Hybrids Between Lycopersicon Esculentum Mill. And Solanum Lycopersicoides Dun

Abstract

The garden tomato (Lycopersicon esculentum Mill.) has been successfully hybridized with all other species of Lycopersicon that have been grown for experimental purposes.' 2 Its crossability relations with the large parent genus, Solanum, on the other hand, are largely-unknown, although a strong barrier to crossing with certain species might be inferred from the following observations. Solanum melongena, S. muricatum, S. nigrum, S. tuberosum, and other species, especially of the tropics, are often grown close to tomatoes, or are found as weeds in tomato fields. Despite this opportunity for crossing, spontaneous hybrids between the tomato and these species have apparently never appeared, and apparently no such hybrid has been produced artificially. The present example of a tomato-night-shade hybrid was encountered in an exploratory survey of the relations between the two genera. The tomato parent of the hybrids is Pearson, the leading variety of the California tomato industry. It is typical of the standard or normal-type L. esculentum in the genetic sense except that it is homozygous for the sp gene, which conditions determinate plant habit. The nightshade parent is Solanum lycopersicoides Dun., a perennial native to the south coast of Peru. It has been classed by Bitter3 in the section Tuberarium, the group pf Solanum species usually considered to be most closely allied to the tomatoes.4 Even among species of this section, S. lyccpersicoides shows a unique resemblance, as its name implies, to the tomatoes in such characteristics as its yellow flowers, nature of leaf dissec-tion, and lack of tubers. Taxonomically S. lycopersicoides is a true Solanum in having the following features that distinguish it clearly from Lycopersicon: its anthers lack sterile tips, dehisce terminally and do not join laterally to each other to form an anther tube. Plants of S. lycopersicoides were acquired5 as collection No. 30382 of the University of California Botanical Garden Third Expedition to the Andes, 1942. Seeds had been collected near Candarave, Peru (Dept. Tacna, Prov. Tarata). Plants in cultures at Davis resemble very closely the herbarium specimen of the original collection (Spec. No. 695,139 of the University of California Herbarium). The F, hybrids between these two species were obtained with considerably greater ease than those between L. esculentum and L. peruvianum (L.) Mill.