Medicinal Plants
Saghi Keyghobadi; Reza Fotohi Ghazvini; Yahya Tajvar; Atefe Sabouri
Abstract
Introduction
Drought is one of the most important environmental stresses that affects various plants such as ornamental plants. The identification and selection of ornamental tolerant genotypes is essential for landscape projects. Understanding the mechanisms that enable plants to adapt to drought ...
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Introduction
Drought is one of the most important environmental stresses that affects various plants such as ornamental plants. The identification and selection of ornamental tolerant genotypes is essential for landscape projects. Understanding the mechanisms that enable plants to adapt to drought stress can help to select the most tolerant genotypes for cultivation in arid and semi-arid regions.
Materials and Methods
For this purpose, a research was conducted as a factorial experiment based on completely randomized design with eleven genotypes and two levels of irrigation (irrigation as Control and severe drought) at Ramsar Citrus and Tropical Fruits Research Institute.
Results and Discussion
The first symptoms of drought stress were observed after 10 days in the Juniperus horizontalis (G1) genotype (the most sensitive genotype) and were not recovered and dried after 15 days. G3 and G5 genotypes (Ravande-mamouli and Ravande-setarei, respectively) showed drought stress after 28 days (most tolerant genotypes) and recovered at the end of the stress period after irrigation. Drought stress decreased photosynthetic pigments in studied genotypes. The content of soluble sugars, proline, and total soluble protein increased under drought stress conditions and the highest amount was observed in G3 genotype 30.8 mg g-1 DW, 30.5 μg g-1 DW, and 965.2 μg g-1FW, respectively. Under drought stress condition, the highest concentration of hydrogen peroxide, malondialdehyde and electrical conductivity were observed in G11, G4, and G10 genotypes respectively compared to control plants. In addition, the most enzyme activity of superoxide dismutase (85.57%), total phenol (181.09%) and total flavonoid (98.46%) was evaluated in G3, G5 and G8 respectively. Also, chlorophyll changes indicate the response of plants to environmental stresses such as drought during drought stress, the concentration of abscisic acid and ethylene increases, which stimulates the activity of the enzyme chlorophilase and causes chlorophyll degradation. The reduction of photosynthetic pigments under drought stress also seems to be related to changes in nitrogen metabolism to proline production and reduced chlorophyll synthesis because the precursor of chlorophyll and proline is glutamate. Furthermore, one of the biochemical changes that occur in plants under drought stress is the accumulation of ROS. Numerous reports have stated that drought stress increases ROS production. Drought-induced oxidative stress causes lipid peroxidation and membrane damage. It seems that in some genotypes with low levels of malondialdehyde, the membrane damage is severe and leads to more electrical conductivity. Genotypes with more electrical conductivity are more damaged by drought stress. In some genotypes, such as G2 and G11, there was a positive correlation between malondialdehyde content and electrical conductivity, but in others, such as G1, there was a negative correlation. Although the amount of malondialdehyde in this genotype is low, electrical conductivity is very high. In other words, this genotype should be a genotype sensitive to drought stress. The tolerance of the plant to various environmental stresses may be related to the level of activity of the enzymes responsible for scavenging ROS. The antioxidant response to water scarcity depends on the severity of stress and type of plant species. Therefore, different genotypes increased their antioxidant activity to reduce the effects of oxidative stress, and the high antioxidant activity was observed for G5 compared with other genotypes which can be contemplated as drought-tolerant genotype. The accumulation of compatible metabolites such as soluble sugars and proline in plants under drought conditions can help to protect them against stress. The proline and soluble sugars accumulation under stress conditions reduce lipid peroxidation and acts as a free radical scavenger. According to the results, drought stress induced accumulation of proline and soluble sugars in the genotypes of Juniperus and the highest accumulation of proline was related to G3. Therefore, this genotype can be introduced as drought-resistant genotype.
Conclusion
The results of the current study showed that drought stress significantly affected some biochemical parameters in all eleven genotypes. However, a variation in drought susceptibility was observed among genotypes. The studied genotypes in this experiment had different responses to drought stress and it seems that they utilized different mechanisms for stress tolerance. Genotype of G3 (Ravande -mamouli) was the most tolerant genotype to drought stress based on the highest levels of superoxide dismutase, soluble sugars, proline, and soluble protein. Genotype of G5 was also tolerant to drought stress with high superoxide dismutase activity and the largest amount of total flavonoid production. Therefore, increasing of compatible metabolites and antioxidant system are effective protective mechanisms against oxidative damage under drought stress.
