Dry matter content of apical and basal portions of Russet Burbank potatoes
Studies were made over a 4-year period of some factors affecting the dry matter content of the apical and basal portions of growing Russet Burbank potatoes. The greatest difference between portions was obtained from tubers of the normally irrigated plots of 1969. The amounts in the two portions in 1970 were nearly equal throughout the growing season. The major differences between the 2 years was a slightly cooler June and warmer maximum temperatures in July of the 1970 growing season. Moisture stress, particularly, early in the stage of tuber development (1972 season) caused a switch in amount of dry matter in the apical and; basal portions. Stress later in the development stage (1969 season) did not cause a switch. Fertility level was not as influential as moisture stress in affecting the ratio of dry matter in the two ends, whether under stress or normal moisture conditions.
The variation in reducing sugar content in different varieties of potatoes
Potatoes that are stored at temperatures below 4 0 ° F tend to accunmlate sugars, which impart a sweet taste when eaten and which cause an off-color and off-flavor when cooked or processed. At least two major approaches to eliminate the problem seem possible, (1) the prevention of a build-up of sugars and (2) the elimination of the sugars after they have accumulated. Considerable work has been done to eliminate reducing sugars after they have accumulated such as the use of conditioning temperatures after storing (14), (17), (18), (19), and the leaching of the soluble sugars from the tissue by various chemical or water baths prior to processing, (11), (13). Considerable study has aiso been directed toward the prevention of the accumulation of reducing sugars, by the application of sprout-inhibiting chemicals, along with a storage temperature higher than is normally considered to be the sprouting telnperature for potatoes, (10), (16). A nmnber of workers (2) , (3) , (4) , (5) , (6) , (7) , (9) , (12, (19) have studied the variations in reducing sugar content occurring in different commercially important varieties of potatoes, but as far as the authors have been able to ascertain no one has attempted a survey of the differences in reducing sugar content which occur in unnamed seedlings which are used in every potato breeding and testing program. Because of the importance of high reducing sugar in potatoes to the n:anufacturer of potato products, it seemed worth while to determine the vara t ion in reducing sugar content which might .exist between commercial potato varieties and unnamed seedling varieties in an effort to find parent n:aterial which could be use:l in a potato breeding program designed to develop a variety which would not accumulate excessive amounts of reducing sugars while in storage.
Immune dysfunction following infection with chicken anemia agent and infectious bursal disease virus. II. Alterations of in vitro lymphoproliferation and in vivo immune responses.
To determine the functional impact of alterations in lymphocyte concentrations and ratios following infection with chicken anemia agent (CAA) alone or in combination with infectious bursal disease virus (IBDV) on the immune system of young chickens, in vitro lymphoproliferation assays and in vivo responses to vaccination with several common viral agents were assessed at various time intervals post-inoculation (PI). Concanavalin A (Con A), phytohemagglutinin (PHA) and pokeweed mitogen (PWM) stimulation of splenic lymphocytes (SPL) collected from control birds could not be detected until 10-14 days PI. Infection with CAA was characterized by significantly higher PWM stimulation of SPL at 17 days PI and significantly lower PWM stimulation of peripheral blood lymphocytes (PBL) at 14 days PI, compared with uninfected controls. Concanavalin A and PWM stimulation of SPL was significantly increased in birds inoculated with IBDV alone. Lymphocytes harvested from birds inoculated simultaneously with CAA and IBDV had significantly lower responses. Effects on humoral and cell-mediated immunity following CAA and/or IBDV were determined by evaluating vaccination responses to Newcastle disease virus (NDV), fowl pox virus (FPV) and infectious laryngotracheitis virus (ILTV) during the acute phase of CAA infection (2 weeks PI). Vaccination of birds 2 weeks following CAA infection at 1 day of age resulted in decreased protection against NDV (85.7%) and ILTV (7.1%) challenge compared with protection rates in control birds (100% and 53.3% respectively). Infectious bursal disease virus infection was associated with decreased protection against NDV (60%) only. Concomitant infection at 1 day of age resulted in a greater reduction in NDV challenge protection (33.3%), slightly decreased FPV protection (87.5%), increased numbers of persistent FPV vaccination lesions and increased protection against ILTV challenge (71.4%). Vaccination of birds 2 weeks following CAA infection at 2 weeks of age resulted in slightly decreased NDV humoral antibody, development of persistent FPV vaccination lesions (17%) and increased immunity to ILTV challenge compared with control birds (83.3% vs. 66.7%). Chickens inoculated with IBDV alone displayed a more severe depression in NDV antibody titers and only a slight decrease in ILTV protection. Vaccination following concomitant infection at 2 weeks of age resulted in a higher percentage of FPV persistent vaccination lesions (39%) and greatly enhanced immunity to ILTV challenge (100%).