No abstract

Jatropha curcas L. has been promoted as a “miracle” tree in many parts of the world, but recent studies have indicated very low levels of genetic diversity in various landraces. In this study, the genetic diversity of landrace collections of J. curcas was compared with the genetic diversity of the species from its native range, and the mating system was analyzed on the basis of microsatellite markers. The genetic diversity parameters were estimated, and analysis of molecular variance, principal coordinate analysis, and unrooted neighbor‐joining tree were used to describe the relationship among populations. Results confirmed very low genetic diversity in African and Asian landraces. Mexican populations from the regions of Veracruz, Puebla, and Morelos were also found to have low levels of diversity (mostly monomorphic), while populations from Chiapas were polymorphic with an expected heterozygosity between 0.34 and 0.54. Bayesian analysis showed differentiation according to geographic locations, which was confirmed by principal coordinate analysis and neighbor‐joining tree. Estimations of outcrossing rate of individual families from Chiapas showed that some mother trees were mainly outcrossing. Mating system could not be estimated in the landraces from Mali and populations from Veracruz, Puebla, and Morelos (Mexico), as these were highly monomorphic. The observed low level of genetic diversity in some of the populations and landraces suggests that breeding programs should test for genetic variation and heritability in relevant quantitative traits and estimate if sufficient gain can be expected from traditional testing and selection. Diversification of the local gene pools may be considered for breeding and selection.

Pot experiments were conducted in a nursery in 2008 in Mali to study the effect of mycorrhizal symbionts on the growth and root infection of Ziziphus mauritiana and Tamarindus indica seedlings in unsterile soils. Three treatments were used and consisted of two types of inoculum (Glomus aggregatum, G. fasciculatum) and an uninoculated control. The seedlings were non-destructively assessed each month, and an additional, destructive harvest was made, after 6 and 10 months for Z. mauritiana and T. indica respectively. Mycorrhizal inoculation had a more positive impact on the growth of Z. mauritiana than on T. indica. G. aggregatum significantly (P \ 0.01) improved the growth of Z. mauritiana seedlings. However, the growth of T. indica seedlings was significantly better in the control compared to the two types of inoculum used. This indicates that unsterile nursery soil may contain effective mycorrhizal propagules. The mean percentage of infection of Z. mauritiana seedlings (74%) was significantly higher than that of T. indica (57%). We conclude that mycorrhizal inoculation can improve both mycorrhizal infection and growth of Z. mauritiana seedlings in unsterile nursery soils.

In sub-Saharan Africa, Sorghum (Sorghum bicolor) is an important cereal for both human being and animals. Unfortunately, its production is confronted to soils with deficiency of phosphorus. Traditional use of mineral phosphate on this culture fertilization is expensive and may cause contamination. It is thus necessary to seek more efficient and economic reasonable techniques to improve sorghum growth. Arbuscular mycorrhizal fungi (AMF) constitute a reference for phosphorus improvement and plant nutrition. This study aimed to investigate the effects of AMF strains (Rhizophagus irregulare, Glomus aggregatum, G. mosseae) on growth of sorghum cultivated in greenhouse on Sangalkam soil (Senegal) sterilized with or without Tilemsi natural phosphate (PNT). The phosphorus can represent until 0.2% of the dry weight of the plant. Two fertilizers were used separately and together to doses of 20 g by strain, 100 mg and 200 mg of PNT. The experiment lasted for 120 d. Results showed that mycorrhizal colonization intensity varied between 40% and 80% for all treatments. AMF inoculation increased sorghum plant height and biomass, regardless of PNT amendment. The inoculation permits to bring strain of AMF that intervene efficiently in the transportation and the availability of phosphorus for the plant.

The market gardening sector is confronted with numerous constraints which weaken and hinder its development. Among these constraints is the importance of plant-parasitic nematodes. For the sustainable management of these worms, a diagnostic evaluation was carried out in two permanent market gardening of Sébéninkoro (Kati) and Koulikoro town in order to determine their diversity. 54 soil samples of 500 g were taken from 3 plots, ie 27 samples per site. Analysis of these samples revealed the presence of 8 genera of nematodes. Among these nematodes, there are nematodes of the genus Meloidogyne very harmful to crops and Tylenchorhynchus. They are common and abundant throughout both sites.