فهرست مطالب عباسعلی جنتی زاده

Damages caused by spring frosts are the most critical factor in reducing apricot production. The selection of cultivars tolerant to spring frost has been regarded as the most straightforward strategy to reduce late spring frost damages. To select frost-tolerant genotypes with suitable fruit quality, 1000 hybrids resulting from hybridization between two genotypes, Noori_Dirras×Rajabali, were evaluated for two years, 2020 and 2021, in the Agricultural Research Station of Bastam Shahroud. Phenological and pomological traits as well as spring frost tolerance were recorded naturally. Frost tolerance was determined by counting the number of healthy and damaged flowers or fruits on three random branches in each tree after the onset of frost. The last critical damaging temperatures in the first and second years occurred at -5 and -4 °C, respectively. Hybrids No. 7-74 with 60% and No. 12-64 with 41% tolerance of spring frost were identified as the most tolerant hybrids in the first and second years, respectively. Evaluation of the fruit of 51 tolerant genotypes in the second year showed that there was a great variety in the most traits among the offsprings. Ranges of 45 days to ripening, 37 g fruit weight, 13 ◦Brix total soluble solids, and 1.933 kg/cm2 fruit firmness were observed among the hybrids. A comparison of the two-year frost tolerance mean of hybrids showed that 10 hybrids, 7-74, 10-65, 11-43, 12-11, 12-31, 12-47, 12-64, 13-29 and 14-16 were superior compared to the commercial tolerant genotype (Jahangiri) and could be candidates for propagation and adaptation experiments to achieve frost-tolerant cultivar with good fruit quality.

 

Production and consumption of button mushroom is increasing in many parts of the world due to their good nutritional value and desirable medicinal properties, but because these types of mushrooms do not have a protective outer coating, they have a short shelf life, and during the postharvest, the quality of button mushrooms decreases due to water reduction, color change, texture change, reduction of taste and nutritional value, which limits its economic value, so the application of postharvest treatments can preserve the nutritional value and improve the shelf life of these mushrooms. Therefore, this study aimed to investigate the effect of postharvest treatments of melatonin and γ-aminobutyric acid (GABA) on the storage life and nutritional quality of fresh cut button mushrooms.

The postharvest treatments used in this experiment included melatonin (10 μM) and GABA (1 mM) and control (distilled water), which the mushrooms were immersed in a solution of these treatments for 5 minutes, and after drying at room temperature (24 ± 1), the mushrooms were placed in sealed containers and stored in a cold store at 4 °C with a relative humidity of 90 ± 5%. The samples were taken on days 0, 5, 10, and 15 days after treatment, and to measure browning index, hydrogen peroxide accumulation, the activity of cell membrane degrading enzymes and antioxidants enzymes were used.

The results showed that postharvest application of melatonin and GABA in fresh cut button mushrooms caused a delay in browning of slices of button mushrooms compared to control mushrooms and on the 15th day of storage, browning index in mushrooms treated with melatonin, GABA, and control was 45.78, 40.01, and 90.5%, respectively. Accumulation of hydrogen peroxide in melatonin and GABA treated mushrooms was significantly reduced compared to control mushrooms due to increased activity of the antioxidant enzymes superoxide dismutase, ascorbate peroxidase, catalase and glutathione reductase, and the highest hydrogen peroxide accumulation (51.35 μ mol g-1 FW) was obtained on the 10th day of storage in control samples. Membrane stability increased in melatonin and GABA treated mushrooms due to decreased activity of lipoxygenase and phospholipase D enzymes in these mushrooms. GABA treatment also showed better results than melatonin in most of the studied traits.

In general, according to the results of the present study, melatonin and GABA can used as an effective and safe method in maintaining nutritional quality and improving the shelf life of fresh cut button mushrooms during cold storage. Also, due to the better results provided by GABA in most of the studied traits and its cheapness compared to melatonin, it is recommended to use GABA in fresh cut mushrooms postharvest to maintain the quality of the mushrooms.

