72 MASS. EXPERUIENT STATION BULLETIN 378 



DEPARTMENT OF FLORICULTURE 

 Clark L. Thayer in Charge 



Breeding Snapdragons for Varietal Improvement and Disease Resist- 

 ance. (Harold E. White, Waltham.) Back-crossing and selection work 

 is being continued with the Field Station rust-resistant strains. Green- 

 house varieties of snapdragon, Lucky Strike, Afterglow, New Cincinnati, 

 Laura, Cheviot Maid, Rose Orange, Bronze Queen, Cornwallis, and 

 Rose Queen, were observed to be very susceptible to rust disease under 

 field conditions. When such varieties were intercrossed, the progeny of 

 the F] and Fj generations continued to show a high degree of susceptibility 

 to rust. However, the Fs generation selections, particularly from a cross 

 between Lucky Strike and Afterglow, showed definite resistance to rust 

 disease. This is an unusual situation in that the existence of natural re- 

 sistance in susceptible commercial varieties of snapdragons has not been 

 definitely proved. The explanation offered for this type of resistance to 

 rust is that these varieties must carry modifying genetic factors which, 

 under conditions of intercrossing and inbreeding, permit a more complete 

 expression of the resistance factor. The nature of this type of resistance 

 and the extent to which it can be developed by breeding must be de- 

 termined by further work. 



Wilt disease (Verticillium) continues to be destructive to snapdragons 

 in the field, though of rare occurrence under greenhouse conditions. 



Effect of Plant Nutrients, Soil Reaction, and Light on Gardenias. (Har- 

 old E. White, Waltham.) Previous experiments were concerned with the 

 effects of different nitrogenous fertilizer materials on flower production, 

 bud drop, and iron chlorosis. This type of work has been continue<l with 

 three phosphate fertilizer materials to determine whether readily available 

 phosphoric acid, as compared to less available forms, had any specific 

 eflfect on growth of gardenia plants. Additional phosphoric acid in the 

 form of bone meal, precipitated bone, and superphosphate (16 percent), 

 applied to soils in sufficient quantities to supply 320 pounds P2O6 per acre, 

 affected flower production appreciably. 



Yields on untreated plots were 20.16 flowers per plant; on plots receiv- 

 ing precipitated bone, 22.39; bone meal, 20.91; and superphosphate, 17.19 

 flowers per plant. 



Bud drop was perceptibly greater on plants given organic forms of 

 phosphoric acid. Untreated plants showed 33.88 percent bud drop; those 

 receiving applications of precipitated bone sliowed 34.70 percent; hone meal, 

 39.40 percent; and superphosphate, 29.30 percent bud drop. 



Symptoms of chlorosis due to a lack of iron were definitely more severe 

 on plants that received superphosphate than on those given either bone 

 meal or precipitated bone. 



Cultural Requirements of Freesias. (Harold E. White, Waltham.) 

 Freesia conns dried or precured for 28 days and planted September 14, 

 1939, required 155 days to reach the flowering stage, as compared to 165 

 days for untreated corms planted on August 17. Cornis dried for 9 weeks 

 and planted October 19 flowered in 130 days. The number of days neces- 

 sary for Freesias to reach the flowering stage decreased in proportion to 

 the lateness of planting, but the actual date of bloom was not affected 

 by precuring treatments. Corms untreated and planted August 17 bloomed 



