1 Potato Experimental at Trial Centre, Shillong-9 (Meghalaya).
2 I. C. A. R. Complex for N. E. Region. Amrit Bhavan, Shillong-4. (Meghalaya).
Nine high spectrum physiologic races of Phytophthora infestons (Mont.) de Bary with 4; 5; 6; and 7 genes for pathogenicity were identified in Khasi hills district of Meghalaya (India). Role of these races in breaking ‘R-gene’ resistance of potato cultivars has been inferred. The possible mechanisms of physiologic specialisation under Khasi hills condition have been discussed and use of varieties having only horizontal resistance to the late blight pathogen has been indicated in order to reduce its pathogenic variability.
