Oriental pear, `Niitaka', often suffers from skin and/or core browning when storage duration is extended. Skin browning occurred in aged fruit differs from browning disorder occurred at the early stage of low temperature storage (within 1 month), which is dark in color. This disorder can be inhibited by temperature conditioning through stacking fruit under shade for 7 days. Unlike dark browning disorder, fruit affected by light browning disorder often develops core browning. Also, when the duration of temperature conditioning is extended, light browning disorder occurred more rapidly even at 0 °C. In this experiment, the effect of external application of ethylene and ethylene scrubbing in storage environment was examined. Light browning disorder increased when fruit were wrapped with polyethylene film (30 μm) and the application of ethylene scrubber effectively decreased this disorder. Skin peeling was also observed in disordered fruit. The application of ethylene resulted in the increase of light browning on skin and core browning. Thus, both disorders seemed to be involved with senescence. The involvement of ethylene on both disorders will be further discussed.
Y.S. Hwang, J.C. Lee, and B.J. Lee
J.D. Chung, B.J. Lee, H.S. Lee, and C.K. Kim
Lettuce (Lactuca sativa L.) were transformed using microparticle bombardment with two different genes, alpha-glucuronidase (GUS) gene and Chinese cabbage Glutathione Reductase (GR) gene. The adventitious shoots of cotyledonary explant from 4-day-old seedlings were formed (46.7%) in MS basal media supplemented with 5.0 μm IAA and 1.0 μm 2ip. When 1100 psi helium pressure, 9 target distance, and coating with tungsten 10 microparticles were used and explants were treated with osmoticum-conditioning medium (0.6M sorbitol/mannitol), 4 h prior to and 16 h after bombardment, it was identified by GUS assay that these conditions were the most efficient for transformation of foreign genes into cotyledon tissue of lettuce with particle bombardment. PCR confirmed that the band observed in the transgenic plants were originated from T-DNA tranfer with strong hybridization. The genomic Southern analysis showed that the 1.5-kbp fragment was hybridized with radiolabeled 1.5-kbp GR probe. To know whether the expression of the GR gene can be stably maintained in the next generation, when T2 selfing seeds that were obtained from the transformed mother plants were sowed on MS medium supplemented with 200 μm kanamycin, 70% of seedlings were revealed resistance to kanamycin.
H.M. Wallace, B.J. King, and L.S. Lee
Pollen source is known to affect the fruit size and quality of 'Imperial' mandarin, but no study has determined the appropriate orchard design to maximize the beneficial effects of pollen source. We determined the parentage of seeds of 'Imperial' mandarin using the isozyme shikimate dehydrogenase to characterize pollen flow and the effect on fruit size in an orchard setting. Two blocks were examined: 1) a block near an 'Ellendale' pollinizer block; and 2) an isolated pure block planting. Fruit size and seed number were maximum at one and three rows from the pollinizer (P ≤ 0.05). Isozyme results were consistent with all seeds being the result of fertilization by the 'Ellendale' pollinizer. In the pure block planting, fruits in rows 5-11 inside the block were very small with no seeds. This indicates poor pollen flow resulting in a reduction in fruit quality for the pure block. These results emphasize the importance of pollinizers in orchard design, and bees in orchard management. They suggest that each row should be planted no more than three rows from the pollinizer to maximize the benefits of the pollen parent in self-incompatible cultivars such as 'Imperial'.
Kyung Ku Shim, Y.M. Ha, J.B. Lee, K.O. Byun, Y. Youn, E.R. Noh, and H.R. Park
New cultivars, `SKK 1' and `SKK 2', of Korean mountain ash (Sorbus alnifolia) that had superior morphological features as woody landscape plants were selected from 5000 seedlings of Sorbus alnifolia. Two clones with genetic variation were selected from 1983 to 1994 as landscape plants with large leaf and unique tree form: `SKK 1', which had large leaf and flower, and `SKK 2', with semi-weeping tree form. New selected cultivars of S. alnifolia were successfully grafted and inherited their mother characteristics. Sorbus alnifolia was difficult to propagate by cutting. Therefore, in vitro propagation methods might be used to propagate the superior cultivars. Shoots with apical and axillary buds were excised from 1-year-old seedlings. The explants were cultured on WPM supplemented with 0.5 mg/L BA. Shoots formed from initial cultures were subcultured at ≈4-week intervals onto the same media. To know the best hormone concentration in shoot multiplication, 0.1–3.0 mg/L of BA and 0.1–1.0 mg/L of zeatin were added to each WPM and MS media. The best shoot proliferation and elongation were obtained on MS medium with 1.0 mg/L BA from the whole shoot with the callus-like tissue, whereas the worst results were obtained from shoot tip. A 13-fold proliferation rate was achieved every 4 weeks.