Chondrostereum purpureum and Fusarium tumidum independently reduce regrowth in gorse (Ulex europaeus)

An experiment was conducted in two gorse populations (Ulex europaeus) in which Chondrostereum purpureum was applied each month as mycelial-agar cultures to the wounds of decapitated stems of previously untreated gorse plants to determine its potential as a mycoherbicide. Summer-autumn (Feb-May) or late winter-early spring (Aug-Sept) applications were effective in both populations, halving stem stump survival (from an average of 56 to 29%). Another experiment in the same gorse populations evaluated the combined effects of C. purpureum applied in May to decapitated stems, and Fusarium tumidum applied as spores in an invert emulsion to regenerative shoots 5-6 months later. There was no evidence of synergism between the two fungi; each pathogen independently reduced the density of regenerative shoots on the decapitated stems by 39-63% averaged over the 12 months following their respective applications. It is concluded that both pathogens have potential as mycoherbicides for gorse regenerating after stem decapitation.     

Chromosome numbers and geographical distribution of Ulex europaeus subsp. europaeus (Leguminosae)

FERNANDEZ PRIETO, J. A., VERA, M. L., ALVAREZ MARTINEZ, M. J., DIAZ, T. E., FERNANDEZ CASADO, M. A., FERNANDEZ-CARVAJAL, M. C, GUTIERREZ VILLARIAS, M. I. & NAVA, H. S., 1993. Chromosome numbers and geographical distribution of Ulex europaeus subsp. europaeus (Leguminosae). Chromosome numbers are reported in Ulex europaeus subsp. europaeus (99 samples from northern Spain, France and Great Britain). Three levels of ploidy (diploid, tetraploid and hexaploid) have been detected; the diploid and tetraploid levels, hitherto unknown in this taxon, have been found exclusively in coastal areas of northern Spain and western France.     

Favourable Conditions for the Bioherbicide Candidate Fusarium tumidum to Infect and Cause Severe Disease on Gorse (Ulex europaeus) in a Controlled Environment

The development of the pathogenic fungus Fusarium tumidum on gorse ( Ulex europaeus ), a major weed of pastures and plantation forests in New Zealand, was studied under controlled conditions. F. tumidum , like most other foliar fungal pathogens, requires moisture to infect plants. Long, continuous dew periods ( 24 h) after inoculation of plants provided favourable conditions for infection. The fungus, however, also caused severe disease on young plants (2 months old) exposed to two or three 12-h dew periods interrupted by 12-h dry periods. A delay of 24 h before inoculated plants were exposed to dew did not affect the severity of the disease. F. tumidum infected plants over a wide range of temperatures (5-27IC), but more plants were killed as temperatures increased during the initial infection phase. All gorse plants tested (up to 4 months old) were susceptible to the fungus, but younger plants were more easily killed. Nevertheless, the biomass of older plants that were severely diseased but not killed by the fungus was significantly reduced. The effectiveness of F. tumidum in killing plants increased with the density of inoculum sprayed. The fungus applied at a density of 1 106 conidia/ml killed more than 95% of 1.5-month-old plants. This basic knowledge of the F. tumidum -gorse system will assist in the development of a pilot bioherbicide to control gorse and broom ( Cytisus scoparius ), another economically important weed in New Zealand which is also susceptible to the fungus.     

Suppressiveness of Vermicompost against Fusarium Wilt of Tomato

Vermicompost added to various container media significantly inhibited the infection of tomato plants by Fusarium oxysporum f. sp. lycopersici. The protective effect increased in proportion to the rate of application of vermicompost. Every type of container media amended with this substrate, used in the experiments, were suppressive to the pathogen. Vermicompost lost its activity after heating. Sterilized extracts of vermicompost added to potato dextrose agar stimulated the growth of F. oxysporum mycelium. The results indicate that chemical factors in this substrate had no direct inhibiting effect on the fungus. The total number of micro-organisms and populations of antagonistic bacteria and fungi were significantly higher in vermicompost than in the control peat substrate. A biotic nature is suggested for the suppressiveness of the vermicompost.     

