SUMMARY OF BARLEY MALTING QUALITY QTLS

MAPPED IN VARIOUS POPULATIONS

J.M.Zale¹, J.A. Clancy¹, S.E. Ullrich¹, B.L. Jones², P.M. Hayes ³, and the North American Barley Genome Mapping Project. ¹ Department of Crop and Soil Sciences, Washington State University, Pullman WA 99164-6420, USA, ² Cereal Crops Research Unit, USDA-ARS, 501 Walnut St., Madison WI 53705, USA, ³ Department of Crop and Soil Science, Oregon State University, Corvallis, OR 97331, USA.

ABSTRACT Characters that affect malting quality (i.e. malt extract content, a- and b-amylase activity, diastatic power, malt b-glucan content, malt b-glucanase activity, grain protein content, kernel plumpness, and dormancy) are quantitatively inherited and variously influenced by the environment (E). Conventional genetic analyses have provided little useful information. Molecular technologies have opened the door for better understanding of these and other quantitatively inherited traits. Quantitative trait locus (QTL) analysis identifies chromosome regions, linked molecular markers, gene effects, QTL X E, and QTL X QTL interactions for a given trait. Considerable QTL analyses have been performed in recent years on a number of crosses. The objective of this study was to accumulate malting quality QTL mapping data published to date to update QTL designations in relation to consensus molecular markers. Additional molecular markers from an integrated map were used to anchor specific QTLs across mapping populations. Data has come from crosses of germplasm sources originating from North America, Europe, Australia and Asia. Based on our search, a minimum of 168 malting quality QTLs representing 19 malting quality traits have been mapped in nine mapping populations. QTL regions are spread across each of the seven barley chromosomes with concentrations especially within chromosomes 1, 2, 4, 5 and 7. Whereas, there is remarkable QTL conservation in some chromosome regions among crosses, some regions hold unique QTLs as well. It is also noteworthy that there are many overlapping QTLs, especially but not surprisingly, of related traits. Malt extract QTLs are almost always coincident with component traits such as carbohydrate hydrolytic enzyme activities. Diastatic power QTLs are often associated with a- and/or b-amylase activity QTLs. It is likely that pleiotropy is the cause, but gene clusters cannot be ruled out at this time. Given that malting quality determinants are widely distributed across the barley genome, care must be taken in choosing QTLs for selection in breeding programs. Magnitude of effect, of course, is one criterion that can be applied. In some cases widely conserved QTL chromosome regions may be targets for selection to maintain malting quality, but selection for unique regions may lead to new improvements. Whereas, understanding of the truly complex traits is far from complete, great advances in knowledge have been gained.

INTRODUCTION QTL analysis provides a better understanding of the genetic factors that influence complex traits such as malting quality. This analysis can identify chromosome regions, linked molecular markers, gene effects, QTL x E and QTL x QTL interactions that are important in plant improvement. The ability to detect chromosome regions that affect two or more traits also provides an understanding of the genetic basis for correlation between traits. A long-term goal of QTL analysis is to maintain or improve malting quality in barley cultivars through molecular marker assisted selection.

QTL mapping in barley has received worldwide attention. The North American Barley Genome Mapping Project has focussed on the Steptoe/Morex, Harrington/TR306,and Harrington/Morex populations, as well as several others. European researchers have studied the Blenheim/E224/3population and the Australian workers have concentrated on the Chebec/Harrington, Clipper/Sahara and Galleon/Haruna Nijo mapping populations.

OBJECTIVES

1) To review the literature on malting quality QTLs in barley and determine whether similar or unique QTLs have been identified among different mapping populations.

2) To create a composite map of each barley chromosome showing the relative locations of all malting quality QTLs from nine mapping populations.

MATERIALS AND METHODS Comprehensive updated maps showing malting quality QTLs were created by adding all reported malting quality QTLs to the skeleton maps of Hayes et al. (4). A total of nine mapping populations with 19 different malt quality QTLs have been published. New markers (in pink) necessary for locating reported QTLs were added to the Harrington/Morex skeleton map of Hayes et al. (4) based on the consensus markers of Qi et al. (11). Exact locations and even relative marker positions may vary across the maps of the nine mapping populations. Some QTLs were described by their peak position in Kosambi map units only and are shown by horizontal bars. Map distances shown are based on the Harrington/Morex population and may be considered as only approximate. Generally, QTLs are represented by vertical bars followed by malt quality trait abbreviation, mapping population (1-9), and reference (0-18). Smaller QTLs that fell within larger QTLs for the same trait were nested within the larger. The reader is urged to consult the original publications for more detailed information on allele phase, magnitude of effect, and the exact QTL position.

