التحري عن أنواع الجنس Fusarium المرافقة لبذور الزينيا و تقييم تأثيرها في إنبات البذور و نمو النباتات

Abstract EN

This study was carried out to detect the species of genus Fusarium that associated with zinnia seeds and test its pathogenicity under Laboratory and green house conditions.

Results of isolation and identification showed the existence of 6 Fusarium species associated with zinnia seeds, and all these species were recorded for the first time on this plant in Iraq.

These species were : F.

acuminatum, F.

culmorum, F.

oxysporum, F.

solani, F.

thapsinum, and F.

verticillioides.

Result showed the existence of F.

solani and F.

culmorum in 27.3 % of seed samples with 31.16 % and 7.59 % frequency rate respectively.

Other species were presented in 18.2 % of seed samples.

The preliminary test of the pathogenicity by cabbage seeds which included two separated experiments, showed that all the 22 isolates caused a significant reduction in the rate of cabbage seeds germination but only seven isolates were highly pathogenic, the percentage of germination in their treatments were 0-20 % compared to 97 and 98 % in control treatments.

F.

culmorum isolate (A33) gave the highest rate of decrease in seed germination (0%).

Test of pathogenicity by blotter method showed that all the 15 isolates of this genus caused a significant reduction in zinnia seed germination which more than half of them were highly pathogenic.

Isolates of F.

oxysporum (F14) and F.

solani (D4) caused the highest decrease in seed germination : 3 % and 7 % respectively.

Under greenhouse conditions the result indicated that all nine isolates caused a significant increase in disease incidence and severity comparing with control treatment.

Isolates F.

culmorum (A33), F.

oxysporum (F14) and F.

verticillioides (B24) caused a significant superiority in disease incidence and severity (97.5-100 % and 96.5-98 %).