Control of Postharvest Diseases of Sweet Cherry with Ethanol and Hot Water

Complete inhibition of the germination of spores of Penicillium expansum occurred after 10 s exposure to 40% ethanol or more at ambient temperature, while spores of Botrytis cinerea were completely inhibited by 30% ethanol or more. Mortality of the spores of P. expansum and B. cinerea in heated 10% ethanol was higher than in water at the same temperatures. Immersion of naturally inoculated fruit in 20, 30, 40, or 50% ethanol reduced the decay present after storage for 10 days at 20°C similarly and by approximately 60–85%. Immersion of fruit that had been inoculated with the spores of P. expansum and B. cinerea reduced decay by both pathogens after storage for 30 days at 0°C and 5 days at 20°C when 30% or higher concentrations of ethanol were used. The incidence of decay after immersion in water alone for 30 s at 24, 50, 55, or 60°C was 57.7, 44.7, 46.2, and 35.7%, respectively, while 10% ethanol at these temperatures the decay incidence to 52.2, 33.9, 32.8, or 14.7%, respectively. Water treatments at 50, 55, or 60°C alone were not effective against P. expansum, while their efficacies were significantly increased by the addition of 10% ethanol. The most effective treatment was immersion in 10% ethanol at 60°C. Ethanol treatments at 20, 30, 40, or 50% and water treatments at 55 or 60°C significantly reduced natural fungal populations on the surfaces of fruit in all of the experiments. Addition of 10% ethanol to water significantly increased the efficacy of water in reducing the fungal populations at elevated temperatures. None of these treatments caused surface injuries to the fruit or adversely affected stem colour.     

In vitro shoot tip multiplication of cowpea Vigna unguiculata (L.) walp

Summary Shoot multiplication was induced in cowpea, cv. Georgia-21, from shoot tip explants. Shoot tips, 5 mm long, were isolated from in vitro-grown seedlings and cultured on MS medium containing N⁶-benzyladenine (BA) at 1, 2.5, or 5 mg/liter (4.4, 11.1, or 22.2 μM) or 6-furfurylaminopurine (kinetin) at 1, 2.5, or 5 mg/liter (4.6, 11.6, or 23.2 μM) combined with 2,4-dichlorophenoxyacetic acid (2,4-D) at 0.01, 0.1, or 0.5 mg/liter (0.05, 0.5, or 2.3 μM) or naphthaleneacetic acid (NAA) at 0.01, 0.1, or 0.5 mg/liter (0.05, 0.5, or 2.7 μM). Cultures were maintained at a 12-h photoperiod (40 μmol·m⁻²·s⁻¹) and 23 ± 2° C. Treatments with BA induced greater shoot proliferation than those with kinetin. The highest number of shoots was produced on 5 mg (22.2 μM) BA per liter in combination with NAA or 2,4-D at 0.01 mg/liter (0.05 μM). Callus proliferated from the basal ends of shoot pieces in all treatments. The cultures also formed roots in the presence of kinetin, but not on BA-containing medium. To produce whole plants, the shoots were separated and rooted on 0.1 mg (0.5 μM) NAA per liter. Resulting plants grew normally under greenhouse conditions. Shoot tips provide an excellent explant source for cowpea micropropagation and can be used for callus induction.     

Some Factors Influencing the in vitro Infectivity and Replication of Encephalitozoon cuniculi*

SYNOPSIS. Rabbit Encephalitozoon cuniculi were propagated in vitro using rabbit choroid plexus (RCP) cells. The organisms reached maximum titer and numbers by 15 days. The source and in vitro passage level of RCP cells moderately influenced the sensitivity of the cells to infection. Cells less than 1 week old were significantly less sensitive than older cells. A moderate increase in infectivity for RCP cells was demonstrated with increasing organism passage level in vitro. Rabbit E. cuniculi were not affected by penicillin-streptomycin or gentamicin in the culture medium. The organism survived more than 9 days in buffer at 37 C and least 24 days at 4 and 20 C. Storage at -70 C or in liquid nitrogen was successful for at least 6 months. Encephalitozoon cuniculi survived 60 but not 120 min at 56 C. They were killed after 10 min of autoclaving and by 2% (v/v) Lysol, 10% (v/v) formalin and 70% (v/v) ethyl alcohol. The organisms survived at least 24 h at pH 9 or pH 4 and were not affected by sonication, freezing and thawing, or distilled water but lost significant infectivity after 24 h in CsCl or 40% (w/v) sucrose.     

