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R.S. Utkhede and E.M. Smith

A 10-year field experiment was conducted on 20-year-old apple trees (Malus domestica Borkh.) inoculated with Phytophthora cactorum (Leb. & Cohn) Schroet. to study the influence of the scion cultivar on rootstock susceptibility. The rootstock MM.111 was less susceptible to P. cactorum than M.7 when `Golden Delicious' was the scion, but there were no differences when `Delicious', `Haroldred Delicious', or `McIntosh' were the scions. Similarly, the rootstock M.26 was less susceptible than M.7 when `McIntosh' was the scion, but there were no differences when `Delicious', `Haroldred Delicious', or `Golden Delicious' were the scions. These results suggest that the influence of scions on rootstock susceptibility to P. cactorum crown rot is variable.

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S.M. Eichorst, R.B. Rogers and M.A.L. Smith

Use of a liquid media during micropropagation has promoted improved proliferation and rooting response in several species. In this experiment, a double phase system (a combination of liquid and agar solidified medium) was applied to three cultivars of miniature roses (Rosa chinensis var. minima) to determine the effects on shoot quality and subsequent ex-vitro rooting. Applications of liquid media to the surface of agar solidified media were made at 0, 2, and 4 weeks. Evaluation via computerized image analysis after eight weeks of proliferation revealed equal or greater values for shoot length, area and weighted density (equivalent to fresh weight) for cultures receiving overlay, regardless of timing, compared to the solid media control. Additionally, application of a liquid overlay improved rooting response by up to 20% over the control and resulted in a tendency for a greater number of roots of greater length and area than the treatment without liquid media overlay.

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M. A. L. Smith, S. L. Knight and M. J. Bass

A whole plant microculture (WPMC) screening system facilitated rapid, quantitative appraisal of salt stress effects on `Micro-Tom' miniature dwarf tomato. Axillary bud explants were micropropagated on a hormone-free control medium (conductivity = 3.3 dS m-1), gradually introduced to treatments with increasing NaCl or Na2SO4 concentrations via biweekly subculture to fresh media (7,6, 12.8, or 18 dS m-1), and monitored over a subsequent 5 week culture period. Non-intrusive video image analysis techniques were adapted to quantify morphometric (shoot growth rate, area, and length; root length and area) and photometric (ruler and tissue quality) plant responses. Shoot growth was only slightly inhibited at 7.6 and 12.8 dS m-1, but was severely stunted and distorted on high salt (18 dS m-1) media. Root growth inhibition (significantly shorter and thinner primary rants) was first evident at 12.8 dS m-1 after 3 weeks of treatment. At 18 dS m-1, conspicuous retardation of root growth relative to controls could be gauged after only one week. Shoot tip chlorosis was observed in the lowest salt-supplemented treatment after three to four weeks of culture, but overall shoot yellowing at the two highest conductivities was marked after only a few days. Chlorosis symptoms were not uniform within treatments. Cell osmotic concentration showed a linear increase with increasing medium salinity. The WPMC system expedited time course observations of stress symptom development, paralleled stress response trends observed in solution culture tests, and provided an excellent vehicle to investigate plant adaptation to saline conditions.

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D.A. Smith, M.L. Metz and S.L. Cuppett

Dry edible beans (Phaseolis vulgaris) represent an inexpensive way to incorporate protein into the diet as a food ingredient, but beans contain unpleasant flavors and several anti-nutritional factors that limit their use without first processing with long heat treatments. `Great Northern' bean flour was processed using either static or specially designed dynamic (continuous) processing methods. The dynamic process treated flour slurries at temperatures up to 124°for 20 sec. The slurries were quick-frozen and freeze-dried after frozen storage periods of 0, 8, 24, 120, or 504 hr. The flours were analyzed for sensory properties, emulsifying activity, foaming properties, and trypsin inhibition. The heat treatments improved sensory attributes of the flour. The foam capacity and foam stability decreased in heat-treated flours. Trypsin inhibitor activity was at a minimum level immediately following thermal processing, but increased with time in frozen storage prior to drying. Minimal thermal processes cannot be relied upon to inactivate trypsin inhibitors.

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C.F. Lunde, M.S. Mehlenbacher and D.C. Smith

A survey of hazelnut (Corylus avellana L.) genotypes for response to the eastern filbert blight pathogen [Anisogramma anomala (Peck) E. Müller] was performed. Seven varieties were discovered that did not display disease signs or symptoms when subjected to severe inoculation with A. anomala in the greenhouse and assayed for infection. These cultivars are `Closca Molla', `Ratoli', `Yoder #5', `Potomac', `Medium Long', `Grand Traverse' and `Zimmerman'. `Ratoli' and `Closca Molla', both minor varieties from Spain, are superior agronomic types to the resistant cultivar Gasaway, which has been the main resistance source used in the breeding program. Only `Zimmerman' carries the RAPD marker linked to resistance in populations segregating for the `Gasaway' gene. Three populations were created using, `Zimmerman', as the pollen parent in controlled crosses. These populations were inoculated with spores of the pathogen and assayed by indirect ELISA and by observation of canker incidence. Resistant phenotypes make up 84% of the populations, indicating that `Zimmerman' possesses resistance either distinct from or additional to that found in, `Gasaway'. A RAPD marker linked to the resistance gene in crosses with `Gasaway' cosegregates with the resistant phenotype in all three populations (0 cM, 3 cM, 4 cM). Mechanisms to explain the distortion in these populations are discussed. Further studies are required to characterize the mechanism and inheritance resistance in these other clones.

