The Influence of Arbuscular Mycorrhizal Fungi Inoculation on micro-propagated hybrid yam (Dioscorea spp.) growth and root knot nematode (Meloidogyne spp.) suppression

Article Purchased; Published online: 12 October 2016The use of commercial inoculants containing non-indigenous arbuscular mycorrhizal fungi (AMF) is an emerging technology towards improving crop production in Africa. The present study aims at evaluating the influence of two strains of commercial arbuscular mycorrhizal fungi (AMF) products, based on Funneliformis mosseae and Glomus dussii, on yam growth and on root knot nematodes suppression. Using micropropagated plantlets two cultivars each of Dioscorea alata (TDa98-01183 and TDa98-165), and D. rotundata (TDr97-00551 and TDr 745) were inoculated with the F. mosseae and G. dussii products separately, at transplanting into 2L pots, and then inoculated one month later with 500 infective juveniles of Meloidogyne spp. and grown for further seven months in the greenhouse. Results demonstrated that even with low colonization rates (6%), AMF led to improved yam growth, especially for D. alata. When challenged with Meloidogyne spp., AMF inoculation significantly suppressed galling symptoms across the treatments and led to higher tuber yield. This study indicates the potential of AMF to sustainably improve yam quality and productivity, although further screening should be done in order to identify a suitable combination AMF species/strain x cultivar compatibility to optimise the results

Effect of two species of arbuscular mycorrhizal fungi inoculation on development of micro-propagated yam plantlets and suppression of Scutellonema bradys (Tylenchideae)

Using two commercially available arbuscular mycorrhizal fungal (AMF) products, one based on Funneliformis mosseae and the other on Glomus dussii, an experiment was conducted to assess their effect on yam growth and ability to suppress nematode damage in pots. Four yam cultivars (cvs) were used: two Dioscorea alata cvs (TDa98-01183 and TDa98-165), and two Dioscorea rotundata cvs (TDr97- 00551 and TDr 745). Micropropagated yam plantlets were inoculated either with F. mosseae or with G. dussii at the stage of transplanting into 2L pots and - one month later - with 500 vermiform Scutellonema bradys. The plantlets were grown for further six months in the greenhouse at IITA-Ibadan. The results showed that the presence of AMF tended to lead to improved growth of yam, especially D. alata cvs, as compared with the non-arbuscular mycorrhizal control plants. When challenged with the yam nematode S. bradys, plantlets of the two D. alata cultivars pre-inoculated with F. mosseae and cv TDr97-00551 pre-inoculated with G. dussii yielded significantly higher tuber weights compared to non- AMF control plantlets. S. bradys densities on yam plantlets pre-inoculated with AMF were generally suppressed, although no differences were observed in visible damage scores, which remained low or absent across treatments

Genetic diversity of the arbuscular mycorrhizal fungus Glomus intraradices as determined by mitochondrial large subunit rRNA gene sequences is considerably higher than previously expected

Summary: • Glomus intraradices is a widespread arbuscular mycorrhizal fungus (AMF), which has been found in an extremely broad range of habitats, indicating a high tolerance for environmental factors and a generalist life history strategy. Despite this ecological versatility, not much is known about the genetic diversity of this fungal species across different habitats or over large geographic scales. • A nested polymerase chain reaction (PCR) approach for the mitochondrial rRNA large subunit gene (mtLSU), distinguished different haplotypes among cultivated isolates of G. intraradices and within mycorrhizal root samples from the field. • From analysis of 16 isolates of this species originating from five continents, 12 mitochondrial haplotypes were distinguished. Five additional mtLSU haplotypes were detected in field‐collected mycorrhizal roots. Some introns in the mtLSU region appear to be stable over years of cultivation and are ancestral to the G. intraradices clade. • Genetic diversity within G. intraradices is substantially higher than previously thought, although some mtLSU haplotypes are widespread. A restriction fragment length polymorphism approach also was developed to distinguish mtLSU haplotypes without sequencing. Using this molecular tool, intraspecific genetic variation of an AMF species can be studied directly in field plants

Unique arbuscular mycorrhizal fungal communities uncovered in date palm plantations and surrounding desert habitats of Southern Arabia

