Inheritance and genetic diversity of some enzymes in the sexual and diploid pool of the agamic complex of Maximae (Panicum maximum Jacq., P. infestum Anders. and P. trichocladum K. Schum.)

La tribu des #Maximae (#Panicum maximum Jacq., #P. infestum Anders., #P. trichocladum K. Shum. ) comprend deux pools sympatriques avec différents modes de reproduction et de niveaux de ploidie : un pool tétraploïde et apomictique d'une part, et un pool plus petit, pool diploïde et sexué d'autre part. Chez ce dernier, la sexualité autorise ces croisements et rend ainsi possible la mise en évidence de la structure (monomérique ou dimérique) de 9 systèmes enzymatiques et de leur déterminisme génétique (16 loci). Des distorsions de ségrégation ont été observées dans les systèmes malate déshydrogenase et estérase. La diversité du pool diploïde est importante en accord avec son mode de reproduction (allogamie et anémophile). Cette diversité est divisée en 3 groupes correspondant à l'origine géographique des populations. Cette organisation est très proche de celle observée à partir de caractères morphologiques. (Résumé d'auteur

Effect of Ethephon Stimulation on Downward Tapping in Latex Production Metabolism on Upward Tapping in PB 217 Clone of Hevea Brasiliensis

In Hevea brasiliensis, Ethephon is used as an exogenous stimulant of latex production. In downward tapping, it has been shown that its misuse has negative consequences on the metabolism of the latex cells of the tree. However, little is known about the impact of this downward tapping practice on latex-producing metabolism in upward tapping. The aim of this study was to determine the effect of stimulation in downward tapping on the latex-producing metabolism in clones PB 217, when the trees are subsequently tapped up. Study was carried out by monitoring the evolution of biochemical parameters of latex and rubber production. From this study, it was found during the last two years of downward tapping that in PB 217 clone, the optimal metabolism of latex production was obtained with 13 Ethephon stimulations per year. When subsequent tapping is done upward, the stimulation frequencies of the trees greater than 4 times per year in downward tapping have a negative impact on the latex-producing metabolism in PB 217 clone of Hevea brasiliensis. However, in cumulative production over the 10 years of downward tapping added to the 2 years of upward tapping, it is the frequency of 13 stimulations per year in downward tapping which is the highest

Influence of plant growth regulators on somatic embryogenesis induction from inner teguments of rubber (Hevea brasiliensis) seeds

Generating somatic embryos from the inner teguments of hevea seeds is difficult. Like other ligneous plants, the rubber-tree is generally considered to be recalcitrant with regard to somatic embryogenesis. In this study, the ability of callus from inner integument explants to develop embryogenic callus lines was highlighted. Combination of 2,4-dichlorophenoxyacetic acid (2,4-D/KT) (9 μM/3.375 μM) revealed the positive effect of the 2,4-D on callogenesis and somatic embryogenesis from the inner integument of the seed of immature fruit. The rate of embryogenic calli of about 50% obtained, suggested that 2,4-D has a similar effect as 3,4-dichlorophenoxy acetic acid (3,4-D). So, although 2,4-D is rarely used as a hormone in biotechnology of rubber, its positive influence on callus induction and somatic embryo development shows that it is an alternative to 3,4-D which is commonly used. Optimal combinations of 2,4-D/thidiazuron (TDZ) (9 μM/34.2 nM) produced abnormal embryos at lower rates (approximately 5%) than the optimal combination of 2,4-D/KT.Keywords: Callus, culture medium, Hevea brasiliensis, hormones, rubber-tree, somatic embryogenesisAfrican Journal of Biotechnology Vol. 12(16), pp. 1972-197

Callogenesis and Somatic embryogenesis induction in Hevea brasiliensis: effects of fruit shelf-life and carbon source

An experiment was conducted to study the effect of the fruit shelf-life and the concentrations of carbon source on somatic embryogenesis via callogenesis of Hevea brasiliensis. Fruits harvested were stored at 15°C during 1, 5, 7, 12 and 15 days and the inner integuments obtained from seed were used as explants. The experiments were performed under carbon source treatments with three concentrations for glucose and five concentrations for sucrose. Under these conditions, the percentage of  explants forming calli was better during the first week of fruit  preservation regardless of the carbon source but at high concentration. However, beyond 7 days of fruits shelf-life, sucrose is best to induce callus unlike glucose but with high concentration. The best rate of embryogenic calli was also obtained with sucrose. The percentages of callogenic explants and embryogenic calli have decreased sharply with the shelf-life of fruit at 15°C. So, to maintain an embryogenic potential of explants in situations of long-term conservation of fruits, sucrose can be used at 234 mM of concentration or default at 111 mM sucrose. These sucrose concentrations are conducive to induce embryogenic calli with  explants coming to rubber fruits after a long time of preservation

Clef D’identification Morphologique De Cinq Clones D’hevea (Hevea Brasiliensis Muell. Arg.) Recommandes En Cote d’Ivoire

La présente étude vise à déterminer un nombre réduit de critères morphologiques pour la différenciation des cinq clones (GT 1, PB 217, IRCA 41, 230 et IRCA 331) recommandés en Côte d’Ivoire. L’objectif général est d’éviter les mélanges clonaux observés dans les Jardins à bois de greffes (JBG) d’hévéa, servant au greffage du matériel de plantation utilisé par des planteurs. Ainsi, ces clones ont été décrits dans deux JBG à l’aide de 27 critères morphologiques utilisés dans le monde. Pour chacun des clones, la description a porté sur 25 plants sains de trois ou quatre étages foliaires dont la conformité clonale a été confirmée à l’aide des marqueurs moléculaires microsatellites. Les résultats ont montré que six critères permettent de discriminer clairement ces cinq clones : couleur des feuilles, coupe transversale de la foliole centrale, forme de l’avant dernier étage foliaire, glandes nectarifères, longueur et l’orientation du pétiolule central. Le clone GT 1 s’identifie par la couleur vertfoncé des feuilles et d’un long pétiolule (> 1,4 cm), le clone PB 217 par des feuilles vert-clair avec de court pétiolule (≤ 0,9 cm), le clone IRCA 331 par un étage foliaire conique, des pétiolules droits et des folioles centrales plates. Les clones IRCA 230 et IRCA 41 se distinguent l’un de l’autre par les glandes nectarifères abondantes et peu abondantes, respectivement. Cette investigation doit être menée dans d'autres localités dans le but de tester la stabilité de ces six critères dans l'espace et le temps. This paper focuses on determining a reduced number of morphological criteria for the differentiation of the five clones (GT 1, PB 217, IRCA 41, 230 and IRCA 331) recommended in Côte d'Ivoire. The general objective is to avoid the clonal mixtures observed in the graft wood garden (GWG) of rubber, which is used to graft planting material used by planters. These clones have been described in two GWG using 27 morphological criteria around the world. For each clone, the description looked at 25 healthy plants of three or four shape of the leaf floors clonal compliance. This was confirmed using microsatellite molecular markers. The results showed that six criteria made it possible to clearly differentiate these five clones: colour of the leaves, the cross-section of the central leaflet, the shape of the leaf floors, the nectariferous glands, the length and orientation of the central petolule. The GT 1 clone is identified by the dark green colour of the leaves and a long petiolule ( 1,4 cm), the PB 217 clone by light green leaves with short petiolule (0.9 cm), and the IRCA 331 clone by a conical shape of the leaf floors, straight petiolules, and flat central leaflets. The IRCA 230 and IRCA 41 clones are distinguished by the abundant and infrequent nectariferous glands, respectively. This investigation should be carried out in other localities with the aim of testing the stability of these six criteria in space and time