RESUMO -Este trabalho objetivou estimar o ganho genético obtido pelo programa de melhoramento de arroz de sequeiro (Oryza sativa L.) desenvolvido em Minas Gerais cooperativamente pela Epamig/Embrapa-Centro Nacional de Pesquisa de Arroz e Feijão (CNPAF)/UFLA/UFV, no período de 1974/75 a 1994/95. Para tanto, utilizaram-se os dados dos ensaios comparativos avançados de cultivares e linhagens de arroz de sequeiro conduzidos no referido período. Em virtude da distribuição irregular de chuvas e da resposta diferenciada dos materiais de ciclos diferentes às condições climáticas, optouse por dividi-los em dois grupos; um contendo os genótipos precoces e o outro os de ciclo médio. Os resultados alcançados mostraram que ocorreu um ganho genético médio anual de 1,26% e de 3,37% em relação ao grupo precoce e ao de ciclo médio, respectivamente. O grupo precoce superou estatisticamente (P≤0,01) em produtividade de grãos o grupo de ciclo médio, indicando que em Minas Gerais deve-se dar preferência ao plantio de cultivares de ciclo curto.Termos para indexação: Oryza sativa, ganho genético, avaliação de genótipos, cultivar. GENETIC PROGRESS OBTAINED BY UPLAND RICE BREEDING IN TWENTY ONE YEARS OF RESEARCH IN THE STATE OF MINAS GERAIS, BRAZILABSTRACT -This work aimed to estimate the genetic gain obtained by the upland rice (Oryza sativa L.) breeding program developed in Minas Gerais State, Brazil, in cooperation with Empresa de Pesquisa Agropecuária de Minas Gerais (Epamig), Embrapa-Centro Nacional de Pesquisa de Arroz e Feijão (CNPAF), Universidade Federal de Lavras (UFLA) and Universidade Federal de Viçosa (UFV), from 1974/75 to 1994/95. Results of the comparative trials of upland rice cultivars and lines conducted over the above quoted period were utilized. Because of irregular rainfall distribuition and the distinctive response of different cycles to climatic conditions, the option was to divide them into two groups, one encompassing the early genotypes and the other those of medium cycle. The achieved result showed that an average genetic gain of 1.26% and 3.37% for the early group and medium cycle, respectively, occurred. In addition, it was found that the early group statistically outyielded (P ≤ 0.01) as to grains the medium cycle group, denoting that in Minas Gerais the short cycle cultivars should be preferred.
This study presents self-organizing maps (SOM) as an alternative method to evaluate genetic diversity in plant breeding programs. Twenty-five genotypes were evaluated in two environments for 11 phenotypic traits. The genotypes were clustered according to the SOM technique, with variable topology and numbers of neurons. In addition to the SOM analysis, unweighted pair group method with arithmetic mean clustering (UPGMA) was performed to observe the behavior of the clustering when submitted to these techniques and to evaluate their complementarities. Genotype ordering according to SOM was consistent with UPGMA results, evidenced by the basic structure of UPGMA groups being preserved in each group of the maps. Regarding genotype arrangement and the group neighbors, maps involving five neurons presented inferior organization efficiency compared to the six-map arrangements in both environments. It was observed that the organization pattern among the rice genotypes evaluated by the maps was complementary to the UPGMA approach, as observed in all scenarios. It can be concluded that self-organizing maps have the potential to be useful for genetic diversity studies in breeding programs.
An evaluation of the genetic improvement program of irrigated rice of Minas Gerais estimated the genetic gain obtained in the 90s. Grain yield data of the advanced comparative trials of cultivars and lines of continuously flooded rice, conducted from 1990/91 to 2000/01 were used. The estimate of the genetic gain was obtained by the methodology of the adjusted means proposed by Breseghello (1998). The mean annual genetic gain in the 90s was 42.45 ± 17.89 kg ha -1 (0.7% per year). The improvement program proved auspicious for the development of lines that outmatched the controls. The mean of the cultivars released in the 90s did however not outstrip the mean of the elite lines, which were the genotypes with the highest means in this study and will be further evaluated in the ongoing program.
Termos para indexação: Oryza sativa, ganho genético, avaliação de genótipos. EVALUATION OF THE GENETICAL PROGRESS OBTAINED IN 22 YEARS ON THE IMPROVEMENT OF IRRIGATED RICE IN MINAS GERAIS, BRAZILABSTRACT -The goal of this work was to evaluate the performance of the genetical improvement program of irrigated rice in the State of Minas Gerais, Brazil. The grain yield data of the advanced comparative trials of both cultivars and lines of irrigated rice, conducted in several regions of the State of Minas Gerais over the period of 1974/75 to 1995/1996 were utilized. The average genetical gain obtained was of 33 kg/ha/year (0.98%), being highly significant (P< 0.01). The 22 year period was subdivided into two phases: at the first phase (1974/75 to 1979/80), a gain of 203 kg/ha/year (6.06%) was noticed, which was highly significant, and the second phase (1980/81 to 1995/96) presented a gain of 15 kg/ha/year (0.25%) being non significant. The high gain of the first phase is ascribed to the replacement of traditional high size and poor yielding potential for breeding materials such as Inca, BG 90-2 and MG 2. In the second phase of the program, increased attention was given to obtain materials more resistant to diseases and with better grain quality and non-significant gains for yield were obtained.
RESUMO: O arroz (Oryza sativa) representa um dos mais importantes grãos em termos de valor econômico, destacando-se como o segundo cereal mais cultivado e um dos mais consumidos em todo mundo. O objetivo deste trabalho foi propor o método de Projeção de Distâncias, para auxiliar na classificação de genótipos de arroz irrigado quanto à adaptabilidade e estabilidade. O delineamento utilizado foi de blocos casualizados em três locais e avaliados em quatro anos, perfazendo um total de 12 ambientes. Previamente foram realizadas análise de variância e análises de adaptabilidade e estabilidade por meio dos Métodos de Eberhart e Russel (1966) e Centroide para posteriores análises gráficas por meio do Método de Projeção de Distâncias proposto neste estudo. As projeções foram construídas sob dois princípios, a saber, complemento do coeficiente de determinação ou distância de Gower. Os resultados indicaram grandes potencialidades do método gráfico proposto. As representações gráficas fornecidas pelo método Projeção de Distâncias, facilitaram o reconhecimento do padrão de interação G x E dos genótipos de arroz avaliados, tendo em vista as dificuldades de interpretação e discordância entre os resultados das metodologias de Eberhart e Russell e Centroide. PALAVRAS-CHAVE: Oryza sativa; classificação; interação G×E; zoneamento. IntroduçãoO arroz (Oryza sativa) constitui um dos alimentos de melhor balanceamento nutricional, sendo capaz de fornecer 20% da energia e 15 % da proteína per capita necessária ao homem, destacando tal cultura como o segundo cereal mais cultivado e um dos mais consumidos em todo mundo (WALTER et al., 2008). Por ser uma cultura que se
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