Recent years have been disappointing for barley growers in the Midwestern U.S.A. with major losses caused by Fusarium head blight (scab) and excessively wet growing conditions. The disease epidemic, coupled with unfavorable growing conditions, has resulted in low grain yield and poor quality barley, frequently with high vomitoxin levels. Kernel diseases other than scab have caused diseased and discolored grain.

Scab Breeding Program

Following the outbreak of the scab epidemic in 1993, our research priorities have changed and scab resistance breeding is occupying most of our attention. While scab attacked barley in Minnesota a few decades ago, it is essentially a new disease for us.

Some data obtained in cooperation with John Wiersma indicate that Stander and Robust, the two large acreage varieties, are susceptible to scab. When vomitoxin levels were 5.2 and 5.9 ppm for Robust and Stander, respectively, grain yields were near normal. On the other hand, in an artificially inoculated trial with unusually high levels of the disease, yield was reduced in both varieties by about 30%. The vomitoxin levels in this trial were 19 and 20 ppm for Robust and Stander, respectively.

The difficulty in finding varieties that differ in vomitoxin level in the grain was emphasized in a 1995 trial. In a trial with four replications, Morex vomitoxin levels ranged from 3.2 to 14.2 ppm and Stander from 6.6 to 13.0 ppm. Based on other data, it appears that Robust and Stander have similar levels of vomitoxin under typical field conditions, whereas at high levels of scab infection Robust fairs somewhat better.

More than 2,000 barley lines were evaluated in 1995 for scab reaction at three locations. In one Crookston nursery, 51 entries were evaluated for scab severity (% infected kernels) and kernel discoloration. A sample of the data is shown in Table 1. A few resistant lines had less than 10% infected kernels and bright disease-free grain. Robust and Stander had 52 and 54% infected kernels and diseased and discolored grain. Some lines, e.g., Steptoe, approached 100% of scab infected kernels.

One aspect of the scab breeding effort entails utilizing lines from a long-term breeding program for resistance to kernel infecting diseases. Chevron, a six-row introduction from Switzerland in 1914, was the source of resistance. Some of these lines exhibited tolerance to scab, lower vomitoxin levels and reduced kernel discoloration compared to Stander.

Table 1. Scab-Kernel discoloration data.

	Scab rating	Kernel discoloration
	(% infected kernels)	(1-5; 1 best)
Resistant
M92-299 (Chevron/M69)	3	1.4
Gobernadora	4	2.0
Chevron	9	1.2
Modertely resistant
GD-27 (Harrington/Excel)	23	2.0
M90-89 (Chevron progeny)	25	3.2
Zedhar #1	31	1.9
Moderately susceptible
Robust	52	4.7
Stander	54	4.3
Susceptible
Karl	77	4.1
Steptoe	97	5.0

 
 
 

Introgression of Agronomic and Quality Genes

A project was initiated in 1991 to broaden genetic diversity in the Minnesota (MN) six-row malting barley gene pool. Based on pedigree analysis and phenotypic uniformity, diversity is limited. In this effort, two cycles of breeding have been done to introgress genes for malting quality and agronomic merit from European two-row barley. In cycle 1, five populations were evaluated: two single crosses, one 3-way cross, and two backcrosses. The 3-way and backcross crosses were made to elite MN lines to increase the proportion of MN germplasm. In cycle 2, eight populations were evaluated. These were single cross populations involving eight parents from cycle 1. The aspiration was to recover, in cycle 1 and/or cycle 2, lines with sufficient MN germplasm to perform well for all agronomic, quality and disease traits while having sufficient introgressed germplasm (two-row) to surpass the local gene pool for a few target traits.

The findings were moderately encouraging. In cycle 1, some six-row lines had useful diversity for several traits including head number, kernel number, malt extract, and low soluble and low total protein. The better lines were similar to local checks in grain yield. However, none of the recovered lines were good enough to warrant variety consideration. Major weaknesses were thin kernels, lodging susceptibility, and low alpha and beta amylase.

The best of the cycle 2 lines were much improved compared to cycle 1. After rigorous selection for agronomic, quality and disease traits, 13 lines were identified with variety potential. They appear to have a desirable agronomic and quality profile, similar to local checks. On a theoretical basis, the most promising lines (assuming no selection) have 12.5% of two-row germplasm.

