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  • Author or Editor: W.A. Sargent x
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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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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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M.J. Bosela, J.P. Schnurr, Z.-M. Cheng and W.A. Sargent

Three elite hybrid aspen, Populus grandidentata × P. canescens, P. tremuloides × P. tremula, and P. tremuloides × P. davidiana, have been transformed with Agrobacterium tumefaciens strains LBA4404 and EHA105 carrying kanamycin resistance and GUS genes. The leaves of micropropagated shoots were co-cultivated with Agrobacterium for 65 to 72 hr and then transferred to callus-induction medium with 80–120 mg/L kanamycin in the dark. After 2 weeks, the leaves were transferred to shoot-induction medium under 18-hr photoperiod. Regenerated shoots were verified for transformation by histochemical staining and PCR. Transformed shoots rooted and were transplanted to soil. The three hybrid clones differed widely in their medium requirements for regeneration and in their competence for transformation. The leaves of P. grandidentata × P. canescens callused vigorously on a wide variety of media. In a typical transformation experiment, 30% to 60% of infected leaves produced putatively transformed calli (up to 10 calli per leaf). The origin of these calli and the frequency of shoot formation depended on the Agrobacterium strains. The calli from EHA105-infected leaves produced shoots within six weeks of co-cultivation and at high frequencies (70% to 90%). However, the calli from LBA4404-infected leaves produced shoots more slowly and at much lower frequencies (5% to 10%). Delaying selection for 2 weeks was found to lower the transformation frequency. Putatively transformed calli were obtained from P. tremuloides × P. tremula, and P. tremuloides × P. davidiana hybrids at frequencies of only 2% to 3%. The calli regenerated from P. tremuloides × P. davidiana leaves were very small, but they continued to grow upon being transferred to shoot-induction media and have started to produce shoots. The calli from leaves of P. tremuloides × P. tremula were much larger and they produced shoots more quickly. This transformation protocol is currently being used to introduce rooting genes into these hybrids to improve their rooting from hardwood cuttings.

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Steven A. Sargent, Adrian D. Berry, Jeffrey G. Williamson and James W. Olmstead

Three southern highbush blueberry cultivars (Vaccinium corymbosum hybrids) were mechanically harvested (MH) or hand-harvested (HH) and commercially packed before storage for 14 days at 1 °C in two successive years. MH fruit were softer, had lower ratings for overall appearance, and lost up to 20% more fresh weight than HH fruit after 14 days storage. MH ‘Meadowlark’ had fewer soft fruit (<35%) during storage than either ‘Sweetcrisp’ or ‘Farthing’; however, the latter two cultivars had lower incidences of shrivel and weight loss. Fruit in the 2010 season were more susceptible to bruising than those from the 2009 season; however, soluble solids content (SSC), total titratable acidity (TTA), and ascorbic acid concentration remained constant during storage and between seasons. ‘Meadowlark’ had the highest sugar to acid ratio (25.0). Successful implementation of MH of southern highbush blueberries for fresh market will only be commercially feasible if harvest impacts are further reduced.

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L.A. Risse, J.K. Brecht, S.A. Sargent, S.J. Locascio, J.M. Crall, G.W. Elmstrom and D.N. Maynard

Two newly released cultivars of small watermelons [Citrullus lunatus (Thumb.) Matsum and Naki], `Mickylee' and `Minilee', plus two other cultivars, Baby Fun and Sugar Baby, were stored at various temperatures from 1 to 21C for up to 4 weeks plus 1 week at 21C over two seasons. All cultivars were susceptible to chilling injury (CI) when stored below 7C; however, `Minilee' was less susceptible than the other cultivars tested. Chilling injury increased with storage length. Conditioning at 26C for 3 days before storage at 1C reduced CI and increased the percentage of marketable watermelons after storage. Decay percentage increased with storage time and was highest on fruit held at 1C where CI led to decay. The flesh of `Mickylee' and `Minilee' was firmer than that of the other cultivars tested and `Mickylee' and Minilee' retained their firmness better during storage. Total soluble solids concentration decreased with increased storage temperature. `Minilee' watermelons were superior to the other three cultivars in postharvest storage potential and exhibited the least CI and decay.

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D.D. Treadwell, G.J. Hochmuth, R.C. Hochmuth, E.H. Simonne, S.A. Sargent, L.L. Davis, W.L. Laughlin and A. Berry

Greenhouse experiments were conducted in 2005 and 2006 near Live Oak, FL, to develop fertilization programs for fresh-cut ‘Nufar’ basil (Ocimum basilicum) and spearmint (Mentha spicata) in troughs with soilless media using inputs compliant with the U.S. Department of Agriculture's National Organic Program (NOP). Four NOP-compliant fertilizer treatments were evaluated in comparison with a conventional control. Treatments and their analyses in nitrogen (N), phosphorus (P), and potassium (K) contents are as follows: conventional hydroponic nutrient solution [HNS (150 ppm N, 50 ppm P, and 200 ppm K)], granular poultry (GP) litter (4N–0.9P–2.5K), granular composite [GC (4N–0.9P–3.3K)], granular meal [GM (8N–2.2P–4.1K)], and GM plus a sidedress application of 5N–0.9P–1.7K fish emulsion (GM + FE). Electrical conductivity (EC) of the media, fresh petiole sap nitrate (NO3-N) and K concentrations, dried whole leaf NO3-N, P, and K concentrations, and yield and postharvest quality of harvested herbs were evaluated in response to the treatments. Basil yield was similar with HNS (340 g/plant) and GP (325 g/plant) in 2005 and greatest with HNS (417 g/plant) in 2006. Spearmint yield was similar with all treatments in 2005. In 2006, spearmint yields were similar with the HNS and GP yields (172 and 189 g/plant, respectively) and greater than the yields with the remaining treatments. In both years and crops, media EC values were generally greater with the GC than with the GP, GM, and GM + FE treatments but not in all cases and ranged from 1.77 to 0.55 dS·m−1 during the experiments. Furthermore, HNS media EC values were consistently equal to or lower than the GP media EC values except with EC measurements on 106 days after transplanting in both crops in 2005. Petiole NO3-N and K results were variable among crops and years, but provided valuable insight into the EC and yield data. We expected EC, petiole NO3-N, and petiole K to be consistently higher with HNS than with organic treatments, but they were not, indicating a reasonable synchrony of nutrient availability and crop demand among the organic treatments. The postharvest quality of both basil and spearmint was excellent with all treatments with few exceptions.