مجله علوم و فنون باغبانی ایران
سال بیست و دوم شماره 4 (زمستان 1400)

An experiment was conducted to examine whether the foliar application of melatonin (MA) and nitric oxide (NO) would improve thermo-tolerance of strawberry plants subjected to high-temperature stress. For this purpose, a factorial experiment in a completely randomized design with three replications, in the college of Agriculture, Isfahan University of Technology was performed. The strawberry plants cv. Kurdistan were exposed to various temperatures (25, 35, and 40 °Ϲ) for 24 hours after pre-treatment with 0, 50, and 100 μM MA and NO. Heat stress significantly induced hydrogen peroxide and malondialdehyde content and increased proline accumulation, whereas reduced relative water content (RWC) and the maximal efficiency of PSII photochemistry (Fv/Fm). In addition, heat stress increased glutathione and ascorbic acid contents and enhanced superoxide dismutase and guaiacol peroxidase activities, and reduced catalase and ascorbate peroxidase activities. Treatment with MA and NO decreased heat injury symptoms and induced antioxidant enzyme systems and increased non-enzymatic antioxidant contents. Melatonin and NO increased proline content, RWC, and improved Fv/Fm compared with the non-treated plants. These results suggested that in strawberry, MA and NO alleviate heat-induced oxidative damage by modulating antioxidant pathways, decreasing reactive oxygen species, and inhibiting lipid peroxidation.

Extensive attempts have been made to clarify the molecular basis of fruit ripening mechanisms in recent decades. Regarding the effect of molecular and genetic processes in regulating fruit ripening, a comprehensive understanding of the ripening genetic network which is involved in fruit quality, ripening time, and shelf life of fruits is necessary. Due to the nutritional and medicinal value of lemon, microarray data of fruit juice vesicle tissue at two developmental stages (immature and mature) was analyzed in the present study. We aimed to identify genes and pathways related to ripening through bioinformatics tools, including Bioconductor Limma, DAVID, String, and iTAK. According to the results, 4,255 probes showed differential expression between the mature and immature stages. Based on the analysis, carotenoid biosynthesis was identified as one of the KEGG-enriched pathways. Considering the upregulated genes in the carotenoid biosynthesis pathway during maturation and its role in abscisic acid (ABA) biosynthesis, it can be stated that ABA signaling might play a vital role in the maturation of lemon fruit. Besides, enhanced expression of ethylene biosynthesis genes during the ripening stage might confirm the role of ethylene and its signal transduction in the ripening of this fruit. Based on the results of this study, the gene encoding 1-aminocyclopropane-1-carboxylate oxidase 1 enzyme showed the highest expression fold change (13.05 times) in the mature compared to immature  lemon. A survey for the determination of upregulated transcription factors, resulted in the identification of 41 transcription factors. Also, upregulated genes network analysis led to the identification of 10 genes, such as the HY5-like transcription factor involved in the maturation process. Manipulation of these identified genes is introduced as one of the approaches to improve secondary metabolites, and change ripening time in lemon fruit which can lead to developing cultivars with favorable ripening time that can be grown in various areas.

To investigate the effects of Zinc-salicylic acid nano-complex and storage time on horticultural and phytochemical properties of Thymus daenensis Celak, a factorial experiment was conducted based on a randomized complete block design. Foliar spraying was done in two stages 15 days after establishment, at levels of zero, 0.1, 0.3 and 0.5% by volume. After harvesting and storage during periods of 0, 2, 4 and 6 months at room temperature, quantitative and qualitative changes in essential oil, phenolic compounds content and antioxidant activity of shoots were studied. Based on the foliar application of zinc-salicylic acid nanocomplex by 0.3%, it increased plant height, fresh weight, dry weight, flower height, leaf length, leaf width and wet to dry weight ratio, respectively, compared to the control without foliar application by 32.5, 26.7, 19.2, 38.3, 22.2 and 27.08%, respectively. Storage time had no significant effect on the percentage of essential oil. Concentration of 0.3% nanocomplex increased the essential oil by 0.822% compared to the control. The effect of interaction between nanocomplex concentration and storage time on the percentage of essential oil was not significant. The predominant compounds were essential oil, Carvacrol, Thymol, p-Cymene and Borneol. The highest antioxidant activity of plant extract was related to the interaction of foliar application of zinc-salicylic acid nanocomplex with a concentration of 0.1% and storage for 60 days. Treatment with zinc-salicylic acid nanocomplex (at a concentration of 0.3%) improved vegetative characteristics and storage time and increased the percentage of essential oil.

