Grants and Contracts Details
Description
FHB resistance breeding programs for hard red winter wheat varieties adapted to Kentucky and the
southeastern U.S. are underway at the University of Kentucky. Population screening tools that have
been used in Kentucky include (i) visual assessment of disease severity, (ii) counts of infected ears or
spikelets postanthesis, and (iii) counts of Fusarium-damaged or -infected kernels at harvest. Reduction
of mycotoxins is a primary goal of our breeding program, but we have found that the correlation
between our assessments of FHB disease severity and DON contamination of the wheat at harvest is
relatively poor. The literature suggests that DON contamination depends on fungal biomass and fungal
genotype, host genotype, moisture levels, and host physiological status (e.g. nitrogen levels).
Although DON levels in the grain can be measured directly, different methods often result in different
estimates of contamination, and the most accurate techniques are too costly, inconvenient, or timeconsuming
for routine use in a breeding program. Two previous studies have reported that a direct,
quantitative measurement of F. graminearum biomass in the seed is highly correlated with levels of
mycotoxin contamination, and thus evaluation of fungal biomass may provide a useful new tool for
screening of breeding populations. Quantitative polymerase chain reaction (PCR) protocols for fungal
pathogens, including Fusarium spp., offer a convenient and cost-effective means for rapid analyses of
fungal biomass. For example, a quantitative assay for trichothecene-producing Fusarium spp. was
developed by European researchers based on real time (RT) PCR using the LightCycler® system and
primers specific for the tri5 gene sequence. Our objectives in this study include: I) Develop and
optimize a protocol for quantification of F. graminearum fungal biomass in developing and mature
wheat kernels based on the tri5 primers and SYBR-Green quantification using RT PCR in the highly
automated and affordable SmartCycler® system. 2) Correlate fungal biomass with DON levels in
kernels of three different breeding lines from the Kentucky breeding program that are highly resistant,
moderately resistant, and susceptible to FHB 3) Use cytological methods to relate fungal development
and localization over time to levels of DON and symptom development in infected seeds from
resistant, moderately resistant, and susceptible wheat varieties. Our goals are 1) to develop useful and
practical tools for screening of germplasm for the Kentucky FHB breeding program, and 2) to improve
our basic understanding of the mechanism of seed infection by F. graminearum and its relation to FHB
symptoms and DON production. Although two recent European studies have already demonstrated
high correlations between F. graminearum biomass in wheat seeds, measured by quantitative PCR,
and DON contamination, we think it will be useful to validate these results and develop a PCR
quantification protocol for routine use in the breeding program in Kentucky. It is likely that
environmental and other variables have different effects on the relationship between fungal biomass
and DON production in different locations, there is considerable value in optimizing screening tools
for each site and for each set of adapted genotypes. Comparisons of the results of parallel
investigations in divergent systems will allow recognition of common themes. This in turn will aid in
transfer of this technology to new sites and additional genotypes.
Status | Finished |
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Effective start/end date | 4/11/06 → 4/11/06 |
Funding
- US Department of Agriculture
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