Herbicidal Potential of Ophiobolins Produced by Drechslera gigantea

Abstract

Drechslera gigantea, a potential mycoherbicide of grass weeds, was isolated in Florida from naturally infected large crabgrass (Digitaria sanguinalis); it produces phytotoxic metabolites in liquid culture. The main metabolite was identified by spectroscopic methods and optical properties as ophiobolin A (1), a well-known phytotoxic sesterterpene produced by several phytopathogenic fungi of important crops and already extensively studied for its interesting biological activities. The other three minor metabolites proved to be related to ophiobolin A and were identified using the same techniques as 6-epi-ophiobolin A and 3-anhydro-6-epi-ophiobolin A (2 and 3) and ophiobolin I (4). Assayed on punctured detached leaves of several grass and dicotyledon weeds, ophiobolin A proved to be on average more phytotoxic as compared to the other related compounds. Some structural features appear to be important for the phytoxicity, such as the hydroxy group at C-3, the stereochemistry at C-6, and the aldehyde group at C-7. Furthermore, grass weeds usually proved to be more sensitive to the phytotoxins than dicotyledons, on which ophiobolin A caused the appearance of large necrosis even at the lowest concentration assayed. This is the first report about the production of ophiobolins from D. gigantea and of the proposed use as potential natural herbicides against grass weeds.

Phytotoxic effects of metabolites from Alternaria euphorbiicola against its host plant Euphorbia heterophylla

“…At concentrations ranging from 0.1 mM to 0.6 mM, degrees of lesions caused by some terpenoids and diketopyperazines obtained from other phytopathogenic fungi in their respective hosts 11,17,18 are very similar to those observed in the present work. Thus, as considered for those phytotoxins, the phytotoxic metabolites produced by A. euphorbiicola may be, in part, responsible for the virulence of this necrotrophic fungus against E. heterophylla.…”

ISOLATION AND CHARACTERIZATION OF NATURAL HERBICIDAL COMPOUND FROM Drechslera rostrata

“…The isolate was maintained on potato dextrose agar plates until further processing. Mass culturing of the fungal isolate was carried out in M-1-D broth (growth medium) (Evidente et al, 2006b). This medium was autoclaved and inoculated with bits of mycelia and spores of D. rostrata and kept at 25 o C. After 28 days of growth, fungal cultures and their metabolites were subjected to further processing.…”

“…This compound was effective against Avena sativa (Kastanias and Chrysayi-Tokousbalides, 2005). Evidente et al (2006b) isolated and identified phytotoxic/ herbicidal constituents (e.g. ophiobolin A) from a fungus, Drechslera gigantea, which has herbicidal properties against many monocot and dicot weeds such as C. album.…”

Herbicidal Potential of Drechslera spp. Culture Filtrates Against Parthenium hysterophorus L.

“…Kastanias and Tokousbalides (2000) isolated pyrenophorol from a D. avenae pathotype that exhibited herbicidal potential against Avena sterilis L. Evidente et al (2005) reported that drazepinone, a trisubstituted tetrahydronaphthofuroazepinone from D. siccans, exhibited herbicidal activity against monocot weeds. In another study, Evidente et al (2006b) identified four herbicidal constituents from D. gigantea, viz. ophiobolin A, 6-epi-ophiobolin A, anhydro-6-epi-ophiobolin A, and ophiobolin I, which were very effective against several grass and broadleaf weeds.…”