Characterization of wheat-alien translocations conferring resistance to diseases and pests: current status

Abstract

Wild relatives of common wheat, Triticum aestivum, and related species are an important source of disease and pest resistance and several useful traits have been transferred from these species to wheat. C-banding and in situ hybridization analyses are powerful cytological techniques allowing the detection of alien chromatin in wheat. Cbanding permits identification of the wheat and alien chromosomes involved in wheat-alien translocations, whereas genomic in situ hybridization analysis allows determination of their size and breakpoint positions. The present review summarizes the available data on wheat-alien transfers conferring resistance to diseases and pests. Ten of the 57 spontaneous and induced wheat-alien translocations were identified as whole arm translocations with the breakpoints within the centromeric regions. The majority of transfers (45) were identified as terminal translocations with distal alien segments translocated to wheat chromosome arms. Only two intercalary wheat-alien transloctions were identified, one induced by radiation treatment with a small segment of rye chromosome 6RL (H25) inserted into the long arm of wheat chromosome 4A, and the other probably induced by homoeologous recombination with a segment derived from the long arm of a group 7 Agropyron elongatum chromosome with Lrl9 inserted into the long arm of 7D. The presented information should be useful for further directed chromosome engineering aimed at producing superior germplasm.

Mapping of the leaf rust resistance gene Lr38 on wheat chromosome arm 6DL using SSR markers

“…From a group of wheat-Agropyron intermedium translocation lines developed by Wienhues (1966Wienhues ( , 1973, the A. intermedium chromosome segment 7Ai#2L was found to be present in Wve diVerent translocations all containing Lr38 (Friebe et al , 1996. The 7Ai#2L segments in the Wve translocation lines T4, T7, T24, T25, and T33 were independently transferred to wheat chromosomes 3DS, 6DL, 5AS, 1DL, and 2AL, respectively .…”

Flow cytometric chromosome sorting from diploid progenitors of bread wheat, T. urartu, Ae. speltoides and Ae. tauschii

“…This was significantly higher than the index determined for hexaploid wheat (0.04) after investigating 21 wheat cultivars originating from different location around the world using 33 genomic probes (Cox 1998). Thus, the genetically diverse diploid progenitors represent a huge reservoir of alleles and genes, which could be used to increase the genetic variation of hexaploid wheat through interspecific hybridization (Cox 1998;Friebe et al 1996). Several agronomic traits, including resistance to pests and diseases, tolerance to abiotic stresses and traits affecting nutritional and bread making quality or yield components, were identified in accessions of wild diploid progenitors of wheat.…”

Potential new genes for resistance to Mycosphaerella graminicola identified in Triticum aestivum × Lophopyrum elongatum disomic substitution lines

“…When the seedlings reached the two-leaf stage (7 days post germination), each pot of plants was infested with three newly emerged adult males and females of Hessian fly biotype L, and then covered with a plastic cup. Biotype L, maintained as a purified laboratory stock, is virulent to all known Hessian fly-resistance genes, except for lines containing genes H13 (Ratcliffe et al 1996), H21 (Seo et al 2001), H25 (Friebe et al 1996), H31 (Williams et al 2003), H32 (Sardesai et al 2005) and Hdic (Liu et al 2005). Ten plants from each of the infested pots (total of 20 plants per entry) were selected arbitrarily and scored for resistance 15 days after infestation.…”