It can be hypothesized that fungal pathogen is responsible for decreased yield.
Explanation:
As the extensive heavy rain changed the climate of that area the soybean plant was effected by pathogenic fungus grown in the field. As we know that fungi makes spores that can withstand harsh environment. Humid and moist environment is favorable for fungi growth. So when spores find a suitable environment they grow rapidly. In the given example, the fungi was pathogenic that produced toxic compounds and effected the growth of soybean plant by damaging its root system and water supply to plant.
