Horace G. Cutler

In vitro auxin production by Balansia epichloë

Abstract Balansia epichloe , a systemic plant pathogen isolated from Sporobolus poiretii , was shown to produce the plant growth regulators 3-indole acetic acid, 3-indole ethanol, 3-indole acetamide and methyl-3-indole carboxylate when grown on a medium containing tryptophan. When grown on a tryptophan deficient medium 3-substituted indole derivatives were not detected. However, extracts of the medium in lower doses increased and in higher doses inhibited the growth of wheat coleoptiles.

Preliminary observations on the effects of macrocyclic trichothecenes on plant growth

Abstract The biological properties of the macrocyclic trichothecenes roridin A, isororidin E, baccharinol B4, verrucarin A, verrucarin J and trichoverrin B were assayed with etiolated wheat coleoptiles ( Triticum aestivum L.), bean ( Phaseolus vulgaris L.), corn ( Zea mays L.) and tobacco ( Nicotiana tabacum L.). Metabolites were tested from 10 −3 to 10 −8 M in the coleoptile assay and from 10 −2 to 10 −4 M in intact plants. All inhibited coleoptile growth; verrucarins A and J, and trichoverrin B inhibited to 10 −7 M. All induced effects in plants that ranged from chlorosis, necrosis, malformations to stunting.

Isolation and identification of two new biologically active norditerpene dilactones from Aspergillus wentii

Abstract Two new biologically-active norditerpenoid dilactones were purified from culture extracts of Aspergillus wentii and assigned the trivial names wentilactone A and wentilactone B. The absolute chemical structure of wentilactone A was determined by single crystal X-ray diffraction and circular dichroism. The structure of wentilactone B was determined by 1 H and 13 C NMR analyses. Wentilactone A had an ld 50 of 7.0 mg/kg when administered orally to 1-day-old chickens. Both metabolites inhibited growth in wheat coleoptile bioassays.

Desmethoxyviridiol, a new toxin from Nodulisporium hinnuleum

Abstract A new mycotoxin obtained from culture extracts of Nodulisporium hinnuleum was determined to be desmethoxyviridiol (C19H16O5,). The toxin had an oral median lethal dose of 4.2mg/kg in 1-day-old cockerels. Desmethoxyviridiol also produced plant-growth regulating and phytotoxic effects in plant systems. The physical and chemical characteristics of desmethoxyviridiol are described.

Unusual plant‐growth regulators from microorganisms

Microorganisms produce a wide assortment of secondary metabolites which may be used to control growth and development of plants. These natural products are diverse in structure and range from oligopeptides to complex and simple nonamino acid molecules. Each has unique properties, but in general they have high specific activity, a narrow spectrum of activity, and are biodegradable. Each molecule has the potential for synthetic modification by two routes. One is to derivatize the natural product; the other is to synthesize simpler structures which are analogs of the natural product. Thus, the spectrum of activity may be suitably altered. Fermentation products and their derivatives are logical candidates for the next generation of agrochemicals. Examples of microbial secondary metabolites and their structures, relative to biological activity, are discussed.

Ruakuric acid: A natural product from Aspergillus fumigatus

A new chroman derivative, named ruakuric acid, was isolated from a strain of Aspergillus fumigatus growing in conjunction with a coral lichen. The structure was determined as 6-acetyl-5-hydroxy-4-methoxy-chroman-2-carboxylic acid (mixture of 2,4-cis,trans isomers).

The structure of chaetoglobosin K.

Abstract The structure of chaetoglobosin K, a toxic metabolite from Diplodia macrospora , has been determined by single crystal X-ray analysis.

A growth inhibitor from young expanding tobacco leaves.

Extracts of expanding tobacco leaves inhibit the growth of wheat coleoptiles. Infrared, ultraviolet, and mass spectroscopy show that the active component is neither abscisin nor an aromatic structure.