Characterization and mapping of cryptic alien introgression from Aegilops geniculata with new leaf rust and stripe rust resistance genes Lr57 and Yr40 in wheat

Abstract

Leaf rust and stripe rust are important foliar diseases of wheat worldwide. Leaf rust and stripe rust resistant introgression lines were developed by induced homoeologous chromosome pairing between wheat chromosome 5D and 5M(g) of Aegilops geniculata (U(g)M(g)). Characterization of rust resistant BC(2)F(5) and BC(3)F(6) homozygous progenies using genomic in situ hybridization with Aegilops comosa (M) DNA as probe identified three different types of introgressions; two cytologically visible and one invisible (termed cryptic alien introgression). All three types of introgression lines showed similar and complete resistance to the most prevalent pathotypes of leaf rust and stripe rust in Kansas (USA) and Punjab (India). Diagnostic polymorphisms between the alien segment and recipient parent were identified using physically mapped RFLP probes. Molecular mapping revealed that cryptic alien introgression conferring resistance to leaf rust and stripe rust comprised less than 5% of the 5DS arm and was designated T5DL.5DS-5M(g)S(0.95). Genetic mapping with an F(2)population of Wichita x T5DL.5DS-5M(g)S(0.95) demonstrated the monogenic and dominant inheritance of resistance to both diseases. Two diagnostic RFLP markers, previously mapped on chromosome arm 5DS, co-segregated with the rust resistance in the F(2) population. The unique map location of the resistant introgression on chromosome T5DL.5DS-5M(g)S(0.95) suggested that the leaf rust and stripe rust resistance genes were new and were designated Lr57 and Yr40. This is the first documentation of a successful transfer and characterization of cryptic alien introgression from Ae. geniculata conferring resistance to both leaf rust and stripe rust in wheat.

Molecular cytogenetic characterization of novel wheat-Thinopyrum bessarabicum recombinant lines carrying intercalary translocations

“…However, because of background translocations and deletions (Comai 2000), relatively few of these lines have been exploitable in breeding programs. In some cases, the alien segment may initially be detected only by plant morphology and subsequently proven by molecular cytogenetic methods (e.g., Barbela), while no alien segment may be seen within situ hybridization but only DNA markers indicate its presence (e.g., transfer to wheat of Lr57 and Yr40 from Aegilops geniculata, Kuraparthy et al 2007). Background wheat translocations and deletions of chromosome segments, as well as aneuploidy are also found in wheat hybrid genetic stocks.…”

Molecular cytogenetic characterization of a new wheat-rye 1BL•1RS translocation line expressing superior stripe rust resistance and enhanced grain yield

“…In some cases, traits of interest are transferred to the recipient crop without cytological changes in its genomic (Multani et al 1994). Such cryptic translocation is alien introgression that can be undetected by cytological methods and rarely a few molecular markers (Kuraparthy et al 2007a). Kuraparthy et al (2007a, b) demonstrated that it was feasible to transfer rust resistance genes with minimal linkage drag from Aegilops geniculata and Ae.…”

Molecular cytogenetic identification of a wheat (Triticum aestivum)-American dune grass (Leymus mollis) translocation line resistant to stripe rust

“…One reality is that the replacement of highly variable land races by high-yielding, pure-line varieties in many parts of the world has narrowed the genetic base for disease resistance in the wheat gene pool (Kuraparthy et al, 2007a). Fortunately, relatives of wheat have been found to be invaluable sources of disease-resistance genes (Jiang et al, 1994;Friebe et al, 1996).…”

“…Fortunately, relatives of wheat have been found to be invaluable sources of disease-resistance genes (Jiang et al, 1994;Friebe et al, 1996). So far, an increasing number of stripe rust resistance genes originating in the wild relatives of wheat have been identified, such as Yr9 from Secale cereale (the Komugi Wheat Genetic Resources Database, seeing the reference b for the URL [http://www.shigen.nig.ac.jp/ wheat/komugi/genes/symbolDetailAction.do?geneId=1637]), Yr28 from Aegilops tauschii (Singh et al, 2000), and Yr40 from Aegilops geniculata (Kuraparthy et al, 2007a).…”