202
The high temperature adult plant stripe rust resistance gene Yr36 was mapped to
chromosome 6B and found to be very tightly linked to the grain protein content
locus (Uauy et al. 2005 ). This study was made possible by the use of recombinant
substitution lines of chromosome 6B of T. dicoccoides in a Langdon background.
Thus far, 140 QTL for stripe rust resistance in wheat have been identifi ed, spread
over 49 chromosome regions on wheat maps (Rosewarne et al. 2013 ). Many of these
QTL are likely identifi ed genes. Many of these genes have already been defeated by
alterations in the organism. It is therefore necessary to search for additional resis-
tance genes. The wild emmer wheat Triticum turgidum spp. dicoccoides is proving
to be one of these sources of new resistance genes.
8.2.2.4 Powdery Mildew Resistance
All of the resistant reactions shown in Table 8.5 are controlled by single genes.
Some genes such as Pm4 are effective at the seedling and adult plant stages. Some
loci have numerous alleles such as Pm4 with 4 and Pm5 with 5. According to
Dhaliwal et al. ( 1993 ), the T. dicoccoides -derived genes Pm4a , Pm5 , Pm16 were
all integrated into cultivated wheat. Molecular markers have now been assigned to
four of the emmer-derived Pm genes shown in Table 8.5. A dominant powdery
mildew resistance gene PmAS846 was transferred from T. dicoccoides to hexaploid
Table 8.5 Powdery mildew resistance genes introgressed from wild emmer or durum
Gene/alleleChromosome
location Cultivar/Line Source Reference
Pm3h 1AS Abessi T. durum Zeller and Hsam
( 1998 )
Pm4a a 2AL Khapli T. dicoccum The et al. ( 1979 )
Pm5a 7 BL Hope T. dicoccum Law and Wolfe
( 1973 )
Pm16 4A Noman rec. line T. dicoccoides Reader and
Miller ( 1991 )
Pm26 2BS TTD140 T. dicoccoides Rong et al.
( 2000 )
Pm30 a 5BS C20 T. dicoccoides Liu et al. ( 2002 )
Pm31 a 6AL G-305-M/781//Jin411 a 3 T. dicoccoides Xie et al. ( 2003 )
MIZeo l 2BL Zecoi-1 T. dicoccoides Mohler et al.
( 2005 )
Hua et al. ( 2009 )
Pm42 2BS P63 T. dicoccoides Piarulli et al.
( 2012 )
Pm50 2AL K2 T. dicoccum Mohler et al.
( 2013 )
MeIW72 a 7A IW72 T. dicoccoides Ji et al. ( 2008 )
a Indicates that genes have been mapped
G. Fedak