Relative Heterothallism and Production of Hybrid Perithecia by Auxotrophic Mutants of Glomerella cingulata from Apple

Glomerella cmgulata is a homothallic species but produces a ridge of fertile perithecia at a frontier between certain wild-type strains on agar. To account for the presence or absence of perithecia earlier workers suggested that alleles at A and B loci control the formation of perithecia at mycelial frontiers in + and – strains. We propose that G. cingulata actually demonstrates “relative heterothallism”. Of 7 induced nutritionally deficient mutants (auxotrophs) in 2 wild-type strains from apple, only one methionine (met-1) and one arginine (arg) mutant in only one wild-type strain gave a heavy ridge of perithecia at their junctures. Neither the met-l nor arg mutations have been identified as those in the A or B locus. The perithecia were either homozygous (selfs) for met-1 or arg, or heterozygous (hybrids). Paired met-1 and arg segregants from hybrid perirhecia as well as diauxotrophic strains from met-l or arg mutants also gave hybrids of selfs. Specific nutritional deficiencies in certain wild-type strains which can direct sexuality are not yet known. Genetic studies are now feasible in G. cingulata to define enzymatic factors responsible for pathogenicity.     

Prolonged environmental stress via a two step process selects mutants of Escherichia,Salmonella and Pseudomonas that grow at 54°C

A prolonged incubation of Escherichia, Salmonella or Pseudomonas at 48°C with nalidixic acid selected mutants (T48) able to grow at 48°C. A prolonged incubation at 54°C of the T48 mutants selected mutants (T54) able to grow at 54°C. These mutants were susceptible to the same bacteriophages as the original mesophilic strains. Auxotrophic phenotypes of Escherichia coli and Salmonella typhimurium mesophilic parents were demonstrated by these mutants if they were cultivated on minimal agar with cellobiose at 48°C or 54°C or on a minimal agar with glucose at 37°C. The T48 alleles mapped in the gyrA region of E. coli or S. typhimurium chromosome. In S. typhimurium the T54 alleles, which permit growth at 54°C, were shown by cotransductional analysis to be linked to gyrA.     

Distribution of Mononchoidea (Nematoda: Enoplea) in pasture soils,with description of lotonchus stockdilli n. sp.

Abstract

Across 64 sites 8 species were found, with Clarkus propapillatus at 60 sites, C. composticola at 7, Prionchulus muscorum at 3, Mylonchulus ubis at 7, M. sigmaturus at 1, Cobbonchus australis at 9, lotonchus basidontus at 4, and I. stockdilli n. sp. at 3 sites. Sampling effort varied at the sites and significant annual and management effects have previously been reported on mononchid populations. No clear geographic or soil factor is apparent in the distributions, but more species may occur at sites with higher annual rainfall. lotonchus stockdilli n. sp. is a large (female L = 3.05–5.90 mm), bisexual species with dorsal tooth at the posterior of the sclerite, female tail about 400 μm or 14%, and no cuticular pores in the vulval region.     

Effects of oximecarbamate, organophosphate and benzimidazole nematicides on life cycle stages of root-knot nematodes, Meloidogyne spp.

A study was made of the effects of concentrations of 2 to 32 ppm of oximecarbamate, organophosphate and benzimidazole nematicides on the hatch, larval viability and migration of Meloidogyne javanica, M. incognita and M. hapla and on development of M. javanica in roots. Aldicarb at less than 8 ppm had little effect on hatch and methomyl markedly affected only the hatch of M. hapla. As little as 2 ppm of fenamiphos or thionazin markedly reduced hatch of all three species but less than 8 ppm ethoprophos significantly reduced only the hatch of M. incognita and phorate had little effect on hatch. Benomyl and thiabendazole had no significant effects on hatch. When egg masses of M. incognita were transferred from nematicides which suppressed hatch to water, hatching occurred, but aldicarb, fenamiphos, ethoprophos and thionazin significantly reduced total hatch. None of the nematicides killed larvae of the three species immersed in 16 and 32 ppm solutions of them for 3 days. Aldicarb at 2 ppm reduced migrations of all three species; the effects of methomyl, fenamiphos or thionazin on migration varied according to species, while phorate, ethoprophos, benomyl or thiabendazole had little or no effect on migration. Aldicarb or thionazin at 2 ppm stopped development of M. javanica in roots of tomato seedlings while methomyl, ethoprophos or fenamiphos at 4 ppm reduced development by 60% and at 8 ppm of ethoprophos or fenamiphos or 16 ppm of methomyl, development was stopped. Phorate had little effect on development and benomyl or thiabendazole had no effect. Nematicide concentrations which reduced development prevented the normal orientation of larvae in the roots and reduced or prevented giant cell formation.     

