Trichoderma Aureoviride Research Articles

Trichoderma aureoviride 7-121, a mutant with enhanced production of lytic enzymes: its potential use in waste cellulose degradation and/or biocontrol

A mutant of the native fungus Trichoderma aureoviride , 7-121, selected for its overproduction of extracellular cellulase and ß-glucosidase (cellobiase) was obtained. In shake flask cultures, production of endoglucanase, filter paper activity and cellobiase increased two to four- fold as compared with the wild type strain. The mutant strain is stable and grows rapidly in liquid as well as in solid culture media. Enzyme yields were best when pH was controlled so that it did not fall bellow pH 3.5. Cellobiase production by this mutant is particularly high (approximately 5 U/ml) as compared to other Trichoderma, strains, which makes it a suitable candidate for waste cellulose degradation. In addition, the mutant strain showed enhanced production of fungal cell wall degrading enzymes: chitinases,ß-1,3-glucanases and proteases. This improvement in extracellular enzyme production by the mutant T. aureoviride 7-121 suggests that it is a suitable strain to be used in biological control.

Trichoderma aureoviride 7-121, a mutant with enhanced production of lytic enzymes: its potential use in waste cellulose degradation and/or biocontrol

A mutant of the native fungus Trichoderma aureoviride , 7-121, selected for its overproduction of extracellular cellulase and s-glucosidase (cellobiase) was obtained. In shake flask cultures, production of endoglucanase, filter paper activity and cellobiase increased two to four- fold as compared with the wild type strain. The mutant strain is stable and grows rapidly in liquid as well as in solid culture media. Enzyme yields were best when pH was controlled so that it did not fall bellow pH 3.5. Cellobiase production by this mutant is particularly high (approximately 5 U/ml) as compared to other Trichoderma, strains, which makes it a suitable candidate for waste cellulose degradation. In addition, the mutant strain showed enhanced production of fungal cell wall degrading enzymes: chitinases,s-1,3-glucanases and proteases. This improvement in extracellular enzyme production by the mutant T. aureoviride 7-121 suggests that it is a suitable strain to be used in biological control.

Aetiology and biological control of Fusarium wilt of pinks (Dianthus caryophyllus) using Trichoderma aureoviride

Fusarium oxysporum f.sp. dianthi (F.o.d.) was the species isolated most frequently from wilted glasshouse‐grown pinks in south‐west England, whereas F. avenaceum was less prevalent and F. culmorum was not found. Although infections by F. avenaceum, via the roots or through a cut‐stem wound, caused symptoms identical to those characterizing mild infections due to F.o.d., the former was always pathogenically weak relative to the latter. Of several organisms screened for potential antagonistic capacity towards F.o.d., using an in‐vitro dual culture plate technique, Trichoderma aureoviride, isolated as an endophyte from healthy pinks, proved most effective. Elevated temperatures substantially reduced the antagonistic capacity of micro‐organisms in both in‐vitro and in‐vivo screens, except in the case of T. aureoviride where maximum antagonism occurred at 28°C, which was near the optimum for wilt disease in pinks. The tolerance shown by T. aureoviride to a wide range of pesticides used in commercial production of pinks under cover indicated its potential in a proposed integrated disease control programme.

Monitoring and manipulation of populations of Pythium oligandrum, Pythium mycoparasiticum and a Papulaspora species in soil

Pythium oligandrum, Pythium mycoparasiticum and Papulaspora sp. were detected by production of their characteristic resting propagules (oospores or bulbils) when soils or soil-sand dilutions were placed on agar colonized by other fungi. Frequency of detection of Papulaspora (on agar colonized by Botrytis cinerea) was enhanced when metalaxyl was incorporated into the agar to suppress competition from P. oligandrum; detection of P. mycoparasiticum (on agar colonized by B. cinerea, Phialophora sp. or Fusarium culmorum) was enhanced by dilution of soil to reduce the P. oligandrum content. When soil was supplemented with mature wheat flag leaf (but not green grass leaves) the resident population of P. oligandrum was enhanced during 280 days, assessed by most probable number (MPN) analysis when serial soil dilutions were plated. A second supplement of wheat flag leaf or grass leaf at 150 days significantly and further enhanced the P. oligandrum population. When oospores of a metalaxyl-tolerant P. oligandrum were added to soil, this strain could be recovered after 240 days and it enhanced the total population of P. oligandrum throughout this time. P. mycoparasiticum was not amenable to MPN analysis because of competition from P. oligandrum in undiluted soils, but its incidence of detection in the higher dilutions suggested a population density similar to P. oligandrum, and this was supported by log-probit regression of detection frequency in soils in which P. oligandrum was rare. When cellulose film colonized by B. cinerea, Phialophora sp. or F. culmorum was buried in soil it was colonized mainly by P. oligandrum if the soil was undiluted, but mainly by P. mycoparasiticum if the soil was diluted with sand, indicating competition between the mycoparasites in soil. In laboratory studies on “host”-preference, Papulaspora grew from agar disc inocula across agar colonies of several fungi, but from bulbil inocula it grew only across B. cinerea and Trichoderma aureoviride, which are the fungi that enable its detection in soil. In liquid medium, Papulaspora grew only in the presence of B. cinerea, but grew well on media that had previously supported growth of F. culmorum or Rhizoctonia solani. In soil Papulaspora was selectively isolated from cellulose film or wheat flag leaves previously colonized by Humicola grisea, but not from substrata left uncolonized or colonized by Rhizoctonia oryzae. This ability of secondary colonizers to invade only some fungal colonies may relate to substrate-possession of crop residues by pathogens in nature. The improved detection methods here suggest that P. mycoparasiticum and Papulaspora sp. are common and abundant in soil, and that other mycoparasites might be detected by eliminating competition from fast-growing species such as P. oligandrum. The coexistence of mycoparasites that can compete with one another in soil suggests that they have different ecophysiological features (niches) of potential exploitation in biocontrol.

