Morade Amrut Sanjay, Sharma Radha Mohan, Dubey Anil Kumar, Sathee Lekshmy, Kumar Sudhir, Kadam Darshan Manikrao, Awasthi Om Prakash, Kumar Amrender, Yadav Deepak
ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India.
ICAR-National Institute of Abiotic Stress Management, Pune, 413115, India.
BMC Plant Biol. 2025 Jun 4;25(1):753. doi: 10.1186/s12870-025-06823-0.
Drought stress, the most prevalent abiotic stress, has a significant effect on citrus production worldwide. The differential mechanisms to overcome the drought stress has been reported in citrus rootstock genotypes. This study evaluated nine citrus rootstock genotypes, including indigenous rough lemon variants, for drought tolerance. The genotypes were subjected to well-watered, drought stress, and re-watering conditions to assess morphological, physiological, and biochemical responses. High-throughput imaging techniques were employed to non-destructively assess chlorophyll fluorescence, digital leaf area, and plant tissue water content during drought stress.
For rapid and accurate screening of rootstocks, phenomics and physio-biochemical tools were used to know morpho-physiological responses to drought. Citrus rootstock genotype X639 demonstrated superior performance under drought stress conditions. It maintained the highest growth in terms of relative shoot increment (8.09%), number of leaves (79.00), and specific leaf area (62.45 cm g). X639 also excelled in root morphological parameters, including root length, projected area, diameter, surface area, volume, and number of tips, forks, and crossings. Trifoliate hybrids X639 and Troyer citrange exhibited larger stomata (54.73 and 43.82 µm) compared to mono-foliate species, with minimal impact of drought on stomatal pore area. X639 maintained the highest relative water content, membrane and chlorophyll stability indices, leaf gas exchange parameters, and antioxidant enzyme activity. RLC-1 and RLC-4 genotypes showed pronounced accumulation of leaf proline and antioxidant enzymes during drought, contributing to better recovery after re-watering.
In this study, Cleopatra mandarin, Grambhiri, and RLC-2 were identified as drought-susceptible rootstocks based on their responses. Rootstock genotypes X639 and RLC-4 proven a superior drought-tolerant genotypes. Their robust root system enables efficient water uptake and the maintenance of water relations during drought stress. The drought tolerance of X639 was evidenced by its ability to maintain plant tissue moisture, membrane and chlorophyll stability, and higher photosystem II efficiency. High-throughput imaging techniques have proven effective in rapidly assessing and differentiating drought-tolerant and drought-susceptible citrus rootstocks based on their photosystem- II efficiency, leaf area, and tissue water content during induced drought stress. These findings will contribute to the selection and development of drought-tolerant citrus rootstocks to improve citrus production under water-limited conditions.
干旱胁迫是最普遍的非生物胁迫，对全球柑橘生产有重大影响。已有报道指出柑橘砧木基因型克服干旱胁迫的不同机制。本研究评估了包括本地粗柠檬变种在内的9种柑橘砧木基因型的耐旱性。使这些基因型分别处于充分浇水、干旱胁迫和再浇水条件下，以评估其形态、生理和生化反应。采用高通量成像技术在干旱胁迫期间无损评估叶绿素荧光、数字叶面积和植物组织含水量。
为了快速准确地筛选砧木，利用表型组学和生理生化工具了解对干旱的形态生理反应。柑橘砧木基因型X639在干旱胁迫条件下表现出优异性能。就相对新梢增量（8.09%）、叶片数量（79.00）和比叶面积（62.45平方厘米/克）而言，它保持了最高的生长水平。X639在根系形态参数方面也表现出色，包括根长、投影面积、直径、表面积、体积以及根尖、根叉和根交叉的数量。与单叶品种相比，三叶杂种X639和枳橙气孔较大（分别为54.73和43.82微米），干旱对气孔孔径的影响最小。X639保持了最高的相对含水量、膜稳定性指数和叶绿素稳定性指数、叶片气体交换参数以及抗氧化酶活性。RLC - 1和RLC - 4基因型在干旱期间叶片脯氨酸和抗氧化酶积累显著，有助于再浇水后更好地恢复生长。
在本研究中，根据克莱奥帕特拉橘、格兰布里橘和RLC - 2对干旱胁迫 的反应，将它们鉴定为干旱敏感型砧木。砧木基因型X639和RLC - 4被证明是耐旱性优良的基因型。它们强大的根系使其在干旱胁迫期间能够高效吸收水分并维持水分关系。X639的耐旱性体现在其能够保持植物组织水分、膜和叶绿素稳定性以及更高的光系统II效率。高通量成像技术已被证明可有效基于诱导干旱胁迫期间的光系统II效率、叶面积和组织含水量快速评估和区分耐旱及干旱敏感型柑橘砧木。这些发现将有助于选择和培育耐旱柑橘砧木，以提高水分受限条件下柑橘的产量。
