Vegetative compatibility and genetic analysis of Colletotrichum lindemuthianum isolates from Brazil

The causal agent of common bean anthracnose, Colletotrichum lindemuthianum, has considerable genetic and pathogenic variability, which makes the development of resistant cultivars difficult. We examined variability within and between Brazilian pathotypes of C. lindemuthianum through the identification of vegetative compatibility groups (VCGs) and by RAPD analysis. Two hundred and ninety-five nit mutants were obtained from 47 isolates of various pathotypes of the fungus collected from different regions, host cultivars and years. In complementation tests, 45 VCGs were identified. Eighteen RAPD primers were employed in the molecular analyses, producing 111 polymorphic bands. Estimates of genetic similarities, determined from the Sorence-Dice coefficient, ranged from 0.42 to 0.97; the dendrogram obtained by cluster analysis revealed 18 groups of isolates. RAPD and VCG markers presented high genotypic diversity. The number of significant associations (P=0.05) between RAPD, VCG and pathogenicity markers ranged from 0 (VCG) to 80% (pathogenicity). The test of multilocus association (rd) for RAPD markers was significantly different from zero (P<0.001), suggesting linkage disequilibrium. However, the results for VCG markers show the presence of recombination mechanisms. In conclusion, RAPD markers and VCGs were useful for detecting genetic variability among isolates of C. lindemuthianum. We found considerable diversity among isolates from the same geographic origin within a short interval; this suggests rapid evolution. There is a need for further studies to elucidate the population structure of this pathogen in agro-ecosystems.     

Pathogenic and genetic variability among Colletotrichum gloeosporioides isolates from different yam hosts in the agroecological zones in Nigeria

Anthracnose, caused by Colletotrichum gloeosporioides Penz., is the most severe foliar disease of water yam (Dioscorea alata) worldwide. Population genetic analyses can yield useful insights into the evolutionary potential of C. gloeosporioides and thus lead to the development of appropriate disease management strategies. The genetic structure of C. gloeosporioides populations from yam and non‐yam hosts in three agroecological zones of Nigeria was investigated. Microsatellite‐primed polymerase chain reaction (MP‐PCR), virulence phenotyping using five putative D. alata differentials, cross‐inoculation tests, and the presence/absence of a Glomerella teleomorph in yam fields were used to infer the evolutionary potential of C. gloeosporioides on yam. We observed high genotypic diversity (GD = 0.99 to 1.00) for populations from all hosts and agroecological zones, with multiple pathogen genotypes in individual anthracnose lesions. Genetic differentiation was low among pathogen populations from different hosts (G_ST = 0.10, θ = 0.034), and agroecological zones (G_ST = 0.04, θ = 0.018), indicating limited host differentiation and significant gene flow. No evidence was found for the existence of C. gloeosporioides f. sp. alatae reported in previous studies. The fungus was recovered from several non‐yam host species commonly found in yam fields but non‐yam isolates caused only mild to moderate symptoms on yam. Eighteen C. gloeosporioides virulence phenotypes were identified among 217 isolates but there was a weak correlation (r = 0.02, P = 0.40) between virulence phenotype and MP‐PCR haplotype. Consistent with the above findings, we observed for the first time the Glomerella teleomorph on anthracnose‐infected yam plants in Nigeria, indicating that sexual recombination might play an important role in anthracnose epidemics on yam. The implications of these findings for C. gloeosporioides evolutionary potential and anthracnose resistance breeding are discussed.     

Synthesis and free radical scavenging activity of a novel metabolite from the fungus Colletotrichum gloeosporioides

A novel metabolite (-)-1 was isolated as its peracetylated derivative, (-)-2-(3',4'-diacetoxyphenyl)-3,4-diacetoxytetrahydrofuran (2), from a strain of the phytopathogenic fungus Colletotrichum gloeosporioides CECT 20122. The synthesis of (-)-1 was carried out by ring-closing metathesis of diene 6 and stereoselective dihydroxylation of a dihydrofuran derivative 7 as key steps. The tetraol (-)-1 showed free radical scavenging activity comparable to that of BHT, caffeic acid or protocatechuic acid.     

