Indole derivatives produced by the fungusColletotrichum acutatumcausing lime anthracnose and postbloom fruit drop of citrus

Abstract

Postbloom fruit drop (PFD) of citrus and Key lime anthracnose (KLA) are caused by Colletotrichum acutatum. Both fungal isolates can infect flower petals, induce young fruit abscission and result in severe yield loss on many citrus cultivars. Previous studies revealed that infection of citrus flowers by C. acutatum caused higher levels of indole-3-acetic acid (IAA), which could be synthesized from the host plant and/or the fungal pathogen. The ability for IAA production by C. acutatum isolates was investigated. Similar to many microorganisms, the production of indole compounds in the medium by C. acutatum was dependent solely on the presence of tryptophan (Trp). In total, 14 PFD and KLA fungal isolates were tested, and revealed that they all were capable of utilizing Trp as a precursor to synthesize IAA and other indole derivatives. High-performance liquid chromatography analysis and chromogenic stains after a fluorescence thin-layer chromatography separation unambiguously identified IAA, tryptophol (TOL), indole-acetaldehyde, indoleacetamide (IAM), indole-pyruvic acid, and indole-lactic acid (ILA) from cultures supplemented with Trp. The data suggest that C. acutatum may synthesize IAA using various pathways. Interestingly, increasing Trp concentrations drastically increased the levels of TOL and ILA, but not IAA and IAM. The ability of C. acutatum to produce IAA and related indole compounds may in part contribute to the increased IAA levels in citrus flowers after infection. ß

Production of Indole-3-Acetic Acid via the Indole-3-Acetamide Pathway in the Plant-Beneficial Bacterium Pseudomonas chlororaphis O6 Is Inhibited by ZnO Nanoparticles but Enhanced by CuO Nanoparticles

“…Both IAM and IAA were detected by thin-layer chromatography (TLC) on plates of silica Gel 60 (EMD Chemicals Inc., Darmstadt, Germany). The plates were loaded with 20 l of aliquots of the acidified methanol extracts from the culture filtrate and compounds separated in hexane:ethyl acetate:isopropanol:acetic acid (40:20:5:1) for 60 min (7). Following drying, the plates were sprayed with Salkowski's reagent to detect indoles (7).…”

“…The plates were loaded with 20 l of aliquots of the acidified methanol extracts from the culture filtrate and compounds separated in hexane:ethyl acetate:isopropanol:acetic acid (40:20:5:1) for 60 min (7). Following drying, the plates were sprayed with Salkowski's reagent to detect indoles (7). The migration of pure IAM and IAA, applied from solutions at 200 g/ml, was used as a standard.…”

Salkowski’s Reagent Test as a Primary Screening Index for Functionalities of Rhizobacteria Isolated from Wild Dipterocarp Saplings Growing Naturally on Medium-Strongly Acidic Tropical Peat Soil

“…Â 250 mm, Chemicals Evaluation and Research Institute, Tokyo) using MeOH: 1% CH 3 COOH, 25:75 19) as an isocratic mobile phase, with a UV detector at 280 nm. The retention times of TRP, ILA, TOL, IPyA, and IAA were tR 6.3, 22.8, 29.0, 30.9, and 33.5 min respectively (Figs.…”

Indole-3-acetic acid: A widespread physiological code in interactions of fungi with other organisms

“…4,[6][7][8][9][10] The role of microbial IAA in plantmicrobe interactions has recently received increasing attention. 3 The well-documented interaction is that between plants and phytopathogenic bacteria, which can inhibit plant development by disturbing the auxin balance in plants and cause tumors and galls.…”