44 MASS. EXPERIMENT STATION BULLETIN 417 



DEPARTMENT OF FLORICULTURE 

 Clark L. Thayer in Charge 



Disease Resistance and Heredity of Carnations. (Harold E. White, Waltham.) 

 Flower petal counts made on blooms from 42 varieties of carnations show that 

 there is considerable variation in the number of petals per bloom within a variety*. 

 A few varieties were very consistent in the number of petals per flower produced. 

 When the varieties were grouped for comparison on the basis of average number 

 of petals, 40 percent had an average count of 25 to 50 petals; 35 percent, 50 to 

 60 petals; and 24 percent, 60 to 80 petals per flower. The variety Silveryln had 

 the highest average number of petals, 97 per bloom. 



Flowers with split calyces were not abundant enough for an accurate analysis 

 of petal number as related to splitting, but material available for inspection re- 

 vealed no correlation between number of petals present and degree of splitting. 

 Extra floral parts such as ovules were found in both normal and split flowers; but, 

 as extra ovules occurred very frequently in both types of flowers, such a condition 

 could not be associated with the splitting character in commercial varieties. 



Some 500 progeny were obtained from crosses made between disease-resistant 

 and susceptible varieties, but data as to the hereditary nature of the disease 

 resistance are not sufficient for analyses. The progeny segregated for two types 

 of double flowers: 50 percent commercial doubles (normal) and 25 percent bursters 

 (abnormal doubles) ; and 25 percent were singles. The data seem to indicate 

 that splitting of calyces is of two types. One, due to specific hereditary factors, 

 induces formation of an abnormal number of extra buds and multiplicity of 

 floral parts within the individual blooms. Dissection of a number of the bursters 

 produced in the seedlings showed that there were from 100 to 150 petals present 

 and 5 to 10 immature ovules per bloom. The second type of splitting occurs in 

 variable degrees with commercial varieties and would seeni to be influenced more 

 by environmental factors than by heredity. 



Cotyledon number of seedling carnations varies from two to three and the 

 seedling leaf character segregates in a 1 to 1 ratio. No structural characteristics 

 were observed to be associated with difference in cotyledon number. 



Breeding Snapdragons for Varietal Improvement and Disease Resistance. 



(Harold E. White, Waltham.) Trials of eight Waltham Field Station strains of 

 rust-resistant snapdragons with Yoder Brothers in Barberton, Ohio, showed the 

 strains to be highly resistant to rust and valuable for outdoor culture as well as 

 worthy of inclusion in the firm's hybridizing work with snapdragons. 



Provisions were made for more extensive tests of the rust-resistant qualities 

 of these strains by distribution of seed to eight expeririient stations and one seed 

 firm in this country. Requests for trials wiere received from Pretoria, South 

 Africa, and Victoria, Australia. 



The rust-resistant character of the strains has shown no indication of breaking 

 down, and no mutant strains of the rust fungus have been observed. Selected 

 inbred lines have been back-crossed to determine possibilities of hybrid stock 

 for commercial flower production use. A large-flowered pink strain has been 

 developed which shows much promise as a winter-blooming greenhouse variety. 



Complete information and results on hereditary phases of the breeding work 

 on this project have been published as Massachusetts Agricultural Experiment 

 Station Bulletin 400, February, 1943. 



