Juan A. Navas-Cortés

Intestinal Microbiota Is Influenced by Gender and Body Mass Index.

Intestinal microbiota changes are associated with the development of obesity. However, studies in humans have generated conflicting results due to high inter-individual heterogeneity in terms of diet, age, and hormonal factors, and the largely unexplored influence of gender. In this work, we aimed to identify differential gut microbiota signatures associated with obesity, as a function of gender and changes in body mass index (BMI). Differences in the bacterial community structure were analyzed by 16S sequencing in 39 men and 36 post-menopausal women, who had similar dietary background, matched by age and stratified according to the BMI. We observed that the abundance of the Bacteroides genus was lower in men than in women (P<0.001, Q = 0.002) when BMI was > 33. In fact, the abundance of this genus decreased in men with an increase in BMI (P<0.001, Q<0.001). However, in women, it remained unchanged within the different ranges of BMI. We observed a higher presence of Veillonella (84.6% vs. 47.2%; X2 test P = 0.001, Q = 0.019) and Methanobrevibacter genera (84.6% vs. 47.2%; X2 test P = 0.002, Q = 0.026) in fecal samples in men compared to women. We also observed that the abundance of Bilophila was lower in men compared to women regardless of BMI (P = 0.002, Q = 0.041). Additionally, after correcting for age and sex, 66 bacterial taxa at the genus level were found to be associated with BMI and plasma lipids. Microbiota explained at P = 0.001, 31.17% variation in BMI, 29.04% in triglycerides, 33.70% in high-density lipoproteins, 46.86% in low-density lipoproteins, and 28.55% in total cholesterol. Our results suggest that gut microbiota may differ between men and women, and that these differences may be influenced by the grade of obesity. The divergence in gut microbiota observed between men and women might have a dominant role in the definition of gender differences in the prevalence of metabolic and intestinal inflammatory diseases.

Yield loss in chickpeas in relation to development of fusarium wilt epidemics.

ABSTRACT Development of 108 epidemics of Fusarium wilt of chickpea caused by Fusarium oxysporum f. sp. ciceris were studied on cvs. P-2245 and PV-61 in field microplots artificially infested with races 0 and 5 of F. oxysporum f. sp. ciceris in 1986 to 1989. Disease progression data were fitted to the Richards model using nonlinear regression. The shape parameter was influenced primarily by date of sowing and, to a lesser extent, by chick-pea cultivars and races of F. oxysporum f. sp. ciceris. Fusarium wilt reduced chickpea yield by decreasing both seed yield and seed weight. These effects were related to sowing date, chickpea cultivar, and virulence of the prevalent F. oxysporum f. sp. ciceris race. Regression models were developed to relate chickpea yield to Fusarium wilt disease intensity with the following independent variables: time to initial symptoms (t(is)), time to inflection point (t(ip)) of the disease intensity index (DII) progress curve, final DII (DII(final)), standardized area under DII progress curve (SAUDPC), and the Richards weighted mean absolute rate of disease progression (rho). Irrespective of the chickpea cultivar x pathogen race combination, the absolute and relative seed yields decreased primarily by delayed sowing. The relative seed yield increased with the delay in t(is) and t(ip) and decreased with increasing DII(final), SAUDPC, and rho. A response surface as developed in which seed yield loss decreased in a linear relationship with the delay in t(is) and increased exponentially with the increase of rho.

Influence of Temperature and Inoculum Density of Fusarium oxysporum f. sp. ciceris on Suppression of Fusarium Wilt of Chickpea by Rhizosphere Bacteria.

The effects of temperature and inoculum density of Fusarium oxysporum f. sp. ciceris race 5 on suppression of Fusarium wilt in chickpea (Cicer arietinum) cv. PV 61 by seed and soil treatments with rhizobacteria isolated from the chickpea rhizosphere were studied in a model system. Disease development over a range of temperatures (20, 25, and 30 degrees C) and inoculum densities (25 to 1,000 chlamydospores per gram of soil) was described by the Gompertz model. The Gompertz relative rate of disease progress and final amount of disease increased exponentially and monomolecularly, respectively, with increasing inoculum densities. Disease development was greater at 25 degrees C compared with 20 and 30 degrees C. At 20 and 30 degrees C, disease development was greater at 250 to 1,000 chlamydospores per gram of soil compared with 25 to 100 chlamydospores per gram of soil. At 25 degrees C, increasing inoculum densities of the pathogen did not influence disease. Nineteen Bacillus, Paenibacillus, Pseudomonas, and Stenotrophomonas spp. out of 23 bacterial isolates tested inhibited F. oxysporum f. sp. ciceris in vitro. Pseudomonas fluorescens RGAF 19 and RG 26, which did not inhibit the pathogen, showed the greatest Fusarium wilt suppression. Disease was suppressed only at 20 or 30 degrees C and at inoculum densities below 250 chlamydospores per gram of soil. Bacterial treatments increased the time to initial symptoms, reduced the Gompertz relative rate of disease progress, and reduced the overall amount of disease developed.

