Geographical Distribution, Host Range and Genetic Diversity of <i>Fusarium oxysporum</i> f. sp. <i>cubense</i> Causing <i>Fusarium</i> Wilt of Banana in India

<i>Fusarium</i> wilt of banana is a major production constraint in India, prompting banana growers to replace bananas with less remunerative crops. Effective disease management practices thus need to be developed and implemented to prevent further spread and damage caused by <i>Fusarium oxysporum</i> f. sp. <i>cubense</i> (<i>Foc</i>), the cause of <i>Fusarium</i> wilt. Currently, knowledge of disease incidence, affected varieties, and the geographical spread of <i>Foc</i> races in India are only scantily available. An extensive field survey was conducted in 53 districts of 16 major banana-growing states of and one union territory of India that covered both tropical and subtropical regions. Disease incidence ranged from 0 to 95% on farms, with Cavendish bananas (AAA) most affected. No <i>Fusarium</i> wilt symptoms due to <i>Foc</i> R1 were observed in Nendran (AAB) or Red Banana (AAA) in South India. During the survey, 293 <i>Foc</i> isolates were collected from Cavendish, Pisang Awak (ABB), Silk (AAB), Monthan (ABB), Neypoovan (AB), and Mysore (AAB) bananas. Isolate diversity was assessed through Vegetative Compatibility Group (VCG) analyses, sequencing of EF1α gene sequences, phylogenetic analyses, and characterisation by <i>SIX</i> gene composition. Thirteen VCGs were identified, of which VCGs 0124, 0125, 01220, and 01213/16 were dominant and infected Cavendish bananas. Phylogenetic analysis divided the Indian <i>Foc</i> isolates into race 1 (R1), subtropical race 4 (STR4), and tropical race 4 (TR4). <i>Secreted in Xylem</i> (<i>SIX)</i> gene analyses indicated that the effector genes <i>SIX</i>4 and <i>SIX</i>6 were present in the VCGs 0124, 0124/5, 0125, and 01220 of race 1, <i>SIX</i>7 was present only in <i>Foc</i> STR4, and <i>SIX</i>8 was found only in <i>Foc</i> R4 (TR4 and STR4) isolates. Insights into the geographical distribution of <i>Foc</i> races, and their interactions with banana varieties, can guide integrated disease management intervention strategies across India.