Molecular characterization and phylogenetic relationships among and within species of Phalaenopsis (Epidendroideae: Orchidaceae) based on RAPD analysis

Random amplified polymorphic DNA (RAPD) analysis for 20 species of Phalaenopsis was conducted to determine their genetic distances and relationships. Among 20 different primers used for RAPD analysis, 10 primers showed polymorphism, and according to the primer type, 26 to 54 DNA fragments were amplified. A total of 414 polymorphic fragments were generated by 10 primers and used for correlation group analysis. The highest value of Similarity index was 0.28 between Ph. violaceamalaysia and Ph. violacea witte. The dendrogram resulting from UPGMA (Unweighted Pair Group Method using Arithmetic average) hierarchical cluster analysis separated the original species into threegroups: The first group had five species of Ph. violacea blue, Ph. belina, Ph. violacea malaysia, Ph. violacea witte, and Ph. gigantea; the second group included Ph. lamelligera, Ph. amabilis, Ph. parishii, Ph. labbi nepal, Ph. speciosa, Ph. lobbi yellow, Ph. venosa, Ph. hieroglyphica, and Ph. maculata; the third group consisted of Ph. minho princess, Ph. leopard prince, Ph. mannii, Ph. modesta, Ph. cornucervi and Ph. pantherina. RAPD markers can thus be successfully applied in this economicallyimportant group of orchids for the study of molecular characterization and relationships. The data acquired from this study could be used for identification and classification of other orchid genera andoriental Phalaenopsis

Exogenous salicylic acid positively affects morpho-physiological and molecular responses of Impatiens walleriana plants grown under drought stress

The aim of this experiment was to investigate the exogenous application of salicylic acid (SA) on morpho-physiological and molecular characteristics of Impatiens walleriana plants grown under water deficit stress. Three levels of soil water contents (95, 85, and 75% of field capacity; FC) and three levels of SA (0, 1, and 2 mM) were applied on two impatient cultivars (‘Tempo’ and ‘Salmon’). The results showed that increasing water deficit stress negatively affected growth and flowering characteristics. On the contrary, the foliar application of SA reduced the adverse effect of water deficit stress and improved growth and ornamental plant attributes. Water deficit increased the amount of electrolyte leakage (EL), malondialdehyde (MDA), peroxidase (POD) and ascorbate peroxidase (APX) activities; and proline content. The expression of the gene encoding for Δ1-pyrroline-5-carboxylate synthetase (P5CS) was slightly increased under control treatment (95% FC + SA 0 mM) and then significantly increased at 75% FC and after the SA treatments. The expression pattern of P5CR (Δ1-pyrroline-5-carboxylate reductase gene) was similar to that of P5CS, with differences in terms of intensity. The application of SA reduced the amount of EL and MDA through increased antioxidant activities and water balance. Overall, the results of this study showed that ‘Salmon’ cultivar was able to tolerate drought stress conditions better than ‘Tempo.’ The application of 2 mM SA increased growth and physiological indices in drought-stressed impatient, mitigating the detrimental effects of water deficit in this important ornamental species

Pollen ultrastructure characterization in Californian and Australian almond cultivars

Pollen morphology can be used for distinguishing species and cultivars of tree fruit species including almond [Prunus dulcis (Mill.) D.A. Webb]. In this study, pollen morphology and ultrastructure of several Californian and Australian almond cultivars has been studied using electron microscopy. Results indicated the efficient use of this trait in the identification of almond cultivars. Several morphological parameters including shape, size and exine characteristics, obtained from an examination of electron micrographs can be used to distinguish pollen from the different almond cultivars, to trace the origins of pollen by honeybees in commercial orchards, and to study gene flow by pollen analysis.K. Sorkheh, A. Vezvaei, M.G. Wirthensohn and P. Martínez-Góme

Effect of Salinity Stress on Some Physiological Traits and Electrophoresis Pattern of Leaf Proteins of Two Barley Genotypes

This experiment was conducted in order to evaluate the effect of salinity stress on some traits of two barley genotypes (Hordeum vulgare L.) at greenhouse of Department of Agronomy and Plant Breeding, Shahrekord University, Shahrekord, Iran. A factorial experiment was carried out based on randomized complete block design (RCBD) with three replications. Treatments included two barley genotypes (Afzal (salt-tolerant) and Ligne527 (salt-sensitive)) and five levels of salinity (Control, 100, 200, 300 and 400 mM NaCl). Results showed that salinity left significant effects on leaf RWC, chlorophyll a and b, sodium, potassium, magnesium, calcium and protein concentrations, sodium/potassium ratio and yield components of barley genotypes. Based on the electrophoresis pattern, protein bands were increased by increasing the salinity levels and protein bands with different molecular weight were observed in different salinity levels. It was found that high concentration of potassium ion along with low concentrations of sodium and proline in barley leaf can be used as a criterion for selection and planting this crop in saline conditions. In addition, identification and isolation of the genes encoding salt resistance proteins in barely and transferring of these genes to sensitive genotypes of crop plants can be useful for breeding and generation of tolerant varieties to salinity

Regulation of the ascorbate-glutathione cycle in wild almond during drought stress

