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- Author or Editor: Jung-Myung Lee x
Similar to many Asian countries, the production and utilization of vegetables in Korea are quite different as compared to western countries. Koreans were used to favor easy-to-grow leafy and root vegetables, but this preference is gradually shifting to other vegetables, due partially to the recent surge in per capita income and westernization of cultures. In Korea, most vegetables are being utilized in fresh state with only a few exceptions, such as Kimchi, spicy vegetables, etc. Growing technics as well as the specialized production systems of several selected vegetable crops will be introduced. These include commercial production of vegetable seed and seedlings of special kinds (grafted or plug-grown), use of virus-free garlic cloves and potato mini-tubers, hydroponic culture of lettuce and other vegetables, automation of greenhouse crop production, off-season growing, and specific growing systems for minor vegetables.
Fruits of `Tsugaru' (an early maturing cultivar), `Hongro' (mid-season cultivar), and `Fuji' (late cultivar), were harvested at different times of the year, depending upon their maturity, and treated with 1-MCP at 0.0, 0.5, 1.0, and 2.0 ppm for 8-24 hours. Fruits were also treated with 1-MCP at different times after harvest. Portions of 1-MCP-treated apples were also treated with ethylene in order to study the interaction between 1-MCP and ethylene. In other experiments, fruits were treated with ethylene first and then treated again with 1-MCP. Major results are as follows. Treatment of 1-MCP greatly retarded the senescence of `Tsugaru' apple stored at room temperatures as compared with the control. The sooner the time of 1-MCP treatment after harvest of fruit, the greater was the 1-MCP effect. In contrast to the time of 1-MCP treatment, the concentration of 1-MCP and duration of 1-MCP infiltration in a closed chamber exhibited only a minor effect. Ethylene treatment immediately before and/or after the 1-MCP treatment showed only the 1-MCP effect, thus clearly showing that 1-MCP treatment could completely reverse or counter the ethylene effect in `Fuji' apples. Repeated treatments of 1-MCP after a certain period of low temperature storage of `Fuji' apples were more effective than a single treatment. Parameters related with fruit quality will be discussed in detail.
Even though dry-heat (DH) treatment has been widely used for inactivation of seed-borne virus in vegetable seeds, it is known that the seeds should be used within a year after the DH treatment because of the significant reduction of storage capability in DH-treated seeds. DH-treated seeds exhibited poor early germination and significantly higher percentages of abnormal seedlings produced. The final germination rate was, however, not usually influenced by DH treatment. DH-treated seeds had been stored at 20 °C up to 5 years in sealed containers with silica gel in some cultivars. Both the intact and DH-treated seed exhibited excellent germination even after 4 years of storage at room temperature. Even though the hypocotyl length was shortened in DH treated seeds of most cultivars tested, other characteristics of seedlings produced from intact and or DH-treated seeds were similar. Cultivars showed marked differences in seedling characteristics, especially in length of hypocotyles.
Dry-heat (DH) treatment has been extensively used for inactivation of some seed-borne virus and Fusarium disease in many vegetable crops, especially in cucurbitaceous vegetables. Strains of tobamovirus (cucumber green mottle mosaic virus; CGMMV) could be successfully inactivated by treating the infected seeds at 75 °C for 72 h. However, DH-treated seeds frequently exhibit slow and poor germination and abnormal seedling characteristics, such as distorted, white streaked, and punctured cotyledons in the seedlings. The moisture content in seed coat and inner cotyledons fell down to below 1% in DH-treated seeds when treated at 75 °C or higher. However, when the seeds were treated at 65 °C, final moisture content in the DH-treated seeds were maintained at about 2.5% to 3.5%. Seeds absorbed moisture above 20% at 100% RH, 9% to 10% at 73% RH, and 4% to 5% at 28% RH, respectively. When the intact and DH-treated seeds were exposed to conditions of varying relative humidity, DH-treated seeds absorbed atmospheric moisture at a much slower rate than the intact seeds in all tested cultivars, and this is thought to be one of the major reasons for slower germination in DH-treated seeds. The inactivation of virus, comparison of respiration of seeds, and endogenous gibberellic acid contents will also be presented.
Increasing numbers of vegetables are being grafted in recent years and many different grafting methods, as well as grafting aids, have been developed and practiced among farmers as well as commercial plug seedling producers. For solanaceous crops, such as tomatoes, peppers, and eggplants, splice grafting at very young stages of development is recommended. Several types of grafting machines and/or robots are now available for commercial use. The presence of roots often slows down and reduces the efficiency of robot or machine grafting. Therefore, grafting with root-removed rootstocks is frequently used for grafting, mostly because of the grafting efficiency, especially in cucurbitaceous crops. The feasibility of producing grafted pepper plug seedlings using root-removed rootstock was investigated. After grafting, the seedlings were placed in pot soil in cell trays, usually 128-cell trays, and then placed in a conditioning room for subsequent rooting and graft union formation. Young pepper cuttings readily rooted in pot soils and the use of rooting substances greatly accelerated the speed of rooting. Even though rooting was delayed a few days in grafted seedlings, normal rooting took place in all graft combinations.
