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  • Identification of ripening-related genes in strawberry fruit by cDNA-AFLP
    33-41.
    Views:
    148

    An RNA fingerprinting study of strawberry receptacle and achene tissue was performed to identify candidate genes involved in fruit ripening. Quantitative cDNA-AFLP was used to detect differential gene expression in green, white, pink and red stages of fruit ripening. Based on hierarchical average linkage clustering the differentially expressed genes formed three major groups, genes expressed only in green receptacle, genes expressed mainly in white, pink and red receptacle, and in achene. 130 transcript-derived fragments (TDFs) were isolated and sequenced. Most TDFs did not show any homology to sequences with known functions, others were homologous to genes involved in oxidative stress response, signal transduction, regulation of development and cell-wall metabolism. Novel genes, so far not associated with strawberry ripening and ripening in general, were identified, such as genes encoding a bHLH protein, putative nitrilase-related protein, putative HD-zip protein. The differential pattern of gene expression draws the attention to the significance of ripening induced-or repressed promoters in strawberry fruit, whose isolation and characterization can be useful tool for functional genomics. For this purpose nine cDNA-AFLP fragments related either to ontogeny or senescing were completed with 5'UTR aiming at more precise annotation and future promoter isolation. Although tens of potentially important transcriptome changes were identified, the function of many ripening induced genes remain unknown.

  • Inheritance of fruit colour and of shoot's pigmentation in the case of interspecific raspberry hybrids
    33-36.
    Views:
    103

    In our research, fruit colour and the shoot's red pigmentation were evaluated in the hybrids of Rubus idaeus and Rubus parvifolius crossings. Y and Ys genes beside the T genes determine the fruit colour of interspecific hybrids, which is characteristic for raspberry. For the explanation of the significantly higher results of segregation then expected at the yellow fruit colour hybrids, we have supposed the presence of a second yellow gene (Y2). In the yellow colour, a lot of different shade colours can be identified from light yellow to the apricot colour. In the regulation of the production of yellow and red colour, several other genes can participate also. Identification of these genes would require more additional research. The C gene determines the shoot colour of raspberry and in the case of wild raspberries we have revealed the role of a dominant Pr gene. The Y and Pr genes are descended linked. The value of crossing over is approximately 15%. The anthocyanin production inhibitory effect of the Y gene extends only for fruit. At the shoots of yellow fruit plants, strong anthocyanin production was observed.

  • Xanthomonas resistance in Hungarian 4 spice pepper varieties
    73-77.
    Views:
    144

    With a view to further enhance the reputation of Hungarian spice pepper it was necessary to improve resistance to the bacterium Xanthomonas campestris pv.vesicatoria, the most dangerous pathogen of pepper varieties. From among the familiar resistance genes in Hungary only the gene Bs-2 could provide sufficient protection against the aggressiveness spectrum of the bacterium species X.c.pv. vesicatoria. The first results of the resistance breeding are the spice pepper varieties Kaldom and Kalorez. In addition to the Bs-2 gene attempts are also being made at building in a gds gene into pepper, a gene creating a general defense system, a different strategy towards Xanthomonas campestris pv. vesicatoria.

     

  • Application of DNA markers for detection of scab resistant apple cultivars and selections
    59-63.
    Views:
    103

    A DNA marker-based study was undertaken to identify the occurrence of major scab resistance genes in some apple cultivars and selections of importance for apple breeding. Unfortunately none of the RAPD-based markers previously reported to detect the Va, Vb, Vr and Vx genes produced unambiguous results. By contrast, the CAPS marker MI8 produced the expected three bands in all cultivars and selections already known or suspected to have the Vf gene, as well as in the Russian cultivar 'Antonovka Polotora Funtovaja' suspected to have Va resistance which however may be allelic to Vf. Vf-carrying selections and newly named cultivars 'Frida' and 'Fredrik' are grown successfully in Sweden without fungicides, suggesting that the Vr resistance breaking scab races 6 and 7 have not yet become a problem. The SCAR marker B12 detected the Vm gene in 'Prairifire', 'Rouville', clones 'OR45T132' and 'OR48T70', and selection '16-36-193'. The SSR locus 0102b10 detected one band at 118 by in 'Reka'. This is presumed to be identical to the Vr gene marker previously reported.

