Meta-analysis of RNA-Seq studies reveals genes with dominant functions during flower bud endo- to eco-dormancy transition in Prunus species.

In deciduous fruit trees, entrance into dormancy occurs in later summer/fall, concomitantly with the shortening of day length and decrease in temperature. Dormancy can be divided into endodormancy, ecodormancy and paradormancy. In Prunus species flower buds, entrance into the dormant stage occurs when the apical meristem is partially differentiated; during dormancy, flower verticils continue their growth and differentiation. Each species and/or cultivar requires exposure to low winter temperature followed by warm temperatures, quantified as chilling and heat requirements, to remove the physiological blocks that inhibit budburst. A comprehensive meta-analysis of transcriptomic studies on flower buds of sweet cherry, apricot and peach was conducted, by investigating the gene expression profiles during bud endo- to ecodormancy transition in genotypes differing in chilling requirements. Conserved and distinctive expression patterns were observed, allowing the identification of gene specifically associated with endodormancy or ecodormancy. In addition to the MADS-box transcription factor family, hormone-related genes, chromatin modifiers, macro- and micro-gametogenesis related genes and environmental integrators, were identified as novel biomarker candidates for flower bud development during winter in stone fruits. In parallel, flower bud differentiation processes were associated to dormancy progression and termination and to environmental factors triggering dormancy phase-specific gene expression.

Changes of bioactive components and antioxidant potential during fruit development of Prunus humilis Bunge.

Dynamic changes in flavonoid, total phenol, and antioxidant potential in different Prunus humilis accessions during fruit development stages were studied in order to provide a reference for the optimum harvest time for flavonoid extraction. 'Nongda 4', 'Nongda 5', 'DS-1' and '02-16' were selected as plant materials to determine the content of flavonoid, total phenol and antioxidant indices during six fruit development stages. Changes in total flavonoid content (TFC) and total phenol content (TPC) in different accessions of P. humilis were slightly different depending on the development stage of P. humilis fruit. TFC and TPC in 'Nongda 5' fruit showed a trend of continuous decline. There was a small increase in TFC and TPC from the young fruit stage to the stone hardening stage, followed by a decreasing trend, and then to the lowest level at the ripening stage of 'Nongda 4', 'DS-1', and '02-16' fruits. The trend of antioxidant capacity (ABTS, FRAP, DPPH) with the TFC and TPC of P. humilis fruit was basically the same, and the correlation analysis results showed that the TFC of P. humilis fruit was positively correlated with the antioxidant indices (P<0.01). Catechin (CC), rutin (RT), and quercetin-7-O-ß-D-glucopyranoside (Q7G) were detected in all the fruit development stages of the four P. humilis fruits. Among them, catechin was the most abundant component, accounting for approximately 10%. Myricetin (MC) and quercetin (QC) were generally detected only in the early fruit development stage, but not in the later fruit development stage. Correlation analysis showed that the flavonoid components with TFC, TPC, and antioxidant indices differed between the different accessions. RT, CC, and liquiritigenin (LR) had a stronger correlation with TFC and antioxidant indices. Cyanidin-3-O-glucoside (C3G) was not detected until the coloring stage in two red P. humilis accessions ('Nongda 4' and 'DS-1'), and so it is better to choose a red P. humilis fruit to extract C3G at the ripening stage. Selecting an early stage of fruit development, especially the stone hardening stage, was important for extracting flavonoids, total phenols and other components. We believe that our results will provide basic information and reference for evaluation of fruit nutrition and health benefits, breeding of functional new varieties, and efficient utilization of P. humilis fruit.

Changes of pollen viability of ornamental plants after long-term preservation in a cryopreservation pollen bank.

This study determined the changes in pollen viability of 102 species/cultivars of ornamental plants (affiliated to 32 genera of 14 families) following long-term liquid nitrogen storage in a cryopreservation pollen bank. The goal was to provide information on the safety and stability of pollen cryopreservation technology. Fresh pollen at the time of storage was used as the control, and the study examined the pollen viability of ornamental plants cryopreserved for 8, 9, or 10 years. The results show that pollen of the 102 species/cultivars in the cryopreservation pollen bank retained viability ranging from 1% to 58%, After long-term storage there were changes in viability: 11.76% (12 species/cultivars) had increased viability, 16.67% (17 species/cultivars) had stable viability, and the viability of 71.57% (73 species/cultivars) showed a decreasing trend.