Button mushroom (Agaricus bisporus) is approved in the global food market, with regards for 30% of total mushroom production in the world, and high content of bioactive constituents including vitamins, minerals, essential amino acids as well as valuable source of polysaccharide (Meng et al., 2012). The market for sliced fresh mushrooms is increasing rapidly due to consumer demand for prepared ready-to-use vegetables and convenience foods. Button mushroom was considered as a highly perishable food due to high respiration rate, and actually no natural physical barrier on its surface to protect it, which leading to texture softening, moisture loss and browning during postharvest (Brennan et al., 2000). For sliced fresh mushrooms, the shelf life is even shorter because of the effects of the washing and cutting processes. Melatonin (N-acetly-5-methoxytryptamine) is an endogenously beneficial indole amine synthesized by all cellular organisms, which can reduce the physiological detrimental effect of abiotic stresses in plants (Zhang et al., 2018). With this regard, melatonin can play prominent roles, as a highly efficient antioxidant, scavenging molecule, and as a signaling molecule in regulating or adjusting ROS scavenging enzyme activities (Zhang et al., 2018). Recently, numerous studies reported that exogenous melatonin treatment besides storage at low temperature has been improved postharvest preservation of several fruit and vegetables (Hu et al., 2018). Since there is no information about the response of fresh-cut button mushrooms to oxidative stress following exogenous melatonin treatment during postharvest cold storage, we evaluated the effects of exogenous melatonin on qualitative attributes of fresh-cut button mushroom with regard to cap browning, weight loss, membrane permeability indicators and phenol metabolism during postharvest low temperature storage.

Button mushrooms were selected on the basis of the uniformity of maturity and size and any mechanical wounded, and were then hand sliced using a sharp knife (4 mm wide). The sliced fresh mushrooms were immersed in 0, 1, 10, 100 and 1000 µmol/L of melatonin solution for 5 minutes at 20 °C, then removed from melatonin solution and air dried at room temperature for 1 hr. After that, sliced mushrooms of each replication were packed in 500g pet plastic mushroom box (40 sliced mushrooms per box) and stored in darkness at 4 °C with 90-95% relative humidity. During storage period (5, 10 and 15 days) sliced mushroom caps per replication of each treatment were used for estimating of traits. The button mushroom weight loss was determined during storage period. To calculate the browning index (BI), photographs of edible mushroom samples were taken on sampling days and L, a and b were calculated in Photoshop software environment. Weight loss was measured according to the method of Nasiri et al (2017). A spectrophotometric procedure described by Terada et al (1978) used for the determination of ascorbic acid content. Total phenolics was measured with using the Folin–Ciocalteu reagent by Singleton and Rossi (1965) method. The texture of the mushroom cap was used to measure electrolyte leakage content and determined essentially as described by Meng et al (2012). Malondialdehyde accumulation was measured with using the thiobarbitoric acid reagent according to the method of Hodges et al (1999). DPPH radical was used to measure of scavenging activity according to the method of Dokhanieh and Aghdam (2016). The extraction and activity of PAL were determined using method described by Nguyen et al (2003). PPO was extracted with acetone according to Nguyen et al. (2003). One-way analysis of variance and Duncan’s multiple range test at P<0.05 were used for multiple mean comparisons with SAS software.

