Gb8, a new gene conferring resistance to economically important greenbug biotypes in wheat.

A new greenbug resistance gene Gb8 conferring broad resistance to US greenbug biotypes was identified in hard red winter wheat line PI 595379-1 and was mapped to the terminal region of chromosome 7DL. Greenbug [Schizaphis graminum (Rondani)] is a worldwide insect pest that poses a serious threat to wheat production. New greenbug resistance genes that can be readily used in wheat breeding are urgently needed. The objective of this study was to characterize a greenbug resistance gene in PI 595379-1, a single plant selection from PI 595379. Genetic analysis of response to greenbug biotype E in an F population derived from a cross between PI 595379-1 and PI 243735 indicated that a single gene, designated Gb8, conditioned resistance. Linkage analysis placed Gb8 in a 2.7-Mb interval in the terminal bin of chromosome 7DL (7DL3-082-1.0), spanning 595.6 to 598.3 Mb in the Chinese Spring IWGSC RefSeq version 1.0 reference sequence. Gb8 co-segregated with a newly developed SSR marker Xstars508, positioned at 596.4 Mb in the reference sequence. Allelism tests showed that Gb8 was different from three permanently named genes on the same chromosome arm and the estimated genetic distance between Gb8 and Gb3 was 15.35 ± 1.35 cM. Gb8 can be directly used in wheat breeding to enhance greenbug resistance.