In wild species of almond (Prunus spp.), the activities of ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR), as well as the levels of ascorbate/glutathione pools and H2O2 were subjected to water deficit and shade conditions. After 60 days of water shortage, the species were subjected to a rewatering treatment. During water recovery, leaves exposed to sunlight and leaves under shade conditions of about 20–35% of environmental irradiance were sampled. After 70 days without irrigation, mean predawn leaf water potential of all the species fell from −0.32 to −2.30 MPa and marked decreases in CO2 uptake and transpiration occurred. The activities of APX, MDHAR, DHAR, and GR increased in relation to the severity of drought stress in all the wild species studied. Generally, APX, MDHAR, DHAR, and GR were down-regulated during the rewatering phase and their activities decreased faster in shaded leaves than in sun-exposed leaves. The levels in total ascorbate, glutathione, and H2O2 were directly related to the increase in drought stress and subsequently decreased during rewatering. The antioxidant response of wild almond species to drought stress limits cellular damage caused by reactive oxygen species during periods of water deficit and may be of key importance for the selection of drought-resistant rootstocks for cultivated almond

Salt stress induction of some key antioxidant enzymes and metabolites in eight Iranian wild almond species

The present work describes the changes in the activities of key antioxidant enzymes and the levels of some metabolites in relation to salt tolerance in eight wild almond species. All the species were exposed to four levels of NaCl (control, 40, 80 and 120 mM). Plant fresh biomass, α-, γ- and δ-tocopherol, total soluble proteins, malondialdehyde (MDAeq), H2O2, total phenolics, and the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were analyzed in leaves of salt-stressed and non-stressed plants of the eight almond species. In all the species, salt stress significantly enhanced the activities of SOD and POD, levels of total phenolics and γ- and δ-tocopherols. High levels of salt stress significantly depressed the levels of total soluble proteins, MDA and CAT activity, while salt stress did not significantly affect leaf H2O2 contents. Regression analysis showed that the relationship between salt levels and total soluble proteins, CAT, γ-tocopherol, MDAeq, SOD and POD were statistically significant. Principal component analysis discriminated the almond species on the basis of their degree of tolerance/sensitivity to saline conditions: Prunus reuteri and P. glauca were ranked as salt tolerant, P. lycioides and P. scoparia as moderately tolerant, and P. communis, P. eleagnifolia , P. arabica and P. orientalis as salt sensitive. The results could be used for selecting salt tolerant genotypes to be used as rootstocks for almond cultivation

Exogenous proline alleviates the effects of H2O2-induced oxidative stress in wild almond species (Prunus spp.)

The effect of proline (PRO) on antioxidant system in leaves of eight species of wild almond (Prunus spp.) exposed to H2O2-mediated oxidative stress was studied. The levels of endogenous PRO and hydrogen peroxide (H2O2), and the activities of total superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) and guaiacol peroxidase (POD) were measured. The degradation of chlorophyll but not of carotenoids occurred in leaves in a solution of 5 mM H2O2. An increase in membrane lipid peroxidation were observed in H2O2 treatment, as assessed by malondialdehyde (MDA) level and percentage of membrane electrolyte leakage (EL). Significant increases in total SOD activity and CAT activity, as well as decreases in APX and POD, were detected in H2O2-treated leaves. The three SOD isoforms showed different behaviors, as Mn-SOD activity was enhanced by H2O2, whereas Fe-SOD and Cu/Zn-SOD activities were inhibited. In addition, proline (PRO) accumulation up to 0.1 µmol/g fresh weight, accompanied by significant decreases in ascorbate and glutathione levels, was observed in H2O2-treated leaves. After two different treatments with 10 mM PRO + 5 mM H2O2, total SOD activity and CAT activity were similar to the levels of control plants, while POD and APX activities were higher if compared to the leaves exposed only to H2O2. PRO+H2O2 treatments also caused a strong reduction in cellular H2O2 content, MDA, and EL. The results showed that PRO could have a key role in protecting against oxidative stress injury of wild almond species, so decreasing membrane oxidative damage

Linkage disequilibrium, genetic association mapping and gene localization in crop plants

DNA-based molecular markers have been extensively utilized for a variety of studies in both plant and animal systems. One of the major uses of these markers is the construction of genome-wide molecular maps and the genetic analysis of simple and complex traits. However, these studies are generally based on linkage analysis in mapping populations, thus placing serious limitations in using molecular markers for genetic analysis in a variety of plant populations. Therefore, alternative approach has been suggested, linkage disequilibrium-based association analysis which detects and locates quantitative trait loci (QTL) by the strength of the correlation between a trait and a marker. Although association analysis has already been used for studies on genetics of complex traits in humans, its use in plants has newly started. In the present review, we describe what is known about variation in linkage disequilibrium (LD) and summarize published results on association studies in crop plant species. We give a list of different factors affecting LD, and discuss the current issues of LD research in plants. Later, we also describe the various uses of LD in crop plants research and summarize the present status of LD researches in different plant genomes. Finally, future key issues about the application of these studies on the localization of genes in these crop plants have been also discussed.Sorkheh, Karim; Malysheva-Otto, Lyudmyla V; Wirthensohn, Michelle G; Tarkesh-Esfahani, Saeed; Martínez-Gómez, Pedro