Cultivation of grafted tomatoes has been sharply increased in recent years. Millions of grafted seedlings were grown in California as well as other parts of the world, and the need for high quality grafted tomato seedlings is also rapidly growing. Since the price of grafted plug seedlings are 3–4 times higher than the nongrafted ones, production and commercial distribution of double-stemmed plugs, even though slightly more expensive than the single-stemmed plugs, will greatly cut down the expenses needed to purchase grafted seedlings. Several methods of producing double-stemmed grafted plug seedlings are presented and the advantages as well as the disadvantages of these methods will be fully discussed. Brushing or painting lanolin paste containing thidiazuron at 100–500 ppm to the lower node of the decapitated scion is effective in fast-growing cherry, whereas inducing double stems from the cotyledonary node of grafted scions appeared to be more practical for ordinary tomatoes for table use. Methods of grafting, especially in relation with machine grafting, will be discussed.
Dry heat treatment (DHT), a powerful and agrochemical-free means of inactivating seed-borne virus and other pathogens, has been extensively used for value-added vegetable seeds in Korea, Japan, and some other countries. Since seeds are treated with extremely high heat (75 °C or higher) for a long time (72 h or longer), heat-induced phytotoxicity symptoms are frequently observed. Even though various internal and external factors, such as seed maturity and vigor, maximum temperature and duration of DHT, are known to influence the severity of phytotoxicity, precise control of seed moisture contents during DHT is regarded as one of the most important factors for successful DHT. In an ideal condition using a specifically designed DTH machine, seed moisture content of bottle gourd, initially around 6.20% to 0.64% when stored in a storage room with 50% RH, decreased by 1% after 24 h at 35 °C (5.20% to 0.23%), and further decreased below 4% after 24 h pretreatment at 50 °C (3.64% to 0.37%). The seed moisture content was further reduced down to about 2% after 72 h DHT at 75 °C (2.16% to 0.28%). During the post-treatment conditioning at 50 °C and 70% RH for 24 h, the moisture contents were raised to about 6%(5.94% to 0.45%), thus approaching the initial moisture content of 6% to 7%. During the germination period, treated seeds showed slower absorption of water as compared to the intact seeds, thus suggesting that this slow absorption of initial moisture absorption may be responsible for the slow initial germination frequently observed in treated seeds. Final germination and seedling vigor were not affected by DHT.
Common watermelons have an indeterminate growth habit with normal internode length, thus allowing the vine to grow indefinitely under the normal conditions. Watermelon breeders have identified four dwarf genes (dw-1, dw-1 s , dw-2, dw-3) and used these for developing dwarf watermelon cultivars. We discovered a naturally occurring new dwarf and seedless mutant (NDSM) from a landrace cv. Mudungsan that had been cultivated in the Mountain Mudung area nearby Gwangju City in Korea. The progenies of this mutant segregated in a ratio of 3 vine to 1 dwarf indicating a single recessive gene nature. Morphological characteristics of the NDSM were markedly different from those of the four known dwarf genotypes. NDSM plants grow shorter than 1 m in length with fan-shaped leaves and have fewer leaf lobes than normal plants, which could be clearly distinguished at 2 or 3 true leaf stage. Male and female flowers have just one petal and failed to open completely even at the anthesis. Even though there were some fertile pollen grains, the fruits of NDSM had no seed after fertilization. The F2 progenies, obtained from crossing `920533' (normal vine type) and NDSM, segregated in a ratio of 3 vine to 1 dwarf. All F1 plants from crosses between 2 dwarf types, `Sugar Bush' (dw-1dw-1) and `NH 9' (dw-2dw-2), and NDSM were normal, while F2 showed 9 vines, 3 dw-1 or dw-2 types, 3 NDSM types, and 1 double dwarf. The backcross generation segregated in a ratio of 1 vine to 1 dwarf. These results indicate that the genes for the NDSM and 2 dwarf types are non-allelic. We named this new dwarf genotype (NDSM) as dw-4 in addition to four dwarf genes previously identified.
Cucumber green mottle mosaic virus (CGMMV) is a noxious disease in cucurbits, especially in Asia where grafting is commonly practiced. CGMMV can be easily transmitted by seed, hands, soil, or grafting. Seed companies are rigorously looking for effective and efficient means of CGMMV inactivation in infected seeds. Among the various treatments applied to the seeds, dry heat treatment (35° C 1 day + 50 °C 1 day + 75 °C 3 days) was found to be most suitable for complete inactivation. Various identification methods including high-density latex agglutination test (HDLPAT), ELISA, RT-PCR, and bioassay (Chenopodium amaranticolor) were compared for accurate diagnosis of the presence of virus in seeds. The results from HDLPAT showed the highest correlation with the bioassay results, suggesting that HDLPAT can be safely used for accurate means of virus detection. Details of dry heat treatment, various seed treatment, and other detection methods will be presented.