Haploid plants of solanum demissum

Abstract

THE wild hexaploid (2n = 72) species Solanum demissum Lindl. has been widely used in breeding for blight (Phytophthora infestans) resistance in potatoes. Crossed with cultivated S. tuberosum varieties (tetraploids with a chromosome number of 2n = 48) it gives pentaploid (2n = 60) hybrids which can be back-crossed by S. tuberosum. An alternative method of breeding has been suggested by Black1. This consists of crossing S. demissum with a diploid (2n = 24) species such as S. Rybinii to get a tetraploid (2n = 48) F1 hybrid, which is then crossed with S. tuberosum varieties. This latter method appears to have much to recommend it, particularly as Thomas 2 states that, in the hybrid S. demissum × S. Rybinii and in the triple hybrid (S. demissum × S. Rybinii) × S. tuberosum, "chromosome differentiation between these related species is not sufficient to affect pairing to any extent". This presumably means that, at least in the triple hybrid, about twenty-four bivalents are formed at meiosis. © 1950 Nature Publishing Group.