EVALUATION OF SOME TRICHODERMA SPECIES IN BIOLOGICAL CONTROL OF POTATO DRY ROT CAUSED BY FUSARIUM SAMBUCINUM FUCKEL ISOLATES

Abstract

Fusarium dry rot of potato is a major disease caused by several Fusarium species, and Fusarium sambucinum Fuckel is considered to be the most aggressive species in worldwide, including Turkey. Biological control based on the use of microorganisms to suppress tuber diseases offers an attractive alternative that has gained great attention due to the significant potential. Several fungal biocontrol agents have been used in plant disease control, and Trichoderma group has been reported as effective against tuber pathogens such as F. sambucinum. This study was carried out under in vitro and in vivo conditions. During in vitro conditions, the effects of fifteen Trichoderma isolates (T. asperellum OT1; T. viride VG18; T. viride VG19; T. harzianum TZ16, T. harzianum LO52; T. gamsii VG47; T. gamsii VG48; T. virens KB31; T. strigosum LO43, T. strigosum . LO8; T. neokoningii A 15; T. atroviride VG3; T. tomentosum VG2; T. Inhamatum KEB12; T. hamatum OT16) were studied against three isolates of F. sambucinum (Fs2, Fs3 and Fs4) in PDA medium by using duel culture technique in incubation at 22 +/- 24 degrees C. The most effective isolates were T. virens KB31, T. gamsii VG47, T. hamatum OT16, T. asperellum OT1, T. harzianum LO52, T. atroviride VG3, respectively. During in vivo conditions, potato tubers, CV. Desire were wounded and inoculated with 1 ml of Trichoderma isolates suspensions (10(7) spores mL(-1)), 24 h prior inoculation by F. Sambucinum. Reduction rate of dry rot in tubers was recorded during 5-6 weeks of incubation at 20-24 degrees C to compare with control treatments. Tuber dry rot was reduced by the antagonistic fungal isolates with different rates. The most effective isolates were T. viride VG18, T. asperellum OT1, T. harzianum TZ16, T. virens KB31 and T. inhamatum KEB12, respectively. Potato tubers were also treated with commercial seed fungicides named Celest-Max (R) (Fludioxonil, SC 100 g/l)] and Quadris (R) (Azoxystrobin, SC 250 g/l). The results revealed that Fludioxonil treatments were more effective compared to Azoxystrobin treatments and the biological control agents.