Tetraploidy Confers Superior in vitro Water-Stress Tolerance to the Fig Tree (Ficus carica) by Reinforcing Hormonal, Physiological, and Biochemical Defensive Systems

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.

Production of Tetraploid Plants from Cotyledons of Diploid Melia volkensii Gürke

“…Tetraploid Robinia pseudoacacia L. clones adapted to drought by reducing intercellular CO 2 , net photosynthetic rate, and stomatal conductance more than diploid clones [59]. Tetraploid F. carica clones showed higher tolerance to water stress by maintaining relative water content while producing high levels of stress hormones, enhancing the enzymatic defense system, and adjusting osmotic pressure [60]. Polyploid eucalyptus hybrids are larger in size, have more fibers, and have thicker walls compared to diploid relatives [61].…”

Cytogenetics and Consequences of Polyploidization on Different Biotic-Abiotic Stress Tolerance and the Potential Mechanisms Involved

“…Due to osmotic stress effects, cell plants usually incur damage by producing MDA and other superoxide’s that cause cell membrane disintegration. Tetraploid plants showed lower MDA concentrations for drought tolerance than diploid plants [ 168 , 171 , 173 ]. Although diploids and tetraploids experience increased ROS production due to drought stress, ROS scavenging and ROS homeostasis increased in tetraploids [ 171 , 172 ].…”

“…In addition, some ABA expresser enzymes such as 9-cis-epoxycarotenoid dioxygenase 1 (NCED1), NCED2, and gene expression ABRE binding factor 5-like (ABF5-like) were observed; such phenomena in tetraploids are responsible for increasing ABA synthesis and signaling pathways for stress adaptation. On the other hand, aquaporin genes such as MdPIP1;1 and MdTIP1;1, which are responsible for cell-to-cell water transportation, are expressed less in polyploid plants ([ 168 ] Table 3 ). Overall, morphological growth and chlorophyll content in tetraploids were higher than in diploids during drought stress [ 168 , 169 , 170 , 171 , 172 ] ( Table 3 ).…”

“…On the other hand, aquaporin genes such as MdPIP1;1 and MdTIP1;1, which are responsible for cell-to-cell water transportation, are expressed less in polyploid plants ([ 168 ] Table 3 ). Overall, morphological growth and chlorophyll content in tetraploids were higher than in diploids during drought stress [ 168 , 169 , 170 , 171 , 172 ] ( Table 3 ). Nevertheless, consideration should be given to the relative fitness of different ploidy levels at different drought levels.…”

The creation of autotetraploid provides insights into critical features of DNA methylome changes after genome doubling in water spinach (Ipomoea aquatica Forsk)

“…This speculation still lacks more evidence support. In addition, polyploidy potentiates plant tolerance to abiotic and biotic stresses (Tossi et al, 2022), such as increased resistance to cold and drought (del Pozo and Ramirez-Parra, 2014;Syngelaki et al, 2021;Abdolinejad and Shekafandeh, 2022).…”