Resistance of american cottons to fusarium wilt in India

Summary

• 1. It is a well-known fact that Indo-American cottons are immune toFusarium wilt in India.

• 2. These cottons as well as the recently introduced American varieties also proved to be immune to an American strain of the fungus when growing in Indian soils.

• 3. The Indo-American cottons were tested in America on American cotton soils and there they proved to be as susceptible as the American cottons to the American strain of the fungus, but they were still immune to the Indian fungus.

• 4. The American and the Indian strains ofF. vasinfectum show, therefore, a very strict parasitic specialisation, the American form being unable to attack Indian cottons in any circumstances, andvice versa.

• 5. Indian cottons grown on American cotton soils are much less susceptible to the Indian form than when they are in India.

• 6. American cotton soils where wilt is common, are light, sandy and acidic but the Indian cotton soils where wilt is predominant are heavy, clayey and alkaline. The above experiments strongly suggest that the reason the IndianFusarium weakly attacks its Indian host in American soils and the AmericanFusarium is almost non-pathogenic to its American and Indo-American host in Indian soils, is to be sought for in the fact that these soils have different texture and reaction.