Estratégias para análise do comportamento de genótipos de soja ao nematoide de cistos (Heterodera glycines) / Strategies for analysis the behavior of soybean genotypes to the cyst nematode (Heterodera glycines)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The objectives of this study were the following ones: to evaluate the stability of the soybean cyst nematode race (H. glycines) from the Nematode Bank of the Soybean Breeding Program by the Federal University of Viçosa (NBSBP-FUV), that is kept under greenhouse conditions; to select the soybean genotypes that were originated by one-single pod descending method and are resistant to the cyst nematode; to evaluate the genetic diversity among genotypes; and to compare the eggs-inoculation methodology to the soil artificialinfestation with the cyst nematode in selecting the resistant genotypes. Two experiments were carried out under greenhouse conditions during the agricultural year 2008/2009, as being one with egg inoculation and another with artificial soil infestation with the cyst nematode. The cyst nematode populations were collected in NBSBP-FUV. Twenty-seven soybean genotypes originated by onepod descendent method were evaluated. The entirely randomized design was used, with six replicates. Each experimental unit was represented by one plant cropped in a pot. Based on female index in the differentiating series (Lee 74, Pickett, Peking, PI88788, PI90763 and Hartwig), the race 3 was found to be predominant and remained stable for 12 years. The egg-inoculated genotypes were evaluated for numbers of the females, eggs, eggs by female, plant height, node numbers, and the weights of the green matter and dry matter. In the experiment from which the soil was artificially infested with the cyst nematode, the number of females were artificially counted by three appraisers with the aid of a magnifying glass (6X increase). Besides counting the number of females, one of those researchers evaluated the female numbers and the vigor of both root and plant, by using the visual scale as base. Besides those characters, also the plant height, the node numbers, the weights of either green matter and dry matter were evaluated. The data were subjected to variance analysis. Then, the genotypes were grouped, by applying the Scott-Knott test. The genotypic determination coefficients as well as the phenotypic, genotypic and environmental correlations and the dissimilarity measures (Mahalanobis Distance) were also estimated in order to evaluate the genetic diversity by either the hierarchical method (Unweighted pair-group method using arithmetic averages - UPGMA) and the Tocher optimization method. The superior genotypes developed by the descendent method of one single pod by plant kept the genetic variability for resistance to the cyst nematode. High genotypic and phenotypic correlations were verified between female numbers and egg numbers evaluated in the genotypes artificially inoculated with eggs of the cyst nematode and among the number of females obtained by the evaluators A, B and C, by the average obtained by evaluators and by the visual note of the female numbers. In genetic diversity analyzes, the genetic variability was detected among genotypes, as Lee74 and BCR945G110 showing higher dissimilarity. Concerning to the genotypes that were resistant to the cyst nematode, race 3, BCR945G110 and BCR1070G229 and the moderately resistant genotypes BCR132390, BCR945G114 and BCR1057G163, it was verified that 20.83% are resistant to the predominant race in the soybean-producing areas in Brazil. No differences occurred among the number of females counted by evaluators, which shows this evaluation can be accomplished by just one previously trained evaluator. The egg inoculation methodologies associated with extraction methodology and the soil artificial infestation associated with visual counting for the analysis of the soybean genotype behavior were generally coherent with each other.

ASSUNTO(S)

diversidade genética nematóide de cistos genetic diversity metodologias melhoramento vegetal correlations metodologys correlações soja cyst nematode soybean

ACESSO AO ARTIGO

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