To produce their progeny, viruses use part of genetic, enzymatic and energetic resources of the infected host. In consequences, processes usually used to produce or to renew organic compounds and the exchanges between host cells, tissues and organs are partially, even completely, disrupted by biological activities of the pathogen.
All biological parameters of infected plants are impaired by viral infections. Resulting physiological disruptions (symptoms) correspond to changes in chlorophyllous accumulation (mosaics, yellowing and/or reddening), cell or tissue death (necrotic lesions) or tissue distortion (dwarfing, leafroll, swelling). Types and intensities of these symptoms depend both on inoculated host and on viral isolate used.
PVY isolates could induce mosaics and/or necroses (local lesions, veinal necroses or tuber necroses) :It is important to note that environmental conditions, characteristics of the inoculated plant and inoculums could modify the symptom expression. As an example, under particular environmental condition, necrotic symptom on potato tubers could be induced by some PVYN or PVYN-W isolates.