Novel inoculants for an environmentally-friendly crop production

The high input of agrochemicals into soils is a major agricultural technique for enhancement of plant crop production, but it is also an environmental hazard. Concern over health hazards related to agrochemicals, especially on radioactively polluted territories, as well as economic problems, have promoted fundamental research to search for new agrobiotechnologies. Nonsymbiotic plant growth-promoting Rhizobacteria (PGPR) are often used as inoculants; however, they are not as effective as endophytic bacteria. These bacteria have the advantage of living within the plant tissue, protecting the plant from superinfection by soil bacteria, and recolonizing the plant surface after some stress situations in the soil. Although the use of beneficial microorganisms is not a new idea, it is an idea that is not heavily utilized. Application of inoculants designed on the base of competitive endophytic bacteria may be a full or partial alternative to agrochemicals, and can diminish the level of penetration and accumulation of heavy metals and radionuclides inside plants. This study evaluates the input of the association of the bacteria, isolated from the plant interior, in the crop of corn (Zea mays) and develops inoculants on their base. Nitrogen-fixing Klebsiella oxytoca VN13 along with Xanthomonas maltophilia VN12 were found to be useful bacteria, the former capable of excreting auxins and antimicrobial substances, the latter promoting assimilation of soil phosphorous by the plants. As the association of the two bacteria has been chosen as an effective endophytic system for the inoculant development, the two are mixed to form an inoculant 'Duet' which is directly inoculated into seeds. Corn inoculated with this 'Duet' produced greater yields, and possessed a greater percentage of protein. In addition, experiments performed in Chernobyl, showed that the 'Duet' could protect the plant from radionuclides penetration. It is suggested that a novel inoculant, 'Kleps', be applied, as the formulation is simple, it is inexpensive, it can be produced on a large scale, and it can be stored for a long period of time in a relatively small volume. It is clear that simple formulations of novel inoculants can be designed on the base of the competitive endophytic bacteria for an environmentally friendly crop production on poor and polluted territories as an alternative to the use of agrochemicals. Copyright (C) 1996 Elsevier Science B.V.