Impact of soil sterilization and irrigation intervals on P and K acquisition by mycorrhizal onion (<Emphasis Type="Italic">Allium cepa</Emphasis>)

Drought is a world-spread problem seriously influencing crop production. Arbuscular mycorrhizal (AM) association and soil microorganisms can help plant growth under water stress condition by improvement of its nutrient and water uptake. In this experiment, onion plants (Allium cepa L. cv. Red Azar Shahr) were inoculated with three AM fungi species (Glomus versiforme, G. intraradices, G. etunicatum) or left un-inoculated as non-mycorrhizal plants, in a sterile or non-sterile sandy loam soil. Plants were irrigated at 7, 9 or 11-day intervals to keep the soil moisture content to field capacity at the irrigation time. Mycorrhizal root colonization decreased (p < 0.05) with an increase in irrigation interval, and the highest root colonization was achieved at 7-day irrigated onions in symbiosis with G. versiforme. Phosphorus content in plant tissue was significantly increased in mycorrhizal than non-mycorrhizal onions. Plants inoculated with G. versiforme at 9-day interval treatment had the highest leaf P content, while the lowest P was observed in non-mycorrhizal plants at all irrigation intervals. Onions inoculated by G. versiforme or G. etunicatum at 9-day irrigation interval had the highest K content. Results revealed that the inoculation of onion plant with G. versiforme or G. etunicatum and increasing irrigation interval up to 9 days, could improve P and K uptake.     

Temporal relationships betweenZea mays,ostrinia nubilalis (Lep.: Pyralidae) and endophyticBeauveria bassiana

The entomopathogenic fungus,Beauveria bassiana (Balsamo) Vuillemin, was applied to whorl-stage (V7) corn,Zea mays L., by foliar application of a granular formulation of corn grits containing conidia or by injection of a conidial suspension. All plants were infested with European corn borer larvae,Ostrinia nubilalis (Hübner), at the V7 (whorl), V12 (late-whorl), or V17 (pretassel) stage of plant development. Plants infested at whorl and late-whorl stages had significantly more European corn borer tunneling than did plants infested at the pretassel stage. The percentage of plants colonized byB. bassiana did not differ significantly among the whorl, late-whorl, and pretassel stages. As the plants matured,B. bassiana was isolated from different plant areas, with the pith more frequently colonized than the leaf collars. Foliar application ofB. bassiana provided immediate suppression ofO. nubilalis in those plants infested at whorl stage. The reduced efficacy ofB. bassiana at the intermediate plant stages relative to efficacy at harvest is discussed. The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

Temperature effects on solute accumulation by Candida utilis

Summary A study was made of the effect of temperature on accumulation of glucosamine and 2-aminoisobutyrate by Candida utilis NCYC 321 grown at 30° C or 10° C. Exponential-phase cells contained greater proportions of C_16:1 and C_18:3 acids, and smaller proportions of C_13:1 and C_18:2 acids, when grown in a defined medium at 10° C compared with 30° C. Cells grown at 30° C or 10° C were able to accumulate extracellular (10 mM) glucosamine and 2-aminoisobutyrate against concentration gradients. 2-Aminoisobutyrate was not metabolised by the cells; glucosamine was accumulated probably as a mixture of glucosamine 1- and 6-phosphates. Rates of accumulation of glucosamine and 2-aminoisobutyrate by cells grown at 30° C or 10° C decreased markedly when the test temperature was decreased from 30° C to 15° C. The rate of accumulation of glucosamine by cells grown at 10° C was considerably lower at each of the test temperatures compared with the corresponding rates for cells grown at 30° C; the rate of accumulation of 2-aminoisobutyrate was much less affected by the temperature at which the cells were grown and then only when measured at temperatures below about 20° C. Apparent K _m values for accumulation of glucosamine by cells grown at 30° C or 10° C decreased considerably when the test temperature was lowered from 20° C to 15° C. The extent of the decrease in K _m value was approximately the same for cells grown at 30° C or 10° C. Apparent K _m values for accumulation of 2-aminoisobutyrate were hardly affected by test temperature. Apparent V _max values for accumulation of glucosamine or 2-aminoisobutyrate were much lower when measured at 15° C than at 30° C. When measured at 30° C, apparent V _max values for accumulation of either solute were slightly lower with cells grown at 10° C compared with cells grown at 30° C; when measured at 15° C, the values were slightly greater with cells grown at 10° C. Net accumulation of glucosamine, at 30° C or 20° C, by cells grown at 30° C or 10° C ceased after 4–6 h. Cells grown at either temperature continued to accumulate 2-aminoisobutyrate at 30° C or 20° C for at least 12 h. The rate of efflux of glucosamine by cells grown at 30° C was slower when measured at 20° C compared with 30° C. With cells grown at 10° C, the rate of efflux at 30° C was slower than with cells grown at 30° C; when measured at 20° C, the rates were about equal. The temperature at which the cells were grown did not affect the ability of d-glucose, d-mannose or d-ribose to compete with d-glucosamine, or with the ability of l-alanine to compete with 2-aminoisobutyrate, when tested at 30° C or 20° C. Cells grown 30° C or 10° C had very similar ATP contents. The results are discussed in relation to the effect of temperature on the rate of solute accumulation by micro-organisms.Abbreviation AIB 2-Aminoisobutyrate     

