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Improved germination under unfavorable soil conditions is an important safeguard against yield losses in direct-seeded crops. Osmoprimed seed has been shown to provide earlier and more uniform germination as well as improve low temperature germination. These attributes combined with the reduced rates of damping-off associated with Pseudomonas aureofaciens AB254 creates a bioosmopriming seed treatment that provides rapid germination under a wider range of soil temperatures while exhibiting the disease resistance and improved growth associated with bacterial coatings. The objective of this work is to combine biopriming and osmopriming into one procedure, thus creating an environment for adequate seed hydration and rapid multiplication of beneficial bacteria which will thoroughly colonize the seed surface. Processing tomato seeds (Lycopersicon esculentum Mill. `OH8245') were bio-osmoprimed in aerated –0.8 MPa NaNO3 at 20°C for 4 days. On the fourth day, a mixture of nutrient broth, a defoaming agent, and bacteria that have been adjusted to the same osmotic potential is added. This is done so that the removal of seeds from the tank at the end of the 7-day treatment coincides with peak populations of bacteria. Pseudomonas aureofaciens AB254 multiplies very rapidly in this environment, with colony forming units for tomato averaging 4 × 105/seed. Results will also be reported for cucumber seed (Cucumis sativus L. `Score'), which were treated using a similar procedure. Bacterial populations per seed, germination characteristics and pathogen control will be discussed.
Osmopriming has been shown to enhance seed performance by increasing germination rates and uniformity. Furthermore, these enhancements persist under less-than-optimum conditions, such as salinity, reduced water availability, and excessively high or low temperatures. Additional benefits include resistance to soil pathogens due to lower leachate levels and more rapid emergence. To augment these existing qualities, it would be advantageous to incorporate beneficial organisms that antagonize soil-borne diseases, combining the benefits of both systems into a single procedure. To accomplish this, processing tomato seeds (Lycopersicon esculentum Mill. OH8245) were bioprimed in aerated –0.8 Mpa NaNO3 at 20°C for 4 days, at which time a mixture of nutrient broth, a defoaming agent, and beneficial bacteria that has been adjusted to the same osmotic potential is added. The bacteria used, Pseudomonas aureofaciens AB254, has been proved to control Pythium ultimum on a variety of crop seeds. After 7 days the seeds are removed having been primed and colonized with 105 colony forming units (cfu)/seed. In the absence of pathogen pressure, osmoprimed and bio-osmoprimed seeds performed similarly improving overall germination by 40% after 3 days, as well as low temperature (10–15°C) germination. However, when these seeds were sown in soilless media inoculated with P. ultimum, osmoprimed and bio-osmoprimed emergence was 57% and 74%, respectively, showing the improvements that these biologicals can provide. Thermogradient table results, storage tests, cfu/seed, and pathogen control will be discussed.
Abstract
The original ‘Brooks’ cherry (Prunus avium L.) seedling was evaluated at the Wolfskill Ranch of the University of California, Davis from 1970 to 1985. Clones of the original seedling have been evaluated for fruit quality in Contra Costa County since 1978 and in Fresno County at the University's Kearney Agricultural Center since 1981. ‘Brooks’ registered its most outstanding performance at the Kearney Field Station.
Abstract
The effects of pH and temperature were determined on NAA sorption by enzymatically isolated tomato (Lycopersicon esculentum Mill. cv. Sprinter) fruit cuticles. Both cuticular membranes (CM) and dewaxed CM (DCM) sorbed more NAA at pH 2.2 than at pH 6.2. At each pH, increasing temperature (15° to 35°C) decreased NAA sorption by both CM and DCM. The same qualitative temperature (5° to 25°) response was observed with 2,4-D for CM at low (0.8) pH. Chemical names used: 2-(1-naphthyl)acetic acid (NAA); (2,4-dichlorophenoxy)acetic acid (2,4-D).
14C-urea penetration of isolated tomato (Lycopersicon esculentum Mill. cv. `Pik Red') fruit cuticular membranes (CM) was studied as a function of concentration and temperature. There was no significant effect of cuticular wax on urea penetration at 25C, permeances for the CM being 8.4 × 10-10 and dewaxed CM (DCM) 11.1 × 10-10·m·s-1. Time lags were near zero for both CM and DCM. Steady-state diffusion analysis suggests that the relatively low cuticular permeance of urea is due to low partitioning that offsets high diffusivity. Urea flux through the CM and DCM showed ≈1.5- and 1.9-fold increases, respectively, for each 10C increase between 5 and 45C. Urea flux across CM and DCM increased linearly with concentration (10 μm to 1 m) and, thus, was a first-order process.