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Short Life Cycle (short + life_cycle)
Selected AbstractsRapid evolution in crop-weed hybrids under artificial selection for divergent life historiesEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 2 2009Lesley G. Campbell Abstract When species hybridize, offspring typically exhibit reduced fitness and maladapted phenotypes. This situation has biosafety implications regarding the unintended spread of novel transgenes, and risk assessments of crop-wild hybrids often assume that poorly adapted hybrid progeny will not evolve adaptive phenotypes. We explored the evolutionary potential of early generation hybrids using nontransgenic wild and cultivated radish (Raphanus raphanistrum, Raphanus sativus) as a model system. We imposed four generations of selection for two weedy traits , early flowering or large size , and measured responses in a common garden in Michigan, USA. Under selection for early flowering, hybrids evolved to flower as early as wild lineages, which changed little. These early-flowering hybrids also recovered wild-type pollen fertility, suggesting a genetic correlation that could accelerate the loss of crop traits when a short life cycle is advantageous. Under selection for large size at reproduction, hybrids evolved longer leaves faster than wild lineages, a potentially advantageous phenotype under longer growing seasons. Although early generation hybrid offspring have reduced fitness, our findings provide novel support for rapid adaptation in crop-wild hybrid populations. Biosafety risk assessment programs should consider the possibility of rapid evolution of weedy traits from early generations of seemingly unfit crop-wild hybrids. [source] Phytotoxicity assay for seed production using Brassica rapa L.INTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 4 2010David Olszyk Abstract Although pesticide drift can affect crop yield adversely, current plant testing protocols emphasize only the potential impacts on vegetative plant growth. The present study was conducted to determine whether a plant species with a short life cycle, such as Brassica rapa L. Wisconsin Fast Plants®, can be used to indicate potential effects on seed production of herbicides applied at relatively low levels (e.g., low field application rates [FAR]). The effects of ,0.1,×,FAR of aminopyralid, cloransulam, glyphosate, primisulfuron, or sulfometuron applied 14 d after emergence (DAE), were evaluated for B. rapa grown in mineral soil in pots under greenhouse conditions. Effects were expressed as the effective concentration of the herbicide producing a 25% reduction in a response (EC25) based on nonlinear regression. Brassica rapa seed dry weight was reduced by sulfometuron at an EC25 of 0.00014,×,a field application rate (FAR) of 53,g active ingredient (a.i.) ha,1, primisulfuron at 0.008 (experiment 1) or 0.0050 (experiment 2),×,FAR of 40,g,a.i.,ha,1, cloransulam at 0.022,×,FAR of 18,g,a.i.,ha,1, glyphosate at 0.0399,×,FAR of 834,g,a.i.,ha,1, and by aminopyralid at 0.005,×,FAR of 123,g,a.i.,ha,1, but only for 1 of 2 experiments. Reduced seed production occurred at less than the FAR that reduced shoot dry weight with sulfometuron and primisulfuron, whereas neither aminopyralid, cloransulam, nor glyphosate affected shoot dry weight. A short life cycle form of B. rapa could be used to indicate reduced seed production with plants grown only 1 week longer (,35,DAE) than as the current vegetative vigor test for nontarget herbicide effects on plants. Integr Environ Assess Manag 2010;6:725,734. © 2010 SETAC [source] PROPOSAL OF ECTOCARPUS SILICULOSUS (ECTOCARPALES, PHAEOPHYCEAE) AS A MODEL ORGANISM FOR BROWN ALGAL GENETICS AND GENOMICS,JOURNAL OF PHYCOLOGY, Issue 6 2004Akira F. Peters The emergence of model organisms that permit the application of a powerful combination of genomic and genetic approaches has been a major factor underlying the advances that have been made in the past decade in dissecting the molecular basis of a wide range of biological processes. However, the phylogenetic distance separating marine macroalgae from these model organisms, which are mostly from the animal, fungi, and higher plant lineages, limits the latters' applicability to problems specific to macroalgal biology. There is therefore a pressing need to develop similar models for the macroalgae. Here we describe a survey of potential model brown algae in which particular attention was paid to characteristics associated with a strong potential for genomic and genetic analysis, such as a small nuclear genome size, sexuality, and a short life cycle. Flow cytometry of nuclei isolated from zoids showed that species from the Ectocarpales possess smaller haploid genomes (127,290 Mbp) than current models among the Laminariales (580,720 Mbp) and Fucales (1095,1271 Mbp). Species of the Ectocarpales may complete their life histories in as little as 6 weeks in laboratory culture and are amenable to genetic analyses. Based on this study, we propose Ectocarpus siliculosus (Dillwyn) Lyngbye as an optimal choice for a general model organism for the molecular genetics of the brown algae. [source] The biology and ecology of lotic rotifers and gastrotrichsFRESHWATER BIOLOGY, Issue 1 2000Claudia Ricci Summary 1The occurrence of Rotifera and Gastrotricha in the meiobenthos of lotic habitats is reviewed. About 150 rotifer and 30 gastrotrich species are reported in such habitats worldwide. 2The two phyla share some morphological and biological features that might account for their presence in the meiofauna. Small-size, a soft and elongate body, adhesive glands on the posterior body end, movement through cilia, relatively short life cycles, parthenogenesis and dormant stages are common characteristics. 3Most species of both taxa inhabiting the superficial sediments in streams and rivers may move downward into the hyporheos in response to both biotic (predation) and abiotic (spates, erosion, desiccation) disturbances. [source] INFLUENCE OF ANTHROPOGENIC POLLUTION ON MACROPHYTOBENTHOS OF THE AVACHA BAY (SOUTHEAST KAMCHATKA, RUSSIA)JOURNAL OF PHYCOLOGY, Issue 2000N.G. Klotchkova Most industrial and agricultural enterprises of the Kamchatsky district are situated along the coast of the Avacha Bay and its river drainage. Intensive water pollution resulted in extreme deterioration of the bay's ecology. The destruction of macrophytobenthos under the influence of pollution was investigated. Materials were regularly collected at the same sampling sites in different seasons of the year from 1988 up to 1999. Analysis of our data allowed us to determine directions of long-term changes of species composition and macrophytobenthos structure, speed of degradation of different types of vegetational communities and reasons for all these processes. The Avacha Bay's flora consisted of more than 160 species up to 1970s, including species belonged to 104 genera, 47 families, 23 orders, 3 divisions (30 Chlorophyta, 48 Phaeophyta, 82 Rhodophyta). Flora of the internal part of the bay differed from that of the bay's mouth and consisted of 143 and 146 species, respectively. Presently, the whole flora of the bay (internal part+ throat) includes only 94 species. Along the urban coast 18 poly- and mesosaprobious species are found only. They are characterized by small sizes, low productivity and short life cycles. Most of them are ephemeral with a primitive morphology. The responsive reaction of algae to pollution resulted in decreases in size and weight of the thalli, and appearance of anomalies of development. Laminaria bongardiana was used as a bioindicator. The changes of weight and sizes of its plants allow us to determine degree of the pollution in different parts of the coast of the Avacha Bay. [source] | ||||||||||