BIOLOGICAL AND MOLECULAR STUDIES ON FUSARIUM WILT DISEASE OF TOMATO

Abstract

Tomato (Solanum lypersicum Mill.) is ranked number 1 among fruits and vegetables with 14% of the total production worldwide (Food & Agriculture Organization of the United Nations, FAO, 2003). Fusarium wilt disease is only responsible for 10 to 50% of these losses (Lukyanenko 1991). In Egypt, the losses due to tomato wilt disease reached up to 67% (Lasheen 2009). Different Fusarium oxysporum isolates were tested under greenhouse conditions to determine their virulence potential toward tomato plants. Severity and development of Fusarium wilt disease was recorded 4, 6 and 8 weeks after pathogen inoculation. All the tested isolates were pathogenic and varied significantly with regard to their virulence potential on tomato under the test conditions. The ability of a Fusarium isolate to infect particular plant species dependent on specific genes encoding host determining ‘virulence factors’ that distinguish virulent from avirulent strains. Eight fungal proteins were identified from xylem sap of infected plants, encompassing the small secreted proteins called SIX1, Six2, Six3, Six4, Six5, Six6, Six7 and SIX 8. The results showed that the tested isolates were varied regarding to their pathogenicity potential toward tomato plants under greenhouse conditions. On the other hand, the amplicons of SIX1, SIX5 and SIX 7 were detected with most hyper virulent isolates while no amplicons for any tested SIX genes were observed with the nonpathogenic isolate (Fo162) as well as with the most hypo virulent isolates. These results, suggested that SIX1, SIX5 and SIX6 may play a distinct role in virulence potential of these Fusarium oxysporum isolates toward tomato plants under Egyptian conditions .