حمید عبداللهی

Erwinia amylovora, the causal agent of fire blight disease in rosaceous plants, contains type III secreted effector proteins including DspA/E, HrpN and HrpW, which are secreted into host plants during the pathogenicity stages. In order to investigate the role of these effector proteins in the interaction with the host plants, susceptible (Bartlett), tolerant (Harrow Sweet) and resistant (Dargazi) pear cultivars were inoculated with wild-type and mutant strains of E. amylovora (hrpW-, hrpN- and dspA/E-) under in vitro conditions. Based on the results, HrpW protein may be involved in pathogenicity in Dargazi cultivar. Different levels of pathogenicity were observed by dspA/E- mutant in cultivars. The results showed the key role of HrpN in the defense mechanisms of Dargazi cultivar, and its pathogenic role in Harrow Sweet and Bartlett cultivars. An increase in ferritin levels was observed in all cultivars inoculated with the wild type strain, but resistant and tolerant cultivars showed higher ferritin levels and a decrease in Fe2+ was observed only in these cultivars. The obtained data show that the HrpW protein does not affect iron homeostasis. Inoculation of Harrow Sweet and Dargazi cultivars with all strains increased ferritin, which was associated with a decrease in Fe2+. Based on the results, it is not possible to associate any of the effector proteins with changes in ferritin and Fe2+. In general, the ability of resistant pear cultivars to increase ferritin levels and regulation of iron can be one of the reasons for their resistance to fire blight. According to the results, different mechanisms are employed by pear cultivars to respond to the causative agent of fire blight.

Drought is a major abiotic stress in arid and semi-arid areas. This study examines how drought stress and different rootstocks affect aerial part physiology and macronutrient uptake in two seedlings of pear cultivars, 'Dargazi' and 'Louise Bonne,' grafted onto 'Dargazi' and 'Pyrodwarf' rootstocks. Treatments were well-watered as control (100% Field Capacity, FC), moderate (60% FC), and severe drought (30% FC). Drought stress decreased the Root-to-Shoot weight ratio (R/SH), Leaf Relative Water Content (LRWC), Soluble Protein (SP), Photosynthetic Nitrogen Use Efficiency (PNUE), leaf osmotic potential (Ψs), Leaf potassium (LK+), Root Calcium (RCa2+), Root Nitrogen (RN), Stomatal aperture (SA), net photosynthetic rate (An), transpiration rate (E), stomatal conductance (gs), and instantaneous carboxylation Efficiency of Rubisco (EiC) in all scion-rootstock combinations. Under drought stress, levels of proline (Prol), Glycine Betaine (GB), Total Soluble Carbohydrate (TSC), root potassium (RK+), leaf calcium (LCa2+), leaf nitrogen (LN), leaf and root phosphorus (P) increased. 'Dargazi' as the cultivar or rootstock showed better instantaneous Water Use Efficiency (WUEi), Nitrogen Utilization Efficiency (NUtE), and Nitrogen Uptake Efficiency (NUpE), with higher LN, LNO3−, LNH4+, Prol, and Ψs under severe stress. 'Louise Bonne' had higher amounts of R/SH weight ratio, Total Nitrogen Accumulation (TNA), leaf and root nitrate reductase activity (NRA),  An, intracellular carbon dioxide concentration (Ci), E, and root nitrate (RNO3−) under moderate stress. 'Pyrodwarf' rootstock demonstrated the highest TNA and RCa2+ under moderate stress conditions. These results indicated that 'Dargazi' demonstrated better tolerance under severe stress, while 'Pyrodwarf' and 'Louise Bonne' were more effective under moderate stress conditions.

Psylla is a key pest in important pear Pyrus Communis -growing areas in Iran. Detection of population fluctuations in ecological models can be traced with time series data. Population dynamics is the result of changes in the population size that ascend from the random and independent contribution of births, deaths, and migrations of population individual members. Population dynamics can be simulated by considering the role of each individual in a time unit as an independent and separate random variable. Mathematical models of resource-consumer relationships can understand miscellaneous patterns of population dynamics, leading to a set of population behavioral patterns under the influence of food resources. This research was conducted on the population dynamics of eggs, nymphs, and adults of pear psylla Cacopsylla pyri L. under feeding conditions from nine pear cultivars in field conditions. Psylla is a key pest of pears and is distributed worldwide. In the climatic conditions of regions like Iran, where spring and summer are dry and rainfall is less, the indirect damage of honeydew secretions is more than the damage from sucking plant sap.

The time series of the population of each growth stage of pear Psylla is a group of observations obtained by regular variable sampling of the eggs, nymphs, and adult Psylla population in a period of four years (2020-2023). The integrated autocorrelated moving average (ARIMA) model was used to forecast the future pear psylla population on nine pear cultivars. ARIMA model suitability criteria and information criterion Bayesian normalized (BIC) were calculated. The plots of residual autocorrelations and partial autocorrelations that show the degree of correlation of the residuals of the model in the actual forecast were premeditated. A cross-correlation model was used to replicate the population model of each developmental stage against the population route of another developmental stage.

