Chemical Communication between the Endophytic Fungus Paraconiothyrium Variabile and the Phytopathogen Fusarium oxysporum

Paraconiothyrium variabile, one of the specific endophytic fungi isolated from the host plant Cephalotaxus harringtonia, possesses the faculty to inhibit the growth of common phytopathogens, thus suggesting a role in its host protection. A strong antagonism between the endophyte P. variabile and Fusarium oxysporum was observed and studied using optic and electronic microscopies. A disorganization of the mycelium of F. oxysporum was thus noticed. Interestingly, the biological effect of the main secondary metabolites isolated from P. variabile against F. oxysporum did not account for this strong antagonism. However, a metabolomic approach of pure fungal strains and confrontation zones using the data analysis tool XCMS were analyzed and pointed out a competition-induced metabolite production by the endophyte in the presence of the phytopathogen. Subsequent MS/MS fragmentations permitted to identify one of the induced metabolites as 13-oxo-9,11-octadecadienoic acid and highlighted a negative modulation of the biosynthesis of beauvericin, one of the most potent mycotoxin of F. oxysporum, during the competition with the endophyte.     

Genetic Diversity and Population Structure Analyses of Wild Relatives and Cultivated Cowpea (Vigna unguiculata (L.) Walp.) from Senegal Using Simple Sequence Repeat Markers

Cowpea (Vigna unguiculata (L.)) is an important crop for food security in Senegal; therefore, understanding the genetic diversity of local germplasm is relevant for crop improvement and genetic maintenance in the era of climate change. For this purpose, 15 microsatellite markers were used to estimate the genetic diversity of Senegalese cowpea germplasm, including 671 accessions grown in eight regions and 66 wild relatives and intermediate forms (weedy). For the cultivated, the main expected heterozygosity (mHe) ranged between 0.317 (Fatick) and 0.439 (South). A narrow genetic variation between accessions from the different regions was observed with genetic similarity ranging from 0.861 to 0.965 and genetic differentiation indices (Fst) between 0.018 and 0.100. The accessions from southern Senegal (Kédougou, Sédhiou, and Kolda regions) are more diverse than the others. However, the accessions from the North (Saint-Louis) are genetically different from other regions. The diversity analysis in wild relatives from Senegal, which had never been performed before, revealed that the wild/weedy forms remain more diverse than the cultivated with genetic diversity values (He) of 0.389 and 0.480, respectively. STRUCTURE software divided the Senegalese germplasm into five subpopulations. Three of them (i, ii, and iii) included only cultivated accessions from several regions, one (v) mainly from Saint-Louis, and one (iv) the wild/weedy with some cultivated accessions. Our results support the hypothesis that Vigna unguiculata var. spontanea is the wild progenitor of cowpea. The accessions from the South, the northern recession accessions, and the wild/weedy could serve as sources of new genes for the genetic improvement of cowpea in Senegal.

     

Construction of Chromosome Segment Substitution Lines in Peanut (Arachis hypogaea L.) Using a Wild Synthetic and QTL Mapping for Plant Morphology

Chromosome segment substitution lines (CSSLs) are powerful QTL mapping populations that have been used to elucidate the molecular basis of interesting traits of wild species. Cultivated peanut is an allotetraploid with limited genetic diversity. Capturing the genetic diversity from peanut wild relatives is an important objective in many peanut breeding programs. In this study, we used a marker-assisted backcrossing strategy to produce a population of 122 CSSLs from the cross between the wild synthetic allotetraploid (A. ipaënsis×A. duranensis)^4x and the cultivated Fleur11 variety. The 122 CSSLs offered a broad coverage of the peanut genome, with target wild chromosome segments averaging 39.2 cM in length. As a demonstration of the utility of these lines, four traits were evaluated in a subset of 80 CSSLs. A total of 28 lines showed significant differences from Fleur11. The line×trait significant associations were assigned to 42 QTLs: 14 for plant growth habit, 15 for height of the main stem, 12 for plant spread and one for flower color. Among the 42 QTLs, 37 were assigned to genomic regions and three QTL positions were considered putative. One important finding arising from this QTL analysis is that peanut growth habit is a complex trait that is governed by several QTLs with different effects. The CSSL population developed in this study has proved efficient for deciphering the molecular basis of trait variations and will be useful to the peanut scientific community for future QTL mapping studies.     

