Effet de l’implantation des souches de Panicum maximum var. C1 sur l’invasion de Hyptis suaveolens (L.) Poit dans les pâturages naturels au Nord-Béni

La productivité et la durabilité des pâturages naturels sont menacées au Nord-Bénin par la prolifération de Hyptis suaveolens. La restauration de ces pâturages nécessite des mesures de lutte contre cette plante. L’étude visait à évaluer l’effet de Panicum maximum C1 installé avec des souches à une densité de 4 plants/m2 sur H. suaveolens et à comparer les réactions face à H. suaveolens des souches de P. maximum issues d’un milieu infesté ou non par H. suaveolens. Le contrôle d’invasion de H. suaveolens par la culture de P. maximum a été évalué par la contribution spécifique de contact (CSC), le biovolume (Bv) et la biomasse (Bm) de H. suaveolens. Lesrésultats ont montré que la présence de P. maximum C1 a réduit significativement (p<0,05) la CSC, le Bv et la Bm de H. suaveolens respectivement à 13,20%, 0,16% et 15,62% après trois mois de culture sans exploitation. La provenance des souches n’a eu d’effet significatif (p>0,05) sur aucun des paramètres biophysiques de H. suaveolens, ni sur le développement de P. maximum C1 en présence de H. suaveolens. Ainsi, la culture de P. maximum dans les pâturages envahis a permis d’améliorer leurs caractéristiques pastorales et peut être promue en milieu paysan.Mots clé : Hyptis suaveolens, Panicum maximum C1, plante envahissante, pâturages, Bénin. Effect of Panicum maximum var. C1 stumps cultivation on invasion of Hyptis suaveolens (L.) Poit in natural pastures in northern Benin   The productivity and sustainability of natural pastures in northern Benin are threatened by the proliferation of Hyptis suaveolens. The restoration of these pastures requires control measures against this plant. This study aimed at evaluating the effect of Panicum maximum C1 installed with stumps at a density of 4 plants/m² on the development of H. suaveolens and to compare the reactions with respect to H. suaveolens of P. maximum’s stumps from an infested environment or not by H. suaveolens. Invasion control of H. suaveolens by culture of P.  maximum was assessed using the specific contact contribution (SCC), biovolume (Bv) and biomass (Bm) of H. suaveolens. The results showed that the presence of P. maximum C1 reduced significantly (p <0.05) the SCC, Bv and Bm of H. suaveolens respectively to 13.20%, 0.16% and 15.62% after three months of cultivation without exploitation. The origin of stumps had no significant effect (p> 0.05) on any of the biophysical parameters of H. suaveolens, nor on the development of P. maximum C1 in the presence of H. suaveolens. Thus, the cultivation of P. maximum in pastures invaded has improved their pastoral characteristics and can be promoted in rural areas. Keywords: Hyptis suaveolens, Panicum maximum C1, invasive plant, pastures, Benin

Chromosome evolution in Neotropical butterflies

Peer reviewe

Chromosomal evolution in the South American Riodinidae (Lepidoptera: Papilionoidea)

Peer reviewe

Horizontally acquired glycosyltransferase operons drive salmonellae lipopolysaccharide diversity.

The immunodominant lipopolysaccharide is a key antigenic factor for Gram-negative pathogens such as salmonellae where it plays key roles in host adaptation, virulence, immune evasion, and persistence. Variation in the lipopolysaccharide is also the major differentiating factor that is used to classify Salmonella into over 2600 serovars as part of the Kaufmann-White scheme. While lipopolysaccharide diversity is generally associated with sequence variation in the lipopolysaccharide biosynthesis operon, extraneous genetic factors such as those encoded by the glucosyltransferase (gtr) operons provide further structural heterogeneity by adding additional sugars onto the O-antigen component of the lipopolysaccharide. Here we identify and examine the O-antigen modifying glucosyltransferase genes from the genomes of Salmonella enterica and Salmonella bongori serovars. We show that Salmonella generally carries between 1 and 4 gtr operons that we have classified into 10 families on the basis of gtrC sequence with apparent O-antigen modification detected for five of these families. The gtr operons localize to bacteriophage-associated genomic regions and exhibit a dynamic evolutionary history driven by recombination and gene shuffling events leading to new gene combinations. Furthermore, evidence of Dam- and OxyR-dependent phase variation of gtr gene expression was identified within eight gtr families. Thus, as O-antigen modification generates significant intra- and inter-strain phenotypic diversity, gtr-mediated modification is fundamental in assessing Salmonella strain variability. This will inform appropriate vaccine and diagnostic approaches, in addition to contributing to our understanding of host-pathogen interactions

The Butterfly Fauna Of The Italian Maritime Alps:Results Of The «Edit» Project

Bonelli, Simona, Barbero, Francesca, Casacci, Luca Pietro, Cerrato, Cristiana, Balletto, Emilio (2015): The butterfly fauna of the Italian Maritime Alps: results of the EDIT project. Zoosystema 37 (1): 139-167, DOI: 10.5252/z2015n1a6, URL: http://dx.doi.org/10.5252/z2015n1a