Strains of Streptomyces were tested for their ability to reduce population densities of the root-lesion nematode (RLN), Pratylenchus penetrans, in roots of alfalfa (Medicago sativa) in growth chamber assays. Previously, these strains were shown to suppress potato scab disease, caused by Streptomyces scabies, in field experiments and to inhibit in vitro growth of a wide range of plant-pathogenic fungi and bacteria. Inoculation with Streptomyces at planting significantly reduced RLN population densities in roots of both susceptible and resistant alfalfa varieties grown in either heat-treated or untreated soil. Reductions in RLN population densities were observed 6 weeks after nematode inoculation. Shoot dry matter was not affected by any treatment; root dry weight was reduced in Streptomyces plus nematode treatments compared to the nematode inoculation alone m some experiments but was not affected by Streptomyces when RLN was absent. Mutant strains not producing antibiotics in vitro also reduced RLN population densities in alfalfa roots and all strains maintained high population densities after inoculation into heat-treated soil and on alfalfa roots. These strains may be useful in multi-crop, multi-pathogen management programs to augment genetic resistance to plant diseases.
Bibliographical noteFunding Information:
This paper is a joint contribution from the Plant Science Research Unit, USDA, Agricultural Research Service and the Minnesota Agricultural Experiment Station (Paper No. 001220106, Scientific Journal Series). Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the USDA, and does not imply its approval to the exclusion of other products and vendors that might also be suitable. We thank Drs. S. Chen and J. Powell for valuable comments on the manuscript.
- Biological control
- Plant growth promoting bacteria
- Rhizosphere bacteria