1-Methylcyclopropene Treatment on Phenolics and the Antioxidant System in Postharvest Peach Combined with the Liquid Chromatography/Mass Spectrometry Technique.

In the present study, the potential effect of 1-methylcyclopropene (1-MCP) treatment on phenolics and antioxidant capacity in postharvest peach was assessed. Peach fruit (cv. Xiahui-8) treated with 1-MCP or without treatment was stored in 25 °C for 2, 4, 6, and 8 days. The phenolic composition and change trend were evaluated by liquid chromatography/mass spectrometry. The reactive oxygen species production and scavenging capacity against DPPH, O2• -, and HO• were determined. Gene expression of enzymes in the flavonoid biosynthetic pathway was assayed by quantitative reverse transcription polymerase chain reaction analysis. 1-MCP application inhibited the ethylene and CO2 production and stimulated the total phenol and total flavonoid contents. Total anthocyanin formation may be influenced directly or indirectly by the level of ethylene. The scavenging capacities of DPPH, HO•, and O2• - after 1-MCP treatment were enhanced. 1-MCP treatment affected the tissue color change, stimulated gene expression of PpaPAL, PpaCHS, PpaF3H, and PpaUFGT, and promoted the biosynthesis of flavonoids and stability of anthocyanin. PpaDFR and PpaUFGT played crucial roles in rapid color change stages. Kaempferol and kaempferol 3- O-galactoside increased distinctively during storage time.

Heat treatment as postharvest tool for improving quality in extra-early nectarines.

BACKGROUND: Extra-early nectarine cultivars such as 'VioWhite 5' could present a lack of organoleptic and nutritional quality. Heat treatments (HT) can be applied to improve their primary characteristics. In this experiment, control (non-treated), HT1 (3 h; 45 °C) and HT2 (2 h; 50 °C) were studied. Fruit were stored (10 days; 0 ± 0.5 °C; 90-95% RH) followed by a simulated retail sale period (3 days; 15 °C; 70-75% RH). RESULTS: HT fruit showed higher weight loss (2.76 ± 0.06% and 3.32 ± 0.01% for HT1 and HT2 , respectively; vs. 2.23 ± 0.14% for control) and lower firmness than control samples (28.88% and 21.67% less for HT1 and HT2 , respectively). HT treatments induced an increase in soluble solids content and a decrease in total acidity, which led to a better sensory quality. These changes were positively received by consumers. Total antioxidant capacity was enhanced by HT due to an increase in phenolic compound content. A higher enzymatic activity was found in pectin methylesterase and polygaracturonase in HT nectarines when compared to control. CONCLUSION: The application of HT on extra-early nectarine cv. demonstrated a strong potential to improve consumption quality in the industry. © 2017 Society of Chemical Industry.

Thinned stone fruits are a source of polyphenols and antioxidant compounds.

BACKGROUND: Thinned fruits are agricultural by-products that contain large quantities of interesting compounds due to their early maturity stage. In this work, the phenolic profile and the antioxidant activity of six thinned stone fruits (apricot, cherry, flat peach, peach, plum and nectarine) have been investigated, focussing on proanthocyanidins. RESULTS: Thinned nectarine had the highest content of total phenols [67.43 mg gallic acid equivalents (GAE) g-1 dry weight (DW)] and total flavonoids (56.97 mg CE g-1 DW) as well as the highest antioxidant activity measured by DPPH scavenging (133.30 mg [Trolox equivalents (TE) g-1 DW] and FRAP assay (30.42 mg TE g-1 DW). Proanthocyanidins were very abundant in these by-products, and the main phenolic group quantified in cherry (10.54 mg g-1 DW), flat peach (33.47 mg g-1 DW) and nectarine (59.89 mg g-1 DW), while hydroxycinnamic acids predominate in apricot, peach and plum (6.67, 22.04 and 23.75 mg g-1 DW, respectively). The low, mean degree of polymerisation of proanthocyanidins suggests that their bioavailability could be very high. CONCLUSIONS: This study shows that thinned stone fruit extracts might be used as antioxidants in foods or as a source of compounds with health-related benefits that can be used in the pharmaceutical, cosmetic and food industries. © 2016 Society of Chemical Industry.

Antioxidant activity of selected wild Canadian prairie fruits.

