Alkhatatbeh Hamad A, Sadder Monther T, Haddad Nizar, Al-Amad Ibrahim, Brake Mohammad, Alsakarneh Nawal A, Alnajjar Abdulsalam M
Faculty of Agricultural Technology, Al-Balqa Applied University, Al-Salt, Jordan.
Department of Horticulture and Crop Science, School of Agriculture, University of Jordan, Amman, Jordan.
Front Plant Sci. 2025 Jun 5;16:1549305. doi: 10.3389/fpls.2025.1549305. eCollection 2025.
Water scarcity and soil salinization are increasingly becoming limiting factors in food production, including olives, a major fruit crop in several parts of the world. Investigating historical olives, which are the last resort for genetic resources, is essential due to their natural resilience to drought and salinity, making them valuable for breeding stress-tolerant cultivars and ensuring sustainable olive production.
In this study, four historic olive cultivars ('Nabali', 'Mehras', 'Frantoio', and 'Manzanillo') were investigated under both drought and salinity stresses. These cultivars also preserve local biodiversity, support traditional agriculture, and offer economic opportunities through unique, heritage-based olive oils. Drought and salt stress in olives are assessed through physiological [the ratio of variable to maximum fluorescence (Fv/Fm), relative water content (RWC)], biochemical (proline content), and molecular (stress-responsive genes) analyses to evaluate stress tolerance.
Under salinity and drought stress, RWC decreased in all olive cultivars, with drought having the most severe impact. 'Nabali' exhibited the highest salinity tolerance, while all cultivars showed similar sensitivity to drought. Proline levels remained stable in 'Mehras' but decreased under salinity stress in 'Frantoio', 'Manzanillo', and 'Nabali'. Higher proline accumulation under drought suggested better drought tolerance than salinity in these cultivars. Photosynthetic efficiency (Fv/Fm) declined under salinity and drought stress in all cultivars, with drought causing a more significant reduction. 'Manzanillo' showed the highest sensitivity to drought, while the other cultivars maintained moderate efficiency under stress. 'Manzanillo' and 'Mehras' exhibited the highest number of differentially expressed genes (DEGs) under both drought and salinity stress, with 'Manzanillo' showing 2,934 DEGs under drought and 664 under salinity stress, while 'Mehras' had 2,034 and 2,866 DEGs, respectively. 'Nabali' demonstrated the strongest salinity-specific response, with 3,803 DEGs under salinity stress compared to 1,346 under drought. 'Frantoio' consistently had the lowest number of DEGs, with 345 under drought and 512 under salinity stress, indicating a more stable transcriptional response. Comparative analyses between drought and salinity conditions revealed significant variations, with 'Manzanillo' showing 2,599 unique DEGs under drought relative to salinity stress, while 'Nabali' exhibited 2,666 DEGs under salinity stress relative to drought. The major novel upregulated genes under salinity stress were Xyloglucan endotransglucosylase hydrolase (7 fold in 'Nabali' and 6.9 fold in 'Mehras'). The novel drought genes detected in 'Frantoio' included Phytosulfokines 3 (4.9 fold), while Allene oxide synthase (6.5 fold) and U-box domain-containing (6.4 fold) were detected in 'Manzanillo'.
The data revealed both novel and common stress-specific biomarkers under both salinity and drought stress, which can potentially be utilized in olive breeding and genetic improvement programs to mitigate stress.
水资源短缺和土壤盐渍化日益成为粮食生产的限制因素，其中包括橄榄，橄榄是世界上几个地区的主要水果作物。研究历史悠久的橄榄树是获取遗传资源的最后手段，因其对干旱和盐渍化具有天然的耐受性，对培育耐胁迫品种和确保橄榄可持续生产具有重要价值。
在本研究中，对四个历史悠久的橄榄品种（“纳巴利”、“梅拉斯”、“佛朗托io”和“曼萨尼约”）进行了干旱和盐胁迫试验。这些品种还保护了当地生物多样性，支持传统农业，并通过独特的、基于传统的橄榄油提供经济机会。通过生理分析（可变荧光与最大荧光之比（Fv/Fm）、相对含水量（RWC））、生化分析（脯氨酸含量）和分子分析（胁迫响应基因）来评估橄榄的干旱和盐胁迫耐受性。
在盐胁迫和干旱胁迫下，所有橄榄品种的RWC均下降，干旱的影响最为严重。“纳巴利”表现出最高的耐盐性，而所有品种对干旱的敏感性相似。“梅拉斯”中的脯氨酸水平保持稳定，但在“佛朗托io”、“曼萨尼约”和“纳巴利”中，盐胁迫下脯氨酸水平下降。干旱条件下脯氨酸积累量较高，表明这些品种的耐旱性优于耐盐性。在所有品种中，盐胁迫和干旱胁迫下光合效率（Fv/Fm）均下降，干旱导致的下降更为显著。“曼萨尼约”对干旱最为敏感，而其他品种在胁迫下保持中等效率。“曼萨尼约”和“梅拉斯”在干旱和盐胁迫下差异表达基因（DEG）数量最多，“曼萨尼约”在干旱下有2934个DEG，在盐胁迫下有664个DEG，而“梅拉斯”分别有2034个和2866个DEG。“纳巴利”表现出最强的盐胁迫特异性反应，盐胁迫下有3803个DEG，而干旱下有1346个DEG。“佛朗托io”的DEG数量始终最少，干旱下有345个，盐胁迫下有512个，表明其转录反应更稳定。干旱和盐胁迫条件下的比较分析显示出显著差异，“曼萨尼约”在干旱下相对于盐胁迫有2599个独特的DEG，而“纳巴利”在盐胁迫下相对于干旱有2666个DEG。盐胁迫下主要的新上调基因是木葡聚糖内转糖基酶水解酶（“纳巴利”中为7倍，“梅拉斯”中为6.9倍）。在“佛朗托io”中检测到的新干旱基因包括植物硫肽激素3（4.9倍），而在“曼萨尼约”中检测到丙二烯氧化物合酶（6.5倍）和含U-box结构域的蛋白（6.4倍）。
数据揭示了盐胁迫和干旱胁迫下新的和常见的胁迫特异性生物标志物，这些标志物有可能用于橄榄育种和遗传改良计划，以减轻胁迫。
