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. 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.

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. Várias cultivares de arroz tem sido desenvolvida no intuito de obter grãos com características de cultivo e composição apropriadas, que são responsáveis pela indicação de uso/consumo dos grãos. Assim, justifica-se a necessidade de caracterização das diferentes cultivares de arroz. No presente estudo, o arroz branco e o farelo de arroz das cultivares BRS AG, BRS Pampa, e BRS 358, cedidas pela EMBRAPA, foram caracterizadas a partir de análises físico-químicas, espectroscopia no infravermelho (FTIR-ATR) e análises térmicas. Nas amostras de arroz branco, o conteúdo de umidade, lipídios e cinzas não diferiu entre as cultivares. A BRS Pampa teve o maior teor de proteínas e o menor teor de carboidratos. A BRS Pampa e BRS 358 tiveram maior teor de ácido fítico. O maior conteúdo de carboidratos observado no arroz branco da cultivar BRS AG confirma sua indicação de uso na produção de bioetanol. Nas amostras de farelo de arroz, a BRS teve maior teor de lipídios, proteínas e ácido fítico, e o menor de carboidratos totais. A análise por FTIR-ATR e análise térmica permitiram correlacionar as propriedades físico-químicas do farelo de arroz e arroz branco com a composição química dentro de cada cultivar estudada. O arroz branco e o farelo de arroz exibiram degradação térmica a 300 °C. O conteúdo de lipídios, proteínas, cinzas e ácido fítico foram superiores no farelo em comparação ao arroz branco para todas as cultivares, o que demonstra a importância do uso desse subproduto.

Grain yield of irrigated rice is a complex character resulting from the expression and association of different components, which should be considered by the breeder for an efficient process of selection of new genotypes. In this sense, the objective is to highlight the phenotypic correlations and the direct and indirect associations of the main components related to crop yield via path analysis. The experiment was carried out in an experimental field of the Lowlands Station of Embrapa Clima Temperado using six genotypes of irrigated rice: the cultivars BRS Pampa, BRS IRGA 409, BRS 7 ‘Taim’, BRS Sinuelo CL, BRS Pampeira and AB 10101 CL. The agronomic characters evaluated were grain yield, days to flowering, panicle length, panicle mass, number of fertile spikelets, number of sterile spikelets, number of tillers per plant, number of panicles per square meter, and mass of one thousand grains. The number of fertile spikelets, number of panicles per square meter, panicle mass and mass of one thousand grains influenced grain yield, both through phenotypic correlation and direct effects. In addition, there was a high direct linear tendency of these variables towards yield. Panicle length and number of sterile spikelets showed a potential of use in the indirect selection for grain yield.

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. Resumo: O objetivo deste trabalho foi determinar o progresso genético de atributos de qualidade de grãos de cultivares de arroz (Oryza sativa) irrigado por inundação no Rio Grande do Sul, entre 1972 e 2016. As estimativas genéticas seguiram a abordagem baseada na análise comparativa das 25 cultivares lançadas pelo programa de melhoramento genético da Embrapa ao longo desse período. O experimento foi implementado em quatro regiões produtoras do Estado do Rio Grande do Sul: Sul, Campanha, Planície Costeira Interna e Planície Costeira Externa. Observaram-se ganhos genéticos significativos de: 0,20% ao ano, para percentual de grãos inteiros após o beneficiamento; -1,38% ao ano, para percentual de grãos gessados e centro branco; -0,77% ao ano, para área gessada total; -0,08% ao ano, para brancura total; e -0,82% ao ano, para brancura não vítrea dos grãos. A maioria das cultivares lançada apresenta alto teor de amilose e baixa temperatura de gelatinização. Portanto, o programa de melhoramento genético apresentou progressos genéticos anuais significativos entre 1972 e 2016 para os principais atributos de qualidade dos grãos, tendo disponibilizado cultivares de acordo com a demanda nacional quanto à qualidade dos grãos nos diversos segmentos da cadeia produtiva do arroz.

The rice cultivar (Oryza sativa L.) BRS AG, developed by Embrapa Clima Temperado, is the first cultivar designed for purposes other than human consumption. It may be used in ethanol production and animal feed. Different abiotic stresses negatively affect plant growth. Soil salinity is responsible for a serious reduction in productivity. Therefore, the objective of this study was to evaluate the gene expression and the activity of antioxidant enzymes (SOD, CAT, APX and GR) and identify their functions in controlling ROS levels in rice plants, cultivar BRS AG, after a saline stress period. The plants were grown in vitro with two NaCl concentrations (0 and 136 mM), collected at 10, 15 and 20 days of cultivation. The results indicated that the activity of the enzymes evaluated promotes protection against oxidative stress. Although, there was an increase of reactive oxygen species, there was no increase in MDA levels. Regarding genes encoding isoforms of antioxidant enzymes, it was observed that OsSOD3-CU/Zn, OsSOD2-Cu/Zn, OsSOD-Cu/Zn, OsSOD4-Cu/Zn, OsSODCc1-Cu/Zn, OsSOD-Fe, OsAPX1, OsCATB and OsGR2 were the most responsive. The increase in the transcription of all genes among evaluated isoforms, except for OsAPX6, which remained stable, contributed to the increase or the maintenance of enzyme activity. Thus, it is possible to infer that the cv. BRS AG has defense mechanisms against salt stress.

