Autecology of Fusarium oxysporum f. sp. raphani in soils suppressive and conducive to Fusarium‐wilt of radish

Abstract

Abstract Effects of organic amendments and alterations of environmental conditions on the inoculum potential of Fusariumoxysporum f. sp. raphani PEG‐4 (PEG‐4), estimated from its population dynamics and spore germinability, were investigated using soils suppressive (S‐soil) and conducive (C‐soil) to Fusarium‐wilt of radish. The results on the population dynamics of PEG‐4 in S‐ and C‐soils showed that the germination‐lysis mechanism, proposed by Chinn and Ledingham (Can. J. Bot. (1962) 39, 739–748), seemed to be applicable to S‐soil, while not application to C‐soil. Germination of PEG‐4 microconidia in soils supplemented with glucose and asparagine (1 mg g−1 of soil) was higher in C‐soil than in S‐soil, showing that S‐soil possessed a greater degree of fungistasis than C‐soil. Organic amendments, especially rice straw and fresh radish residue (FRR), brought about suppressive effects on the germination of PEG‐4 in both soils along with their decomposition. These results suggest that the autecology of PEG‐4 in S‐ and C‐soils was quite different depending on incubation conditions, and presence or absence of organic amendments. Copyright © 1995, Wiley Blackwell. All rights reserved