Research topic

Cocoa and Sweet Potato Agronomy

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Research papers

2011 · Nature · 1,307 citations

The Medicago genome provides insight into the evolution of rhizobial symbioses

Sequencing of Medicago truncatula, a model organism of legume biology, shows that genome duplications had a role in the evolution of endosymbiotic nitrogen fixation. Legumes are unusual among plants in that they can carry out endosymbiotic nitrogen fixation with rhizobial bacteria. The genome of Medicago truncatula (also known as barrel medic or barrel clover), a well-established model for the study of legume biology, has now been sequenced. Genome analysis shows that M. truncatula has undergone several rounds of whole-genome duplication, and that the duplication that took place approximately 58 million years ago played an important part in the evolution of endosymbiotic nitrogen fixation. Legumes (Fabaceae or Leguminosae) are unique among cultivated plants for their ability to carry out endosymbiotic nitrogen fixation with rhizobial bacteria, a process that takes place in a specialized structure known as the nodule. Legumes belong to one of the two main groups of eurosids, the Fabidae, which includes most species capable of endosymbiotic nitrogen fixation1. Legumes comprise several evolutionary lineages derived from a common ancestor 60 million years ago (Myr ago). Papilionoids are the largest clade, dating nearly to the origin of legumes and containing most cultivated species2. Medicago truncatula is a long-established model for the study of legume biology. Here we describe the draft sequence of the M. truncatula euchromatin based on a recently completed BAC assembly supplemented with Illumina shotgun sequence, together capturing ∼94% of all M. truncatula genes. A whole-genome duplication (WGD) approximately 58 Myr ago had a major role in shaping the M. truncatula genome and thereby contributed to the evolution of endosymbiotic nitrogen fixation. Subsequent to the WGD, the M. truncatula genome experienced higher levels of rearrangement than two other sequenced legumes, Glycine max and Lotus japonicus. M. truncatula is a close relative of alfalfa (Medicago sativa), a widely cultivated crop with limited genomics tools and complex autotetraploid genetics. As such, the M. truncatula genome sequence provides significant opportunities to expand alfalfa’s genomic toolbox.

2002 · Forests Trees and Livelihoods · 25 citations

TOWARDS THE IMPROVEMENT OF SAFOU (<i>DACRYODES EDULIS</i>): POPULATION VARIATION AND REPRODUCTIVE BIOLOGY

In the last two decades, growing interest in the production and utilisation of safou (Dacryodes edulis), an indigenous fruit tree species of West and Central Africa, has stimulated work on the selection of genetic resources with desired traits, timing of fruit collection and the tree's reproductive biology. In this context, 58 germplasm accessions were collected in Nigeria during 1998. The periodicity of fruiting was found to vary geographically and a preliminary characterisation showed a wide range of variation in fruit traits. About 4% of fruits were seedless. The importance of this knowledge is discussed with regard to genetic selection and improvement, and the need to extend germplasm collection activities to wild relatives of the species. In the humid forest zone, the main insect pollinator is Meliponula erythra. Allogamy has been found to be the main reproduction system of D. edulis, while hermaphrodite flowers are self-compatible.

1977 · Bulletin of Entomological Research · 20 citations

Studies on the biology of <i>Acanthomia tomentosicollis</i> (Stål) (Hemiptera: Coreidae) in the field and insectary

Abstract Studies on the biology of Acanthomia tomentosicollis (Stål) at Ibadan, Nigeria, showed that the periods of development in the field and the insectary averaged 17 and 18 days, respectively. The hemispherical, hexagonally sculptured eggs were laid in batches of 2.99 (mean=7 eggs per batch in the insectary and 20 in the field). Preoviposition periods were 11–22 days in unmated and 6–9 days in mated females. The mean number of eggs deposited by mated females (202) was significantly higher than that deposited by unmated females (135), although the average oviposition period of 16 weeks in unmated females was three weeks longer than in mated females. Unmated males and females were longer-lived than their mated counterparts, and females generally lived longer than males. These results and other observations on 'the biology of A. tomentosicollis are discussed in the context of its seasonal biology and the pattern of infestation of pigeon pea ( Cajanus cajari ), its main host plant.