Conducting Field Trials for Frost Tolerance Breeding in Cereals.

Cereal species can be damaged by frost either during winter or at flowering stage. Frost tolerance per se is only a part of the mechanisms that allow plants to survive during winter, while winter-hardiness also considers other biotic or physical stresses that challenge the plants during the winter season, limiting their survival rate. While frost tolerance can also be tested in controlled environments, winter-hardiness can only be determined with field evaluations. Post-heading frost damage occurs from radiation frost events in spring during the reproductive stages. A reliable evaluation of winter-hardiness or of post heading frost damage should be carried out with field trials replicated across years and locations to overcome the irregular occurrence of natural conditions which satisfactorily differentiate genotypes. The evaluation of post-heading frost damage requires a specific attention to plant phenology. The extent of frost damage is traditionally determined with a visual score at the end of the winter, although, recently an image-based phenotyping coupled with unmanned aerial vehicles (UAVs) has been proposed.