Nitrogen fixation in Faidherbia albida,Acacia raddiana,Acacia senegal and Acacia seyal estimated using the 15N isotope dilution technique

A pot experiment was conducted in a greenhouse using the ¹⁵N isotope dilution method and two reference plants, Parkia biglobosa and Tamarindus indica to estimate nitrogen fixed in four Acacia species: A raddiana, A. senegal, A. seyal and Faidherbia albida (synonym Acacia albida). For the reference plants, the ¹⁵N enrichments in leaves, stems and roots were similar. With the fixing plants, leaves and stems had similar ¹⁵N enrichments; they were higher than the ¹⁵N enrichment of roots. The amounts of nitrogen fixed at 5 months after planting were similar using either reference plant. Estimates of the percentage of N derived from fixation (%Ndfa) for the above ground parts, in contrast to %Ndfa in roots, were similar to those for the whole plant. However, none of the individual plant parts estimated accurately total N fixed in the whole plant, and excluding the roots resulted in at least 30% underestimation of the amounts of N fixed. Between species, differences in N₂ fixation were observed, both for %Ndfa and total N fixed. For %Ndfa, the best were A. seyal (average, 63%) and A. raddiana (average, 62%), being at least twice the %Ndfa in A. senegal and F. albida. Because of its very high N content, A. seyal was clearly the best in total N fixed, fixing 1.62 g N plant^–1 compared to an average of 0.48 g N plant^–1 for the other Acacia species. Our results show the wide variability existing between Acacia species in terms of both %Ndfa and total N fixed: A. seyal was classified as having a high N₂ fixing potential (NFP) while the other Acacia species had a low NFP.     

Phylogenetic analyses of symbiotic genes and characterization of functional traits of Mesorhizobium spp. strains associated with the promiscuous species Acacia seyal Del.

Aims: To assess the phenotypic, symbiotic and genotypic diversity scope of Mesorhizobium spp. strains associated with Acacia seyal (Del.) isolated from different agro‐ecological zones in Senegal, and uses of susceptible microbial inoculum in a reafforestation process. Methods and Results: A polyphasic approach including phenotypic and genotypic techniques was used to study the diversity and their relationships with other biovars and species of rhizobia. The geographical origins of the strains have limited effect on their phylogenetic and phenotypic classification. Nodulation tests indicated promiscuity of the strains studied, because they were capable of nodulating six woody legume species (Acacia auriculiformis, Acacia senegal, A. seyal, Acacia tortilis ssp. raddiana, Leucaena leucocephala and Prosopis juliflora). Sequencing and phylogenetic analyses of nodA, nodC and nifH genes pointed out that in contrast to nodA gene, the phylogenies of nodC and nifH genes were not consistent with that of 16S rRNA, indicating that these genes of the A. seyal‐nodulating rhizobia might have different origins. Microbial inoculation on nonsterile soil had significant effect on the nodules number and the growth of the seedlings, indicating that these strains of rhizobia might be used as inoculum. Conclusions: The results indicated that A. seyal is a nonselective host that can establish effective symbiosis with Mesorhizobium spp. strains from diverse genomic backgrounds and that the selected A. seyal‐nodulating rhizobia could enhance plant growth. Significance and Impact of the Study: These results showed the important role that A. seyal could play in the improvement of reafforestation process as a promiscuous host, which can establish effective symbiosis with rhizobia from diverse genomic backgrounds.     

Cherimolacyclopeptide D, a novel cycloheptapeptide from the seeds of Annona cherimola

In a chemical investigation of the seeds of Annona cherimola, a natural cyclic heptapeptide, cherimolacyclopeptide D, were isolated and purified by HPLC with three known cyclic peptides, cherimolacyclopeptides A, B and C. The structure was established by various analyses including MS/MS fragmentation, spectroscopic and chemical evidences.     

