SelectingRhizobium phaseoli strains for use with beans (Phaseolus vulgaris L.) in Kenya: Infectiveness and tolerance of acidity and aluminium

Forty strains ofRhizobium phaseoli, isolated from Kenyan soils, were tested for infectiveness on common bean (Phaseolus vulgaris L.). 28 strains were infective and a cultivar × Rhizobium interaction was observed. 48 strains were screened for tolerance of acidity and Al in liquid culture. Assessment of visible turbidity after 14 days indicated 34 strains tolerant of pH 4.5 but none tolerant of pH 3.5. No strain was tolerant of 50 M Al at pH 5.5. Three strains were tolerant of 20 M Al at pH 5.5 and 10 M Al at pH 4.5. Screening on a solid medium identified strains tolerant of 20 and 50 M Al at pH 5.5 and 4.5 which were sensitive to these treatments in liquid culture. Those strains tolerant to 20 M Al at pH 4.5 and 5.5 in liquid culture were correctly identified on the solid medium.     

Enhanced bactericidal activity of platelet β-lysin forE. coli in the presence of membrane perturbation

Inhibition by sodium chloride of the growth of 19 strains ofLegionella pneumophila and of 10 strains of otherLegionella spp. was studied. Results from growth in buffered -ketoglutarate cysteine yeast extract (BAYE) broth containing 0 to 2.0% sodium chloride indicated that 15/19 laboratory strains ofL. pneumophila were capable of growing in 1.0% to 1.5% sodium chloride, whereas 4 strains ofL. pneumophila and 10 strains of 6 other species were not.L. micdadei andL. longebeachae were the most inhibited in BAYE broth, growing only in concentrations of 0.5% sodium chloride. These in vitro studies indicate thatL. micdadei andL. longbeachae might be differentiated from other species by their low tolerance to salt in BAYE broth, and thatL. pneumophila may be more tolerant to salt concentrations found in brackish water environments.     

Interspecific differences in aluminium tolerance in relation to root cation-exchange capacity

Genotypic differences in aluminium (Al) tolerance hold considerable promise in overcoming an important limitation to plant growth in acid soils. Little is known, however, about the biochemical basis of such differences. Extracellular properties, particularly low root cation-exchange capacity (CEC), have been associated with Al tolerance, since roots of low CEC adsorb less Al than do those of high CEC. A solution culture study was conducted in which 12 plant species (monocots and dicots) were grown in solution culture of low ionic strength (ca 2 mM) for 8 d at four Al concentrations (0, 16, 28 and 55 M). The species differed significantly in Al tolerance as shown by differences in root length. Root length relative to that of the same species grown in the absence of Al varied from 6 to 117% at 16 M Al, and from 6 to 75% at 28 M Al. Species tolerance of Al was not closely associated with differences in root CEC. Although in some species Al sensitivity was associated with high adsorption of Al during a 10- or 40-min exposure to Al (expressed on a fresh mass or root length basis), this was not a good predictor of Al tolerance across all species studied.     

Are chemical barriers necessary for evolution of butterfly-plant associations?

Summary The association between heliconiine butterflies and Passion flower vines is composed of three or more subassociations, in which each Heliconius species group feeds on a different Passiflora subgenus. The relationships are consistent with the adaptive zone hypothesis of Ehrlich and Raven, which would suggest that (1) species of the subgenus Plectostemma proliferated as a result of chemical barriers to herbivory, which created a herbivore-free adaptive zone in which speciation and diversification took place, and (2) species of the H. erato-charitonia group overcame these barriers and entered a competitor-free adaptive zone, in which they proliferated and speciated with those plants as hosts. The hypothesis that plant secondary chemicals were responsible for creating such barriers to herbivory was tested using heliconiine species as bioassays, in which reduced growth rates indicated presence of chemical barriers to feeding. Contrary to expectation, plants of the subgenus Plectostemma showed little or no chemical defense against any species of heliconiine caterpillar. In contrast many plants of the primitive subgenus Granadilla possessed significant chemical barriers against herbivory by heliconiine larvae, excepting those species in the H. numata-melpomene species group. I concluded that chemical barriers to feeding were not responsible for proliferation and diversification in the subgenus Plectostemma, nor did chemicals create a competitor-free adaptive zone in which the H. erato-charitonia species-group could proliferate and speciate. Chemical barriers may have been important in the evolution of the subgenus Granadilla-heliconiine association. I suggest that plant allelochemics are only one of many possible barriers to herbivory which can help create adaptive zones for plants and their herbivores, and that the patterns of butterfly foodplant specialization discussed by Ehrlich and Raven (1964) are not necessarily the result of biochemical adaptation and counteradaptation.     

