Resistance of Potato Tubers (Solanum tuberosum) to Phoma exigua var. exigua and Phoma exigua var. foveata

Abstract

A histological study of the development of lesions caused by P. exigua var. exigua and P. exigua var. foveata was made in immature tubers of potato cv. Brownell at 18, 10 or 2°C and in mature tubers of cv. Brownell and Bismark at 10°. At 10 and 18°, lesion development was arrested in both cultivars and maturities. Evidence indicated that suberization and lignification are involved in the retardation and arrest of lesions.

Both rishitin and phytuberin were produced in response to infection by P. exigua var. exigua and var. foveata. It is unlikely that rishitin and phytuberin are important in the resistance of tubers to Phoma exigua varieties in cultivar Bismark or in immature tubers of cultivar Brownell. In mature tubers of cultivar Brownell the concentration of phytuberin induced in response to P. exigua var. exigua and var. foveata was c. 20-fold higher than the concentration of rishitin. The possible signifi- cance of phytuberin in these interactions is discussed.