Coordinator’s report: Chromosome 7H

 

Coordinator’s report: Chromosome 7H

 

Lynn S. Dahleen

 

USDA-Agricultural Research Service

Fargo, ND 58105, USA

 

Hard-copy edition pages 149 - 151.

Mapping and marker development progressed in the last year, both for barley and for two related Hordeum species. Researchers looked at single genes and QTLs for disease resistance, morphological markers, and many agronomic traits.

 

Macaulay and colleagues at SCRI, 2001 selected a ‘genotyping set’ of 48 well characterized SSR markers for genetic studies in barley. Seven of these markers are located on chromosome 7H. When tested against a reference set of 24 barley genotypes, these SSRs on chromosome 7H had polymorphism information content values ranging from 0.41 to 0.87, indicating they should be useful in a large number of crosses. Research has continued on combining the physical and molecular maps of barley. Serizawa et al., 2001 examined a series of 22 deletion and translocation stocks in the wheat-barley addition lines for chromosome 7H. The stocks were used for deletion mapping of 17 AFLP and 28 STS markers. The deletion stocks provided additional breakpoints that were not recovered in the previous studies using translocation stocks. Marker orders matched previous maps.

 

Agronomic trait QTLs were located in three reports. Marquez-Cedillo et al., 2001 analyzed QTL for agronomic traits in a doubled haploid population derived from Harrington x Morex. They found QTLs on chromosome 7H for heading date and height using the full population, and a QTL for kernel plumpness using a 2-rowed sub-population. QTLs in a Mediterranean population derived from Tadmor x Er/Apm were located by Teulat et al., 2001. Significant regions on chromosome 7H were identified for height and heading date, both in single locations and in the overall analysis. QTLs for yield and harvest index were identified that were important only in certain environments. Choo et al., 2001 examined associations between the nud hulless gene and agronomic traits in a population of doubled haploid lines from Kunlun no.1 x CIMMYT no.6. Hulless lines generally had lower yield, seed weight, plant density and emergence rate, were shorter and had higher test weights.

 

Disease resistance-related loci were mapped to chromosome 7H in two studies. Scheurer et al., 2001 analyzed QTLs for tolerance to BYDV-PAV in two populations derived from the resistant cultivar Post. After inoculating the lines with the virus, they found that one region on chromosome 7H was associated with an increase in kernel yield and another was associated with earlier heading. A new leaf stripe resistance gene was mapped by Tacconi et al., 2001. They mapped the Rgd2a gene from the cultivar Thibaut to the telomeric region of 7HS and developed STS primers for linked RAPD and RFLP markers. The resistance gene is located in the same region as genes for resistance to stem rust, powdery mildew and scald.

 

Other QTL mapping projects looked at additional traits. Takahashi et al., 2001 mapped QTLs for deep-seeding tolerance in the Steptoe x Morex and Harrington x TR306 populations. One significant QTL was located on the short arm of chromosome 7H in the Steptoe x Morex population. They also located QTLs for kernel weight and first internode length on 7H in both populations. Bregitzer and Campbell, 2001 also used the Steptoe x Morex mapping population to locate QTLs for green and albino plant regeneration from barley callus cultures. They identified eight regions associated with green plant regeneration, one from Steptoe which was located on 7H. They then used their mapping data to develop a model to predict regeneration response, which explained approximately 62% of the variability for this trait.

 

An additional map was developed for the Oregon Wolfe Barleys (Costa et al., 2001). This involved a cross between the recessive and dominant morphological marker stocks, which segregated for twelve morphological traits. The map they developed for chromosome 7H includes four SSR, 13 RFLP, 1 RAPD and 143 AFLP markers, and covers 191 cM. Two morphological traits, for naked caryopsis (nud) and for short awn (lks2), were included in this chromosome.