BACKGROUND: Canadian prairies are a habitat for unique wild plants. The main object of the present study was to investigate phytochemicals content and antioxidant activity in seven wild Canadian prairie fruits. METHODS: The presence of total phenolics, flavonoids, anthocyanins and antioxidant activity were identified in the extracts according to standard procedure. RESULTS: Wild rose had the highest amounts of total phenolics and total flavonoids, whereas elderberry exhibited the highest amount of anthocyanins. All extracts showed good scavenging activities towards DPPH radicals. The results showed a good linear relationship between oxygen radical absorbance capacity and total phenolics indicating that radicals are scavenged at a greater rate as the total phenolics content increases. Additionally, all extracts when applied at concentration of 800 ppm, showed ability to inhibit oxidation of canola oil. In SOT test the best results were obtained when extract of American mountain ash was used. In general, wild rose followed by American mountain ash demonstrated the highest antioxidant activity among assessed Canadian prairie fruits. CONCLUSIONS: From the results it can be concluded that prairie fruit extracts are a rich source of phenolic compounds and poses a high antioxidant activity, confirmed by assessment with different type of radicals employed.

Physicochemical characterisation of four cherry species (Prunus spp.) grown in China.

The physicochemical characteristics of four cherry species (Prunus avium, Prunus cerasus, Prunus pseudocerasus and Prunus tomentosa) were evaluated. Inter-species variability was greater than intra-species differences. Glucose and fructose were the main sugars, and malic acid was the main organic acid in all species. Combining HPLC-DAD and LC-ESI-MS/MS technologies, total 25 phenolic components were preliminarily identified. P. avium was characterised by high fruit weight, edible proportion, sugar content and low acid content, which made it suitable for fresh eating. P. cerasus was high in acid content and anthocyanins content, making it a good processing species. P. pseudocerasus had rich flavonols varieties and high proportion of hydrocinnamic acids. P. tomentosa was characterised by high total phenolics content (especially flavonols and tannins) and antioxidant activity, indicating a great developmental potential as a health fruit. The results of the present study might provide theoretical guidance for the further development and utilisation of cherries.

Preharvest application of oxalic acid increased fruit size, bioactive compounds, and antioxidant capacity in sweet cherry cultivars (Prunus avium L.).

Trees of 'Sweet Heart' and 'Sweet Late' sweet cherry cultivars (Prunus avium L.) were treated with oxalic acid (OA) at 0.5, 1.0, and 2.0 mM at 98, 112, and 126 days after full blossom. Results showed that all treatments increased fruit size at harvest, manifested by higher fruit volume and weight in cherries from treated trees than from controls, the higher effect being found with 2.0 mM OA (18 and 30% higher weight for 'Sweet Heart' and 'Sweet Late', respectively). Other quality parameters, such as color and firmness, were also increased by OA treatments, although no significant differences were found in total soluble solids or total acidity, showing that OA treatments did not affect the on-tree ripening process of sweet cherry. However, the increases in total anthocyanins, total phenolics, and antioxidant activity associated with the ripening process were higher in treated than in control cherries, leading to fruit with high bioactive compounds and antioxidant potential at commercial harvest (≅45% more anthocyanins and ≅20% more total phenolics). In addition, individual anthocyanins, flavonols, and chlorogenic acid derivatives were also increased by OA treatment. Thus, OA preharvest treatments could be an efficient and natural way to increase the quality and functional properties of sweet cherries.

Effects of storage temperature, storage duration, and subsequent ripening on the physicochemical characteristics, volatile compounds, and phytochemicals of Western Red nectarine (Prunus persica L. Batsch).

Western Red nectarines, harvested at commercial maturity, were stored for up to 20 days at 1, 4, or 8 °C and then transferred to 25 °C for 0 or 4 days. The main physicochemical attributes, phytochemicals, and volatile compounds were then determined. During storage and ripening, firmness, titratable acidity, organic acids, and C6 volatile compounds decreased, whereas ethylene production, lactones, and C13 norisoprenoids greatly increased. Soluble solids content, sugars, and polyphenols remained quite constant during both stages. During storage, vitamin C decreased and carotenoids did not significantly change, whereas both greatly increased during ripening. Increased time of low-temperature storage has been found to decrease lactones and C13 norisoprenoids in nectarine and, consequently, to limit its aroma during maturation. Finally, Western Red nectarine was found hardly chilling injury sensitive, and trends for sugars, polyphenols and lactones observed in this study were contrary to those generally reported in the literature for chilling-injured fruit.

