In vitro and ex vitro Selection of Potato Plantlets for Resistance to Early Blight

Reaction to the culture filtrate of Alternaria solani (Sorauer) was used as an indicator in an in vitro screening test to select lines with decreased field susceptibility to early blight from a population of 1000 putative mutants. Plantlets of cv. Desire´e derived from irradiated callus of potato were inoculated in vitro with a culture filtrate of A. solani (Sorauer). Of the 45 lines selected and subsequently evaluated under conditions of natural infection in the greenhouse six showed lesser degrees of early blight infection than the cv. Desire´e control. The six lines selected in the greenhouse retained lower degrees of infection during 2 years of field trials.