Preservation, mass production and storage ofStagonospora convolvuli, a bioherbicidecandidate for field bindweed (Convolvulusarvensis)

Different solid substrates were investigated as spore production methods for Stagonospora convolvulistrain LA39, a potential bioherbicide for field bindweed (Convolvulusarvensis L.). Up to 4 × 10⁸ spores/g of substratewere yielded on cous-cous (cracked hard wheat). Thespores were as pathogenic as those grown on artificial medium (V-8-juice agar). The air-drying on kaolin and storage at 3 °C kept spores viable and pathogenic for 180 days. Spore germination exceeded70% for the first 140 days and then declined to 50%after 175 days. Less than 5% of spores were still viable after 17 months. The preservation of stock cultures in 10% glycerine at −80 ° C and in liquid nitrogen did not affect viability orpathogenicity of the spores. This revised version was published online in July 2006 with corrections to the Cover Date.     

Two granular formulations of Fusarium oxysporum f.sp. orthoceras to mitigate sunflower broomrape Orobanche cumana

Fusarium oxysporum Schlecht. f.sp. orthoceras (Appel & Wollenw.) Bilai, a potential biocontrol agent against Orobanche cumana Wallr.,was formulated into two granular forms, wheatflour kaolin (`Pesta') granules and sodium alginatepellets. The formulations were compared in terms ofeffectiveness for mitigating O. cumanaparasitism in sunflower and shelf-life forstorage. `Pesta' granules reduced the emergence of O. cumana shoots by 64% while sodium alginatepellets did not reduce the emergence rate but increased thepercentage of diseased O. cumana plants.Calculated efficacy of the application was better for`Pesta' granules. Viability of the formulatedmaterial tested in the laboratory was higher in sodium alginatepellets than in the `Pesta' formulation.However, a loss of virulence after six months of storage wasalso observed in sodium alginate pellets in agreenhouse experiment.     

Optimization of storage conditions for adequate shelf-life of 'pesta' formulation of Fusarium oxysporum 'foxy 2', a potential mycoherbicide for Striga: Effects of temperature, granule size and water activity

An adequate shelf-life of mycoherbicidial products is an essential requirement for their acceptance and commercialization. Therefore, attempts were made to study the effects of temperature, granule size, and water activity (R.H./100) on the viability of the encapsulated propagules of Fusarium oxysporum 'Foxy 2' in 'Pesta' granules during storage. 'Pesta' granules were made with different inocula of Foxy 2, including: microconidia; mixture of mycelia and microconidia; fresh and dried chlamydospore-rich biomass. Two sizes of each granular preparation (0.5-2 and 0.25-0.5 mm) were stored in the refrigerator at 4°C as well as at room temperature (21±3°C) for 1 year. Additional samples were also stored at water activities (a_w) of 0.12 and 0.41 at 25°C. Regardless of the type of formulated propagules and the granule size, all samples stored at 4°C maintained a significantly higher viability compared to those kept under room temperature. At 4°C, the 'Pesta' preparations with the larger granule size (0.5-2 mm) maintained more viable propagules than those with the smaller one (0.25-0.5 mm) in case of microconidia, mycelia plus microconidia and fresh chlamydospore inoculum after 1 year of storage. Granule size did not affect the viability of the dried chlamydospores. At 25°C, shelf-life of all 'Pesta' granules was significantly prolonged when stored at a low water activity of 0.12 compared to the storage at 0.41 a_w. The results of the combined effect of water activity and temperature also revealed clearly that all formulated propagules in 'Pesta' granules retained a significantly higher viability when stored at 0.62 a_w and 4°C than at 0.12 a_w and 25°C, indicating the most pronounced effect of storage temperature.     

The effect of varying rates of glyphosate and an organosilicone surfactant on the control of gorse

The herbicidal effect of glyphosate applied to gorse (Ulex europaeus L.) was improved by the addition of increasing amounts (0.5–20 g/litre) of Silwet L-77, an organosilicone surfactant. Increasing the rate of herbicide also enhanced control. There was a highly significant interaction between surfactant rate and herbicide dosage; as the amount of Silwet L-77 was increased the rate of glyphosate could be reduced without loss of herbicide efficacy. However, without any added organosilicone surfactant, glyphosate did not provide more than 73% control of gorse at any rate up to 6.5 kg a.i./ha. With the addition of Silwet L-77, complete mortality of all plants could be achieved with 2.2 kg glyphosate/ ha.     

