Effect of three water-regimes on morpho-physiological, biochemical and yield responses of local and foreign olive cultivars under field conditions

Physiological and biochemical study of the drought tolerance of 14 main olive cultivars in the Mediterranean basin

A complete study of 14 olive cultivars of great economic importance was carried out. These cultivars are Arbequina, Arbosana, Chemlali, Cornicabra, Cornezuelo de Jaén, Empeltre, Frantoio, Hojiblanca, Koroneiki, Manzanilla de Sevilla, Martina, Picual, Sikitita1 and Sikitita 2. All of them are certified by the World Olive Germplasm Bank of Córdoba (Spain). They are predominant cultivars in the olive groves of different locations throughout the Mediterranean basin, and they were subjected to total water deficit for a minimum of 14 days and a maximum of 42 days in the present study. Data such as chlorophyll content, soil moisture and specific leaf area were gathered. Photosynthetic parameters measured at the respective saturation irradiance of each cultivar were also analysed: assimilation rate, transpiration, stomatal conductance, photosynthetic efficiency, photochemical and non-photochemical quenching, photonic flux density, electron transference ratio, efficient use of water and amount of proline and malondialdehyde as indicators of oxidative stress. In addition to the control, two different experimental conditions were analysed: moderate drought, after 14 days of lack of irrigation, and severe drought, after 28-42 days of total absence of irrigation, depending on the tolerance of each cultivar. Based on the results, the cultivars were characterised and divided into four groups according to their drought tolerance: tolerant, moderately tolerant, moderately sensitive and sensitive to drought. This work represents the first contribution of drought tolerance of a considerable number of olive cultivars, with all of them being subjected to the same criteria and experimental conditions for their classification.

Physiological and Biochemical Responses of Commercial Strawberry Cultivars under Optimal and Drought Stress Conditions

Improving the extent of adaptation and the choice of the most tolerant cultivar is the first step to mitigating the adverse effects of limited water, especially in susceptible plants such as strawberries. To address this issue, two commercial strawberry cultivars (Camarosa and Gaviota) were compared when irrigated to match 100, 75, 50, and 25% field capacity (FC) to simulate the control, slight, moderate, and severe drought stress conditions, respectively. Drought stress induced the reduction of total chlorophyll, carotenoid, relative water content, and phenolic content significantly, whereas the activity of antioxidant enzymes, electrolyte leakage, osmolyte accumulation, and oxidative markers upsurged progressively in drought severity-dependent behavior. Gaviota produced more proline, hydrogen peroxide as a marker of membrane lipid peroxidation and disposed of by higher electrolyte leakage, significantly. On the other hand, Camarosa having higher soluble carbohydrates as well as enzymatic and non-enzymatic antioxidants could be considered a drought-tolerant cultivar. Genotypic variation between these cultivars could be used in breeding projects to promote drought-tolerant strawberries in the future.

Overexpression of CpADC from Chinese Cherry (Cerasus pseudocerasus Lindl. 'Manaohong') Promotes the Ability of Response to Drought in Arabidopsis thaliana

Polyamines (PA) play an important role in the growth, development and stress resistance of plants, and arginine decarboxylase (ADC) is one of the key enzymes in the biosynthetic pathway of polyamines. Previously, the transcriptional regulation of the 'Manaohong' cherry under the shelter covering was carried out, and the PA synthase-related genes, particularly the ADC gene, were differentially expressed as exposure to drought stress. However, the mechanisms of how ADC is involved in the response of cherry to abiotic stress (especially drought stress) are still unknown. In the present work, the full-length coding sequence of this gene was isolated and named CpADC. Bioinformatics analysis indicated that the coding sequence of CpADC was 2529 bp in length. Cluster analysis showed that CpADC had the highest homologies with those of sweet cherry (Prunus avium, XP_021806331) and peach (Prunus persica, XP_007200307). Subcellular localization detected that the CpADC was localized in the plant nucleus. The qPCR quantification showed that CpADC was differentially expressed in roots, stems, leaves, flower buds, flowers, and fruits at different periods. Drought stress treatments were applied to both wild-type (WT) and transgenic Arabidopsis lines, and relevant physiological indicators were measured, and the results showed that the putrescine content of transgenic Arabidopsis was higher than that of WT under high-temperature treatment. The results showed that the MDA content of WT was consistently higher than that of transgenic plants and that the degree of stress in WT was more severe than in transgenic Arabidopsis, indicating that transgenic CpADC was able to enhance the stress resistance of the plants. Both the transgenic and WT plants had significantly higher levels of proline in their leaves after the stress treatment than before, but the WT plant had lower levels of proline than that of transgenic Arabidopsis in both cases. This shows that the accumulation of proline in the transgenic plants was higher than that in the wild type under drought and high and low-temperature stress, suggesting that the transgenic plants are more stress tolerant than the WT. Taken together, our results reveal that, under drought stress, the increase in both expressions of CpADC gene and Put (putrescine) accumulation regulates the activity of ADC, the content of MDA and Pro to enhance the drought resistance of Arabidopsis thaliana.