RAPID COMMUNICATION Rhizobia survival in seeds coated with polyvinyl alcohol (PVA) electrospun nanofibres

The electrospinning technique of rhizobia immobilization in nanofibres is an innovative and promising alternative for reducing the harmful effects of environmental stress on bacteria strains in a possible inoculant nanotechnology product for use in agriculture. The use of polyvinyl alcohol (PVA) shows up as an effective polymer in cell encapsulation because of its physical characteristics, such as viscosity and power of scattering. The aim of these studies has been to evaluate the survival of rhizobia incorporated in PVA nanofibres, which were applied to soybean seed and then subjected to different storage times and exposure to fungicide. The maintenance of the symbiotic characteristics of the incorporated bacterial strains was also evaluated, noting the formation of nodules in the soybean seedlings. No significant differences in the cell survival at 0 h and after 24 h of storage were observed. After 48 h, a significant difference in the bacterial cell concentration of the seeds affixed with PVA nanofibres was observed. Exposure to the fungicide decreased the viability of the bacteria strains even when coated with the nanofibres. A larger number of nodules formed in soybean seedlings from seeds inoculated with rhizobia incorporated in PVA nanofibres than from seeds inoculated with rhizobia without PVA. Thus, the electrospinning technique is a great alternative to the usual protector inoculants because of its unprecedented capacity to control the release of bacteria. Resume : La technique d'electrofilage destinee al'immobilisation de rhizobiums dans des nanofibres est une solution de rechange prometteuse pour la protection de souches bacteriennes contre les effets nefastes des stress environnementaux, dans le contexte d'un possible produit nanotechnologique destine al'agriculture. L'alcool polyvinylique (PVA) se montre efficace dans la formation de polymeres d'encapsulation cellulaire en raison des attributs physiques de ces derniers, dont leur viscosite et leur pouvoir de diffusion. Le but des etudes presentes fut d'evaluer la survie des rhizobiums incorpores dans des nanofibres de PVA une fois appliques ades semences de soja puis assujettis adiverses periodes de conservation et al'exposition aun fongicide. On a egalement evalue le maintien des proprietes symbiotiques chez les souches bacteriennes encapsulees, en fonction de la formation de nodules chez des semis de soja. On n'a releve aucune difference quant ala survie cellulaire au temps initial et apres 24 h de conservation. Apres 48 h, on a observe une difference significative eu egard ala concentration de cellules bacteriennes chez les semences revetues de nanofibres de PVA. L'exposition au fongicide a diminue la viabilite des souches bacteriennes, meme en presence d'un enrobage de nanofibres. Comparativement aux semences inoculees, un plus grand nombre de nodules se sont developpes chez les semis de soja inocules avec les rhizobiums enfouis dans des nanofibres de PVA. Ainsi, la technique d'electrofilage s'avere une alternative interessante aux inoculants protecteurs en raison de sa capacite sans precedent acontroler la liberation des bacteries. (Traduit par la Redaction) Mots-cles : Bradyrhizobium, soja, immobilisation, electrofilage, encapsulation.