Thigmomorphogenesis: Ethylene evolution and its role in the changes observed in mechanically perturbed bean plants

Mechanical perturbations, in the form of either rubbing or wounding, cause ethylene evolution from bean internodes ( Phaseolus vulgaris L. cv. Cherokee Wax). This evolution begins 45 to 60 min after perturbation or wounding and peaks about 2 h later. Maximal thigmomorphogenesis occurs if internodes are perturbed when they are 10 mm or less in length. Maximal ethylene evolution, however, occurs in longer internodes. When one internode is perturbed, ethylene evolution is not observed from other internodes even though they respond thigmomorphogenetically by exhibiting decreased elongation. Ethylene evolution is apparently a result of increased 1-amino-cyclopropane-1-carboxylic acid (ACC) production after perturbation. Inhibitors of ACC and ethylene synthesis block increased radial growth but not reduced elongation. Ethylene may therefore be only one of several factors causing thigmomorphogenesis.     

Evolution of ethylene by sulphur dust addition

Kidney-bean plants ( Phaseolus vulgaris L. cv. Contender) were dusted with sulphur 25 days after germination. The amount of ethylene evolution was measured in shoots (with attached leaves) and roots from plants in several stages of development. The growth of shoots and roots was also measured, and the flowering time observed. The ethylene evolution was associated with precise morphogenic stages. The amounts of ethylene produced from sulphur treated plants, compared with that evolved from control plants, showed two stages of stimulation in shoots, one preceding full bloom and one preceding fruit-set. Inhibition of ethylene evolution due to sulphur dust occurred in roots before initiation of floral primordia and before full bloom. The treatment with sulphur dust seemed to increase the number of leaves per plant, but only in the vegetative stage. Likewise, the earliness of flowering was enhanced. The effects of elemental sulphur dust treatments on ethylene evolution may be attributed to a slow oxidation of elemental sulphur in air producing SO²; this SO² greatly enhances ethylene evolution from leaf tissues.     

Effect of Cytokinin 4-PU-30 on the Lipid Composition of Water Stressed Bean Plants

Fourteen days-old bean plants, grown on sand with Knop's nutrient solution were subjected to water stress (three days without irrigation). The stress led to a decrease in almost all lipid classes except phospholipids in the primary leaves. The content of palmitic acid increased, and that of the linolenic acid decreased. An increase of hexadecenoic acid in phospholipids was also observed. Rewatering for 24 h led to the recovery of the stressed plants including that of the photosynthetic apparatus, but the changes in the lipid composition were insignificant. The spraying of the plants before and after the water stress with 5 × 10-6 M solution of the phenylurea cytokinin 4-PU-30 alleviated negative effect of water stress on the lipid membrane composition permitting the plants to resist the harmful environment. This revised version was published online in July 2006 with corrections to the Cover Date.     

菜豆病虫害及其防治

对危害菜豆的病虫害进行了研究,根据病虫害的种类及发生规律,提出了相应的防治措施.     

Alterations in Endogenous Levels of Gibberellin-like Substances during Germination of Phaseolus vulgaris Seeds

The endogenous gibberellin-like substances were determined in mature dry and germinating bean seeds, Phaseolus vulgaris L. cv. Alabaster. Methanol extracts were partitioned against ethyl acetate and butanol at neutral and acid pH. Each phase was individually chromatographed on a silica gel column. The gibberellin activity was measured with the Tan-ginbozu dwarf rice micro-drop bioassay. Each extract was tested in two dilutions. Extracts from dry seeds showed the highest gibberellin activity, largely attributable to ethyl acetate-soluble substances. The activity was considerably reduced in extracts from seeds imbibed for 1 day. Gibberellin-like substances soluble in butanol appeared in extracts from seeds soaked for 1 or more days.     

On the Relationship between the Activity of O-Methyltransferase and the Content of Lignin in Various Organs of Kidney Bean

The activity of O-methyltransferase (OMT) and the content of lignin in various organs of 12- to 14-day-old seedlings of kidney bean (Phaseolus vulgarisL., cv. Saksa) were determined. The epicotyl and hypocotyl were characterized by the highest OMT activity, and the leaves, by the lowest OMT activity. At the same time, the lignin content gradually increased in the following order: leaves < epicotyl < hypocotyl < roots. Thus, in kidney bean seedlings, there is no direct relationship between the OMT activity and the lignin content. It is suggested that lignin biosynthesis is limited by biosynthetic steps other than O-methylation of caffeic and 5-hydroxyferulic acids affected by OMT.     

