What type of plant response can indicate an infection by Beet necrotic yellow vein furovirus?

The indication of an infection by Beet necrotic yellow vein furovirus is primarily associated with distorted vascular tissue. This virus affects the phloem—the vascular tissue responsible for the transport of nutrients. When a plant is infected, the characteristics of the vascular tissue can change as the plant tries to cope with the infection. This distortion often manifests as stunted growth, yellowing leaves, or vein necrosis, which are direct indicators of how the plant's internal vascular structure is responding to the viral attack.

The other options don’t align with the typical responses seen with this viral infection. For instance, an increase in chlorophyll levels would suggest a healthy plant that is efficiently photosynthesizing, which is not the case for a plant infected by this virus. Faster growth rates would imply that the plant is thriving, while no visible changes would mean the plant is unaffected or healthy, contrary to what is observed in infected plants. Thus, distorted vascular tissue is a clear and direct indicator of the impact that the Beet necrotic yellow vein furovirus has on the plant.