QTL identification for leaf senescence in perennial ryegrass (Lolium perenne L.)

In plants, lifespan is agronomically important as it is a major determinant of productivity. The onset of leaf senescence is associated with decrease of in photo-synthetic capability that reduces herbage yield and biomass production. This re-search aims to identify genes/quantitative trait loci (QTL) that can prolong photo-synthesis and delay the senescence processes in Lolium perenne. This is vital for understanding of the mechanism of senescence and also for practical purposes such as improvement of productivity, silage and hay quality and stress tolerance. A linkage map of an F2 Lolium perenne population derived from a cross between genotypes of the cultivars Aurora and Perma was developed by IBERS consisting of 7 linkage groups. This same population was used for the characterisation of leaf senescence related traits. Four different phenotyping activities were conducted namely: (1) detached leaf senescence under natural light; (2) dark-induced senescence of detached leaves; (3) attached leaves grown in a controlled environment and (4) attached leaves grown under unheated green green-house conditions with natural light.

One major QTL for leaf senescence was identified on linkage group 2. This QTL is robust and consistent as it was detected in four different conditions. The traits on visual color index, chlorophyll fluorescence and chlorophyll loss were mapped with an LOD of >3.0. There were also three minor QTLs for leaf senescence relat-ed traits on linkage in linkage group 3, 4 and 6.