Fusarium oxysporum and post-emergence herbicide for the control of the parasitic plant Striga hermonthica in maize

Two trials were conducted to evaluate the efficacy of a granular mycoherbicide formulation based on Fusarium oxysporum and post-emergence herbicide for the control of the parasitic plant, Striga hermonthica in the Nigerian Savanna. Four fungal treatments were used: F. oxysporum followed by 2,4-D, F. oxysporum followed by supplementary hoe weeding, F. oxysporum followed by Triclopyr and a control (No F. oxysporum but hoe-weeded). The experiments were laid out in a split plot design with three replications in the two locations. The two varieties (Across 97 TZL and farmer's local variety) formed the main plot treatments, while the Striga fungal treatments formed the sub-plot treatments. At the Lafia location, the emergence of Striga was delayed by 7 days (46 days) as compared to the Makurdi location, which germinated earlier 39 days after sowing. Maize variety Across 97 TZL similarly delayed the time to Striga emergence when compared to the farmer's local variety. However, the different Striga control methods did not have any significant effect on the time of Striga emergence. Generally, number of maize plants infected with Striga was highest with the farmer's local variety throughout the period of observation, while in the Striga control treatments, hoe-weeded check recorded the highest; the minimum was obtained with plots treated with F. oxysporum followed by postemergence application of Triclopyr at the rate of 0.36 kg a.i./ha at 6 weeks after sowing. Highest maize grain yields were obtained at Lafia with Across 97 TZL and plots treated with F. oxysporum followed by either post-emergence 2,4-D or Triclopyr at 0.36 kg a.i./ha each. The results demonstrate the high potentiality of using F. oxysporum as a spot application at planting followed by post-emergence herbicide (2,4-D or Triclopyr) application at 6 weeks after sowing for the control of the parasitic plant S. hermonthica in the Nigerian Savanna.     

Field assessment of <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> based mycoherbicide for control of <Emphasis Type="Italic">Striga hermonthica</Emphasis> in Nigeria

Fusarium oxysporum (isolate PSM 197) based mycoherbicide was evaluated for its efficacy under field conditions in trials conducted during 1999--2001 cropping seasons in the Nigerian savanna. In the 1999 cropping season, spot application of 5--10 g of mycoherbicide was found to give effective control of Striga hermonthica. Results of on-farm trials at Barhim and Dutsen-Ma areas showed the application of the mycoherbicide to significantly (p= 0.05) increase stand count at both 3 weeks and at harvest, reduced Striga shoot count and increased crop yield in both improved and local sorghum varieties, as compared with the same varieties not treated with the mycoherbicide. Results establish the efficacy of F. oxysporum as a mycoherbicide and the need for further development of the mycoherbicide into formulated granules or seed treatment for use in control of S. hermonthica under field conditions.     

Studies on the population dynamics and integrated management of Fusarium oxysporum f. sp. psidi (Fop), a cause of guava (Psidium guajava) wilt

To assess the impact of non-host crops intercropping, bioagents and oil cakes, on population dynamics of Fusarium oxysporum f. sp. psidii (Fop) and wilt of guava. Lowest population of Fop was recorded in garlic followed by intercropping with marigold with reduction of 84.9 and 83.9%, respectively. Bioagents viz; Aspergillus niger, Trichoderma viride and Trichoderma harzianum reduced the Fop population significantly, with the lowest in T. harzianum followed by A. niger. Garlic bulb extract exhibited maximum inhibition of Fop growth (2.7 cm) followed by marigold (2.4 cm), respectively, over control. Neem cake significantly reduced population of Fop, closely followed by mahua cake, over control. Integration of neem cake + T. harzianum + garlic reduced the Fop population significantly, over control, followed by neem cake + T. harzianum + marigold but neem cake + T. harzianum + marigold reduced wilt disease significantly in comparison to neem cake + T. harzianum + garlic inter-cropping.     