Integrated Management of Fusarium Wilt of Chickpea with Sowing Date, Host Resistance, and Biological Control

ABSTRACT A 3-year experiment was conducted in field microplots infested with Fusarium oxysporum f. sp. ciceris race 5 at Córdoba, Spain, in order to assess efficacy of an integrated management strategy for Fusarium wilt of chickpea that combined the choice of sowing date, use of partially resistant chickpea genotypes, and seed and soil treatments with biocontrol agents Bacillus megaterium RGAF 51, B. subtilis GB03, nonpathogenic F. oxysporum Fo 90105, and Pseudomonas fluorescens RG 26. Advancing the sowing date from early spring to winter significantly delayed disease onset, reduced the final disease intensity (amount of disease in a microplot that combines disease incidence and severity, expressed as a percentage of the maximum possible amount of disease in that microplot), and increased chickpea seed yield. A significant linear relationship was found between disease development over time and weather variables at the experimental site, with epidemics developing earlier and faster as mean temperature increased and accumulated rainfall decreased. Under conditions highly conducive for Fusarium wilt development, the degree of disease control depended primarily on choice of sowing date, and to a lesser extent on level of resistance of chickpea genotypes to F. oxysporum f. sp. ciceris race 5, and the biocontrol treatments. The main effects of sowing date, partially resistant genotypes, and biocontrol agents were a reduction in the rate of epidemic development over time, a reduction of disease intensity, and an increase in chickpea seedling emergence, respectively. Chickpea seed yield was influenced by all three factors in the study. The increase in chickpea seed yield was the most consistent effect of the biocontrol agents. However, that effect was primarily influenced by sowing date, which also determined disease development. Effectiveness of biocontrol treatments in disease management was lowest in January sowings, which were least favorable for Fusarium wilt. Sowing in February, which was moderately favorable for wilt development, resulted in the greatest increase in seed yield by the biocontrol agents. In March sowings, which were most conducive for the disease, the biocontrol agents delayed disease onset and increased seedling emergence. B. subtilis GB03 and P. fluorescens RG 26, applied either alone or each in combination with nonpathogenic F. oxysporum Fo 90105, were the most effective treatments at suppressing Fusarium wilt, or delaying disease onset and increasing seed yield, respectively. The importance of integrating existing control practices, partially effective by themselves, with other control measures to achieve appropriate management of Fusarium wilt and increase of seed yield in chickpea in Mediterranean-type environments is demonstrated by the results of this study.

Region-Wide Analysis of Genetic Diversity in Verticillium dahliae Populations Infecting Olive in Southern Spain and Agricultural Factors Influencing the Distribution and Prevalence of Vegetative Compatibility Groups and Pathotypes

Severity of Verticillium wilt in olive trees in Andalusia, southern Spain is associated with the spread of a highly virulent, defoliating (D) Verticillium dahliae pathotype of vegetative compatibility group 1A (VCG1A) but the extent of this spread and the diversity of the pathogen population have never been documented. VCG typing of 637 V. dahliae isolates from 433 trees in 65 orchards from five olive-growing provinces in Andalusia indicated that 78.1% were of VCG1A, 19.8% of VCG2A, 0.6% of VCG2B, 1.4% of VCG4B, and one isolate was heterokaryon self-incompatible. A single VCG prevailed among isolates within most orchards but two and three VCGs were identified in 12 and 3 orchards, respectively, with VCG1A+VCG2A occurring in 10 orchards. VCG1A was the predominant VCG in the three most important olive-growing provinces, and was almost as prevalent as VCG2A in another one. Molecular pathotyping of the 637 isolates using specific polymerase chain reaction assays indicated that VCG1A isolates were of the D pathotype whereas isolates of VCG2A, -2B, and -4B were of the less virulent nondefoliating (ND) pathotype. The pathotype of isolates correlated with the disease syndrome affecting sampled trees. Only three (seq1, seq2, and seq4) of the seven known sequences of the V. dahliae-specific 539- or 523-bp amplicon were identified among the 637 isolates. Distribution and prevalence of VCGs and seq sequences among orchards indicated that genetic diversity within olive V. dahliae in Andalusia is higher in provinces where VCG1A is not prevalent. Log-linear analysis revealed that irrigation management, source of irrigation water, source of planting stock, and cropping history of soil were significantly associated with the prevalence of VCG1A compared with that of VCG2A. Multivariate analyses using a selected set of agricultural factors as variables allowed development of a discriminant model for predicting the occurrence of D and ND pathotypes in the area of the study. Blind tests using this model correctly indentified the V. dahliae pathotype occurring in an orchard. The widespread occurrence and high prevalence of VCG1A/D pathotype in Andalusia have strong implications for the management of the disease.

