Effect of Herbicides Used in Horticulture (2,4-D, Glyphosate and Nicosulfuron) on Snails <i>Achatina fulica</i>(Bowdich, 1720)

2,4-Dichlorophenoxyacetic (2,4-D), glyphosate, and nicosulfuron, because of their modes of action and selectivity, are the most widely used herbicides in Ivorian horticulture. Fuels toxicity was the reason of many debates in the world because of their massive and uncontrolled use. They are frequently blamed for the reduction of soil fertility and terrestrial biodiversity observed in agricultural areas. In view of the debates raised by their toxicities, the use of these herbicides requires the greatest caution and clear information on the real risk incurred by the edaphic fauna by conducting ecotoxicity studies. The present study aims to evaluate the effect of 2,4-D, glyphosate and nicosulfuron herbicides on the growth and reproduction of Achatina fulica snails in microcosm. To do this, we treated each plot on which snail microcosms were placed with 2,4-D, glyphosate or nicosulfuron herbicides according to the manufacturer’s recommendations. The results showed for all the herbicides used, that after 28 days of exposure, the growth of juvenile snails was slowed down. The number of eggs laid per pair was reduced in adult snails. The egg hatchability test revealed a reduction in egg hatchability. In addition, each effect was dependent on the herbicide used. Thus, toxicity was found to be greater according to the following order: nicosulfuron ? glyphosate ? 2,4-D. From the results obtained, we concluded that 2,4-D, glyphosate, and nicosulfuron treatments under field conditions are a potential threat to the sustainability of snail species and therefore to soil life. The intensity of the effect depends on the toxicity of the herbicides used.

Genetic Diversity of Taro Landraces from Côte d’Ivoire Based on Qualitative Traits of Leaves

Taro is an important crop species in Côte d’Ivoire. It is cultivated for its tubers and leaves. But its knowledge and genetic diversity and differentiation are very weakly documented. Several morphological types are found in rural area, but their identification is not very clear, and their agronomic potentiality is underexploited. In this context we initiated a survey and collected 213 accessions from 14 growing regions of Côte d’Ivoire. The diversity was evaluated based on seven qualitative traits of leaves (Shape of the base of the leaf, Predominant position (shape) of the leaf blade surface, Margin of the leaf blade, Leaf blade variegation, Profile of the petiolar junction, Shape of the leaf sheath, Shape of the appendix) during an experimentation conducted in rural area. The objective of this study was to characterize the collection of taros collected in different geographical zones of Côte d’Ivoire and identify the genera cultivated. Results of our study indicated that excepted margin of the leaf blade all traits are very discriminant. Several variants were observed for each of traits. According to observations and statistics analysis accessions were separated into two main groups. The characteristics of these groups indicate that taro cultivated in Côte d’Ivoire could belong to two genera: Xanthosoma and Colocasia.

热带草原棕榈树的空间格局及其时间变异性

物种的空间分布和关联可以提供林分的基本信息及动态。然而,由于树木的空间分布和关联依赖于不同尺度下的环境因子,要弄清环境异质性和植物间相互作用的影响,需要选择合适的空间模型进行分析。本研究分析了同一热带草原棕榈树的种群空间分布,并假设这些分布在20年内发生了变化。为了消除大规模环境异质性的影响,采用异质性泊松零模型下的非均质L-函数。研究结果发现:(ⅰ)与20年前不同,稀树草原地区的成年树种呈规则分布而非聚集分布:(ⅱ)虽然幼苗和幼树的空间分布总是呈聚集状,但聚集区域面积(强度)在减少:(ⅲ)除幼树期,其它阶段均与富养斑块无关联,这也与20年前不同;(ⅳ)没有两个研究地点在结构上有特别的差异,只是雌性棕榈树在空间上与保护区的整叶幼苗有关联,而在乡村,它们在空间上是相互独立的。我们的研究证明,空间分布发生了部分变化,同时对空间异质性的管理也更加完善,模拟结果也更精确。