Genetics of frost hardiness in Juglans regia L. and relationship with growth and phenology

Abstract

The growing interest in broadleaf timber plantations in the Mediterranean area has promoted several studies focusing on the identification and characterization of variability sources in main timber-producing species. J. regia is one of these species, well-adapted to this area, but with freezing, damages registrations. Breeding focused on productive traits should include knowledge of adaptation, required to obtain a good selection capable of producing a suitable turnover in timber plantations. In this study, the features evaluated were autumn and winter frost hardiness and some vegetative traits on 22 half-sib J. regia progenies. Budsticks were exposed to sub-zero temperatures in a controlled chamber and using measurements of relative electrolyte content, the LT50 values (°C) were calculated by each individual. The study was carried out on seven-year-old progenies. The familiar heritability of autumn frost hardiness was 0.68, and on winter, it was 0.77. The autumn frost behaviour correlated genetically with the length of the growing season (0.574 ± 0.351), and both autumn and winter frost hardiness correlated inversely with secondary annual growth measured at breast height (−0.654 ± 0.259 and −0.740 ± 0.227, respectively). These results pointed that growth could therefore be improved without increasing the frost vulnerability. This should be important for growers, particularly under climate change conditions

Dynamic Modeling of Carbon Metabolism During the Dormant Period Accurately Predicts the Changes in Frost Hardiness in Walnut Trees Juglans regia L.

“…In walnut trees, significant genotypic effect has been observed for eco-dormancy release and cold deacclimation (Charrier et al, 2011). Calibrating such a model on different walnut genotypes would bring new perspectives in identifying the variability in carbon metabolism related iso-enzymes and unraveling the genetic basis in frost hardiness variability (Guàrdia et al, 2016; Charrier et al, 2018). This could help the breeder for genetic analysis, especially when current production areas are expected to shift due to climate change.…”

Walnut: past and future of genetic improvement

“…They must also be well adapted to French climatic conditions, specifically winter hardiness so with late bud break to avoid late spring frosts but also with rapid fruit development. A team of INRA Clermont-Ferrand has been working on winter hardiness and found that the high heritability of autumn and winter hardinesses, and the lack of correlation with growth traits, may provide interesting selection pathways (Guàrdia et al 2016). However, the development of dedicated models highlighted that early frost damages, although lower than at other times of the leafless period, would negatively influence fruit yield in the following year (Charrier et al 2017).…”

Assessing frost damages using dynamic models in walnut trees: exposure rather than vulnerability controls frost risks

“…Under extended warm conditions during autumn, frost damages may be critical (Guàrdia et al . , ). Frost hardening, which is tightly connected to chilling exposure, may be subsequently delayed until the moment of first freezing event (Kalberer et al ; Arora & Taulavuori ).…”

“…Autumn period with warmer conditions therefore deserve a particular attention in upcoming studies (Charrier & Améglio ; Guàrdia et al . , ).…”