The fitted models were significant at the 0.01% level for the populations of pear Psylla on nine cultivars. The ARIMA time series model showed good capacity in forecasting the population of egg, nymph and Adult. Differences among the fit indices of the model were observed in all three developmental stages. The mobility of the growth stage has been one of the most important reasons for these differences. Because with the increase in mobility, the accuracy of sampling usually decreases and population sampling becomes more difficult. The type of host cultivat has also been effective in determining the predictive power of the model. The values of residual autocorrelations and partial autocorrelations in most growth stages and different pear cultivars were smaller than 0.5 in absolute terms, and this indicates that the remaining effective data was not included in the fitting of the time series model in the minimum amount. A sinusoidal trend occurs in the curve of pears Psylla population density fluctuations. The trend of changes in observations was the same as predicted by the model. In some stages such as adult and in cultivars such as Shah Miveh where the population densities were higher than normal, the sinusoidal trend was not observed in the population forecast by the model. The relationship between the population of alternating developmental stages has been direct and increasing and inverse and decreasing at different periods of seasons. These changes were caused by the difference in the pear cultivars quality for pear psylla growth stages. The average absolute value of the cross-correlation varied between 0.3 and 0.4, which indicates the average detection power of each developmental stage compared to the subsequent developmental stage. The maximum detection power in different cultivars was related to the transition of the population from the nymph stage to the adult. In pear cultivars with higher population density, which most of the times had a population above the normal limit, such as Shah Miveh and Dargezi cultivars, the model recognized ability was less, and instead, in cultivars with subnormal population density, such as Boheme and Harvest Queen, the model recognize ability was lower. In cultivars that have less population carrying capacity, births, and mortality reach the equilibrium point earlier than other cultivars. In natural environments, the measurement of living spaces has different dimensions, including nutrition quality.

The flexibility of the models in describing the different annual phenological behaviors of the various growth stages of the pear psylla and the possibility of self-calibrating the models with the help of autocorrelation and cross-correlation models make this approach a valuable tool for monitoring the population of this insect.

Considering the extent of grapevine cultivation in arid and semi-arid areas of the world where salinity stress is one of the important environmental stresses that limits grape production in Iran. Therefore, this research was carried out for preliminary evaluation and comparison of the reaction of three grapevine native cutivars; Bidaneh Sefid, Bidaneh Ghermez, Shahroudi and three hybrids H4, H6 and Kober5BB rootstocks in response to salinity stress in Temperate Fruits Research Center, Horticultural Sciences Research Institute, in Karaj, Iran, in 2015 -2017. The experiments were conducted as factorial arrangements in completely randomized design with five replications under in vitro conditions. The effect of salt was evaluated to identify the most tolerant cultivar/rootstock at four concentration levels of sodium chloride (NaCl); 0 (control), 25, 50 and 75 mM. The results showed significant effect of different salt levels on grapevine cultivars/rootstocks for all vegetative traits including; length of shootlets, number of leaves shootlet-1 and leaf expansion. Most of these traits increased at mild salt stress up to 25 mM. However, at 50 and 75 mM, which are decisive concentrations for tolerance of plant tissues to salinity, the traits showed significant decreases. According to the vegetative growth charcteristics, H6 hybrid rootstock and cv. Shahroudi had relative tolerance to the salinity stress that was confirmed by high preservation of their chlorophyll content, as observed about 2 mg g-1 FW in H6 hybrid rootstock. The total protein and proline contents of leaves showed that the total protein content in all grapevine cultivars and rootstocks followed increasing trend with stress intensity. The proline content had an appropriate association with the higher tolerance level of H6 hybrid rootstock and cv. Shahroudi to 75 mM of sodium chloride.

Dwarfing and nutrient uptake ability are among the important traits in pear rootstocks breeding programs. In this research, growth characteristics and macronutrients and iron uptake ability was compared in seedlings of 13 native and introduced species of genus pear (Pyrus), one commercial interspecies hybrid and three common clonal rootstocks of Pyrodwarf, Quince EMA and Quince BA29 from the species of genus Cynodonia (Cydonia oblonga Mill.). Evaluation was carried-out under controlled conditions using completely randomized design with 10 replicates in 2022. Growth characteristics and chlorophyll index in 70, 120, and 160 days after establishment were evaluated and measured. Nitrogen, phosphorus, potassium and iron uptake was evaluated and compared in Pyrus and Cydonia rootstocks 160 days after seedlings establishment. The results showed that the highest dwarfing rate belonged to P. syriaca followed by the clonal rootstocks, and the highest growth rate was measured in seedling rootstocks of P. communis derived from cv. Dargazi followed by P. bretschneideri. In P. syriaca, the lowest internode length was observed after 160 days with an average of 1.61 cm, which indicated the effect of dwarfing on slowing the growth of this species. Regarding the uptake of nutrient, P. hyrcana, P. nivalis, and P. pashia had the highest nitrogen uptake, P. amygdaliformis and P. nivalis had the highest phosphorus uptake and P. syriaca had the highest leaf potassium content. Considering the results of this research, future researches should focus on e evaluation of using P. syriaca as a dwarf rootstock for in establishment of intensive/ highly intensive pear orchards, or as the parent for dwarfing traits in pear breeding programs.

