The objective of this study was to estimate the results ofthe upland rice {Oryza sativa L.) breeding program conducted by the Brazilian Agricultural Research Corporation (Embrapa) and collaborators over the period of 1984 to 2009 covering 25 annual steps of improvement. The best lines generated by this program are evaluated in "value for cultivation and use (VCU) trials." This study used data from 603 VCU trials conducted in seven Brazilian States. The group of lines entering VCU in each year was faken as a sample of the elife program in that year. Best linear unbiased estimates (BLUEs) of the means of groups were computed, and the regression of the BLUEs on years was taken as an estimate of the efficiency of the breeding program.

The relative performance of one genotype is not identical in different environments due to genotype-environment interaction (G9E). Thus, for a breeding program to successfully develop cultivars, it is fundamental that candidate elite-lines are tested in several target environments and that the data are analysed for yield, adaptability and stability. The objective of this work was to study the G9E for upland rice using a mixed model and, using the harmonic mean of relative performance of genotypic values (HMRPGV) method, to analyse cultivars and elite-lines over time to identify those that aggregate high grain yield (GY) with high genotypic adaptability and stability. A large dataset of ''value for cultivation and use trials'' collected by the Brazilian Agricultural Research Corporation (Embrapa) and collaborators from 1984 to 2010, involving seven states that represent upland rice crops in the Midwest, North and Northeast regions of Brazil, was used. The effect of location was shown to be more important than the effect of year for promoting crossover interaction. The CNA 8555 had the best GY associated with adaptability and stability, presenting a superiority of 13.28 % above the general mean of all elite-lines. Using already-released cultivars and potential elite-lines, the generalised linear regression analysis revealed significant progress of the stability and adaptability associated with GY over time. The HMRPGV method was shown to be an important tool and allowed identification of three elite-lines in the Embrapa pipeline (AB 062008, AB 062041 and AB 062037), each with high stability, adaptability and yield potential to be released commercially.Keywords Oryza sativa Á HMRPGV Á BLUP Á REML Á G9E Á Genetic progress Abbreviations BLUPBest linear unbiased predictor REML Restricted maximum likelihood GY Grain yield VCU Value for cultivation and use G9EGenotype-environment interaction G9LGenotype-location interaction G9YGenotype-year interaction G9L9YGenotype-location-year interaction HMRPGV Harmonic mean of relative performance of genotypic values

O objetivo deste trabalho foi avaliar, por meio de análise dialélica, o potencial de dez variedades de arroz-vermelho para a implementação de um programa de melhoramento. A identificação de genitores foi feita com dez variedades, em um cruzamento dialélico completo sem recíprocos. As variedades e seus 45 cruzamentos foram avaliados nas gerações F1 e F3, quanto às suas características agronômicas, em delineamento em blocos ao acaso. Para o caráter produção de grãos, foram avaliados: a heterose do cruzamento (H), o efeito varietal (v), a heterose média (h), a heterose varietal (h) e a heterose específica (s) em cada geração, além da capacidade geral de combinação (g) dos genitores. Foram detectadas diferenças significativas entre as variedades genitoras, quanto às características agronômicas avaliadas, e foram considerados mais promissores, para a seleção de novas linhagens, os cruzamentos 'AL03/PB13' e 'PB05/PB10', em razão das estimativas favoráveis dos parâmetros relacionados à produtividade, à diversidade genética e à capacidade de combinação de seus genitores.

