Some notes on the relations between field resistance to Phytophthora infestans in leaves and tubers and ripening time in Solanum tuberosum subsp. Tuberosum

Abstract

A survey is made of the correlations between three characters, viz. field resistance of the foliage and of the tubers to Phytophthora infestans and ripening time. The relation between resistance of the foliage and ripening time is so close, that to all appearances it seems to be difficult to combine earliness with a high degree of resistance. This conclusion holds true only for the subspecies tuberosum of Solanum tuberosum and the breeder must draw some optimism from the possibility that this close correlation can be broken by the use of wild and cultivated South American and Mexican material.

There is not such a close correlation between ripening time and tuber resistance. From some preliminary experiments the impression is gained that the skin of the tuber is an important barrier for the penetration of the fungus into the tuber in many cases. However, the defence reactions of the flesh are also instrumental in determining of degree of field resistance.