Fatemeh Moradipour; Jamal-Ali Olfati; Yousef Hamidoghli; Atefeh Saburi; Bahman Zahedi
Abstract
Introduction: Cucumber (Cucumis sativus L.) is one of the most widely cultivated vegetables. Plant length is a quantitative trait is controlled by many genes. These traits are difficult to study due to the complex nature of their inheritance. The combining ability estimation is useful in determining ...
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Introduction: Cucumber (Cucumis sativus L.) is one of the most widely cultivated vegetables. Plant length is a quantitative trait is controlled by many genes. These traits are difficult to study due to the complex nature of their inheritance. The combining ability estimation is useful in determining the breeding value of cucumber lines by suggesting the appropriate use in a breeding program. In studying combining ability, the most commonly utilized experimental approach is the diallel design. General combining ability is a measure of additive genetic action; and specific combining ability (SCA) is deviation from additivity. General combining ability is a main effect and SCA is an interaction. The aim is to determine the breeding value of the cross. Heterosis has been utilized to exploit dominance variance through production of hybrids. There are reports on positive and negative heterosis in cucumber however, there are differences between reports. This research was conducted to estimate general and specific combining ability and heterosis in cucumber inbred lines and hybrids to produce hybrids with high yield and quality.
Material and Methods: In the spring of 2014, the seven parental lines and their 21 F1 hybrid were planted at the University of Guilan, in loamy sand field. Three replications were arranged in a randomized complete block design. The sandy loam soil was prepared by plowing and disking and formed into raised beds by plowed and harrow prior to plant establishment. Rows were on 1 m centers and plants were about 25 cm apart in the row. Prior to planting 150 kg·ha-1 of nitrogen from urea and 100 kg·ha-1 of phosphorous from triple superphosphate and 80 kg·ha-1 of potassium sulfate was applied. Side dressing with the same amount of nitrogen and phosphorus occurred at 50% flowering stage. Irrigation with 250 m3·ha-1, three times weekly, was begun at plant first flowering. In each replication, 12 individuals of each line or hybrid were spaced 25 cm within a row (plot) on 1 m centers. Data were collected from 12 plants per plot of each accession. Analyses of variance (ANOVA) of data were performed and where appropriate, ANOVA was followed by LSD mean comparison of trait values. For the combining ability analysis (GCA), measurements of plants within each plot were averaged, and means were used as experimental units for analysis by the computer program Diallel.
Results and Discussion: Genotypes has significant effect on all measured characteristics. The highest plant length was related to B6 line and the lowest plant length was related to A0×B6 and B12×B6 hybrids. The highest number of lateral branch was related to B10×A11, B12×A0 and Guilan while the lowest number was related to A0, B12×B6, A15×A11. The highest plant length to first fruit was related to A4×A11 hybrids and the lowest plant length to first fruit was related to B10, B12, B10×A15 and B12×A4. The mean square of general combining ability (GCA) were significant only for plant height up to the first fruit but the mean square of specific combining ability revealed significant differences for all traits that indicated the important effects of dominance genes in inheritance of traits. Plant height up to first fruit has further general combining which reflects the non-additive genes action. The highest parent and standard negative heterosis for plant length was related to B12×B6 hybrid. This hybrid also showed the highest negative heterosis for number of lateral branch. The highest high parent negative heterosis for plant length to first fruit was related to A11×A4 hybrid while the highest standard negative heterosis was related to A0×A4 hybrid and the highest positive heterosis for this trait was obtained from B10×B12 and B12×A4 hybrids.
Conclusion: Although heterosis is affected a plant length is the primary target for increasing yield in high density cultivation, the biological complexity of this trait makes it difficult to draw meaningful conclusions in order to track individual causal elements involved in heterosis. Cucumber breeders might develop determinate or indeterminate cultivars based on high GCA for certain traits. Cucumber breeders might develop cucumber cultivars with optimal vegetative growth based on high general combining ability for their traits. The results revealed B10 and A4 lines are proposed for hybrid production with optimum vegetative growth. The hybrid obtained by crossing of B12 and B6 are proposed for cultivation with high plant density.
