Evaluation of the resistance to two nematodes: Radopholus similis and Meloidogyne spp. in four banana genotypes in Morocco

Radopholus similis and Meloidogyne spp. are the main nematode parasites of banana plants grown under plastic shelters in Morocco. A test was made in pots to evaluate the resistance of four genotypes of banana to these nematodes. Infection by Meloidogyne spp. brought about an increase in root weight in all banana plants tested because of gall formation. The inoculation of R. similis produced a reduction in length and diameter of the pseudo-trunk as well as in root and aerial mass in all genotypes. Pisang jari buaya showed the significantly lowest number of Meloidogyne nematodes per 10 g of roots, whereas for R. similis, the significantly smallest numbers were obtained in Pisang berlin and Pisang jari buaya. Therefore, Pisang jari buaya was the only banana genotype studied to show some degree of resistance to both nematodes.     

Isolation of fluorescent pseudomonads from the rhizosphere of banana plants antagonistic towards root necrosing fungi

Total aerobic bacteria and fluorescent pseudomonads were counted in bulk and rhizospheric soils of banana plants of 14 plantations in Martinique (French West Indies). Fluorescent Pseudomonas isolates were then identified and investigated for in vitro antagonism towards Cylindrocladium sp., a fungal pathogen of banana roots. Total aerobic bacteria and fluorescent pseudomonads were significantly more abundant in rhizospheric soils than in bulk soils. Among 58 fluorescent Pseudomonas isolates, 41 were identified as Pseudomonas fluorescens biovar V and 17 as Ps. putida biovar A. Six strains exhibited an antagonism towards Cylindrocladium isolates. Among them, Ps. putida strain 93.1 totally blocked fungal growth. No relationship was established between the antifungal effect and enzyme or hydrogen cyanide production by bacteria, suggesting that siderophores and other compounds were involved in fungal inhibition. Antagonistic fluorescent pseudomonads represent a potential for the biological control of banana root infections by Cylindrocladium sp.     

Effects of endophytic Fusarium oxysporum towards Radopholus similis activity in absence of banana

Four endophytic fungi (Fusarium spp.) isolated from the cortical tissue of surface-sterilised banana as well as from tomato roots were tested for their capacity of biological control towards the burrowing nematode Radopholus similis on banana. The pathogenic and parasitic capacities of endophytic fungi towards R. similis were tested in in vitro experiments. No parasitism of fungi on R. similis was observed. However, nematode activity decreased significantly in the presence of all endophytic fungi in vitro when compared to nematodes in the absence of fungi. The effects of fungi on R. similis activities in the soil were tested in the absence of plants. Nematode activities were reduced significantly by 16-30% by endophytic fungi when compared to untreated soil.     

Species of Pseudomonas obtained at 7 degrees C and 30 degrees C during aerobic storage of lamb carcasses.

A total of 268 strains of Pseudomonas isolated during storage life of lamb carcasses was identified to species level. One-hundred and thirteen strains obtained at 30 degrees C were Ps. fragi (51), Ps. lundensis (17), Ps. fluorescens biovars I (10), III (9) and VI (1), Ps. putida biovar A (8 strains) and unidentified (17 strains). Species and biovars isolated at 7 degrees C (155) were Ps. fragi (101), Ps. lundensis (32), Ps. fluorescens biovar I (6), Ps. putida biovar A (8) and unidentified (8). Numerical analysis (82% SSM, UPGMA) of 'psychrotrophic' and 'mesophilic' strains resulted in the formation of nine and eight clusters respectively. The dendrograms obtained exhibited similar structures. Most of the strains of Ps. lundensis and Ps. fragi clustered together. Strains of this latter species also joined the type strain of Ps. testosteroni and appeared included with phenons containing the Ps. putida strains. There were clusters made up exclusively of strains assigned to one biovar or group (Ps. fluorescens biovars I and II and unidentified). A high level of similarity was observed between clusters of Ps. fluorescens biovar I and those containing the Ps. fragi-Ps. lundensis complex (> 74% SSM) and Ps. lundensis (> 80%). The recovery of pseudomonads seemed to be affected by the sampling day.     

