Interactions between a Root Knot Nematode (<i>Meloidogyne exigua</i>) and Arbuscular Mycorrhizae in Coffee Plant Development (<i>Coffea arabica</i>)

This paper focuses on parasitic root knot nematodes (Meloidogyne exigua) and how to decrease their pathogenic effect on coffee plants (Coffea arabica), by examining the behaviour of and the interactions between nematodes, coffee plant and arbuscular mycorrhizae (AM). The experiment was carried out at the seedling stage, with six (6) treatments (plants with M. exigua, plants with arbuscular mycorrhizae, plants with both organisms, and the same time, first mycorrhizae plants, then nematodes were inoculated and vice versa). After 5 months the measured variables were: dry biomass (roots and shoot), nematode knots caused by M. exigua in root, nematode juvenile (J2) found in 100.0 g of soil, and mycorrhizal percentage. Plant nutrients (P and N) contents were analysed. Significant differences were found in all the variables, but concentration N content in plants. Plants with mycorrhizae and plants with mycorrhizae and then inoculated with nematodes have the same behaviour. Control plants and plants with nematode and then inoculated with mycorrhizae behave similarly. It is thought that arbuscular mycorrhizae are formed before the nematode infestation, allowing coffee plants to regain the energy lost by the parasitic interaction. AM may help coffee plants with lignifications of the plant cell wall cuticle. As the cuticle thickens it is more difficult for nematodes to penetrate and enter into plant roots. Therefore, arbuscular mycorrhizae help coffee plants to uptake and transport nutrients, improving its nutritional status and stabilizing nematode attacks. It is suggested that symbiotic interactions help neutralize parasitic interactions.

<i>Trypanosoma evansi</i>: A Qualitative and Quantitative Ultrastructural Analysis of the Spleen during Experimental Murine Infections

A murine model is used to study qualitatively and quantitatively the splenic ultrastructural changes induced by two Trypanosoma evansi strains derived from naturally infected local equine hosts (Equusasinus and E. caballus);T. evansi causes ultrastructural modifications in the spleen of the infected mice. The modifications include tissular disorganization, fibrosis, mitochondrial swelling, apoptosis and necrosis. The initial phases of the infection are quite similar, whereas the final phases differ qualitatively depending on the strain’s source. The ultrastructural quantitative changes were studied in the reticular splenocytes covering alterations in the area of the cytoplasm and nucleus. Analysis of the results shows the induction of various splenic alterations caused by local T. evansi strains. Also, it was documented that discriminative time modulation, as well as progressive tissular, cellular and subcellular changes, are more associated with derived infections from E. caballus strain.