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Use of GUS Transformants of Fusarium subglutinans for Determining Etiology of Mango Malformation Disease

Fusarium subglutinans has been associated with mango floral and vegetative malformation, although confusion exists regarding the etiology of the disease. A wild-type isolate of F. subglutinans causing mango malformation disease was transformed with the GUS (β-glucuronidase) reporter and hygromycin resistance genes. Five stable transformants were isolated containing varying copy numbers at different integration sites. Specific GUS activity was quantified for the transformants, whereas no activity was recorded for the wild-type isolate. The transformants and the wild-type isolate were inoculated into healthy mango floral and vegetative buds. Typical symptoms of misshapen shoots with short internodes, stubby leaves, and bunchy, malformed inflorescences were observed 6 to 8 weeks following inoculation. The presence of GUS-stained mycelium of the pathogen viewed microscopically within infected plant organs provided unequivocal evidence that F. subglutinans is indeed a causal agent of mango malformation disease.