Plant and Soil

, Volume 268, Issue 1, pp 271–283

Green manures and crop sequences influence alfalfa root rot and pathogen inhibitory activity among soil-borne streptomycetes

  • B. Elizabeth. Wiggins
  • Linda L. Kinkel
Article

DOI: 10.1007/s11104-004-0300-x

Cite this article as:
Wiggins, B.E. & Kinkel, L.L. Plant Soil (2005) 268: 271. doi:10.1007/s11104-004-0300-x
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Abstract

A two-year trial was conducted to determine the effects of green manures and crop sequences on plant disease, streptomycete and bacterial densities, and inhibitory activity of indigenous streptomycetes against four target pathogens. Green manure treatments, buckwheat (Fagopyrum esculentum L.), canola (Brassica napus L.), sorghum-sudangrass (Sorghum bicolor) (L.) Moench × Sorghum sudanense (Piper) Stapf.), and fallow control were tested in conjunction with three crop sequences in a Phytophthora-infested soil placed in containers. Alfalfa (Medicago sativa L.), potato (Solanum tubersoum L.), or corn (Zea mays L.) was grown in the first year, and alfalfa was grown in all containers in the second year. Compared to fallow controls, alfalfa grown in sorghum-sudangrass- or buckwheat-treated soil had significantly greater stand counts and total biomass, respectively. In addition, alfalfa grown in fallow-treated soils had the greatest Phytophthora root rot as a function of stand count. Crop rotation also had a significant effect on alfalfa root rot and yield. Potato scab disease intensity was greatest on tubers grown in fallow-treated soils, while tubers grown in canola-treated soils had the highest yields (total tuber weight). Green-manure-treated soils tended to have greater streptomycete and bacterial densities than fallow-treated soils. In addition, buckwheat- or sorghum-sudangrass-treated soils had greater proportions of streptomycetes that were antagonistic against the target pathogens than fallow-treated soils. The proportion of antagonists in soil was negatively correlated with alfalfa root rot, and positively correlated with alfalfa stand counts. Inhibitory activity of the streptomycetes was also negatively correlated with potato scab and positively correlated with potato yield. These data suggest that green manures may provide a strategy for increasing pathogen inhibitory activity within the streptomycete community in soil, and, in conjunction with crop rotation, may contribute to the control of a diverse collection of soil-borne plant pathogens on multiple crop species.

Abbreviations

GM

green manure

WA

water agar

SCA

starch casein agar

OA

oatmeal agar

PDWA

potato dextrose water agar

PDA

potato dextrose agar

CZB

Czapek-Dox broth

DAP

days after planting.

Copyright information

© Springer 2005

Authors and Affiliations

  • B. Elizabeth. Wiggins
    • 1
  • Linda L. Kinkel
    • 1
  1. 1.Department of Plant PathologyUniversity of MinnesotaSt. PaulUSA