Potato plants have specific symptoms that look to me as virus, what is it really? Symptoms have appeared in the end of July. up to 30% of plants have them without any certain local difference across the field.
I am not a plant pathologist, but still the symptoms appear to me as caused by fungus, similar to that caused by Alternaria, or early blight. Less possibility of being symptoms of a viral infection.
@Инна, спасибо! Но там легкая почва, высокое поле, влаги лишней точно не было. Грибы исключены - рядом стоят совсем зеленые растения (защита фунгицидами на высоте). Я поставил выделение на комплекс патогенов. Кажется, что заражение вирусами усиливает проявление дефицита магния (растения с симптомами в основном в начале поля, где обычно мало внесено удобрений).
some leaves have necrotic and ring spot as symptoms of the infection with PVY.., But the symptoms of yellowing with the color of the large brown spots associated with the fall is not a well-known isolation or that the plant reaction as excessive sensitivity or stimulate resistance.
it seems like the chlorophyll degradation followed by spot necrosis, which may be due to the nutrients deficiency or even unbalanced sufficiency and sort of things. nonetheless, I also suspected to early blight or alternaria. it is also noteworthy to say that, sometimes, symptoms of disorders overlap and several disorders may be depicted by the same symptom, having that said, the symptoms in your picture is also feasible to be a viral disease symptom such as mosaic virus or etc, to make sure about it further investigation is needed.
thank you! We found also, that all symptomatic plants were infected by PYV, and symptomless plants nearby were virus-free. Is it expected that virus infection increase micro/macro-element deficiency?