 

Two studies report the creation of linkage maps in related Hordeum species and their comparison to maps in barley and wheat. A map of  H. chilense was developed by Hernandez et al., 2001. The map of 123 markers contained 26 RAPD and 1 RFLP marker on the chromosome homoeologous to barley 7H. In general, marker order was consistent with that found in barley and wheat. Salvo-Garrido et al., (2001) developed an RFLP map of diploid H. bulbosum. Recombination in this species was lower than barley in centromeric regions but similar or greater in more distal regions. The chromosome 7H map contained 22 loci that showed good collinearity with the barley and Triticeae consensus map order.

 

References:

 

Bregitzer, P. and R.D. Campbell. 2001. Genetic markers associated with green and albino plant regeneration from embryogenic barley callus. Crop Sci. 41:173-179.

 

Choo, T.-M., K.M. Ho, and R.A. Martin. 2001. Genetic analysis of a hulless x covered cross of barley using doubled-haploid lines. Crop Sci. 41:1021-1026.

 

Costa, J.M., A. Corey, P.M. Hayes, C. Jobet, A. Kleinhofs, A. Kopisch-Obusch, S.F. Kramer, D. Kudrna, M. Li, O. Riera-Lizarazu, K. Sato, P. Szucs, T. Toojinda, M.I. Vales, and R.I. Wolfe. 2001. Molecular mapping of the Oregon Wolfe Barleys: a phenotypically polymorphic doubled-haploid population. Theor. Appl. Genet. 103:415-424.

 

Hernández, P., G. Dorado, P. Prieto, M.J. Giménez, M.C. Ramírez, D.A. Laurie, J.W. Snape, and A. Martin. 2001. A core genetic map of Hordeum chilense and comparisons with maps of barley (Hordeum vulgare) and wheat (Triticum aestivum). Theor. Appl. Genet.102:1259-1264.

 

Macaulay, M., L. Ramsay, W. Powell, and R. Waugh. 2001. A representative, highly informative ‘genotyping set’ of barley SSRs. Theor. Appl. Genet. 102:801-809.

 

Marquez-Cedillo, L.A., P.M. Hayes, A. Kleinhofs, W.G. Legge, B.G. Rossnagel, K. Sato, S.E. Ullrich, D.M. Wesenberg, and the North American Barley Genome Mapping Project. 2001. QTL analysis of agronomic traits in barley based on the doubled haploid progeny of

two elite North American varieties representing different germplasm groups. Theor. Appl. Genet. 103:625-637.

 

Salvo-Garrido, H., D.A. Laurie, B. Jaffé, and J.W. Snape. 2001. An RFLP map of diploid Hordeum bulbosum L. and comparison with maps of barley (H. vulgare L.) and wheat (Triticum aestivum L.). Theor. Appl. Genet. 103:869-880.

 

Scheurer, K.S., W. Friedt, W. Huth, R. Waugh, and F. Ordon. 2001. QTL analysis of tolerance to a German strain of BYDV-PAV in barley (Hordeum vulgare L.). Theor. Appl. Genet. 103:1074-1083.

 

Serizawa, N., S. Nasuda, F. Shi, T.R. Endo, S. Prodanovic, I. Schubert, and G. Künzel. 2001. Deletion-based physical mapping of barley chromosome 7H. Theor. Appl. Genet. 103:827-834.

 

Tacconi, G., L. Cattivelli, N. Faccini, N. Pecchioni, A.M. Stanca, and G. Valé. 2001. Identification and mapping of a new leaf stripe resistance gene in barley (Hordeum vulgare L.). Theor. Appl. Genet. 102:1286-1291.

 

Takahashi, H., K. Sato, and K. Takeda. 2001. Mapping genes for deep-seeding tolerance in barley. Euphytica 122:37-43.

 

Teulat, B., O. Merah, I. Souyris, and D. This. 2001. QTLs for agronomic traits from a Mediterranean barley progeny grown in several environments. Theor. Appl. Genet. 103:774-787.

 

 

 

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