Influence of total nonstructural carbohydrates on snow mold tolerance in winter wheat

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" Influence of total nonstructural carbohydrates on snow mold tolerance in winter wheat "
F. Mohammad R. S. Zemetra

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1113275
Doc. No	:	TLpq304107121
Main Entry	:	F. Mohammad
	:	R. S. Zemetra
Title & Author	:	Influence of total nonstructural carbohydrates on snow mold tolerance in winter wheat\ F. MohammadR. S. Zemetra
College	:	University of Idaho
Date	:	1994
student score	:	1994
Degree	:	Ph.D.
Page No	:	88
Abstract	:	Snow mold is an important disease of winter wheat in the Pacific Northwest, USA. It is most prevalent when snow covers unfrozen soil for long periods of time. Plants capable of accumulating large amounts of total nonstructural carbohydrates (TNC) before snow fall survive infection by psychrophilic fungi. Studies were conducted to ascertain the heritability of TNC in two hard red winter wheat populations. A preliminary study was arranged with genotypes of known tolerance to snow mold in the greenhouse. An experiment using randomized complete block design with four replications was planted in greenhouse and then transferred to a growth chamber at 4C for imposing fall conditions for TNC accumulation. TNC was determined in all treatments by using the Smith (1969), Weinmann (1947) and Nelson (1944) methods standardized for this project. Statistical analysis showed significant differences for TNC accumulation among genotypes. In growth chamber studies, snow mold tolerant genotypes accumulated significantly higher TNC than susceptible genotypes, confirming the positive correlation between TNC and snow mold tolerance. To ascertain the narrow-sense heritability of TNC, field studies were conducted with lines derived from two hard red winter wheat populations. Three experiments were planted in 5x5 balanced square lattice designs with six replications at Tetonia, Idaho, during 1992-93 and 1993-94. Plant samples were collected prior to snow fall in all experiments and in one experiment, after snow melt, for TNC determination. Genotypes were highly significant (P = 0.01) for TNC, spring stand percentage and plant count in all of the experiments. Genotypic and phenotypic correlations among TNC, stand percentage and plant count were calculated. Narrow-sense heritability was determined for TNC, spring stand percentage and plant count. Irregular infection by Typhula idahoensis occurs in the field in most years in high snow fall areas. The method standardized for TNC extraction and quantification can effectively evaluate 100 plant samples per week. The fall TNC levels were less influenced by environment compared to spring TNC content. The narrow-sense heritability estimates for fall TNC were higher than spring survival. TNC may be used in selection of winter wheat genotypes derived from 'Manning' 2/'Survivor' population for snow mold tolerance and there was no genotypic correlation between TNC and spring survival in 'Blizzard'2/'Sumner' population. Further research needs to be conducted on the specific sugar profiles and degree of polymerization of fructan. The technique used in this study for snow mold screening was found to be genotype dependent.
Subject	:	Agronomy
	:	Agronomy
	:	Biological sciences
	:	Genetics
	:	Plant pathology
	:	Typhula idahoensis