Assessment of cold stress in avocado cultivars based on visual, physiological and biochemical criteria

Abstract

Low temperatures affect avocado plants and their response varies across genetic variants. The objective of this study was to assess cold stress of avocado cultivars based on visual, physiological, and biochemical criteria for evaluating freezing injury in these plants. The avocado cultivars 'Geada,' 'Fortuna,' 'Fuerte,' 'Quintal,' 'Margarida,' and 'Primavera' were subjected to temperatures of −2.5, −4.0, −5.0, and −6.0 °C for 1 h in a growth chamber. Their responses to cold stress were evaluated on the basis of visual damage score, photosynthetic rate, water pressure potential, protein content and enzymatic activity. Moreover, the experimental design was factorial and completely randomized with four replicates of each cultivar. An analysis of variance of the results was performed and the means were compared using Tukey's post-hoc test (p <0.05). Evaluations based on the plants water pressure potential, total protein content, catalase activity, photosynthetic rate, and visual damage score were efficient in estimating the effects of cold stress in avocado plants. Additionally, photosynthesis and visual damage score were significantly correlated in all evaluations, enabling classification of the cultivars in terms of response to cold stress. We found that Fuerte was the most tolerant cultivar followed by Geada. The Primavera was the most sensitive cultivar.

Photosynthetic response and antioxidative activity of ‘Hass’ avocado cultivar treated with short-term low temperature

“…Chloroplast APX existing as both soluble and thylakoid-bound forms provided effective elimination of H 2 O 2 generated both internally and externally 50 . Although CAT and POD had antioxidant activity in response to chilling stress in other avocado cultivars 40 , the enzymes in ‘Hass’ avocado seedlings were not differently activated (Fig. 6 C,D).…”

“…Still, the relationship with photosystem in this study could be described as relatively more straightforward than other biochemical systems. Generally, an increase in the activities prevented the accumulation of H 2 O 2 and consequent cellular damage, suggesting that enzymes may play an important role in plant responses to oxidative stress caused by low temperature 40 . In the leaves in the avocado seedlings treated with 1 and − 2 °C, APX and GR activities increased compared to those before treatment (Fig.…”

“…Since avocado is an evergreen fruit tree, the color changes would be a visual signal for physiological disorders and leaf senescence 39 . The discoloration of leaves in the seedlings treated with – 5 °C for 1 h was shown in various avocado cultivars, including ‘Geada’, ’Fortuna’, ’Fuerte’, ’Quintal’, ’Margarida’ and ’Primavera’ 40 . In grafted one-year ‘Hass’ avocado, exposure from – 2 to – 3 °C for 10 h led to the discoloration and death of leaves within one to three days 3 .…”

“…6 ). Since the activity of individual enzymes varied depending on plant types and growth conditions 17 , 40 , 42 , the activity would be too complicated to understand. Still, the relationship with photosystem in this study could be described as relatively more straightforward than other biochemical systems.…”

Covering young ‘Reed’ avocado trees with shading nets during winter alleviates cold stress and promotes vegetative growth

“…Since young avocado plants are considered to be more susceptible to cold stress compared to adult trees, a competent protection technique should be implemented in the orchards (Zaro et al, 2019). The hypothesis of this study is that shading nets may alleviate cold damage in avocado orwas to evaluate the effect of covering young 'Reed' avocado trees with different shading nets during winter.…”