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Source of Infection of Sunflower Plants by Diaporthe helianthi in Yugoslavia

Mihaljčević, M., Muntan̄ola‐Cvetković, M., Vukojević, J., Petrov, M.
Phytopathologische Zeitschrift 1985 v.113 no.4 pp. 334-342
Diaporthe helianthi, Helianthus annuus, Phomopsis, asci, ascocarp, ascospores, autumn, host plants, humidity, phloem, spring, stem form, stems, summer, winter, Yugoslavia
D. helianthi shows a developmental rhythm similar to that of many plant pathogenic Ascomycotina: the anamorph develops during the summer and the teleomorph during winter. However, under conditions of high humidity D. helianthi can precociously complete the development of its ascomata in autumn. Perithecial differentiation and maturation do not occur simultaneously. Conidiomata in epidermal and subepidermal tissues and ascomata located in the phloem system were seen in the same over‐wintered sunflower stem detritus in various proportions; however, conidiomata were prevalent on samples collected in early winter, while ascomata were much more numerous in spring. Infections could not be obtained when conidiomata were employed as inoculum. On the other hand, ascospores from perithecia formed on over‐wintered stem residues were capable of provoking infection regardless of the season in which the residues were collected. In the conditions of Voivodina (Yugoslavia), ascospores are the principal source of infection of the so‐called “Phomopsis” disease of sunflower, not only from one year to the next, but also during the life‐span of the host plants.