RESULTS AND DISCUSSION Among the most important parameters affecting malting are malt extract percentage, a-amylase activity, diastatic power, b-glucan content, grain protein percentage and dormancy. Generally, Harrington, Morex, Calicuchima-sib, Haruna Nijo, Blenheim, and Sahara 3371 contribute superior malting quality alleles. QTLs for many of the malt quality traits are concentrated in most of the mapping populations on chromosome 1 ABC158-Psr129; on chromosome 2 ABG008-ABG19; on chromosome 4 MWG634-BCD402B; on chromosome 5 Act8A-CDO99 and KgE33M59.222 –ABC159c; and on chromosome 7 MWG635d-ABC302a and ABG495a-MWG851b (see Maps). The North American Barley Genome Mapping Project has most thoroughly characterized the Harrington/TR306, Steptoe/Morex and Harrington/ Morex mapping populations and this is evident by the numerous malting quality QTLs for these mapping populations (see Maps and Table).

There is conservation in QTLs for grain protein on the short arm of chromosome 2 at ABG459 among five diverse mapping populations (see Map of Chromosome 2) and in several other traits throughout the genome. A minimum of 156 distinct malting quality QTLs were counted for the 19 traits in the nine mapping populations. Among all of the mapping populations, eighty-four percent of the malting quality QTLs are coincident.

The fact that many related malting quality traits occur together may indicate pleiotropic gene effects, or alternately, the presence of gene clusters. For example, the maps show that diastatic power is often associated with a-or b-amylase activity. However, there are cases of diastatic power not associated with its component enzymes. This may be due to the enzymes not being assayed independently or due to lack of polymorphism in the mapping populations. While many QTLs are similar among mapping populations, there are some apparently unique QTLs present.

Given that malting quality determinants are widely distributed across the barley genome, care must be taken in choosing QTLs for selection in breeding programs. Magnitude of effect is one criterion that can be applied. Widely conserved QTL chromosome regions may be targets for selection to maintain malting quality, but selection for unique regions may lead to new improvements.

REFERENCES

Han,F. and Ullrich, S.E. 1994. Mapping of QTLs associated with malting quality in barley. Barley Genet. Newslltr. 23:84-97.

Han, F., Ullrich, S.E., Chirat, S., Menteur, S., Jestin, L., Sarrafi, A., Hayes, P.M., Jones, B.L., Blake, T.K., Wesenberg, D.M., Kleinhofs, A., and Kilian, A. 1995. Mapping of b-glucan content and b-glucanase activity loci in barley grain and malt. Theor. Appl. Genet. 91:921-927.

Han, F., Ullrich, S.E., Kleinhofs, A., Jones, B.L., Hayes, P.M., and Wesenberg, D.M. 1997. Fine structure mapping of the barley chromosome-1 centromere region containing malting-quality QTLs. Theor. Appl. Genet. 95:903-910.

Hayes, P.M., Liu, B.H., Knapp, S.J., Chen, F., Jones, B., Blake, T., Franckowiak, J., Rasmusson, D., Sorrells, Ullrich, S.E., Wesenberg, D., and Kleinhofs, A. 1993. Quantitative trait locus effects and environmental interaction in a sample of North American barley germplasm. Theor. Appl. Genet. 87:392-401.

Hayes, P.M., Cerono, J., Witsenboer, H., Kuiper, M., Zabeau, M., Sato, K., Kleinhofs, A., Kudrna, D., Kilian, A., Saghai-Maroof, M., Hoffman, D., and the North American Barley Mapping Project. 1997. Characterizing and exploiting genetic diversity and quantitative traits in barley (Hordeum vulgare). J. Quant. Trait Loci 3(2) Avail. WWW: http://probe.nalusda.gov:8000/otherdocs/jqtl.

Karakousis, A., Kretschmer, J., Manning, S., Chalmers, K., and Langridge, P. 1996. The Australian barley genome mapping project. Available: WWW: http://greengenes.cit.cornell.edu/WaiteQTL

Larson, S.R., Habernicht, D.K., Blake, T. K., and Adamson, M. 1997. Backcross for six-rowed grain and malt qualities with introgression of a feed barley yield QTL.J. Am. Soc. Brew. Chem. 55:52-57.

Marquez-Cedillo, L.A., Hayes, P.M., Jones, B.L., Kleinhofs, A., Legge, W.G., Rossnagel, B.G., Sato, K., Ullrich, S.E., Wesenberg, D.M., and The North American Barley Genome Mapping Project. 2000. QTL analysis of malting quality in barley based on the doubled haploid progeny of two elite North American varieties representing different germplasm groups. Theor.Appl. Genet. (in press).

Mather, D.E., Tinker, N.A., LaBerge, D.E., Edney, M., Jones, B.L., Rossnagel, B.G., Legge, W.G., Briggs, K.G., Irvine, R.B., Falk, D.E., and Kasha, K.J. 1997. Regions of the genome that affect grain and malt quality in a North American two-row barley cross. Crop Sci. 37:544-554.

Oziel, A., Hayes, P.M., Chen, F.Q., and Jones, B. 1996. Application of quantitative trait locus mapping to the development of winter-habit malting barley. Plant Breeding 115:43-51.

Pan, A., Hayes, P.M., Chen, F., Chen, H.H., Blake, T., Wright, S., Karsai, I., and Bedo, Z. 1994. Genetic analysis of the components of winterhardiness in barley (Hordeum vulgare L.). Theor. Appl. Genet. 89:900-910.

