Inmaculada García-Romera

Interactions between Trichoderma koningii, Fusarium solani and Glomus mosseae: Effects on plant growth, arbuscular mycorrhizas and the saprophyte inoculants

Abstract The effect of inoculation with the saprophytic fungi Trichoderma koningii and Fusarium solani on maize ( Zea mays ) and lettuce ( Lactuca sativa ) with or without arbuscular mycorrhizal (AM) colonization by Glomus mosseae was studied in a greenhouse trial. Plant dry wt of non-AM inoculated maize and lettuce were unaffected by the presence of T. koningii and F. solani . In contrast, T. koningii decreased plant dry wt and AM colonization when inoculated into the rhizosphere before or at the same time as G. mosseae . In addition, the T. koningii population was considerably reduced when G. mosseae was inoculated 2 weeks before the saprophytic fungus. At this time T. koningii did not affect the proportion of the root length colonized by G. mosseae , but did adversely affect its metabolic activity assessed as succinate dehydrogenase activity. Although F. solani did not affect AM colonization of maize roots, its effect on AM colonization of lettuce roots was similar to that of T. koningii . The population of F. solani decreased significantly in the rhizosphere of both plants. The possible mechanisms of interaction between the saprophytic fungi and G. mosseae are discussed.

Arbuscular mycorrhizal colonization and growth of soybean (Glycine max ) and lettuce (Lactuc sativa ) and phytotoxic effects of olive mill residues

We studied the influence of olive mill dry residue (DOR) on growth of soybean (Glycine max ) and lettuce (Lactuca sativa ) colonized with the arbuscular fungi Glomus mosseae or G. deserticola. The DOR has 6 mg g 21 of soluble phenolic compounds and the application of 2.5 g kg 21 of DOR (15 mg kg 21 of phenolic content) to soil decreased the growth of plants colonized with the AM fungi. The application to the soil of 10 g kg 21 of DOR (60 mg kg 21 of phenolic content) decreased the dry weight of nonarbuscular mycorrhizal (AM) plants. The application of DOR decreased the percentage of AM colonization of plants except those were inoculated with G. mosseae or G. deserticola 4 weeks before the application of DOR. No effect of the residue on the colonization of these previously AM inoculated plants was observed. DOR had no effect neither on the fungal succinate dehydrogenase activity nor on the most probable number of AM propagules in all treated soils. The obtained results showed than AM fungi increased the phytotoxicity of DOR in lettuce and soybean. q 2002 Elsevier Science Ltd. All rights reserved.

Interactions between Glomus mosseae and arbuscular mycorrhizal sporocarp-associated saprophytic fungi

The saprophytic fungi Wardomyces inflatus (Marchal) Hennebert, Paecilomyces farinosus (Holm & Gray) A. H. S. Brown & G. Sm., Gliocladium roseum Bain., sterile dark mycelium (SDM-54), Trichoderma pseudokoningii Rifai and Trichoderma harzianum Rifai were isolated from sporocarps of Glomus mosseae. The effect of saprophytic fungi on G. mosseae spore germination was tested on water agar. Wardomyces inflatus decreased the percent germination of G. mosseae spores; G. roseum, T. pseudokoningii and T. harzianum had no effect on germination; and P. farinosus and SDM-54 increased the percentage of spore germination of G. mosseae after 4 d. Wardomyces inflatus significantly decreased hyphal length of spores which germinated, but no other saprophytic fungi affected hyphal growth. Trichoderma pseudokoningii, T. harzianum, P. farinosus and SDM-54 increased the number of auxiliary cells formed by G. mosseae. The effect of saprophytic fungi on arbuscular mycorrhizal colonization of soybean was studied in a greenhouse trial. The percentage of soybean root length colonized was decreased by W. inflatus, unaffected by SDM-54 and T. harzianum, and increased by P. farinosus. Gliocladium roseum decreased root length colonized when plants were 12 wk old, and T. pseudokoningii increased colonization of roots when plants were 4 wk old. Antagonistic, synergistic and neutral actions of G. mosseae upon the saprophytic fungi were observed. The population of T. harzianum decreased and the populations of T. pseudokoningii and SDM-54 increased in the presence of G. mosseae. Our results indicate a complex interaction between G. mosseae and associated saprophytic fungi.