Species of Pseudomonas obtained at 7°C and 30°C during aerobic storage of lamb carcasses

A total of 268 strains of Pseudomonas isolated during storage life of lamb carcasses was identified to species level. One-hundred and thirteen strains obtained at 30°C were Ps.fragi (51), Ps. lundensis (17), Ps. fluorescens biovars I (10), III (9) and VI (1), Ps. putida biovar A (8 strains) and unidentified (17 strains). Species and biovars isolated at 7°C (155) were Ps. fragi (101), Ps. lundensis (32), Ps. fluorescens biovar I (6), Ps. putida biovar A (8) and unidentified (8). Numerical analysis (82% S _SM, UPGMA) of 'psychrotrophic' and 'mesophilic' strains resulted in the formation of nine and eight clusters respectively. The dendrograms obtained exhibited similar structures. Most of the strains of Ps. lundensis and Ps. fragi clustered together. Strains of this latter species also joined the type strain of Ps. testosteroni and appeared included with phenons containing the Ps. putida strains. There were clusters made up exclusively of strains assigned to one biovar or group ( Ps. fluorescens biovars I and II and unidentified). A high level of similarity was observed between clusters of Ps. fluorescens biovar I and those containing the Ps. fragi-Ps. lundensis complex (>74% S _SM) and Ps. lundensis (>80%). The recovery of pseudomonads seemed to be affected by the sampling day.     

Evaluation of an Antibiotic-Producing Strain of Pseudomonas fluorescens for Suppression of Plant-Parasitic Nematodes

The antibiotic 2,4-diacetylphloroglucinol (DAPG), produced by some strains of Pseudomonas spp., is involved in suppression of several fungal root pathogens as well as plant-parasitic nematodes. The primary objective of this study was to determine whether Wood1R, a D-genotype strain of DAPG-producing P. fluorescens, suppresses numbers of both sedentary and migratory plant-parasitic nematodes. An experiment was conducted in steam-heated soil and included two seed treatments (with Wood1R and a control without the bacterium) and six plant-nematode combinations which were Meloidogyne incognita on cotton, corn, and soybean; M. arenaria on peanut; Heterodera glycines on soybean; and Paratrichodorus minor on corn. Wood 1R had no effect on final numbers of M. arenaria, P. minor, or H. glycines; however, final numbers of M. incognita were lower when seeds were treated with Wood1R than left untreated, and this reduction was consistent among host plants. Population densities of Wood1R were greater on the roots of corn than on the other crops, and the bacterium was most effective in suppressing M. incognita on corn, with an average reduction of 41%. Despite high population densities of Wood1R on corn, the bacterium was not able to suppress numbers of P. minor. When comparing the suppression of M. incognita on corn in natural and steam-heated soil, egg production by the nematode was suppressed in natural compared to steamed soil, but the presence of Wood1R did not result in additional suppression of the nematodes in the natural soil. These data indicate that P. fluorescens strain Wood1R has the capacity to inhibit some populations of plant-parasitic nematodes. However, consistent suppression of nematodes in natural soils seems unlikely.     

