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J. Cohen, Noga Sikron, S. Shuval, and A. Gera

In this study, 18 Petunia ×hybrida Hort. Volm.-Andr. cultivars were mechanically inoculated with the tobamoviruses tobacco mosaic (TMV) or tomato mosaic virus (ToMV) (20 μg·L-1 in 0.05 m sodium phosphate buffer). One and 2 weeks post-inoculation (PI), inoculated and noninoculated upper leaves were harvested and assayed for TMV infection using enzyme-linked immunosorbent assay (ELISA). Local lesions developed on inoculated leaves of 16 cultivars 3-5 days PI. A total of 11 and 16 of the cultivars developed systemic symptoms characteristic of tobamovirus infection 2 weeks after inoculation with TMV and ToMV, respectively. All cultivars were positive in ELISA tests. Large amounts of virus were recovered from the upper, noninoculated leaves of all cultivars, including symptomless plants. Up to 95% infection by TMV occurred when a sterilized knife was passed through an infected shoot of petunia prior to its being used to remove cuttings from healthy petunia plants. Heat sterilization of knives and/or treatment with 2.8 g·L-1 sodium troclosene was very effective in controlling TMV transmission.

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Sara Spiegel, Dan Thompson, Aniko Varga, and Delano James

An apple chlorotic leaf spot virus (ACLSV) isolate was detected by TAS-ELISA and RT-PCR in an ornamental dwarf flowering almond (Prunus glandulosa Thunb.). This plant, maintained at the Centre for Plant Health, Sidney, B.C., Canada, has been showing transient leaf symptoms during the spring seasons. A 390-bp fragment and a 1,350-bp product, in the RNA polymerase and the coat protein viral coding regions, respectively, were amplified by RT-PCR from the infected plant. A sequence comparison of the 390-bp fragment of this ACLSV isolate (designated as AL1292) with other published isolates, revealed a similarity of 81% to 84% at the nucleotide level and 88% to 100% at the amino acid level. In contrast to other ACLSV isolates, AL1292 has an exceptionally narrow range of experimental herbaceous and woody hosts, as determined by mechanical and graft inoculation assays. These standard bioassays may not be effective for the detection of the AL1292 isolate because of its limited host range. The results we report in this paper confirm P. glandulosa as a natural host of this virus. Currently it is not known how ACLSV is spread, other than by bud-grafting and possibly by root grafts. The use of virus-tested source plants for the preparation of planting material will minimize its spread.

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China F. Lunde, Shawn A. Mehlenbacher, and David C. Smith

Ninety hazelnut (Corylus sp.) genotypes were surveyed for response to the eastern filbert blight pathogen [Anisogramma anomala (Peck) E. Müller] following greenhouse inoculation using a combination of enzyme-linked immunosorbent assay (ELISA) and visual inspection for cankers. Most were cultivars of the European hazelnut (Corylus avellana L.) and a few were interspecific hybrids. Six genotypes did not display signs of the pathogen or symptoms of disease: `Closca Molla', `Ratoli', `Yoder #5', `Potomac', `Medium Long', and `Grand Traverse'. `Closca Molla' and `Ratoli', both minor Spanish cultivars, are superior in many respects to `Gasaway', which has been extensively used as a completely resistant parent in breeding. `Potomac' and `Yoder #5' have C. americana Marsh. in their pedigrees, `Grand Traverse' is one-quarter C. colurna, and the origin of `Medium Long' is uncertain. The random amplified polymorphic DNA (RAPD) marker generated by primer UBC 152, which is linked to the single dominant resistance gene of `Gasaway', is absent in these six genotypes, and thus they appear to be novel sources of genetic resistance to this devastating disease.

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Youjian Lin and Charles A. Powell

The distribution pattern of citrus tristeza virus (CTV) T-36 isolate in leaves of infected mexican lime [Citrus aurantifolia (Christm.) Swingle] plants was visualized using a whole-leaf-blot immunoassay (WLBIA) procedure in combination with a computer scanning imaging technique and CTV-specific monoclonal antibody 17G11 (CTV MAb 17G11). The distribution pattern of CTV T-36 in leaves varied with the age of the leaves and shoots of infected plants. In the young leaves, especially the about 5-day-old leaves and the completed expanded leaves, CTV T-36 was easily detected in most of the leaf veins, the main veins and the large and small primary veins. In the old leaves, CTV T-36 only was detected in the main veins, sometimes in a few of the large primary veins with weak signals, and seldom in the small primary veins. The distribution density and immunoassay reaction signals of CTV T-36 reacted to CTV MAb 17G11 in leaves from new shoots were much higher than that in leaves from old shoots. ELISA test results using leaves with different ages from different shoots of the same mexican lime plants infected with CTV T-36 supported the visualized-test results obtained by the WLBIA in combination with computer scanning imaging technique. This is the first reported visual analysis of the distribution pattern of CTV in leaves of infected citrus plants. The results indicate that the WLBIA in combination with computer scanning imaging technique is a useful tool for studying the distribution of plant viruses in leaves of virus-infected plants.

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Angeline M. Peters and Aart van Amerongen

In this pilot study, we investigated the relationship between levels of bitter sesquiterpene lactones and sensory evaluation of chicory (Cichorium intybus L.). The levels of two bitter sesquiterpene lactones—lactucopicrin and lactucin-like sesquiterpene lactones—were measured by ELISA in raw and cooked chicory samples from several cultivars. Data were compared with the results of a sensory evaluation on the flavor attributes bitterness, typical chicory flavor, and total flavor intensity of identical chicory samples. Linear regression analysis demonstrated that the levels of lactucin-like sesquiterpene lactones were significantly related to bitterness (P = 0.006) and total flavor intensity (P = 0.03) attributes in raw chicory samples. When cooked chicory samples were evaluated, the levels of lactucin-like sesquiterpene lactones were significantly related to bitterness (P = 0.002), typical chicory flavor (P < 0.001), and total flavor intensity (P = 0.009) attributes, while lactucopicrin levels were related to bitterness (P = 0.002) only. These results show that the ELISA can be useful to predict flavor attributes in chicory.

