Screening Of Iranian Onion Seed Sets Genotypes For Resistance To Fusarium Oxysporum f. sp. Cepae

Root and basal rot disease (RBR) of onion, Fusarium oxysporum f. sp. cepa (FOC) is one of the most important diseases, causing tremendous losses in onion growing areas worldwide. In this study, various onion genotypes, including eight main and dominant Iranian seed sets and two exotic ones were tested against FOC incidence in greenhouse and field conditions of various growing stages. The incidence of the PBR was determined at three stages of early, flowering and seed setting stages on the bases of disease severity. The genotypes reacted differentially to FOC within and between various stages with a very high significant level. The genotypes were classified in five scoring scales accordingly. Highly infected ones tended to be associated with the high mean scores of 75 – 100 percent severity and the least infected genotypes had the lowest scores of 0 – 10 percent. In addition, the examined genotypes were ranked from 1 to 10 according to their markedly differing reactions to FOC at various stages. Variance and cluster analysis also showed similar results among the genotypes with various levels of infections. There was a direct, positive and enhancing correlation for every genotype to infection as the growing stages were reaching to maturing stage.