Fruit cuticle composition of a melting and a nonmelting peach cultivar.

Although postharvest quality of fruit is greatly affected by cuticle composition, structure, and properties, very few published studies have analyzed fruit cuticle composition from a postharvest perspective. In this work, the chemical composition of waxes and cutin, major cuticular components, was analyzed in fruit cuticle samples isolated from a melting ('October Sun') and a nonmelting ('Jesca') peach (Prunus persica L. Batsch.) cultivar at harvest and after a simulated shelf-life period of 5 days at 20 °C. Cutin composition was dominated by 18-hydroxyoleic acid, whereas the triterpenoid ursolic and oleanoic acids and the alkanes n-tricosane and n-pentacosane were quantitatively prominent among the wax compounds identified. Some quantitative differences were found between both cultivars for particular compound families and in their postharvest modifications. To the best of the authors' knowledge, this is the first study characterizing the composition of the cuticle of peach fruit and describing the changes therein after harvest.

[Procedure of seed quality testing and seed grading standard of Prunus humilis].

So far there exists no corresponding quality test procedures and grading standards for the seed of Prunus humilis, which is one of the important source of base of semen pruni. Therefor we set up test procedures that are adapt to characteristics of the P. humilis seed through the study of the test of sampling, seed purity, thousand-grain weight, seed moisture, seed viability and germination percentage. 50 cases of seed specimens of P. humilis tested. The related data were analyzed by cluster analysis. Through this research, the seed quality test procedure was developed, and the seed quality grading standard was formulated. The seed quality of each grade should meet the following requirements: for first grade seeds, germination percentage ≥ 68%, thousand-grain weight 383 g, purity ≥ 93%, seed moisture ≤ 5%; for second grade seeds, germination percentage ≥ 26%, thousand-grain weight ≥ 266 g, purity ≥ 73%, seed moisture ≤9%; for third grade seeds, germination percentage ≥ 10%, purity ≥ 50%, thousand-grain weight ≥ 08 g, seed moisture ≤ 13%.

Characterization and the effect of maturity at harvest on the phenolic and carotenoid content of Northeast USA Apricot (Prunus armeniaca) varieties.

The phenolic and carotenoid content and quality indices of five Northeast apricot varieties were assessed over two years and the impact of maturity at harvest was evaluated. Four varieties were analyzed at commercial and tree ripe stages and one variety after storage for 4 weeks (0-1 °C, 90-95% relative humidity). Total phenolic content ranged from 44.0 to 345.1 mg/100 g, total antioxidant capacity (oxygen radical absorbance capacity assay) from 2096.9 to 7165.1 µmol/100 g, and total carotenoid content from 1312.1 to 7371.1 µg/100, fresh weight. 'Hargrand' apricot had the highest phenolic and carotenoid content. Catechin, chlorogenic acid, and neochlorogenic acid were the predominant phenolic compounds and ß-carotene was the predominant carotenoid compound. Carotenoid content increased with ripening and postharvest storage while changes in phenolic content and antioxidant capacity were variety-dependent. Results show the apricot varieties studied to be good or excellent sources of vitamin A despite moderate carotenoid content attributed to cultivation in a colder climate.

Nutritional evaluation and health promoting activities of nuts and seeds cultivated in Greece.

Available data suggest that genetic as well as environmental factors may influence nuts and seeds nutrients content. In this context nuts and seeds cultivated in Greece were studied. Macronutrients content was in agreement with that from other areas. Total phenolics content was in the range of 43.0 ± 2.1-1512.7 ± 60.7 mg GAE/100 g for chestnut and walnut, respectively. Thirteen to 22 individual phenolics were identified in the studied species. Oleanolic acid was in the range of 0.10-9.03 mg/100 g. Pumpkin seeds contained the higher squalene content (71.6 mg/100 g). ß-Sitosterol predominated in all samples except pumpkin seeds. Tocopherols ranged from 8.9 mg/100 g (chestnut) to 29.3 mg/100 g (almond). Nuts and seeds hydrophilic extracts at quantities corresponding to the estimated daily consumption by the Greeks succeeded in inhibiting LDL oxidation in vitro by increasing lag time 1.1-14.1 times. One serving of nuts or seeds may cover a significant fraction of health promoting microconstituents daily intake.

