Sunflower white rust – albugo tragopogonis, a new disease for the North-East Bărăgan area

Abstract

The sunflower, Helianthus annuus, is a cultivated species which is attacked by many diseases, such as: blight produced by Plasmopara helianthi (sin. P. halstedi) fungus, white rot produced by Sclerotinia sclerotiorum fungus, black spotting produced by Phoma oleracea var. helianthi fungus, sunflower’s brown spotting and stems’ breaking produced by Diaporthe helianthi f. c. Phomopsis helianthi fungus and brown rot produced by Botrytis cinerea fungus etc. (Iacob Viorica, Hatman, M., Ulea, E., Puiu, I., 1998, Velichi, E. 2012) In the North-East of Brăila County, attacks of a pathogenic agent which presents symptoms which had not been signalled in the previous years have been observed during 2017. These attacks have been signalled on the sunflower leaves, starting with the middle of June, more affected being the leaves from the lower half of the plants. After the attack was signalled, samples of leaves that presented attack symptoms have been taken. These samples have been examined first of all at the stereo-microscope, being observed the presence of some blisters which had the membrane broken, here and there, showing a matter with an aspect somewhat dusty. From this matter, a preparation on microscopic slide was executed, in glycerine, after which it was examined at the optic microscope. The careful observation has confirmed it is about the caduceus sporangia of Albugo tragopogonis fungi which produce the disease known in other countries (U.S.A., South Africa) under the name of white rust. The pathogen frequently attacks the sunflower in these states, having sometimes an invasive character. The disease is mentioned in our country by Vera Bontea in the paper “Saprophytic and Parasitic Fungi from Romania, Vol. II” as being present at some species of plants from Asteraceae (Compositae) family, out of which the most known is the thistle (Cirsium arvense). The attack of this fungus on sunflower in our country is not mentioned in this paper. Up to present, the causes which have determined the occurrence of this pathogen in Romania are not known.