A study of the incidence of different fluorescent Pseudomonas species and biovars in the microflora of fresh and spoiled meat and fish, raw milk, cheese, soil and water

M. GENNARI AND F. DRAGOTTO. 1992. Of 182 various foodstuffs and environmental samples examined, 86% had microflora containing fluorescent Pseudomonas in differing proportions. A computer-aided technique was used to identify most of the 445 fluorescent strains. Pseudomonas fluorescens biovar V-1 was most frequently isolated (24%); it either predominated or was present in all types of samples. Other strains, belonging to the other subgroups of biovar V (V-2, V-4, V-5, V-6 and V-7), together represented 14.3%. We also identified Ps. fluorescens biovars I-1 and I-2 (13.9%), II-1 and II-3 (3.6%), III-1 and III-2 (8.7%), IV-2 (0.7%); Ps. putida A and B (11%); Ps. lundensis (10.3%); group B3 (2%) and Ps. aeruginosa (0.7%). Unidentified strains accounted for 10.6% of the flora, many resembling Ps. fluorescens biovar V. Although the presence of Ps. fluorescens V-1 was often marked, other taxa predominated or were present in large quantities in some particular samples, such as Ps. fluorescens I-1 in raw milk and cheese, Ps. lundensis in spoiled meat and Ps. fluorescens III-1 in spoiled fish. Pseudomonas putida A and B were evident in environmental rather than in food samples.     

A study of the incidence of different fluorescent Pseudomonas species and biovars in the microflora of fresh and spoiled meat and fish, raw milk, cheese, soil and water.

Of 182 various foodstuffs and environmental samples examined, 86% had microflora containing fluorescent Pseudomonas in differing proportions. A computer-aided technique was used to identify most of the 445 fluorescent strains. Pseudomonas fluorescens biovar V-1 was most frequently isolated (24%); it either predominated or was present in all types of samples. Other strains, belonging to the other subgroups of biovar V (V-2, V-4, V-5, V-6 and V-7), together represented 14.3%. We also identified Ps. fluorescens biovars I-1 and I-2 (13.9%), II-1 and II-3 (3.6%), III-1 and III-2 (8.7%), IV-2 (0.7%); Ps. putida A and B (11%); Ps. lundensis (10.3%); group B3 (2%) and Ps. aeruginosa (0.7%). Unidentified strains accounted for 10.6% of the flora, many resembling Ps. fluorescens biovar V. Although the presence of Ps. fluorescens V-1 was often marked, other taxa predominated or were present in large quantities in some particular samples, such as Ps. fluorescens I-1 in raw milk and cheese, Ps. lundensis in spoiled meat and Ps. fluorescens III-1 in spoiled fish. Pseudomonas putida A and B were evident in environmental rather than in food samples.     

A study of the relative incidence of different Pseudomonas groups on meat using a computer-assisted identification technique employing only carbon source tests

A computer-assisted probabilistic identification technique employing 18 carbon source utilization tests has been developed and applied to 787 Pseudomonas strains isolated from beef, pork and lamb stored under aerobic conditions. Seven hundred and twelve (89.7%) were identified using these tests alone and a further six (0.8%) with extra tests. Taxa detected were Ps. fragi cluster 2, 390 strains (49.6% of all isolates); Ps. fragi cluster 1, 191 strains (24.9%); meat cluster 3, 87 strains (11.1%); Ps. fluorescens biotype I, 31 strains (3.9%); Ps. fluorescens biotype III, 7 strains (0.9%); and Ps. putida , 1 strain (0.1%). The relative incidence of members of the various taxa was similar on beef, pork and lamb, and was unaffected by storage temperature in the range 0°–10°C. Each taxon was also detected at similar rates before and after spoilage. Meat origin (abattoir) affected the frequency of detection of meat cluster 3 and Ps. fluorescens biotype I strains but did not affect the incidence of detection of either cluster of Ps. fragi.     

