Comparative degradation of oomycete, ascomycete, and basidiomycete cell walls by mycoparasitic and biocontrol fungi

Abstract

Fourteen fungi (primarily representing mycoparasitic and biocontrol fungi) were tested for their ability to grow on and degrade cell walls (CWs) of an oomycete (Pythium ultimum), ascomycete (Fusarium equisetii), and basidiomycete (Rhizoctonia solani), and their hydrolytic enzymes were characterized. Protein was detected in the cultural medium of eleven of the test isolates, and these fungi significantly degraded CWs over the 14-day duration of the experiment. In general, a greater level of CW degradation occurred for F. equisetii and P. ultimum than for R. solani. Fungi that degraded F. equisetii CWs were Coniothyrium minitans, Gliocladium roseum, Myrothecium verrucaria, Talaromyces flavus, and Trichoderma harzianum. Taxa degrading P ultimum CWs included Chaetomium globosum, Coniothyrium minitans, M. verrucaria, Seimatosporium sp., Talaromyces flavus, Trichoderma hamatum, Trichoderma harzianum, and Trichoderma viride. Production of extracellular protein was highly correlated with CW degradation. Considerable variation in the molecular weights of CW-degrading enzymes were detected among the test fungi and the CW substrates in zymogram electrophoresis. Multivariate analysis between CW degradation and hydrolysis of barley beta-glucan (beta1,3- and beta1,4-glucanases), laminarin (beta1,3- and beta1,6-glucanases), carboxymethyl cellulose (endo-beta1,4-glucanases), colloidal chitin (chitinases), and chitosan (chitosanases) was conducted. For F. equisetii CWs, the regression model accounted for 80% of the variability, and carboxymethyl cellulases acting together with beta-glucanases contributed an R2 of 0.52, whereas chitinases and beta-glucanases alone contributed an R2 of 0.11 and 0.12, respectively. Only 61% of the variability observed in the degradation of P. ultimum CWs was explained by the enzyme classes tested, and primarily beta-glucanases (R2 of 0.53) and carboxymethyl cellulases (R2 of 0.08) alone contributed to CW break down. Too few of the test fungi degraded R. solani CWs to perform multivariate analysis effectively. This study identified several fungi that degraded ascomyceteous and oomyceteous, and to a lesser extent, basidiomycetous CWs. An array of enzymes were implicated in CW degradation.

Biocontrol of toxigenic strain of Aspergillus flavus isolated from the root tubers of safed musli (Chlorophytum borivilianum Sant. F) using its rhizospheric mycoflora

“…derma which was found interacting in the present study has already been recognized as the most potent biological control agent for certain plant diseases from the last 20 years (Inglis, 2002). Other similar studies indicating inhibition of aflatoxin production by A. flavus and A. parasiticus when cultured with Trichoderma sp.…”

Identifying glycoside hydrolase family 18 genes in the mycoparasitic fungal species Clonostachys rosea

“…For growth rate measurements under different carbon conditions, C. rosea WT and the deletion strains were inoculated on SMS medium with 1 % (w/v) glucose, 1 % (w/v) colloidal chitin (Sigma-Aldrich) or 1 % (w/v) R. solani cell wall material (Inglis & Kawchuk, 2002) as the sole carbon source, and containing 1.5 % agar. The agar plates were incubated at 25 uC in darkness and mycelial growth rates were recorded daily.…”

“…IK726 was isolated from Fusarium culmoruminfected barley roots (Knudsen et al, 1997). C. rosea produces extracellular chitinases during growth on Fusarium equisetii and Pythium ultimum cell wall material (Inglis & Kawchuk, 2002), and three chitinase genes [ech37, chi1 (also referred to as ech42) and ech58 ] have been identified in C. rosea (Gan et al, 2007;Mamarabadi et al, 2008a). The ech37 gene is of bacterial origin and is present in C. rosea through horizontal gene transfer (Ubhayasekera & Karlsson, 2012).…”

A PKS gene, pks-1, is involved in chaetoglobosin biosynthesis, pigmentation and sporulation in Chaetomium globosum

“…On the other hand, C. globosum has a broad range of applications in agriculture and industry. For instance, it has been used as a biocontrol agent against pathogenic microbes and even aphids [3,4]. Able to degrade plant biomass, C. globosum is potentially applicable for the making of biofuel from cellulignin materials [5].…”