Screening maize inbred lines for tolerance to low-P stress condition

Genotype screening and selection for tolerance to low-phosphorus stress conditions is an important strategy for the development of cultivars growing on soils low in available P. This study was conducted to adjust an existing screening methodology which provides stable, diffusion-limited low-P concentrations for use with maize, and then use the modified methodology to select maize inbreds tolerant to low-P stress during the vegetative stage of development. Low and high-P concentration levels were established that provided a reproducible and diffusion-controlled availability of P to the plants at concentrations of 8–10 M and 40–50 M, respectively, of culture medium solution P at the time of transplanting. The procedure was also effective in providing low concentrations of P during the period of plant growth. The sand-alumina culture medium was used to screen 20 maize inbreds known to be efficient in P uptake or accumulation and/or tolerant to aluminum toxicity. The inbreds B37, Oh40B, NY821, Pa36, and MS1334 were selected as tolerant to low-P and WH, H99, H84, Pa32, and W37A were selected as intolerant to low-P in sand-alumina medium.     

The β-tubulin gene family evolution in theDrosophila montium subgroup of themelanogaster species group

The 1-, 2-, and 3-tubulin genes have been mapped by in situ hybridization on the polytene chromosomes of 11 selected species (15 strains) belonging to theDrosophila montium subgroup. Although the hybridization pattern among the strains of the same species does not differ, this pattern is significantly different among the species. The -tubulin genes in themontium subgroup seem to be organized in a cluster, or in a semi-cluster, or are completely dispersed. The clustered arrangement is found in the North-Oriental sibling speciesD. auraria, D. triauraria, andD. quadraria. The semi-clustered arrangement, wherein the 1 and 2 genes are located at the same locus while 3 is at a different one, appears in the South-Oriental speciesD. bicomuta, D. serrata, andD. birchii, as well as in the Afrotropical speciesD. diplacantha andD. seguyi. The complete separation of the genes is observed in the Indian speciesD. kikkawai andD. jambulina and in the Afrotropical speciesD. vulcana. Based on the above results, a possible mode of evolution of the -tubulin genes in the montium subgroup is attempted. In addition, phylogenetic relationships among themontium species are discussed. Correspondence to: Z.G. Scouras     

Copper and cobalt uptake byHaumaniastrum species

Summary Herbarium specimens of the genus Haumaniastrum (mainly from Shaba Province Zaïre) were analysed for copper and cobalt.H. homblei showed elevated copper levels and indicated its tolerance to mineralized ground.H. robertii (previously-known as a copper flower) showed the expected high copper concentrations, but contained abnormally high concentrations of cobalt (av. 4304 g/g dry weight) far exceeding those of copper. This species has the highest cobalt content of any phanerogam and its distribution may be controlled by cobalt rather than by copper. re]19761220     

Glucose tolerant and thermophilic β-glucosidases from yeasts

Summary Forty-eight yeast strains belonging to the genera Candida, Debaryomyces, Kluyveromyces and Pichia (obtained from the ARS Culture Collection, Peoria, IL) were screened for production of extracellular glucose tolerant and thermophilic -glucosidase activity using p-nitrophenyl--D-glucoside as substrate. Enzymes from 15 yeast strains showed very high glucose tolerance (<50 % inhibition at 30 %, w/v glucose). The optimal temperatures and pH for these -glucosidase activities varied from 30 to 65°C and pH 4.5 to 6.5. The -glucosidases from all these yeast strains hydrolyzed cellobiose.Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Lack of effect of toxic aluminium concentrations on nitrogen fixation by nodulatedStylosanthes species

Summary Effects of three solution aluminium concentrations (0, 25, and 100M) on nitrogen fixation by well-nodulated plants ofStylosanthes hamata, Stylosanthes humilis andStylosanthes scabra are reported. Plants were inoculated with Rhizobium CB756 and grown for 21 days in an aluminium-free nutrient solution at pH 5.3 before imposition of the aluminium treatments.Nitrogen fixation was measured both by the increase in total nitrogen content of the plants and acetylene reduction in roots of plants harvested at 10 and 20 days after imposition of the aluminium treatments. Solution aluminium concentrations as high as 100M, had no detrimental effect on nitrogen fixation in any species.     

