Browsing by Subject "Zearalenon"

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Genetics of resistance to ear diseases and mycotoxin accumulation in the pathosystems maize/Fusarium and wheat/Fusarium
(2010) Messerschmidt, Martin; Miedaner, Thomas
Infection of ears of maize with Fusarium graminearum (FG) reduces yield and, more important, contaminate the harvest with mycotoxins. F. verticillioides (FV) is an economically important cause of ear rot. Among other mycotoxins, FV produces the fumonisins (FUM) and FG produces deoxynivalenol (DON) and zearalenone (ZEA). All three mycotoxins are harmful to humans and animals. Therefore, the European Union released legally enforceable limits. One alternative to reduce ear rot severity and mycotoxin concentrations is breeding and growing varieties resistant to Fusarium infections. However, few is known about breeding parameters for resistance to Fusarium infections and mycotoxin accumulation in European maize breeding material. The main objective of this thesis was to draw conclusions for breeding of resistance to ear rot and mycotoxin accumulation with special attention on three European maize maturity groups. We investigated methodical aspects like (1) the comparison of natural and artificial inoculation to evaluate ear rot resistance and (2) the necessity of separate testing of FV and FG. Furthermore, quantitative-genetic parameters like heritabilities and correlations were estimated to draw conclusions about (3a) genetic variation in line and testcross performance and the relationships (3b) between ear rot severity and mycotoxin concentrations in lines and testcrosses and (3c) between line and testcross performance. Three maturity groups (early, mid-late, late) each comprising about 150 maize inbred lines were evaluated for ear rot resistance to FV. The same genotypes of the early maturity group were additionally evaluated for resistance to FG in separate, but adjacent trials. Field evaluation was conducted in two to six environments with silk channel inoculation and natural infection, respectively. In the late maturity group kernel inoculation was conducted additionally. Out of the 150 lines, 50 to 60 lines per maturity group were crossed with two unrelated testers of the opposite heterotic group. The concentrations of toxins FUM, DON and ZEA of the chosen lines and their testcrosses were analyzed by immunotests. Despite significant genotypic differences among the inbred lines after inoculation or natural infections, inoculation was found to be superior due to easier visual differentiation and increased accuracy. Therefore, inoculation should be conducted. In the late maturity group silk channel inoculation (simulating infection over the silks) and kernel inoculation (simulating secondary infection after wounding) were appropriate since both caused similar ear rot severity. However, both inoculation methods should be tested separately due to only moderate correlations between them. In the early maturity group resistance to FG or FV should be tested separately due to moderate correlations. Significant genotypic variances in large sets and subsets of lines and also in testcrosses revealed that there is genetic variation in all maturity groups and also within heterotic groups. In the flint group less lines were resistant to FV and FG than in dents indicating that resistance needs improvement, i.e. by introgression of resistance alleles followed by recurrent selection. Significant genotype x environment interactions may complicate selection and, therefore, multi-environmental trials are required for an accurate selection. High genotypic correlations between ear rot rating and mycotoxin concentrations were found among lines and testcrosses. The cost efficient indirect selection for mycotoxin concentrations based on ear rot rating could increase response to selection by testing more genotypes and/or in more test environments assuming a fixed budget. This should increase selection intensity and/or heritability. Moderate genotypic correlations between line and testcross performance were. One moderately to highly susceptible tester is sufficient due to high genotypic correlations between testcrosses of different testers. Both indicates a mainly additive gene action, but also non-additive gene action may play a role in some crosses. Selection for testcross performance based on line performance was less effective when calculating relative efficiencies. Different scenarios have been identified: (1) In Central Europe mainly resistance to ear rot in lines needs to be tested to ensure high seed quality, whereas resistance in testcrosses is not important due to low natural infection. (2) In Southern Europe, where high natural infections occur regularly, parallel selection for resistance to ear rot in lines and testcrosses is important. One susceptible tester should be used for creation of testcrosses. For selection in lines all parental lines should be inoculated but only lines selected out of testcrosses for agronomic traits would be rated afterwards saving resources. This is feasible due to later harvest date of lines than of testcrosses.