  • The genetic background of resistance to common bacterial blight in newly identified common bean lines on the basis of inheritance studies
    77-81.
    Views:
    100

    Common bacterial blight (CBB), caused by Xanthomonas campestris pv. phaseoli (Xcp). is a major disease problem of common bean (Phaseolus vulgaris L.). The inheritance of resistance in Xrl and Xr2 lines to two isolates of Xcp was studied in the F2 and F3 popu­lations from the crosses between these lines and the Masay variety (susceptible to Xcp). Segregation patterns indicated that different single recessive genes presumably in coupling phase linkage determined the resistance to the HUN and EK-1 1 strains of Xcp in both lines. The presence of some minor, modifying genes beside the monogenic genetic background of resistance was also observed. Xrl and Xr2 lines represent valuable new monogenic genetic sources in resistance breeding to CBB.

  • General defense system in the plant kingdom III.
    45-54.
    Views:
    153

    Our observations regarding the symptoms not fitting into, significantly differing from the hypersensitive defense system, which we noticed during the judgment of several plant species, symptoms provoked on several million plants have constituted a unified entity. They have provided evidence for the existence of a different plant defense system. We called this so far unknown basic response of plants to biotic effects as general defense system. This system defends them from the attack of numerous microbe species in the environment.

    The evolutionary intermediate phase between the general and the specific, the two defense systems is the susceptible host—pathogen relation. The vertical resistance system of plants escaping from the susceptible host—pathogen relation, based on specific hypersensitive reaction also suggested the existence of a more original, general defense system and the susceptible host—pathogen relation developed as a result of the collapse of that system.

    The evolutionary relation of the two defense systems is proved by the only recessive inheritance of the older general defense system and in the majority of cases dominant hereditary course of the specific defense system. In our experiences, the modifying genes of the recessive general defense system, in most cases, are behind the specific defense systems, which are known to have monogenic dominant hereditary course and react with hypersensitive tissue destruction. This seemingly striking genetic fact is explained by the following: the general defense system less dependent on environmental effects regulates much faster pathophysiological reaction than the specific resistance genes strongly dependant on environmental effects coding dominant hypersensitive reaction.

    The general and specific defense reactions, the processes excluding the microbes attacking plants with compacting of cell growth and tissue destruction, which mean two opposite strategies, building on and regulating each other constitute the entity of resistance to plant disease.

  • Review of the molecular background of self-incompatibility in rosaceous fruit trees
    7-18.
    Views:
    184

    This review gives a presentation of the gametophytic self-incompatibility system in the roscaeous fruit trees. Studies to discover the pistil (S-ribonucleases) and pollen-part components (F-box molecules) are summarized and models for the self-incompatibility reactions as well as their molecular background are discussed. We describe how mutations within the S-RNase or F-box genes can contribute to the transition from self-incompatibility to the self-compatible phenotype in many fruit tree crops. The current state of the arts is compared to the information obtained in other plant species possessing similar incompatibility system.

  • Ripening related processes in strawberry, a nonclimacteric fruit: a short overview
    105-109.
    Views:
    183

    Fruits are essential part of the human diet: they provide vitamins, minerals, antioxidants to the mankind. Physiologically they can be divided into two groups-climacteric and nonclimacteric - depending if they display any respiratory peak and dramatic increase in ethylene biosynthesis or do not. Ethylene is a gaseous hormone playing a very important role in several physiological processes in plants. While climacteric fruits, like apples, bananas, tomatoes, peaches, apricots show increased ethylene biosynthesis and dramatic respiratory peak during their ripening, nonclimacteric fruits, like strawberries, grapes, citrus do not.

    The most widely used fruits for studying nonclimacteric ripening are strawberries: several papers are focusing on the identification and characterization of ripening related genes from this plant. Therefore here we attempt to summarize the most important advances in strawberry fruit development, and ripening.

  • Transformation of tobacco plants with virEl gene derived from Agrobacterium tumefaciens pTiA6 and its effect on crown gall tumor formation
    53-56.
    Views:
    135

    The VirEl protein plays a key role in the transport of VirE2 protein from the bacterium to the plant cell during crown gall tumor induction by Agrobacterium. The virEl gene of A. tutnefaciens pTiA6 was cloned into the plant transformation vector pTd33 yielding pTd93virEl that was introduced into A. tuniefaciens EHA101 and used for tobacco transformation. The presence of the foreign DNA in the putative transgenic plants was confirmed by PCR analysis. Nine of the 41 transformed plants formed only small tumors following infection with the wild-type A. vitis octopine strain AB3. This property was inherited into the T1 generation. The expression of virEl gene in TI plants was demonstrated by Northern blot analysis.