Fruit quality and bioactive compounds relevant to human health of sweet cherry (Prunus avium L.) cultivars grown in Italy.

The fruit quality characteristics, phenolic compounds and antioxidant capacities of 24 sweet cherry (Prunus avium L.) cultivars grown on the mountainsides of the Etna volcano (Sicily, Italy) were evaluated. High-performance liquid chromatographic methods were used to identify and quantify sugars, organic acids and phenolics. A total of seven phenolic compounds were characterised as hydroxycinnamic acid derivatives (neochlorogenic acid, p-coumaroylquinic acid and chlorogenic acid) and anthocyanins (cyanidin 3-glucoside, cyanidin 3-rutinoside, pelargonidin 3-rutinoside and peonidin 3-rutinoside). The total anthocyanin content ranged from 6.21 to 94.20mg cyanidin 3-glucoside equivalents/100g fresh weight (FW), while the total phenol content ranged from 84.96 to 162.21mg gallic acid equivalents/100g FW. The oxygen radical absorbance capacity (ORAC) assay indicated that fruit of all genotypes possessed considerable antioxidant activity. The high level of phenolic compounds and antioxidant capacity of some sweet cherry fruits implied that they might be sources of bioactive compounds that are relevant to human health.

Prediction of components of the sporopollenin synthesis pathway in peach by genomic and expression analyses.

BACKGROUND: The outer cell wall of the pollen grain (exine) is an extremely resistant structure containing sporopollenin, a mixed polymer made up of fatty acids and phenolic compounds. The synthesis of sporopollenin in the tapetal cells and its proper deposition on the pollen surface are essential for the development of viable pollen. The beginning of microsporogenesis and pollen maturation in perennial plants from temperate climates, such as peach, is conditioned by the duration of flower bud dormancy. In order to identify putative genes involved in these processes, we analyzed the results of previous genomic experiments studying the dormancy-dependent gene expression in different peach cultivars. RESULTS: The expression of 50 genes induced in flower buds after the endodormancy period (flower-bud late genes) was compared in ten cultivars of peach with different dormancy behaviour. We found two co-expression clusters enriched in putative orthologs of sporopollenin synthesis and deposition factors in Arabidopsis. Flower-bud late genes were transiently expressed in anthers coincidently with microsporogenesis and pollen maturation processes. We postulated the participation of some flower-bud late genes in the sporopollenin synthesis pathway and the transcriptional regulation of late anther development in peach. CONCLUSIONS: Peach and the model plant Arabidopsis thaliana show multiple elements in common within the essential sporopollenin synthesis pathway and gene expression regulatory mechanisms affecting anther development. The transcriptomic analysis of dormancy-released flower buds proved to be an efficient procedure for the identification of anther and pollen development genes in perennial plants showing seasonal dormancy.

Exon skipping of AGAMOUS homolog PrseAG in developing double flowers of Prunus lannesiana (Rosaceae).

KEY MESSAGE : Two transcript isoforms of AGAMOUS homologs, from single and double flower Prunus lannesiana, respectively, showed different functions. The Arabidopsis floral homeotic C function gene AGAMOUS (AG) confers stamen and carpel identity. Loss of AG function results in homeotic conversions of stamens into petals and formation of double flowers. In order to present a molecular dissection of a double-flower cultivar in Prunus lannesiana (Rosaceae), we isolated and identified a single-copy gene, AG homolog from two genetically cognate P. lannesiana bearing single and double flowers, respectively. Sequence analysis revealed that the AG homolog, prseag-1, from double flowers showed a 170-bp exon skipping as compared to PrseAG (Prunus serrulata AGAMOUS) from the single flowers. Genomic DNA sequence revealed that abnormal splicing resulted in mutant prseag-1 protein with the C-terminal AG motifs I and II deletions. In addition, protein sequence alignment and phylogenetic analyses revealed that the PrseAG was grouped into the euAG lineage. A semi-quantitative PCR analysis showed that the expression of PrseAG was restricted to reproductive organs of stamens and carpels in single flowers of P. lannesiana 'speciosa', while the prseag-1 mRNA was highly transcribed throughout the petals, stamens, and carpels in double flowers from 'Albo-rosea'. The transgenic Arabidopsis containing 35S::PrseAG displayed extremely early flowering, bigger stamens and carpels and homeotic conversion of petals into staminoid organs, but ectopic expression of prseag-1 could not mimic the phenotypic ectopic expression of PrseAG in Arabidopsis. In general, this study provides evidences to show that double flower 'Albo-rosea' is a putative C functional ag mutant in P. lannesiana.

