Molecular mapping of Russian wheat aphid resistance from triticale accession PI 386156

The Russian wheat aphid (RWA), Diuraphis noxia Mordvilko, is an economic pest of wheat (Triticum aestivum L,) in some western growing regions. Sources of resistance occur within the wheat gene pool, but there are also high levels of resistance in wheat relatives, including rye (Secale cereale L.). An F-2 population between PI 386156, a Russian wheat aphid-resistant triticale (x Triticosecale Wittmack) from Russia and NE88T222, a susceptible triticale, was used to examine the inheritance of resistance. Five distinct classes of reaction to the RWA were observed, suggesting this trait is not controlled by a single dominant gene in this population. Bulked segregant analysis was performed with DNA from plants representing the most resistant ('R') and most susceptible ('S') classes. A co-dominant marker amplified by primer OP-M09 explained more than 55% of the variation observed for resistance. Sequencing results revealed a deletion in the 'S' parent relative to the 'R' parent. Using a set of wheat-rye addition lines, we mapped the target fragment to chromosome 4R, which has previously been identified as the critical chromosome for RWA resistance from PI 386156 and other Russian triticales.