This research was conducted to identify the fire blight resistance and related oxidative responses in quince genotypes.  KVD4, NB2, PH2 and KVD3 genotypes and Quince C rootstock were inoculated in vitro with Erwinia amylovora Ea273 and necrosis progress and ROS generation, including O2-, H2O2 and OH- in control and infected shootlets was compared. Results showed three types of oxidative responses in genotypes. In NB2 and Quince C rootstock, with a higher level of disease resistance, they had a fast O2- increase, a delay in H2O2 generation, and a faster increase in OH- severity. KVD4 had a moderate susceptibility level and similarly moderate behavioral in generation of three ROS. In third group, more susceptible genotypes, PH2 and KVD3, showed low O2- generation, faster H2O2 increase and slower rate of increase of OH- level. It seems that defensive mechanism of quince against the fire blight disease is completely different from pear tree, which mainly accumulates H2O2 as a barrier. 

Fire blight (Erwinia amylovora) is considered the most important limiting factor for pome fruit trees such as apples, pears and quinces (Van der Zwet, and Keil, 1979). Numerous factors are effective for E. amylovora’s pathogenicity and molecular interaction with host plants, but the oxidative burst is the critical factor that results in host cell degradation and pathogen growth (Azarabadi et al., 2016). Among various hosts of fire blight causal agent, the quince trees are the most susceptible one and the disease usually causes large disease symptoms such as bloom blight, shoot blight, canker and trunk necrosis that leads to entire decline of the tree in the outbreak years (Van der Zwet, and Keil, 1979). Quince tree also is native to Iran and this country is among the main producers of quince fruits in the world (Abdollahi, 2023). Due to importance of quince tree in Iran and high damages of fire blight disease on it, the current research was conducted to evaluate the mechanisms of resistance to this disease in level of oxidative burst and severity of generation of various reactive oxygen species in the different quince genotypes.
 

Quince genotypes including KVD4, NB2, PH2 and KVD3, along with Quince C rootstock were established in in vitro conditions on modified QL medium and inoculated with Erwinia amylovora type strain Ea273. Following this step, the progress of disease necrosis and generation of reactive oxygen species (ROS), including superoxide radical (O2-), hydrogen peroxide (H2O2) and hydroxyl radical (OH-); as the main species of active oxygen during interaction of E. amylovora with the host plants (Venisse et al., 20002), were compared in three separate experiments in control and infected in vitro shootlets. Severity of the generation of each reactive oxygen species evaluated by the index of red color in the tissues of quince genotypes from score 0 (without any trace of ROS) to 5 (the highest severity of each individual ROS) following the colorimetric method described by of Azarabadi et al. (2016). Traces of superoxide radical, hydrogen peroxide and finally hydroxyl radical were determined by nitro blue tetrazolium (NBT), 3, 3´-Diaminobenzidine-HCl (DAB)-HCl and Dimethyl sulfoxide (DMSO), respectively, Following Azarabadi et al. (2016). Data were collected in 120 hours time course after inoculation of in vitro shootlets with with Erwinia amylovora type strain Ea273, and the curves were depicted using Microsoft Excel.
 

The results showed three types of oxidative stress and ROS generation patterns in responses to fire blight disease progress in the tissues of studied quince genotypes. Quince C and NB2 genotypes, with higher levels of disease resistance, demonstrated faster increase in the superoxide generation, delay in the generation of hydrogen peroxide, and faster increase in severity of the hydroxyl radical. Also, KVD4 genotype had moderate susceptibility level to the disease and similarly moderate behavioral of the amount of the generation of three reactive oxygen species including superoxide, hydrogen peroxide and hydroxyl. In the third group, the more susceptible genotypes, PH2 and KVD3, showed fast necrosis progress, low generation of superoxide, faster increase of hydrogen peroxide and slower rate of increase of hydroxyl radical level. Considering the various patterns of ROS generation in the evaluated quince genotypes, it can be concluded that the defensive mechanisms of the quince tree against fire blight is completely different from pear tree in which the accumulation of hydrogen peroxide is the main barrier for resistance to the fire blight disease (Azarabadi et al., 2016).

The plateau of Iran has very high diversity of different species of the genus Pyrus that has not been evaluated at the species level and used in the national pear breeding programs. The present research was carried out with the aim of evaluating the variation in fruit, seed and the initial seedling growth characteristics of 10 native pear species and comparing them with three East Asian pear species during 2021-2022. The results showed that P. salicifolia and P. hyrcana species had the highest and lowest seed thickness that could be used to distinguish these species. The highest (226.5 g) and lowest (0.67 g) fruit weight was observed in the two Asian pear species, P. bretschneideri and P. betulifolia. The evaluation of the seedlings of pear species showed that the highest seedling height, stem diameter, number of internodes, number of leaves, number of leaflets and petiole length belonged to the seedlings of P. communis cv. Dargazi, and the lowest related to P. pashia. Cluster analysis based on morphological and pomological characteristics grouped pear species in two groups. The first group included P. communis cv. Dargazi and P. bretschneideri that were very similar for pomological characteristics. Considering the importance of breeding for devlepment of dwarf rootstocks, it is necessary to study the dwarf pear species especially P. pashia in future and for longer period.

