Androgenesis as a means of dissecting complex genetic and physiological controls: selecting useful gene combinations for breeding freezing-tolerant grasses

The advantages of androgenesis from Lolium × Festuca hybrids as a means towards enhanced gene expression and capture of rare genetic variation are reviewed. New evidence is presented for the technique’s use in combination with introgression-mapping for targeting Festuca-derived genes for enhanced freezing-tolerance. As a starting point, a dihaploid genotype derived by androgenesis from a Lolium multiflorum × Festuca pratensis amphiploid (2n = 4x = 28) hybrid cultivar is used as female parent in a backcross breeding programme with L. multiflorum (2n = 2x = 14). A derivative of the backcross␣breeding programme was a genotype of L.␣multiflorum (2n = 2x = 14) incorporating a F.␣pratensis introgression on chromosome 4 that was more freezing-tolerant than Lolium. New evidence of the importance in Lolium and Festuca species of the adaptive capabilities of Photosystem II (PSII) in relation to subsequent freezing-tolerance, is presented. Non-photochemical quenching (NPQ) mechanisms for expulsion of excess light energy during cold acclimation are found in F. pratensis but not in L. multiflorum. Screens of a backcross population derived from an initial dihaploid genotype (n + n = 14) produced by androgenesis from a L. multiflorum × F.␣pratensis amphiploid, indicate a direct relationship between cold acclimation induced increases in NPQ and freezing-tolerance. Preliminary evidence of a role for genes found on chromosome 4 of F. pratensis for increased NPQ expression, is presented.