Identification and characterization of simple sequence repeat (SSR) markers from Fragaria×ananassa expressed sequences

The availability of expressed sequence data derived from gene discovery programmes enables mining for simple sequence repeats (SSRs), providing useful genetic markers for crop improvement. These markers are inexpensive, require minimal labour to produce and can frequently be associated with functionally annotated genes. This study reports on the development and characterization of expressed sequence tag (EST)–SSR markers in the cultivated strawberry, Fragaria×ananassa. Fourteen primer pairs were assessed for polymorphism in 13 F.×ananassa genotypes. The markers show reliable amplification and considerable polymorphism, demonstrating the utility of EST–SSRs for genetic analysis of commercial strawberry germplasm.     

Know Thy Enemy: Experience Affects Elk Translocation Success in Risky Landscapes

ABSTRACT To maximize success, reintroduction programs generally select predator-free release areas having high habitat quality. Past studies provide little insight into recovery efforts where multiple, potentially novel, mortality hazards occur. The ability of translocated animals to cope with novel environments can be affected by both pre- and postrelease experiences with habitat and mortality risks. We experimentally released elk (Cervus elaphus) having different background experiences into an area where predators and hunters were prevalent and habitat quality varied. Using a competing risks approach, we predicted the postrelease survival of individuals and their fidelity to release areas as a function of animal source and postrelease encounters with forage resources and areas used by wolves (Canis lupus) or humans. Mortality patterns were consistent with prerelease exposure to mortality risks but not habitat differences among source areas. Wolf predation, poaching, and legal Native hunting were equivalent in magnitude and accounted for the majority of elk mortalities. Familiarity with either wolves or hunters prior to release yielded first-year survival rates 1.9-2.2 times greater than observed for animals naive to both risks. These 2 primary sources of mortality traded off temporally as well as spatially given the proximity of roads, which wolves avoided. The prevalence of forage resources in release areas increased fidelity to release sites but coincided with higher mortality risk during the critical first year, potentially setting an ecological trap for animals naïve to local risks. Translocated individuals largely mediated their respective vulnerabilities over time, showing second-year survival rates equivalent to resident elk. In addition to using source populations that are able to adjust to mortality risks in release areas, spatial and temporal variation in mortality risks might be exploited when planning releases to increase the success of translocations into risky landscapes. (JOURNAL OF WILDLIFE MANAGEMENT 71(2):541–554; 2007)     

Early Release of ABA from Cell Walls During Rose Petal Protoplast Isolation

During the isolation of rose petal protoplasts, two successivetransient abscisic acid (ABA) accumulations were detected whendigest medium and tissue slices were assayed simultaneously,using polyclonal antibodies raised against (+)-ABA. Late accumulation,occurring after more than 1 h of incubation, was observed, whetherenzymes were present or not, in a hyperosmotic medium. Veryearly accumulation, occurring at a maximum of 15 min after thebeginning of incubation, was observed only in the presence ofcellulolytic and pectinolytic enzymes. The ABA level could beincreased by the addition of tetcyclacis, an inhibitor of mono-oxygenaseknown to delay ABA oxidation. The need for cell wall digestingenzymes to observe this first ABA increase suggested that itwas due to a release from the cell wall. Analysis by radioimmunoassay(RIA) and high performance liquid chromatography (HPLC) showedthat ABA and another non-acidic immunoreactive compound werereleased from purified cell walls by the same enzymes. Key words: ABA, cell wall, protoplast, rose petal     

Atmospheric Ozone Interacts with Stress Ethylene Formation by Plants to Cause Visible Plant Injury

Ozone toxicity was studied in peas, beans, and tobacco (BelB and Bel W3). These experiments showed that ozone toxicitywas related to the rates of ethylene biosynthesis. Sensitivityto ozone was reduced if ethylene biosynthesis was inhibitedafter treatment with aminoethoxyvinylglycine (AVG). Similarly,plants that were able to reduce or prevent stress ethylene formationwere less sensitive after both short- and long-term exposureto ozone. Plants conditioned by longer exposures to ozone havelow rates of ethylene formation and this may be why brief ozoneexposures may be more phytotoxic than prolonged fumigations. Key words: Nicotiana tabacum, Phaseolus vulgaris, Pisum sativum, lipid peroxidation, peas, Pinto beans, tobacco     

Starch Gel Electrophoresis of Plant NADH-Nitrate Reductase and Nitrite Reductase

Isozymes of both nitrate reductase (NR) and nitrite reductase(NiR) have been found in plant tissues, mainly after partialpurification. We have used starch gel electrophoresis to examineboth NR and NiR in crude extracts. Only one NR and one NiR enzymewere found in wheat tissues and no difference in mobilitiescould be detected between root and leaf enzymes. It was confirmedthat some tissues of corn have two NiR isozymes.     

The influence of weather and microclimate on Dalbulus maidis (Homoptera: Cicadellidae) flight activity and the incidence of diseases within maize and bean monocultures and bicultures in tropical America

Mixed cropping systems in tropical America have been shown to be less prone than monocultures to damage from pathogens carried by insects. This finding formed the basis for a series of experiments conducted in Costa Rica to evaluate the hypothesis that mixed cropping systems create a physical environment that influences vector movement and consequently the spread of leafhopper-borne pathogens. The principle finding of the study is that both the mixture of plants and planting density have little influence on the spread of pathogens by Dalbulus maidis, an oligophagus leafhopper which prefers maize, within maize and bean single and mixed cropping systems. Leafhopper flight activity proved similar for high and low density monocultures and bicultures. The number of leafhoppers immigrating to and emigrating from a field appears dependent on the size of the field, not the density of maize plants. Single and mixed crops with the same density of maize plants were equally prone to damage by pathogens carried by leafhoppers. The lower percentage infection in high density than in low density maize treatments resulted from fewer vectors per plant in the former.