Fumonisin-Plant Interactions

[Synopsis] The fumonisins are phytotoxins produced by fungi including Fusarium and Alternaria species infesting weeds, crops, soil and conifers. Fumonisin B_1 (FB_1) is also well-known as a mammalian toxin. FB_1 is a long-chain alkylamine with propanetricarboxylic moieties attached. It is structurally related to AAL-toxin, a phytotoxin first isolated from A. alternata f. sp. lycopersici, which causes stem canker disease on susceptible (asc / asc) tomatoes (Lycopersicon esculentum Mill.) . The susceptibility range of FB_1 and AAL-toxin has been investigated. Both toxins were initially thought to be host-specific to asc / asc tomatoes, but now are known to also be phytotoxic to weeds, specifically dicots. Symptoms include chlorosis, necrosis, stunting, and mortality. The fumonisins, especially FB_1, are produced by F. moniliforme, F. proliferatum and other Fusarium spp. of the Liseola section. Fumonisins were also isolated from A. alternata grown in liquid media and the mycelia and spores of A. alternata grown on solid rice media. FB_1 and AAL-toxin inhibit ceramide synthase, causing accumulation of free sphingolipid bases that are intermediates in the biosynthesis of sphingolipids, essential components of cell membrances. The accumulation of free sphingolipid bases is thought to result in the damage to cell components, cellular leakage, and chlorophyll loss. FB_1 and AAL-toxin were about 8 times more active than the recently-discovered ceramide synthase inhibitor australifungin. Duckweed was exposed to 1 μM FB_1, 1μM AAL-toxin or 5μM australifungin for 24 or 48 hrs and transferred to toxin-free media for 2 wks. Duckweed exposed to 24 hrs of FB_1 or AAL-toxin at 1μM recovered, whereas plants exposed to longer periods or higher concentrations did not. Duckweed subjected to 5μM of australifungin for up to 72 hrs recovered dramatically after removal of the toxin. To determine if FB_1 is a contact toxin or can be translocated throughout the plant, the movement of radiolabeled FB_1 was followed in jimsonweed, black nightshade and tomatoes. These results indicate that FB_1 applied to the surface of plants exhibits primarily contact activity. However, application of FB_1 to a wound site results in extensive damage to tissue above the point of application, indicating that FB_1 is xylem mobile. Fumonisins are potent phototoxins that act by a novel mechanism. Research is continuing to discover possible applications for fumonisins or their analogs in weed control

Fumonisin-Plant Interactions

none[Synopsis] The fumonisins are phytotoxins produced by fungi including Fusarium and Alternaria species infesting weeds, crops, soil and conifers. Fumonisin B_1 (FB_1) is also well-known as a mammalian toxin. FB_1 is a long-chain alkylamine with propanetricarboxylic moieties attached. It is structurally related to AAL-toxin, a phytotoxin first isolated from A. alternata f. sp. lycopersici, which causes stem canker disease on susceptible (asc / asc) tomatoes (Lycopersicon esculentum Mill.) . The susceptibility range of FB_1 and AAL-toxin has been investigated. Both toxins were initially thought to be host-specific to asc / asc tomatoes, but now are known to also be phytotoxic to weeds, specifically dicots. Symptoms include chlorosis, necrosis, stunting, and mortality. The fumonisins, especially FB_1, are produced by F. moniliforme, F. proliferatum and other Fusarium spp. of the Liseola section. Fumonisins were also isolated from A. alternata grown in liquid media and the mycelia and spores of A. alternata grown on solid rice media. FB_1 and AAL-toxin inhibit ceramide synthase, causing accumulation of free sphingolipid bases that are intermediates in the biosynthesis of sphingolipids, essential components of cell membrances. The accumulation of free sphingolipid bases is thought to result in the damage to cell components, cellular leakage, and chlorophyll loss. FB_1 and AAL-toxin were about 8 times more active than the recently-discovered ceramide synthase inhibitor australifungin. Duckweed was exposed to 1 μM FB_1, 1μM AAL-toxin or 5μM australifungin for 24 or 48 hrs and transferred to toxin-free media for 2 wks. Duckweed exposed to 24 hrs of FB_1 or AAL-toxin at 1μM recovered, whereas plants exposed to longer periods or higher concentrations did not. Duckweed subjected to 5μM of australifungin for up to 72 hrs recovered dramatically after removal of the toxin. To determine if FB_1 is a contact toxin or can be translocated throughout the plant, the movement of radiolabeled FB_1 was followed in jimsonweed, black nightshade and tomatoes. These results indicate that FB_1 applied to the surface of plants exhibits primarily contact activity. However, application of FB_1 to a wound site results in extensive damage to tissue above the point of application, indicating that FB_1 is xylem mobile. Fumonisins are potent phototoxins that act by a novel mechanism. Research is continuing to discover possible applications for fumonisins or their analogs in weed control

