Polymyxa betae is an obbligate intracellular parassite and vector of Beet Necrotic Yellow Vein Virus, agent of rhizomania, an extremely severe disease of sugar beet. 2,4-Diacetylphloroglucinol (DAPG) is a wide spectrum antibacterial and antifungal antibiotic and a major determinant in the biological control of several plant diseases. It is produced by many strains of Pseudomonas both in vitro and in the rhizosphere of crop plants. It has previously demonstrated that DAPG and P. fluorescens F113Rif pCUGP, a genetically modified strain iperproducing DAPG, is able to inhibit viability of P. betae zoospore and resting spore in microcosm. In this work the protection efficacy of synthetic DAPG has been compared to that provided by GM-Pseudomonas, taking also into account the bacterial colonization levels obtained and the possible phytotoxic effect of DAPG, both in microcosm and in field. In microcom experiments, at the lowest concentrations still affecting P.betae viability, synthetic DAPG showed phytotoxic effect that inhibits, in some extent, sugar beet seed germination and plant growth. In the same condition, P. fluorescens F113Rif pCUGP efficiently colonized sugar beet rhizosphere producing a clear protection (although minor if compared with synthetic DAPG effect) against rhizomania. However, no phytotoxicity was observed. Following these promising evidences, sugar beet seed, inoculated with P. fluorescens F113Rif pCUGP were sown in a field naturally infected by rhizomania, but no protection against disease was attained. In open field condition, introduced strain appeared less able to colonize rhizosphere than resident pseudomonads population. Rhizospheric competitive-colonization ability, rather than the production of DAPG, seems therefore to play here the principal role in the efficacy of bioprotection. The possibility to increase colonization by improving the quality of the inocula (cell number and nature of the strain) and its application technique, is then discussed.
Effect of Pseudomonas fluorescens pCUGP and synthetic DAPG on biocontrol of Polymyxa betae/Beet Necrotic Yellow Vein Virus complex in sugar beet
BASAGLIA, MARINA;CASELLA, SERGIO
2002
Abstract
Polymyxa betae is an obbligate intracellular parassite and vector of Beet Necrotic Yellow Vein Virus, agent of rhizomania, an extremely severe disease of sugar beet. 2,4-Diacetylphloroglucinol (DAPG) is a wide spectrum antibacterial and antifungal antibiotic and a major determinant in the biological control of several plant diseases. It is produced by many strains of Pseudomonas both in vitro and in the rhizosphere of crop plants. It has previously demonstrated that DAPG and P. fluorescens F113Rif pCUGP, a genetically modified strain iperproducing DAPG, is able to inhibit viability of P. betae zoospore and resting spore in microcosm. In this work the protection efficacy of synthetic DAPG has been compared to that provided by GM-Pseudomonas, taking also into account the bacterial colonization levels obtained and the possible phytotoxic effect of DAPG, both in microcosm and in field. In microcom experiments, at the lowest concentrations still affecting P.betae viability, synthetic DAPG showed phytotoxic effect that inhibits, in some extent, sugar beet seed germination and plant growth. In the same condition, P. fluorescens F113Rif pCUGP efficiently colonized sugar beet rhizosphere producing a clear protection (although minor if compared with synthetic DAPG effect) against rhizomania. However, no phytotoxicity was observed. Following these promising evidences, sugar beet seed, inoculated with P. fluorescens F113Rif pCUGP were sown in a field naturally infected by rhizomania, but no protection against disease was attained. In open field condition, introduced strain appeared less able to colonize rhizosphere than resident pseudomonads population. Rhizospheric competitive-colonization ability, rather than the production of DAPG, seems therefore to play here the principal role in the efficacy of bioprotection. The possibility to increase colonization by improving the quality of the inocula (cell number and nature of the strain) and its application technique, is then discussed.
Pubblicazioni consigliate
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
