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Browsing by Author "Muehlbauer, G.J."

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    Genetic architecture of quantitative trait loci associated with morphological and agronomic trait differences in a wild by cultivated barley cross
    (Genome, 2007) Steffenson, Brian; Gyenis, L.; Yun, S.J.; Smith, K.P.; Bossolini, E.; Sanguineti, M.C.; Muehlbauer, G.J.
    Hordeum vulgare subsp. spontaneum is the progenitor of cultivated barley (Hordeum vulgare L.). Domestication combined with plant breeding has led to the morphological and agronomic characteristics of modern barley cultivars. The objective of this study was to map the genetic factors that morphologically and agronomically differentiate wild barley from modern barley cultivars. To address this objective, we identified quantitative trait loci (QTLs) associated with plant height, flag leaf width, spike length, spike width, glume length in relation to seed length, awn length, fragility of ear rachis, endosperm width and groove depth, heading date, flag leaf length, number of tillers per plant, and kernel color in a Harrington/OUH602 advanced backcross (BC2F8) population. This population was genotyped with 113 simple sequence repeat markers. Thirty QTLs were identified, of which 16 were newly identified in this study. One to 4 QTLs were identified for each of the traits except glume length, for which no QTL was detected. The portion of phenotypic variation accounted for by individual QTLs ranged from about 9% to 54%. For traits with more than one QTL, the phenotypic variation explained ranged from 25% to 71%. Taken together, our results reveal the genetic architecture of morphological and agronomic traits that differentiate wild from cultivated barley.
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    Quantitative trait loci for multiple disease resistance in wild barley
    (Crop Science, 2005) Steffenson, Brian; Yun, S.J.; Gyenis, L.; Hayes, P.M.; Matus, I.; Smith, K.P.; Muehlbauer, G.J.
    Foliar diseases of barley (Hordeum vulgare L.) such as spot blotch [caused by Cochliobolus sativus (Ito & Kuribayashi) Drechs. ex Dastur], net type net blotch (NTNB; caused by Pyrenophora teres f. teres Drechs), Septoria speckled leaf blotch (SSLB; caused by Septoria passerinii Sacc.), leaf scald [caused by Rhynchosporium secalis (Oudem.) J. J. Davis], and powdery mildew (caused by Blumeria graminis f. sp. hordei Em. Marchal) can result in significant yield reductions in many production areas. The wild progenitor of cultivated barley, Hordeum vulgare subsp. spontaneum is well known as a rich source of disease resistance. To determine the location of H. vulgare subsp, spontaneum-derived alleles for disease resistance, we conducted quantitative trait locus (QTL) analysis of a recombinant inbred line (RIL) population derived from a cross between the resistant H. vulgare subsp, spontaneum accession OUH602 and the two-rowed malting cultivar Harrington. A total of 151 simple sequence repeats (SSR) markers were mapped into 11 linkage groups, covering 948 cM. Major QTLs for resistance to each disease were identified: one for spot blotch resistance on chromosome 1(7H); three for NTNB resistance on chromosomes 3(3H), 4(4H), and 5(1H); two for SSLB resistance on chromosomes 2(2H) and 6(6H); one for leaf scald resistance on chromosome 5(1H); and two for powdery mildew resistance on chromosomes 4(4H) and 5(1H). Resistance alleles for each QTL were contributed by OUH602, except those for NTNB and powdery mildew resistance on chromosome 5(1H) and chromosome 4(4H), respectively. The two QTLs identified for SSLB resistance are novel. All other QTLs mapped to regions where known resistance QTLs or major resistance genes have been reported. Our results indicate that most of the OUH602-derived loci are clustered in regions coincident with those described in cultivated barley. These resistance QTLs and their associated markers should be valuable for further exploitation of disease resistance variation in barley improvement.