Frost Hardiness Expression and Characterisation in Wheat at Ear Emergence

Abstract

Occasionally, wheat can be exposed to overnight freezing temperatures whilst it is in the early reproductive stage and considerable frost damage can occur. In the vegetative stage, full expression of frost tolerance genes can be gained when plants are exposed to acclimation temperatures (4 °C). Paradoxically, wheat during flowering has limited or no ability to effectively acclimate or re‐acclimate and it demonstrates frost sensitivity during this stage. Using a combined approach involving infrared thermography and molecular analysis, the causes and effects of frost‐induced damage to wheat during ear emergence were investigated. It was demonstrated that frost damage only occurs to wheat ears if the temperature falls below −5 °C but some ears, and some spikelets on frozen ears do not freeze but supercool and escape freezing. In whole plant freezing experiments, spikelets showed both complete and partial sterility upon maturation and this was linked to parallel infrared observation of detached ears showing full or partial freezing of spikelets. It was hypothesised that wherever spikelet freezing occurred the spikelet was sterile and grain production per ear was drastically reduced, and in contrary, spikelet survival was as a result of supercooling. Molecular analysis of the upregulation of Cbf14 showed that as ear emergence progressed the ability to induce Cbf14 decreased but at early stages of ear emergence Cbf14 was able to be induced by exposure to acclimating temperatures (4 °C). The hypothesis that the lack of the ear to acclimate is because of the incapability to induce the CBF transcription factor was only partially upheld in this investigation. Further work is needed to elucidate more precisely the molecular incompetency for the acclimation of wheat during ear emergence.

Chilling to zero degrees disrupts pollen formation but not meiotic microtubule arrays in Triticum aestivum L.

“…The ability of plant tissues to avoid ice formation when chilled below 0 °C (supercooling) is a protective condition sought by researchers (Al‐Issawi et al . ), but has also been reported as resulting in reduced yields in Hartog under experimental conditions (Fuller et al . ).…”

Molybdenum application enhances antioxidant enzyme activity and COR15a protein expression under cold stress in wheat

“…Some plants can improve their tolerance to low temperatures through a process known as cold acclimation when they are exposed to low non-freezing temperature (0-4°C) (Thomashow 1999;Fowler 2007;Al-Issawi et al 2013a). During the acclimation process, many cellular changes occur such as the accumulation of osmoprotectants such as soluble sugars (Uemura et al 2003), amines, and compatible solutes such as polyols, proline and betaine (Allard et al 1998;Naidu 1998), via activation of low-temperature signal transduction pathways, which eventually lead to membrane stability and altered gene expression to provide tolerance (Thomashow 2010).…”

Perturbation of nutrient source–sink relationships by post‐anthesis stresses results in differential accumulation of nutrients in wheat grain

“…While nutrient fluxes have often been described under optimal growth conditions, much of the world's wheat is grown in areas that suffer abiotic stresses during grain filling, that alter source–sink relationships including frost stress and heat stress which cause floret sterility/abortion ( Ferris et al, 1998; Saulescu and Braun , 2001; Al‐Issawi et al, 2012) and terminal drought—the major cause of grain yield variability in wheat ( de Oliveira et al, 2013). Under post‐anthesis water deficit, wheat plants generally remobilize a greater proportion of stored leaf carbohydrate to developing grains, but the result is still typically a net loss of yield compared to unstressed plants ( Yang et al, 2001).…”