Degree Type


Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Thomas Lübberstedt


For a long time, petroleum-based fuels have been used to provide energy, but limited supplies along with environmental effects of fossil fuels created the need of alternative and clean energy sources. Grasses in general have a low lignin content compared to woody species which is desirable for ethanol production. Furthermore, other features such as: low water and nutrient requirements, and a high rate of carbon fixation that make grasses desirable for biomass production. Perennial grasses have also environmental advantages such as reduced soil organic matter and tillage requirements compared with annual species. Perennial ryegrass has been increasingly used in Europe as forage grass. In 2004, it represented 40% of the grass seed production area in the European Union. This species has a two-locus systems SI systems which has been described for other grasses such as rye and switchgrass. For allogamous grasses, selfing rates are considerably low due to SI and the progeny developed by selfing display a strong inbreeding depression (ID). This suggests that grasses are excellent candidates for hybrid breeding. To ensure 100% hybrid seed production, controlled pollinations are required. For ryegrass, male and female organs coexist in the same floral structure and emasculation can be laborious. Conveniently, SI is a built-in pollination control system that can be exploited in hybrid seed production. The objectives of this research are to; i) discuss the perspectives for hybrid breeding in bioenergy grasses; ii) develop a tool to calculate pollen compatibility for self-incompatible allo-and autotetraploid species; iii) map a new source of self-fertility in ryegrass; and iv) determine the inheritance of polymorphic markers close to the Z gene to validate the self-incompatibility model in tetraploid ryegrass and its effectiveness at a higher ploidy level

Copyright Owner

Andrea Sofia Arias Aguirre



File Format


File Size

104 pages