Tolerance to deficit irrigation and related mechanisms are very important characteristics of seedling and clonal pear rootstocks for successful commercialization. In this study, seedling rootstocks, Dargazi and Pyrus betulifolia Bunge, and clonal Pyrodwarf, OH×F69 and OH×F87 rootstocks for tolerance to deficit irrigation as well as enzymatic anti-oxidative mechanisms in response to the stress was evaluated under greenhouse conditions at temperate fruits research center, Horticultural Science Research Institute, Karaj, Iran, in 2018. The deficit irrigation stress applied at three levels: control, mild and severe by irrigation at 100, 75 and 50 percent of field capacity (FC), in greenhouse during 60 days. Rootstock heights, generation of hydrogen peroxide (H2O2), electrolyte leakage and the activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (POX) were assessed at 30 and 60 days following the application of deficit irrigation stress. The results showed that Pyrodwarf rootstock had greater tolerance to deficit irrigation stress, even at 50% FC. The generation of H2O2 was between 23.7 μM g-1 of fresh weight in OH×F87 and 32.5 in P. betulifolia Bunge. However, as the deficit irrigation stress severity and duration increased, the H2O2 level enhanced to its maximum of 81.3 μM g-1 of fresh weight, and was highly correlated (r = 0.734**) with electrolyte leakage. In addition, the calculated correlation coefficients confirmed the order of increase in the activity of SOD and then CAT in response to the increase in the intensity of deficit irrigation stress. Based on the results of this study, tolerance mechanisms to deficit irrigation stress in pear rootstocks is partly attained by converting superoxide into hydrogen peroxide (H2O2), followed by preventing its accumulation.

Oxidative stress of the fire blight disease in host plant consists of chloroplastic and mitochondrial oxidative stresses that leads to the necrosis of tissues. This research was conducted to quantify and compare the role of oxidative stress of these organelles using glutaraldehyde as chloroplastic inhibitor of electron transport chain (ETC) and rotenone as mitochondrial inhibitor ETC. Due to the necrotic effect of inhibitors, in the primarily tests, different concentrations of inhibitors were examined under in vitro conditions and two concentrations of inhibitors (5 and 10 mg l-1) were optimized for co-cultivation tests of host-pathogen interaction. In co-cultivation tests, necrosis appearance was recorded at 48 and 72 hours after inoculation in susceptible cv. Bartlett and tolerant cv. Harrow Sweet, respectively. Although both concentrations of inhibitors postponed necrosis appearance and reduced necrosis progress rate, but in cv. Harrow Sweet, higher effects of glutaraldehyde were observed in 10 mg l-1. The higher effects of chloroplastic glutaraldehyde inhibitor demonstrated more effective role of the chloroplastic ETC in oxidative stress of pathogen in comparison with the role of mitochondrial ETC. Additionally, in susceptible cv. Bartlett, mitochondrial inhibitor caused similar necrosis progress rate to the chloroplastic inhibitor which demonstrated another evidence for more effective role of chloroplast organelle in resistance to the fire blight disease in cv. Harrow Sweet.

Despite adaptability of Pyrodwarf semi-dwarf pear rootstock in Iran, the final yield and yield efficiency of different commercial pear cultivars on this rootstock have not been studied and analyzed in detail. Therefore, in recent study, the yield, yield potential and yield efficiency of four commercial pear cultivars including Louis Bonne, Spadona, Dargazi and Beyrut cultivars were evaluated on Pyrodwarf rootstock during four years (2017 to 2020) in commercial bearing phase. Growth traits according to high vigor of Dargazi and Spadona cultivars were higher than Louise Bonne cultivar and all cultivars in 2020 (8 years old) had a height between 294.4 to 352.7 cm, which indicates semi-dwarf habit of this rootstock. The highest yield per tree was in Dargazi cultivar and then at a lower level in two cultivars Spadona and Louise Bonne. In spite of increase in tree yields with increasing age of the trees, the yield per trunk cross-sectional area (TCSA) decreased consistently, so this index in 2017 was more than 0.2 in most cultivars and decreased to about 0.05 kg per cm2 TCSA in two years 2019 and 2020. A similar situation was observed in terms of fruit number and yield per unit volume of canopy and the highest efficiency of canopy volume unit was observed in Louise Bonne cultivar. It can be concluded that for higher yield efficiency of pear cultivars on Pyrodwarf rootstock, evaluation of training forms that decrease the canopy shading in the internal parts of canopy is essential.

Rootstocks are very important for the production of a healthy and fruitful product, and without having well-matched rootstocks with the physical and chemical conditions of the soil as well as the weather conditions; one cannot hope to have productive orchards. The objective of this research is to find the efficiency of leaf nutrient uptake on fruit quality and shelf life (brown spot) in quince (Cydonia oblonga Mill.) cultivars (Behta,Vidoja and Isfahan) and promising genotypes ("KVD2", "NB2") grafted on hawthorn (Crataegus spp.) and quince seedling (Cydonia oblonga) rootstocks grown in heavy calcareous soil. This study suggests that, higher mineral nutrient uptake of studied cultivars or genotypes favored by hawthorn (Crataegus spp.) rootstocks, makes them suitable for heavy and calcareous soils. ‘KVD2’/hawthorn combination in our experiment demonstrated higher mineral nutrient uptake than other studied combinations in heavy (56% silt; 14% loam) and calcareous soils (28% calcium carbonate equivalent in soil) with slight saline (2.08%) and pH of 7.67. None of the studied cultivar/rootstock combinations were found to have adequate nutrient ratios in fruit that could reduce the risk of brown spot and increase storage capacity in the cold storage.

