DETERMINATION OF SEED-BORNE FUNGI IN ONION AND THEIR TRANSMISSION TO ONION SETS

Samples of onion (Allium cepa L.) seeds were obtained from seven regio ns in Turkey. The seed coat, embryo and endosperm were cultured, the s eedborne fungi were determined and their transmission to onion sets wa s investigated in both sterile and field soils. Among the fungi determ ined, Aspergillus alutaceus Berk, and Curt., Beauveria bassiana (Bals. ) Vuill., Cladosporium cladosporioides (Fres.) de Vries, Geotrichum sp ., Humicola fuscoatra Traaen, Trichoderma harzianum Rifai and T. pseud okoningii Rifai in onion seeds, and Fusarium culmorum (W.G.Sm.) Sacc., F. graminearum Schwabe and F. sambucinum Fuckel in onion sets, were r ecorded for the first time. Aspergillus niger v. Tieghem was found at the highest rate in seed samples (especially in the seed coat), and in bulbs and roots of onion sets that developed from these seeds, whethe r in sterile or field soil. Fusarium oxysporum Schlecht was isolated a t a higher rate from onion sets grown in sterile or field soil, than f rom seeds. F: acuminatum Ellis and Everhart, F. sambucinum, F. equiset i (Corda) Sacc. and F. graminearum were isolated only from onion sets grown in sterile soil. In dual culture tests, these Fusarium isolates were inhibited by A. niger and thus, except for F: oxysporum, could no t develop in agar plate. The Fusarium spp. appeared-in onion sets grow n in sterile soil and were inhibited by other fungi infield soil. It w as concluded that all fungi were seedborne and that A. niger and Fusar ium spp., but not the other fungi, were transmitted from the seeds to onion sets. A. niger and F. oxysporum were also transmitted through th e soil.