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United States Department of Agriculture

Agricultural Research Service

Title: Panel Discussion: 4th Annual Fumonisin Elimination Workshop for Multicrop Workshop-Afllatoxin/fumonisin/fungal Genomics.

Author
item Riley, Ronald

Submitted to: Multicrop Aflatoxin and Fumonisin Elimination and Fungal Genomics Workshop-The Peanut Foundation
Publication Type: Proceedings
Publication Acceptance Date: December 1, 2003
Publication Date: March 15, 2004
Citation: Riley, R.T. 2004. Panel discussion: 4th annual fumonisin elimination workshop for multicrop workshop-afllatoxin/fumonisin/fungal genomics.. Multicrop Aflatoxin and Fumonisin Elimination and Fungal Genomics Workshop-The Peanut Foundation. October 12-15, 2003, Savannah, Georgia. p.22-23.

Interpretive Summary: Panel Members: Pat Dowd, Ron Riley, Ida Yates, Leilani Robertson, Charles Woloshuk, Ken Voss, Xiangcheng Zhu and Robert Butchko. The 4th Fumonisin Elimination workshop was moderated by Gerald Donaldson of the Texas Corn Producers Board. There were eight presentations covering a wide variety of topics ranging from the development of novel methods for the detection and monitoring of toxigenic Fusarium species in developing corn to the efficacy of processing methods to reduce fumonisins in foods. The following is a brief summary of each presentation. The first speaker was Pat Dowd who reported on the use of a predictive molecular method for monitoring Fusarium in the field. The method was used to augment predictions made by a computer program for forecasting mycotoxin presence in Midwest corn. Ron Riley reported on the results of a three year survey of fumonisin levels in corn from the highlands (>1700 m) and lowlands (<360 m) in Guatemala. The results showed that the occurrence of fumonisins and Fusarium verticillioides in highland corn was quite rare, whereas, in corn from the lowlands they were both quite common. Ida Yates summarized the results of field studies comparing the effects of F. verticilliodes infection on the performance of two corn genotypes. The seed borne infection was not detrimental to the performance of either genotype. Leilani Robertson has identified two maize inbred lines as potential sources of resistance to both fumonisin accumulation and ear and kernel rot. Promising quantitative trait loci (QTLs) for ear rot resistance and resistance to fumonisin accumulation have been identified. Charles Woloshuk reported the results of microarray analysis in F. verticillioides that identified potential candidate genes having roles in regulating fumonisin biosynthesis under different environmental conditions. Ken Voss showed that preparation of corn-based foods using alkali processing (nixtamalization) reduces fumonisin in the final product, whereas, baking and frying have little effect. In addition, cooking does not increase the toxicity of the final products indicating that unknown, biologically active fumonisins were not produced during processing. Xiangcheng Zhu reported on recent investigations to develop a model system for studying the biosynthesis of fungal polyketides (like fumonisin). Two mutants have been identified for FUM5, a polyketide synthase in F. verticillioides and it was shown that domains from other fungi could be interchanged and the resulting genes retained functionality. Robert Butchko reported on studies of gene deletion studies to determine the function of FUM7, FUM10, FUM1 and FUM14 of the FUM gene cluster. It was found that all four genes were involved in the addition of the tricarballylic acid moieties to the fumonisin backbone. Following the presentation there was the reading of a poem by Anne Desjardin paying homage to Ron Plattner, who recently retired from USDA-ARS after many many years of productive work in the field of mycotoxicology. It was generally agreed that Ron's contributions to our understanding of fumonisins and other Fusarium toxins has been immense and that he will be sorely missed. Following the tribute to Ron, Charles Woloshuk and other panel members were asked to comment on the practical implications of their molecular work as it pertains to reducing fumonisins in corn. Charles pointed out that understanding the factors that regulate toxin production will lead to the identification of molecular targets in both the fungus and the plant that can be used to improve resistance to fumonisin accumulation and can also be used to predict what environmental factors are most important in regulating fumonisin production in the field. Robert Butchko and Xiangcheng Zhu added several comments along the same line and pointed out that identification of the genetic

