Effect of watering regime and Fusarium virguliforme (Fv) infection on location of soybean cyst nematode (SCN) syncytia in soybean roots
N. TATALOVIC (1), G. L. Tylka (1), L. F. Leandro (1). (1) Iowa State University, Ames, IA, U.S.A.
The interaction of Fv with SCN results in earlier onset and increased SDS severity. The mechanism of this interaction is unclear. Studies were conducted to assess the effect of Fv infection and watering on formation of SCN feeding sites, called syncytia, in roots. Soybeans were planted in SCN-infested or SCN-free soil and grown at 27°C for 8 days prior to transplant into Fv-free or Fv-infested soil. Plants were subjected to two watering regimes: normal (watered daily) and reduced (watered on alternate days). Foliar SDS severity was assessed over 14 days. Root rot severity and root weight were evaluated after 14 days, and SCN syncytia were quantified and their location noted using microscopy. Foliar SDS severity was greater (p=0.0015) in co-inoculated plants than in Fv-inoculated plants in both watering regimes. However, root rot was greater in Fv-inoculated than in co-inoculated plants (p =0.04). The number of root tips was greater (p=0.02) in plants grown in SCN-infested compared to SCN-free soil. SCN syncytia were primarily located (89%) in the stele in plants inoculated with SCN alone, whereas the percent of syncytia in the stele was only 49% in co-inoculated plants (p=0.0068). The percentage of syncytia in the stele was 57% under normal watering and increased (p=0.05) to 82% under reduced watering. These data suggest that both pathogens respond to each other’s presence and that the interaction is affected by water availability.
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