Document Type : Research Article
Authors
1 Horticulture Crops Research Department, Chaharmahal and Bakhtiari Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension organization (AREEO), Shahrekord, Iran
2 Horticulture Crops Research Department, Isfahan Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension organization (AREEO), Isfahan, Iran
Abstract
Evaluation of Drought Tolerance in Some Almond Commercial Cultivars (Prunus dulcis Mill.) on GN Vegetative Rootstock
Introduction
Peach×almond (GN) hybrid rootstocks have favorable characteristics such as ease of rooting, favorable growth vigour, resistance to nematodes, calcareous and dry soil (Babadaei et al., 2018). Currently, water deficiency because of the decrease in rainfall is one of the important concerns and a key limitation in the production of agricultural products (Hass et al, 2021). Under drought stress, plant cell membranes are sensitive to electrolyte leakage. Membrane leakage is caused by uncontrolled free radicals and leads to lipid peroxidation (Cheng et al. 2018). Since tolerance to drought stress is the result of the interaction of morphological and physiological traits of plant, therefore, a combination of different traits that have a direct relationship with drought tolerance can be used as selection criteria to screen the ideal cultivar (Karimi et al., 2015).
Material and methods
This research carried out during the years 2020 and 2021 at the Chahartakhteh station affiliated to the Center for Research and Education of Agriculture and Natural Resources in Chaharmahal and Bakhtiari Province. The almond seedlings included Shahroud 6, 7, 8, 10, 12, 13 and 21, that all of them grafted on the GN rootstock, along with GN rootstock, subjected to different drought stress treatments in June for four months. Drought stress treatments included 70% of field capacity (control or no drought stress), 50% field capacity (mild stress), 30% field capacity (moderate stress) and 10% field capacity (severe stress). A counter determined the amount of irrigation in each treatment, and a Time-Domain Reflectometry (TDR) used to measure the soil moisture. Before the experiment, the physicochemical properties of the soil measured. The measured morphological traits included leaf area, percentage of leaf abscission, and shoot fresh and dry weight. These traits measured four months after subjecting to water stress. The evaluated physiological traits included electrolyte leakage (EL), relative leaf water content (RWC), leaf chlorophyll, proline and malondialdehyde (MDA). These traits also measured four months after subjecting to water stress. The experiment conducted in split plots based on a randomized complete block design in three replications and four seedlings in each experimental unit. The main plot included water drought treatments and the sub plot included almond cultivars. Data analysis carried out using SAS software version 9.2 and comparison of mean data conducted based on LSD test at a five percent probability level.
Results and discussion
As the intensity of drought stress increased, the fresh and dry weight of shoot decreased in almond cultivars and GN rootstock. At soil humidity of 10% field capacity, Shahroud 8 showed higher amounts of shoot fresh weight (785 g). The lowest fresh and dry weight of the shoot and the highest leaf abscission were observed under severe drought stress (10% of the field capacity) in Shahroud 13. The increase in drought levels led to a decrease in the leaf area in the studied cultivars and rootstock of almond. Shahroud 8 had more chlorophyll content than other cultivars at the most severe stress level, and Shahroud 13 showed the lowest chlorophyll b content at 10% humidity of field capacity. A significant decrease in leaf chlorophyll concentration under drought stress has also been reported in previous research (Schlemmer et al., 2005; Gohari et al., 2023). A further decrease in chlorophyll could be due to a drastic decrease in RWC under severe stress conditions. According to Ranjbar et al. (2022), the amount of RWC decreased by 32 to 44% under stress conditions in the K13-40 grafted cultivar on the rootstock of bitter almond No. 32. In the current research, the biggest decrease in RWC was in Shahroud 13 with a decrease of 36.85%. The lowest decrease in RWC was also observed in the GN rootstock with a decrease of 20.94%. Shahroud 13 and GN rootstock showed the highest and lowest electrolyte leakage at the highest stress level, respectively. Karimi et al. (2023) also found a significant increase in EL in White, Mamai and Ferragnes cultivars due to the higher sensitivity of these cultivars to water loss. The most difference in MDA value was observed in Shahroud 13 with an increase of 186.35% and the lowest difference was found in Shahroud 10 with an increase of 84.58%. Shahroud 6 produced the highest content of proline under severe water stress. According to the results, Shahroud 13 and then Shahroud 6 were recognized as the most sensitive cultivars. Shahroud 8 and 12 were among the tolerant cultivars. Other cultivars were also between these two groups.
Conclusion
Shahroud 13 was recognized as the most sensitive cultivar with the lowest fresh and dry weight, RWC and the highest ion leakage and MDA at the most severe stress level. After that, Shahroud 6 had high sensitivity. Shahroud 8 was recognized as the most drought tolerant cultivar due to its lowest MDA content, the highest chlorophyll a and b and RWC in the most level of drought. After Shahroud 8, Shahroud 12 was including the tolerant cultivars. Tolerant cultivars can be used in future studies to evaluate the possibility of planting these cultivars in areas with water shortage problems
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