Colchicine and oryzalin effects on tetraploid induction and leaf anatomy of Solanum commersonii ssp.Ciência Rural, v.46, n.11, nov, 2016. 1973Colchicine and oryzalin effects on tetraploid induction and leaf anatomy of Solanum commersonii ssp.

ABSTRACT. Methods to obtain phenotypic information were evaluated to help breeders choosing the best methodology for analysis of genetic diversity in backcross populations. Phenotypes were simulated for 13 characteristics generated in 10 populations with 100 individuals each. Genotypic information was generated from 100 loci of which 20 were taken at random to determine the characteristics expressing two alleles. Dissimilarity measures were calculated, and genetic diversity was analyzed through hierarchical clustering and graphic projection of the distances. A backcross was performed from the two most divergent populations. A set of characteristics with variable heritability was taken into account. The environmental effect was simulated assuming ~ (0, ). For hierarchical clusters, the following methods were used: Gower Method, average linkage within the cluster, average linkage among clusters, the furthest neighbor method, the nearest neighbor method, Ward's method, and the median method. The environmental effect and heritability of the analyzed variables had an influence on the pattern of hierarchical clustering populations according to the backcrossed generations. The nearest neighbor method was the most efficient in reconstructing the system of backcrossing, and it presented the highest cophenetic correlation. The efficiency of the nearest neighbor method was the highest when the analysis involved characteristics of high heritability.Keywords: hierarchical clustering, genetic diversity, backcrossing.Agrupamentos genéticos hierárquicos para análises fenotípicas RESUMO. Visando auxiliar o melhorista na escolha da melhor metodologia para análises de diversidade genética em populações de retrocruzamento avaliaram-se os métodos baseados em informações fenotípicas. Os fenótipos foram simulados para 13 características, geradas em 10 populações com 100 indivíduos cada. Geraram-se informações genotípicas de 100 locos, dos quais 20 foram tomados ao acaso para determinar as características, manifestando dois alelos. Medidas de dissimilaridade foram calculadas, e analisou-se a diversidade genética por meio agrupamento hierárquico e projeção gráfica das distâncias. A partir das duas populações mais divergentes fez-se o retrocruzamento. Considerou-se um conjunto de características com herdabilidade variável. Simulou-se o efeito ambiental admitindo distribuição normal, com média zero e variância . Para as análises de agrupamentos hierárquicos utilizaram-se os métodos: Método de Gower, Ligação média dentro de grupo, Ligação média entre grupo, Vizinho mais distante, Vizinho mais próximo, Método de Ward, Método da mediana. O efeito ambiental e a herdabilidade das variáveis analisadas influenciaram o padrão de agrupamento de populações sob retrocruzamento. Em características de herdabilidade elevada, o método do Vizinho mais próximo foi o mais eficiente em reconstituir o retrocruzamento, além de ter apresentado a maior correlação cofenética, sendo considerada a melhor metodologia a priori e a posteriori.Palavras-chave: métodos ...

-Meiotic abnormalities in potato hamper sexual recombination, due to their influence on pollen production and viability rate. In this study we evaluated pollen viability and meiosis of three clones of Solanum commersonii commersonii Dun. (SCC), two of Solanum commersonii malmeanum Bitt. (SCM) and seven clones and four cultivars of Solanum tuberosum L., with the purpose of indicating promising genotypes for genetic breeding of potato. Early chromosome migration at metaphases I and II and chromosome pairing anomalies were the main causes of pollen inviability in the evaluated genotypes. Clones SCC 07 and SCM 60 are the most suitable for sexual recombination, owing to the high percentage of viable pollen grains and low frequencies of meiotic abnormalities.

RESUMOSolanum commersonii subsp. Termos para indexação: Batata, pólen não reduzido, melhoramento genético vegetal. ABSTRACTSolanum commersonii subsp. commersonii Dun. and Solanum commersonii subsp. malmeanum Bitt. (2n=2x=24 -1EBN) cannot be directly crossed with the cultivated Solanum tuberosum subsp. Tuberosum L. (2n=4x=48 -4EBN) species due to ploidy barriers and endosperm balance number (EBN). However, non-reduced pollen production by the wild species S. commersonii ssp. (2x=2n=24 -1EBN), allows the crossing of these species with dihaploids of potato and with the diploids species, S. phureja Juz.&Bukasov. and S. chacoense Bitt., all with 2EBN. The aim of this work was to determine the meiotic mechanism and frequency of non-reduced pollen production of five clones of S. commersonii ssp. Three different clones of S. commersonii subsp. commersonii Dun. (SCC) and two of S. commersonii subsp. malmeanum Bitt. (SCM) were evaluated. In the evaluation, two hundred viable pollen grains were stained (2% acetic carmin) and measured. The pollen grains measuring 25 µm in diameter or more were considered nonreduced. The clone Solanum commersonii subsp. commersonii Dun. (SCC 100) produces 26.1% of non-reduced pollen grains caused by parallel spindles and fusion spindles, which may be used in breeding program.