Tillerbox: an easy-to-use tool to efficiently assess tiller density in grassland

Perennial ryegrass (Lolium perenne L.) is an important grass species in temperate regions due to its high forage quality and its high productivity. To maintain this productivity over time, high persistence is key. Tiller density is a trait strongly associated with persistence and is traditionally measured by manually counting tillers in swards. Even though this method is still considered state-of-the-art, it is intensive in labour and time. Therefore, a reliable high-throughput method would be highly valuable. Here we suggest such a method to assess tiller density using images taken with a self-designed ‘Tillerbox’. The ‘Tillerbox’ is a portable, waist-high box, containing a camera, enabling both standardised conditions and measurements independent of weather conditions. An image covers approx. 1800 cm2, which is at least ten times more than what is usually covered by manual counting. This makes our method especially suitable for tiller density analysis of heterogeneous swards. The images of swards of perennial ryegrass revealed significant differences in tiller density between diploid and tetraploid cultivars, which is in line with other studies. We anticipate our method to be a valuable tool for breeders to facilitate the monitoring of persistence of ryegrass in grassland.