Isolation and characterization of a clay-dispersing polysaccharide produced by the phytopathogenic fungus, Colletotrichum gloeosporioides

The fungus, Colletotrichum gloeosporioides, which is pathogenic to peppers produced an extracellular polysaccharide in liquid culture which possessed clay-dispersing activity. The polysaccharide could bind cationic dyes, Ruthenium Red and Alcian Blue, indicating it to be polyanionic. The polysaccharide dispersed kaolin in water and the dispersion was maintained for more than 7 days at 25 °C. Kaolin dispersion by the polysaccharide was stable from pH 3 to 10 but the addition of divalent metals at 1 mM inhibited half of the dispersion activity comparing to the control. The polysaccharide could disperse bentonite, calcium carbonate and other fine particles but did not possess emulsifying activity.     

The genetic diversity and phenotypic characterisation of Streptococcus agalactiae isolates from Rio de Janeiro, Brazil

Streptococcus agalactiae isolates are more common among pregnant women, neonates and nonpregnant adults with underlying diseases compared to other demographic groups. In this study, we evaluate the genetic and phenotypic diversity in S. agalactiae strains from Rio de Janeiro (RJ) that were isolated from asymptomatic carriers. We analysed these S. agalactiae strains using pulsed-field gel electrophoresis (PFGE), serotyping and antimicrobial susceptibility testing, as well as by determining the macrolide resistance phenotype, and detecting the presence of the ermA/B, mefA/E and lnuB genes. The serotypes Ia, II, III and V were the most prevalent serotypes observed. The 60 strains analysed were susceptible to penicillin, vancomycin and levofloxacin. Resistance to clindamycin, chloramphenicol, erythromycin, rifampin and tetracycline was observed. Among the erythromycin and/or clindamycin resistant strains, the ermA, ermB and mefA/E genes were detected and the constitutive macrolides, lincosamides and streptogramin B-type resistance was the most prevalent phenotype observed. The lnuB gene was not detected in any of the strains studied. We found 56 PFGE electrophoretic profiles and only 22 of them were allocated in polymorphism patterns. This work presents data on the genetic diversity and prevalent capsular serotypes among RJ isolates. Approximately 85% of these strains came from pregnant women; therefore, these data may be helpful in developing future prophylaxis and treatment strategies for neonatal syndromes in RJ.     

Dispersal of the conidia of Colletotrichum gloeosporioides by rain and the development of anthracnose on onion

The conidia of Colletotrichum gloeosporioides were found to be dispersed during rainfall by wash-off and splash mechanisms. The initiation and development of onion anthracnose was found to depend on the frequency of rainfall and the movement of conidial inoculum during rainfall. Experiments conducted under controlled conditions in the laboratory employing splash and wash-off assemblies showed that impacting incident water drops (splash) and flowing water (wash-off) liberated the conidia from the anthracnose lesions of the onion leaf/peduncle. Peak liberation of conidia occurred with 3 to 5 water drops and most of the conidia were removed from the source within 90 seconds. A possibility of the dispersal of conidia of C. gloeosporioides from soil to lower leaf by splash mechanisms and then from the leaves to the neck of the onion bulb and to the bulb by wash-off mechanisms is indicated.     

