Genetic variation in the flowering and yield formation of timothy (Phleum pratense L.) accessions after different photoperiod and vernalization treatments

Abstract

Timothy is a perennial forage grass grown commonly in Boreal regions. This study explored the effect of vernalization and photoperiod (PP) on flowering and growth characteristics and how this related to changes in expression of three flowering related genes in accessions from different geographic origin. Large variation was found in accessions in their vernalization and PP responses. In southern accessions vernalization response or requirement was not observed, the heading date remained unchanged, and plants flowered without vernalization. On the contrary, northern types had obligatory requirement for vernalization and long PP, but the tiller elongation did not require vernalization at 16-h PP. Longer vernalization or PP treatments reduced the genotypical differences in flowering. Moreover, the vernalization saturation progressed stepwise from main tiller to lateral tillers, and this process was more synchronized in southern accessions. The expression of PpVRN1 was associated with vernalization while PpVRN3 accumulated at long PP. A crucial role for PpVRN3 in the transition to flowering was supported as in southern accession the transcript accumulated in non-vernalized plants after transfer to 16-h PP, and the apices transformed to generative stage. Differences in vernalization requirements were associated with variation in expression levels of PpVRN1 and PpVRN3, with higher expression levels in southern type. Most divergent transcript accumulation of PpMADS10 was found under different vernalization conditions. These differences between accessions can be translated into agronomic traits, such as the tiller composition of canopy, which affects the forage yield. The southern types, with minimal vernalization response, have fast re-growth ability and rapidly decreasing nutritive value, whereas northern types grow slowly and have better quality. This information can be utilized in breeding for new cultivars for longer growing seasons at high latitudes.

Agronomic assessment of two populations of intermediate wheatgrass—Kernza® (Thinopyrum intermedium) in temperate South America

“…In addition, the degree to which primary induction requirements have been completed may be modifying the demands of secondary induction requirements, that is, the more complete the primary induction process, the fewer long‐day cycles may be required in secondary induction (L. T. Evans, 1964; Heide, 1994). This said, the interactions between vernalization, cold‐temperature tolerance, photoperiod, flowering, and yields remain largely unclear (Fowler et al, 1996; Jokela et al, 2015; Limin & Fowler, 2006; Seppänen et al, 2013) and require continuous and progressive evaluation of new ecotypes in fields, rather that designing new breeding programs that are decontextualized and based on simplified factors.…”

Process-based analysis of Thinopyrum intermedium phenological development highlights the importance of dual induction for reproductive growth and agronomic performance

“…Phleum pratense) do not require vernalization to achieve flowering (Table S1). Moreover, population diversity, breeding, and plant life-history in fields leads to a certain variability or heterogeneity of inductive requirements among the same species, with the potential formation of cultivars or local ecotypes (Dubcovsky et al, 2006 Cooper andCalder, 1964;Jokela et al, 2015;Palit et al, 2014). Considering IWG, the need of primary induction (vernalization treatment) to ensure proper reproductive growth has been shown previously (Frischknecht, 1959) and has been recently confirmed by field observations and results from controlled experiments (Ivancic et al, under review).…”

Simulation of timothy nutritive value: A comparison of three process-based models

“…The DM yield and nutritive value of the timothy vary with growing conditions and management practices, such as cutting and fertilisation regimes (Bélanger et al, 2001). In addition, the relationship between development, growth and nutritive value varies between timothy cultivars (Jokela et al, 2015). Length of the growing season, temperature and precipitation patterns during the growing season and conditions in the previous winter are particularly important for growth, yield development and management of this species.…”