Genetic diversity of Verticillium dahliae isolates from olive trees in Algeria

Verticillium wilt of olive trees (Olea europaea L.), a wilt caused by the soil-borne fungus Verticillium dahliae (Kleb), is one of the most serious diseases in Algerian olive groves. To assess the pathogenic and genetic diversity of olive-infecting V. dahliae populations in Algeria, orchards from the two main olive-producing regions (north-western Algeria and Kabylia) were sampled and 27 V. dahliae isolates were recovered. For purposes of comparison, V. dahliae strains from France and Syria were added to the analysis. By means of PCR primers that specifically discriminate between defoliating (D) and non-defoliating (ND) V. dahliae pathotypes it was shown that all V. dahliae isolates belonged to the ND pathotype. The amount of genetic variation between the 43 isolates was assessed by random amplification of polymorphic DNA (RAPD). A total of 16 RAPD haplotypes were found on the basis of the presence or absence of 25 polymorphic DNA fragments. Genotypic diversity between the 27 Algerian isolates was low, with two RAPD haplotypes accounting for 70% of all isolates. Genotypic diversity was however greater between isolates from Kabylia than between isolates from north-western Algeria. Cluster analysis showed that most of the Algerian V. dahliae isolates grouped together with the French and Syrian isolates. On the basis of their ability to form heterokaryons with each other, a subset of 25 olive-pathogenic isolates was grouped into a single vegetative compatibility group (VCG). These results suggest that the olive-infecting V. dahliae populations in Algeria show limited diversity and that caution should be taken to prevent introduction of the D pathotype

Genetic diversity of Verticillium dahliae isolates from olive trees in Algeria

Summary. Verticillium wilt of olive trees (Olea europaea L.), a wilt caused by the soil-borne fungus Verticillium dahliae (Kleb), is one of the most serious diseases in Algerian olive groves. To assess the pathogenic and genetic diversity of olive-infecting V. dahliae populations in Algeria, orchards from the two main olive-producing regions (north-western Algeria and Kabylia) were sampled and 27 V. dahliae isolates were recovered. For purposes of comparison, V. dahliae strains from France and Syria were added to the analysis. By means of PCR primers that specifically discriminate between defoliating (D) and non-defoliating (ND) V. dahliae pathotypes it was shown that all V. dahliae isolates belonged to the ND pathotype. The amount of genetic variation between the 43 isolates was assessed by random amplification of polymorphic DNA (RAPD). A total of 16 RAPD haplotypes were found on the basis of the presence or absence of 25 polymorphic DNA fragments. Genotypic diversity between the 27 Algerian isolates was low, with two RAPD haplotypes accounting for 70% of all isolates. Genotypic diversity was however greater between isolates from Kabylia than between isolates from north-western Algeria. Cluster analysis showed that most of the Algerian V. dahliae isolates grouped together with the French and Syrian isolates. On the basis of their ability to form heterokaryons with each other, a subset of 25 olive-pathogenic isolates was grouped into a single vegetative compatibility group (VCG). These results suggest that the olive-infecting V. dahliae populations in Algeria show limited diversity and that caution should be taken to prevent introduction of the D pathotype

Genetic diversity of Verticillium dahliae isolates from olive trees in Algeria

Verticillium wilt of olive trees (Olea europaea L.), a wilt caused by the soil-borne fungus Verticillium dahliae (Kleb), is one of the most serious diseases in Algerian olive groves. To assess the pathogenic and genetic diversity of olive-infecting V. dahliae populations in Algeria, orchards from the two main olive-producing regions (north-western Algeria and Kabylia) were sampled and 27 V. dahliae isolates were recovered. For purposes of comparison, V. dahliae strains from France and Syria were added to the analysis. By means of PCR primers that specifically discriminate between defoliating (D) and non-defoliating (ND) V. dahliae pathotypes it was shown that all V. dahliae isolates belonged to the ND pathotype. The amount of genetic variation between the 43 isolates was assessed by random amplification of polymorphic DNA (RAPD). A total of 16 RAPD haplotypes were found on the basis of the presence or absence of 25 polymorphic DNA fragments. Genotypic diversity between the 27 Algerian isolates was low, with two RAPD haplotypes accounting for 70% of all isolates. Genotypic diversity was however greater between isolates from Kabylia than between isolates from north-western Algeria. Cluster analysis showed that most of the Algerian V. dahliae isolates grouped together with the French and Syrian isolates. On the basis of their ability to form heterokaryons with each other, a subset of 25 olive-pathogenic isolates was grouped into a single vegetative compatibility group (VCG). These results suggest that the olive-infecting V. dahliae populations in Algeria show limited diversity and that caution should be taken to prevent introduction of the D pathotype

Utilización de microorganismos nativos en la producción de aves de traspatio en Burkina Faso

