Citogenética em Catteya intermedia Lindl.

37

The induction of polyploidy in cassava

A poliploidia teve importante papel no melhoramento de muitas espécies de plantas, principalmente nos cereais, incluindo híbridos intergenéricos. O processo de poliploidização, geralmente, produz novos e desejáveis fenótipos ou fornece suporte para cruzamentos de plantas em programas de melhoramento. Esse trabalho apresenta o resultado da indução de poliploidia em duas cultivares de mandioca (\'Porquinho\' e \'Vassourinha\') que foram tratadas com diferentes concentrações de colchicina (0,05%, 0,10% e 0,15%), em meio de cultura, durante 48 e 96 horas. As plantas regeneradas foram analisadas citologicamente por citometria de fluxo e pela contagem do número de cromossomos. Adicionalmente, análises do tamanho e da frequência dos estômatos foram realizadas e o resultado comprovou que podem ser utilizadas como screening das plantas tratadas. O tratamento com 0,1% de colchicina, em meio de cultura, durante 96 horas apresentou maior número de plantas tetraplóides produzidas sobre o número de plantas regeneradas nas duas cultivares avaliadas. Não há diferenças entre as doses de colchicina e tempos de exposição a droga no número de tetraplóides encontrados em cada tratamento. Entretanto, foi possível verificar que existe diferença significativa na produção de tetraplóides entre as cultivares analisadas, indicando que pode haver uma resposta genética à indução da duplicação dos cromossomos com colchicina.The polyploidy played an important role in the improvement of many species of plants, especially in cereals including intergeneric hybrids. The process of polyploidy usually produces new and desirable phenotypes or provides support for crosses of plants in breeding programs. This research work reports the result of polyploidy induction in two cassava cultivars (\'Porquinho\' and \'Vassourinha\') by different colchicine concentrations (0.05 %, 0.10 % and 0.15 %) in culture medium exposed for 48 or 96 hours. Regenerated plants were examined cytologically by flow cytometry and chromosome counting. Additionally, analysis of the size and frequency of stomata were performed and the results showed that can be used for screening of the treated plants. Treatment with 0.1% colchicine in the culture medium for 96 hours showed a higher number of tetraploid plants produced about the number of regenerated plants in both cultivars evaluated. No significant differences among colchicine doses and duration times treatment were found in the number of tetraploids found in each treatment. However, we observed a significant difference in tetraploid production between the cultivars analyzed, indicating that there may be a genetic response to induction of chromosome doubling with colchicine

Citogenética em Catteya intermedia Lindl.

37

Induction and identification of polyploids in Cattleya intermedia Lindl. (Orchidaceae) by in vitro techniques

The effect of colchicine on the protocorm-like bodies of Cattleya intermedia L. (Orchidaceae) cultured in vitro was studied. Different concentrations of the drug (0.00, 0.05, 0.10 and 0.20%) as well as two times of culture (4 or 8 days) were tested to determine the best treatment for the induction of tetraploid plants. Of the 3 colchicine levels applied, 0.05 and 0.10% of drug treatments appeared to be effective on the production of mixoploids and tetraploids and could be further used in breeding programs. The suitability of stomatal area and stomata density as criteria for the distinction between diploids and tetraploids was also tested. The results suggested that tetraploid plants could be identified with a fair amount of certainty when the screening was based on the density of stomata