Spatiotemporal Analysis of Spread of Infections by Verticillium dahliae Pathotypes Within a High Tree Density Olive Orchard in Southern Spain

The development of Verticillium wilt epidemics in olive cv. Arbequina was studied from November 1999 to May 2003 in a drip-irrigated, nontillage orchard established in a soil without a history of the disease at Córdoba, southern Spain. Disease incidence measured at 1-month-intervals increased from 0.2 to 7.8% during this period. Verticillium dahliae infecting the trees was characterized as defoliating (D) or nondefoliating (ND) pathotypes by a specific, multiplex-polymerase chain reaction (PCR) assay. Of the symptomatic trees, 87.2 and 12.8% were infected by the D or ND pathotypes, respectively. Dynamics of disease incidence were described by a generalized logistic model with a multiple sigmoid pattern. In the fitted model, the infection rate was highest in the winter to spring period and decreased to minimum values in the summer to fall period. Binary data of disease incidence was analyzed for point pattern and spatial correlation, either directly or after parsing them in contiguous quadrats. Overall, ordinary runs analysis indicated a departure from randomness of disease within rows. The binomial index of dispersion, interclass correlation, and Taylors power law for various quadrat sizes suggested aggregation of diseased trees within the quadrat sizes tested. Spatial analysis by distance indices showed a nonrandom arrangement of quadrats containing infected trees. Spatial pattern was characterized by the occurrence of several clusters of infected trees. Increasing clustering over time was generally suggested by stronger values of clustering index over time and by the increase in the size of patch clusters. Significant spatial association was found in the clustering of diseased trees over time across cropping seasons; however, clustering was significant only for infections by D V. dahliae, indicating that infections by the D pathotype were aggregated around initial infections. The number and size of clusters of D V. dahliae-infected trees increased over time. Microsatellite-primed PCR assays of a representative number of V. dahliae isolates from diseased trees indicated that the majority of infecting D isolates shared the fingerprinting profile with D V. dahliae isolated from soil of a naturally infested cotton field in close proximity to the orchard, suggesting that short distance dispersal of the pathogen from this soil to the olive orchard may have occurred.

Effect of Sowing Date, Host Cultivar, and Race of Fusarium oxysporum f. sp. ciceris on Development of Fusarium Wilt of Chickpea

ABSTRACT Microplots experiments were carried out at Córdoba, southern Spain, from 1986 to 1989 to determine the effects of sowing date in the management of Fusarium wilt of chickpea as influenced by virulence of the pathogen race and by cultivar susceptibility. A total of 108 epidemics of the disease were described, analyzed, and compared to assess the degree of disease control. The epidemics were characterized by five curve elements: final disease intensity index (DII), standardized area under DII progress curve, time to epidemic onset, time to inflection point (t(ip)), and the DII value at t(ip), the last two parameters being estimates from the Richards function adjusted by nonlinear regression analysis. The structure of Fusarium wilt epidemics was examined by conducting multivariate principal components and cluster analyses. From these analyses, three factors accounting for 98 to 99% of the total variance characterized the DII progress curves and provided plausible epidemiological interpretations. The first factor included the t(ip) and the time to disease onset and can be interpreted as a positional factor over time. This factor accounted for the largest proportion of the total variance and may, therefore, be considered as the main factor for analysis of Fusarium wilt epidemics. The second factor concerns the standardized area under DII progress curves and the final DII of the epidemics. The third factor identified the uniqueness of the estimated value for the point of inflection of the DII progress curve over time. Our results indicate that for each year of experiment epidemic development was related mainly to the date of sowing. Thus, for chickpea crops in southern Spain, advancing the sowing date from early spring to early winter can slow down the development of Fusarium wilt epidemics, delay the epidemic onset, and minimize the final amount of disease. However, the net effect of this disease management practice may also be influenced, though to a lesser extent, by the susceptibility of the chickpea cultivar and the virulence and inoculum density of the Fusarium oxysporum f. sp. ciceris race.

