Scald and net blotch resistance in the Shyri x Galena population

 

Due to time, space, and resource constraints, scald and net blotch resistance QTL in the Shyri x Galena population were not reported by Toojidna et al. (2000).  Accordingly, we have made these phenotype data sets available at this site and used the same map and QTL analysis procedures employed by Toojinda et al. (2000) to map resistance QTL. The results are summarized below. 

Scald, incited by Rynchosporium secalis, and net blotch, incited by Pyrenophora teres f. teres, are two important foliar diseases in barley.  Sources of genetic resistance are known.  Scald resistance QTL were reported by Backes et al. (1995) on chromosomes 1 (7H), 3 (3H), 6 (6H) and 7 (5H), by Thomas et al. (1995) on chromosome 3 (3H), and by Spaner et al. (1998) on chromosomes 4 (4H) and 6 (6H).  Net blotch resistance QTL were reported by Steffenson et al. (1996) on all chromosomes except 5(1H) and by Spaner et al. (1998) on all chromosomes except 2(2H) and 5(1H).

The population and parents were assessed for adult plant resistance to scald at two planting dates at Toluca, Mexico in 1995 and 1996. These four environments were designated as:  Toluca 95-1; Toluca 95-2; Toluca 96; and Toluca 96-2. Scald severity was rated as percentage severity on a plot basis.  The DH population and parents were assessed for adult plant resistance to net blotch in field tests at Toluca, Mexico and Ciudad Obregon, Mexico in 1996. Two planting dates were used at each location, and the tests are designated as follows: Toluca 96-1; Toluca 96-2; CIANO 96-1; CIANO 96-2. Net blotch reaction type was scored using 0 - 9 scale (0 = immune, 9 = susceptible). These data are available at the disease phenotype page.

The frequency distributions for scald percentage of severity and net blotch reaction support quantitative inheritance (Fig. 1 and Fig 2). In the case of scald, there were no transgressive segregants more resistant than Shyri, but there were lines with higher disease severities than Galena, the susceptible parent.  In the case of net blotch, there were both positive and negative transgressive segregants. 

QTL results for scald and net blotch are summarized in Table 1.  One significant QTL was detected in the multi-environment analysis of the scald data.  This QTL is located on chromosome 1 (7H) and it is flanked by  ABG704 and MWG089. This QTL accounted for 9 % of the phenotypic variation in trait expression.  In the analysis of the individual environment data sets, significant QTL were detected in Toluca 95-1 and Toluca 95-2 .  In the Toluca 95-1 data, two QTL were detected, one in chromosome 3 (3H) and one in chromosome 6 (6H). BCD907 and HTPPB flank the QTL on chromosome 3 (3H), while RGA106 and MWG 620 flank the QTL on chromosome 6 (6H).  These QTL accounted for 27% of the variation in phenotypic trait expression.  In the Toluca 95-2 data, only one QTL was detected.  This QTL, on chromosome 1 (7H), coincides with the QTL detected in the multiple environment analysis. This QTL explained 14% of the phenotypic variation.

In the multiple environment analysis of the net blotch data, two QTL were detected on chromosome 3 (3H). The flanking markers are HTPPB-RGA52 and KsuAIH4 -T22M3li. These two QTL are 75 cM apart and jointly accounted for 22% of the variation in trait expression. In the analysis of the individual environment data, the QTL flanked by HTPPB and RGA52 was significant in all cases, whereas the QTL flanked by KsuAIH4 and T22M3li was significant only in the CIANO 96-1 data. A third QTL, which mapped between the previously described QTL on chromosome 3 (3H), was detected using the CIANO 96-2 data.

According the consensus map of Qi et al. (1996) and the Bin Map/QTL summary of Hayes et al (2000), none of the scald resistance QTL detected in the Shyri x Galena population coincide with QTL reported in other populations.  Of the net blotch QTL, the QTL flanked by KsuAIH4-T22M3Li coincides with a previous report (Steffenson et al., 1998), as does the QTL flanked by HVM15-HVM60 (Spaner et al., 1998).

 
References

1.      Backes G., A. Granner, B. Foroughi-Wehr, G. Fischbeck, G. Wenzel, and A. Jahoor. 1995. Localization of quantitative trait loci (QTL) for agronomic important characters by the use of a RFLP map in barley (Hordeum vulgare L.). Theor. Appl. Genet. 90: 294-302.

2.      Hayes P.M., A.Castro, L. Marquez-Cedillo, A. Corey, C. Henson, B. Jones, J. Kling, D. Mather, I. Matus, C. Rossi, K. Sato. 2000. A summary of published barley QTL reports. http://www.css.orst.edu/barley/nabgmp/qtlsum.htm   

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

  1. Spaner, D., L.P. Shugar, T. M. Choo, I. Falak, K. G. Briggs, W. G. Legge, D. E. Falk, S. E. Ullrich, N. A. Tinker, B. J. Steffenson, and D. E. Mather. 1998. Mapping of disease resistance loci in barley on the basis of visual assessment of naturally occurring symptoms. Crop Sci. 38:843-850.
  2. Steffenson, B. J., P. M. Hayes, and A. Kleinhofs. 1996. Genetics of seedling and adult plant resistance to net blotch (Pyrenophora teres f. teres) and spot blotch (Cochlibus sativus) in barley. Theor. Appl. Genet. 92: 552-558.

6.      Thomas, W.T.B., W. Powell, R. Waugh, K.J. Chalmers, U.M. Barua, P. Jack, V. Lea, B.P. Forster, J.S. Swanston, R.P. Ellis, P.R. Hanson, and R.C.M. Lance.  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.