Our results showed that weight loss and cap browning index of fresh cut mushrooms following exogenous melatonin treatment (10 µM), was significantly declined to lower amount than the control during cold storage at 4 °C for 15 days. According to our results, exogenous melatonin treatment significantly slowed process of senescence in strawberry fruit as exhibited by reduced weight loss and cap browning softening of during storage (Liu et al., 2018). At the end of storage, application of endogenous melatonin at 100 µmol/L led to an increase in total phenol and ascorbic acid in fresh cut button mushrooms. Similar enhancements in total phenol and ascorbic acid along with quality retention have also been reported in exogenous melatonin treated of peach and strawberry fruit during storage time (GAO et al., 2016; Aghdam & Fard, 2017). In this study, exogenous melatonin treatment obviously declined the increasing rate of electrolyte leakage rate as well as MDA contents compared to the control, demonstrating that the effect of melatonin in reduction of membrane oxidative damage might lead to slow down browning and senescence in fresh cut mushrooms. In agreement with this suggestion, suppression of oxidative stress due to retarded senescence and quality deterioration has been described in melatonin treated cassava root and strawberry and pomegranate fruit (Ma et al., 2106; Liu et al., 2018). DPPH scavenging capacity of melatonin treated fresh cut mushrooms steadily remained higher than the control during cold storage. Higher phenylpropanoid pathway activity in response to exogenous melatonin treatment during storage, might lead to accumulation of phenolic compounds which in result provided free radical scavenging capacity up-regulation (Zheng et al., 2019). As shown in this study, higher PAL and lower PPO enzymes activity in fresh cut mushrooms followed by exogenous melatonin treatment, may be associated with molecular signaling of H2O2 pool due to enhanced NADPH oxidase enzyme activity, result in triggering phenylpropanoid pathway might lead to higher total phenol content and higher total antioxidant scavenging activity, as well membrane lipids protection from peroxidation which indicated by enhanced PAL/PPO enzymes activity accompanying with lowering cap browning (Rastegar et al., 2020).

In summary, results of this study revealed the functional effects of postharvest exogenous melatonin application at 10 µM in preserving fresh cut mushrooms quality by retarding senescence process in A.bisporus as demonstrated by attenuating weight loss and cap browning during cold storage at 4 °C for 15 days. Bioactive constituents such as ascorbic acid and total phenolics notably enhanced in response to exogenous melatonin, which is accompanied with higher PAL and lower PPO activities in melatonin treated fresh cut mushrooms during storage time. Melatonin application maintained cell membrane stability as exhibited by lowering electrolyte leakage, MDA values as well as enhancing total antioxidant activity. In general, our result showed exogenous melatonin treatment can be used as a safe and beneficial method to maintain button mushrooms quality, reduce the cap browning and prolong postharvest life the mushrooms.

Almond is one of the most important species of the genus Prunus, and most of its cultivars are self-incompatible and some are cros-incompatible. For pollination, fertilization and fruit production the self-incompatible cultivars require compatible pollen grains from other cultivars. In this regard, the compatibility of Shahroud 12 cultivar with pollen of MSK81, MSK82, MSK83, MSK84 genotypes of Shahroud 14, Shahroud 12 (self-opening) was studied and free pollination in garden conditions was performed during 1397-1396. The results showed that pollen grains of Shahroud 14 cultivars and MSK81 genotype had the highest compatibility with Shahroud 12 cultivar so that the highest percentage of fruit formation (14.39) was obtained in the cross pollination of Shahroud 12 and Shahroud 14 and then in the cross pollination of Shahroud 12 with MSK81 with 9.80%. Pollination of Shahroud 12 cultivar with native pollen (self-pollination) led to no fruit formation (zero percent) in this cultivar. According to the results of this study, it was found that pollen grain type has a significant effect on the evaluated traits of fruit such as length, width and dry weight of fruit and kernel, hard shell weight and kernel percentage. Shahroud 12 cultivar is self-incompatible and Shahroud 14 cultivar and MSK81 genotype can be used as suitable pollinators for Shahroud 12 cultivar in the climatic conditions of the western region of the country.