Antagonistic interaction between auxins and the growth regulator NC 9634

The synthetic growth regulator NC 9634, [(3-phenyl-1,2,4-thiadiazol-5-yl)thio] acetic acid (NC 9634) was shown to have anti-auxin properties in bioassay tests. The inhibition of wheat coleoptile extension growth by concentrations of NC9634 up to 260 M was completely overcome by 60 M IAA, 50 M NAA or 50 M 2,4-D. In cress root tests 2.6 × 10^–7 M NC 9634 stimulated root elongation and relieved the growth inhibiting effect of 2,4-D. Extension growth of intact apple shoots was inhibited by NAA, which proved lethal at concentrations above 6.25 × 10^–4 M. NC 9634 applied in combination with the NAA, reduced this growth inhibiting effect and prevented death of shoots sprayed with high auxin concentrations.     

Comparative structure of the gas-vacuoles of blue-green algae

Summary An investigation was made of 5 species of blue-green algae reported to contain gas-vacuoles. All organisms were grown and harvested under standard conditions. Gas-vacuoles were characterised as reddish structures which are destroyed by applying pressure. Using a simple direct preparation technique gascylinders were observed with the transmission electron microscope in gas-vacuolate cells. Gas-vacuoles were present in the strains of Anabaena flos-aquae, Gloeotrichia echinulata and Oscillatoria agardhii studied and absent from Microcystis aeruginosa and Nostoc linckia. The reddish, refractile central area of N. linckia and M. aeruginosa cells was tentatively identified as nucleoplasm. Gas-vacuoles are collections of gas-cylinders 70 m wide, which in A. flos-aquae and G. echinulata are clearly bounded by photosynthetic lamellae and associated with -granules. The presence of bounding photosynthetic lamellae in these species is suggested as a causal factor of the unusual optical properties of their gas-vacuoles. The range of lengths of gas-cylinders in G. echinulata and O. agardhii is from 100 m to 500 m and in A. flos-aquae it is from 100 m to 1300 m. The percentage of cell volume occupied by gas-vacuoles was estimated by direct measurement. In A. flos-aquae and G. echinulata it was 22%. In O. agardhii gas-cylinders were not clearly associated with photosynthetic lamellae and -granules and occupied 39% of cell volume. Gascylinder membranes showed reasonable preservation in KMnO₄ and excellent preservation in OsO₄. The widths of membranes after treatment with these two fixatives was 3 m and 2 m respectively.     

Variability in the 11S globulin fraction of seed storage proteins ofHelianthus (Asteraceae)

The seed storage globulins from sixHelianthus and four hybrids were studied using mono and bidimensional gel SDS electrophoresis (+ 2 mercaptoethanol). The polypeptide composition of each subunit was determined. Different pairs are specifically expressed according to the species studied. Three typical patterns were discriminated. All the studied species exhibit five subunits: two of them are expressed in all the species (₁₁ and ₂₂). The subunit corresponding to the ₁₁ pair is present inH. petiolaris and in the three populations ofH. annuus studied. The _2b2 pair is common toH. annuus andH. argophyllus. H. petiolaris presents two specific _2a2 and ₄₄ pairs andH. annuus a specific ₃₃ pair. InH. argophyllus _{11 33} or ₄₄ are never observed but are replaced by ₁₃ and ₃₁ pairs. Some globulins, poorly represented, are of forms but present chains of higher molecular weights (in the range 54–56 kDa). Expressing variations in the banding patterns between these species by the use of a similarity index reveals complete identity between the three populations ofH. annuus. Identity between the twoH. petiolaris studied is also observed.H. annuus andH. argophyllus appear to be closer to each other thanH. petiolaris concerning the seed storage globulins.     

The effect of nitrate concentration in a flowing solution system on growth and nitrate uptake of twoPlantago species

Summary Juvenile plants ofPlantago lanceolata andP. major ssp.major were grown in a flowing solution system at 7.5 mM or 9.5 M NO₃. The parameters investigated were: RGR, shoot weight percentage, leaf length, length of main root axis, shoot concentrations of major ions and organic N, and the specific uptake rate for NO₃. At 9.5 M NO₃ growth ofP. major was not hampered, whereas shoot growth and leaf length ofP. lanceolata were reduced. The NO₃ concentration ofP. lanceolata decreased more than that ofP. major. The different performances of the species at 9.5 M NO₃ were associated with different specific uptake rates. In both treatments the root system ofP. major was shorter than that ofP. lanceolata. P. lanceolata accumulated more NO₃ in the leaves. The performance of thePlantago species is discussed in relation to the availability of nutrients in their habitats.Grassland Species Research Group. Publication no. 37.     

