Relation of nitrogen fertilizers and manure to vascular wilt of egyptian cotton caused by four fusaria species and strains

Abstract

Four different species and strains ofFusarium, namely,F. oxysporum f.vasinfectum (Atk.)Snyder &Hansen,F. solani (Mart.)App. &Wr.,F. vasinfectum (Atk.) f1Wr. strainFahmy, andF. vasinfectumAtk. are responsible for cotton wilt in U.A.R. Pathogenicity experiments have shown that the four experimentalFusaria possess varying degrees of pathogenicity towards two susceptible cotton varieties, namely, “Karnak” and “Bahtim 190”. On the other hand, “Ashmouni” cotton proved resistant to the fourFusaria. Variability of pathogenicity of the experimentalFusaria is not only related to host cotton plant or parasite, but also to nitrogenous fertilizer or manurial treatment of the soil. Resistance of “Ashmouni” cotton was not broken in presence of sodium nitrate, ammonium nitrate or stable manure added to soil inoculated with any of the fourFusaria. The application of nitrogen fertilizers or manure resulted on the whole, in increased wilt-disease incidence of the susceptible cotton varieties. Stable manure enhanced predisposition to vascular-wilt more than other nitrogen treatments, especially in presence of the virulentF. oxysporum f.vasinfectum or both strains ofF. vasinfectumAtk. Ammonium nitrate induced the sudden appearance of mottling characteristic of vascular-wilt of cotton when “Bahtim 190” plants were raised in nitrogen-fertilized soil inoculated withF. solani (Mart.)App. &Wr. At the same time, the raised affected plants showed increased growth-vigour and enhanced maturity of their leaves.