Hossein Nastari Nasrabadi; Seyyed Farhad Saber Ali
Abstract
Introduction: Melon (Cucumis melo L.) is one of the most important vegetables in Cucurbitaceae family and one of the most important economic crops in the Torbat-e Jam city (Longitude: 60 ̊48', latitude: 35 ̊31', altitude: 928 m). Growth and yield of agricultural crops are affected by biotic ...
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Introduction: Melon (Cucumis melo L.) is one of the most important vegetables in Cucurbitaceae family and one of the most important economic crops in the Torbat-e Jam city (Longitude: 60 ̊48', latitude: 35 ̊31', altitude: 928 m). Growth and yield of agricultural crops are affected by biotic and abiotic environmental stresses. Cold stress can be one of the most important environmental factors reducing crops yield. Cold acclimation in plant is a complex process involving many morphological, physiological and biochemical changes, including a significant reduction in tissue hydration during cold hardening. Melatonin (MEL, N-acetyl-5-methoxytryptamine) is a conserved substance, which has been discovered in all living organisms, from bacteria to mammals. MEL regulates the growth of root, shoot, and explant, activates seed germination and rhizogenesis, and delays leaf senescence. In addition, the most frequently mentioned functions of MEL are related to various abiotic stresses such as drought, radiation, low/high temperature, heavy metals, and salinity stresses. Materials and Methods: In order to investigate the effect of PEG priming and melatonin on cold stress resistance of melon seedlings, a factorial experiment was conducted in a completely randomized design with three replications in Torbat-e-Jam University. In this experiment polyethylene glycol 6000 was used to produce drought stress at three levels (0, 0.18 and 0.58 MPa) and melatonin was used at two levels (0 and 200 μmol). When melon seedlings were at 4 leaf stage, the amount of polyethylene glycol was added to the irrigation solution for a week and to prevent drought stress, drought stress was increased for 3 days and increased one third of the required concentration daily. Recovery was performed for three days after drought stress and during this period melatonin was added to the irrigation solution at the required concentration. Seedlings were then exposed to cold stress (T0: non-stress and T1: cold conditions). Control plants were kept in greenhouse conditions. Results and Discussion: Comparison of the mean results showed that there was an increasing trend in proline production by increasing drought stress. The highest amount of proline (0.80 µmol g-1 FW) was recorded at the highest level of drought pretreatment with no melatonin and without cold stress (D2M0T0), and then a decreasing trend in proline production was observed. The results showed that melatonin significantly increased leaf relative water content compared to the control. Interaction effects of drought pretreatment and temperature showed that there was a trend of decrease in relative water content by increasing drought pretreatment. Ghanbari and Sayyari (8) reported that drought pretreatment stress maintains relative water content of tomato seedlings under cold stress conditions. Drought pretreatment significantly reduced the amount of chlorophyll a and total chlorophyll. The results showed that the highest levels of drought pretreatment stress (D2) and melatonin (M1) maintained chlorophyll a under cold stress conditions. Results showed that the amount of chlorophyll b was decreased by drought pretreatment stress, but it increased by melatonin application in all compounds. Based on the results, it was found that only simple effects of treatments at 1% of probability level had significant effects on soluble sugars content. Comparison of the mean simple effects of drought pretreatment showed that under drought stress the amount of soluble sugars increased significantly and the highest sugar content was recorded at the highest drought stress level. The amount of soluble sugars in plants under cold stress also increased significantly. Melatonin application also significantly increased the amount of soluble sugars. Kabiri et al. (19) reported that the use of melatonin increased soluble sugars in Moldavian balm seedlings under osmotic stress which is similar to this study results. It was found that melatonin significantly increased phenolic compounds under stress conditions and significantly decreased electrolyte leakage.
Davood Sadeghzadeh Ahari; Mohammad Reza Hassandokht; Abdolkarim Kashi; Ahmad Amri
Abstract
Introduction: Fenugreek (Trigonella foneum-graecum L.) has been cultivated in vegetable farms at the most parts of Iran. It is an annual crop belonging to the Leguminosae family. It originated from west Asia and Iran and cultivated at mostly in European, Asian and African countries, presently. With distinguished ...
