Abstract
Soil salinity is a limiting factor for rice cultivation, especially in the early stages of development and the flowering period. The use of sources of poor quality water for irrigation results in the accumulation of salts in the soil, causing major toxicity in culture. A solution to the problem would be the introduction of varieties with tolerance to high salinity. Hus the aim of this work is to evaluate genetic divergence among rice genotypes, aiming at the selection of genotypes tolerant to salinity during the vegetative phase. Seeds of 10 rice genotypes were grown in vitro on MS medium supplemented with 0 and 136 mM NaCl. After 21 days, six morphological characters were evaluated and the results subjected to multivariate analysis. The methods of Tocher, based on Mahalanobis distance, and graphic dispersion of canonic variables followed the same pattern of clustering structure, forming six groups. The characteristic of shoot fresh weight was the largest contributor to the genetic dissimilarity between genotypes by the method of Singh, while the other two canonic variables were sufficient to account for 91.27% of observed variation. Under the experimental conditions tested, the genotypes showed different degrees of salinity tolerance, while Colossus BRS, BRS Bojuru and BR IRGA 410, belonging to the groups three and four, were those who were more tolerant genotype and Moti, belonging to two what was more sensitive to salt stress.
Highlights
Soil salinity is a limiting factor for rice cultivation, especially in the early stages of development and the flowering period
Em câmara de fluxo laminar, as sementes foram colocadas para germinar em tubos de ensaio contendo 5 mL de meio MS
Ambos pertencem ao grupo japônica e apresentaram comportamento semelhante para os caracteres número de raízes, massa fresca da parte aérea e do sistema radicular, sendo observados, no genótipo Moti, os maiores valores percentuais de redução para a maioria das variáveis
Summary
O experimento foi conduzido no Laboratório de Cultura de Tecidos pertencente ao Departamento de Botânica, Instituto de Biologia da Universidade Federal de Pelotas (UFPEL), localizado no município de Pelotas-RS. Em câmara de fluxo laminar, as sementes foram colocadas para germinar em tubos de ensaio contendo 5 mL de meio MS Os tratamentos foram constituídos por duas concentrações de NaCl acrescidos ao meio de cultura. As concentrações utilizadas foram 0 (testemunha) e 136 mM (8 g L-1) de NaCl. Após o preparo de cada meio o pH destes foi ajustado para 5,8. O delineamento experimental utilizado foi o inteiramente casualizado com cinco repetições por tratamento, sendo cada uma delas representada por cinco tubos, contendo uma semente cada. Para esses caracteres foram realizados cálculos percentuais de desempenho relativo (aumento ou redução), considerando-se 100% o valor absoluto do tratamento controle (0 mM de NaCl), com a finalidade de observar o comportamento diferencial dos genótipos frente ao estresse. As análises foram realizadas utilizando o programa computacional Genes, versão 2007 (CRUZ, 2007)
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