Phytotoxic metabolite

Sirons, G.J., Frank, R., and Sawyer, T. Residues of atrazine, cyanazine, and their phytotoxic metabolites in a clay loam soil, J. Agric. Food Chem., 21(6) 1016-1019, 1973. 

Isoxaflutole is an isoxazole herbicide that, in the presence of hypochlorite, hydrolyzed to a stable and phytotoxic metabolite, diketonitrile. This intermediate further degraded to yield benzoic acid as the major end product, which is nonphytotoxic [112]. 

Plant residues can provide substrates for the production of phytotoxic metabolites by soil microorganisms but they can also support the growth of pathogens and other deleterious micro-organisms. This is illustrated by reference to the problems of establishing crops drilled in the presence of straw residues and of decaying weed and grass residues that have been previously killed with herbicides. 

Strange, R. N., Pippard, D. J. and Strobel, G. A. 1982. A protoplast assay for phytotoxic metabolites produced by Phytophthora drechsleri in culture. Physiol. Plant Pathol. 20, 359-364... 

Triazine tolerance is mainly regulated by the pathway and the rate of detoxication in a given plant species. The hydrolytic and conjugation processes which were listed in a) and b) allow resistant plants to transform the phytotoxic triazines rapidly into non-phytotoxic metabolites. Moderately susceptible plants may do this more slowly or for example through N-dealkylation, as listed in c), whereby metabolites are formed which may still possess some phytocidal activity. 

Zinniol. Zinniol [13] was first described as a phytotoxic metabolite of Alternarla zinniae (21). Zinniol is now known to be produced by many Alternaria spp., including fungal pathogens of weeds and crop plants (21). This compound causes necrosis in plants (21)> S2) and "green island formation, as discussed earlier. 

Botrydienal. A new phytotoxin, botrydienal [29], and two phytotoxic metabolites, dehydrobotrydienal and deacetyidlhydro-botrydial, have been Isolated from a phytopathogen1c fungus,... 

The formation of aromatic rings via rDA processes has found application in the synthesis of many natural products only a representative set can be presented here. Pyrenochaetic acid A (134), a phytotoxic metabolite, was synthesized by a process involving a rDA reaction as a key step. The DA reaction of pyrone (132) with ethyl propiolate gave, after isolation, benzoate (133) via a rDA reaction evolving carixin dioxide (equation 60). A synthesis of a-cartopterone (137) has been achieved that involves the rDA elimination of ethylene. The tey step is rDA decomposition of adduct (135) to naphthoquinone... 

Rosnecatrone 310 is a phytotoxic metabolite isolated from cultures of a virulent strain of the fungus Rosellinia necatrix In the initial tests using apple and geranium seedlings, 310 showed higher phytotoxicity than cytochalasin E. 

CBA contaminated soil but died when inoculated with degrader strains. Plant exudates were demonstrated to impact the bacteria physiology and bacteria inoculants are known to alter plant physiology. Thus, plants might change bacteria in such a way that they produce phytotoxins or phytotoxic metabolites or, alternatively, bacteria may interfere with certain plant detoxification processes. ... 

C. aphidicola. Other metabolites with a ten-membered lactone ring include the decarestrictins (4.76) from PenicUlium species such as P. simplicissimum and putaminoxin (4.77), which is a phytotoxic metabolite of Phoma putamimm. Recifeiolide (4.78) from C. recifei is a hexaketide with a 12-membered ring. Cladospolide A (4.79), also with a 12-membered ring, is a phytotoxic metabolite of Cladosporium fulvum. The decarestrictins affect cholesterol biosynthesis whilst the diplodialides were found to be steroid 11-hydroxylase inhibitors. Biosynthetic experiments with [ C]-labelled acetate established that the decarestrictins were polyketides. 

The fungus Fames annosus is the cause of another serious root decay of trees, particularly conifers. The phytotoxic metabolite, fomannosin (5.81) also arises by cleavage of a protoilludane, this time of the six-membered ring. The cleavage is followed by a lactonization. Labelling studies with [l,2- C2]acetate have confirmed this biosynthetic route. 

The silver-leaf disease of fruit trees is caused by the fungus Stereum pur-pureum. The phytotoxic metabolites such as sterpuric acid (5.82) possess the sterpurane skeleton which may also be derived from a protoilludane by a series of rearrangements. 

Alternaria species are associated with several leaf-spot diseases of plants. Alternaric acid (8.10), produced by A. solani, which is the cause of early blight on potatoes and tomatoes, has a marked phytotoxic activity and may be responsible for many of the symptoms of the plant disease caused by the fungus. It also shows a specific anti-fungal activity. The branched chain structure is biosynthesized from nine acetate units and three Ci units derived from formate. The solanopyrones are another group of phytotoxic metabolites of A. solani. Solanopyrone A (8.11) induced necrotic lesions on the leaves of potatoes typical of this fungal infection. The structures of the solanopyrones were established by... 

The pigments of the Fusaria have been described in Chapter 7. Many of the characteristic phytotoxic metabolites are the sesquiterpenoid trichothecenes (8.38) (see Chapter 5). The more highly hydroxylated members have considerable mammalian toxicity as well as phytotoxicity. Trichothecenes have been identified as metabolites of species from ten of the twelve sections of the genus Fusarium as classified by Booth. The trichothecenes occur with various combinations of oxygen substituents at positions 3, 4, 7, 8 and 15. Several trichothecenes contain macrocyclic esters linking C-4 and C-15. These are known as the roridins and verrucarins. 

Several species of Seiridium, including S. cardinale, S. cupressi and S. unicorne, are associated with the canker diseases of cypress, Cupressus sempervirens. The phytotoxic metabolites include the butenolides seiridin (8.61) and isoseiridin (8.62) and their 7 -hydroxy relatives as well as the sesquiterpenes seiricardine A (8.63) and B (8.64). Solutions of these sesquiterpenes when applied to leaves produce chlorosis, browning and death of the leaves. 

Subsequent ramification of inter and intra cellular mycelium induced morphological change and death. Recent evidence supports the hypothesis that fungi may be directly, or indirectly pathogenic to plants by the production of phytotoxic metabolites. 

Ichihara A, Nonaka M, Sakamura S, Sato R, Tajimi A. Structure and synthesis of alboatrin, a novel phytotoxic metabolite from Verticillium albo-atrum. Chem Lett 27-30, 1988. 

Recently, Sirons et al. (1973) investigated the degradation of atrazine (8) and cyanazine (18) in soil. Both compounds yield three phytotoxic metabolites ... 

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