The center of origin of quince is Talysh region in northwest of Iran and the Caucasus. There are numerous centers of diversity of this tree species in Iran, Republic of Azerbaijan, Turkey and Europe. In this study, the genetic relationships of genotypes and cultivars of quinces collected from the center of origin of this tree species in the west of Guilan in Iran and the Caucasus region were compared with the genotypes and cultivars from different centers of diversity of this species in Khorasan, Isfahan, Ardabil, Western Azarbaijan and Tehran provinces in Iran as well as genotypes from Turkey and Europe using 12 and 14 pairs of SSR markers developed from apple and pear. SSR markers were successfully transferred to the quinces and led to the distinction of Japanese and Chinese quinces from the genotypes belong to the genus Cydonia, and also grouped 63 quince genotypes in seven clusters. The highest allelic frequency (0.968) was observed in CH03g06 and KU10 markers. The germplasm of Europe was clustered in an independent group, while Quince C was grouped with the germplasm of northwest of Iran and the Caucasus. Analysis of genetic structure of the germplasm approved the results of cluster analysis and confirmed the previous reports in relation to two independent evolutionary pathways of the quinces from the Caucasus and northwest of Iran to Turkey and Europe, and the second pathway toward central and northeast regions of Iran. Comparison of these evolutionary relationships of the quince genotypes with the previous reports on morphological and organoleptic evaluations of fruits indicated that each group of identified germplasm has different breeding potential for being used in quince breeding programs.

In the present study, seven native and five introduced pear (Pyrus communis L.) cultivars were evaluated for fruit morphological traits and biochemical characteristics including total soluble solids, total titratable organic acids, acidity of juice, sclereid cell density and size, ascorbic acid and organoleptic attributes. The results showed that in fruit morphological evaluations, the most important distinguishing traits were general shape and fruit size, length: diameter ratio, position of maximum diameter, fruit side profile, background color and size of lentils in ground color, size of over color area and the characteristics of fruit stalk. Also, three very similar cultivars, Coscia, Louis Bonne and Spadona, showed that these similarities has caused synonym and homonym names for them in some nurseries. However, they were distinguishable by the fruit characteristics including size, thickness and curvature of stalks. Total soluble solids contents of fruit varied from 14 to 17.4%, and the lowest was observed in Beurre Giffard cultivar and the highest in Felestini. Total titratable acid content of the fruit also varied between 3.4 mg g-1 of fresh weight in cv. Dargazi, cv. Louis Bonne and cv. Spadona and 11.4 mg g-1 of fresh weight in cv. Domkaj. In general, the highest overall score of fruit quality in organoleptic evaluations belonged to cv. Louis Bonne, which due to its excellent quality at the ripening time and other characteristics such as compatibility with the clonal rootstocks and fire blight tolerance has become the most popular commercial pear cultivar in Iran, in recent years.

The aim of this study was to investigate the growth and early bearing potential of some commercial and fire blight resistant pear cultivars on OH × F87TM rootstock and to compare this rootstock with the commercial semi-dwarf Pyrodwarf rootstock. The pear cultivars were Louise Bonne, Dargazi, Spadona as the three most popular pear cultivars in Iran, and two newly introduced cultivars, Super Elliot and Packham`s Triumph, which have been evaluated under Karaj climatic conditions for four years (2017-20). The rootstocks were micro-propagated from virus free materials and the trees were two year old nursery plants. The tallest tree height was observed in cultivars Dargazi on both OH × F87TM and Pyrodwarf rootstocks and also the highest spur density was 12 spurs per meter in three graft combinations of Louise Bonne and Packhams cultivars on OH × F87TM rootstock and Spadona on Pyrodwarf. The use of two year old trees caused early bearing of trees in the first year after planting, and flowering in the second year on OH × F87TM rootstock with about 40 blossoms per tree, while Pyrodwarf had about 37.5 blossoms per tree. The highest fruit yield research period observed in cv. Dargazi and cv. Super Elliot, however, the latter showed high susceptibility to pear psylla. On the other hand, cv. Spadona which normally has a low fruit yield on Pyrodwarf rootstock, had higher fruit yield on OH × F87TM rootstock. In general, OH × F87TM rootstock, due to lower growth and relatively higher fruit yield had high yield index per trunk cross section in grafted trees, and in addition to cv. Dargazi, Louise Bonne also had high yield index per trunk cross section on this rootstock. The results showed that OH × F87TM rootstock can be considered as suitable, and even superior to Pyrodwarf, for pear cultivars in the continuation of this research.

