Preliminary field test to assess the performance of the azospirillum-sorgum association in different crop management conditions.

In view of the release of 3 GM strains characterised for their ability to synthesize Indol-3- Acetic Acid (IAA-, IAAn, IAA+++) an alternative experirnent with WT strains with different ability in the synthesis of IAA was carried auto The evaluation of the effects of "natura!" strains, somehow similar in this aspect to the GM to be tested would be helpull even consideringt that A. brasilensSep 245, used in this study, is the base system to construct the genetically modified strains. The 3 WT strains provided, A. irakenseK BC1 (low IAA-producer), A. brasilenseS p245 (medium-IAA producer) and A. brasilense Sp7 (high-IAA producer) were compared to an untreated contrai, under three different levels of nitrogen fertilisation (0,90 and 180 kg ha-l). In order to evaluate the effect of IAA on the performance of the Azospirillum/plant association multiple fiela' trial including different conditions or water supply and soil managemen were also considered. The experirnental scheme included a comparison between irrigation at 100% of restitution of root system in the first soillayer could have no beneficial effects, especially in very drought conditions, such as thbse occurred this year. These results could be related to the effect of IAA over-producer strains on root system, as previously described for A. brasilense Sp6 I AA over-produce mutant, which affects the root length density particularly in the first 0-30 cm soil layer. When water is a limiting factor (not irrigated soil) the association with IAA producer azospirillum improves drought resistance while when water is available (irrigated soil) a further development of the root system would not provide benefits. Minimum tillage causes a greater development of the root system in the upper soillayer compared to conventional tillage (ploughing

Effect of Pseudomonas fluorescens pCUGP and synthetic DAPG on biocontrol of Polymyxa betae/Beet Necrotic Yellow Vein Virus complex in sugar beet

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

Interaction of genetically modified Azospirillum with biotic or abiotic components of the agro-system

Interaction ofAzospirillum with biotic or abiotic components of the agro-syste

Evaluation of genetically modified biological control agents (GM-BCAs) on pathogenic fungi

Torino (Italy