Objective: To characterize the effect of native microorganisms on backyard poultry production in western-central Burkina Faso. Materials and Methods: The study was divided into two parts: broilers and laying hens. Two groups of growing broilers, three months old and 0,54 kg live weight as average (ten broilers per group) were used. A complete randomized design was applied to determine the growth dynamics of the animals for 75 days. During this period, egg laying was evaluated for two batches of laying hens averaging five months of age and 0,82 kg live weight (10 hens per treatment). Two treatments were established: T1) typical farm diet, T2) typical diet, plus combined inclusion of native microorganisms in drinking water and feedstuffs at the rate of 6 mL/animal/day and 4,0 % of daily dry feedstuff weight, respectively. Results: There were no significant differences between treatments with regards to broiler growth. The final live weight was 0,93 kg, with a gain of 0,005 kg/chicken/day. Laying hens did not differ in growth either, with an average of 0,003 kg/day and a final weight of 1,02 kg. Broilers had high mortality (50 and 30 % for T1 and T2, respectively). However, no deaths were recorded in laying hens. Egg laying did not differ between treatments either, but egg weight in T2 was higher (p < 0,05) than in T1, with 40 and 30 g, respectively. Conclusions: There was no evidence of a significant effect of native microorganisms on the productivity of the poultry flock, but there was evidence of a significant effect on egg weight and viability of the animals under study

Association of shifting populations in the root zone microbiome of millet with enhanced crop productivity in the Sahel region (Africa)

This study characterized specific changes in the millet root zone microbiome stimulated by long-term woody-shrub intercropping at different sites in Senegal. At the two study sites, intercropping with woody shrubs and shrub residue resulted in a significant increase in millet [Pennisetum glaucum (L.) R. Br.] yield (P < 0.05) and associated patterns of increased diversity in both bacterial and fungal communities in the root zone of the crop. Across four experiments, operational taxonomic units (OTUs) belonging to Chitinophaga were consistently significantly (P < 0.001) enriched in the intercropped samples, and "Candidatus Koribacter" was consistently significantly enriched in samples where millet was grown alone. Those OTUs belonging to Chitinophaga were enriched more than 30-fold in residue-amended samples and formed a distinct subgroup from all OTUs detected in the genus. Additionally, OTUs belonging to 8 fungal genera (Aspergillus, Coniella, Epicoccum, Fusarium, Gibberella, Lasiodiplodia, Penicillium, and Phoma) were significantly (P < 0.005) enriched in all experiments at all sites in intercropped samples. The OTUs of four genera (Epicoccum, Fusarium, Gibberella, and Haematonectria) were consistently enriched at sites where millet was grown alone. Those enriched OTUs in intercropped samples showed consistently large-magnitude differences, ranging from 30-to 1,000-fold increases in abundance. Consistently enriched OTUs in intercropped samples in the genera Aspergillus, Fusarium, and Penicillium also formed phylogenetically distinct subgroups. These results suggest that the intercropping system used here can influence the recruitment of potentially beneficial microorganisms to the root zone of millet and aid subsistence farmers in producing higher-yielding crops

Response of soil microbial properties to long-term application of organic and inorganic amendments in a tropical soil (Saria, Burkina Faso)

Soil microbial biomass carbon (MBC), &#946;-glucosidase, acid phosphatase and fluorescein diacetate (FDA) activities and bacterial community structure were assessed in a long-term (26 years) experiment, at physiological stages of sorghum growth, comparing different management methods for organic (manure, straw residues) and inorganic (urea) amendments at the INERA field station in Saria (Burkina Faso). Annual application of manure led to the highest soil microbial biomass and enzyme activities. Investigations indicated that only microbial biomass and &#946;-glucosidase activities were affected during the cropping season. Phosphatase and FDA enzyme activities did not depend on the crop development stages. The application of N fertilizer modified phosphatase and FDA enzyme activities, the activities being higher in soils amended with N fertilizer. The bacterial community structure was analyzed by PCR-denaturing gradient gel electrophoresis (PCR-DGGE) targeting the eubacterial 16S rRNA gene. Cluster analysis of PCR-DGGE patterns showed two major clusters, the first containing the mineral fertilization and straw treatments and the second, the straw + urea, manure and manure + urea treatments. Sorghum grain yields were the highest for manure treatments. In this long-term experiment, applying straw did not produce a better grain yield than that obtained in the un-amended plot

Influence of tropical leaf litter on nitrogen mineralization and community structure of ammonia-oxidizing bacteria

