Multi-environment Screening of Timothy (Phleum pratense) Breeding Material for Better Forage Yield in Sweden.

Sammanfattning: Timothy (Phleum pratense) is one of the most widely used forage crops in hay and pasture grass mixtures in Nordic countries; it’s also used in areas where it is one of the top forage crops harvested high yield, especially in boreal climates. There hasn’t been any large-scale breeding of Timothy to develop varieties that are adapted for Swedish climate and standards, which is surprising given that Timothy is the main forage crop used in Sweden. This thesis is a part of a bigger project which aims for developing a “starter package” that offers a more efficient breeding method to commercial actors, which can be implemented together with traditional breeding for the development and improvement of new varieties of Timothy that enable sustainable farming. This study is aimed to evaluate eco-agronomic traits such as fresh weight (cut), dry matter (DM), and botanical development stage (botdev) among advanced breeding material of timothy and estimate the impact of genotype-by-environment interactions (GEI) by testing the material at three geographic locations. A set of 264 modern accessions developed by Lantmännen were grown at three sites (Röbäcksdalen (RBD), Lövsta (LVT), and Svalöv) in Sweden together with two check varieties (Switch and Tryggve) that are well-known commercial varieties. The field trial was conducted according to a modified block design. The results of an Anova indicated a significant difference in yield among the modern accessions. There was a significant difference between the length of growing degree days in RBD and LVT. The genetic variability analyses reveal the broad-sense heritability increase across the season from DM1 to DM3 and that the genetic gain was higher than environmental effects in LVT. However, the environmental effects were large for the traits DM1 and DM3 in RBD. The suggestion is that DM2 could be more efficiently bred among the modern accessions for the site RBD, while in LVT all three DM could be bred to increase the yield. A combination of PCA and GEI reveals a significant effect on accessions and the environment. The conclusions are based on a combination of analyses such as PCA, GEI and genetic variability analyses and indicates suitable parental lines as we demonstrate here. Furthermore, these findings can speed up the breeding program and understanding of the GEI of Timothy in Sweden. There is an imperative need for a comprehensive understanding of the GEI of Timothy for today and future challenges and opportunities, to comply with climate changes. Additionally, more harvesting years and locations will provide a better understanding of the GEI of Timothy, an experiment of this kind is currently underway at the Swedish University of Agriculture.