Micropropagation of 21 species of Mexican cacti by axillary proliferation

Summary We have developed micropropagation systems for 21 species of Mexican cacti using explants from seedlings germinatedin vitro or shoot segments of juvenile 2–3-yr-old greenhouse plants. The species propagated belong to the generaAstrophytum, Cephalocereus, Coryphantha, Echinocactus, Echinocereus, Echinofossulocactus, Ferocactus, Mammillaria, Nyctocereus, andStenocactus. Multiple shoot formation from areoles was achieved in Murashige and Skoog (MS) medium supplemented with either 1 or 2 mg N⁶-benzyladenine (BA) per 1 (4.44 or 8.87 μM) or BA at 1 or 2 mg/l plus naphthaleneacetic acid at 0.1 or 1 mg/l (0.54 or 5.37 μM). The requirements of growth regulators for optimal shoot proliferation, the velocity of the response, and the number of buds produced by explant were different among the genera and species studied. Rooting of the shoots generatedin vitro was achieved in MS medium supplemented with indoleacetic acid at 0.5–1 mg/l (2.85–5.71 μM) or indolebutyric acid at 0.5–1 mg/l (2.46–4.90 μM). Finally, 70–95% of the rooted plants transferred to potting medium survived.     

Biodegradation of Petroleum Hydrocarbons in Seawater at Low Temperatures (0–5 °C) and Bacterial Communities Associated with Degradation

In this study biodegradation of hydrocarbons in thin oil films was investigated in seawater at low temperatures, 0 and 5 °C. Heterotrophic (HM) or oil-degrading (ODM) microorganisms enriched at the two temperatures showed 16S rRNA sequence similarities to several bacteria of Arctic or Antarctic origin. Biodegradation experiments were conducted with a crude mineral oil immobilized as thin films on hydrophobic Fluortex adsorbents in nutrient-enriched or sterile seawater. Chemical and respirometric analysis of hydrocarbon depletion showed that naphthalene and other small aromatic hydrocarbons (HCs) were primarily biodegraded after dissolution to the water phase, while biodegradation of larger polyaromatic hydrocarbons (PAH) and C₁₀–C₃₆ n-alkanes, including n-hexadecane, was associated primarily with the oil films. Biodegradation of PAH and n-alkanes was significant at both 0 and 5°C, but was decreased for several compounds at the lower temperature. n-Hexadecane biodegradation at the two temperatures was comparable at the end of the experiments, but was delayed at 0°C. Investigations of bacterial communities in seawater and on adsorbents by PCR amplification of 16S rRNA gene fragments and DGGE analysis indicated that predominant bacteria in the seawater gradually adhered to the oil-coated adsorbents during biodegradation at both temperatures. Sequence analysis of most DGGE bands aligned to members of the phyla Proteobacteria (Gammaproteobacteria) or Bacteroidetes. Most sequences from experiments at 0°C revealed affiliations to members of Arctic or Antarctic consortia, while no such homology was detected for sequences from degradation experiment run at 5°C. In conclusion, marine microbial communities from cold seawater have potentials for oil film HC degradation at temperatures ≤5°C, and psychrotrophic or psychrophilic bacteria may play an important role during oil HC biodegradation in seawater close to freezing point.     

