The phenolic acid profiles of six cultivars of wheat with known tolerance to Fusarium head blight were evaluated during plant development from anthesis through maturity. Analysis by HPLC of grain at anthesis revealed that p-coumaric and ferulic acid were the two principal phenolic compounds present. The effect of these two phenolic acids on Fusarium species was evaluated in vitro. Both phenolic acids demonstrated significant reductions (p < 0.05) of Fusarium species growth at all concentrations tested. Ferulic acid is the primary phenolic acid in grain at all stages of development, and its concentration increased steadily during grain development prior to a 50% decrease during grain ripening. The accumulation of ferulic acid synthesis from anthesis until approximately 20 days after anthesis appears related with cultivar resistance to Fusarium. Concentrations of ferulic acid in the grain were similar at maturity, implying that the end-use quality would be similar for both resistant and susceptible cultivars.

Campbell and Lipps, 1998;Yang et al., 1999). Resistance expression often differs among envi-The development of wheat (Triticum aestivum L.) cultivars resis-

Progeny from three crosses of adapted hard red spring wheats (Triticum aestivum L. em Thell.) and a common exotic parent, ‘Rageni 15’, were grown in replicated field experiments for 3 years in Minnesota. Agronomic and physiologic traits were measured to evaluate Rageni 15 as a source of high grain protein and to appraise selection criteria for the combination of grain yield and grain protein percentage.The comparison of actual vs. predicted grain protein percentage, based on the linear regression of grain protein percentage on grain yield, indicated the Rageni 15 had low yield and grain protein percentage, and did not contribute higher grain protein to its progeny.Grain yield and grain protein percentage were negatively correlated (r = −0.48), and no single selection criterion proved of value in improving both traits simultaneously. Improvement of grain protein percentage with reduction of grain yield was obtained upon selection for high deviants from the linear regression of grain protein percentage on grain yield, protein content per kernel, and grain protein percentage. Selection for grain protein per se was most effective in improving this trait.Nitrogen harvest index and harvest index were correlated (r = −0.54) and both were positively correlated with grain yield. Grain protein percentage was negatively correlated with harvest index (r = −0.54), but it was not correlated with N harvest index (r 0.00). Therefore, N harvest index could prove useful as a selection criterion to improve grain yield while maintaining grain protein percentage

Breeders of hard red spring wheat (Triticum aestivum) are attempting to incorporate resistance to scab, caused by Fusarium graminearum. In artificially inoculated, replicated field plots, 37 wheat entries (inbred lines or cultivars) were evaluated for 3 years and an additional 60 entries for 2 of the 3 years for incidence (percent spikes infected), severity (percent infected spikelets within infected spikes), and disease index (percent infected spikelets in 50-spike sample). From year to year, entries had similar index values, with coefficients of determination (r 2) ranging from 0.59 to 0.78, with a mean of 0.73. Entries appeared slightly more similar from year to year for incidence than for severity, although both measures of disease had highly significant r 2 values. Incidence and severity were highly correlated in the wheat germ plasm examined; r 2 values in single years ranged from 0.51 to 0.67, with a mean of 0.64. A representative subset of 22 entries was included for a fourth year. None of the measures of disease in year 4 correlated with their counterparts in any of the first 3 years. This loss of repeatability may have been caused by severe lodging or by high temperatures during the evaluation period that accelerated disease progress and wheat maturity during year 4. Incidence and severity remained correlated in year 4 (r 2 = 0.60).

Increasing kernel weight has been proposed as a method to increase flour extraction in spring wheat (Triticum aestivum L.). Recurrent selection was initiated to increase kernel weight while maintaining genetic variation for the unselected traits. Our objectives were to determine (i) genetic gain for kernel weight after eight cycles of selection, (ii) the indirect effects of the selection for kernel weight on other agronomic traits, kernel morphology, milling fractions, and grain protein concentration, and (iii) the level of genetic variability among lines within selection cycles for kernel weight and unselected traits. Ten lines, selected for high kernel weight, were originally intermated to form the base population. About 20 F2 plants with the highest kernel weight were selected (∼2% of the population), and about three of their F3 progeny were intermated to form the next cycle. This procedure was repeated for eight cycles, with an average of 60 crosses per cycle. Forty random lines from each cycle were used to evaluate agronomic traits in three environments. Kernel weight increased linearly at about 4.5% cycle−1 Cycle means did not differ for plant height and grain yield, but tillers per square meter and kernels per spike decreased 2.4 and 1.6% per cycle, respectively. Spikelets per spike, kernels per spikelet, test weight, and days to heading decreased, whereas spike length increased in response to selection for kernel weight. The proportion of bran and shorts decreased, and flour extraction and grain protein concentration increased 0.58 and 0.16% cycle−1, respectively. No clear trend towards decreased genetic variance for kernel weight was observed since gain was linear over eight cycles. The observed gain from selection and heritability estimates point to kernel weight being controlled by several genes with small effects. Selection for increased kernel size in this population resulted in increased flour yield.