VIEW ARTICLE

Radial Extent of the Bean Spermosphere and its Relation to the Behavior of Pythium ultimum. M. E. Stanghellini, Department of Plant Pathology, University of California, Berkeley 94720, Present address of senior author: Department of Plant Pathology, University of Arizona, Agricultural Experiment Station, P.O. Box 1308, Mesa 85201; J. G. Hancock, Department of Plant Pathology, University of California, Berkeley 94720. Phytopathology 61:165-168. Accepted for publication 8 September 1970. DOI: 10.1094/Phyto-61-165.

Bean seed exudates diffused through moist soil and stimulated sporangial germination of Pythium ultimum. In soil contiguous to the seed, 78% sporangial germination occurred within 3-4 hr after sowing. Extensive mycelial growth in soil and subsequent host penetration and infection occurred within 24 hr. Bean seed exudates, in sufficient quantity to stimulate sporangial germination of P. ultimum and chlamydospore germination of Fusarium solani f. phaseoli and to support vegetative growth, diffused through soil maintained at 28% moisture (pF 1.7) up to 10 mm from the seed surface within 24 hr. A lower soil moisture content (15.7%, pF 2.0) resulted in a decrease in the magnitude of the bean spermosphere.