HU Participates in Expression of a Specific Set of Genes Required for Growth and Survival at Acidic pH in <Emphasis Type="Italic">Escherichia coli</Emphasis>

The major histone-like Escherichia coli protein, HU, is composed of alpha and beta subunits respectively encoded by hupA and hupB in Escherichia coli. A mutant deficient in both hupA and hupB grew at a slightly slower rate than the wild type at pH 7.5. Growth of the mutant diminished with a decrease in pH, and no growth was observed at pH 4.6. Mutants of either hupA or hupB grew at all pH levels tested. The arginine-dependent survival at pH 2.5 was diminished approximately 60-fold by the deletion of both hupA and hupB, whereas the survival was slightly affected by the deletion of either hupA or hupB. The mRNA levels of adiA and adiC, which respectively encode arginine decarboxylase and arginine/agmatine antiporter, were low in the mutant deficient in both hupA and hupB. The deletion of both hupA and hupB had little effect on survival at pH 2.5 in the presence of glutamate or lysine, and expression of the genes for glutamate and lysine decarboxylases was not impaired by the deletion of the HU genes. These results suggest that HU regulates expression of the specific set of genes required for growth and survival in acidic environments.     

Viability of dried vegetative cells and the formation and germination of reproductive structures inPithophora œdogonia, Cladophora glomerata andRhizoclonium hieroglyphicum under water stress

All dried vegetative cells ofPithophora œdogonia died within 1 h, while those ofCladophora glomerata andRhizoclonium hieroglyphicum retain viability to some extent for 1 and 8 d, respectively, under similar storage conditions. The viability of dried vegetative cells of eitherC. glomerata orR. hieroglyphicum decreased more or less equally when stored either at 20 °C. in light or dark or at 12 °C in dark, but was lost rapidly and drastically when stored at 0 °C in dark. Both dried and wet akinetes ofP. œdogonia were equally more viable when stored at 20 °C in dark than in light, but they lost germination ability when stored either at 12 or 0 °C in dark; this might be either due to loss of viability or dormancy induction at low temperatures. The water stress imposed by growing vegetative filaments either on highly agarized media, in NaCl-supplemented liquid media or in media undergoing progressive air-drying to complete dryness did not induce, but reduced akinete formation inP. œdogonia, decreased zoosporangium formation inC. glomerata andR. hieroglyphicum, decreased or totally suppressed akinete germination inP. œdogonia and zoospore germination inC. glomerata andR. hieroglyphicum. Akinetes ofP. œdogonia formed under water stress were equally viable, while zoosporangia ofC. glomerata andR. hieroglyphicum formed under water stress were comparatively less viable than those formed without any water stress. Akinete germination inP. œdogonia and zoospore germination inC. glomerata andR. hieroglyphicum were comparatively more sensitive to water stress than the formation of akinetes and zoosporangia. The akinete germination inP. œdogonia was more sensitive to water stress than zoospore germination inC. glomerata andR. hieroglyphicum and it might be either due to their large size, thick wall or dense content.     

Changes in fungi and mycotoxins in pearl millet under controlled storage conditions

Pearl millet is increasingly being grown as a premium-value grain for the recreational wildlife and poultry industries in the southern US. We conducted three experiments to assess grain mold development in storage conditions typically encountered in the region of production. Variables included production year, temperature, relative humidity, atmosphere, and grain moisture content. In the first experiment, grain was stored for 9 weeks at 20 or 25°C and maintained at 86% or 91% relative humidity (r.h.). In the second experiment, grain was stored for 9 weeks at 20 or 25°C in either air (aerobic) or N₂ (anaerobic), and maintained at 100% r.h. In the third experiment, high-moisture grain was stored for 3 weeks at 20 or 25°C and maintained at 100% r.h. Grain was sampled at weekly intervals and plated to determine changes in fungal frequency. Fungi isolated included Fusarium chlamydosporum (19% of grain), Curvularia spp. (14%), F. semitectum (16%), Alternaria spp. (9%), Aspergillus flavus (8%), “Helminthosporium”-type spp. (6%), and F. moniliforme sensu lato (3%). Year of grain production significantly affected isolation frequency of fungi. Isolation frequencies from low-moisture grain were rarely affected by temperature, relative humidity, or atmosphere treatments, but was affected by storage duration for some fungi. Changes in isolation of toxigenic fungi occurred in high-moisture grain. Isolation frequency of F. chlamydosporum increased in grain stored at 86% and 91% r.h. Incidence of A. flavus increased in high-moisture grain treatments, particularly at 25°C. Incidence of deoxynivalenol was not affected by storage treatment. Low concentrations of nivalenol were detected in most grain incubated at 100% r.h. Zearalenone was detected only when grain moisture content was 20–22%. Aflatoxin contamination averaged 174 ng g⁻¹ over all treatments, and increased up to 798 ng g⁻¹ in high-moisture grain at stored at 25°C.     

