There is evidence of fungi appearing over 1 billion years ago [1].
Plants first appeared around 400 million years ago or later [2]. In fact, early plants required symbiosis with fungi to grow. Even now, plants grow better if they have symbiosis with fungi and most plants (such as tomatoes) can grow symbiotically with fungi. But it is cheaper to use fertilizers, and those are used instead.
Still, forest ecosystems still depend on fungi and require them as a way to recycle plant material (fallen leaves, dead plants and trees).
Evolutionary, fungi existed well before plants managed to evolve.
Plants first appeared around 400 million years ago or later [2]. In fact, early plants required symbiosis with fungi to grow. Even now, plants grow better if they have symbiosis with fungi and most plants (such as tomatoes) can grow symbiotically with fungi. But it is cheaper to use fertilizers, and those are used instead. Still, forest ecosystems still depend on fungi and require them as a way to recycle plant material (fallen leaves, dead plants and trees).
Evolutionary, fungi existed well before plants managed to evolve.
1. https://en.wikipedia.org/wiki/Evolution_of_fungi
2. https://en.wikipedia.org/wiki/Evolutionary_history_of_plants