Molecular mapping of plant genomes has progressed rapidly since Bostein et al.(1980) introduced the idea of constructing linkage maps of human genome based on restriction fragment length polymorphism (RFLP) markers. In recent years, the development of protein and DNA markers has stimulated interest for the new approaches to plant improvement. While classical maps based on morphological mutant markers have provided important insights into the plant genetics and cytology, the molecular maps based on molecular markers have a number of inherent advatages over classical genetic maps for the applications in genetic studies and/or breeding schemes. Isozymes and DNA markers are numerous, discrete, non-deleterious, codominant, and almost entirely free of environmental and epistatic interactions. For these reasons, they are widely used in constructing detailed linkage maps in a number of plant species. Plant breeders improve crops by selecting plants with desirable phenotypes. However a plant's phenotyes is often under genetic control, positioning at different "quantitative trait loci" (QTLs) together with environmental effects. Molecular maps provide a possible way to determine the effect of the individual gene that combines to produce a quantitative trait because the segregation of a large number of markers can be followed in a single genetic cross. Using market-assisted selection, plants that contain several favorable genes for the trait and do not contain unfavourable segments can be obtained during early breeding processes. Providing molecular maps are available, valuable data relevant to the taxonomic relationships and chromosome evolution can be accumulated by comparative mapping and also the structural relationships between linkage map and physical map can be identified by cDNA sequencing. After constructing high density maps, it will be possible to clone genes, whose products are unknown, such as semidwarf and disease resistance genes. However, much attention has to be paid to level-up the basic knowledge of genetics, physiology, biochemistry, plant pathology, entomology, microbiology, and so on. It must also be kept in mind that scientists in various fields will have to make another take off by intensive cooperation together for early integration and utilization of these newly emerging high-techs in practical breeding. breeding.

지난 반세기간에 우리나라에 채소 육종은 주요 채소의 주년공급을 가능하게 하였으며, 토지 생산성의 향상, 상품화율의 증대, 품질의 향상 등의 면에서도 괄목할 만한 성과를 거두었고 인공교잡은 물론이고 웅성불임성과 자가불화합성의 활용에 의한 1대잡종 품종의 일반화로 채소 산업의 발전에 크게 기여하였다. 앞으로는 기왕의 업적을 심화시키는 한편, 생산비를 절감하기 위한 생력화, 기계화 재배용 품종 및 내제초제성 품종의 개발 환경보호 및 식품안정성의 확보를 위한 내병층성 품종 개발, 수출시장과 다양화하는 국내의 시장기호에 대응하고 가공 식품의 표준화된 품질관리를 지원할 수 있도록 품질 면에서의 개량과 신작물 또는 신생태형 품종의 개발에도 더욱 노력이 필요하다. 이러한 육종목표를 달성하기 위한 유전자원의 확보는 더욱 어려워질 것이며 유전 양식이 복잡하고, 환경요인의 작용이 상대적으로 크기 때문에 전통적인 육종 방법만으로는 목표달성에 필요한 인적, 물적, 시간적 소요가 훨씬 증가될 전망이다. 유전변이의 창성 및 확대, 유용 대립인자의 도입, 동정 및 선발, 그리고 종자생산을 위한 자가 불화합성 및 웅성불임성과 개화·수정 관련 유전인자의 발현 조절에 분자유전학의 보완적 역할이 기대되며 이렇게 되면 전통육종과 분자유전학간의 잡종강세로 품종 개량의 효율은 크게 높아질 것이다.

The major objectives of fruit breeding lie in improvement of cultivar, easy to be cultivated and of high quality, in order to produce unexpensive, delicious fruit both for fresh fruit market and processing. Recently, fruit breeding in Korea has contributed to breeding of several superior cultivars in major fruit crops, resulting in appreciable improvement in qualities such as skin color, taste and fruit-bearing habit concerned with productivity. In spite of accomplishments mentioned above, the need for both highly disease-resistant cultivars and long-keeping, physiological disorder-resistant cultivars to meet long distance transsportation in the temperate fruit crops of apples, oriental pears, stone fruits such as peaches, and grapes grown in Korea is rapidly pressing more than ever, as cultivars of today susceptible to pests and diseases and vulnerable to physiological disorders are very expensive and time-consuming in post-harvest handling and management. Thus, imporvements made in the above problems through breeding level will lead to the really enhanced productivity in fruit industry. The major impediments of tree size, the long length of juvenile period and the highly heterogeneous genetic composition to the improvement of fruit crops are responsible for the lower amount and rate of improvements of fruit crops as compared to annuals. Considering the expected limitations of the above problems to be solved through conventional breeding methods and strategy, a turning point of breeding a near perfect cultivar would be laid down if innovative breakthroughs in biological technology will be realized in applying some of the techniques of genetic manipulation at the molecular level to the cultivar improvement of fruit crops, such as the selective insertion of DNA carrying genes that govern desirable characteristics. More than anything else, those traits such as fruiting habit deciding productivity, elements of fruit qualities conditioned by monogene, and disease-and pest-resistance of vital importance for successful fruit growing are urgently desired to be improved by advancement of biotechnology for they are more than difficult and need long period to be attained through conventional breeding method.