Recent quince breeding programs has resulted in release of new cultivar Viduja and Behta and presentation of promising Esfahan-2, Esfahan-3 and Esfahan 5 genotypes. This research was conducted to discriminate these cultivars by morphological and molecular markers. Morphological markers were based on 38 characteristics from discrimination, uniformity and stability (DUS) tests, while for molecular markers, 15 primer pairs of apple and pear SSR markers were used. Cluster analysis on morphologic and banding pattern of SSR marker demonstrated distinctness of all evaluated cultivars and promising genotypes. Among morphological markers, tree vigor and growth habit, shoot color and position of bud in relation to the shoot, leaf size and undulation of blades, bloom color and fruit traits were key characteristics. Cultivar Esfahan, based on tree growth habit and fruit shape, cv. Viduja based on tree form and leaf blade undulation, bloom color and flowering time have been discriminated, while in Esfahan-2, Esfahan-3, Behta and Esfahan-5, the fruit shape, position of but in relation to the shoot, fruit neck and finally green-brown of shoot color, respectively were the most discriminative characteristics. In molecular markers, 10 polymorph alleles with mean 3.3 alleles per locus were observed. The highest allele numbers and PIC indices were observed for CH05d04, CH04a12 and CH02b10 primer pairs. Three primer pairs belong to CH04a12, CH05d04 and Ch02b10, SSR loci were more discriminative and three primer pairs, including NH015a, CH04a12 and NB103a with one of the CH01d08, CH05d04 or NH011b were adequately discriminative for all evaluated quinces.

Pyrodwarf and OH × F69 rootstocks are the main clonal rootstocks for pear trees in Iran. This research was conducted to compare growth and nutrient uptake in different commercial pear cultivars including; Louise Bonne, Dargazi and William`s Duchesse on Pyrodwarf, OH × F69 and Dargazi seedling rootstocks in two years in the nursery. Both clonal rootstocks inducted higher growth in cultivars. Cultivar Louise Bonne had the highest growth on Pyrodwarf rootstock. Calcium content varied from 1.4% to 1.5%, but nitrogen, phosphorus, potassium and manganese showed higher variation, and the highest content of these nutrients were observed in cultivar Dargazi on Pyrodwarf rootstock. The lowest and the highest variations were observed in zinc and iron content, respectively. In addition, about 30% of total iron of the leaves was active iron, indicating high level of active iron in pear in comparison with other fruit tree species. In all graft combinations, variation in micro and macro nutrients contents were in optimum range. Comparison of nutrient contents with active lime level in soil indicated that the range of 10-15% active lime in soil would not hinder growth and nutrients uptake of plants.

Quince (Cydonia oblonga Mill.) is considered as a self-compatible species, but some levels of self-incompatibility also have been reported in its cultivars and genotypes. Therefore in this research allelic diversity, isolation and deposition of alleles has been considered in some indigenous quince cultivars and genotypes of Iran. The primes were designed according to the C1 to C5 conserved regions of apple and pear species. 55 genotypes, cultivars and related species of quince were evaluated and amplification of this locus demonstrated various band lengths between 500 to 1100 bp with 13 various sizes. After partial sequencing, these bands primarily were coded as Sq1 to Sq13, but the frequency of two putative alleles, Sq13 and Sq4 where higher than other respectively with 17.7 and 14.4%. Sequencing of the first self-incompatibility allele (S1) in KM1 genotype or cultivar Torsh Esfahan revealed the highest homology of this allele with S6 of apple species Malus domestica Borkh. and Ss (S111) of pear species Pyrus communis L., respectively, with 94 and 93 of nucleotide similarity.

Fire blight, the most important disease of pear tree causes necrosis by an oxidative stress in tissues. Therefore, identification of resistant cultivars and mechanisms of resistance to the oxidative stress of disease, that are mainly related to the chloroplasts, are important in breeding programs of this tree.  In order to study the role of chloroplasts in this interaction, expression of chloroplastic gene psbA that are under control of oxidation/reduction (redox), was evaluated in susceptible (Williams) and resistant (Harrow Sweet) cultivars during 48 h post inoculation by Erwinia amylovora in in vitro condition. In addition, expression of this gene was studied at presence of glutaraldehyde and rotenone as the inhibitors of the electron transport chain of chloroplast and mitochondria, respectively. The results showed higher necrosis progress rate in the in vitroshootlets of susceptible cultivar. Expression of psbA gene at presence of inhibitors in both presence and absence of E. amylovora was higher in cultivars Harrow Sweet. According to the results, the higher resistance level of cultivars Harrow Sweet to the disease could be due to the higher rapid responses and reaction of the chloroplasts of this cultivar in comparison to the cultivar Williams.

