Comparative Study between the Photosynthetic Parameters of Two Avocado (Persea americana) Cultivars Reveals Natural Variation in Light Reactions in Response to Frost Stress

Abstract

Avocado is a commercially important fruit tree which is sold worldwide. Originating in subtropical regions of the South America, this species is now grown worldwide and is sometimes exposed to cold temperatures. Specifically, frost stress harms the crop yield and its quality. While it is known in general that the photosynthetic apparatus changes in response to cold conditions, there is still not much information regarding the photosynthetic apparatus response to sporadic frost stress. In this study, we tracked the photosynthetic apparatus’ light reaction of ‘Hass’ and ‘Ettinger’ avocado cultivars to frost stress, with Ettinger being known to be more resilient to cold than Hass. We found that in avocado trees, the photosynthetic apparatus’ response to frost occurs at the level of photosystem II (PSII) itself, rather than a photoprotective response to a stress. The Hass apparatus incorrectly interprets the reduction in electron transport rate activity and by that increases its light harvesting complex size at the expense of its reaction centers which then increases the apparatus’ probability to generate reactive oxygen species. The results of this study open opportunities to further research the process which regulates the feedback mechanism that controls the photosynthetic unit’s size in Hass when compared to the Ettinger cultivar, and whether it is part of a feedback regulation from the carbon assimilation step or indirectly from a stomatal limitation which arises in these subtropical species. While corroborating past studies performed on avocados, this study suggests using advanced chlorophyll a fluorescence protocols when researching natural variation in crops.

Phenology of hass avocado in the Andean tropics of Caldas, Colombia

“…In areas close to the equator, the length of the day does not seem to change significantly (YEANG, 2007), and as for solar radiation, Renner (2007) reported that when the sun passes directly over the equator twice a year, a bimodal cyclic change in the incoming solar radiation (insolation) is observed on these regions. point (WEIL et al, 2022). In this research, maximum PAR values above 2,000 µmol/m-2/s-1 were recorded and the average values observed were slightly less than 1,400 µmol/m-2/s-1 (Figure 9 A-B).…”

“…While the three ecological avocado cultivars offer a wide range of adaptation to air temperature (WEIL et al, 2022), for the 'Hass' cultivar in particular, Garner and Lovatt (2016) found that under the southern Australia conditions, only the coldest (17/10°C) and hottest (37/30°C) treatments restricted growth and dry matter accumulation, while…”

“…The 3 avocado cultivars, Mexican, Guatemalan and Antillean, were cultivated in different climatic regions and may show different responses to soil temperature (SILVA et al 2017). Furthermore, it has been shown that there is root growth restriction at soil temperature below 13.5ºC (WEIL et al, 2022). Likewise, soil temperature ranging from 21º to 27° was better for avocado seedling growth, but temperatures above 27° reduce growth (SILVA et al 2017).…”

Agroclimatic and Phytosanitary Events and Emerging Technologies for Their Identification in Avocado Crops: A Systematic Literature Review

“…The light response of two avocado cultivars to sporadic frost stress can have negative results on crop yield and fruit quality, as stated in the study conducted by Weil et al [69]. The focus of the study was on the photosynthetic parameters of these avocado varieties, and the researchers examined their responses to frost stress in four instances both in the laboratory and in the field conditions.…”

Priming avocado with sodium hydrosulfide prior to frost conditions induces the expression of genes involved in protection and stress responses

“…Damage can range from burning of shoots and foliage, damage to flowering buds and fruits and even death of trees in more extreme cases (Witney & Arpaia, 1991;Mandemaker, 2008). Physiological and biochemical aspects of the response of avocado 'Hass' to chilling and frost/freezing have been studied (Joshi et al, 2020;Chung et al, 2022;Weil et al, 2022), focusing on photosynthetic performance, reactive oxygen species (ROS) and antioxidants. Possible horticultural means for mitigating frost damage in 'Hass' orchards include wind machines or highdensity shading nets (Lahak et al, 2024;Bar-Noy et al, 2019).…”