The improvement of tomatoes by selection

Abstract does not appear. First page follows.

Introduction

Although the numerous present-day varieties of tomatoes have been developed in the last 75 years from forms with smaller and less desirably-shaped fruits, the history of the evolution of our cultivated forms is obscure. As Bailey⁽¹⁾ has pointed out, the extremely large fruit-size of certain cultivated forms is generally associated with that type of fasciation known as synanthy. Whereas the number of loculi or cells in the fruit of the small-fruited and doubtless more primitive forms, such as Red Cherry, is from two to three, in the large fruited varieties, such as Trophy and Ponderosa, the number is from 15 to 20. According to Warren⁽¹²⁾ fasciation of fruit is determined by the recessive allelomorphs of two dominant Mendelian factors which inhibit fasciation. On this hypothesis the fasciated condition has presumably arisen by gene mutations.

It is generally believed that in the later development of the tomato, selection has played an important role, though the literature on this subject is meager. Myers⁽⁸⁾ reports that in some instances the general character of the fruit produced by the progeny of single plant selections of Earliana and Matchless was less desirable than that of the original selection, but in others some improvement was recorded. Using statistical methods, Myers found that the progenies of selections were less variable than the parent variety. Later, this author reported that there was no cumulative improvement through further selection and that the original selection was the important one.