Early Detection and Quantification of Verticillium Wilt in Olive Using Hyperspectral and Thermal Imagery over Large Areas

Automatic methods for an early detection of plant diseases (i.e., visible symptoms at early stages of disease development) using remote sensing are critical for precision crop protection. Verticillium wilt (VW) of olive caused by Verticillium dahliae can be controlled only if detected at early stages of development. Linear discriminant analysis (LDA) and support vector machine (SVM) classification methods were applied to classify V. dahliae severity using remote sensing at large scale. High-resolution thermal and hyperspectral imagery were acquired with a manned platform which flew a 3000-ha commercial olive area. LDA reached an overall accuracy of 59.0% and a κ of 0.487 while SVM obtained a higher overall accuracy, 79.2% with a similar κ, 0.495. However, LDA better classified trees at initial and low severity levels, reaching accuracies of 71.4 and 75.0%, respectively, in comparison with the 14.3% and 40.6% obtained by SVM. Normalized canopy temperature, chlorophyll fluorescence, structural, xanthophyll, chlorophyll, carotenoid and disease indices were found to be the best indicators for early and advanced stage infection by VW. These results demonstrate that the methods developed in other studies at orchard scale are valid for flights in large areas comprising several olive orchards differing in soil and crop management characteristics.

Influence of Inoculum Density of Races 0 and 5 of Fusarium oxysporum f. sp. ciceris on Development of Fusarium Wilt in Chickpea Cultivars

Artificial inoculation experiments were carried out at 25°C to determine the effects of inoculum density of Fusarium oxysporum f.sp. ciceris races 0 (Foc-0) and 5 (Foc-5) and susceptibility of chickpea cultivars P-2245 and PV-61 on development of Fusarium wilt. Foc-5 proved much more virulent than Foc-0. Increasing the inoculum density of F. oxysporum f.sp. ciceris caused an exponential reduction in disease incubation period and a monomolecular increase of disease incidence and the area under the disease intensity progress curve. The extent of these effects was highest in the most conducive ‘P-2245’/Foc-5 combination and decreased in the less susceptible ‘PV-61’ and for the less virulent Foc-0, in that order. For ‘P-2245’/Foc-5, the highest disease intensity was attained with 6 chlamydospores g−1 of soil, the lowest inoculum density in the study. One thousand chlamydospores g−1 of soil of the same race were needed to attain a comparable disease intensity in ‘PV-61’. Twenty thousand chlamydospores g−1 of soil of Foc-0 were required for maximum disease intensity in ‘P-2245’.The disease intensity curves were adequately described by the Gompertz model. Using this model, a response surface for disease intensity was developed, in which the model parameters are expressed as a function of both time from inoculation and inoculum density. This response surface confirmed that the final amount of disease intensity increases in a monomolecular relationship with increasing inoculum density and showed that the relative rate of disease progress increases exponentially with increasing inoculum density of the pathogen.

In Planta and Soil Quantification of Fusarium oxysporum f. sp. ciceris and Evaluation of Fusarium Wilt Resistance in Chickpea with a Newly Developed Quantitative Polymerase Chain Reaction Assay

Fusarium wilt of chickpea caused by Fusarium oxysporum f. sp. ciceris can be managed by risk assessment and use of resistant cultivars. A reliable method for the detection and quantification of F. oxysporum f. sp. ciceris in soil and chickpea tissues would contribute much to implementation of those disease management strategies. In this study, we developed a real-time quantitative polymerase chain reaction (q-PCR) protocol that allows quantifying F. oxysporum f. sp. ciceris DNA down to 1 pg in soil, as well as in the plant root and stem. Use of the q-PCR protocol allowed quantifying as low as 45 colony forming units of F. oxysporum f. sp. ciceris per gram of dry soil from a field plot infested with several races of the pathogen. Moreover, the q-PCR protocol clearly differentiated susceptible from resistant chickpea reactions to the pathogen at 15 days after sowing in artificially infested soil, as well as the degree of virulence between two F. oxysporum f. sp. ciceris races. Also, the protocol detected early asymptomatic root infections and distinguished significant differences in the level of resistance of 12 chickpea cultivars that grew in that same field plot infested with several races of the pathogen. Use of this protocol for fast, reliable, and cost-effective quantification of F. oxysporum f. sp. ciceris in asymptomatic chickpea tissues at early stages of the infection process can be of great value for chickpea breeders and for epidemiological studies in growth chambers, greenhouses and field-scale plots.