A comparison of methods for inoculating bean plants with Elsinoë phaseoli and some factors affecting infection

Bean (Phaseolus vulgaris) leaves were inoculated with a conidial suspension of Elsinoe phaseoli by spraying, by applying a 10 μl drop, by a cotton wool technique or by using a camel hair brush. Spray application resulted in a uniform distribution of lesions over the leaf surface and gave consistent levels of infection between repetitions. Drop application allowed good control of the amount of inoculum applied. Although brush or cotton wool techniques gave high levels of infection it was not possible to control the amount of inoculum. Only immature tissues were susceptible to infection. Five cultivars were inoculated with two isolates and disease was scored on the basis of numbers of lesions and lesion type (scab severity). The small white cvs PAN 181 and Teebus were the most resistant; lesions were small and generally fewer than on the large-seeded red speckled sugar bean cvs Umlazi and Umvoti. The value of the different inoculation techniques in studies on bean scab is discussed.     

Initial Stages of Morphogenetic Changes in Detached Cotyledons,Hypocotyls, and Leaves of Kidney Beans and Eggplants under Salinity Conditions

The effects of salinity on the morphogenesis of various organs of kidney bean (Phaseolus vulgaris L.) and eggplant (Solanum melongena L.) plants grown in nosterile culture and of explants from these organs grown in vitro were studied. Salt stress was produced by adding NaCl (0.5 and 1.0%) to water or the Murashige and Skoog nutrient medium. Salt stress suppressed rhizogenesis, particularly profoundly in the salt-sensitive beans. Callus cultures obtained from different organs differed in their salt tolerance, which was evaluated from the callus growth. Under salinity conditions, homologous structures of the two crops differed markedly in survival and regeneration. Different organs and corresponding explants of one and the same plant differed in the threshold sensitivity to salinity, which indicates the organ-specificity of salt resistance.     

Inheritance of Anthracnose Resistance in the Common Bean Differential Cultivar G 2333 and Identification of a New Molecular Marker Linked to the Co-42 gene

The inheritance of anthracnose resistance of the common bean ( Phaseolus vulgaris L.) differential cultivar G 2333 to Colletotrichum lindemuthianum races 73 and 89 was studied in crosses with the susceptible cultivar Rudá. The segregation ratios of 15 : 1 in the F₂ and 3 : 1 in the backcrosses to Rudá indicate that for each of the races tested there are two independent resistance loci in G 2333. A random amplified polymorphic DNA (RAPD) molecular marker (OPH18_1200C) linked in resistance to race 73 was identified in a BC₃F_2:3 population derived from crosses between Rudá and G 2333. A RAPD molecular marker OPAS13_950C, previously identified as linked to gene Co-4² , was also amplified in this population. Co-segregation analyses showed that these two markers are located at 5.6 (OPH18_1200C) and 11.2 (OPAS13_950C) cM of the Co-4² gene. These markers were not present in BC₁F_2:3 plants resistant to race 89 indicating that this population carries a different resistance gene. DNA amplification of BC₁F_2:3 plants with RAPD molecular marker OPAB_450C, previously identified as linked to gene Co-5 , indicated that this gene is present in this population.     

Resistance of stored bean varieties to Acanthoscelides obtectus (Coleoptera: Bruchidae)

During bean seed storage, yield can be lost due to infestations of Acanthoscelides obtectus Say, the bean weevil. The use of resistant varieties has shown promising results in fighting these insects, reducing infestation levels and eliminating chemical residues from the beans. The expression of resistance to A. obtectus in bean varieties is frequently attributed to the presence of phytohemagglutinins, protease inhibitors and alpha-amylase, and especially to variants of the protein arcelin, which reduce the larval viability of these insects. To evaluate the effect of bean seed storage time on the resistance expression of bean varieties to A. obtectus , tests with seeds of three ages (freshly-harvested, 4-month-old, and 8-month-old) were conducted in the laboratory, using four commercial varieties: Carioca Pitoco, Ipa 6, Porrillo 70, ônix; four improved varieties containing arcelin protein: Arc.1, Arc.2, Arc. 3, Arc.4; and three wild varieties also containing arcelin protein: Arc.1S, Arc.3S, and Arc. 5S. The Arc.5S, Arc.1S, and Arc.2 varieties expressed high antibiosis levels against the weevil; Arc.1 and Arcs expressed the same mechanism, but at lower levels. The occurrence of oviposition non-preference was also observed in Arc.5S and Arc.1S. The Arc.3 and Arc. 4 varieties expressed low feeding non-preference levels against A. obtectus. The expression of resistance in arcelin-bearing, wild or improved varieties was affected during the storage of seeds, and was high under some parameters but low in others. The results showed that addition of chemical resistance factors such as protein arcelin via genetic breeding may be beneficial in improving the performance of bean crops.     

Production of Transgenic Kidney Bean Shoots by Electroporation of Intact Cells

We obtained transformed bean shoots by electroporation of intact bean cells with the plasmid pDPG165 containing bar gene conferring herbicide resistance to plants. Transformed shoots were selected from electroporated callus on herbicide containing media. Data of molecular analysis (PCR and Southern blotting) confirmed the insertion of bar gene in the genome of herbicide resistant shoots. Detailed procedures for obtaining regenerative bean callus, optimization of electroporation of intact cells and transgenic shoots are given.