Effects of the Fungicide Propiconazole on Agronomic and Quality Traits of Hulled and Hulless Barley

The hypocholesterolemic effect of hulless waxy barley (Hordeum vulgure L.) has increased its use in food products. Hulless cultivars currently grown in the Upper Midwest U.S. barley growing region are susceptible to a foliar disease, spot blotch, that can severely reduce yield. Spot blotch and kernel blight generally occur in the eastern area of the region; thus, hulless barley production is limited to the western area. Research on chemical control of spot blotch and kernel disease in hulless barley genotypes grown in the Upper Midwest has not been conducted. The objectives of this study were to determine whether natural field infections of the pathogen responsible for causing spot blotch and partly responsible for causing kernel blight similarly affect kernel and flour brightness of hulled and hulless barley genotypes, and to determine whether disease control with the fungicide propiconazole {1[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole} similarly affect agronomic and quality traits of hulled and hulless barley genotypes. Propiconazole reduced spot blotch severity. This resulted in increased yield and yield-related traits in hulled and hulless genotypes. Responses to propiconazole by the hulled and hulless genotypes were generally similar for spot blotch control, and similar for grain yield and 1000-kernel weight. The reduction in spot blotch severity did not result in brighter kernels or flour, nor did it affect mean total or soluble β-glucan content of hulled and hulless genotypes. Thus, hulless barley cultivars susceptible to spot blotch can be produced in the eastern area of the Upper Midwest barley growing region if they are protected with propiconazole. Research QuestionIn the Upper Midwest barley growing region of the USA, hulless waxy barley genotypes generally are grown only in western North Dakota, where environmental conditions often are not favorable for development of foliar and spike diseases. A concern with producing hulless waxy barley in the eastern area of the region is that the hulless character of the kernel may predispose it to more unsightly kernel diseases and discoloration than hulled barley. Also, hulless cultivars currently grown in the Upper Midwest are susceptible to a foliar disease, spot blotch, that can severely reduce yield. Cochliobolus sativus is the pathogen responsible for causing spot blotch and a major causal organism of kernel blight. Research on control of spot blotch and kernel blight with a foliar fungicide on hulless barley genotypes grown in the Upper Midwest has not been conducted. The objectives of this study were to determine whether natural field infections of the pathogen responsible for causing spot blotch and partly responsible for causing kernel blight similarly affect kernel and flour brightness of hulled and hulless barley genotypes, and to determine whether disease control with the fungicide propiconazole similarly affects agronomic and quality traits of hulled and hulless barley genotypes. Literature SummaryThe pathogen C. sativus can incite common root rot, spot blotch, and kernel blight in barley. In the Upper Midwest, spot blotch and kernel blight are the two most damaging diseases incited by C. sativus. The best control against C. sativus is sowing of resistant cultivars or use of fungicides. The fungicide propiconazole (Tilt®) has been labeled for use in barley for control of foliar and kernel diseases. Reports on use of propiconazole to control diseases incited by C. sativus are limited. Also, research comparing prevalence of spot blotch and kernel blight in hulled and hulless barley genotypes grown in the upper Midwest U.S. has not been conducted. Study DescriptionField experiments were conducted using a randomized complete block design with a split plot arrangement at Minot and Prosper, ND, in 1991 and 1992. Whole plots were propiconazole treatments (0 and 1.8 oz ai/acre) and subplots were genotypes. Ten hulled and eight hulless barley genotypes were evaluated. All but two of the genotypes were susceptible to spot blotch. Spot blotch severity was rated prior to maturity. Data collected on clean grain were yield, test weight, 1000-kernel weight, kernel plumpness, and kernel brightness. Flour brightness and total and soluble β-glucan content were determined on barley flour. Kernel and flour brightness were used to measure the level of kernel blight and discoloration. Applied QuestionsCan propiconazole be used to control spot blotch? Propiconazole reduced spot blotch severity in hulled and hulless genotypes. Mean reduction in spot blotch severity tended to be slightly better in the hulled genotypes than hulless genotypes. Did control of spot blotch by propiconazole result in increases in yield and yield-related traits? Control of spot blotch by propiconazole increased grain yield, 1000-kernel weight, and kernel plumpness in hulled and hulless genotypes. Improvements in grain yield and 1000-kernel weight were similar in hulled and hulless genotypes. Propiconazole significantly improved test weight in the hulled genotypes, but not the hulless genotypes. Improvements in kernel plumpness were generally greater in the hulless than the hulled genotypes. Did control of spot blotch by propiconazole result in improvements of quality related traits? Environmental conditions were not conducive for development of kernel blight. The reduction in foliar infection of spot blotch did not correspond to brighter kernels or flour. In fact, propiconazole slightly decreased kernel brightness. Spot blotch control by propiconazole had no affect on mean total or soluble β-glucan content of hulled and hulless genotypes.