Effects of charcoal rot on soybean seed composition in soybean genotypes that differ in charcoal rot resistance under irrigated and non-irrigated conditions

Charcoal rot is a major disease of soybean (Glycine max) caused by Macrophomina phaseolina and results in significant loss in yield and seed quality. The effects of charcoal rot on seed composition (seed protein, oil, and fatty acids), a component of seed quality, is not well understood. Therefore, the objective of this research was to investigate the impact of charcoal rot on seed protein, oil, and fatty acids in different soybean genotypes differing in their charcoal rot susceptibility under irrigated and non-irrigated conditions. Two field experiments were conducted in 2012 and 2013 in Jackson, TN, USA. Thirteen genotypes differing in charcoal rot resistance (moderately resistant and susceptible) were evaluated. Under non-irrigated conditions, moderately resistant genotypes showed either no change or increased protein and oleic acid but had lower linolenic acid. Under non-irrigated conditions, most of the susceptible genotypes showed lower protein and linolenic acid but higher oleic acid. Most of the moderately resistant genotypes had higher protein than susceptible genotypes under irrigated and non-irrigated conditions but lower oil than susceptible genotypes. The different responses among genotypes for protein, oil, oleic acid, and linolenic acid observed in each year may be due to both genotype tolerance to drought and environmental conditions, especially heat differences in each year (2012 was warmer than 2013). This research showed that the increases in protein and oleic acid and the decrease in linolenic acid may be a possible physiological mechanism underlying the plant\u2019s responses to the charcoal rot infection. This research further helps scientists understand the impact of irrigated and non-irrigated conditions on seed nutrition changes, using resistant and susceptible genotypes

Contamination of sesame seed grown in Mississippi with aflatoxin, fumonisin, and mycotoxin-producing fungi

Four sesame varieties (S-34, S-35, S-38, and S-39) were planted in the Mississippi Delta in 2014 and 2015 at four nitrogen fertiliser application rates from 44.8 to 112 kg N/ha, and evaluated for grain yield and contamination by mycotoxins and toxigenic fungi. Variety S-35 had the highest yield in both years. Harvest seed moisture was not related to variety, because opposite results were obtained in the two years. N fertiliser application rate had no effect on yield or mycotoxin contamination of harvested seed in 2014, but significantly increased yield in 2015. Harvested sesame seed density was influenced by treatments (N rates and variety) with varietal differences occurring in the different years. While observed differences were small, even small differences could impact marketability. There was no significant effect of N fertiliser application rate, variety, crop year or interaction between them for contamination of harvested seed by aflatoxins, fumonisins, Aspergillus flavus or Fusarium verticillioides in cleaned and uncleaned harvested sesame seed. Similar results were obtained from trials conducted in the Florida Panhandle during 2015. In general, sesame seed is not susceptible to aflatoxin and fumonisin contamination. None of the mycotoxin levels observed in this study were significant in regard to human or animal health, but further testing is needed. This is the first report of fumonisin found in sesame seed. The results of this study indicate that sesame seed is a safe crop for growers and consumers