A study of the relative incidence of different Pseudomonas groups on meat using a computer-assisted identification technique employing only carbon source tests

A computer-assisted probabilistic identification technique employing 18 carbon source utilization tests has been developed and applied to 787 Pseudomonas strains isolated from beef, pork and lamb stored under aerobic conditions. Seven hundred and twelve (89.7%) were identified using these tests alone and a further six (0.8%) with extra tests. Taxa detected were Ps. fragi cluster 2, 390 strains (49.6% of all isolates); Ps. fragi cluster 1, 191 strains (24.9%); meat cluster 3, 87 strains (11.1%); Ps. fluorescens biotype I, 31 strains (3.9%); Ps. fluorescens biotype III, 7 strains (0.9%); and Ps. putida, 1 strain (0.1%). The relative incidence of members of the various taxa was similar on beef, pork and lamb, and was unaffected by storage temperature in the range 0 degrees-10 degrees C. Each taxon was also detected at similar rates before and after spoilage. Meat origin (abattoir) affected the frequency of detection of meat cluster 3 and Ps. fluorescens biotype I strains but did not affect the incidence of detection of either cluster of Ps. fragi.     

Plant mediated interactions between Pseudomonas fluorescens, Rhizobium leguminosarum and arbuscular mycorrhizae on pea

Using undisturbed sandy loam soil cores heavily infested with mycorrhizae, the effects of the antibiotic-producing Pseudomonas fluorescens strain F113 and its non-antibiotic derivative Ps. fluorescens F113G22 on nodulation by introduced and indigenous Rhizobium were studied. Furthermore, the effects of the different microbial inocula on the colonization of the pea roots by mycorrhizae were studied. It was found that Ps. fluorescens F113 enhanced nodulation by Rhizobium fourfold, while the nodules produced were much larger and strongly pigmented (pink) compared with those in other treatments. The proportion of roots colonized by arbuscular mycorrhizae was not significantly affected by the different treatments.     

Numerical systematics of bacteria of the genus Pseudomonas

In 290 strains of bacteria belonging to the genus Pseudomonas, 120 morphological and physiologo-biochemical characters were studied and the results obtained thereby were analyzed by the methods of numerical taxonomy using computers. The majority of strains were subdivided into 11 clusters: Ps. aeruginosa (1), Ps. putida (2), Ps. rathonis (5), Ps. syringae (8), Ps. pseudoalcaligenes (9), Ps. maltophilia (10), Ps. acidovorans (11), Ps. testosteroni (12), Ps. mendocina (13), Ps. cepacia (14), Ps. fluorescens (3). The latter cluster included also the strains identified earlier as Ps. aurantiaca, Ps. lemonnieri, Ps. fluoro-violaceus, and Ps. aureofaciens. Three clusters contained strains which could not be identified and probably should be regarded as distinct species. The characteristics have been selected useful for diagnostics of the above Pseudomonas bacteria and the subgroups of Ps. fluorescens.     

Efficacy of Paecilomyces lilacinus (strain 251) for the control of Radopholus similis in banana

Paecilomyces lilacinus is a common soil fungus that has been isolated from many different habitats around the world. It is well known as a facultative egg pathogen of sedentary nematodes and also an important option to control Radopholus similis juvenile and adults in banana. This nematode antagonistic fungus may be used in an integrated approach to control banana plant parasitic nematodes. Dose response and form of application experiments were conducted with burrowing nematode, R. similis, on banana using a commercial water dispersible granulate formulated P. lilacinus (strain 251) product. The results revealed that nematode activity decreased in the presence of this fungus. An important correlation between rates of application and the degree of control of R. simnilis penetration and banana root weight was observed. The best control was achieved in the treatment were plantlets and soil were pre-inoculated with P. lilacinus and reinoculated during transplantation. The results showed that the biocontrol agent P. lilacinus is an excellent candidate for an IPM program against nematodes such as Radopholus similis.     