Untersuchungen zur Belastung von Getreidestroh mit Fusarium-Toxinen und Ochratoxin A in Deutschland mit Verfügbarkeitsstudien
(2011) Sondermann, Sarah; Drochner, Winfried
In a two year enduring nationwide screening experiment, the occurence of 13 trichothecene toxins, as well as zearalenone (ZEA) and ochratoxin A (OA) in crop straw was examined, in order to enable a better assessment of the risk of exposure for farm animals through the intake of the straw. The straw samples were taken according to the ?Futtermittelprobenahme - und Analysenverordnung? and the attached questionnaires were filled out in cooperation with the farmers. Through correlation of the toxin contents with the information of the questionnaire, hints for the influence of measures of cultivation and crop farming on the toxin content of the straw were sought. Additionally, through correlation of the toxin contents with weather data, hints for the influence of the weather on the toxin content of the straw were sought. In plus, information on the occurence of masked toxins in straw should be obtained. With the help of the extensive, nationwide taking of samples, implemented by official samplers, these samples illustrate a representative average for Germany throughout the two years of investigation. A screening of straw samples of different sorts of crop from 2007 and 2008 were examined on a spectrum of 14 Fusarium toxins as well as OA, a macroscopic result for the samples was raised. A statistic evaluation of the data was made. Throughout the two years of investigation, 80 samples of wheat straw, 79 of barley straw, 11 of oat straw, 12 of rye straw, 12 of triticale straw , 1 of spelt straw and 6 of an unknown sort of straw were examined. The macroscopic results for the screening samples revealed a mostly positive figure concerning the food value, on the other hand the figure concerning the average hygienic status showed in 2007 and 2008 an evidence for slight or even distinct hygienic deficiencies. The pollution of the straw samples with a spectrum of Fusarium toxins was verified. Because the average assertained number of cooccuring toxins in the samples was 3, the possibility of a multi toxin exposure of the straw must be considered. DON was concerning the frequency of occurance and the content the dominating toxin. It occured in 83 % of the samples verifiable with an average content of 1234 µg/kg, a median content of 439 µg/kg and a range of variation of 23253 µg/kg. The trichothecenes HT-2, T-2, T-2,4, SCIRP, NIV, 15-ADON and 3-ADON were verifiable in 55, 37, 9, 9, 32, 21 and 9 % of the 201 analysed samples. FUS-X, MAS, DAS, T-2,3 and OA were detected in less than 5 % of the samples, NEO in none of them. ZEA was provable in 46 % of the 201 samples, with contents between 7 and 767 µg/kg. OA was detected in only one of the 201 straw samples, consequently there is no pollution by this storage toxin expected. A different occurence of trichothecene was observed in the 2 years of investigation. In the first year the contents of NIV, 15-ADON and ZEA were higher than in the second year. HT-2 and T-2 were significant or rather tendential existent in a higher number in the year 2008. Altogether, the pollution of the straw was higher in the year 2007, recognizable through the sensorial evaluation as well as trough the analysis of the Fusarium toxins. Wheat- and barley straw exhibited a pollution by different spectra of trichothecene, whereby the results of the two years of investigation coincided well. All in all, significant different contents of the toxins DON, 15-ADON and ZEA with higher contents in the wheat straw and the type-A trichothecenes HT- and T-2 in the barley straw could be detected. These differences in the spectrum of toxins could arose from a population of different species of Fusarium. . The high amounts of samples of wheat- and barley straw allowed a detached evaluation concerning the influences of cultivation and crop farming on the two sorts of straw on the one hand and on the other hand a geographic distribution of the toxins within Germany. The assay of the samples of straw concerning masked toxins were made with the help of chemical and enzymatic hydrolysises and an in vitro - model, which simulates the conditions in the gastro-intestinal tract of a pig. The statistic evaluation of the single experiments delivered no significant differences between the varieties with treatment compared to the varieties without treatment. So a release of possibly existing masked toxins was not verifiable with the applied methods.