Explanation:

Statement 2: Most bacteria that are associated with plants are actually saprotrophic and do no harm to the plant itself. However, a small number, around 100 known species, are able to cause disease. Bacterial diseases are much more prevalent in subtropical and tropical regions of the world.
For e.g. Pseudomonas syringae pv. tomato disease causes tomato plants to produce less fruit.
Statement 3: Rice blast is a disease caused by a necrotrophic fungus. The oomycetes are fungus-like organisms. They include some of the most destructive plant pathogens.
Statement 4: Viroids are the smallest infectious pathogens known. They are composed solely of a short strand of circular, single-stranded RNA without protein coat.
Plant viruses are generally transmitted from plant to plant by a vector, but mechanical and seed transmission also occur.
Statement 5: Nematodes are small, multicellular wormlike animals. Many live freely in the soil, but there are some species that parasitize plant roots.
They are a problem in tropical and subtropical regions of the world, where they may infect crops.
Potato cyst nematodes (Globodera pallida and G. rostochiensis) are widely distributed in Europe and North and South America.