Zinc and glycerol enhance the production of nematicidal compounds in vitro and improve the biocontrol of Meloidogyne javanica in tomato by fluorescent pseudomonads

AIMS: To assess the effects of various carbon and mineral sources on the nematicidal potential of biocontrol inoculants of Pseudomonas aeruginosa IE-6S+ and Ps. fluorescens CHA0 under laboratory and glasshouse conditions. METHODS AND RESULTS: Culture filtrates of strains IE-6S+ and CHA0, cultured in nutrient yeast extract broth, caused substantial mortality of the juveniles of Meloidogyne javanica. The nematicidal activities of the culture filtrates were altered after amendment with various carbon and mineral sources. Soil amendment with zinc alone or in combination with glycerol improved the biocontrol efficacy against root-knot nematode, promoted tomato plant growth and enhanced bacterial rhizosphere and endophytic colonization. CONCLUSIONS: Appropriate quantities of glycerol and zinc alone or in combination enhance the nematicidal activity of Ps. aeruginosa and Ps. fluorescens. Glucose reduces the activity of these bacteria against nematodes. SIGNIFICANCE AND IMPACT OF THE STUDY: Minerals and carbon sources are appealing because they are easy and economical to provide during liquid fermentation of inoculants or as fertilizer amendments to improve the biocontrol activity of indigenous and introduced bacteria.     

Growth of lipolytic psychrotrophic pseudomonads in raw and ultra-heat-treated milk

The lipolytic floras of 36 raw milk samples showing lipolytic defects were dominated by pseudomonads. Representative lipolytic isolates were selected and tested for growth, lipase activity and lipolysis in ultra-heat-treated milk at temperatures ranging from 5 degrees to 30 degrees C. Pseudomonas fluorescens was the most frequently encountered species but Ps. fragi was found to cause more severe lipolytic defects in both single and mixed strain milk cultures. A representative strain of Ps. fragi multiplied faster in cold-stored milk than did three representative strains of Ps. fluorescens. The lipases produced by Ps. fragi strains were more heat-stable than those produced by Ps. fluorescens strains.     

Selection of pH buffers for use in conductimetric microbiological assays

The lipolytic floras of 36 raw milk samples showing lipolytic defects were dominated by pseudomonads. Representative lipolytic isolates were selected and tested for growth, lipase activity and lipolysis in ultra-heat-treated milk at temperatures ranging from 5° to 30°C. Pseudomonas fluorescens was the most frequently encountered species but Ps. fragi was found to cause more severe lipolytic defects in both single and mixed strain milk cultures. A representative strain of Ps. fragi multiplied faster in cold-stored milk than did three representative strains of Ps. fluorescens. The lipases produced by Ps. fragi strains were more heat-stable than those produced by Ps. fluorescens strains.     

Classification of the spoilage flora of fish, with special reference to Shewanella putrefaciens

One hundred and fifty-nine Gram-negative strains isolated from refrigerated fish, taken from the Baltic Sea or Swedish inland waters, together with 32 reference strains of Shewanella, Pseudomonas, Aeromonas and Alcaligenes, were phenotypically classified using 124 unit characters. Data were processed by the Simple Matching (SSM) and Jaccard (SJ) coefficients, and unweighted pair group algorithm with arithmetic averages. Fourteen clusters were defined at the 75% SJ similarity level which correspond to the SSM level of 86%. SJ-based clusters containing field strains were designated Pseudomonas fragi (cluster 1; 31% of the field strains), Ps. lundensis (cluster 2; 2% of the field strains), Ps. fluorescens biovar III (cluster 4; 4% of the field strains), Ps. putida biovar A (cluster 5; 3% of the field strains), Ps. fluorescens/putida (clusters 3 and 6; 6% of the field strains), Psychrobacter (clusters 8 and 9; 3% of the field strains), Shewanella putrefaciens (clusters 10, 11, 12 and 13; 44% of the field strains) and Aer. sobria (cluster 14; 6% of the field strains, all isolated from fresh water fish). Each field strain represented the spoilage flora of refrigerated fish at a total aerobic count of about 10(8) cfu/g. Phenotypic characteristics of major clusters are given. The four S. putrefaciens clusters may be separated by key characteristics. Shewanella putrefaciens ATCC 8071T and reference strains from sources other than fish, did not group in any of the clusters. The mol % guanine + cytosine content was on average 47.6 for cluster 10, and 45.3 for cluster 13.     

