Factors Relating to Peanut Yield Increases After Seed Treatment with Bacillus subtilis. J. T. Turner, Department of Plant Pathology, Alabama Agricultural Experiment Station, Auburn University, Auburn 36849. P. A. Backman, Department of Plant Pathology, Alabama Agricultural Experiment Station, Auburn University, Auburn 36849. Plant Dis. 75:347-353. Accepted for publication 15 September 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0347.

Bacillus subtilis, when added as a seed treatment, consistently colonized the roots of peanut plants at rates exceeding 10⁴ colony-forming units (cfu) per gram of root tissue when evaluated 120 days after planting. Yield increases from 1982 to 1985 ranged from –3.5 to 37%, with only two incidences of negative responses in 24 tests. Peanuts responded most favorably to the bacterial seed treatment when subjected to stresses, such as limited water availability, poor rotational practices, or cool soils, caused by early plantings. Treatment of peanut seed with B. subtilis was associated with improved germination and emergence, increased nodulation by Rhizobium spp., enhanced plant nutrition, reduced levels of root cankers caused by Rhizoctonia solani AG-4, and increased root growth. The means by which B. subtilis may affect yield in peanuts are multiple and are not operative at the same time, making predictions of degree of yield responsiveness difficult.

Keyword(s): bacterization, root rot.