Abstract
The fig tree is a well-adapted and promising fruit tree for sustainable production in arid and semi-arid areas worldwide. Recently, Iran’s dryland fig orchards have been severely damaged due to prolonged severe and consecutive drought periods. As emphasized in many studies, ploidy manipulated plants have a significantly enhanced drought tolerance. In the current study, we compared the induced autotetraploid explants of two fig cultivars (‘Sabz’ and ‘Torsh’) with their diploid control plants for their water stress tolerance under in vitro conditions using different polyethylene glycol (PEG) concentrations (0, 5, 10, 15, 20, and 25%). After 14 days of implementing water stress treatments, the results revealed that both tetraploid genotypes survived at 20% PEG treatments. Only ‘Sabz’ tetraploid explants survived at 25% PEG treatment, while both diploid control genotypes could tolerate water stress intensity only until 15% PEG treatment. The results also demonstrated that the tetraploid explants significantly had a higher growth rate, more leaf numbers, and greater fresh and dry weights than their diploid control plants. Under 15% PEG treatment, both tetraploid genotypes could maintain their relative water content (RWC) at a low-risk level (80–85%), while the RWC of both diploid genotypes drastically declined to 55–62%. The ion leakage percentage also was significantly lower in tetraploid explants at 15% PEG treatment. According to the results, these superiorities could be attributed to higher levels of stress response hormones including abscisic acid, salicylic acid, and jasmonic acid at different PEG treatments, the robust osmotic adjustment by significantly increased total soluble sugar (TSS), proline, and glycine betaine contents, and augmented enzymatic defense system including significantly increased superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione peroxidase (GPX) activities in tetraploid genotypes, compared to their diploid control genotypes. Consequently, the current study results demonstrated that the ‘Sabz’ tetraploid genotype had a significantly higher water stress tolerance than other tested genotypes.
Highlights
With the intensifying adverse effects of climate change, water stress has become a worldwide crisis and threat to agricultural development, especially in arid and semi-arid areas (Rai et al, 2011)
Analysis of variance showed that the interaction effects between cultivar, Ploidy level, and polyethylene glycol (PEG) treatments were significant for all measured traits
15% PEG treatment is identified as the critical water stress level in the present study due to the diploid genotypes not surviving in higher concentrations
Summary
With the intensifying adverse effects of climate change, water stress has become a worldwide crisis and threat to agricultural development, especially in arid and semi-arid areas (Rai et al, 2011). The fig (Ficus carica L.) is a fruit tree from the Moraceae family, well-adapted to the arid and semi-arid areas worldwide, including Mediterranean regions and the Middle East, due to its great tolerance to harsh climates (Flaishman et al, 2008; Falistocco, 2009). During the last two decades, severe and consecutive drought periods and shifting precipitation patterns influenced by climate change have seriously damaged fig production and industry in Iran. Developing efficient breeding methods to achieve highly drought-tolerant cultivars and/or rootstocks is necessary to maintain sustainable production and future demand (Flaishman et al, 2017; Abdolinejad et al, 2020)
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