The development of rice genotypes with higher mineral content and less accumulation of toxic elements can help to mitigate problems related to mineral deficiency and insure consumption of safe foods. However, genetic improvement depends on the presence of genetic diversity. Therefore, here we characterize a rice panel, grown in southern Brazil, regarding iron (Fe), zinc (Zn), selenium (Se), manganese (Mn), copper (Cu), arsenic (As), cadmium (Cd) and lead (Pb) content in irrigated system with permanent flooding. The environment of each harvest season significantly influenced Cu, Zn, Se, Fe and Mn content in rice grains. None of the analyzed rice genotypes can meet the daily recommendation of Fe and Zn, being the highest contents detected for these mineral of ∼17 and ∼27 mg kg−1, respectively. We detected genotypes able to supply Mn, Cu and Se demand, and genotypes accumulating ∼37, ∼5, ∼0.200 mg kg−1 were detected, respectively. None of the analyzed genotypes showed Cd and Pb accumulation above the Brazilian allowed limits. However, As content was above of the allowed limit for most of the studied accessions, and some genotypes reached 1 mg kg−1of As in their grains. Among the genotypes, low genetic diversity was detected for the evaluated elements.

The aim of this study was to verify differences in the tolerance to suboptimal temperatures of eight rice mutant genotypes in relation to their cultivars of origin in the initial stages of development. During the germination period, the germination percentage and the germination rate index were evaluated at temperatures of 25 and 13°C. For the vegetative stage enzymatic indicators, photosynthetic pigment concentration and electrolyte leakage were verified. The relative decrease in the germination percentage of mutants QUE 47, QUE 30 and QUE 33 was significantly lower (p ≤ 0.01) than that of cv. BRS Querencia. The principal component analysis using the values of the relative decreases of the germination percentage and of the germination rate index confirmed this distinction and the mentioned genotypes were classified into the group with a higher cold tolerance than BRS Querencia. The BRS Fronteira genotype did not differ from its mutants for the variables analyzed during germination. In the vegetative stage there were no differences (p ≤ 0.05) between the mutant genotypes and BRS Querencia for the analyzed variables. The induced mutation increased the tolerance to suboptimal temperature in the germination period in the genotypes QUE 47, QUE 30 and QUE 33, but not for the vegetative stage. Key words: Oryza sativa, mutation, abiotic stress, low temperature.

BRS Catiana is an irrigated rice cultivar with a medium cycle and excellent grain quality, suited for cultivation in 17 Brazilian states. It has a high yield potential (15,535 kg ha-1) and a mean yield of 7,253 kg ha-1, wide adaptation and late senescence (stay green trait). Made available in DSpace on 2019-10-25T18:08:55Z (GMT). No. of bitstreams: 1 CNPAF20191cbab.pdf: 249327 bytes, checksum: 0aeff44a94169d1b1b0b4693f11547fb (MD5) Previous issue date: 2019

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.

A recomendação da pesquisa é que as práticas de manejo do arroz irrigado sejam realizadas de acordo com os estádios de desenvolvimento da planta. O problema é que a ocorrência desses estádios é variável, por ser dependente da temperatura. Por isso, é preferível estimá-los por meio de soma térmica, ou graus-dia, ao invés do número de dias do calendário. O objetivo deste trabalho foi determinar o número de dias e a soma térmica necessários para atingir seis estádios de desenvolvimento da planta, de quatro grupos, envolvendo 34 cultivares. Experimentos de campo foram conduzidos na Embrapa Clima Temperado (ETB), município de Capão do Leão, RS, durante doze safras. Dez plantas de cada cultivar foram marcadas e tiveram o desen­volvimento acompanhado durante o ciclo. Os graus-dia foram calculados através do somatório da diferença entre a temperatura média diária (Tm) e a temperatura base inferior (Tb) de 11ºC, da emergência até a data de cada estádio. Os resultados indicam que o número de dias e a soma térmica necessários para atingir os seis es­tádios da planta variam de acordo com o comprimento de ciclo das cultivares, sendo menores no grupo Muito Precoce, intermediários nos grupos Precoce e Médio e maiores no grupo Tardio.

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.

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. Resumo: O objetivo deste trabalho foi estimar os efeitos da interação genótipo x ambiente e o potencial genotípico de cultivares de arroz irrigado por inundação, lançadas entre 1972 e 2017, para o Rio Grande do Sul. Os experimentos foram realizados em campo, em todas as regiões agroclimáticas de cultivo de arroz irrigado por inundação do estado, entre os anos agrícolas de 2005/2006 e 2015/2016, no total de 60 ambientes, com 1.961 unidades experimentais. Vinte e cinco cultivares de arroz irrigado foram avaliadas quanto aos caracteres produtividade de grãos, altura de plantas, dias para o florescimento e qualidade de grãos inteiros após o beneficiamento. Os valores de adaptabilidade e estabilidade foram estimados por meio de modelos mistos. As cultivares de arroz BRS Pampa, BRS Pampeira e BRSCIRAD 302 apresentaram, simultaneamente, alta produtividade genotípica de grãos, adaptabilidade, estabilidade, bons atributos agronômicos e bom rendimento de grãos inteiros após o beneficiamento. 'BRSCIRAD 302' e 'BRS Pampa' apresentam alta estabilidade produtiva e podem ser recomendadas para cultivo em todas as regiões orizícolas do Rio Grande do Sul. 'BRS Pampeira' é responsiva às melhorias do ambiente e é indicada para condições de alta tecnologia.

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. 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.