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Introduction: Fenugreek (Trigonella foneum-graecum L.) has been cultivated in vegetable farms at the most parts of Iran. It is an annual crop belonging to the Leguminosae family. It originated from west Asia and Iran and cultivated at mostly in European, Asian and African countries, presently. With distinguished of feeding and medicinal values, low needs to soil conditions and its width adaptability to cultivation in different regions, the range of fenugreek cultivation areas have been extended from America to India. In most parts of Iran there is limiting possibilities for cultivation of horticultural and agricultural crops for the reason of limiting water harvesting and unsuitable rainfall distributions. There is no doubt that introduction of new crops for such conditions could increase variation of crops production and stability of farming systems. Plants landraces have been created in thousands of cultivation years under different climatologically and local cropping systems. They are evolved by natural and artificial selection under environmental conditions where they were grown and there have accumulative adaptive genes for tolerance to biotic and abiotic stresses and are the most precious materials in starting of breeding programs. Germination phase is the most important period that guaranties the growth and establishments of crops. One of the basic activators of germination starters is water and limiting of it (drought) is the most important retardant of seed growth during germination period under field condition. Fast germination and emergence of seedling from soil and high preliminary growth rate has been known for one of the drought escape mechanisms for most crops such as chickpea, lentil and bean. In breeding programs of crops, using in vitro method is one of the most used methods in germplasm selection for drought tolerance. This study carried out under laboratory condition in order to evaluate some Iranian fenugreek landraces reactions to drought stress.
Materials and Methods: In order to evaluate the Iranian fenugreek landraces reactions to drought stress induced by Poly Ethylene Glycol 6000, twenty fenugreek landraces originated from different parts of Iran were used in this study. The experiment was conducted at Maragheh experimental station of the Dry land Agricultural Research Institute (DARI) under laboratory condition, with a factorial experiment based on randomized complete blocks design and three replications. The stress levels were zero (di-ionized water),-2, -4,-6 and -8 bar. Fifteen normal and health seeds from each landraces were cultivated in petridishes and stayed under fixed temperature (25±1 degree of centigrade), 12 hour day/night for fourteen days. Seedling characteristics (seed germination percentage, root and stem lengths, ratio of stem length to root length, root and stem fresh weights, ratio of stem fresh weight to root fresh weight, root and stem dry weights) were noted. Data were analyzed by MSTAT-C software and comparisons of noted traits means done by Duncan’s Multiple Range Test at 5% probability level. In order to distinguish tolerant and susceptible genotypes, landraces ranked by using of Sarmadnia et al.,(1988) and Kafi et al.(2005) methods, and with using of the main traits such as seed germination percentage, root and stem lengths, root and stem fresh weights, root and stem dry weights.
Results and Discussion: Results showed that, drought stress levels had significantly affected on all study traits (seed germination percentage, root and stem lengths, ratio of stem length to root length, root and stem fresh weights, ratio of stem fresh weight to root fresh weight, root and stem dry weights). The differences among landraces were highly significant in all traits except in primary root dry weight. The most visible differences among the genotypes in germination percentage monitored at less than -4 bars. Based on ranking of genotypes with seven main studied traits (seed germination percentage, root and stem lengths, root and stem fresh weights, root and stem dry weights), Kashan and Neyshaboor were the most tolerant and Rey and Khash were the most susceptible landraces among the studied genotypes at germination and seedling growth stages.
Conclusion: It could be concluded that, there are differences among the Iranian fenugreek landraces in case of reaction to drought stress at germination and seedling growth stages that shows suitable diversity among them. Moreover, using from less than -4 bar drought stress levels recommended for screening and selection of drought tolerance fenugreek genotypes. Also, it is recommended attention to Iranian fenugreek landraces and using the hidden potentials of them same as drought tolerance and resistance. It is suggested protection of them as a precious genetically resources in gene bank.