248 BREEDING CROP PLANTS 



need not be repeated here. Yield, quality, and disease resistance 

 are the three most important economic characters. To bring 

 about a desirable combination of these characters, both selection 

 and hybridization have been practiced. 



Selection has been used by Edgerton (1918), of the Louisiana 

 Agricultural Experiment Station, to isolate tomatoes resistant 

 to wilt (Fusarium lycopersici) . The improved technic followed 

 is worthy of consideration. Seeds of a particular variety were 

 planted in soil which had been sterilized previously and then 

 inoculated with a pure culture of the wilt-producing organisms. 

 When seedlings showed wilt infection they were pulled and dis- 

 carded. Only plants which showed resistance were transplanted 

 to the field. Tomatoes had grown continuously for eight or ten 

 years on this field and it was known to be heavily infected with 

 the wilt fungus. The use of this method permits a smaller 

 acreage and insures the contact of each plant with the wilt 

 organism. A selection made from a row of Acme grown in 1909 

 named " Louisiana Wilt-Resistant" was extremely wilt resistant 

 but possessed other characters which made it undesirable for 

 Louisiana conditions. Selections from the progeny of crosses 

 between this form and Earliana showed considerable promise. 



Durst (1918) reported the result of five years' selection for 

 resistance to Fusarium of tomatoes. Varieties were found to 

 differ a great deal in their resistance and unfortunately the most 

 resistant ones produced poor fruit. After five years, some of the 

 better strains stood up in soil which proved fatal to the original 

 varieties. In addition to disease resistance, the selections also 

 showed good yielding ability. Of seventy-four lots grown one 

 year the highest fourteen yields were produced by selected 

 strains. 



Whether selection alone or hybridization and selection together 

 are to be used as a means of improving a crop is dependent upon 

 the nature of the material. If the character combination is not 

 already present, the only practical means of bringing it about 

 is crossing followed by selection. 



Cross-Fertilized Vegetables 



Crops have previously been classified as belonging to four 

 groups according to their mode of reproduction. Cross-fertilized 

 vegetables may be roughly divided into three main divisions; 