The largest numbers of the Brazilian traditional upland rice varieties are found in the Maranhão state, Northeast region of Brazil. However, no information is available on the diazotrophic bacterial population associated as well as the plant growth promoting potential when these traditional genotypes are inoculated with native strains. Here, we evaluated the response of ten traditional rice varieties to inoculation with ten diazotrophic strains, previously isolated from rice soil of this region and screened for their ability to produce indole-3-acetic acid (IAA) in vitro. The procedure for selection of the best diazotrophic strain/rice variety interaction involved three steps: gnotobiotic conditions, soil pot and field experiments. The gnotobiotic experiment showed that the Azospirillum amazonense strain AR3122 increased the biomass of the traditional varieties Cana Roxa and Cana Forte (28 and 48%, respectively) while this effect was less evident for the other combination of strains/rice varieties. The soil pot experiment showed that the combination of Burkholderia vietnamiensis strain AR 1122 and traditional variety Arroz 70 was superior to the other strains/varieties and the treatment fertilized with 100 kg N ha −1. The best performance of the Burkholderia vietnamiensis strain AR1122/variety Arroz 70 was confirmed in the field experiment. There was an increase of up 10 and 29% in the grain yield in comparison to both the N fertilization and Herbaspirillum seropedicae ZAE 94 strain treatments, respectively. In contrast, the response of the commercial variety Bonanç a to inoculation with strain AR1122 was much lower, suggesting that a biofertilizer inoculation program for traditional rice varieties should consider the genetic interaction between strain and rice variety. The diazotrophic B. vietmaniensis strain AR1122 was a good biofertilizer candidate for inoculation of traditional rice varieties and therefore should be used for further studies to confirm the strain-genotype effect envisaging a sustainable rice crop system mainly in the Northeast region of Brazil.

Periodic assessment of the genetic progress made in recurrent selection programs is essential for assessing the evolution of the programs and identifying the main factors that have contributed to this progress. This study aimed to estimate genetic progress in grain yield, plant height and days-to-flowering achieved in the CNA6 population of upland rice (Oryza sativa L.), after four cycles of recurrent selection; and evaluate the genetic potential of this population to generate superior inbred lines after each selection cycle. The experimental data were obtained from progeny yield trials of each recurrent selection cycle. These trials were carried out in two or three locations per cycle, and consisted of S 0:2 progenies and at least three checks. Federer's augmented block design, with one replication on location (the environment), was adopted.Results revealed genetic progress for grain yield and plant height, with total genetic gains of 375.87 kg ha −1 and -3.90 cm, respectively, during the four selection cycles. The annual relative gain observed for grain yield was 1.54 %. The genetic potential of the population was analysed by the expected proportion of superior inbred lines. The standard adopted as the limit for obtaining superior inbred lines was the average of the checks for each trait. The genetic potential for grain yield and plant height increased during the study period. For days-to-flowering, no genetic gain occurred; however, the genetic potential of the population to generate superior inbred lines for this trait was maintained after the selection cycles.

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Termos para indexação: Oryza sativa, ganho genético, correlações genéticas, parâmetros genéticos, cultivares. GENETIC GAINS FOR GRAIN YIELD BY IRRIGATED RICE BREEDING PROGRAM IN THE MID-NORTH REGION OF BRAZILABSTRACT -Data from 37 advanced yield trials, conducted from 1984 to 1997, were analyzed to evaluate the genetic progress made by the Brazilian Mid-north Region irrigated rice (Oryza sativa L.) breeding program. The following traits were measured: grain yield, days to flowering, plant height, and lodging. These trials had 89 breeding lines and two checks ('Cica 8' and 'Metica 1'). During these 14 years of experiments, the annual gain for grain yield was small and equal to 0.3%, but statistically significant (P < 0.05). The genetic correlations estimated by the conventional and indirect methods were similar. Out of the six cultivars recommended for the region during this period, the cultivar Diamante provided significant gains for grain quality, when compared to the checks. (Levantamento, 1996). Apesar da baixa representatividade em termos de Brasil, o arroz irrigado desta região tem grande importância econômica e social para os pequenos agricultores, predominantes na região. Por ser uma cultura cuja produção independe das variações climáticas, principalmente da ausência de chuvas por longos períodos (secas), tão comum na região, o arroz irrigado funciona como elemento agregador e fixador do homem à terra, evitando com isto o êxodo rural e garantindo o sustento de inúmeras famílias nordestinas.

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