Technical Abstract: Panel Members: Pat Dowd, Ron Riley, Ida Yates, Leilani Robertson, Charles Woloshuk, Ken Voss, Xiangcheng Zhu and Robert Butchko. The 4th Fumonisin Elimination workshop was moderated by Gerald Donaldson of the Texas Corn Producers Board. There were eight presentations covering a wide variety of topics ranging from the development of novel methods for the detection and monitoring of toxigenic Fusarium species in developing corn to the efficacy of processing methods to reduce fumonisins in foods. The following is a brief summary of each presentation. The first speaker was Pat Dowd who reported on the use of a predictive molecular method for monitoring Fusarium in the field. The method was used to augment predictions made by a computer program for forecasting mycotoxin presence in Midwest corn. Ron Riley reported on the results of a three year survey of fumonisin levels in corn from the highlands (>1700 m) and lowlands (<360 m) in Guatemala. The results showed that the occurrence of fumonisins and Fusarium verticillioides in highland corn was quite rare, whereas, in corn from the lowlands they were both quite common. Ida Yates summarized the results of field studies comparing the effects of F. verticilliodes infection on the performance of two corn genotypes. The seed borne infection was not detrimental to the performance of either genotype. Leilani Robertson has identified two maize inbred lines as potential sources of resistance to both fumonisin accumulation and ear and kernel rot. Promising quantitative trait loci (QTLs) for ear rot resistance and resistance to fumonisin accumulation have been identified. Charles Woloshuk reported the results of microarray analysis in F. verticillioides that identified potential candidate genes having roles in regulating fumonisin biosynthesis under different environmental conditions. Ken Voss showed that preparation of corn-based foods using alkali processing (nixtamalization) reduces fumonisin in the final product, whereas, baking and frying have little effect. In addition, cooking does not increase the toxicity of the final products indicating that unknown, biologically active fumonisins were not produced during processing. Xiangcheng Zhu reported on recent investigations to develop a model system for studying the biosynthesis of fungal polyketides (like fumonisin). Two mutants have been identified for FUM5, a polyketide synthase in F. verticillioides and it was shown that domains from other fungi could be interchanged and the resulting genes retained functionality. Robert Butchko reported on studies of gene deletion studies to determine the function of FUM7, FUM10, FUM1 and FUM14 of the FUM gene cluster. It was found that all four genes were involved in the addition of the tricarballylic acid moieties to the fumonisin backbone. Following the presentation there was the reading of a poem by Anne Desjardin paying homage to Ron Plattner, who recently retired from USDA-ARS after many many years of productive work in the field of mycotoxicology. It was generally agreed that Ron's contributions to our understanding of fumonisins and other Fusarium toxins has been immense and that he will be sorely missed. Following the tribute to Ron, Charles Woloshuk and other panel members were asked to comment on the practical implications of their molecular work as it pertains to reducing fumonisins in corn. Charles pointed out that understanding the factors that regulate toxin production will lead to the identification of molecular targets in both the fungus and the plant that can be used to improve resistance to fumonisin accumulation and can also be used to predict what environmental factors are most important in regulating fumonisin production in the field. Robert Butchko and Xiangcheng Zhu added several comments along the same line and pointed out that identification of the genetic basis of toxin production and resistance are key to developing control strategies and will also assist in developing molecular markers to be used in breeding for resistance. Don White asked Ken Voss and Ron Riley to discuss the current status of the studies suggesting a possible link between human neural tube defects and fumonisin exposure in China. Ken briefly summarized recent studies and concluded that there is currently no convincing evidence that the fumonisins can cause NTDs in humans, however, NTDs have been produced in mice and fumonisins can inhibit the transport and alter the processing of folate. Folate deficiency is a known risk factor for NTD in China and elsewhere. Leilani Robertson and Ida Yates were asked why the fumonisin levels are always high in corn grown in the southeastern US. There was no easy answer but it was pointed out by Don White and others that maybe is was an artifact of the fact that corn is more intensely monitored in southern states, whereas, in the Midwest, the corn goes from the field to the elevator and is not analyzed until it reaches its final destination. Charles Woloshuk raised the question about the correlation between ear and kernel rot and fumonisin levels. Leilani commented that in North Carolina you could have 30 ppm FB1 and no evidence of rot. Charles expressed skepticism and Anne Desjardin agreed. Don White supported Leilani's observation and added that the proof was in the fact that the growers rate the corn as clean and yet high levels of fumonisin can be found when analyzed. Gary Payne agreed with Don and stated that even when aflatoxins and fumonisins are high there are cases where there is no evidence of rot or symptoms and that that has been the case for many years! The question of the correlation between the degree of rot and fumonisin levels was left unresolved. The discussion session ended with Pat Dowd updating the current status of the predictive computer program that has been used successfully and is in the process of being converted to a more user friendly format that will help farmers make decisions aimed at reducing aflatoxin and fumonisin levels in harvested corn in the Midwest.

Last Modified: 4/23/2014
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