Quince seedling genotypes are distributed in independent landraces in different parts of Iran. The selectection oftheir superior genotypes is possible for usingin some breeding programs. This research was performedto evaluate some quince genotypes of North West Iran and selection of superior genotype(s). Therefore, 13 genotypes from Ardabil and western regions of Guilan provinces,with cultivar `Esfahan` as control,were evaluated according to 55 traits of the National Guidelines ofDifferentiation, Unifirmity and Stability (DUS) Tests, and also organoleptic and yield traits. The results indicated some traits were distinct in growth habit, leaf, blossom and fruit in quince genotypes and in control cultivar. Dwarfing in AD6 and AD7 genotypes and late flowering in AD5, AD3 and PSH genotypes were considerable traits. Cluster analysis based on all traits, dividedthe genotypes in three clusters, in which the first was containg superior genotypes Givi, AS1, ASH, AD1 and control cultivar. In the second and third clusters, genotypes had lower values for selection. In the organoleptic evaluations, ASH, AD1, and AS1 were evaluated assuperior genotypes, so that both ASH and AS1 genotypes were considered for possibile use as fresh fruits, with higher organoleptic values than cultivar `Esfahan`. Givi, AD5 and AD6 genotypes with 28, 23 and 21 kg fruit per tree had the highest yield and yield efficiency. Based on all traits, Givi, AD1, ASH and AS1 genotypes were selected preliminarily for various purposes of breeding programs.

New identified alleles of self-incompatibility locus in Pyrus communis and renumbering of these alleles caused some confusion in their evaluation and categorization. Therefore, this research was performed for a comprehensive bioinformatics review on all 27 S-alleles of this species, and identification of S-alleles in some native Iranian pear cultivars. The results demonstrated that 21 S-alleles, out of 27 identified S-alleles are completely sequenced, that subsequently all 13 parts of them, including promoter, signal region, conserved C1 to C5, intron region and 6 intermediate region were aligned. Bioinformatic analysis revealed considerable conservation also in promoter, signal and terminal parts of locus and their appropriateness for primer design, also showed presence of two CAAT and two coherent TAAT boxes in most promoter regions of S-alleles. Cluster analysis of various parts of alleles showed the complete similarity of polypeptide sequence of S119 and S121 alleles, but in intron region they were moderately different, this high similarity level causes some mistakes in S-alleling of some cultivars such as Dargazi. Comparison of the results also demonstrated that due to sequence similarities and gene flow of other species, the specific primer method is not a trustable method for S-alleling in pear. Finally, S-alleling of some cultivars confirmed S104 in two control cultivars, Coscia and Beurre Diel, also in central Asian cultivar, Krus Siehan, also S108 in Krusalun and S107 in Shekkari and Shahmiveh cultivars, while S119 in Esfarayeni and Dargazi. Interestingly, S35 from P. ussuriensis in Shirin Torkan, Konjuni and Kaftarbache cultivars and S19 from P.×bretschneideri as the second allele of Shekkari cultivar were detected that reconfirming the previously reported gene flow of other Pyrus species in the native Iranian pear cultivars.

Tolerance to drought stress is important characteristic related to growth of pear trees and selection of rootstocks for orchard establishment. In this research, growth and physiological indices were evaluated in several pear rootstocks including; micropropagated Dargazi, Pyrus betulifolia and three clonal rootstocks; Pyrodwarf, OH×F69 and OH×F87 after 60 days in deficit irrigation conditions. Deficit irrigation levels were 75% and 50% of filed capacity and non- stress condition as control were implementend in greenhouse. P. betulifolia and OH×F87 rootstocks demonstrated the highest and lowest growth rate and tolerance to the deficit irrigation conditions based on relative growth rate (RGR) and leaf number (tgαln). Monthly evaluation of leaf relative water content (RWC), proline, total carbohydrates and total proteins as well as membrane stability and electrolyte leakage showed that P. betulifolia with 72.1% RWC had the lowest level of this index in optimal (control) condition. However, despite the highest reduction of RWC to 57.1 and 58.3, on 30 and 60 days after deficit irrigation, respectively, in P. betulifolia, this rootstock could maintain the highest growth rate. Based on the results of this research the highest levels of tolerance to the deficit irrigation was observed in P. betulifolia followed by Pyrodwarf, OH×F69, Dargazi and finally OH×F87 rootstocks, respectively. These results showed the importance of selection of tolerant pear rootstocks and need for further orchard evaluation of them for establishment of pear orchards in stressful conditions.

Response of pear cultivars to causal agent of fire blight diseases is expressed by both resistance and tolerance, however the difference of the two is not clear. To better understand the mechanisms of resistance and tolerance of pear cultivars to the disease, the necrotrophic behaviour and electrolyte leakage of resistant (Dargazi) and tolerant (Harrow Sweet) cultivars was compared with susceptible cultivar (Barttlet) after inoculation by wild type and mutant strains (hrpN-, dspA/E- and hrpW-) of the bacterium. The appearance of symptoms in reaction to wild type strains occurred after three days in susceptible and tolerant cultivars, and in seven days in resistant cultivar. However, in resistant cultivar, Dargazi, disease progress slowed down. In all cultivars, one to two days before necrosis, electrolyte leakage increased to ~70%, and with the completion of necrosis it reached to 100%. The mutant strain hrpW- did not affect incidence of necrosis and electrolyte leakage, indicating no effect of this protein on resistance mechanisms. Using strain hrpN- increased the necrosis and electrolyte leakage in resistant cultivar and delayed these indices in tolerant cultivar in comparison with susceptible cultivar. Also, dspA/E- strain accelerated necrosis and electrolyte leakage in resistant cultivar in comparison with tolerant cultivar, and had no symptoms on susceptible cultivar. Considering the dual role of HrpN in pathogencity and stimulation of host defense system, the results indicated key role of HrpN protein on acquired defense system (ADS) in relation to the pathogenic role in the resistant cultivar (Dargazi) and its inverse relationship in tolerant cultivar (Harrow Sweet). This dual behaviour can be used as a tool for deeper understanding of the fire blight resistance mechanisms in pear, and also as an index for distinctness of resistant and tolerant pear cultivars.

