STUDIES ON FUNGICIDAL ACQUIRED RESISTANCE OF ALTERNARIA SOLANI ON TOMATO

Abstract

Since tomato can be grown in Egypt year round , it can be considered one of the most important expo1t vegetable crops. Tomato is subject to many diseases which reduce the quantity and quality of the )ield. Tomato early blight disease caused by Alternaria solaui, is considered one of the most destructive diseases. Chemical control is considered the most effective way to control this

disease, however, in the last years many problems have arisen with the constant use of f1mgicides. One of the most recent problems which attract attention of the plant pathologists has been development of strains of different plant pathogens resistant to different fungicides. Since fungicides are likely to continue to be the mainstay of disease management all over the world for the foreseeable future, effective control of plant disease requires effective management of f1mgicide resistanc,e in the pathogen population. The work aimed to illiminate the problem of acquired 1•esistance in the

natural populations of Alternaria solaui the causal organism of early blight disease of tomato, in different governorates in Egypt, El-Behera, El-Sharkcya, El-Ismaelia, Souhage, El-Fayoum,EI-Giza, Bani Swif and Sinai. 1- F1mgicidal resistance of Altrnaia so/ani isolates:

The eight Alternaria sola11i isolates representing eight governorates, were tested for their resistance to 4 fungicides, representing the different fungicide groups to which belong most of the fungicides used to control early blight disease. 1- A- Resistance to Dithiocarbamate compounds.

1- A.a - Resistance of mycelium.

All the eight isolates representing the eight governorates can be considered sensitive to slightly resistant. The EC 50 ranged from 31 to 97 ppm.