A vernalization-intensity model to predict bolting in sugar beet

Abstract

SUMMARYA new model is presented that relates the numbers of bolters in sugar-beet crops to an intensity of vernalization calculated as the accumulated number of hours between sowing and the end of June that temperatures were between 0 and 13°C, with each temperature within this range differentially weighted for its vernalizing effect. The model allows varieties to be characterized in terms of a threshold number of vernalizing hours needed to induce bolting (the vernalization requirement) and the increase in the proportion of bolted plants with each additional 10 vernalizing hours accumulated above this vernalizing threshold (the bolting sensitivity). When parameterized for variety, the model allows the level of bolting to be predicted for crops sown on specific dates in particular locations.Data from variety-assessment trials done at a wide range of locations throughout the main UK sugar-beet growing areas between 1973 and 2006, and from early sown bolting trials done at a few sites between 2000 and 2008, were used to define specific aspects of the model. These included the range and weightings of vernalizing temperatures, the period during which vernalization occurs, and the temperatures likely to cause plants to become devernalized.The vernalization-intensity bolting model was parameterized and validated using separate subsets of the UK variety-assessment trial data. It was shown to be more discriminating and robust than an existing ‘cool-day’ model, which relates bolting to the number of days from sowing in which the maximum air temperature was below 12°C. Examples are given of the use of the new model to assess the bolting risk associated with early sowing in different regions of the UK, to interpret recent patterns of bolting (especially the large numbers of bolters seen in some commercial crops in 2008), and its potential use as an advisory tool.

Genetic analysis of bolting after winter in sugar beet (Beta vulgaris L.)

“…This model allows the quantification of bolting sensitivity in terms of vwh-thresholds. The results of this study indicated that more recent sugar beet varieties tend to have a higher vernalization requirement with a threshold of 140 vwh than older varieties with a threshold of 120 vwh, reflecting the improved early bolting resistance due to breeding activities (Milford et al 2010).…”

“…However, we could not reproduce the previously observed bolting rate of 0.50 for parent BETA 1773 (bolting rate = 0.12). Milford et al (2010) showed that not only the duration of cold treatment but also temperature is affecting the vernalization response of sugar beet. Therefore, the higher bolting rate of BETA 1773 observed in our initial field experiment might be explained by a lower average temperature of 2.5 °C from November through February (data not shown) compared to a temperature of 5 °C in the cold chamber.…”

“…Although sugar beet cultivars carry the b allele , cold temperatures after sowing could vernalize the plants and lead to bolting before winter (Chiurugwi et al 2013;Milford et al 2010), often referred to as early bolting. As early bolting is undesired during crop production, this has always been addressed in breeding and resulted in improved early bolting resistance of modern cultivars (Milford et al 2010).…”

“…As early bolting is undesired during crop production, this has always been addressed in breeding and resulted in improved early bolting resistance of modern cultivars (Milford et al 2010). …”

“…In the literature, optimum temperatures have been reported between 3 and 9 °C (Bachmann et al 1963;Curth 1962;Smit 1983;Stout 1946). Taking both factors into account, Milford et al (2010) studied the influence of cold temperatures in spring on early bolting of sugar beet. They expressed the length and intensity of cold treatment as vernalization-weighted hours (vwh) and modeled the bolting rate of sugar beet in response to vwh.…”