نوع مقاله : مقاله پژوهشی
نویسندگان
1 دانشجوی دکتری، گروه زراعت و گیاهان دارویی، دانشکده کشاورزی، دانشگاه آزاد واحد شهرکرد، شهرکرد، ایران.
2 استادیار، بخش تحقیقات علوم زراعی و باغی، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان چهارمحال و بختیاری، سازمان تحقیقات، آموزش و ترویج کشاورزی، شهرکرد، ایران.
3 دانشیار، مرکز تحقیقات تغذیه و محصولات ارگانیک، دانشگاه آزاد اسلامی واحد شهرکرد، شهرکرد، ایران.
4 استادیار، بخش تحقیقات خاک و آب، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان چهارمحال و بختیاری، سازمان تحقیقات، آموزش و ترویج کشاورزی، شهرکرد، ایران.
چکیده
کلیدواژه‌ها
عنوان مقاله [English]
نویسندگان [English]
The present research was conducted to evaluate the response of different almond cultivars to drought stress. The experiment was carried out as split plot arrangement is in randomized complete block design with three replications in the Agricultural and Natural Resources Research Center of Chaharmahal and Bakhtiari, ShahreKord, Iran, in 2020 and 2021. Different irrigation periods based on the available soil moisture; 70%, 50%, 30% and 10% of field capacity were assigned to the main plots and 13 commercial almond cultivars; Mamaei, Rabie, Saba, Araz, Eskandar, Aidin, Shahrood 6, 7, 8, 10, 12, 13, 21 and GN clonal rootstock, were randomized in the subplots. All commercial almond cultivars were grafted on GN clonal rootstock. The plants were under water stress for four months and antioxidant enzymes activity was measured at the middle (two months after application of stress) and the end (four months after application of stress) of drought stress period. The results showed that drought stress significantly decreased fresh and dry weight of the above-ground parts of all cultivars. The lowest effect of drought stress was recorded in cv. Shahrood 8 and GN clonal rootstock. Malondialdehyde content and electrolyte leakage in all almond cultivars significantly increased with increasing drought intensity. In both the middle and end of drought stress period, cv. Shahrood 8, cv. Shahrood 12 and GN clonal rootstock showed the highest chlorophyll index and the lowest malondialdehyde content and electrolyte leakage under severe drought stress (10% FC). Under severe drought stress, the highest antioxidant capacity of enzymes was recorded in cv. Shahrood 12, cv. Shahrood 8 and GN clonal rootstock. Considering the results of this research, under different levels of drought stress, cv. Shahrood 8, cv. Shahrood 12 and GN clonal rootstock had the highest above-ground fresh and dry weight, chlorophyll index and antioxidant enzymes activity, and the lowest peroxidation level that showed the high level of tolerance to water deficit stress.
Keywords: Almond, chlorophyll index, stress period, oxidative stress, tolerant cultivar.
Introduction
Changing climate, global warming and water scarcity necessitate identifying and introducing tolerant crop varieties to environmental stresses. The water shortage is the main restricting factor for different horticulture crops in regards to yield and quality of production. The plant response to different levels of water stress is complex that determines the sensitivity or tolerance of plants to water deficiency (Yanget al., 2021). However, variation in growth, physiological and phytochemical process are the common response of different plant species to unfavorable environment conditions. The accumulation of reactive oxygen species (ROS) in plant tissues under drought stress adversely affects the main physiological and biochemical processes (Hernandez-Santana et al., 2016). The plant defense system for detoxifying of ROS accumulation under drought stress comprises the enzymatic (e.g. catalase (CAT), peroxidas (POX), superoxide dismutase (SOD), Glutathione peroxidase (GPX)) and non-enzymatic compounds (e.g. phenols, proline, glycin betaein, soluble carbohydrate) (Waszczak et al., 2018). Almond tree is known as drought-tolerant crop, however, in arid and semi-arid conditions, water deficit restricts the nut yield and its quality (García Tejero et al., 2018). The present study was aimed to assay the growth, chlorophyll index, peroxidation level, and antioxidant enzymes activity of 14 commercial almond cultivars under different imposed drought stress levels during the middle and end of growing season.
Materials and Methods
The experiment was carried out as split plot arrangement is in randomized complete block design with three replications in the Agricultural and Natural Resources Research Center of Chaharmahal and Bakhtiari, ShahreKord, Iran, in 2020 and 2021. Different irrigation regimes based on the available soil moisture; 70%, 50%, 30% and 10% of field capacity were assigned to the main plots and 13 commercial almond cultivars; Mamaei, Rabie, Saba, Araz, Eskandar, Aidin, Shahrood 6, 7, 8, 10, 12, 13, 21 and GN clonal rootstock, were randomized in the subplots. All commercial almond cultivars were grafted on GN clonal rootstock. The plants were under water stress for four months (from early June) and antioxidant enzymes activity was measured at the middle (two months after application of stress) and the end (four months after application of stress) of drought stress period.