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Amnon Levi and Kai-shu Ling

of disease symptoms for plants inoculated with ZYMV-FL in the greenhouse, an enzyme-linked immuno-sorbent assay (ELISA), and marker-assisted selection using two cleaved amplified polymorphic sequence (CAPS) markers of the eIF4E gene locus (CAPS1, CAPS

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Amnon Levi, John Coffey, Laura Massey, Nihat Guner, Elad Oren, Yaakov Tadmor, and Kai-shu Ling

(based on total number of plants from both tests), and average enzyme-linked immunosorbent assay (ELISA) values (based on two to four replications) in response to inoculation with Papaya ringspot virus (PRSV) in a greenhouse tests at the U.S. Vegetable

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Amnon Levi, Karen R. Harris-Shultz, and Kai-shu Ling

susceptible heirloom watermelon cultivar New Hampshire Midget ( Fig. 1 ). The breeding process employed stringent phenotypic ratings of plants inoculated with ZYMV-FL in the greenhouse, an enzyme-linked immunosorbent assay (ELISA) test, and marker

Open access

Elisa Solis-Toapanta, Paul Fisher, and Celina Gómez

To identify practices that may simplify the use of small-scale hydroponic systems for indoor gardening, we compared two nutrient solution management treatments for basil (Ocimum basilicum) production. Experiments were conducted for 8 weeks to evaluate the effect of biweekly replacement of the nutrient solution (W) vs. biweekly fertilizer addition without nutrient solution replacement (W/O) on growth and nutrient uptake of basil ‘Genovese Compact’ grown in either a greenhouse or an indoor environment. Greenhouse day/night temperature was 29/24 ± 4 °C, relative humidity (RH) was 65 ± 4%, and daily light integral (DLI) was 26.1 mol·m‒2·d‒1. The indoor environment had a constant ambient temperature of 21 °C, RH of 65%, and DLI of 9 mol·m‒2·d‒1 provided by broadband white lamps. Four plants were grown in 7.6-L replicate hydroponic systems, with 178 mg·L‒1 N from a complete nutrient solution in two experimental runs. Shoot fresh and dry mass, leaf number, and leaf area showed an increasing quadratic trend over time when plants were grown in the greenhouse. In contrast, growth over time was linear for plants grown indoors. Within each environment, solution management treatment did not affect growth, indicating that the simpler W/O strategy was adequate under these conditions. Plants grown in the greenhouse required more frequent refill water applications compared with indoors, which resulted in three to four times more refill water applied. Because indoor-grown plants had a decreased growth rate, nutrient uptake rate, and volume of water applied compared with plants grown in the greenhouse, electrical conductivity (EC) for the W/O treatment increased over time. Final nutrient solution concentration was highest for indoor-grown plants under the W/O treatment, and final tissue nutrient concentration was higher for plants grown indoors compared with the greenhouse. Final nutrient uptake (dry mass × nutrient concentration) was higher for plants grown in the greenhouse rather than indoors. Considering that EC increased in the solution of indoor-grown plants under W/O, an appropriate strategy using this treatment would require reducing fertilizer input indoors. To refine simple and robust fertilizer management strategies for indoor gardeners, further research is needed to test variables such as different plant species, cultivars, and water qualities.

Open access

Elisa Solis-Toapanta and Celina Gómez

In the quest to identify minimum daily light integrals (DLIs) that can sustain indoor gardening, we evaluated DLIs less than the recommended ranges for commercial production of basil (Ocimum basilicum). Experiments were conducted for 8 weeks to evaluate the effect of providing a constant vs. an increasing DLI over time (DLIInc) on growth and photosynthetic capacity of green (‘Genovese Compact’) and purple (‘Red Rubin’) basil grown hydroponically under a constant ambient temperature of 21 °C. Plants were grown under a 14 h·d–1 photoperiod and were subjected to the following DLI treatments: 4 (DLI4), 6 (DLI6), 8 (DLI8), or 10 (DLI10) mol·m–2·d‒1 (80, 119, 159, and 197 µmol·m‒2·s‒1, respectively); DLIInc was used as a fifth treatment and was achieved by transitioning hydroponic systems systematically to treatments with greater DLIs every 2 weeks. In general, regardless of cultivar, leaf area, leaf number, and overall growth [shoot fresh weight (SFW) and shoot dry weight (SDW)] were similar for plants grown under DLIInc to DLI4 and DLI6 during weeks 2, 4, and 6. However, plants grown under DLIInc produced the same leaf area as those grown under DLI10 at week 8. Nonetheless, across weeks, growth was significantly less under DLIInc compared with DLI10, but similar to that produced by DLI8 at week 8. Photosynthetic responses were significant only at week 8, for which leaves of plants grown under DLI8, DLI10, and DLIInc had 15% to 25% greater maximum gross carbon dioxide (CO2) assimilation (A max) than plants grown under DLI4. The light saturation point of photosynthesis was unaffected by DLI, but showed a general increasing trend with greater DLIs. Overall, our results suggest that providing a constantly high DLI results in greater growth and yield than increasing the DLI over time. In addition, we found that changes in A max and the light saturation point are not good indicators of the capacity of whole plants to make use of the available light for photosynthesis and growth. Instead, morphological and developmental traits regulated by DLI during the initial stages of production are most likely responsible for the growth responses measured in our study.