Measuring the spermosphere colonizing capacity (spermosphere competence) of bacterial inoculants

Spermosphere establishment by bacteria which were coated onto seeds was studied using soybean seeds treated with four bacterial strains at levels of log10 1 to 4 colony-forming units (cfu) per seed planted in a field soil mix, and incubated 48 h. Each strain at every inoculum level developed spermosphere population densities of log10 4 to 8 cfu/seed, demonstrating an average multiplication of log10 3 cfu/seed. An alternative method was developed to differentially rank bacteria for spermosphere colonizing capacity, based upon incorporation of bacteria into a soil and monitoring the resulting spermosphere population densities around noninoculated seeds after 4 days at 14 degrees C. Fifty-seven bacterial strains which were isolated from soybean roots or from water samples, including Pseudomonas putida, P. putida biovar B, P. fluorescens, Serratia liquefaciens, Enterobacter aerogenes, and Bacillus spp. were tested in the spermosphere colonization assay. Average spermosphere population densities for the 57 strains ranged from 0 to log10 7.0 cfu/seed. Strains of a given taxon demonstrated marked diversity with ranges from 0 to log10 6.0 cfu/seed for Bacillus spp. and from log10 1.4 to 7.0 cfu/seed for Pseudomonas putida. The relative ranking of representative strains was consistent in repeating experiments. The potential usefulness of the assay for efforts to develop competitive bacterial inoculants for crop seeds is discussed.     

相似穿孔线虫拮抗细菌的筛选及分子鉴定

【背景】相似穿孔线虫是一种重要的检疫性有害生物,其寄主范围广,危害具有毁灭性,已给我国农业生产造成潜在威胁。由于目前大多化学杀线剂毒性较高,筛选获得对相似穿孔线虫具有拮抗活性的微生物菌株对线虫防控具有重要意义。【方法】广泛从染病香蕉植株根际采集土壤样本,运用等比稀释涂布平板法分离菌株;采用摇瓶发酵法制备拮抗菌株上清液和发酵液。通过室内生物测定和盆栽试验,筛选出对相似穿孔线虫具有拮抗作用的细菌菌株,并通过16S rDNA的PCR扩增和序列分析,对拮抗菌株进行种类鉴定。【结果】获得5株对相似穿孔线虫具有较理想拮抗活性的细菌菌株。其中,菌株HD-86的作用效果最好,其发酵上清液处理24 h后的相似穿孔线虫死亡率达100%。盆栽试验表明,菌株HD-86发酵液处理42和70 d后对相似穿孔线虫的相对防效分别为77.34%和90.51%,均优于对照药剂阿维菌素。【结论与意义】菌株HD-86对相似穿孔线虫具有很强的拮抗作用,将其鉴定为洋葱伯克氏菌Burkholderia cepacia。本研究可为相似穿孔线虫生防制剂的研发和病害的防控提供依据。     

Identification of Pseudomonas spp. Isolated from Milk Produced in South Eastern Queensland

S ummary . Bacteria were isolated from raw and pasteurized milks produced throughout S. E. Queensland. Milk samples were plated initially on penicillin agar or on milk agar and incubated at 30° and 7°, respectively. On the basis of primary characterization, 167 of the 330 isolates obtained were identified as Pseudomonas spp. The pseudomonads were further characterized in accordance with the taxonomic studies of the genus by Stanier, Palleroni & Doudoroff (1966). Species designations were ascribed to the Pseudomonas isolates on the basis of distinctive species characteristics in conjunction with similarity coefficients between each isolate and the ideal species phenotype, as follows: Ps. fluorescens (121), Ps. aeruginosa (16), Ps. putida (12), Ps. maltophilia (9), Ps. pseudoalcaligenes (5), Ps. cepacia (3) and Ps. alcaligenes (1). A dendrogram obtained by cluster analysis of the Pseudomonas isolates is included.