Source of Infection of Sunflower Plants by Diaporthe helianthi in Yugoslavia

Abstract

D. beliantbi 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. belianthi can precociously complete the development of its ascomata in autumn. Perithccial differentiation and maturation d o 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 conidiomau 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. ZusammcnfassungUrsprung dcr Infcktion bci Sonncnblumcn durch Diaprtbe bcLanrhi in Jugoslawicn D. belianthi zeig cine jihnlichen EntwicWungsrhythmw wie der vieler pflanzenpathogenen Ascomycotina: die anamorphe Form entwickelc sich im Sommer, und die teleomorphe Form im Winter. Jedoch kann D. helianthi bci hoher Fcuchtigkeit die Entwirllung der Fruchtkbrper der Asci im Herbst friihzeitig vollenden. Differenzierung und Reife der Perithecien erfolgen nicht gleichzeitig. Konidienfruchtkorper in epidermalen und subcpidermalen Geweben und Fruchtkorper der Asci, die rich im Phloemsystem befanden, wurdcn im gleichen Detritus der iibcrwinterten Sonnenblumenstielen in unterschiedlichen Verhdtnissen gefunden; die Konidienfruchtkorper waren jedoch in U.J. Copyriphc Qcmnce &ca codc bcrmenc:

Phomopsis Stem Canker: A Reemerging Threat to Sunflower (Helianthus annuus) in the United States

“…They concluded that the Diaporthe isolates that produced predominantly b-conidia were similar to D. helianthi, as described in Yugoslavia. However, they were not able to resolve inconsistencies in the description of the Diaporthe isolates found in Ohio in comparison with those from Yugoslavia (Mihaljčević et al 1985), particularly for those that produced predominantly a-conidia. In our study, D. helianthi isolates produced white, floccose, and dense mycelia, dark-brown colored, on PDA; size of b-conidia (20 to 35 by 0.5 to 2.7 µm) was consistent with Gulya et al (1997).…”

Transmission and overseasoning of Diaporthe adunca on Plantago lanceolata

“…After overwintering, these infected stalks were able to infect newly formed flower stalks of carrot. In contrast, Mihalj cević et al (1985) were unable to infect sunflower with conidia of D. helianthi from overwintering pycnidia, but infections could be readily established with ascospores from overwintered perithecia. Our results indicate that conidia of D. adunca from pycnidia on overwintered P. lanceolata scapes are capable of infecting spikes through vertical splash dispersal during rain events ( Table 4).…”

“…Some Phomopsis spp. can be seedborne or overseason with (immature) pycnidia and/or perithecia on infected debris (Von Arx, 1951;Kulik, 1983Kulik, , 1984bMihalj cević et al, 1985).…”

Cytological Observations of the Infection Process by Phomopsis helianthi (Munt.‐Cvet) in Leaves of Sunflower

“…Stem canker caused by P. helianthi started in the leaves of sunflowers. The systemic nature of the disease was recognized by Mihaljcevic et al. (1985).…”

“…(1991) gave a coarse cytological description of the infection process in naturally infected leaves, but detailed cytological and physiological investigations have not yet been reported. The systemic nature of the disease was recognized by Mihaljcevic et al. (1985).…”