Variation in pathogenicity of Fusarium verticillioides and resistance of maize genotypes to Fusarium ear rot

Abstract

The ineffective control measures of pathogens is due to variability among their populations. Hence, the study of pathogenic variation of Fusarium verticillioides strains on maize genotypes. Six F. verticillioides infected maize ear were randomly obtained from three agro-ecological zones in Southwest Nigeria. Pathogenicity of F. verticillioides strains at 1.0?×?10⁶ spores/mL were examined in vivo based on the rating scale of 1–7 on maize genotypes T2L COMP.1.STR SYN-W-1, PVA SYN 8F2, and T2L COMP.4. The pathogens were inoculated to the maize genotypes on 8th week for disease severity and were all moderately susceptible, however, genotype T2L COMP.4 was the most susceptible. It was observed that, 9.4% were classified as highly virulent, 12.5% as virulent, 37.5% as moderately virulent, 21.8% as slightly virulent, and 18.8% as non-virulent. In all, Fusarium verticillioides strains displayed different degrees of virulence, however, maize genotype T2L COMP.4 was the most susceptible to ear rot.     

Influence of Plant Root Exudates, Germ Tube Orientation and Passive Conidia Transport on Biological Control of Fusarium Wilt by Strains of Nonpathogenic Fusarium oxysporum

In earlier studies, biological control of Fusarium wilt of cucumber induced by Fusarium oxysporum f. sp. cucumerinum was demonstrated using nonpathogenic strains C5 and C14 of Fusarium oxysporum. Strain C14 induced resistance and competed for infection sites whether roots were wounded or intact, whereas strain C5 required wounds to achieve biocontrol. In the current work, additional attributes involved in enhanced resistance by nonpathogenic biocontrol agents strains to Fusarium wilt of cucumber and pea were further investigated. In pre-penetration assays, pathogenic formae specials exhibited a significantly higher percentage of spore germination in 4-day-old root exudates of cucumber and pea than nonpathogens. Also, strain C5 exhibited the lowest significant reduction in spore germination in contrast to strain C14 or control. One-day-old cucumber roots injected with strain C14 resulted in significant reduction in germ tube orientation towards the root surface, 48–96 h after inoculation with F. o. cucumerinum spores, whereas strain C5 induced significantly lower spore orientation of the pathogen and only at 72 and 96 h after inoculation. In post-penetration tests, passive transport of microconidia of pathogenic and nonpathogens in stems from base to apex were examined when severed plant roots were immersed in spore suspension. In repeated trials, strain C5, F. o. cucumerinum and F. o. pisi were consistently isolated from stem tissues of both cucumber and pea at increasing heights over a 17 days incubation period. Strain C14 however, was recovered at a maximum translocation distance of 4.6 cm at day 6 and later height of isolation significantly declined thereafter to 1.2 cm at day 17. In pea stem, the decline was even less. Significant induction of resistance to challenge inoculation by the pathogen in cucumber occurred 72 and 96 h after pre-inoculation with biocontrol agents. Nonetheless, strain C14 induced protection as early as 48 h and the maximum resistance was reached at 96 h. The presented data confirm the previous findings that attributes important for nonpathogenic fusaria to induce resistant are: rapid spore germination and orientation in response to root exudate; active root penetration and passive conidia transport in stem to initiate defence reaction without pathogenicity and enough lag period between induction and challenge inoculation. Strain C14 possesses all these qualifications and hence its ability to enhance host resistance is superior than strain C5.     

Ulex europaeus agglutinin II (UEA-II) is a novel, potent inhibitor of complement activation

Complement is an important mediator of vascular injury following oxidative stress. We recently demonstrated that complement activation following endothelial oxidative stress is mediated by mannose-binding lectin (MBL) and activation of the lectin complement pathway. Here, we investigated whether nine plant lectins which have a binding profile similar to that of MBL competitively inhibit MBL deposition and subsequent complement activation following human umbilical vein endothelial cell (HUVEC) oxidative stress. HUVEC oxidative stress (1% O(2), 24 hr) significantly increased Ulex europaeus agglutinin II (UEA-II) binding by 72 +/- 9% compared to normoxic cells. UEA-II inhibited MBL binding to HUVEC in a concentration-dependent manner following oxidative stress. Further, MBL inhibited UEA-II binding to HUVEC in a concentration-dependent manner following oxidative stress, suggesting a common ligand. UEA-II (< or = 100 micromol/L) did not attenuate the hemolytic activity, nor did it inhibit C3a des Arg formation from alternative or classical complement pathway-specific hemolytic assays. C3 deposition (measured by ELISA) following HUVEC oxidative stress was inhibited by UEA-II in a concentration-dependent manner (IC(50) = 10 pmol/L). UEA-II inhibited C3 and MBL co-localization (confocal microscopy) in a concentration-dependent manner on HUVEC following oxidative stress (IC(50) approximately 1 pmol/L). Finally, UEA-II significantly inhibited complement-dependent neutrophil chemotaxis, but failed to inhibit fMLP-mediated chemotaxis, following endothelial oxidative stress. These data demonstrate that UEA-II is a novel, potent inhibitor of human MBL deposition and complement activation following human endothelial oxidative stress.     

