This study was conducted over a period of 20 years, to assess the problems involved in developing subcultures over a very long period, of oil palm (Elaeis guineensis Jacq.) somatic embryos which were maintained in vitro on a Murashige and Skoog mineral-based culture medium, without growth regulators. Analysis of the proliferation rate of the embryogenic cultures, along with the survivability of the regenerated plantlets after their transfer into soil and of the flowering of the derived adult palms has been conducted for cultures maintained in vitro during 1 to 20 years. From the ninth year of maintenance, the tissue quality of the somatic embryos gradually began to decline. However, after more than 20 years, 30% of the 20 clones tested still continued to proliferate satisfactorily on the same maintenance medium, keeping their multiplication potential intact. Even though a depressive effect of the age of the lines has been observed on the survival capacity of plants under natural conditions, it is noteworthy that among the clones originating from 20-year-old cultures only eight of them (40%) have exhibited the "mantled" floral abnormality. Different hypotheses concerning the origin of the disruptions observed on the in vitro cultures, plantlets and adult palms that occur over a very long period of in vitro conservation are discussed.
RésuméLes présents travaux visent à proposer des voies d'optimisation du rendement de la production de semences par fécondation contrôlée chez le cocotier. Les variétés de cocotier Grand de Comores (GCO) et Nain Jaune de Malaisie (NJM) ont été utilisés à cet effet. Le pollen produit à partir de l'inflorescence est conditionné sous vide et conservé au congélateur à -15°C pendant 4 mois. Chaque mois, la qualité du pollen est évaluée. Il ressort que GCO fournit par inflorescence 8,6 g de pollen et NJM, 5,7 g. Pendant la conservation les taux de nouaison diminuent en général de 20,5 à 1,1 % après 4 mois. Les teneurs en protéines et en sucres non réducteurs diminuent respectivement de 30 à 7,1 % et de 7,9 à 2,3 % alors que celles des sucres réducteurs augmentent de 0,7 à 1,1 %. La qualité du pollen conservé au delà de 1 mois est donc altérée et affecte le rendement de la production de semences.
Mots clés:Cocotier, fécondation contrôlée, qualité du pollen, conservation. CMT and MYD produced 8.6 g and 5.7
Abstract
Effect of the storage time on the quality of pollen in the seeds production at the coconut palm (Cocos nucifera L.). The main objective of this study is to find the ways to optimize the yield of controlled pollination in the coconut palm. Pollen from the coconut varieties Comoro Moheli Tall (CMT) and the Malayan Yellow Dwarf (MYD) stored in deepfreezer for 4 months at -15°C is studied. This study shows that
Genetic control by creation of the coconut varieties expressing both Lethal Yellowing (LY) disease resistance and good agronomic performances led breeders to select in Tall populations which contain large diversity, some peculiar palms used as genitors. Thus, 18 genotypes of Vanuatu Tall (VTT) coded from G1 to G18 were described from 30 quantitative descriptors assessed on the coconut organs that are stem, leaf, inflorescence and fruit. The results showed that these 18 VTT genotypes were divided into two agro-morphological clusters: (i) genotypes providing large nuts with heavy components and (ii) the genotypes characterized by small fruit with weak component weights. Therefore, the genotypes that belong to first cluster G1,
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