Characterization of Colletotrichum lindemuthianum Isolates from the State of Minas Gerais, Brazil

Anthracnose disease of common bean (Phaseolus vulgaris), caused by Colletotrichum lindemuthianum, is responsible for extensive yield losses worldwide. This pathogen is known to vary greatly in its pathogenicity. Control strategies include chemical control and, mainly, the development of resistant cultivars, taking into account the population structure of C. lindemuthianum. The objective of this study was to investigate the pathogenic and genetic diversity and population structure among C. lindemuthianum isolates collected in Minas Gerais state, Brazil. When these isolates were inoculated on 12 differential cultivars, a total of 10 races were identified within a series of 48 isolates collected in Minas Gerais, Brazil. Races 65, 81 and 73 were the most frequent races and occurred in most of the regions. This study also detected race 337, which had not been reported previously in the literature. Random amplified polymorphic DNA (RAPD) analysis performed on the same 48 isolates revealed great genetic diversity, clustering the series into five groups at a maximum similarity value of 89.6%. There was no clear relationship between the loci sampled by RAPD markers and the pathogenic characterization. Analysis of molecular variance showed that 96.06% of the variability was contained within regions and 3.94% among regions, indicating a high exchange of genetic material among the regions of the State. Most of the variability was detected within races (75.24%). The pathogenicity and RAPD assays corroborated the broad genetic diversity of the pathogen and the results have been useful in breeding for resistance to anthracnose.     

Physiognomic-structural characterization of dry- and humid-forest fragments (Atlantic Coastal Forest) in Pernambuco State,NE Brazil

Although both dry- and humid-forests have been intensively studied, their physiognomic and structural differences have not yet been well characterized. The present work seeks to identify the physiognomic and structural differences between fragments of humid- and dry-forests in the state of Pernambuco, Brazil. The humid-forest fragment was located in the municipality of São Vicente Férrer (7°37′ S × 35°28′ W) and the dry-forest fragment in the municipality of Aliança (7°38′ S × 35°14′ W). Fifty 10 × 20 m plots were delimited in each area and all individual living plants with a diameter at breast height (DBH) ≥5 cm were included. It was observed that the total density (1,390 ind ha^?1) and total basal area (29.9 m² ha^?1) were greater in the humid-forest than the dry-forest (649 ind ha^?1 and 18.7 m² ha^?1, respectively). Individual plants in the humid-forest tended to be taller, while those in the dry-forest had generally larger diameters. There were also differences in the most structurally important families as, for example, Clusiaceae, Moraceae, Myristicaceae, and Sapotaceae in the humid-forest and Sterculiaceae, Fabaceae, Bignoniaceae, and Moraceae in the dry-forest. Physiognomic differences were also observed in the different forest layers, as the group of species composing the canopy of the dry-forest are dominated by deciduous species, while many of the species in the understory are evergreen. In the humid-forest, both the understory and canopy are predominantly composed of evergreen species. The examination of the phytosociological parameters of average height and species richness allowed us to identify physiognomic differences between humid and dry forests in Pernambuco State. The present study demonstrated that dry forests are not simply floristic/structural subsets of humid forests, and that there is a great need to establish conservation areas to protect these important but spatially restricted forests within the Atlantic coastal domain.     

Morphological abnormalities in the cladoceran Ilyocryptus spinifer (Apipucos Reservoir, Pernambuco State, Brazil).

In a sample taken from Apipucos Reservoir (Recife, PE, Brazil) for taxonomic study, a high percentage (40%) was found of cladoceran Ilyocryptus spinifer individuals with morphological abnormalities on their postabdomen. There was not a fixed pattern of the malformations, which varied in gravity, and could affect the postanal spines or terminal claws. The postabdominal abnormalities are described and compared to the ones described in the literature. The hypothesis of the morphological abnormalities being induced by an occasional environmental toxicant is discussed.     

Characterization of Colletotrichum gloeosporioides isolates from avocado and almond fruits with molecular and pathogenicity tests.