The main objective of this study was to shed light on the previously unknown arbuscular mycorrhizal fungal (AMF) communities in Southern Arabia. We explored AMF communities in two date palm (Phoenix dactylifera) plantations and the natural vegetation of their surrounding arid habitats. The plantations were managed traditionally in an oasis and according to conventional guidelines at an experimental station. Based on spore morphotyping, the AMF communities under the date palms appeared to be quite diverse at both plantations and more similar to each other than to the communities under the ruderal plant, Polygala erioptera, growing at the experimental station on the dry strip between the palm trees, and to the communities uncovered under the native vegetation (Zygophyllum hamiense, Salvadora persica, Prosopis cineraria, inter-plant area) of adjacent undisturbed arid habitat. AMF spore abundance and species richness were higher under date palms than under the ruderal and native plants. Sampling in a remote sand dune area under Heliotropium kotschyi yielded only two AMF morphospecies and only after trap culturing. Overall, 25 AMF morphospecies were detected encompassing all study habitats. Eighteen belonged to the genus Glomus including four undescribed species. Glomus sinuosum, a species typically found in undisturbed habitats, was the most frequently occurring morphospecies under the date palms. Using molecular tools, it was also found as a phylogenetic taxon associated with date palm roots. These roots were associated with nine phylogenetic taxa, among them eight from Glomus group A, but the majority could not be assigned to known morphospecies or to environmental sequences in public databases. Some phylogenetic taxa seemed to be site specific. Despite the use of group-specific primers and efficient trapping systems with a bait plant consortium, surprisingly, two of the globally most frequently found species, Glomus intraradices and Glomus mosseae, were not detected neither as phylogenetic taxa in the date palm roots nor as spores under the date palms, the intermediate ruderal plant, or the surrounding natural vegetation. The results highlight the uniqueness of AMF communities inhabiting these diverse habitats exposed to the harsh climatic conditions of Southern Arabia

Successional sequence of forest types in a disturbed dry forest reserve in southern Benin, West Africa

Published online: 01 July 2001Human pressure on forest resources in southern Benin has led to a dramatic reduction and disturbance of natural forest patches. The largest remaining forest reserve in southern Benin is the Lama forest, which is known to be a reserve for many endangered species and situated in the boundary between dry forest and savanna. From cluster analysis and hierarchical classification of tree species composition, five forest types were identified in the Lama forest, and ordination techniques were used to determine to what extent these forest types were associated with physiognomic tree characteristics. The geographical position of vegetation plots was used to examine the spatial distribution of the identified forest types. The forest types were interpreted as levels in a successional sequence ranging from either disturbed forest or formerly cultivated farmland to dense forest. Based on the outlined succession sequence it was suggested that reforestation should focus on establishment of Anogeissus leiocarpus, Albizia zygia, Lannea nigritana, Ficus exasperata and Lonchocarpus sericeus as these tree species are associated with the initial forest types

Impacts des dechets liquides des navires sur l’ecosysteme marin: casdes larves de crevettes de Saumure, Artemia Salina Leach

Cette étude a permis d’évaluer les impacts des rejets des déchets liquides des navires. Elle a été consacrée à l’analyse des polluants contenus dans les rejets liquides des navires afin d’apprécier leur conformité aux normes ainsi que leur toxicité.Les enquêtes réalisées ont révélé, qu’il n’existe au Port de Cotonou, aucun texte réglementant la gestion des déchets liquides des navires. En effet, certains capitaines ou consignataires de navires confieraient les déchets liquides à bord aux personnes sans aucune spécialisation en la matière.En outre, certaines allégations ont mentionné l’éventualité qu’une partie de ces effluents liquides soit déversée de manière illicite dans les eaux marines et portuaires.Nos investigations nous ont cependant permis de découvrir que d’autres navires qualifiés de navires modernes sont équipés de dispositifs de traitement de leurs déchets liquides avant leurs rejets en mer.Par ailleurs, les résultats obtenus à l’issue des différents tests, révèlent que les éléments inorganiques tels que les ions nitrates, nitrites, ammonium et phosphates, susceptibles de polluer le milieu récepteur et contenus dans les échantillons E1, E2 et E3, sont en concentrations faibles par rapport aux normes de rejet des eaux usées.La pollution du milieu marin par ces éléments n’est donc pas considérable. Par contre le plomb dont la teneur est également faible dans ces milieu, peut porter préjudice à la vie aquatique surtout en raison de son caractère à être bio-accumulé par les organismes vivants.Notons également que les valeurs de DCO et de DBO5 ont permis de comprendre que les eaux usées des navires, pour des quantités de rejets supérieures à 30kg/J sont susceptibles de polluer les milieux récepteurs.Ainsi, au regard de tout ce qui précède, il convient de signaler que le sujet abordé a apporté une contribution appréciable dans la sensibilisation des acteurs du Port de Cotonou sur l’importance de la gestion efficace des déchets liquides en provenance des navires ; ceci en vue d’un assainissement adéquat de l’environnement maritime et portuaire au Port de Cotonou.Mots clés: Impacts ; déchets liquides ; navire, PortEnglish AbstractThis study assessed the impacts of shipboard liquid waste discharges. It was devoted to the analysis of the pollutants contained in the liquid discharges of ships in order to assess their compliance with the standards and their toxicity. The surveys carried out revealed that there is no legislation in the Port of Cotonou governing waste management. But it is certain that the waste arrives, that it is received by people without any specialization in the matter.It is also a certainty that a part is unlawfully dumped into marine and port waters. However, our investigations have enabled us to discover that some ships qualified as modern ships are equipped themselves with devices for treating their liquid waste before their discharge to the sea.Moreover, the results obtained from the various tests reveal that the inorganic elements such as the nitrate, nitrite, ammonium and phosphate ions capable of polluting the receiving medium and contained in the samples E1, E2 and E3 are Low concentrations compared to wastewater discharge standards.The pollution of the marine environment by these elements is therefore not considerable. On the other hand, lead, which is also low in these mediums, can be harmful to aquatic life, especially because of its bio-accumulated character by living organisms.It should also be noted that the COD and BOD5 values have made it possible to understand that wastewater from ships, for quantities greater than 30 kg / day, is liable to pollute the receiving media.Thus, in view of all the above, it should be pointed out that the subject matter has made a significant contribution in raising the awareness of the actors of the Port of Cotonou on the importance of the effective management of waste from ships; With a view to an adequate reorganization of the maritime and port environment in the Port of Cotonou.Keywords: Impacts; Liquid waste; Ship, harbo

