V. Tiwari,
I. Kamara,
D. Yadav,
V. Irihimovitch,
D. Charuvi

The ongoing climate changes are bringing on more frequent and more extreme weather conditions, among which are frost events. Radiation frosts are characterized by sub-zero temperatures at night/dawn followed by high light during the following clear-sky day. The sequential combination of frost and high radiation conditions can result in substantial damage to sub/tropical plant species. The avocado cultivar ‘Hass’, which is the most popular and sought-after in the world, is cold-sensitive. There are several means for dealing with frost in orchards, e.g., overhead sprinklers or large fans, but not all are practical at every site. Chemical priming, which can improve plants’ coping with various biotic or abiotic stresses, may provide an alternative way for dealing with chilling and frost conditions. Earlier, we found that priming young potted ‘Hass’ trees with sodium hydrosulfide (NaHS) prior to their exposure to simulated frost conditions improved their response to frost. The primed trees exhibited reduced inhibition of CO₂ assimilation, less photoinhibition, a better non-photochemical quenching capacity, and a lower accumulation of hydrogen peroxide in their leaves, compared to untreated trees. In this paper, we describe our trials of priming ‘Hass’ avocado trees with NaHS in commercial orchards. We found that following natural chilling temperatures (1-2°C) in the orchard, primed mature trees had reduced inhibition of photosynthetic assimilation and stomatal conductance, which may last for several days after the treatment. These results are promising, yet the effect of priming still needs to be tested at natural frost conditions.