Epidemiology of Cladosporium allii and Cladosporium allii-cepae, leaf blotch pathogens of leek and onion.

Conidia of Cladosporium allii and C. allii-cepae germinated over the temperature range 2–30°C on agar with optimal responses at 15–20°C (C. allii) and 20°C (C. allii-cepae). Conidia of both fungi germinated in water and at c. 100% relative humidity (r.h.) but not at lower humidities on leaf and glass slide surfaces. Germination was more rapid when spores were applied dry to agar or leaves than when applied in water or nutrient solution. More lesions developed when conidia of C. allii-cepae were deposited dry on onion leaf discs or leaf surfaces than when they were applied suspended in water. Conidia of both fungi required 18–20 h at c. 100% r.h. to germinate and infect when applied dry to leaves. Damaging the leaves or the addition of nutrients to the leaf surface increased the incidence of infection by C. allii-cepae compared to controls. Inoculated onion bait plants placed out-of-doors developed infection after at least 17 h at c. 100% r.h. or with leaf wetness. Similar conditions were necessary for infection of bait plants exposed in onion and leek crops infected by C. allii-cepae and C. allii respectively. Disease development and spread of infection occurred at different rates over the same period in two different cultivars of leeks, with spore concentrations increasing in proportion to disease. Spore numbers in the air fell considerably when infected leeks were ploughed under.     

Effects of delaying fungicide treatment of wounded potatoes on the incidence of Fusarium dry rot in store

Potato tubers artificially inoculated with Fusarium solani var. coeruleum or F. sulphureum 3 months after harvest were uniformly wounded and held at 5, 10 or 15°C for up to 21 days before immersion in fungicide suspensions. Holding tubers for 14 days at 15°C (curing conditions) or at 5°C did not alter the incidence of dry rot subsequently developing on tubers stored at 10°C, and holding tubers for up to 21 days at 15°C slightly increased disease caused by both pathogens. Thiabendazole, imazalil and prochloraz applied to tubers immediately after wounding almost completely prevented dry rot. Treatment after 3 days was less effective and the amount of disease increased with further delay; fungicides were more effective on tubers held at 5°C than at 10 or 15°C before treatment and storage, and efficacy of the fungicide was decreased by increasing the amount of inoculum on tubers. Wounds became less susceptible to infection by F. solani var. coeruleum and F. sulphureum when tubers were held at 15°C before inoculation, and the incidence of rots was decreased by 70–80% by delaying inoculation for 7 days. Treating tubers with dichlorophen immediately after wounding slightly increased the disease. The effects of fungicide treatment, curing conditions and wound healing are discussed.     

The time rate and mechanism of chromosome elimination in Hordeum hybrids

Seed development at 20±1° C in continuous light was studied during the first 5 days after pollination in diploid Hordeum vulgare, diploid H. bulbosum and the cross, H. vulgare x H. bulbosum, where H. bulbosum chromosomes were eliminated. Developing seeds were fixed and stained at known intervals after pollination and the embryo sac contents dissected out for cytological examination. — In all cases, the pattern of development was similar to that previously described for the Triticeae. After intraspecific pollination, the rate of endosperm and embryo development was significantly faster in H. vulgare than in H. bulbosum. In hybrid tissues, the rate was intermediate, but often much nearer to that of H. vulgare at first. Elimination of H. bulbosum chromosomes occurred only during endosperm and embryo mitoses. Usually, 0–3 chromosomes were lost at any one division but up to 7 were lost at some. Elimination, which occurred as early as zygotic anaphase, was nearly or quite complete in all dividing cells in both embryo and endosperm after 5 days. The mean number of chromosomes lost per nucleus per nuclear cycle was low at first but rose rapidly and stayed high for about a day in each tissue before falling quickly. The rate of elimination in each tissue was maximal when that tissue first synthesized significant amounts of new cytoplasm (day 2 after pollination in the endosperm and day 3 in the embryo). At mitosis, chromosomes being eliminated differed from others only in failing to congress at metaphase or to reach a pole at anaphase or both. — It is noted that in several widely different examples where either haploids are produced when only hybrids are expected, or where chromosomes of one species are preferentially eliminated from hybrid cells, nucleolar activity was suppressed in chromosomes of the genome which was selectively or preferentially eliminated. Consequently, it is suggested that chromosome elimination in Hordeum hybrids may be caused by a disturbed control of protein metablism in hybrid seeds and perhaps H. bulbosum chromosomes are selectively eliminated because they are less efficient than H. vulgare chromosomes at forming normal attachments to spindle protein.     