In order to investigate the effects of postharvest application of hydrogen sulfide (H2S) on physicochemical attributes of cornelian cherry fruit, a factorial experiment was performed based on completely randomized design with three replications (each replication including 60 fruits). Treatments included NaHS (0, 0.6, 1.2, and 1.8 mmol) and different storage times (7, 14, and 21 days). The fruits were placed in the refrigerator (at 2°C and relative humidity of 85%) immediately after treatment. Physical and biochemical variables were measured within an interval of seven days. According to the results, the maximum amount of anthocyanin (2.27 mg/g FW) and ascorbic acid (26.8 mg/100g FW) and the minimum amount of H2O2 (0.41 µm/100g FW) were obtained by 0.6 mmol of H2S. Also, H2S (1.2 mmol) was more effective in terms of maintaining the total phenol (414.13 mg GA/100g FW). Weight loss with H2S 1.8 mmol was significantly less than other treatments and accompanied with the highest amount of flavonoids (27. 9 mg QUE/100g FW) and proline (0.24 mg/ml). Fruits treated with H2S were able to maintain better physical and biochemical attributes in comparison with control fruits. Referring to the important of cornelian cherry storing at cold storage conditions in terms of maintenance of the firmness, appearance quality and long shelf life with low frost damage, H2S 0.6 mmol should consider as the favorite treatment level.

The aim of the present study was to determine the effects of 24 h pulls treatment of thidiazuron (TDZ at 0, 8, and 16 µM) and foliar application of chitosan (CS at 0, 250, and 500 mg/L) on the postharvest quality of Strelitzia reginae cut leaves. In the last week of the experiment, 8 µM TDZ and the control treatment showed the lowest (22.11 g) and the highest (28.98 g) leaf fresh weight loss, respectively. The highest (7.75 ml) and the lowest (4 ml) solution uptake was obtained by using 8 µM TDZ and 500 mg/L CS, respectively. The maximum (27.51 and 2.52) and the minimum (12.58 and 0.30) values of SPAD index and performance index (PI) were observed in 8 µM TDZ and control treatments, respectively. The highest (0.46) and the lowest (0.12) values of Fv/Fm were obtained by using 8 µM TDZ and 500 mg/L CS, respectively. Application of 16 µM TDZ + 500 mg/L CS exhibited the best color indices (L, a, b, and chroma). Using 16 µM TDZ, the lowest vase life (12.87 days) was obtained. The maximum vase life (21 days) was obtained in the leaves treated by 8 µM TDZ or 16 µM TDZ + 500 mg/L CS, which were the best treatments in the present study.

Mango is one of the most important fruits in Asia and the tropical and subtropical regions of the world. In this study, the intraspecific genetic variation of 30 mango genotypes (Mangifera indica L.) from some regions (Roudan, Manoojan, Faryab, Jiroft, Anbarabad, Hishin, Dehkahan and Boluk) in two southern provinces of Kerman and Hormozgan was investigated by evaluating the trnH-psbA intergenic region. After sampling the young leaves, DNA extraction was done by using dellaporta method and PCR was conducted using trnH-psbA (IGS) primers. Proliferated products of each genotype were recorded in the NCBI database after sequencing. Analysis and drawing phylogenic relationships dendrogram and sequence similarity matrix was done by using Darwin, Popgene and Mega softwares to determine genetic relationships and genetic distances between genotypes. Sequence analysis showed that in the trnH-psbA intergenic region, 361 positions were identified. Studying the sequence homology of all mango samples represented a common sequence of 116 base pairs among them. Based on the dendrogram resulted from cluster analysis, all genotypes classified in 4 groups. Based on the results, it can be concluded that the use of the trnH-psbA intergenic region was useful for studying and identifying the diversity and interrelationships of mango genotypes.

Gray mold is one of the most important pathogens of cherry fruit. In the present study, the ability of bioinhibition of Botrytis cinerea by antagonist bacteria and the effects of adding marjoram essential oil  on the growth of pathogenic fungi was evaluated. According to the results, with increasing in the concentration of essential oil, the growth rate of fungi decreased. In vivo, cherry fruits were infected with a suspension of 105 hg/ml of pathogenic fungus, then separately treated with a suspension of 108 cells/ml of selected strains of antagonist bacteria and marjoram essential oil at 5 levels. The qualitative parameters were examined at three times of zero, 15 and 30 days. The results showed that the treatment of Bacillus bacterium and marjoram essential oil at a concentration of 750 μl/l were the most effective treatment to increase the level of antioxidant activity and phenylalanine-ammonialyase enzyme activity. Total phenol content and anthocyanin content at the concentration of 1000 μl/l  were the highest after 30 days. The highest amount of polyphenol oxidase enzyme was recorded after 15 days at the concentration of 750 μl/l. According to the results of this study, the mechanism of B. subtilis and marjoram essential oil in the control of gray mold of cherries is probably due to the induction of resistance in cherry fruit and increased antioxidant activity.

