MOLECULAR CHARACTERIZATION OF Fusarium oxysporum F. SP. CUBENSE (FOC) TROPICAL RACE 4 CAUSING PANAMA DISEASE IN CAVENDISH BANANA IN PAKISTAN.

Fusarium wilt or Panama disease poses a great risk to banana production worldwide and is caused by Fusarium oxysporum f. sp. Cubense (Foc). Its tropical race 4 (TR4) is a major problem for Cavendish banana growing areas. Basrai (Dwarf Cavendish) is the major cultivated variety in Pakistan and now recently been reported to be affected by Foc TR4 in certain areas in the Sindh province. To genetically characterize, three independent isolates (P.TH1, P.TH2 and P.Th3) were sampled from different fields in district Thatta and fungus was isolated on potato dextrose agar. The pure fungal isolates were used to establish Koch's postulates by testing their pathogenicity on tissue cultured Cavendish banana. A diagnostic PCR assay was optimized and used to sequence a reported molecular marker for specific detection of Foc TR4 and to sequence 28S-18S ribosomal RNA intergenic spacer region (IGS) from these local isolates. The phylogenetic of Pakistani isolates suggests that they belong to previously characterized lineage V of tropical race 4 of F. oxysporum cubense with 99% bootstrap support and show close relationship with Indonesian and Malaysian Foc TR4 isolates. The rapid spread of this disease in different banana growing areas of the Sindh is alarming and necessitates effective control of this through chemical and biocontrol, if remains unchecked, Foc TR4 can raise havoc to banana industry in Pakistan and would be devastating economically. [ABSTRACT FROM AUTHOR]