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See detailTuber formation and growth of Dioscorea cayenensis-D. rotundata complex. Interactions between exogenous and endogenous jasmonic acid and polyamines
Ondo Ovono, Paul ULg; Kevers, Claire ULg; Dommes, Jacques ULg

in Plant Growth Regulation (2010)

Tubers can be initiated and developed in vitro from nodal cuttings of yam (Dioscorea cayenensis - D. rotundata complex). The effect of exogenous jasmonic acid, alone or in combination with putrescine, on ... [more ▼]

Tubers can be initiated and developed in vitro from nodal cuttings of yam (Dioscorea cayenensis - D. rotundata complex). The effect of exogenous jasmonic acid, alone or in combination with putrescine, on these processes was investigated in relationship to endogenous jasmonic acid and polyamine levels. Application of exogenous jasmonic acid at various concentrations positively affected microtuber formation and growth from yam nodal cuttings. In control conditions, three weeks were needed to obtain 100% of tuberisation. Jasmonic acid at low level (0.1 µM) accelerated tuber formation (46% after one week) as did putrescine (10 µM). But endogenous levels of jasmonic acid were not significantly affected by its exogenous presence in the medium. Jasmonic acid also interacted with other growth regulators as polyamines, but the decrease in time necessary to observe tuber formation could not be correlated with endogenous modifications of PUT content. The presence of jasmonic acid (0.1 to 1 µM) as PUT (1 µM) induced also an increase of tuber length and weight. The combination of jasmonic acid (0.1 µM) and putrescine (1 µM) had no positive effect on tuber formation (precocity) but had an additive effect on further growth (length and weight). In the future, these results could help the optimising in vitro conditions for mass production of larger yam microtubers. [less ▲]

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See detailIn Vitro Preservation of Yam ( Dioscorea cayenensis-D.rotundata complex) for a Better Use of Genetic Resources
Ondo Ovono, Paul ULg; Kevers, Claire ULg; Dommes, Jacques ULg

in Notulae Botanicae Horti Agrobotanici Cluj-Napoca (2010), 38

Among the food crops, yam takes up quantitatively the first place in the gabonese diet. Unfortunately, it can stay available only 6 to 7 months in the year because of difficulties of harvest and post ... [more ▼]

Among the food crops, yam takes up quantitatively the first place in the gabonese diet. Unfortunately, it can stay available only 6 to 7 months in the year because of difficulties of harvest and post- harvest. This problem is little studied in the case of Dioscorea cayenensis-D. rotundata complex. In order to optimize the use of micro tubers for the growing in green house or field, it is important to control the duration of storage before the germination. The present study concerns microtubers obtained by in vitro culture. When microtubers were harvested (after 9 months of culture) and directly transferred on a new medium without hormone, the tubers rapidly sprouted in in vitro conditions. Harvested microtubers were also stored dry in jars in sterile conditions during 2 to 18 weeks before in vitro sprouting. In this case, microtubers stored during 18 weeks sprouted more rapidly than those stored 8 weeks. The size of the tubers used for the storage had great influence on further sprouting. The upper microtubers in 25 mm can be kept to the darkness, under 50% of relative humidity, in 25°C during at least 18 weeks. Sprouting is 100% whatever the substrate of culture. The plant tissue culture technique constitutes a serious alternative for the preservation of plant kinds and for the production of planting material. These techniques allow multiplying in a short time of thousands of copies of new varieties of newly created plants. These in vitro plants can be used on one hand, for the production planting material, and on the other hand for ex vitro storage of breeding grounds with decelerated growth, to struggle against genetic erosion. These results should allow improving in practice the multiplication of yam, while guaranteeing phytosanitary qualities. [less ▲]

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See detailTuber formation and development of Dioscorea cayenensis-D. rotundata complex in vitro. Effect of polyamines.
Ondo Ovono, Paul ULg; Kevers, Claire ULg; Dommes, Jacques ULg

in In Vitro Cellular & Developmental Biology-Plant (2009)

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 ... [more ▼]

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. [less ▲]

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See detailEffects of reducing sugar concentration on in vitro tuber formation and sprouting in yam (Dioscorea cayenensis-D. rotundata complex).
Ondo Ovono, Paul ULg; Kevers, Claire ULg; Dommes, Jacques ULg

in Plant Cell, Tissue & Organ Culture (2009), 99(1), 55-59

The effects of reducing sucrose level on tuber formation (% of cultures with microtubers), development (length and fresh weight of microtubers) and sprouting in yam Dioscorea cayenensis-D. rotundata ... [more ▼]

The effects of reducing sucrose level on tuber formation (% of cultures with microtubers), development (length and fresh weight of microtubers) and sprouting in yam Dioscorea cayenensis-D. rotundata complex in vitro were investigated. Only 29% of the explants showed tuber formation after 3 weeks in the presence of 1% sucrose in contrast to 100% with 3%. After 120 days of culture, the length and the weight of the tubers obtained in the presence of 1% sucrose were less than with 3% sucrose. Addition of sorbitol to keep osmolarity at the same level did not restore normal rate of tuber formation. Similar results were obtained with the use of reduced fructose or glucose level. Microtuber sprouting was also affected by sucrose level incorporated into the tuberisation medium. Tubers obtained on reduced sucrose level sprouted later and the increase of osmolarity with sorbitol did not restore normal sprouting. The bigger tubers obtained on high sucrose media could contain more carbohydrate reserves that could partially explain a higher sprouting rate. These results can be used for optimising in vitro conditions for mass production of microtubers in yam and especially in Dioscorea cayenensis-D. rotundata complex, a very important species in West Africa. They specially showed the importance of tuberisation conditions on precocity of tuberisation, on tuber length and weight and on their further sprouting. [less ▲]

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