Low temperature storage is widely used as a postharvest treatment to delay senescence in vegetables and ornamentals, and ripening in fruits, and thereby maintaining their postharvest quality. However, tropical and subtropical crops such as Anthurium flowers are sensitive to chilling injury, a physiopathy affecting these crops when subjected to temperatures below 12 °C but above the freezing point. The recommended optimum temperature for storage of anthurium cut flowers is 12.5–20 ◦C. The main symptom of chilling injury in anthurium flowers under low temperature storage is spadix wilting and spathe browning. The main symptom of chilling injury in anthurium flowers under low temperature storage is spadix wilting and spathe browning. In this experiment, the impact of 0, 1, 2 and 4 mM salicylic acid (SA) treatment applied by postharvest stem-end dipping (15 min at 20 ˚C) on GABA shunt pathway activity of anthurium cut flowers (cv. Sirion) storage at 4 ˚C for 21 days were investigated. SA treatment at 2 mM delayed spathe browning and retards electrolyte leakage and malondialdehyde (MDA) increase. The anthurium cut flowers in response to 2 mM SA treatment displayed significantly higher GABA transaminase (GABA-T) activity during storage at 4 ˚C for 21 days, which coincided with lower GABA content, leading to flowers with lower spathe browning. SA treatment enhanced GABA shunt pathway activity, by enhancing GABA-T activity, during storage at 4 ˚C, lead to consumption of GABA for providing higher ATP content associated with lower H2O2 content.These findings showed that SA treatment at 2 mM can be applied as an effective procedure for improving anthurium cut flowers tolerance to postharvest chilling stress. Anthurium flowers are sensitive to chilling injury, a physiopathy affecting these crops when subjected to temperatures below 12 °C but above the freezing point. The recommended optimum temperature for storage of anthurium cut flowers is 12.5–20 ◦C. The main symptom of chilling injury in anthurium flowers under low temperature storage is spadix wilting and spathe browning. Anthurium flowers are sensitive to chilling injury, a physiopathy affecting these crops when subjected to temperatures below 12 °C but above the freezing point. The recommended optimum temperature for storage of anthurium cut flowers is 12.5–20 ◦C. The main symptom of chilling injury in anthurium flowers under low temperature storage is spadix wilting and spathe browning.These findings showed that SA treatment at 2 mM can be applied as an effective procedure for improving anthurium cut flowers tolerance to postharvest chilling stress. These findings showed that SA treatment at 2 mM can be applied as an effective procedure for improving anthurium cut flowers tolerance to postharvest chilling stress.

Late spring frost damage is the main factor that limits apricot production in Iran. This research was aimed to evaluate the damage of freezing in two apricot cultivar flowers: ʽʽNasiriʼʼ and ʽʽNori-Dirrasʼʼ during spring 2011. Reproductive organs of these cultivars at two phenological stages، popcorn and full bloom، were transferred to programmable freezer with temperature touch down from 5°C to -10°C. Temperature were detected by the mean of thermocouple and recorded by a data logger connected to a PC Computer. According to the results، differences between two cultivars and interaction of cultivar and phenological stages were not significant، whereas the effect of phenological stage was significant. The lowest supercooling temperature was -6. 1°C and recorded at full bloom stage in ʽʽNori-Dirrasʼʼ. More than 30% of ʽʽNori-Dirrasʼʼ buds and more than 60% of its flowers showed less supercooling than -5°C. According to this result، ʽʽNori-Dirrasʼʼ showed lower supercooling temperature than ʽʽNasiriʼʼ.

Iran, with a long history of apricot cultivation is one of the most important apricot producers in the world. Centuries of sexual reproduction via seed, have developed many divergent variations of apricots in Iran. However, unfortunately there is no comprehensive report available concerning its diversity and genetic make-up. In this study, 39 Iranian apricot cultivars as well as accessions, native to Iran, were evaluated using morphological and RAPD molecular markers. Total Soluble Solids (TSS), Titrable Acidity (TA), kernel weight, fruit flesh weight as well as fruit weight exhibited high diversity coefficients, making it possible to select for desirable characters in breeding programs. In addition, factor analysis was performed to determine the number of the main factors. A 79.52% level of total variance was explained by the first six factors for morphological discrimination, the first independent factors of which included fruit size (24%), pit (16%) and flavor (14.5%). Cluster analysis of morphological traits led to a separation of cultivars according to their fruit size, ripening season as well as characteristics related to fruit taste. According to the RAPD, the highest genetic similarity was observed between ‘Noori-Dirras’ and ‘Noori-Pishras’ (0.95) while the lowest between ‘Tanasgol’ and ‘Shahrood-48’ (0.3). In the cluster analysis, at similarity distance of 65%, cultivars were placed in six main groups, in agreement with some other results obtained from morphological analysis and from the geographical origins of accessions.