Potential of non-ligninolytic fungi in bioremediation of chlorinated and polycyclic aromatic hydrocarbons.

In previous decades, white-rot fungi as bioremediation agents have been the subjects of scientific research due to the potential use of their unspecific oxidative enzymes. However, some non-white-rot fungi, mainly belonging to the Ascomycota and Zygomycota phylum, have demonstrated their potential in the enzymatic transformation of environmental pollutants, thus overcoming some of the limitations observed in white-rot fungi with respect to growth in neutral pH, resistance to adverse conditions and the capacity to surpass autochthonous microorganisms. Despite their presence in so many soil and water environments, little information exists on the enzymatic mechanisms and degradation pathways involved in the transformation of hydrocarbons by these fungi. This review describes the bioremediation potential of non-ligninolytic fungi with respect to chlorinated hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) and also shows known conversion pathways and the prospects for future research.

Defence response of tomato seedlings to oxidative stress induced by phenolic compounds from dry olive mill residue

ADOR is an aqueous extract obtained from the dry olive mill residue (DOR) which contains the majority of its soluble phenolic compounds, which are responsible for its phytotoxic properties. Some studies have shown that ADOR negatively affects seed germination. However, to date, few studies have been carried out on the effect of ADOR on the oxidative stress of the plant. It is well known that saprobe fungi can detoxify these phenolic compounds and reduce the potential negative effects of ADOR on plants. To gain a better understanding of the phytotoxic effects and oxidative stress caused by this residue, tomato seeds were germinated in the presence of ADOR, treated and untreated with Coriolopsis rigida, Trametes versicolor, Pycnoporus cinnabarinus and Penicillium chrysogenum-10 saprobe fungi. ADOR sharply reduced tomato seed germination and also generated high levels of malondialdehyde (MDA), O(2)(-) and H(2)O(2). However, bioremediated ADOR did not negatively affect germination and reduced MDA, O(2)(-) and H(2)O(2) content in different ways depending on the fungus used. In addition, the induced defense response was studied by analyzing the activity of both antioxidant enzymes (superoxide dismutase (SOD), catalase, ascorbate peroxidasa, glutathione reductase (GR), peroxidases and coniferil alcohol peroxidasa) and detoxification enzymes (glutathione-S-transferase (GST)). Our findings suggest that, because ADOR is capable of inducing oxidative stress, tomato seedlings trigger a defense response through SOD, GR, and GST activity and through antioxidant and lignification processes. On the other hand, the bioremediation of ADOR plays an important role in counteracting the oxidative stress induced by the untreated residue.

Production of xyloglucanolytic enzymes by Trichoderma viride, Paecilomyces farinosus, Wardomyces inflatus, and Pleurotus ostreatus

Different conditions of culture medium, incubation time, concentration and surfactant were tested to determine xyloglucanase activity. Trichoderma viride, Paecilomyces farinosus, Wardomyces inflatus and Pleurotus ostreatus showed increased xyloglucanase activities when the fungi grown on microcrystalline cellulose as the sole carbon source. Endoxyloglucanase activity increased with the growth of the fungi and reached a peak on day 14 of incubation, practically 95% of the activity was associated with the extracellular fraction. Precipitation with ammonium sulfate was the best concentration method for detection of endoxyloglucanase activity of the fungi. Endoxyloglucanase activity of the fungi was increased by 4 fold with the use of the non-ionic surfactant Tween 20. Six and three bands of xyloglucanase activities were observed in T. viride and P. ostreatus, respectively, whereas both P. farinosus and W. inflatus presented only one xyloglucanase activity band. These results indicate the presence of several xyloglucanases in the saprophytic fungi examined.

In vitro interactions between Trichoderma koningii, Fusarium solani and Glomus mosseae

Abstract The inoculation of maize plants with spores of G. mosseae decreased the populations of the saprophytic fungi Trichoderma koningii and Fusarium solani. However, F. solani had no effect on mycorrhizal development, whereas G. mosseae was inhibited in its extramatrical stage by T. koningii. Germinated spores of G. mosseae did not affect growth of the saprophytic fungi on water-agar. T. koningii inhibited the germination, but not mycelial development of G. mosseae; this inhibition was independent of the change in pH of the medium. F. solani did not inhibit germination of G. mosseae spores, and endophyte hyphal development was markedly stimulated. The influence of soluble and volatile substances produced by the saprophytic fungi on these effects is discussed.

