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Population fluctuations of the western tent caterpillar in southwestern British Columbia (2000)

Myers, J. H.

Springer

Population ecology 42 (2000), S. 231-241

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ISSN: 1437-5613

Keywords: Key words Population cycles ; Nucleopolyhedrovirus ; NPV ; Insect quality ; Metapopulation ; Island populations ; Forest tent caterpillars ; Sublethal disease

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Cyclic populations of western tent caterpillars fluctuate with a periodicity of 6–11 years in southwestern British Columbia, Canada. Typically, larval survival is high in early stages of the population increase, begins to decline midway through the increase phase, and is low through several generations of the population decline. Fecundity is generally high in increasing and in peak populations but is also reduced during the population decline. Poor survival and low fecundity for several generations cause the lag in recovery of populations that is necessary for cyclic dynamics. The dynamics of tent caterpillar populations vary among sites, which suggests a metapopulation structure; island populations in the rainshadow of Vancouver Island have more consistent cyclic dynamics than mainland populations in British Columbia. Sudden outbreaks of populations that last a single year suggest that dispersal from source to sink populations may occur late in the phase of population increase. Wellington earlier discussed qualitative variation among tent caterpillar individuals as an aspect of population fluctuations. The variation in caterpillar activity he observed was largely statistically nonsignificant. Recent observations show that the frequency of elongate tents as described by Wellington to characterize active caterpillars varies among populations but does not change in a consistent pattern with population density. The level of infection from nucleopolyhedrovirus (NPV) was high in some populations at peak density but was not associated with all population declines. Sublethal infection can reduce the fecundity of surviving moths, and there is a weak association between viral infection and egg mass size in field populations. The impact of weather in synchronizing or desynchronizing populations is a factor to be investigated further.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/PL00012002

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Continuous callus production and regeneration of garlic (Allium sativum L.) using root segments from shoot tip-derived plantlets (1998)

Myers, J. M. ; Simon, P. W.

Springer

Plant cell reports 17 (1998), S. 726-730

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ISSN: 1432-203X

Keywords: Key words Garlic ; Allium sativum L. ; Root segments ; Regeneration ; Picloram

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Root segments from shoot tip-derived plantlets of the garlic (Allium sativum L.) clones `DDR7099', `PI383819', and `Piacenza' were utilized as an explant source for continuous, friable callus production. The best callus production occurred on root segments initially cultured on medium with 4,5 μm 2,4-dichlorophenoxyacetic acid (2,4-D) for 8 weeks, then subcultured to medium with 4.7 μm 4-amino-3,5,6-trichloropicolinic acid (picloram) +0.49 μm 6-(γ-γ-dimethylallylamino)purine (2iP) for 8 weeks. Embryogenic, friable callus was transferred to liquid medium for 1 month and then transferred to solid regeneration medium for 14 weeks. The best shoot and root regeneration (85.3% and 35.8%, respectively) occurred on 4-month-old calli from the clone `DDR7099'. In all clones, regeneration rate decreased as callus age increased.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002990050473

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Regeneration of garlic callus as affected by clonal variation, plant growth regulators and culture conditions over time (1999)

Myers, J. M. ; Simon, P. W.

Springer

Plant cell reports 19 (1999), S. 32-36

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ISSN: 1432-203X

Keywords: Key words Allium sativum ; Benzyladenine ; Picloram ; Thidiazuron ; 2 ; 4-D ; 2iP

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract A long-term regeneration system for garlic (Allium sativum L.) clones of diverse origin was developed. Callus was initiated on a modified Gamborg's B-5 medium supplemented with 4.5 μM 2,4-D and maintained on the same basal medium with 4.7 μM picloram+0.49 μM 2iP. Regeneration potential of callus after 5, 12 and 16 months on maintenance medium was measured using several plant growth regulator treatments. The 1.4 μM picloram+13.3 μM BA treatment stimulated the highest rate of shoot production. Regeneration rate decreased as callus age increased, but healthy plantlets from callus cultures up to 16-months-old were produced for all clones. Regeneration of long-term garlic callus cultures could be useful for clonal propagation and transformation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002990050706

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Induction of diploid androgenetic and mitotic gynogenetic Nile tilapia (Oreochromis niloticus L.) (1995)

Myers, J. M. ; Penman, D. J. ; Basavaraju, Y. ; [et al.]

Springer

Theoretical and applied genetics 90 (1995), S. 205-210

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ISSN: 1432-2242

Keywords: Androgenesis ; Gynogenesis ; Tilapia Gene bank ; Chromosome manipulation

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Androgenesis is a potentially valuable technique for recovering fish from gene banks composed of cryopreserved sperm, developing inbred lines, and analyzing patterns of inheritance. The procedure for producing diploid organisms whose nuclear DNA is wholly of paternal origin is dependent on: (1) the denucleation of “host” eggs, and (2) the inhibition of the first mitotic division in order to double the haploid sperm chromosome complement following fertilization of host eggs. Denucleation of tilapia (Oreochromis niloticus L.) eggs was carried out using UV irradiation. Treatment durations of 5–8 min (total dose of 450–720 J/m2) produced acceptable yields of viable denucleated eggs [22.9±1.6% (±SE) of controls] as estimated by the survival of haploid androgenetic tilapia to 48 h post-fertilization. Successful mitotic inhibition was accomplished using a heat-shock of 42.5 °C for 3–4 min, applied at 2.5-min intervals from 22.5 to 30 min post-fertilization (mpf). The mean survival of androgenetic diploid fish to yolk-sac absorption for treatment groups varied from 0.4% to 5.3%, relative to the controls. Differences in the suceptibility of eggs from different females to UV irradiation were a significant factor in the overall yield of androgenetic diploids. Paternal effects did not significantly influence the androgenetic yield, suggesting that individual males would not be selected against. For comparative purposes mitotic gynogenetic “mitogyne” diploids were produced from UV-irradiated sperm. Mean survival to yolk-sac absorption varied from 0.5% to 10.64%, relative to controls. Similar optima for androgenetic and gynogenetic induction were found in the period 25–27.5 mpf (minutes post-fertilization). Induction treatments would appear to be operating on the same developmental events in both these techniques, and the results suggest that the UV irradiations used do relatively little damage to the eggs beyond nuclear inactivation. The results indicate that the production of androgenetic O. niloticus is possible on a consistent basis and that the application of this technique may be useful in quantitative and conservation genetics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00222203

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