One hundred twenty isolates of Colletotrichum gloeosporioides from avocado (6 U.S. and 57 Israeli isolates) and almond (57 Israeli isolates) fruits were compared by various molecular methods and a pathogenicity assay in order to determine the genetic diversity and host specificity between and among the different populations. DNA from eight additional U.S. almond anthracnose isolates were also compared. PCR amplification of genomic DNA with four primers produced uniform banding patterns for all the Israeli almond isolates from different geographic locations in Israel. DNAs from the U.S. almond isolates were distinct from DNAs of the Israeli isolates. In contrast, the avocado isolates from Israel and the United States were more diverse, with numerous arbitrarily primed-PCR phenotypes being observed. HaeIII digestion patterns of A+T-rich DNA distinguished between the almond and avocado isolates. Southern hybridization of the repetitive nuclear-DNA element GcpR1 to PstI-digested genomic DNA of almond and avocado isolates revealed no polymorphic fragments among the almond isolates, whereas polymorphic fragments were observed among the avocado isolates. Amplification and subsequent restriction enzyme digestion of the internal transcribed spacer 4 and 5 regions between the small and large nuclear subunits of DNA encoding rRNA failed to distinguish between C. gloeosporioides isolates from a diverse host range. In artificial inoculations, avocado isolates produced various lesions on avocado and almond fruits, whereas the almond isolates infected both fruits at a lower rate.     

Phylogenetic diversity of endophytic leaf fungus isolates from the medicinal tree Trichilia elegans (Meliaceae)

Various types of organisms, mainly fungi and bacteria, live within vegetal organs and tissues, without causing damage to the plant. These microorganisms, which are called endophytes, can be useful for biological control and plant growth promotion; bioactive compounds from these organisms may have medical and pharmaceutical applications. Trichilia elegans (Meliaceae) is a native tree that grows abundantly in several regions of Brazil. Preparations using the leaves, seeds, bark, and roots of many species of the Meliaceae family have been widely used in traditional medicine, and some members of the Trichilia genus are used in Brazilian popular medicine. We assessed the diversity of endophytic fungi from two wild specimens of T. elegans, collected from a forest remnant, by sequencing ITS1-5.8S-ITS2 of rDNA of the isolates. The fungi were isolated and purified; 97 endophytic fungi were found; they were separated into 17 morpho-groups. Of the 97 endophytic fungi, four genera (Phomopsis, Diaporthe, Dothideomycete, and Cordyceps) with 11 morpho-groups were identified. Phomopsis was the most frequent genus among the identified endophytes. Phylogenetic analysis showed two major clades: Sordariomycetes, which includes three genera, Phomopsis, Diaporthe, and Cordyceps, and the clade Dothideomycetes, which was represented by the order Pleosporales.     

Benthic Bacillariophyta of the Paripe River estuary in Pernambuco State, Brazil.

The aim of this study was to evaluate the benthic diatom composition from the estuary sediment in the Pernambuco State, based on 32 samples. Samples were collected monthly from September through December 1999 (dry period) and from April through July 2000 (rainy period) during four pre established sampling stations. Results indicated 19 families and 31 specific and infraspecific taxa. Eight new records were founded for Pernambuco State: Auliscus coelatus, Fallacia nummularia, Navicula algida, Plagiograma pulchellum, Terpsinoe americana, Triceratium antideluvianna and Tryblionella coarctata and one, Auliscus punctatus Bailey, in northeastern Brazil.     

Frequency of pathogenic enterobacteria in infantile diarrheic processes in the city of Recife, Pernambuco, Brazil

326 samples of diarrheal feces obtained from children whose ages ranged from zero to 5 years, admitted in two rehydration hospitals in the city of Recife, Pernambuco, were analyzed. Feces were placed in Cary-Blair medium (4 degrees C) for shipment to the laboratory. There was no difference in the rate of bacteria isolation if the samples were analyzed within the period from 3 to 7 days of collection. 19.02% of the analyzed samples were positives for at least one of the searched bacteria, 26 Salmonella belonging to 3 species, 21 classic enteropathogenic E. coli, 1 invasive E. coli, 10 Shigella belonging to 3 serotypes and 1 Yersinia enterocolitica were found.