Data/hora: 21/06/2024 09:16:02

Biblioteca(s): 	Embrapa Meio Ambiente.	
Data corrente: 	12/07/2002	
Data da última atualização: 	31/05/2011	
Autoria: 	STADNIK, M. J.	
Título: 	Induction of resistance in wheat by a benzothiadiazole derivative against the powdery Mildew (Blumeria graminis f. sp. tritici): practical aspects and mechanisms of action.	
Ano de publicação: 	1999	
Fonte/Imprenta: 	Stuttgart: Verlag Ulrich E. Grauer, 1999.	
Páginas: 	139p.	
ISBN: 	3-86186-261-1	
Idioma: 	Inglês	
Notas: 	Tese Doutorado.	
Conteúdo: 	The resistance inducer BTH (benzo [1,2,3] thiadiazole-7-carbothioic acid S-methyl ester) was studied in wheat in field trials during three years. While the BTH-treatment at the end of the tillering stage (GS 28) reduce the powdery mildew severity more effectively than when applied in the mid of tillering (GS 25), the earlier application led to higher grain yields. The fungicide cyprodinil (GS 31) controlled the powdery mildew more efficiently than BTH. Effectiveness of BTH to control Septoria tritici disease BTH was variable, and dependent of the application time and year. In contrast, the fungicides azoxystrobin and NAD 21100 F (tryfloxistrobin + propiconazole) markedly reduced the S. tritici disease severity. While all tested fungicides increased the grain yield of wheat, the combinations of fungicides with BTH did not show any additional effect on yield, although sometimes reduction of the foliar diseases was improved. The epidemiological development of the powdery mildew was differently affected by BTH on the cvs. Monopol (susceptible), Rektor (pm5 gene for resistance) and Zentos (resistant). Foliar sprays of kinetin or urea during tillering incfreased the powdery mildew severity. However, the highest yield increase by BTH was found when the inducer was applied in combination with 85 urea solution. A more erect leaf position was only observd in one experimental year, suggesting that environmental conditions may play an important role in the expression of these growth habit modifications. While the surface of flags leaves of BTH-treated wheat plants of cv. Monopol grown at a lower nitrogen level in an outdoor pot experiment was drastically reduced, their cross sections were thicker. This effect was especially visible in the vascular bundle region. Although inhibition of the leaf elongation was obvious only in plants growing at the lower level of nitrogen, similar erect foliar position was also observed at the higher nitrogen level. An accumulation of lignin in the vascular bundle region of flag leaf tissues showing a more erect position was detected by both staining methods and thioglycolate assay. Also an enhanced content of wall-bound phenolic compounds was found by HPLC in leaves of BTH-treated plants. Translocation studies at GS 73 revealed that in BTH-treated plants a higher percentage of C14-labeled metabolites was transported from flag leaf into the ear compared to the untreated plants. However, at GS 84 a smaller quantity of metabolites was translocated into the ear of treated plants than in the controls. Furthermore, pigment determinations of flag leaves at GS 84 of the treated plants showed that contents of chlorophyll a+b and carotenoids were slightly reduced compared to those of control plants. The de novo synthesis of phenolic compounds was studied in the cv. Monopol and cv. Zentos under laboratory conditions. Two peaks of phenylalanine ammonia-lyase (PAL) activity were detected. The first occurred 4 h after inoculation with Bgt, coinciding with the primary germ tube formation and the second at 12 hai, during the appressorium formation. In both cultivars, BTH caused a significant increase of the PAL-activity at 12 hai, but this effect was more evident in the cv. Monopol than in the cv. Zentos. The intensity of localized autofluorescence at the attempted penetration site was also modified by BTH. In epidermial cells of BTH-treated plants of cv. Monopol, autofluorescence was more frequent and intense 12 and 18 hai in comparison to the untreated control. Autofluorescence at attempted penetration sites was clearly higher in cv. Zentos but only slightly increased by BTH. Increase in PAL-activity was associated with enhanced autofluorescence in BTH-treated plants, suggesting that both phenomena are closely associated. In vitro treatment of leaves with AOPP (a PAL-inhibitor) reduced the localized autofluorescence at the attempted penetration sites and the accumulation of wall-bound cell phenolic compounds (i.e. ferulic acid and coumaric acid) which resulted in increase of fungal penetration efficiency. However, lignin (polyphenolics) content was not modified by BTH-treatment. Activity of peroxidase was significantly enhanced 18 hai, but not of cinnamyl alcohol dehydrogenase (CAD). Inhibition of CAD-activity did neither affect localized autofluorescence nor the penetration efficiency of the powdery mildew fungus. Results suggested that phenylpropanoid materials are biosynthesized de novo and more rapidly accumulated at the attempted penetration site causing a redution of the Bgt-penetration efficiency in BTH-treated wheat plants.	
Palavras-Chave: 	Benzothiadiazole derivative; Fungus; Induction of resistance; Plant diseases.	
Thesaurus Nal: 	Blumeria graminis; powdery mildew; wheat.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Meio Ambiente (CNPMA)	
Exemplares: 	CNPMA - (4288-1) - ADD - TS - PP - 0462 -  - 2002.00462 - DIS