engleski

Effect of Diaporthe/Phomopsis species on soybean seed germination

Infection of soybean seeds (Glycine max (L.) Merr.) by Phomopsis/Diaporthe species, which are known as primary casual agents of pod and stem blight, stem canker and seed decay, reduces the seed germination and emergence (Kulik and Schoen 1981, Zorilla et al. 1994). Numerous weed species can be alternative hosts for fungi of Phomopsis/Diaporthe genus. In this research, Phomopsis longicolla, Phomopsis sojae and Diaporthe phaseolorum var. caulivora were discovered only on Abutilon theophrasti Medik. The aim of our research was to evaluate the influence of Phomopsis/Diaporthe species on soybean seed germination, germ length and germ necrosis and to compare pathogenicity of isolates harbored by the A. theophrasti to soybean with isolates of the same parasites from soybean. P. longicolla, P. sojae and D. p. var caulivora were isolated from infected soybean plants, as well as from seeds and plants of A. theophrasti. Pathogenicity test was performed on 6 isolates from soybean (2 isolates of Phomopsis longicolla, Phomopsis sojae and Diaporthe phaseolorum var. caulivora, respectively) and 5 isolates from diseased A. theophrasti plants (3 isolates of P. longicolla, 1 isolate of P. sojae and 1 isolate of D. p. var. caulivora), according to Vidić et al. (1995). Cultures of P. sojae and P. longicolla, being 2 weeks old, and cultures of D. p. var. caulivora, being 4 weeks old, each grown on PDA medium (pH 4, 5), were used for inoculation. Substrate with mycelium and pycnidia of species P. longicolla and P. sojae, and perithecia with ascospores of D. p. var. caulivora were chopped up in 100 ml of sterile water. Soybean seeds were kept in the suspension of conidia and mycelium for 24 hours, and then transferred to boxes covered with wet filter paper. They were kept at a room temperature of about 25 º ; ; C. In the second experiment soybean seeds were kept in the suspension for 5 minutes and then sowed in sterile soil. Percentage of germinated seeds was determined after ten days. The same procedure was repeated in the control experiment, but instead of the suspension of inoculate, seeds were kept in sterile water. Results of the first experiment showed that the isolates of Phomopsis/Diaporthe species from soybean and A. theophrasti were pathogenic to soybean and influenced the germ length, which was shorter than the length of healthy germs. Isolates of P. longicolla and P. sojae had greater influence on germ length than the isolates of D. p. var caulivora. All three fungi caused soybean germ necrosis and grain rot. Germination test showed that the isolates of P. longicolla and P. sojae had a greater effect on soybean seed germination than the D. p. var caulivora isolates. This research confirmed that the isolates of same species differ with respect to pathogenicity and seed germination. It also proved that there are no significant differences in the pathogenicity of the same species’ isolates, which were isolated from different hosts.

soybean ; seed germination ; Diaporthe/Phomopsis species

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