Comparison of pathogenicity of geographically separate populations of Scutelllonema bradys on yam (Dioscorea spp.) in West Africa

Nine Nigerian populations of Scutellonema bradys, obtained from infected yam (Dioscorea spp.), were assessed following inoculation onto susceptible yam (Dioscorea rotundata) cv. TDr131 in pot and field experiments in Nigeria between 2002 and 2004. In addition, geographically separated populations, two each from Benin, Burkina Faso, Côted’Ivoire, Ghana, Mali, Nigeria and Togo, were compared in pot assays in Benin between 2003 and 2004. The effect of different nematode populations on tuber yield was variable and depended on the experiment. Moreover, S. bradys damage and yield reduction was more pronounced when plants were under stress as evidenced by production of small tubers. Nematode numbers increased for all S. bradys populations during storage, by as much as 37.3 times for one population from Nigeria. Similarly, up to 44.5% tuber weight loss was observed during storage compared with control tubers (28%), with differences in weight loss evident among some S. bradys population treatments. Dry rot symptoms occurred on both S. bradys infected and also uninfected tubers, indicating that dry rot is an unreliable diagnostic for yam nematode infection. However, dry rot severity was higher on infected tubers, varying with some S. bradys populations. In conclusion, this study demonstrates that nematode densities and yam dry rot severity (following infection with the different nematode populations) was variable and differed between years, but did not identify any populations that had higher pathogenicity. Results imply, however, that greater variability of S. bradys damage may occur because of the effects of environment and host differences, rather than between the pathogenicity of these populations

Racocetra beninensis from sub-Saharan savannas : a new species in the Glomeromycetes with ornamented spores

A new fungal species is described under the epithet Racocetra beninensis (Racocetraceae, Glomeromycota). It forms white to creamy-white, globose to sub-globose (sometimes oval) glomerospores terminally on sporogenous Cells. Spores measure 195-335 mu m diam and have two spore walls: a three-layered outer wall and a three-layered inner wall. The Outer spore surface is ornamented with rounded wart-like projections that measure 0.9-2.8 x 0.9-3.8 mu m and are spaced (2.2-)4.0-11.0 mu m apart. The germination shield that forms on the outer surface of the inner wall is multiple-lobed (6-10 lobes) and (sub-)hyaline or occasionally yellowing with age. The lobes regularly bear a single germ tube initiation. The fungus differs from other Racocetra species by spore size and color, ornamentation type, and outer spore wall staining reaction. It has been frequently recovered from sites under natural vegetation and newly cultivated or post-harvest yam (Dioscorea spp.) fields in the sub-Saharan Sudan and Guinea savannas of Benin (West Africa)

Efficacy of indigenous arbuscular mycorrhizal fungi for promoting white yam (; Dioscorea rotundata; ) growth in West Africa

Tuber yields of yam (Dioscorea spp.), a main staple food in West Africa. are steadily declining per unit area, an incidence for which decreasing soil fertility due to increasing land pressure is largely blamed. Recent studies demonstrated the association of a plethora of arbuscular mycorrhizal fungi (AMF) with yam, soil microorganisms crucial for natural soil fertility. Thus, inoculation of yam with AMF could help reverse declining yields, above all in soils with a strong loss of AMF diversity due to agricultural land use intensification. In a pot experiment, we studied the impact of indigenous and exotic AMF isolates on growth performance of micro-propagated white yam plantlets (Dioscorea rotundata, cv.TDr89/02461). Pots were inoculated with single spore derived isolates of Glomus etunicatum, originating from tropical environments in West Africa, South America and Asia and, for comparison, also with three isolates of other AMP species from temperate Europe. In addition, isolates of nine AMF species originating from sub-Saharan West Africa and three commercial AMF were compared. Six of the 11 isolates of G. etunicatum from the tropics increased yam tuber growth compared with non-mycorrhizal controls, whereas the European AMP species tended to be less efficient but led to an increased tuber phosphorus concentration. The African isolates of G. mosseae, G. hoi, G. etunicatum, Acaulospora scrobiculata and A. spinosa generally led to increased tuber growth compared with non-mycorrhizal controls, while isolates of G. sinuosum and Kuklospora kentinensis did not. Our study indicates that inoculation of micro-propagated yam plantlets with selected indigenous AMP could potentially constitute a sustainable measure to boost yam productivity again in degraded African soils. (C) 2010 Elsevier B.V. All rights reserved