Description of the subject: The present study concerns the relationships among leaf litter decomposition, substrate quality, ammonia-oxidizing bacteria (AOB) community composition and nitrogen (N) availability. Decomposition of organic matter affects the biogeochemical cycling of carbon (C) and N. Since the composition of the soil microbial community can alter the physiological capacity of the community, it is timely to study the litter quality effect on N dynamic in ecosystems. Objectives. The aim of this study was to determine the influence of leaf litter decomposition on N mineralization. The specific objectives of this study were to evaluate the influence of the litter biochemistry of five plants species (Faidherbia albida A.Chev., Azadirachta indica A.Juss., Casuarina equisetifolia L., Andropogon gayanus Kunth and Eragrostis tremula Hochst. ex Steud.) on N mineralization in a tropical ferrous soil (Lixisol), nitrification, and genetic diversity of ammonia-oxidizing bacteria. Denaturing gradient gel electrophoresis (DGGE) of amplified fragments of genes coding for 16S rRNA was used to study the development of bacterial communities during decomposition of leaf litter in soils. Method. Community structure of AOB was determined at two time periods: day 0 and day 140. Ten strains were tested and each of these strains produced a single band. Thus, DGGE DNA band patterns were used to estimate bacterial diversity. Plant secondary compounds such as polyphenols are purported to influence nutrient cycling by affecting organic matter degradation, mineralization rates, N availability and humus formation. In a laboratory study, we investigated the influence of six phenolic acids (ferulic, gallic, vanillic, syringic, p-coumaric and p-HBA acids) commonly found in the plant residues on N mineralization and NH4+ and NO3- production in soils. Results. The results showed that litter type did affect soil nitrification. Faidherbia albida litter was associated with increased inorganic N in soil after 140 days of incubation while A. gayanus and C. equisetifolia litter immobilized N. Azadirachta indica and E. tremula amendments had no significant effects in N mineralization. The results show that the addition of six phenolic acids significantly reduced NH4+ and NO3- compared to the control soil but had no significant effect on N mineralization. For the community of ammonium-oxidizing bacteria, a litter quality effect was noted, but the incubation time effect was more pronounced, except for C. equisetifolia litter. Conclusions. Results confirmed that the N mineralization changed with litter type under controlled conditions and the genetic structure of AOB is highly dependent on litter quality

Long-term Piliostigma reticulatum intercropping in the Sahel : crop productivity, carbon sequestration, nutrient cycling, and soil quality

Throughout the Sahel, food insecurity remains a persistent threat. A few studies have shown that Piliostigma reticulatum, a dominant native shrub in parklands from Senegal to Sudan, can positively impact crop yields. However, there are no experiments that measure whether this species can stabilize long-term crop productivity under erratic rainfall. Therefore, an 11-year study of an optimized P. reticulatum intercropping system (1000 shrubs ha(-1) with annual coppiced residue soil amendments) was initiated in 2004 in Senegal, West Africa to determine its impacts on crop productivity and soil quality. The experiment was a split-plot factorial design with the main plot shrubs (with and without) and the subplot fertilizer rate (0, 0.5, 1, and 1.5 times the recommended N-P-K rate) with an annual groundnut (Arachis hypogaea) and pearl millet (Pennisetum glaucum) crop rotation. Yield, biomass, soil carbon, and soil and plant nutrient data from 2011 to 2015 were compared with data from 2004 to 2007. The presence of shrubs increased millet and groundnut yield from 2011 to 2015 and rainfall water use efficiency (WUE) between 2004 and 2015. Without fertilizer addition, the shrub plots had approximately 2 times greater millet yield throughout the duration of this experiment. The presence of shrubs also improved soil quality, as evidenced by significantly greater C in the fraction <53 mu m and total C in shrub over non-shrub plots. Thus, P. reticulatum intercropping promotes C sequestration. In addition, five macronutrients (N, K, Ca, Mg, S) and two micronutrients (Mn and Cu) were significantly greater in the shrub plots. The results provide strong evidence that intercropping with P. reticulatum is an ecological agroforestry system for the Sahel that can remediate soils, increase crop yields, and buffer climate change

Local Beneficial Microorganisms Impact Carbon and Nitrogen Mineralization in a Lixisol Incubated with Organic Waste Products

Growing awareness of the environmental impact of intensive agriculture has prompted a quest for more sustainable approaches. The most promising alternatives include the application of organic waste products (OWPs), as well as biofertilizers containing local beneficial microorganisms (BMs) on cultivated soils. This study was designed to assess the effects of BMs on carbon and nitrogen mineralization of OWPs. A 28-day laboratory incubation experiment was conducted at 28 °C with a soil, three OWPs (poultry litter (PL), cow dung (CD), and sewage sludge (SS)), and three BMs (groundnut + millet from Saint-Louis (LGM), groundnut from the southern groundnut basin (BG), and rice from the southern groundnut basin (BR) in Senegal), alone and combined. The results showed that the C mineralization from OWP + BM + soil mixtures exceeded (range 13–41%) those measured for OWP + soil. The BM input induced an increase or reduction in OWP nitrogen mineralization, depending on the type of BM and OWP. However, the net mineral nitrogen (Nmin) obtained with the PL-LGM and SS-BG combinations was 13.6- and 1.7-fold higher than with PL and SS, respectively, at 28 days. The addition of BM seemed to lead to a decrease in the C: N ratio, an improvement in the availability of nitrogen, and an increase in microbial activity in the OWP + BM + soil mixture. Our results generated new information on the variation patterns of OWP carbon and nitrogen in OWP-BM-soil systems. This novel insight will be developed to guide the most appropriate choice of OWP-BM mixtures for improved fertilization in sustainable production systems