Effects on growth and comparison of root tissue colonization patterns of Eucalyptus viminalis by pathogenic and nonpathogenic strains of Fusarium oxysporum

Soilborne pathogens, especially Fusarium oxysporum , are responsible for damping-off and root necrosis in Eucalyptus nurseries. New technologies are increasingly considering strategies for plant disease control other than chemical fungicides. Among these, natural fungal antagonists, which are colonizers of the root cortex, are potential biocontrol agents. An in vitro system was used: (1) to test the pathogenic effects of F. oxysporum strain Foeu1 which was recovered from a forest nursery soil; (2) to explore the potential of the nonpathogenic F. oxysporum strain Fo47, which is known for its efficiency in biological control, to suppress damping-off of Eucalyptus seedlings; (3) to compare the patterns of root colonization and host response to invasion by the two Fusarium strains inoculated separately in a time-course study. Root inoculation of E. viminalis with F. oxysporum strain Foeu1 caused damping-off in young seedlings in vitro , whilst disease symptoms were not visible in plants inoculated with F. oxysporum strain Fo47 or when both strains (Foeu1 + Fo47) were inoculated simultaneously. Each strain showed similarities in patterns of root tissue colonization, and in the processes of root penetration and initial colonization. Differential effects on root tissue were observed with fungal development within the cortex: ingress of strain Foeu1 was accompanied by severe host-cell alterations whilst no tissue damage occurred with development of strain Fo47.     

A commercial iron fertilizer increases the survival of Fusarium oxysporum f. sp. orthoceras propagules in a wheat flour-kaolin formulation

Fusarium oxysporum f.sp. orthoceras, a potential biocontrol agent against the parasitic weed Orobanche cumana Wallr., has proven to be efficacous under greenhouse conditions when formulated as wheat-kaolin granules. To help minimize the loss of viable fungal propagules during the formulation process, the addition of a commercial fertilizer containing the iron chelate of EDDHA to the formulation was investigated. The proportion of surviving propagules was significantly increased after adding the fertilizer. However, growing conidia in fertilizer-amended liquid medium did not reduce losses in viability during formulation. The efficacy of the formulated fungus and the storability at room temperature for the first 3 months was not affected by the iron fertilizer. The protective effect could neither be obtained with the chelator EDDHA alone nor with FeEDTA or FeSO_4.     

Biological control of Meloidogyne incognita and Fusarium solani in dry common bean in the field

Meloidoyne incognita (root-knot nematode) and Fusarium solani (root-rot pathogen) were the common soil-borne pathogens and cause severe damage to bean plants in newly reclaimed sandy soil in Nubaryia district, Behera Governorate, Egypt. The antagonistic effects of Trichoderma album and Trichoderma viride as well as three commercial products namely Rhizo-N^® (Bacillus subtilis), Bio-Arc^® 6% (Bacillus megaterium) and Bio-Zeid^® 2.5% (T. album) were tested against M. incognita and F. solani under naturally infected field conditions. T. album and T. viride highly reduced the frequency (%) population of pathogenic fungi such as Fusarium spp., F. solani and Rhizoctonia spp., than the commercial products. Results indicated that all the tested bio-control agents reduced, significantly, the nematode criteria as evidenced by the number of juvenile (J₂) in soil and number of galls and egg masses on roots of common bean and Fusarium root-rot incidence (%). Rhizo-N^® highly reduced the number of J₂ in soil, while T. album was the best in reducing the number of galls and egg masses in roots. The bio-control agents also increased the plant growth parameters of common bean plants i.e. plant height, plant weight, branch no./plant, pods no./plant, pod weight/plant, pod weight, seeds no./plant, fresh seeds weight/pod, dry seeds weight/pod and dry weight of 100 seeds.