Stem Nodulation in Legumes: Diversity,Mechanisms, and Unusual Characteristics

Rhizobia can establish a nitrogen-fixing symbiosis with plants of the Leguminosae family. They elicit on their host plant the formation of new organs, called nodules, which develop on the roots. A few aquatic legumes, however, can form nodules on their stem at dormant root primordia. The stem-nodulating legumes described so far are all members of the genera Aeschynomene, Sesbania, Neptunia, and Discolobium. Their rhizobial symbionts belong to four genera already described: Rhizobium, Bradyrhizobium, Sinorhizobium, and Azorhizobium. This review summarizes our current knowledge on most aspects of stem nodulation in legumes, the infection process and nodule development, the characterization and unusual features of the associated bacteria, and the molecular genetics of nodulation. Potential use as green manure in lowland rice of these stem-nodulating legumes, giving them agronomical importance, is also discussed.     

Genetic diversity and distribution of Bradyrhizobium and Azorhizobium strains associated with the herb legume Zornia glochidiata sampled from across Senegal

Herb legumes have great potential for rehabilitation of semi-arid degraded soils in Sahelian ecosystems as they establish mutualistic symbiosis with N₂-fixing rhizobia. A phylogenetic analysis was performed for 78 root nodule bacteria associated with the common Sahelian herb legume Zornia glochidiata Reichb ex DC in Senegal. Based on ITS (rDNA16S-23S) and recA sequences, these strains were shown to belong to the two genera Bradyrhizobium and Azorhizobium. Strains of this latter, although frequent, formed small and ineffective nodules and suggested a parasitism rather than a symbiotic association. A potential negative effect of Azorhizobium on Zornia growth was tested for when inoculated alone or in association with a Bradyrhizobium strain. Bradyrhizobium isolates were distributed in four groups. Groups A and B were two sister clades in a larger monophyletic group also including Bradyrhizobium liaoningense, Bradyrhizobium yuanmingense, and Bradyrhizobium japonicum. Strains of cluster D fell in a sister clade of the photosynthetic Bradyrhizobium sp. group, including ORS278, whereas group C appeared to be divergent from all known Bradyrhizobium clusters. Amplified fragment length polymorphism (AFLP) clustering was congruent with ITS and recA phylogenies, but displayed much more variability. However, within the main Bradyrhizobium clades, no obvious relationship could be detected between clustering and geographical origin of the strains. Each sub-cluster included strains sampled from different locations. Conversely, Azorhizobium strains showed a tendency in the phylogeny to group together according to the site of sampling. The predominance of ineffective Azorhizobium strains in the nodules of Zornia roots, the large Bradyrhizobium genetic diversity and the geographical genetic diversity pattern are explored.     

Aspects cliniques, biologiques et thérapeutiques de la cryptorchidie diagnostiquée à l’âge adulte: analyse d’une série de 69 cas

Objective

To report the clinical, biological and therapeutic features of adult cryptorchidism and to determine whether orchidopexy at adulthood may improve male fertility.

Material and methods

We retrospectively studied the clinical pattern, biological and therapeutic features of 69 men aged of more than 18 years admitted for cryptorchidism at the urological department of Aristide-Le-Dantec teaching hospital between January 1999 and December 2007.

Results

The mean age of our patients was 31.04 ± 8.4 years. In the majority of cases, cryptorchidism was diagnosed in a context of infertility (38 cases), scrotum vacancy (21 cases) and testicular cancer (six cases). Cryptorchidism was unilateral in 69.5% and bilateral in 30.4% of cases. Semen analyses were done for 60 patients and showed azoospermia in 46.6%, oligozoospermia in 38.3% and a normal sperm count in 15% of cases. In all bilateral cryptorchidism cases, semen analyses showed azoospermia. At surgery, the undescended testis was found in 66 cases (95.6%) and orchidopexy was the most done surgical procedure. Seven patients (without testicular cancer) underwent unilateral orchiectomy and histology of specimens showed sertoli-cell-only syndrome with no spermatogenesis in all cases. The histological type of testicular cancer was seminoma (three cases) and embryonic carcinoma (three cases). In azoospermic men (28 cases) no induction of spermatogenesis was achieved after orchidopexy. In infertile patients, the improvement of sperm count was seen in three patients with unilateral cryptorchidism. Three patients with unilateral crytorchidism achieved pregnancy (pregnancy rate of 7.8%).

Conclusion

Orchidopexy for adult cryptorcidism had little impact in male fertility. Because of the risk of testicular cancer, orchidectomy was recommended as treatment of unilateral cryptorchidism. But with the recent development of TESE, orchidopexy appears as a reasonable treatment of adult cryptorchidism.