The effects of postharvest dip treatment in hot water and carbendazim fungicide on sensory, physicochemical, and antioxidant characteristics determining the internal and external quality of sweet lime (Citrus limettioides Tan.) fruit were studied. Treatments included a 4 min dip in 45 °C hot water, 0.5 g L-1 carbendazim solution and distilled water (control). Fruits were stored at 10 °C and 85% relative humidity for 90 days, with characteristics being measured at 30-day intervals. Compared to control fruits, treated fruits by hot water had lower weight loss and decay, better taste index, and higher content of total phenol in peel and ascorbic acid in the juice. After one month of the storage, they showed higher levels of enzymatic antioxidant activity (superoxide dismutase, catalase, ascorbate peroxidase, and guaiacol peroxidase) and more non-enzymatic antioxidants such as total phenol in peel and ascorbic acid in juice when compared to control. Afterwards, peel enzymatic antioxidant activity increased in control fruits while decreasing in hot water-treated fruits. Based on non-enzymatic antioxidants content and sensory evaluation after 3-months storage, hot water-treated fruits possessed the best internal and external quality, while fungicide-treated fruits with a pale appearance had the lowest quality in peel color and firmness. At this time, investigations on the peel content of hydrogen peroxide and enzymatic antioxidant activity revealed that fungicide-treated fruits experienced more stress and oxidative injury than control fruits. As a result, hot water dip treatment was recognized as a safe treatment for improving and extending the storability of sweet lime, as well as a suitable substitute for chemical fungicides.

To investigating the effects of various concentrations of nitrogen (180, 230, 280 and 330 mg L-1) and potting media composition (peat moss:perlite or cocopeat:perlite as 2:1 V/V) on some growth traits of Euphorbia pulcherrima,  a factorial experiment was conducted based on a completely randomized design with 8 treatments and 3 replications. The results showed that the highest height, plant canopy diameter and protein content eamed by using of were observed in plants grown at the concentration of 230 mg L-1 N in cocopeat and perlite media. The concentration of 230 mg L-1 N increased the bract and leaf area in comparison with the other treatments. The concentration of 280 mg L-1 of nitrogen with cocopeat and perlite media caused the maximum amount of the Mg content in plant leaves tissue. Using of peat mass and perlite and 330 mg L-1 of nitrogen resulted in the highest bract anthocyanin and potassium content. Generally, the results of the study showed that the concentrations of 230 and 280 mg L-1 nitrogen and the combination of cocopeat and perlite as a media improved the growth indices and qualitative characteristics of Poinsettia.

In this study, a pot experiment was conducted in the greenhouse conditions to investigate the drought tolerance of six Iranian grape cultivars. The experiment was factorial, based on a completely randomized design, with two factors including cultivars (‘Rotabi’, ‘Rashe’, ‘Chafte’, ‘Bidaneh Sefid’, ‘Khalili’, and ‘Laal’) and moisture treatments (40 % and 80 % of soil available water). Under drought stress, the lowest accumulation of soluble carbohydrates and proline (50.36 and 4.25 mg g-1 FW, respectively) and the highest stress susceptibility index (2.47, on average) and growth reduction were observed in ‘Bidaneh Sefid’ cultivar. ‘Chafte’ showed a considerable growth in optimal moisture condition; moreover, this cultivar had a relatively low stress susceptibility index (0.60, on average), designated as the most tolerant cultivar to drought stress. ‘Khalili’ had the highest root weight and root volume under optimal conditions. Although this cultivar had the highest stress susceptibility index in terms of root dry weight (1.24) and root volume (1.35) after ‘Bidaneh Sefid’, but under stress conditions it had a suitable root weight, root volume and number of roots. ‘Rotabi’ and ‘Laal’ had relatively less growth under optimal moisture conditions; however, they showed a subtle growth reduction under drought stress. These results indicate that in order to introduce drought tolerant plants, stress susceptibility index and vegetative growth rate under water shortage should be considered together.

Micropropagation is a method for mass and rapid proliferation of plants on tissue culture media. Low survival and poor growth of micropropagated seedling after transplanting is one of the main disadvantages of this technique in many plants. The success of this method can be increased by using biological agents such as arbuscular mycorrhizal fungi. The experiment was conducted to evaluate the efficiency of arbuscular mycorrhizal fungi to improve physiological indices and osmotic regulators content of micropropagated pear rootstock (Pyrodwarf) under drought stress. Factorial experiment was performed in a completely randomized design with two factors (two mycorrhizal and three drought stress level). Experiment was conducted in three replications under greenhouse conditions. Drought stress continued for two months. Results of analysis of variance showed that mycorrhizal symbiosis significantly increased physiological parameters and decreased osmotic regulators at all levels of drought stress. Mycorrhizal colonization percentage determined as 84, 81.66 and 72%, in low, medium and severe drought stresses levels, respectively. Mycorrhizal application significantly increased physiological indices such as Fv/Fm, photosynthetic efficiency index, SPAD index, and the content of chlorophyll b, cartenoid and total chlorophyll in mycorrhizal treatments compared to control (no mycorrhizal plants) and decreased proline and soluble sugars content. Overall, the results of this experiment showed that rootstocks obtained from tissue culture treated with arbuscular mycorrhizal fungi were more adapted to natural conditions and drought stress.