Genetic diversity and population structure of Fusarium oxysporum f. sp. cepae, the causal agent of fusarium basal plate rot on onion, using RAPD markers

Bayraktar Harun

doi:10.1501/tarimbil_0000001133

Abstract

A total of 116 single spore isolates of Fusarium oxysporum f. sp. cepae representing seven populations from Turkey and one population from Colorado, USA were subjected to molecular marker analysis using Random amplified polymorphic DNA (RAPD) technique. Using eleven polymorphic primers, 110 RAPD fragments were obtained with an average of 10 polymorphic bands per primer. Cluster analysis with UPGMA revealed five distinct lineages at arbitrary level of 65% similarity. The majority of F. oxysporum f. sp. cepae isolates from Turkey were observed to derive probably from the same clonal lineage. Genetic estimates and population differences demonstrated that the isolates from Turkey were significantly distinct from Colorado isolates and that Bursa population was the most divergent among Turkish populations. Cluster analysis of Nei's genetic distances supported populations grouping according to the geographical regions. Comparison of genetic differentiation estimates (H T : 0.140, H S : 0.124) revealed low levels of genetic differentiation among Turkish populations. Only, 11.4% of total genetic diversity (G ST ) attributed to differentiation among the geographical populations. Analysis of molecular variance (AMOVA) confirmed that there was low genetic differentiation among populations. The results suggest that RAPD-PCR is a useful method for analyzing genetic variation within and between populations of F. oxysporum f. sp. cepae .

Highlights

Onion (Allium cepa L.) is a crop of economic importance and widely grown in many countries
These primers produced a total of 110 reproducible fragments among the 116 isolates of F. oxysporum f. sp. cepae, all of them were polymorphic, giving a ratio of 10 polymorphic bands/primer
Random Amplified Polymorphic DNA (RAPD) analysis of genomic DNA from the pathogenic isolates revealed the presence of five lineages at the arbitrary level of 65% similarity (Figure 2)

Summary

Introduction

Onion (Allium cepa L.) is a crop of economic importance and widely grown in many countries. Cepae W.C Snyder & H.N Hansen, the causal agent of Fusarium basal rot is a common disease in onion growing regions worldwide, causing economically significant losses in both field and storage (Abawi & Lorbeer 1971; Sumner 1995). The pathogen infects the root and basal plate areas of onion plants. The pathogen can cause yield losses on other Allium species such as garlic, chive and shallot (Sumner 1995). Cepae has a high degree of pathogenic variability on onion plants, the classification of different races has not been described yet (Sumner 1995; Özer et al 2004) F. oxysporum f. sp. cepae has a high degree of pathogenic variability on onion plants, the classification of different races has not been described yet (Sumner 1995; Özer et al 2004)

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