At the middle and the end of drought stress period, the leaves of plants of each cultivar were sampled and frozen rapidly, and then transferred to laboratory for biochemical assays. The chlorophyll index was measured using a chlorophyll meter. Electrolyte leakage and malondialdehyde were determined as lipid peroxidation index. Catalase (CAT) activity was detrmined according to the H2O2 extinction coefficient of 39.4 mM-1 cm-1 as mmol decomposed H2O2 per min (one unit) per mg soluble protein. The peroxidase (POX) activity was measured by guaiacol substrate. The POX activity was measured as mmol produced tetraguaiacol per min per mg soluble protein (Unit mg-1 protein) using the tetraguaiacol extinction coefficient of 25.5 mM-1 cm-1. The activity of Superoxide dismutase (SOD) enzyme was assayed according to its ability to inhibit the photochemical reduction of nitro blue tetrazolium (NBT). The glutathione peroxidase (GPX) activity was calculated in mmol oxidized NADPH in one min per mg protein (units per mg soluble protein) using an extinction coefficient of 6.62 mM-1 cm-1.
Results and Discussion
Combine analysis of variance showed that year, drought stress, cultivar and the interaction effect of drought × cultivar significantly affected all traits (except chlorophyll index). The aboveground fresh and dry weight of almond cultivars considerably decreased with increasing the drought level. Shahrood 8 cultivar and GN clonal rootstock had the highest biomass under severe drought stress. The chlorophyll index in the leaves of almond cultivars significantly decreased with increasing drought stress level due to damage and break of the pigments as well as decomposition of chlorophylls. Under drought stress, the lowest chlorophyll index was recorded in cv. Saba and the highest in cv. Shahrood 8 and GN clonal rootstock. Also, in all studied almond cultivars, with increasing drought stress level, the electrolyte leakage and malondialdehyde content showed increasing trend.
In both drought stress period cv. Shahrood 12, cv. Shahrood 8 and GN clonal rootstock had the lowest electrolyte leakage. However, cv. Shahroud 13 had the highest electrolyte leakage and lipid peroxidation under drought stress. The almond cultivars showed significant differences for antioxidant enzymes activity under different levels of drought stress. Antioxidant enzymes activity increased during the stress period. Under severe drought stress, the highest activity of CAT enzyme was measured in cv. Shahrood 12, cv. Shahrood 8 and GN clonal rootstock. The highest peroxidase and SOD activity measured in GN clonal rootstock under severe drought stressed levlel. Under severe drought stress, the highest GPX activity was determined in cv. Shahrood 8 and GN clonal rootstock. Considering the results of this research, under different levels of drought stress, cv. Shahrood 8, cv. Shahrood 12 and GN clonal rootstock had the highest aboveground fresh and dry weight, chlorophyll index and antioxidant enzymes activity, and the lowest peroxidation level that showed the high level of tolerance to water deficit stress.
References
García Tejero, I.F., Moriana, A., Rodríguez Pleguezuelo, C.R., Durán Zuazo, V.H. and Egea, G. 2018. Sustainable deficit-irrigation management in almonds (Prunus dulcis L.): Different strategies to assess the crop water status. Pp.271-298. In: García Tejero, I.F. and Durán Zuazo, V.H. (eds.) Water scarcity and sustainable agriculture in semiarid environment: tools, strategies and challenges for woody crops. Academic Press. Cambridge, MA, USA. DOI: 10.1016/B978-0-12-813164-0.00012-0
Hernandez-Santana, V., Rodriguez-Dominguez, C.M., Fernández, J.E. and Diaz-Espejo, A. 2016. Role of leaf hydraulic conductance in the regulation of stomatal conductance in almond and olive in response to water stress. Tree Physiology, 36, pp.725-735. DOI: 10.1093/treephys/tpv146
Waszczak, C., Carmody, M. and Kangasjarvi, J. 2018. Reactive oxygen species in plant signaling. Annual Review of Plant Biology, 69, pp.209-236. DOI: 10.4161/psb.22455
Yang, X., Lu, M., Wang, Y., Wang, Y., Liu, Z. and Chen, S. 2021. Response mechanism of plants to drought stress. Horticulturae, 7(3), 50. DOI: 10.3390/horticulturae7030050
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