Pathogenic and Molecular Confirmation of Fusarium sacchari Causing Wilt in Sugarcane

Wilt of sugarcane is a serious disease affecting sugarcane production in many sugarcane growing regions. Since the associated pathogen has not been clearly established with the disease, detailed studies were conducted to identify the fungal species by pathogenicity and molecular variation. Selected 10 isolates of Fusarium associated with sugarcane wilt were tested for their pathogenicity on the cv Co 86032 and among them the isolates Fs 032 TN4L2 and Fs 121 UP1 originated from Tamil Nadu and Uttar Pradesh, respectively had shown severe disease and proved to be more virulent. Also pathogen inoculation by plug method combined with abiotic stress on selected sugarcane varieties at Coimbatore, caused typical wilt symptoms in cvs Co 6304 and Co 86249 and partial symptoms on CoC 90063 and CoC 92061 under field conditions. However, disease at endemic location in Gujarat the cvs Co 86002, Co 95020, Co 97008, Co 98010 and Co 0323 exhibited typical wilt in response to pathogen inoculation by plug method. Further studies on molecular variation using specific RAPD and ISSR markers were taken up to confirm the pathogenic isolates of Fusarium . The molecular markers such as 1000 bp fragment of RAPD primer OPA13, 650 bp fragment in ISSR1, 720 bp fragment in ISSR5 and 880 bp fragment in ISSR9 very clearly demarcated pathogenic and nonpathogenic isolates. The field and laboratory studies very clearly confirmed that the wilt pathogenic isolates belong to F. sacchari and this is the first attempt that generated molecular markers which correlated with pathogenicity of F . sacchari isolates.