Cross infection and genetic diversity of Fusariumoxysporum f. sp. cubense, the casual agent of Fusarium wilt in banana.

Fusarium wilt, caused by Fusarium oxysporum f. sp. cubense (Foc), is posing a serious threat to banana production in India. Out of 234 Foc isolates collected from different parts of India, 100 representative isolates were subjected to cross reaction as well as diversity analyses. In-vitro cross reaction tests involving different nit-1 testers of Foc race 1 and race 2 indicated that there was a cross reaction between race 1 and race 2 Foc isolates in many cases. Validation carried out under pot culture conditions also confirmed the cross reaction between the members of Foc race 1 and race 2. For diversity analyses, VCG analyses were carried out using the local nit-M testers. The result showed the presence of nine different VCGs in India. The molecular characterisation of Foc isolates by PCR-RFLP analysis of rDNA IGS region, using six restriction enzymes grouped the Indian Foc isolates into 13 IGS genotypes. Among these, group 1 (AAAAAA) was the most common and consisted of 44 isolates of pathogenic Fusarium