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promote transfer of BYDV resistance and, respectively, salt tolerance from addition
lines for a group 7 Th. intermedium chromosome (7Ai-1) and for a group 5 Th.
junceum chromosome (AJDAj5). On the other hand, in a number of cases (see
ahead) exchange products of potential breeding value have spontaneously occurred,
probably as a result of the action of pairing promoting genes present in perennial
Triticeae genomes , which, to various extent, appear to counteract the suppressing
effect of wheat Ph genes (Dvorak 1987 ; Zhang and Dong 1995 ; Jauhar and
Almouslem 1998 ; Jauhar and Peterson 2000 ; Kang et al. 2008 ; Mullan et al. 2009 ).
Whatever the method adopted for promoting exchanges, segmental introductions
that involved homoeologous chromosomes and were of relatively more limited
length gave rise to the best compensating and hence useful products for breeding
exploitation.
11.3.3.1 Transfers Involving Th. intermedium and Th. ponticum
Favoured by the close relationships of their E/J and St basic genomes (Table 11.1 )
with those of wheat, particularly D and A, Th. intermedium and Th. ponticum , and
so diploid species of the same genus, result the most valuable species contributing
to wheat cultivar development among perennial Triticeae , and probably among wild
relatives altogether (e.g., Li and Wang 2009 ; Wang 2011 ; Mujeeb-Kazi et al. 2013 ).
As for other alien donors, among the many useful genes that have been stably trans-
ferred from Thinopyrum species into compensating wheat translocation/recombi-
nant lines, the more easily manageable genes conferring disease resistance prevail.
Many of these were described in previous extensive reviews (e.g., Mclntosh et al.
1995 ; Friebe et al. 1996 ; Li and Wang 2009 ). In recent years, the list of exploitable
resistance sources has widened, with addition of several new genes, and of genes
previously included in transfer types unsuitable for breeding use (e.g., associated
with excessive alien chromatin amount).
Introgression s from Th. intermedium
As to Th. intermedium , transfers into wheat include Pm40 (Luo et al. 2009 ) and
Pm43 (He et al. 2009 ) for resistance to wheat powdery mildew, a disease toward
which the donor species shows complete immunity (Wang et al. 2000 ). Both trans-
fers appeared to consist of a spontaneously occurred cryptic translocation (the for-
mer on wheat 7BS, the latter on 2DL), giving rise to cytologically and phenotypically
suitable bread wheat lines for use in breeding, especially in humid Chinese environ-
ments, where the disease is constantly epidemic. From the same wheat- Th. interme-
dium partial amphiploid used as donor material of the Pm43 gene, an additional,
spontaneous translocation product was recently obtained, consisting of a bread
wheat line with a pair of chromosomes 6A carrying a Th. intermedium segment
which occupies most of the short arm, and contains a gene with dominant inheri-
tance, determining an immune reaction to powdery mildew races collected from
C. Ceoloni et al.