| Wheat head blight (WHB) is one of the most serious wheat diseases worldwide. This disease was generally caused by Gibberella zeae (Schwein) with anamorphic state Fusarium graminearum Schwabe. F. graminearum pathogen may produce toxin deoxynivalenol (DON) during wheat growth stage. So this toxin are existed in wheat head blight occurs areas worldwide in a wide variety of wheat kernels, foods, feeds and other commodities. Chronic consumption of low levels of DON toxin may result in impaired immunity and decreased resistance to infectious diseases. So researches about how to control WHB, reduce DON toxin in wheat grain, may increase wheat production and benefit to people health. Chemical control method is one of the most important methods to control WHB, carbendazim has been being most popular fungicide to control WHB in China for more than 30years, it is important to monitoring frequency of carbendazim resistant subpopulation of F. graminrarum in practice. So the major content of the present study are that,1. Effects of wheat cultivars resistance to Fusarium graminearum and Fusarium-damaged kernels on toxin accumulation in grains: 2.Estimation.of wheat head blight economic threshold according to DON concentration; 3. Incidence of trichothecenes in wheat-based foodstuff from China.4. Studies on monitoring and evolvement of resistance to carbendazim of Fusarium graminearum; 5. Temperature and nutrition sensitivity of carbendazim resistance in Fusarium graminearum from wheat head blight; and 6. Studies on the changes of trichothecenes contimanation in wheat kernels during storage period1. Effects of wheat cultivars resistance to Fusarium graminearum and Fusarium-damaged kernels on toxin accumulation in grainsSix single spore isolates of F. graminearum were respectively inoculated to 6 different resistant wheat cultivars. Deoxynivalenol (DON) contamination in the grains from different resistant cultivars grown on the same trial condition differed insignificantly (p=0.05) under the same sum of inoculum, same percentage of FDK and same disease kernel grade (DKG). While relationship of 3-acetyldeoxynivalenol (3ADON) or 15-acetyldeoxynivalenol (15ADON) content among resistant wheat cultivars were non-significant. However, DON content of the same cultivar under the control of same cultural condition and the same strain correlated significantly positively with the FDK. Theoretical curve equation of main toxin concentration(Y) and FDK (X=0-20%) was Y=3.82X0.86 (R2=0.93 F=219.83 P<0.0001), which was suitable for interactions between a strain 2021 and winter wheat cultivar WangshuiBai, and Y=1.1X1.32 (R2=0.95, F=325.04, P<0.0001, X= 0～50%) for interaction between strain B4-1 and winter wheat cultivar DH050. DON content in grains of the tested wheat cultivars varied with inoculated strains and FDK, but not with the resistance level of the cultivars to F. graminearum.2. Estimation of wheat head blight economic threshold according to DON concentrationIn order to establish WHB economic threshold according to DON concentration, corelationship between WHB disease severity, yield losses, Fusarium damage kernel (FDK) and toxin DON concentration (DON) in wheat grain under natural and inoculated condition were studied in this paper. Close relationships between the percentage of FDK and the yield of wheat were observed (r2=0.45-0.92) with linear relationship. Close linear relationship (R2=0.75-0.77) between FDK and DON were also found in random selected disease grains in natural condition. The economic threshold of WHB was 2.8-7.5% FDK or disease index 2.4-8.7% according to yield losses. While according to toxin pollution in the grain course price losses, the economic threshold in susceptible wheat cultivars were 1.1%—3.1%of FDK or disease index 0.4—3.2%.3. Incidence of trichothecenes in wheat-based foodstuff from ChinaThe occurrence of trichothecene toxins was determined in different kinds of wheat-based foods (convenience noodles, biscuits, bread, and cakes) in Nanjing, China. A total of 74 commercially available samples were collected from the supermarkets in Nanjing from September 2006 to April 2007. Three trichothecenes named deoxynivalenol (DON),3-acetyldeoxynivalenol (3ADON) and 15-acetyldeoxynivalenol (15ADON), were detected and quantified by gas chromatography with electron capture detection. The incidence of DON,3ADON and 15ADON were 73.0,8.1 and 23.0%, respectively, the content ranges were 0-11.38,0-1.47 and 0-2.06 mg/kg, respectively, and the averages content were 1.80,0.06 and 0.11 mg/kg in all samples, respectively. The average DON contents in convenience noodles, biscuits, bread and cakes were 1.95,2.25,0.62 and 0.31mg/kg, respectively. Thirty-seven of 74 samples contained more than 1 mg of DON/kg, which is the regulatory limit defined by the Chinese government.4. Studies on monitoring and evolvement of resistance to carbendazim of Fusarium graminearumSeverity of wheat head blight caused by Fusarium graminearum in Jiangsu province was investigated from 1994 to 2007 and frenquency of carbendazim (MBC) -resistant isolates of Fusarium graminearum collected in fields of Jiangsu was monitored consecutively from 1985 to 2008. Correlation among frequency of MBC-resistant, Severity of wheat head blight and weather fators affecting the disease was analysed. The result showed that the years of moderate epidemic of WHB in counties (including Jiangpu) of south Jiangsu accounted for 30.8% in the investigated 13 years, but accounted for 7.7%-15.4% in the counties (including Ganyu, Gaoyou) of north Jiangsu where the disease occurred moderately. Close relationship were found among change rate of field MBC—resistant isolate of F. graminearum (Y), WHB occurrence severity in Jiangsu Province (X1), WHB disease index (X2) and rainy days of last twenty days of April (X3) in Jiangsu Province with correlation equation Y=1.49X1+0.25X2- 0.02X3-1.59. MBC-resistant isolates increased as WHB occurred moderately or severely and MBC was applied more extensively, vice versa. MBC still has played important role in controlling WHB in agricultural production.5. Temperature and nutrition sensitivity of carbendazim resistance in F. graminearum from wheat head blightTo understand temperature sensitivity of carbendazim resistance in F. graminearum from wheat head blight may benefit chemical control of WHB.160 MBC resistant single spore isolates of F. graminearum in natural field collected in Jiangsu during 2003-2007, were analyzed for its ability to grow at 10℃,15℃,20℃,25℃,30℃and 35℃on potato dextrose agar (PDA) with or without carbendazim.22 high levels of resistance isolates and 9 low levels of resistance isolate were cold sensitive according to this experiment.19% of total carbendazim resistant isolates of F. graminearum were cold sensitive while 81% of isolate were not temperature sensitive.6. Studies on the changes of trichothecenes contimanation in wheat kernels during storage periodIn order to study chang law of trichothecenes contimanation in wheat kernels during storage in normal condition, wheat kernels containing trichothecenes during storaged in one year period were detected and quantified by gas chromatography with electron capture detection pre-menstrual. The trichothencens concentration had no significant difference duing the storage period in this study. |
PDF Full Text Request