Seedling responses of three Australian tree species to toxic concentrations of zinc in solution culture

A frequently desired outcome when rehabilitating Zn toxic sites in Australia is to establish a self-sustaining native ecosystem. Hence, it is important to understand the tolerance of Australian native plants to high concentrations of Zn. Very little is known about the responses of Australian native plants, and trees in particular, to toxic concentrations of Zn. Acacia holosericea, Eucalyptus camaldulensis and Melaleuca leucadendra plants were grown in dilute solution culture for 10 weeks. The seedlings (42 days old) were exposed to six Zn treatments viz., 0.5, 5, 10, 25, 50 and 100 M. The order of tolerance to toxic concentrations of Zn was E. camaldulensis> A. holosericea> M. leucadendra, the critical external concentrations being approximately 20, 12 and 1.5 M, respectively. Tissue Zn concentrations increased as solution Zn increased for all species. Root tissue concentrations were higher than shoot tissue concentrations at all solution Zn concentrations. The critical tissue Zn concentrations were approximately 85 and 110 g g^–1 DM for M. leucadendra, 115 and 155 g g^–1 DM for A. holosericea and 415 and 370 g g^–1 DM for E. camaldulensis for the youngest fully expanded leaf and total shoots, respectively. The results from this paper provide the first comprehensive combination of growth responses, critical external concentrations, critical tissue concentrations and plant toxicity symptoms for three important Australian genera, viz., Eucalyptus, Acacia and Melaleuca, for use in the rehabilitation of potentially Zn toxic sites.     

Tolerance and Resistance in Gastropod Mollusks Hydrobia ulvaeand H. ventrosafrom the White Sea to Abiotic Environmental Factors

Tolerance to salinity changes and resistance to desiccation, fresh water, and freezing were studied in two hydrobiid species from the White Sea, Hydrobia ulvae(Pennant) and H. ventrosaMontagu. It was shown that H. ventrosahas a greater tolerance to low salinities in the range of 6–10 but is less tolerant to high salinities (35–45). The interspecies differences in low salinity tolerance persisted after the acclimation of snails to 20, 16, and 12. A comparison of survival in fresh water and under desiccation conditions suggests that H. ulvaeis more resistant to these factors. In fresh water, LT₅₀was 30 and 60 days for H. ventrosaand H. ulvae, respectively. Under desiccation conditions, LT₅₀was 6 and 25 days for H. ventrosaand H. ulvae, respectively. At subzero temperatures, H. ventrosawas shown to be a superior survivor. Within the same species of mud snail, the detrimental effect of freezing depended on the salinity: survival decreased with decreasing salinity. These data suggest significant differences in the mechanisms of resistance and tolerance to abiotic environmental factors between the two species. Despite the partial overlapping of their ecological niches, the interspecies differences may play an important role in the distribution and spatial structure dynamics of coexisting populations of these species in the White Sea region.     

SelectingRhizobium phaseoli strains for use with beans (Phaseolus vulgaris L.) in Kenya: Tolerance of high temperature and antibiotic resistance

Forty one strains ofRhizobium phaseoli were screened for the ability to multiply at high temperatures on yeast extract-mannitol agar. Most strains were tolerant of 30°C, eight strains were tolerant of 45°C and two of 47°C although the rate of multiplication was reduced at 45–47°C. The high temperature-tolerant strains were isolated from Kenyan soils and were fast-growing. Seven of the eight strains tolerant of 45–47°C lost their infectiveness after incubation at high temperature but four strains tolerant of 40°C remained infective after incubation at that temperature.Thirty six strains were resistant to 200 g ml^–1 streptomycin sulphate and 29 strains to 200 g ml^–1 spectinomycin dihydrochloride. Eight strains were resistant to both antibiotics each at 200 g ml^–1. Two of the double-labelled antibiotic-resistant mutants lost their infectiveness onPhaseolus vulgaris. The response to acidity was unaltered and two of the mutants showed a decrease in temperature tolerance. The doublelabelled mutants were recoverable from two Kenyan soils.     

