Search Results
Abstract
The inheritance of resistance to curly top virus in the tomato breeding line C5 was studied in 5 field trials and a greenhouse seedling test. Comparisons in curly top incidence were made between susceptible commercial parents, the resistant parent C5, and F1, F2, backcross-resistant, and backcross-susceptible progenies. Results suggest that resistance in C5 is controlled by 2 duplicate, incompletely dominant genes probably with modifiers. Plants that contain both genes have the ability to escape infection with CTV until harvest 70 to 100% of the time, depending on the severity of curly top exposure.
Abstract
Potatoes (Solanum tuberosum L.) normally are propagated vegetatively by tubers and produce a uniform, productive, high-quality crop. However, tubers accumulate systemic diseases, which greatly reduce their productivity and quality. Many countries control these diseases with complex and expensive seed certification programs. Such control methods are not available in many other countries where potatoes are an important part of the diet.
Abstract
Mist, low light, and low temperature during dormancy significantly promoted subsequent floral bud growth in peach (Prunus persica L. Batsch) while high temperature and high light intensity significantly decreased it. Chilling hours at 10°C bud temperature were half as effective as hours at 6°. No significant changes occurred in abscisic acid (ABA) levels in floral bud scales. ABA content of primordia within misted buds was significantly lower than of primordia in other treatments. The data support the concept that fog influences bud rest through temperature, light, and leaching effects. Results also indicate that ABA content in buds may not be the primary factor that determines termination of rest.
Photosynthetic lighting is one of the main costs of running controlled environment agriculture facilities. To optimize photosynthetic lighting, it is important to understand how plants use the provided light. When photosynthetic pigments absorb photons, the energy from those photons is used to drive the light reactions of photosynthesis, thermally dissipated, or re-emitted by chlorophyll as fluorescence. Chlorophyll fluorescence measurements can be used to determine the quantum yield of photosystem II (ΦPSII) and nonphotochemical quenching (NPQ), which is indicative of the amount of absorbed light energy that is dissipated as heat. Our objective was to develop and test a biofeedback system that allows for the control of photosynthetic photon flux density (PPFD) based on the physiological performance of the plants. To do so, we used a chlorophyll fluorometer to measure ΦPSII, and used these data and PPFD to calculate the electron transport rate (ETR) through PSII. A datalogger then adjusted the duty cycle of the light-emitting diodes (LEDs) based on the ratio of the measured ETR to a predefined target ETR (ETRT). The biofeedback system was able to maintain ETRs of 70 or 100 µmol·m−2·s−1 over 16-hour periods in experiments conducted with lettuce (Lactuca sativa). With an ETRT of 70 µmol·m−2·s−1, ΦPSII was stable throughout the 16 hour and no appreciable changes in PPFD were needed. At an ETRT of 100 µmol·m−2·s−1, ΦPSII gradually decreased from 0.612 to 0.582. To maintain ETR at 100 µmol·m−2·s−1, PPFD had to be increased from 389 to 409 µmol·m−2·s−1, resulting in a gradual decrease of ΦPSII and an increase in NPQ. The ability of the biofeedback system to achieve a range of different ETRs within a single day was tested using lettuce, sweetpotato (Ipomoea batatas), and pothos (Epipremnum aureum). As the ETRT was gradually increased, the PPFD required to achieve that ETR also increased, whereas ΦPSII decreased. Surprisingly, a subsequent decrease in ETRT, and in the PPFD required to achieve that ETR, resulted in only a small increase in ΦPSII. This indicates that ΦPSII was reduced because of photoinhibition. Our results show that the biofeedback system is able to maintain a wide range of ETRs, while it also is capable of distinguishing between NPQ and photoinhibition as causes for decreases in ΦPSII.