P-692 - Evaluation of the impact of winter small crops and oilseeds on soybean diseases caused by Fusarium graminearum in a relay cropping system

Fusarium graminearum (Fg) is an important small-grains and soybeans pathogen. Relay cropping (RC) is a practice that involves the harvest of a main cash crop plus a second crop in the same field with some overlap in growth cycle. RC have the potential to control pests by breaking disease cycles. To evaluate the effect of winter crops/oilseeds on soybean disease caused by Fg we tested in the greenhouse (i) the susceptibility to Fg of winter rye, barley, oilseeds and soybeans. The cultivars were planted in a Fg-inoculated (Fg+) and non-inoculated (Fg-) potting mixture (6 reps/treatment) and harvested after ~ four months. (ii) Winter cereals/oilseeds were tested for fungal disease reduction/control on soybeans. For this, pots were refilled with the used potting mixture in the treatments described in (i), and only soybeans were planted. In the vegetative stage, higher Fg incidence (P < 0.05) was observed in Fg+ barley < rye< < canola vs other treatments. In the flowering stage, Fg-incidence was higher in the Fg+ vs Fg- for all the cultivars except canola. At maturity, no Fg-incidence was observed in rye, either Fg+ or Fg-. The number of pods formed in camelina, canola, and soybean was 572.3, 8.8, and 29.5 in Fg + pots compared with 759, 23.6, and 49 in Fg- controls, respectively. The average number of nodules was lower (P < 0.05) in Fg+ soybean (32.8) compared with 103.6 in the Fg- group. Interestedly, for the soybeans growing in the used potting mix (ii), no significant difference in stand counts, plant heights, fresh and dry weights of shoot and root was observed.