Due to several reasons such as firmness and high astringency, the fruits of quince are rarely used as table fruit, however, there are genotypes that produce fruits for table fruits. Considering this issue, in current research, the organoleptic properties and their relationship with physicochemical attributes of fruits of quince genotypes collected from different regions of Iran were evaluated in Karaj, Iran. The organoleptic properties included aroma, juiciness, sensory firmness, astringency and taste of pulp, while physical fruit firmness, pH, TSS, TA were also evaluated as physicochemical attributes. Means of physicochemical attributes were: physical fruit firmness with 12.6 kg/cm2, TSS with 16.2 °Brix and TA equivalent to 9.8 mEq/mg titratable acids. Fruits of quince genotypes originated from Kashan region, especially KVD4, with physical fruit firmness as high as 15.3 kg/cm2 had the firmest fruit texture. On the contrary, the fruit of genotypes originated from Guilan region, in general, had the softest fruits texture. TSS in all genotypes ranged from 14-19 °Brix, but similarly the fruits of Guilan region had the lowest TSS levels. PH2 and SVS2 genotypes had the highest TSS that could be the main reason that they gained highest sensory values in the organoleptic tests. The organoleptic tests demonstrated that sensory values were highest in the fruits of genotypes originated from Isfahan plain; in this case the highest sensory values were evaluated in fire blight susceptible genotype, KM1, followed by NB4 and Isfahan cultivar. The lowest sensory values were scored in Guilan genotypes, and AS2 genotype demonstrated the lowest scores. Fruit firmness by sensory evaluation were significantly correlated with physical firmness. Correlation analysis also showed that the total score of fruit in organoleptic tests were significantly and positively correlated with all of the organoleptic properties, except fruit astringency. It is concluded that the quince genotypes originated from Isfahan province are the most important genetic resources for selection and breeding of new quince cultivars, both for growth and bearing habit purposes as reported in the previous works as well as for fruit quality based on the results reported in this research.

Pear seedlings are the most predominant rootstocks for pear trees in Iran that are vigorous and show diversities. In addition, the use of semi-dwarfing clonal quince rootstocks is limited due to their susceptibilities to stresses. Based on these, Pyrodwarf pear rootstock could be considered as a new choice for intensive orchards, therefore, in this research growth and bearing of four important commercial pear cultivars including Beyrouti, Dargazi, Louise Bonne and Spadona cultivars were evaluated on this rootstock from 2012-2014. The orchard was established with 333 trees/hec and modified leader training form. The highest diametric growth of rootstocks, trunk diameters, tree heights, number of lateral shoots and annual growths were observed in the Spadona, Dargazi and Louise Bonne cultivars, respectively. All pear cultivars at the first year demonstrated higher diametric growth and lower height comparing to the standards of pear trees on the seedling rootstocks. In addition, cultivar Beyrouti with the lowest diameters of the stock and scion, and reduced 30% of growth was the most dwarf combination. All cultivars bloomed at the second years and had small quantities of fruit bearing at the subsequent year, but the highest bloom density and rate of spur/trunk surface area were observed in Dargazi, while the highest spur density along the branches observed in cultivar Beyrouti. According to the results, Pyrodwarf rootstock with dwarfing effects about 30%, early bloom initiation and bearing in the second and third years of cultivation could be considered as a promising choice for establishment of semi-dwarfing pear orchards.

In this research, morphological, leaf chlorophyll and its variations, biochemical traits related to the fruit quality and sclereid cell cluster characteristics were evaluated in 15 introductions of European pear cultivars. Morphological characteristics based on 68 traits of the national descriptors for distinctness, uniformity and stability as well as chlorophyll were evaluated during growing period. Morphological evaluation revealed distinctness in tree, branch, leaf, flower and fruit traits. Among the evaluated traits, color of branches, length : width ratio of leaf, position of petal margins, length : diameter ratio, position of largest diameter and color of fruit skin, and the characteristics of fruit stalk were highly distinctive. Length : width ratio of leaf, ranged from <1.4, 1.4-1.5, 1.5-1.6, 1.6-1.7 and >1.7 in very narrow to very broad leaves. For length : diameter ratio of fruits ranged from <1.0, 1.0-1.2, 1.2-1.4, 1.4-1.6 and >1.6 indicated extremely wide to extremely narrow fruits. In addition, quantitative traits showed that these traits were mostly consistent with the control cultivars of the UPOV descriptor, however, low stability was observed in some traits such as blooming time. Leaf chlorophyll content changes showed varied patterns, but mostly increased in the beginning of summer and decreased toward leaf fall. Meanwhile, the highest chlorophyll indices were found in Alvert, Beurre Diel and Doyenne du Comice cultivars. Based on the results of this study, Packhams Triumph, Doyenne du Comice and Bulghar No. 2 were identified as superior cultivars.