RESUMEN
AIMS: To employ the genome shuffling technique for improving the phenotype of a biocontrol control agent of the genus Streptomyces. METHODS AND RESULTS: Two rounds of genome shuffling (GS) were carried out with Streptomyces melanosporofaciens EF-76, a geldanamycin producer. Six fusants that showed optimized in vitro antagonistic activity against Streptomyces scabies or Phytophthora infestans, two important pathogens of potato crops, were selected. All selected fusants retained the capacity to produce geldanamycin, but none overproduced this antibiotic. The higher antagonism ability appeared to result from a diversification of secreted metabolites. Seven or eight metabolites were detected in the HPLC profiles of parental strains, whereas 12-15 were detected in fusant strains. Biocontrol assays revealed that four of six fusants protected tubers more efficiently than parental strains. CONCLUSIONS: GS emerged as an elegant and rapid tool to optimize the antagonistic ability of Streptomyces strains. Optimization of the in vitro antagonistic activity against plant pathogens appears to be an effective approach to select for improved biocontrol agents. The enhanced phenotype did not depend on an overproduction of a specific antibiotic but rather on the secretion of a wider variety of secondary metabolites. SIGNIFICANCE AND IMPACT OF THE STUDY: Improved capacities of a biocontrol agent compensate for the lack of efficient chemical control of potato scab.
Asunto(s)
Agentes de Control Biológico , Barajamiento de ADN , Solanum tuberosum/microbiología , Streptomyces/genética , Antibiosis , Benzoquinonas/metabolismo , ADN Bacteriano/genética , Genoma Bacteriano , Lactamas Macrocíclicas/metabolismo , Phytophthora infestans/patogenicidad , Enfermedades de las Plantas/microbiología , Streptomyces/metabolismo , Streptomyces/patogenicidadRESUMEN
A method for quantification of recombinant DNA for Roundup Ready (RR) corn and RR soybean in soil samples is described. Soil DNA from experimental field samples was extracted using a soil DNA extraction kit with a modified protocol. For the detection and quantification of recombinant DNA of RR corn and RR soybean, a molecular beacon and two pairs of specific primers were designed to differentially target recombinant DNA in these two genetically modified crops. Soil DNA extracts were spiked with RR corn or RR soybean DNA, and recombinant DNA was quantified using real-time PCR with a molecular beacon. As few as one copy of RR corn genome or one copy of RR soybean genome was detected in the soil DNA extract.
Asunto(s)
Glycine max/genética , Plantas Modificadas Genéticamente/genética , Reacción en Cadena de la Polimerasa , Suelo/análisis , Transgenes , Zea mays/genética , ADN de Plantas/análisis , ADN Recombinante/análisis , Proteínas Fluorescentes Verdes/genéticaRESUMEN
The arbuscular mycorrhizal (AM) non-host plants mustard, sugar beet, lupin and the AM host plant cucumber were used as test plants. Cucumber plants were grown either in the absence of the AM fungus (AMF) Glomus mosseae or in a split-root system, with one side mycorrhizal and one side non-mycorrhizal. Root exudates of the AM non-host plants, the non-mycorrhizal cucumber plants and the mycorrhizal and the non-mycorrhizal side of the split-root system of mycorrhizal cucumber plants were collected and applied to cucumber plants inoculated with the AMF. Root exudates of non-mycorrhizal cucumber plants showed a significant stimulatory effect on root colonization, whereas root exudates from the mycorrhizal and the non-mycorrhizal sides of a split-root system of a mycorrhizal cucumber plant did not show this stimulatory effect and were even slightly inhibitory. Root exudates of the two AM non-host plants mustard and sugar beet significantly reduced root colonization in cucumber plants, whereas no such effect was observed when root exudates of the AM non-host plant lupin were applied.