Effects of hormones applications on the germination of six populations of Garcinia kola Heckel (Guttiferae) seeds

The present study was carried out to investigate laboratory germination responses of six collections of Garcinia kola seeds to six different hormonal pre-germination treatments. This consisted of soaking seeds for three days in cool distilled water (control), in cool distilled water supplemented with 10-4 M of either naphthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), benzylaminopurin (BAP), kinetin (Kin) or gibberellic aicid 3 (GA3). The results showed that the pre-germination treatments had profound effects on the phenology of Garcinia kola seeds germination. Multiple shoots, multiple roots and callus formation were induced from seeds soaked in benzylaminopurin, naphthaleneacetic acid and 2,4-dichlorophenoxyacetic acid solutions, respectively. Analysis of variance showed a significant (p < 0.01) effect of seed collection on the germination velocity, indicating the variability in seed dormancy among collections. Although the rate of germination was higher in seeds treated with NAA, none of the seed treatments significantly enhanced germination when compared with the control. Keywords: Bitter kola, auxins, cytokinins, gibberellic acid, phenology, variable dormancy. International Journal of Biological and Chemical Sciences Vol. 1 (3) 2007: pp. 255-26

VARIATION OF b-1,3-GLUCANASE, CHITINASE AND POLYPHENOLOXIDASE ACTIVITIES IN CACAO PODS UPON Phytophthora megakarya INOCULATION

Cacao (Theobroma cacao   L.) clones that differ in susceptibility to black pod disease were analysed for response to stress induced by pod inoculation with the fungus Phytophthora megakarya   Braz. Et Griff. Fungal inoculation significantly stimulated β-1,3-glucanase activity in both soluble and ionically-bound fractions of the less susceptible clones. No significant correlation was found in the other clones. Chitinase activity in both soluble and ionically-bound fractions was generally reduced upon pod inoculation with the fungus, but this pattern did not correlate with disease severity. Polyphenoloxidase activity, following pod inoculation, was genotype dependent in the soluble fractions, whereas in the ionically-bound fractions, stimulation of this activity was recorded in the less susceptible clones. Moreover, pod inoculation was characterised by the appearance of a new polyphenoloxidase isoform A'2 in the less susceptible clones

Amino acids, carbohydrates and heritability of resistance in Theobroma cacao/ Phythophtora megakarya interaction.

The black pod disease of cocoa (Theobroma cacao), caused by Phythophthora megakarya, is responsible for 80% loss of cocoa production in Cameroon. The principal method of ameliorating crop losses is through the use of black pod resistant and high productivity hybrid cocao clones. In order to assess the possible role of amino acids and carbohydrates in the defence of T. cacao against P. megakarya, comparative analyses (quantitative and qualitative) of sugars and amino acids were carried out on leaves of parental genotypes, ICS95, ICS84 and hybrids (families F25:♀ICS84 X ♂ICS95 and F30: ♀ICS95 X ♂ICS84 ). A reduction in soluble sugar contents of parental genotypes ICS84, ICS95 and 30% of hybrid genotypes was noted under conditions of infection. Qualitative analyses of sugars showed that most cases of infection were characterized by the disappearance of sucrose and the persistence of glucose. Amino acids content increased in 70% of genotypes after injury or infection. In parental tolerant clone ICS84 and hybrid genotypes F3011, F2551 and F2552, proline appeared solely during conditions of infection, suggesting its implication in the defence mechanism of T. cacao against P. megakarya. A significant positive relationship was observed between amino acid contents and the severity of necrosis. There was a very weak relationship between sugar and amino acid contents in parental genotype, and those of the progeny. PCA of the length of necrosis, sugar level, amino acids and phenolics showed that under infection, the increase in content of phenolic compound was concomitant with reduction in amino acid content

Tuber formation and development of Dioscorea cayenensis-D. rotundata complex in vitro. Effect of polyamines.

Tuberisation was obtained in vitro on yam (Dioscorea cayenensis-D.rotundata complex). The effect of exogenous polyamines on tuber formation and development (length and weight of microtubers) were investigated and discussed in relation with changes in endogenous polyamines. Application of exogenous polyamines, inhibitors of their metabolism and polyamines precursors in various concentrations positively affected microtuber formation by yam nodal cuttings and their further development. In control conditions, three weeks are needed to obtain 100% of tuberisation. With low concentrations of putrescine (10 5 or 10 6 M), tuber formation occurred earlier. Polyamine endogenous level and metabolism can be significantly affected by exogenous polyamines but modifications of endogenous free polyamines could not be directly correlated to the tuber formation process. Increases in endogenous putrescine and auxins were observed in tubers showing a better development in the presence of putrescine. These results can be used for optimising in vitro conditions for mass production of larger microtubers of the Dioscorea cayenensis-D. rotundata complex