297central Italy environment where durum wheat is typically grown. Signifi cant and
differential impacts on relevant yield traits could be detected in homozygous carri-
ers (HOM+) vs. non-carriers (HOM−) of the different 7el 1 L segments (Ceoloni
et al. 2014b ; Kuzmanovic et al. 2014 ). 7el 1 L genes/QTL determining positive
effects on grain and tiller number, grain and biomass yield, fl ag leaf dimensions and
chlorophyll content, were found to be all located within the distal 40 % of the alien
arm. Most of them turned out to reside within the 28 %-long 7el 1 L segment of line
R112- 4, except for the locus/i controlling grain number per spike and per spikelet,
present in the most proximal 7el 1 L portion of the total 40 % assayed, specifi c to
R23-1 (Fig. 11.3 ).
Many of the valuable loci detected and confi rmed across years appear to be read-
ily exploitable in durum wheat breeding , as they are included in the R112-4 7el 1 L
segment that has no undesirable linkage drag for the recipient species. Less straight-
forward may turn out to be the harnessing of the grain number per spike/spikelet
locus, in most instances found to be associated with considerably decreased kernel
weight and, at times, also depending on the wheat genotype, with other abnormal
plant phenotypes. These have been tentatively attributed to the presence, in the same
R23-1-specifi c 7el 1 L segment, of a Sd gene (probably Sd1 , see also above), deter-
mining in durum wheat backgrounds a more or less severe segregation distortion of
such a recombinant chromosome, always in the direction of self-elimination through
the male germline (Ceoloni et al. 2014a ).
Taking advantage of the 7el 1 -7el 2 homologous relationships, via homologous
recombination in hybrids between translocation/recombinant lines carrying the two
long arms or portions of them, useful genes originally present in either one have
Fig. 11.3 Structural–functional dissection of 7A-7Ag chromosomes representing three durum
wheat- Th. ponticum recombinant lines. Within the 7AgL regions defi ned by the different
7AL-7AgL breakpoints in the three chromosome types, known genes ( Lr19 , Sr25 , Yp , Sd ), and
putative genes/QTL for yield-contributing traits could be assigned (adapted from Kuzmanovic
et al. 2014 and unpublished). White background = 7A, red background = 7AgL. FL fractional arm
length of the breakpoint to centromere distance, from 0 = centromere to 1 = telomere
11 Wheat-Perennial Triticeae Introgressions: Major Achievements and Prospects