Abstract
20 isolates of 9 Fusarium spp. obtained from roots of cotton seedlings and roots infected with damping-off disease were used. Pre-emergence damping-off was recorded 15 days after planting for the cotton cultivars of Giza 80 and Giza 90. Post-emergence damping-off, survival and dry weight (mg/plant) were recorded 45 days after planting. Isolate, cultivar and isolate X cultivar interaction were significant sources of variation in all the tested parameters except the cultivar which was a non-significant source of variation in pre-emergence damping-off. Random Amplified Polymorphic DNA (RAPD) technique has been used as a molecular technique for typing and genetic characterization of Fusarium spp. using three different decamer random primers (3, 4, and 5). DNA was extracted from 9 different Fusarium spp. and used for polymerase chain reaction (PCR). The similarity levels were determined by Cluster analysis for RAPD-PCR profiles via phylogeny tree. Primer 3 was successful in separating the isolates of Fusarium solani, Fusarium moniliforme, Fusarium oxysporum and Fusarium semitectum. Isolates of F. oxysporum gave high DNA similarity (99.65%) with this primer. Primer 4 was successful in the separation of F. solani, F. oxysporum, F. moniliforme, F. semitectum and Fusarium sporotrichioides. This primer is suggested to be the best of all primers in separating F. sporotrichioides since it showed the highest DNA similarity degree (98.87%). Primer 5 was successful only in the separation of F. solani, F. oxysporum, F. moniliforme, and F. semitectum isolates. This primer was the best of all the primers in the separation of F. solani, and F. semitectum since it showed high DNA similarity degrees among these isolates (99.71 and 99.78% respectively). Results in this study evoke that isolates of Fusarium spp. exhibited diversity in pathogenicity on cotton cultivar and demonstrate that the use of RAPD analysis is useful in classification of Fusarium spp.