Chemical and functional properties of cell wall polymers from two cherry varieties at two developmental stages.

The cell wall polysaccharides of Regina and Sunburst cherry varieties at two developmental stages were extracted sequentially, and their changes in monosaccharide composition and functional properties were studied. The loosely-attached pectins presented a lower d-galacturonic acid/rhamnose ratio than ionically-bound pectins, as well as lower thickening effects of their respective 2% aqueous solution: the lowest Newtonian viscosity and shear rate dependence during the pseudoplastic phase. The main constituents of the cell wall matrix were covalently bound pectins (probably through diferulate cross-linkings), with long arabinan side chains at the RG-I cores. This pectin domain was also anchored into the XG-cellulose elastic network. Ripening occurred with a decrease in the proportion of HGs, water extractable GGM and xylogalacturonan, and with a concomitant increase in neutral sugars. Ripening was also associated with higher viscosities and thickening effects, and to larger distribution of molecular weights. The highest firmness and compactness of Regina cherry may be associated with its higher proportion of calcium-bound HGs localized in the middle lamellae of cell walls, as well as to some higher molar proportion of NS (Rha and Ara) in covalently bound pectins. These pectins showed significantly better hydration properties than hemicellulose and cellulose network. Chemical composition and functional properties of cell wall polymers were dependent on cherry variety and ripening stage, and helped explain the contrasting firmness of Regina and Sunburst varieties.

Proteomic analysis of apricot fruit during ripening.

Ripening of climacteric fruits involves a complex network of biochemical and metabolic changes that make them palatable and rich in nutritional and health-beneficial compounds. Since fruit maturation has a profound impact on human nutrition, it has been recently the object of increasing research activity by holistic approaches, especially on model species. Here we report on the original proteomic characterization of ripening in apricot, a widely cultivated species of temperate zones appreciated for its taste and aromas, whose cultivation is yet hampered by specific limitations. Fruits of Prunus armeniaca cv. Vesuviana were harvested at three ripening stages and proteins extracted and resolved by 1D and 2D electrophoresis. Whole lanes from 1D gels were subjected to shot-gun analysis that identified 245 gene products, showing preliminary qualitative differences between maturation stages. In parallel, differential analysis of 2D proteomic maps highlighted 106 spots as differentially represented among variably ripen fruits. Most of these were further identified by means of MALDI-TOF-PMF and nanoLC-ESI-LIT-MS/MS as enzymes involved in main biochemical processes influencing metabolic/structural changes occurring during maturation, i.e. organic acids, carbohydrates and energy metabolism, ethylene biosynthesis, cell wall restructuring and stress response, or as protein species linkable to peculiar fruit organoleptic characteristics. In addition to originally present preliminary information on the main biochemical changes that characterize apricot ripening, this study also provides indications for future marker-assisted selection breeding programs aimed to ameliorate fruit quality.

Changes in total soluble proteins and Ca2+ upon cryopreservation of Prunus mume pollen.

Mei Flowers (Prunus mume) are traditional Chinese ornamental plants. Fifty-one Mei cultivars have been conserved in a pollen cryobank since 2003. We used two-dimensional electrophoresis (2-DE) of total soluble proteins and flow cytometric detection of Ca2+ fluorescence to probe changes in pollen grains before and after cryopreservation. Results indicated that: (1) electrophoresis maps of total soluble proteins before and after cryostorage of pollen from three cultivars were different, even though 70 percent of the protein spots among these three cultivars were matched after cryopreservation. We found some protein spots that changed in all three cultivars; their molecular weights and pI were between 12.6-72.8 kDa and 5.6-7.3, respectively; (2): the geometric mean of Ca2+ fluorescence intensity (GMFI) value of cryopreserved pollen was significantly higher compared with that of fresh pollen in cultivar 'Beijing Yudie'. GMFI increased during pollen germination in our studied cultivars, especially after 0.5 and 1.0 h of culturing. In addition, no positive correlation was found between pollen germination rate and GMFI in the present study.