207In tetraploid and hexaploid wheat , the low molecular weight glutenin loci ( Mr )
were mapped at the X glu - 3 locus in the distal regions of chromosomes 1AS, 1BS,
and 1DS. A new Mr locus mapped to chromosome 7AL in T. monococcum
(Dubcovsky et al. 1997 ). Glaucousness inhibitor IW3 gene has been identifi ed in
Triticum dicoccoides (Wang et al. 2014 ). IW3 inhibits glaucousness formation by
altering wax composition. The gene has been mapped to chromosome 1BS.
8.2.3.4 Insect Resistance
Hessian Fly Resistance
Resistance to Hessian fl y was found in 65 of 147 accessions of T. araraticum screened
(Gill et al. 1983 ). No resistance to greenbug or WSMV was detected in this collec-
tion. A number of Hessian fl y resistance genes have been transferred to hexaploid
wheat from T. tauschii. One such resistance gene was transferred from T. turgidum
ssp. dicoccum and mapped to the short arm of chromosome 1A (Liu et al. 2005 ). This
is the fi rst emmer-derived insect resistance gene to be mapped and characterized. To
date, a total of 14 Hf resistance genes have been transferred from T. turgidum
ssp. durum to hexaploid wheat. More recently the gene Hdic has been identifi ed in
T. dicoccum and transferred to hexaploid wheat (Liu et al. 2005 ). This introgressed
gene mapped to wheat chromosome 1A in the same region as H9 , H10 , and H11.
8.3 Triticum timopheevii
The wild hulled form of T. timopheevii is designated as Triticum timopheevii (Zhuk.)
Zhuk subsp. armeniacum (Jakubz) Slageren (Traditionally known as Triticum ara-
raticum Jakubz). The domesticated hulled form is classifi ed as Triticum timopheevi i
(Zhuk.) Zhuk subsp. timopheevii. The cultivated free threshing form is designated
as T. militinae Zhuk & Migush. In the wild the species is found, according to some
accounts, in southern zones of T. dicoccoides (AABB), distribution which occurs in
the Fertile Crescent. The genome of T. timopheevi is designated as AAGG. Its origin
is not entirely clear, but appears to be a double mutation from an AABB genotype
that controls chromosome asynapsis that lead to reproductive isolation, T. timophee-
vii has a diploidizing mechanism similar to the Ph1b system in hexaploid wheat
(Martinez et al. 1996 ). There are not many reports of gene transfer from T. timophee-
vii to wheat. It is initiated by normal crossing and embryo rescue followed by up to
three backcrosses to restore fertility. Interest in T. timopheevii as a source of disease
resistance for bread wheat goes back about 70 years. Wheat-like progeny with resis-
tance to stem rust, leaf rust and mildew were reported by Pridham ( 1939 ) and
Shands ( 1941 ). Semeniuk ( 1947 ) reported detailed cytogenetic studies of advanced
generations of stem and leaf rust resistant progeny obtained from the hybrid of
8 Alien Introgressions from wild Tr it icu m species, T. monococcum...