Temperature-dependent phosphate solubilization by cold- and pH-tolerant species of Aspergillus isolated from Himalayan soil

Ten species of Aspergillus isolated from soil samples collected from different locations in the Indian Himalayan region have been studied for their growth requirements and tricalcium phosphate solubilization at different temperatures. The Aspergillus species could grow at low temperature and tolerated a wide range of pH. Phosphate solubilization by various Aspergillus species ranged between 374 μg/ml (A. candidus) to 1394 μg/ml (A. niger) at 28°C, 33 μg/ml (A. fumigatus) to 2354 μg/ml (A. niger) at 21°C, 93 μg/ml (A. fumigatus) to 1452 μg/ml (A. niger) at 14°C, and 21 μg/ml (A. wentii) to 83 μg/ml (A. niger) at 9°C. At 21 and 28°C, phosphate solubilization showed a decrease within 4 weeks of incubation, whereas at 9°C and 14°C, it continued further up to 6 weeks of incubation. In general, phosphate solubilization by different Aspergillus species was recorded at a maximum of 28°C or 21°C; biomass production was favored at 21°C or 14°C. Conversely, A. nidulans and A. sydowii exhibited maximum phosphate solubilization at 14°C and produced maximum biomass at 21°C. Data suggest that suboptimal conditions (higher or lower temperature) for fungal growth and biomass production were optimal for the production of metabolites involved in phosphate solubilization. Significant negative correlations were obtained between pH and phosphate solubilization for eight species at 28°C, for seven at 21°C, and for nine at 14°C. Extracellular phosphatase activity was exhibited only in case of A. niger, whreas intracellular phosphatase activity was detected in all species, the maximum being in A. niger. Statistically significant positive or negative correlations were obtained between phosphate solubilization and other parameters in most cases at different temperatures.     

Diapause and cold tolerance in Asian species of the parasitoid Leptopilina (Hymenoptera: Figitidae)

Diapause and cold tolerance are essential for temperate insects to pass the winter, with the mechanisms controlling these two traits varying considerably among insects. In the present study, diapause and cold tolerance are compared among three Leptopilina species: Leptopilina japonica Novkovi? & Kimura, Leptopilina victoriae Nordlander and Leptopilina ryukyuensis Novkovi? & Kimura, all larval parasitoids of frugivorous drosophilid flies, with the aim of understanding their climatic adaptations. The first species is divided into the temperate (Leptopilina japonica japonica) and subtropical subspecies (Leptopilina japonica formosana), and the latter two species are distributed in the tropical and subtropical regions. The temperate subspecies of L. japonica enters prepupal diapause at low temperatures (15 or 18 °C), irrespective of photoperiod, and some individuals enter diapause when exposed to 0 °C for 1 or 2 day(s) or when placed at low humidity. Leptopilina victoriae also shows signs of diapause initiation at 15 °C, although L. ryukyuensis and L. j. formosana from the subtropical regions do not. Preimaginal viability at low temperature (13, 14 or 15 °C) is usually lower in L. victoriae from the tropical regions compared with L. japonica or L. ryukyuensis from the temperate or subtropical regions. Diapausing prepupae of the temperate subspecies appear to be cold tolerant. However, the cold tolerance of nondiapausing prepupae, pupae and adult females varies little among the tropical, subtropical and temperate species or subspecies, and adult males of the temperate subspecies of L. japonica are less cold tolerant than those of the tropical or subtropical species or subspecies. Cold tolerance may be unnecessary, except for diapausing individuals of the temperate species, because nondiapausing individuals appear in warmer seasons.