Mycoparasite‐like behaviour of the plant pathogen Pythium aphanidermatum in vitro

Pythium aphanidermatum antagonized several other fungi after hyphal contact on films of water agar, recorded by video microscopy. It sometimes coiled round, penetrated and caused cytoplasmic coagulation of hyphae of the mycoparasites P. oligandrum, P. acanthophoron, P. mycoparasiticum and P. periplocum, but was not affected by them. It also coiled round, penetrated and coagulated P. ultimum, P. vexans, P. catenulatum, P. dissotocum and (infrequently) P. graminicola. It caused cytoplasmic coagulation of Fusarium oxysporum and Trichoderma aureoviride after contact, but without coiling. Six isolates of P. aphanidermatum behaved similarly, with a mode of action like that of the mycoparasite P. oligandrum but less rapid and consistent than this species. The results are discussed in relation to possible ecological roles of P. aphanidermatum.

Interactions of trichoderma spp. with Glomus mosseae and two wilt pathogenic fungi

Two Trichoderma aureoviride and two Trichoderma harzianum isolated from organic composts were considered to be involved in suppressiveness of Fusarium wilt. Microscopic examination indicated that hyphae from both aureoviride isolates grew and coiled around the hyphae of Fusarium oxygporum “in vitro”. Non-volatile compounds released by both T. harzianum isolates growing on cellophane disks over malt agar significantly (P= 0.001) inhibited growth of Fusarium oxygsporum and Verticillium dahliae “in vitro”. The same Trichoderma isolates were tested for their influence on Glomus mossaea. Inoculation with each isolate esparately had no significant effect on spore germination, but there was a highly significant (P= 0.001) increase in the production of vegetation spores on the mycelium from G. mosseas germinated resting spores when Trichoderma spp. was inoculated in the center of the plate.

Aggressiveness and fungal host ranges of mycoparasitic Pythium species

As evidenced by the ability to reduce cellulolytic activities of host fungi on cellulose film or filter paper, Pythium oligandrum was a more aggressive mycoparasite than Pythium SWO which, in turn, was usually more aggressive than Pythium nunn. Both P. oligandrum and Pythium SWO produced oogonia in the presence of susceptible host fungi, deriving carbon, organic N and sterols from the hosts. P. nunn did not form oogonia with any host, and it was the only mycoparasite that utilized nitrate as sole N source. Host fungi differed in resistance, in the same ranking order with each mycoparasite. Phialophora sp. and Trichoderma aureoviride were most susceptible; Pythium graminicota and Rhizoctonia solani were most resistant, and Fusarium culmorum, F. oxysporum and Botryotrichum piluliferum showed intermediate susceptibility. Botrytis cinerea was susceptible to P. oligandrum but not usually to Pythium SWO or P. nunn, which it antagonized. The findings support previous evidence from hyphal interactions on water agar but with some differences, ascribed to ‘disease escape’ within host colonies. P. oligandrum grew across agar previously colonized by several host fungi, but Pythium SWO and P. nunn grew across few host colonies. Trichoderma harzianum grew across colonies of several hosts, some different from those that supported P. oligandrum. Gliocladium roseum grew across colonies of nearly all hosts. The implications of these findings for biocontrol arc discussed.

Biological Control of Sheath Blight Disease of Rice

Trichoderma aureoviride restricted the mycelial growth and sclerotial initiation in a virulent isolate of Rhizoctonia solani over culture medium by 52.7 and 95.3% respectively. Microscopic examination of the R. solani mycelium near the inhibition zone revealed that more than 25% of the mycelia were lysed and most of the hyphal tips showed bulb-like terminal enlargements. Pot culture experiments showed that soil amendment with T. aureoviride brought down considerably the incidence and severity of the sheath blight disease in TKM-9 rice.

Effect of dilution rate on ?-glucosidase secretion and cell wall metabolism in Trichoderma aureoviride cultivated in a continuous air lift fermenter

Trichoderma aureoviride was grown in continuous culture under glucose limitation in an airlift fermenter at dilution rates (D) varying between 0.06–0.21 h−1. Autoradiography showed a high incorporation of 3H-GlcNAc into hyphal tips under these conditions, indicating that the hyphae were not suffering from physical stress.