Incidence and distribution of cassava mosaic begomoviruses in Cote d'Ivoire

Cassava mosaic disease (CMD) caused by the whitefly-transmitted begomoviruses (family Geminiviridae) is amajor threat to production of cassava (Manihot esculenta Crantz) in Côte d’Ivoire. A survey was conducted in themajor production zones in Côte d’Ivoire to assess the incidence, severity, and distribution of cassava viraldiseases. At each survey site, up to ten plants were assessed for symptom severity; incidence and samples weretaken for virus testing. Techniques based on polymerase chain reaction (PCR) were used for the detection ofcassava mosaic begomoviruses (CMBs) in the sampled leaves. Incidence of CMD varied from 0 to 100% andsymptom severity from 1 to 5. Incidence differed significantly between the various agro-ecological zones(P<0.001), but severity was the same in those zones. Out of the 335 samples tested, African cassava mosaic virus(ACMV) was detected in 43.3%, East African cassava mosaic Cameroon virus (EACMCV) in 5.7%, and bothACMV and EACMCV in 31.3%; 19.7% of the samples analyzed were negative to all the viruses tested. None of thesamples was tested positive to the East African cassava mosaic virus-Uganda (EACMV-Ug). These resultssuggest high incidence of CMD in the cassava production zones in Côte d’lvoire and underscores a need forimplementation of control measures including phytosanitary measures with utilization of CMD-free materials forplanting and adoption of resistant varieties

Distribution, incidence and severity of viral diseases of yam (Dioscorea spp.) in Cote dIvoire

A survey was conducted in major yam cultivation zones in Côte d’Ivoire in 2009 to determine the incidence, severity of viral diseases, and viruses associated with the infected plants. Incidence and severity of the viral diseases were estimated based on symptoms. Enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR)-based techniques were used for the detection of Yam mosaic virus (YMV), Cucumber mosaic virus (CMV), Dioscorea mottle virus (DMoV) and yam badnaviruses in the sampled yam leaves. Disease incidence varied from 0 to 90% and symptom severity from 1 to 5. There were significant difference in incidence and severity between different agro-ecological zones (P < 0.001). About 36% of the samples tested positive to YMV, ca. 1.5% tested positive to CMV, ca. 39.1% samples tested positive to yam infecting badnaviruses, and none of the samples tested positive to DMoV. This study demonstrated high incidence of virus diseases in all the yam production regions and warrants implementation of virus disease control measures

Effect of wall thickness and node diaphragms on the buckling behavior of bamboo culm

The buckling behavior of bamboo culm is highly affected by internodal properties, i.e. material properties and geometric parameters of the trunk. In this study, the effects of Phyllostachys Edulis bamboo culms have on buckling phenomena under bending and compressive loads are investigated. Internodal walls are assumed to be composed of orthotropic functionally graded-type materials which are controlled by the volume fraction of the vascular fiber bundle. Provided that the trunk wall thickness near the node is greater than that in the internode and that the number of fibers is mostly unchanged, the internode and node walls are defined by shell elements with the same composite layup material but different thicknesses. It is found that, with a constant internodal length the buckling behavior transitions from global to local as the tube radius increases. The global buckling load increases with approximately a fourth order polynomial in relation with the radius while the local buckling load linearly increases with the tube radius. Nodal wall thickening enhances the buckling load in both the global and local domains. There is an interactive contribution of nodal wall and diaphragm thicknesses on the buckling behavior up to a certain point where the local buckling load is independently determined by each internodal structure. The buckle can occur within thin diaphragms, which results in much lower buckling load compared with the tube without/removed the diaphragms