The hard red spring wheat line ND643 was used in crosses with CIMMYT germplasm to introgress the high protein content gene gpc-B1. Several lines derived from these crosses showed moderate seedling and adult plant resistance to race TTKSK (Ug99) of Puccinia graminis f. sp. tritici. The gene responsible for this resistance was designated SrND643 (1).
Basnet et al. (2) determined that the chromosomal location of SrND643 is on the distal end of chromosome arm 4AL. These authors developed a mapping population of 123 F4:5 RILs by crossing ND643/2*Weebill with the susceptible line Cacuke and tested it in the KARI´s field facilities in Njoro, Kenya for two seasons. Based on the shape and size of uredinia on the stems, Cacuke showed infection responses between susceptible and moderately susceptible, and ND643/2*Weebill between moderately resistant, and moderately resistant to moderately susceptible. Regarding disease severity, the susceptible parent scored a disease severity of at least 80% and for the resistant parent ranged between 5 to 15%.
SrND643 is moderately effective against the races of the Ug99 group, including the newer TKTTF race. It is already present in several lines developed at CIMMYT (see Ref.2 for more information on available germplasm) and it must be combined with other resistance for effective deployment in the field.
Markers for SrND643
SrND463 is located on the distal end of long arm of chromosome 4A, flanked by SSR markers gwm350 (proximal) at 0.5 cM and wmc219 (distal) at 4.1 cM.
Primer sequences:
gwm350
WMS350-F 5´- ACC TCA TCC ACA TGT TCT ACG -3´
WMS350-R 5´- GCA TGG ATA GGA CGC CC -3´ Annealing temperature: 55°
wmc219
WMC219-F 5´- TGC TAG TTT GTC ATC CGG GCG A -3´
WMC219-R 5´- CAA TCC CGT TCT ACA AGT TCC A -3´ Annealing temperature: 61°C
Expected products:
The wmc219 and gwm350 alleles linked to SrND643 amplify bands of 136 and 148 bp respectively. All CIMMYT lines postulated to contain SrND643. Other lines not carrying this gene amplify bands of other sizes or fail to amplify.
References
1.The emergence of Ug99 races of the stem rust fungus is a threat to world wheat production. Singh RP, Hodson DP, Huerta-Espino J, Jin Y, Bhavani S, Njau P, Herrera-Foessel S, Singh PK, Singh S, Govindan V In: Annual Review of Phytopathology, 2011, 49:465-481. DOI:10.1146/annurev-phyto-072910-095423
2. Molecular Mapping and Validation of SrND643: A New Wheat Gene for Resistance to the Stem Rust Pathogen Ug99 Race Group. Basnet BR, Singh S, Lopez-Vera EE, Huerta-Espino J, Bhavani S, Jin Y, Rouse MN, Singh RP. In: Phytopathology, 2015, 105:470-476]. DOI:10.1094/PHYTO-01-14-0016-R.