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S.M. Smith, J.W. Scott, J.A. Bartz and S.A. Sargent

Harvested tomato (Solanum lycopersicum L.) fruit can absorb water via stem scar tissues. Decay incidence {bacterial soft rot (Erwinia carotovora Jones), sour rot (Geotrichum candidum Link), bacterial sour rot [Leuconostoc mesenteroides (Tsenkovskii) van Tieghem ssp. mesenteroides], and certain species of Lactobacillus Beijerinck} has been positively linked with the degree of water absorption. Previous studies have shown that cultivars differ in their tendencies to take up water during a simulation of packinghouse handling procedures. The inheritance of water absorption tendency was examined in two seasons of tests where six inbred tomato lines were intercrossed to develop a complete diallel. Following harvest at the mature-green stage, fruit were weighed, submerged in water for 2 min, and then reweighed to determine water absorption. Parental lines were tested in three seasons. Two parental lines, Fla. 7776 and Fla. 7946, were always in the low-absorption grouping, and NC84173 also had relatively low absorption. Fla. 8059 and Fla. 7777 were always in the high-absorption group, and Fla. 8000 tended to have high absorption. General combining ability for the low water absorption fruit characteristic was significant for both seasons with a higher level of significance in the spring over the fall season (P ≤ 0.001 and P ≤ 0.05, respectively), while specific combining ability was not significant for either season. Thus, the low water absorption fruit characteristic appears to be additively inherited. Accurate knowledge of parental absorption should allow prediction of hybrid performance. None of the hybrids absorbed unexpected amounts of water over both seasons. Reciprocal effects were significant (P ≤ 0.05) for fall, and maternal effects were significant (P ≤ 0.05) in spring. However, there was no general trend in water absorption due to the direction of the cross and thus no clear evidence for cytoplasmic inheritance. Water absorption was much greater in spring than in fall. Based on previous observations, the greater absorption in spring was due to higher field temperatures. Because of such environmental effects, parent lines should be replicated and tested over several seasons to accurately assess their relative water absorption. Crosses between consistently low water absorption parents should provide low-absorption hybrids, but testing of hybrids before release is suggested to verify this.

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J.S. Seron, R.J. Ferree, S.L. Knight, M.A.L. Smith and L.A. Spomer

Tolerance of increased salinity by tomato is of great importance to the tomato processing industry, where increased conductivity of up to 6 dS m-1 is used to increase specific yield components. A new line of miniature dwarf tomato, Lycopersicon esculentum Mill. cv. Micro Tom, was evaluated for photosynthetic response to elevated salinity. Tomatoes were grown in solution batch culture and subjected to constant salt treatments of 2.4 (control), 7.6, 12.8, or 18 dS m-1. Weekly photosynthetic measurements were made beginning week 4 on the most recent fully open leaf or leaf opposite a fruit. Net photosynthesis decreased across all salt treatments over the last six weeks of sampling. As salinity level increased, net photosynthesis decreased compared to the control. The 18 dS m-1 treatment reduced net photosynthesis relative to 12.8 and 7.6 dS m-1. Although salinity increased succulence, limitations to net photosynthesis were due to diminished utilization of intercellular CO2, rather than reduced internal CO2 concentration or stomatal conductance.

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S.M. Smith, J.W. Scott, J.A. Bartz and S.A. Sargent

Fresh market tomatoes (Solanum lycopersicum L.) handled through dump tanks and flumes at packinghouses can absorb water via stem scar tissues. This water uptake can lead to internalization of various hazardous bacteria, including Erwinia carotovora (Jones), the causal agent of bacterial soft rot. Studies were conducted to determine if the interval between harvest and water immersion affected water uptake for ‘Florida 47’ and ‘Sebring’, cultivars with high and low water uptake, respectively. Fruit were held for 2, 8, 14, and 26 hours after harvest for the fall season and 2, 4, 6, 8, and 14 hours for the following spring season before water immersion. Mature green fruit were weighed, submerged in water for 2 min and then reweighed to determine water uptake. During the submergence, air pressure was applied such that the fruit were exposed to a static water-head equivalent to 1.3 m. In the fall season ‘Sebring’ fruit absorbed significantly less water than ‘Florida 47’ fruit at 8 and 26 hours after harvest. In the spring season fruit of ‘Sebring’ absorbed significantly less water than ‘Florida 47’ at all times after harvest, confirming results of previous studies. In the fall season, the time interval between harvest and treatment did not affect water uptake for either cultivar. By contrast, in the spring season fruit absorbed significantly greater amounts of water at 2 hours as compared with 4, 6, 8, and 14 hours after harvest, whereas similar amounts of water were absorbed at 4–14 hours after harvest. Therefore, to minimize the tendency of fruit to absorb water, packinghouse managers should hold freshly harvested fruit for at least 4 hours before immersing them in the dump tank.

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T.E. Thompson, L.J. Grauke, William Reid, M.W. Smith and S.R. Winter

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S. Garcés, M. Koch-Dean, J. Maas, B. Smith and F. Hammerschlag

As part of a program to generate anthracnose (Colletotrichum acutatum) resistance in strawberry (Fragaria × ananassa Duch.) via either tissue culture or gene transfer techniques, studies were conducted to determine whether in vitro screening for resistance to C. acutatum was feasible. Six commercial cultivars (Latestar, Delmarvel, Pelican, Sweet Charlie, Chandler, and Honeoye) that differed in their response to the pathogen under field conditions were tested to see whether this response was reflected in vitro. Leaves from 4-week-old shoot cultures were soaked in a spore suspension of C. acutatum isolate Goff, transferred to 0.5% water agar, and the presence or absence of disease symptoms was evaluated on a 0-4 rating scale after 7 days. Five of the six cultivars exhibited a disease rating similar to field results. This study suggests that there is potential to use this procedure as a screening technique, and studies are in progress to screen strawberry regenerants for resistance.