     

  • Optimization of RNA isolation from stone fruits at different ripening stages
    101-104.
    Views:
    183

    This study was conducted to select the most appropriate RNA isolation method that can be used successfully in case of stone fruits. The changing pattern of gene expression during the ripening process of stone fruits may elucidate the molecular background of several phenotypical or phytochemical alterations present among different genotypes. Our laboratory aims to study the expression of genes encoding for enzymes that catalyze crucial steps in the flavonoid biosynthesis pathway. RNA isolation from fruit mesocarp is a challanging task due to high levels of sugars and polyphenolics accumulating during fruit development. Therefore, at first, the optimal techniques eligible for RNA isolation from fruit tissues at different ripening stages must be selected. Our study compares three different RNA isolation protocols and describes their potential applicability according to different fruit species and ripening stages.

  • Changing of carbohydrates by inoculation of Pseudomonas savastanoi pv. phaseolicola oil bean lines with different resistance
    82-85.
    Views:
    135

    The Pseudomonas savastanoi pv. phaseolicola (PS) is one of the most significant stressors of bean (Phaseolus vulgaris L.). Chemical and agrotechnical treatments have minor importance, so breeding has great part in the protection against this pathogen. Most of the cultivars are susceptible to PS. The genetic background of resistance in the plant is a complex system. Leaf resistance is a monogenic system, but there are some modifier genes. The pathogen species can be divided into different races.

    To understand the functioning of this resistance gene, experiments were carried out using bean varieties with different genotypes and near isogenic lines of bean. Eight lines were tested. Our main objective was to test bean lines with PS with high virulence.

    The experiment was made in greenhouse and on field. The virulent bacterium strain has been isolated in Hungary.

    The changes of carbohydrates were tested after infection. In homeostasis the level of carbohydrates (especially glucose and fructose) were higher in susceptible lines. In case of artificial and natural infection the decrease of glucose were more significant in susceptible lines than in resistant lines. In the leaf samples from systemic chlorosis the level of this carbohydrate increased.

    These changes are connected with the level of resistance, but more experiments are needed to verify this assumption.

  • Test of the utility of apple retrotransposon insertion patterns for molecular identification of 'Jonathan' somatic mutants
    7-10.
    Views:
    168

    Up until today, apple sport mutants proved to be indistinguishable from each other and their progenitors at the molecular level using random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) marker techniques. This is not surprising, since the genomes of these somatic mutants differ only in one or a few small regions that affect economically important characteristics, such as improved fruit colour, size, or flavour. In most cases, these genome differences are probably caused by retrotransposons which are able to convert their RNA transcripts to DNA with reverse transcriptase enzyme prior to reinsertion, but unable to leave the genome and infect other cells. Retrotransposon insertions can alter the expression of other genes and/or the structure of encoded proteins. The sequence-specific amplified polymorphism (S-SAP) technique is capable of revealing the genetic distribution of retrotransposable elements over the whole genome. The present study used this approach to try to characterize and distinguish 'Jonathan' somatic mutants via fingerprinting, which is an unsolved problem.

  • Transmethylation and the general defense reaction of plants
    35-40.
    Views:
    160

    Plant breeding for resistance, namely building specific resistance genes into cultivated plants to ensure resistance against certain pathogen species, is a several-decade-long practice. While looking for purposes of failures appearing during the cultivation of varieties created in this way, a plant feature that ensures non-specific reactions against effects which evoke biotic stress attracted our attention. We named this plant defense form the general defense reaction. The general defense reaction is a fundamental attribute of the plant kingdom, fulfils the role of plant immune system and manifests itself in cell enlargement and cell division. Plants with a high level general defense reaction endure abiotic stresses as well.

    In studying the biochemical background of the interaction of the general defense reaction and transmethylation, we found that transmethylation has important role in warding off both biotic and abiotic stresses. According to our observations, plants possessing high level general defense system are suitable for thorough examination of the process and plant physiological role of transmethylation. Biochemical studies also strengthened our observation, which has been taken on the basis of phenotype, that the general defense system can not be ignored during future plant breeding.