Between-family variation in sex ratio in the Trinidad (T-30) strain of Aedes aegypti (L.) indicating differences in sensitivity to the meiotic drive gene M D

Sex ratio in the Trinidad (T-30) strain of Aedes aegypti has remained constant at around 43% during seventeen years of laboratory culture. The divergence from 50% is due to meiotic drive by the M ^D gene on the Y chromosome. The driving Y chromosome gives a much more distorted sex ratio (mean = 5.7%) when coupled with the highly sensitive X chromosomes from strain 64. This was demonstrated in all of 98 families tested, indicating that all or most of the Y chromosomes in T-30 carry the M ^D gene. Consequently the low level of sex ratio distortion in T-30 must be due to resistance to M ^D.Crosses made within T-30 demonstrated wide differences in sex ratio between families, depending on the sensitivity of the male parent's X chromosome to M ^D. However, sex ratios were not continuously variable but fell within fairly discrete categories. Thus, X chromosomes could be classified according to the modal sex ratios associated with them: m ^s3 (12.5%), m ^s2 (32.5%), m ^s1 (40%), m ^r1 (47.5%) m ^r2 (57.5%).The different sex ratio categories were more discrete in the families of sib matings than from random matings, suggesting the possibility of background modification of what is essentially a balanced polymorphism. Evidence is presented suggesting that the polymorphism could be due to interaction at two loci. A further X variant, m ^s4 (<10%) characterised strain 64 but was absent from T-30.A comparison of fertility between the different sex ratio categories in T-30 established that sex ratio distortion was not caused by differential mortality after fertilisation.     

DNA base composition within the genusScenedesmus (Chlorophyta)

The DNA base compositions of 60 strains ofScenedesmus were determined and found to be a valuable indicator for the differentiation within this genus (except for the very closely related species of the subsect.Desmodesmus). The range for allScenedesmus species was 49.9–69.3 mol% GC for nuclear DNA and 36.8–39.9 mol% GC for chloroplast DNA. The separation of the genusTetradesmus cannot be verified by GC values, becauseS. obliquus andS. (Tetradesmus)wisconsinensis have a similar GC content.S. (Chlorella)ultrasquamata, S. costato-granulatus (sect.Costato-granulati) andS. lunatus are separated clearly from all other species of the genus because of their high GC content.     

Effects of external phosphorus supply on internal phosphorus concentration and the initiation,growth and exudation of cluster roots in Hakea prostrata R.Br.

The response of internal phosphorus concentration, cluster-root initiation, and growth and carboxylate exudation to different external P supplies was investigated in Hakea prostrata R.Br. using a split-root design. After removal of most of the taproot, equal amounts of laterals were allowed to grow in two separate pots fastened together at the top, so that the separate root halves could be exposed to different conditions. Plants were grown for 10 weeks in this system; one root half was supplied with 1 M P while the other halves were supplied with 0, 1, 25 or 75 M P. Higher concentrations of P supplied to one root half significantly increased the P concentration of those roots and in the shoots. The P concentrations in root halves supplied with 1 M P were invariably low, regardless of the P concentration supplied to the other root half. Cluster root initiation was completely suppressed on root halves supplied with 25 or 75 M P, whereas it continued on the other halves supplied with 1 M P indicating that cluster-root initiation was regulated by local root P concentration. Cluster-root growth (dry mass increment) on root halves supplied with 1 M P was significantly reduced when the other half was either deprived of P or supplied with 25 or 75 M P. Cluster-root growth was favoured by a low shoot P status at a root P supply that was adequate for increased growth of roots and shoots without increased tissue P concentrations. The differences in cluster-root growth on root halves with the same P supply suggest that decreased cluster-root growth was systemically regulated. Carboxylate-exudation rates from cluster roots on root halves supplied with 1 M P were the same, whether the other root half was supplied with 1, 25 or 75 M P, but were approximately 30 times faster when the other half was deprived of P. Estimates of root P-uptake rates suggest a rather limited capacity for down-regulating P uptake when phosphate was readily available.     

Meiotic analysis ofElymus caucasicus,E. longearistatus,and their interspecific hybrids with twenty-threeElymus species (Triticeae,Poaceae)

Interspecific hybridizations were carried out between the two tetraploidsElymus caucasicus andE. longearistatus, and 23 tetraploids and hexaploids ofElymus containing SH, SY, SYH, and SYW genomes and representing various geographical regions. Meiotic pairing was studied in the two target species and their hybrids. It is concluded from this study that (i) interspecific hybridization is fairly easy to perform although strong reproductive barriers exist between the species; (ii)Elymus caucasicus andE. longearistatus are allotetraploids, and share the diverged SY genomes; (iii) the divergence of SY genomes is correlated with the geographic distance between theElymus spp. studied.