Kernel Discolouration in Western Australia and the Performance of North American Lines. Kevin J Young (current address, University of Minnesota)

The southern cereal growing region of Western Australia produces about 0.5m tonnes of barley annually. On average only 65% of the production of the malting barley varieties is accepted into the malting grade. The major reason for rejection is kernel discolouration (KD) due to weather staining. A project commenced in 1995 which aims to determine the effects of genotype, development stage and environment on KD in Western Australia. Four hundred and fifty barley lines consisting of Australian and overseas cultivars and elite crossbreds were sown at Esperance on the south coast of Western Australia in 1995. Heads were scored visually for discolouration. Only a very small number of the 450 lines tested showed any significant improvement over the popular local variety Stirling. The most promising lines originated from Canada and Japan with the some of them maintaining a bright colour after a month's delay in harvest. Lines from Australia, Europe, ICARDA and the USA were generally similar to Stirling with only minor improvements in a few lines. The KD resistant lines from the University of Minnesota were not available for testing in the first year of the project. The standard Midwestern six row barleys were heavily discoloured. The best lines from Canada are two row lines, TR118 (a malting line) and SB85738 (a naked type, although the scores relate to its hull colour).

In the ensuing four years of the project additional lines, local and imported, will be screened in field trials. This will include progeny of crosses between local varieties and the most promising lines showing resistance to kernel discolouration including lines from the University of Minnesota. Nursery tunnels will be erected and the most promising lines irrigated using overhead sprinklers to ensure conditions that predispose the grain to kernel discolouration. Work will commence to identify the major pathogens involved and quantify grain colour using digital image analysis. Studies on the relative susceptibility of stages of grain development to rain and high relative humidity will be conducted in nursery tunnels.

Improving Grain Yield of Semidwarf Barley

Grain yield of barley genotypes possessing the sdw semidwarf gene has been disappointing. It is our experience, semidwarf progeny are lower yielding than normal height progeny. Accordingly, a project was initiated in 1992 to evaluate four parental strategies to enhance grain yield of semidwarf barley. These strategies were using parents with a) high grain yield, b) high head number, c) high kernel number, and d) high kernel weight. Eight populations were created by crossing two lines for each strategy with Royal, a recently released sdw semidwarf variety. Sixteen semidwarf lines in each of the eight populations were evaluated in three environments.

Substantial variation was obtained for head number, kernel number and kernel weight in the several populations. So the goal of creating distinctive semidwarf populations for the three yield components was achieved.

The research findings were consistent with our long-term experience with the sdw semidwarf. Relatively few lines were equal in grain yield to the checks, Royal and Robust. The head number and kernel weight populations were most promising with a few lines equal to or modestly exceeding Royal and Robust. Using high grain yield parents, Excel and M66, failed to produce high yielding progeny. Our results again indicate the difficulty in achieving high yield in sdw semidwarfs. Based on these findings, parents high in head number and kernel weight offer more promise for improving grain yield of sdw semidwarf barley than high yield and high kernel number parents.

Enhancing Barley Malting Quality Using Morex QTLs

Molecular marker assisted selection of barley malting quality traits is an attractive alternative to conventional selection procedures. A study was initiated in 1994 to determine whether malting quality quantitative trait loci (QTL) identified in the cultivar Morex can be utilized in improvement of Midwestern USA malting barley. The quality QTL were identified in the Steptoe/Morex population. Five populations derived from crosses of Morex to regional malting cultivars Kindred, Traill, Robust, Excel and Stander were developed to investigate restriction fragment length polymorphism (RFLP) markers and 16 associated malting quality QTL.

Polymorphism for the RFLP markers was low within the regional malting barley germplasm compared to that in a diverse set of barley genotypes. The absence of polymorphism between Minnesota cultivars Morex, Robust, Excel, and Stander precluded study of the crosses involving Robust, Excel and Stander and appears to limit use of Morex QTL in improving malting quality in elite Midwestern USA germplasm. In crosses with older North Dakota cultivars Kindred and Traill, polymorphism was found for 11 RFLP markers. Analyses will be conducted to determine the expression of these Morex QTL in Kindred and Traill backgrounds.