**5. Diseases mode of transmission**

The ecosystem of grassland is diverse and complex. Apart from the climatic changes that the plants have to face, there are other threats that are threatening the peaceful existence of the C3 and C4 plants aside from being a food source to herbivores. Diseases in grassland can spread like wildfire depending on the mode of transmission. Several viruses or viroids could spread extensively in the field just by contact between healthy leaves. Viruses are spread systemically and can be transmitted through natural grafting. Root graft can also transmit viruses or even parasitic plants. Common transmission modes of plant diseases are often by vegetative propagation. There are also plant diseases that transmit through seed. For instance, sour-cherry yellows in the *Prunus spp*. The disease is caused by the Prune Dwarf Virus that causes young leave to have chlorotic yellow rings or mottle. The virus can be transmitted by infected pollen grains or infected seeds when pollinated by bees or during propagation process (**Table 2**).