  • The Effects of Some Parameters on Agrobacterium-Mediated Transformation in Muskmelon
    46-49.
    Views:
    168

    Some parameters involved in Agrobacterium-mediated transformation in muskmelon Hales best (HBS) were studied. Cotyledon explants excised from 3.5-day-old seedlings were co-cultivated with Agrobacterium tumefaciens harbouring binary vectors which contained GUS and BAR genes. After co-cultivation on a low pH medium, explants were transferred to selective medium, with higher pH, containing Claforan and Finale. The medium was changed every two weeks till shoots were induced. All shoots rooted on MS medium supplemented with 0.3 mg/L IBA. These parameters combined as a whole led to successful transformation. The expression of the introduced gene construct was confirmed by GUS staining of shoot segments.

     

  • Study of genetic resources for Powdery mildew resistance by biochemical and physiological parameters on peaches and nectarines in Romania
    57-61.
    Views:
    119

    During 1997-2002, studies on the physiological and biochemical changes due to powdery mildew attack in peach and nectarine cultivars and hybrids belonging to different classes of resistance had been performed at the Research Station for Fruit Tree Growing (RSFTG) Baneasa Bucharest, located in the southern part of Romania. The study was based on disease assessments in the field and on other diagnosis criteria.

    The southern part of Romania has favourable ecological conditions for growing peach and nectarine but trees have been attacked by various pathogens such as Sphaerotheca pannosa (Wallr.: Fr.) Lev. var. persicae Woronichin fungus for a long time. The presence of the pathogen causes important changes in the quantity and quality of fruits and affects the metabolism of trees.

    This study was focused on several physiological and biochemical parameters such as photosynthesis and respiration intensity along with catalase activity; and changes in some biochemical compounds such as free, total and linked water content, dry matter, nitrogen and protein content, tannin levels. The aim was to find possible correlation among the above parameters and the biotic stress induced by the powdery mildew fungus calculated as attack degree (AD%).

    Results showed that photosynthesis diminished significantly in the case of the attacked phenotypes, the respiration was more intense in the infected cultivars and catalase proved to be less intense in the affected plants. The total water content significantly increased in contrast to the dry matter and tannin contents, which greatly reduced in the case of resistant cultivars such as 'Victoria', Vectared 7', 'KB 11-40'. The total nitrogen and protein levels showed less influence on resistance to powdery mildew on all cultivars. All genetic material found resistant to powdery mildew is currently used in peach and nectarine breeding programs in Romania.

    Further studies focused on isolation and characterization of resistance genes for powdery mildew resistance will be done in the future based on data collected during several years.

  • Impact of foliar fungi on dogroses
    23-30.
    Views:
    180

    Wild roses of the section Caninae, commonly known as dogroses, have been described as more disease tolerant than ornamental roses and could therefore become valuable for breeding improved rose cultivars. Two fields with dogroses, one with plants obtained by open pollination in wild populations, and one with plants obtained from intra- and interspecific crosses, were evaluated for blackspot, powdery mildew, rust and leafspots in the autumn of 2005. Symptoms of the different fungi on different dogrose species were carefully evaluated in a microscope and documented by photography. Interestingly, almost no symptoms of powdery mildew were found in either field, although the fungus infected wild roses of a different section in a field closeby. Surprisingly few symptoms were found also of blackspot, and they differed considerably from those found on ornamental cultivars, indicating a lower susceptibility in dogroses. The most important fungal disease in 2005 was rust, followed by leafspot symptoms. The latter were apparently caused by Sphaceloma rosarum and Septoria rosae which can be properly discriminated only in a microscope. The investigated dogrose species and their progeny groups varied significantly in disease susceptibility and in the appearance of encountered symptoms but there was no evidence of major resistance genes, except possibly in Rosa rubiginosa which did not show any symptoms of Septoria. In 2006, a subset of the plant material in Field 1 was evaluated to check for consistency between the years. Leafspots had overtaken rust as the most important disease but results were otherwise very similar to those of 2005.

  • Recent findings of the tree fruit self-incompatibility studies
    7-15.
    Views:
    177

    This review endeavours to collect all recent and substantial contributions to the quickly deepening fields of tree fruit self-incompatibility studies and hence updating previously published reviews. Studies carried out to discover the molecular basis of gametophytic self-incompatibility are summarized and a newly described model for the solanaceous plants is also outlined. We describe recent findings in all economically important fruit tree crops involving apple, European pear, sweet and sour cherries, almond, Japanese plum, sloe, Japanese apricot, European apricot and peach. Additional DNA sequences are now available for both the pistil and pollen component genes in several species and their molecular, evolutionary or economic implications are discussed in the light of the fruit setting behaviour.