Introduction. Fusarium head blight (FHB), incited primarily by Fusarium graminearum, severely affected the quality of barley (Hordeum vulgare L.) grown in North Dakota and northwestern Minnesota the past six years. Quality of harvested grain was reduced because of blighted kernels and the presence of deoxynivalenol (DON), a mycotoxin produced by the pathogen.

Nearly 40 barley genotypes have been identified with partial FHB resistance. Many of these genotypes are being used as sources of genes for FHB resistance and low DON accumulation; yet, little information is known about the genetic relationship between genotypes or their malt quality, agronomic performance, and reaction to other diseases. The objectives of this study are: 1) to determine the genetic relationship among barley genotypes with putative FHB resistance and genotypes susceptible to FHB using cluster analyses of genetic distance based on RAPD marker data, and taxonomic distance based on agronomic performance, morphological traits, and severity of FHB and other diseases; 2) to determine if the results from the cluster analysis of genetic distance are similar to the results from the cluster analyses of taxonomic distance; 3) to determine if genotypes within the same cluster based on genetic distance are identical; and 4) to compare the malt quality, agronomic performance, and reaction to other diseases of barley genotypes with partial resistance to FHB with barley cultivars currently grown in North Dakota.

Materials and Methods. Agronomic data were collected on genotypes grown in yield trial experiments in Fargo, ND in 1997 and 1998. Grain of each entry was malted and malt data were collected as described in Karababa et al. (1993). Data for FHB severity and DON content were obtained from genotypes grown in FHB epidemic nurseries at Fargo and Langdon, ND in 1997, and Fargo, Langdon, and Osnabrock, ND in 1998. Genotypes grown in epidemic nurseries were inoculated with F. graminearum and scored for FHB severity according to the methods of Prom et al. (1997). DON content was determined as described in Schwarz et al. (1995). Seedling responses to pathogens were tested in the greenhouse during fall 1997. Pathogens used for testing were Cochliobolus sativus, Pyrenophora teres (isolate NB89-19) , Puccinia hordei (race 8), Puccinia graminis f. sp. tritici (pathotypes Pgt-MCC and Pgt-QCC), and Blumeria graminis f. sp. hordei.

RAPD polymorphisms were identified using 50 10-decamer primers. Polymorphism data were used to calculate genetic distance. The taxonomic distance between genotypes was calculated separately using morphological, agronomic, FHB severity and DON content, and foliar disease data. Calculation of genetic and taxonomic distances and production of the corresponding dendograms was done using NTSYSpc (Rohlf, 1998) as described by Tatineni et al. (1996).

Results and Discussion. Twenty of the 50 primers tested identified polymorphisms among the 39 barley genotypes evaluated. These 20 primers produced 33 polymorphic RAPD fragments that were used to calculate genetic distance and to conduct the cluster analysis. Five clusters were identified at a genetic distance of 0.64 (Figure 1). Three genotypes did not fall into any cluster. Individual cluster analyses also were done for taxonomic distances based on morphological traits, agronomic traits, FHB severity and DON content, and resistance to foliar diseases. Based on the method of Mantel (1967), results indicate that the clusters for the taxonomic distance analyses are different than those obtained in the genetic distance analysis.

Most two-rowed Chinese genotypes are grouped in cluster 1 (Figure 1). However, Svanhals, developed in Sweden, and its derived genotypes also are included in this cluster. Genotypes in cluster 1, except Fuji Nijo, are the most resistant to FHB and have the lowest DON levels. It might be possible that genotypes in cluster 1 have similar alleles for FHB resistance and DON accumulation. Cluster 2 includes 11 genotypes (Figure 1). Genetic distances between genotypes in this cluster are greater than 0.25, except for Isaria and Balder. The genetic distance between these two genotypes is about 0.12, and the origin of both is northern and central Europe. There is a mixture of Asian, European, and US barley genotypes in cluster 3 (Figure 1), and this cluster includes all photoperiod sensitive genotypes except Misato Golden. FHB severity and DON levels were intermediate to high for cluster 3 genotypes. Cluster 4 contains four genotypes that were developed by Midwest US barley breeding programs. Chevron and the Chevron-derived genotype CIho16128 comprise cluster 5. These genotypes have the lowest FHB severity and DON levels of the six-rowed genotypes evaluated.

None of the resistant two- or six-rowed genotypes have acceptable malt quality for all traits. In general, excessive grain protein, and low kernel plumpness and malt extract are the traits most severely limiting. Most FHB resistant two- and six-rowed genotypes head significantly later and are taller than the genotypes currently grown. Most FHB resistant two-rowed genotypes are susceptible to leaf rust, wheat stem rust, net blotch, spot blotch, and powdery mildew, and all are susceptible to leaf rust. All FHB resistant six-rowed genotypes are susceptible to leaf rust, pathotype Pgt-QCC of wheat stem rust, and powdery mildew.

Improvements in malt quality, agronomic traits, and disease resistances of genotypes derived from crosses to FHB resistant accessions have been made. Yet, further improvements are needed before FHB resistant cultivars will be acceptable to producers and the malting and brewing industry. The genotypes that are progeny from crosses to FHB resistant genotypes have gone through one to two cycles of breeding. Our experience in working with unadapted germplasm tells us that at least four cycles of breeding are necessary to develop genotypes with acceptable agronomic performance and malt quality

References:

Karababa, E., P.B. Schwarz, and R.D. Horsley. 1993. Effect of kiln schedule on micro-malt quality parameters. Am. Soc. Brewing Chem.51(4):163-167.

Mantel, N.A. 1967. The detection of disease clustering and a generalized regression approach. Cancer Res. 27:209-220.

Prom, L.K., B.J. Steffenson, Salas, B., Fetch, T.G. Jr., and H.H Casper. 1997. Barley accessions resistant to Fusarium head blight and the accumulation of deoxynivalenol. p 807-808. In: Proc. 5^th European Fusarium Seminar. Á. Mesterházy (ed.) Cereal Research Institute, Szeged, Hungary.

Rohlf, F.J. 1998. NTSYSpc Numerical taxonomy and multivariate analysis system. Version 2.0. Applied Biostatistics, Inc., New York.

Schwarz, P.B., H.H. Casper, and S. Beattie. 1995. The fate and development of naturally occurring Fusarium mycotoxins during malting and brewing. J. Am. Soc. Brew. Chem. 53:121-127.

Sneath, P.H.A., and R.R. Sokal. 1973. Numerical taxonomy: The principles and practice of numerical classification. W.H. Freeman, and Company.

Tatineni, V., R.G. Cantrell, and D.D. Davis. 1996. Genetic diversity in elite cotton germplasm determined by morphological characteristics and RAPDs. Crop Sci. 186-192.