Interaction between Alternaria alternata or Fusarium equiseti and Glomus mosseae and its effects on plant growth

Abstract The effect of inoculation with the saprophytic fungi Alternaria alternata or Fusarium equiseti on maize (Zea mays) and lettuce (Lactuca sativa) with or without arbuscular mycorrhizal (AM) colonization by Glomus mosseae was studied in a greenhouse trial. Plant dry weights of non-AM-inoculated maize and lettuce were unaffected by the presence of A. alternata and F. equiseti. In contrast, A. alternata and F. equiseti decreased plant dry weights and mycorrhization when inoculated to the rhizosphere before G. mosseae. The saprophytic fungi inoculated 2 weeks after G. mosseae did not affect the percentage of root length colonized by the AM endophyte, but did affect its metabolic activity assessed as succinate dehydrogenase activity. Although F. equiseti inoculated at the same time as G. mosseae did not affect mycorrhization of maize roots, its effect on AM colonization of lettuce roots was similar to that with A. alternata. In the rhizosphere of both plants, the population of saprophytic fungi decreased significantly, but was not affected by the presence of G. mosseae. Our results suggest that there may have been a direct effect of the saprophytic fungi on the mycorrhizal fungi in the extramatrical phase of the latter, and when the AM fungus was established in the root the AM fungus was less affected by the saprophytic fungi.

Advanced oxidation of benzene, toluene, ethylbenzene and xylene isomers (BTEX) by Trametes versicolor

Advanced oxidation of benzene, toluene, ethylbenzene, and o-, m-, and p-xylene (BTEX) by the extracellular hydroxyl radicals (*OH) generated by the white-rot fungus Trametes versicolor is for the first time demonstrated. The production of *OH was induced by incubating the fungus with 2,6-dimethoxy-1,4-benzoquinone (DBQ) and Fe3+-EDTA. Under these conditions, *OH were generated through DBQ redox cycling catalyzed by quinone reductase and laccase. The capability of T. versicolor growing in malt extract medium to produce *OH by this mechanism was shown during primary and secondary metabolism, and was quantitatively modulated by the replacement of EDTA by oxalate and Mn2+ addition to DBQ incubations. Oxidation of BTEX was observed only under *OH induction conditions. *OH involvement was inferred from the high correlation observed between the rates at which they were produced under different DBQ redox cycling conditions and those of benzene removal, and the production of phenol as a typical hydroxylation product of *OH attack on benzene. All the BTEX compounds (500 microM) were oxidized at a similar rate, reaching an average of 71% degradation in 6 h samples. After this time oxidation stopped due to O2 depletion in the closed vials used in the incubations.

Negative influence of non-host plants on the colonization of Pisum sativum by the arbuscular mycorrhizal fungus Glomus mosseae.

Abstract We studied the influence of the arbuscular mycorrhizal (AM) non-host plants Stellaria media (Caryophyllaceae), Chenopodium album and Spinaceae oleracea (Chenopodiaceae), Brassica campestris , B. nigra , Capsella bursa-pastoris and Sisymbrium altissimum (Brassicaceae), Juncus balticus (Juncaceae), Urtica dioica (Urticaceae) and of the AM host plant Taraxacum officinale (Asteraceae) on the colonization of Pisum sativum by the AM fungus Glomus mosseae . None of the non-host plants tested were colonized by Glomus mosseae . Older non-host plants competed with P. sativum . No inhibition of AM colonization was observed in host plants that were grown in the same pot and at the same time as non-host plants. However, when non-host plants were grown for 30 d before P. sativum , they inhibited mycorrhizal colonization of the latter. In a split pot system the presence of U. dioica on the left-side decreased AM colonization of P. sativum roots on the left-side, but not on the right-side. Non-host plants decreased the inoculum potential of G. mosseae and in some cases the percentage AM colonization of host plants cultivated after non-host plants. These results indicate that roots of non-host species have factors that seem to affect the AM fungus before it establishes in the root of host plants.