Qi, X., Stam, P., and Lindout, P. 1996. Comparison and integration of four barley genetic maps. Genome 39:379-394.

Thomas, W.T.B., Powell, W., Swanston, J.S., Ellis, R.P., Chalmers, K.J., Barua, U.M., Jack, P., Lea, V., Forster, B.P., Waugh, R., and Smith, D.B. 1996. Quantitative trait loci for germination and malting quality characters in a spring barley cross. Crop Sci. 36:265-273.

Thomas, W.T.B., Powell, W., Waugh, R., Chalmers, K.J., Barua, U.M., Jack, P., Lea, V., Forster, B.P., Swanson, J.S., Ellis, R.P., Hanson, P.R., and Lance, R.C.M. 1995. Detection of quantitative trait loci for agronomic, yield, grain and disease characters in spring barley (Hordeum vulgare L.). Theor. Appl. Genet. 91:1037-1047.

Tinker, N.A., Mather, D.E., Blake, T.K., Briggs, K.G., Choo, T.M., Dahleen, L., Dofing, S.M., Falk, D.E., Ferguson, J.D., Frankowiak, J.D., Graf, R., Hayes, P.M., Hoffman, D., Irvine, R.B., Kleinhofs, A., Legge, W., Rossnagel, B.G., Saghai-Maroof, M.A., Scoles, G.J., Shugar, L.P., Steffenson, B., Ullrich, S.E., and Kasha, K.J. 1996. Loci that affect agronomic performance in two-row barley. Crop Sci. 36:1053-1062.

Tinker, N. The North American Barley Mapping Project (NABGMP) in Canada. 10 Jan. 1996. NABGMP, Canada, 12 Apr. 1999, Available: WWW: http://gnome.agrenv.msgill.ca/nabgmp/cnabgmp.htm.

Ullrich, S.E. and Han, F. 1997. Genetic complexity of the malt extract trait in barley suggested by QTL analysis. J. Am. Soc. Brew. Chem. 55:1-4.

Ullrich, S.E., Han, F., Blake, T.K., Oberthur, L.E., Dyer, W.E., and Clancy, J.A. 1995. Seed dormancy in barley: genetic resolution and relationship to other traits. p. 157-163. In K. Noda and D.J. Mares (ed.). Pre-harvest sprouting in cereals 1995. Center for Academic Societies, Osaka, Japan.

Ullrich, S.E., Han, F., and Clancy, J.A. 1998. Comparative mapping of beta-amylase activity loci among three barley crosses. Plant & Animal Genome VI International Conference (Jan. 18-22, San Diego). Final Program and Abstracts Guide, p 125.

Table 1. Incidence of malting quality QTLs: mapping population vs. chromosome number.

Mapping Population	1(7H)	2(2H)	3(3H)	4(4H)	5(1H)	6(6H)	7(5H)
Blenhem/ E224-3		GP	DP, GP KP		DP, GP, KP	KP	ME, DP
Calicuchima-sib/Bowman	AA, DP	AA, GP ME		DP, AA		ME	AA
Chebec/ Harrington		GP	Dor	DP, AA BA/F			Dor
Clipper/ Sahara		BA/F	FMB- Gase	BA/F	AA
Dicktoo/ Morex	AA, DP F/C, GP	ME		GP, AA, DP F/C	GP	GP	AA, DP F/C, GP ME
Galleon/ Haruna Nijo		DP, GP BA/F	BA/F	BA/F		DP AA	BA/F
Harrington/ TR306	GP	BA/P	BA/P BA/F F/C, EV MBG	Dor, KP,GP	DP, ME, GP BA/F, BA/P F/C	F/C, EV, AA, DP	ME, KP GP, AA DP, F/C SMP BBG, EV
Steptoe/ Morex	ME, MBG FMBGaseMBGase Dor, AA DP, BA/P	BBG ME, DP AA,GP KP	KP, GP MBG TMP AA, DP WC, SMP	MBG,BA/P BA/F, DP, AA ME, GP, Dor FM/GMBGase	DP, ME, AA KP, BA/F BA/P, BBG MBG FM/GMBGase	ME BA/P BA/F AA DP GP	AA, DP GP FM/ GMBGase Dor, KP
Harrington/ Morex	GP, DP, KP, BA/F BA/P	ME,GPBA/F BA/P DP, KP S/T		GP	KP	BA/P	GP, KP AA, S/T

Ledgend: AA- a amylase; BA/F- b amylase activity, U/g flour; BA/P- b amylase activity, U/mg protein; BBG- barley b-glucan; Dor- seed dormancy; DP- diastatic power; EV- extract viscosity; F/C- fine-coarse difference; FMBGase- finished malt b-glucanase; GMBGase- green malt b-glucanase; GP- grain protein; KP- kernel plumpness; MBG- malt b-glucan; MBGase- malt b-glucanase; ME- malt extract; SMP- soluble malt protein; S/T-soluble /total protein ratio; TMP- total malt protein; WC- wort clarity.