Exserohilum turcicum is considered serious destructive disease of maize (Zea mays L.) in North Korea. This study aimed to understand genetic inheritance and combining ability of newly bred lines of maize tolerant to E. turcicum by diallel crosses. Three diallel sets for two different ecological regions and one agronomic trait; eastern (E), northern (N) and stay green (SG) involving 29 inbred lines were tested in eight locations of 2000 and 2001. E. turcicum infections were under natural conditions, respectively. Lines used were selected for high yield potential in test crosses with good agronomic traits and tolerance to biotic and abiotic stresses. Selection for race specific high resistance to biotic stresses was avoided to select quantitatively inherited genes. Host plant responses to E. turcicum were rated on a scale of 1 (highly tolerant) to 9 (highly susceptible). Highly significant variations were recorded in all trials. General combining ability (GCA) mean square was roughly twice that of specific combining ability (SCA). The genotype (G) by environment (E) interaction was highly significant. The overall results of genetic studies in three diallel sets show that genetic control for inbred tolerance to E. turcicum is polygenic and quantitatively inherited. New inbreds; E-3, N-1 and SG-4 confer better tolerance to E. turcicum than the widely used inbreds; Mo17, and B73. Proper use of genetic information from this study shall increase of corn production under high E. turcicum infection in the Far Eastern Regions of Korea and China.

Use of public tropical lines for U.S. commercial maize (Zea mays L.) breeding is either undocumented or non-existent. A possible exception is the old Cuban line A6, which was still being used in tropical hybrids over 40 years after its development. A major reason for the under-utilization of this valuable germplasm source is the sparse amount of yield-trial data available for most tropical lines. Effective evaluation of tropical, unadapted maize is costly and time-consuming in the U.S. corn-belt, where most temperate maize breeding is done. Thus, temperate maize breeding programs have shown minimal interest in such lines. The narrowness of the temperate maize (Zea mays L.) germplasm base has long been recognized, and there are many available, elite tropical lines that might be used to profitably broaden it. However, there are few comparative yield-trial data by which to choose which line(s) might be most useful. As the investment required for using a tropical line in a temperate breeding program is large, line-choice is critical. Tropical maize (Zea mays L.) represents a valuable genetic resource containing unique alleles not present in elite temperate maize. The strong delay in flowering in response to long daylength photoperiods exhibited by most tropical maize hinders its incorporation into temperate maize breeding programs. The objective of this study was to integrate candidate gene analyses with photoperiod QTL mapping across multiple maize populations. We tested the hypothesis that diverse tropical inbreds carry alleles with similar effects at four key photoperiod response quantitative trait loci (QTL) previously identified in maize. Four tropical maize inbreds were each crossed and backcrossed twice to the temperate recurrent parent B73 to establish four sets of introgression lines. Evaluation of these lines under long day lengths demonstrated that all four QTL have significant effects on flowering time or height in these lines, but the functional allelic effects varied substantially across the tropical donor lines. At the most important photoperiod response QTL on chromosome 10, one tropical line allele even promoted earlier flowering relative to the B73 allele. Significant allelic effect differences among tropical founders were also demonstrated directly in an F2 population derived from the cross of Ki14 and CML254. The chromosome 10 photoperiod response QTL position was validated in a set of heterogeneous inbred families evaluated in field tests and in controlled environments.

Mongolia is known as the livestock country for 800 years from the period of Chinggis Khaan Empire. The livestock has been raised without corn, a high quality feed. Hence, the meat of Mongolia has not been exported. In 2004, International Corn Foundation (ICF) and KNU in Korea initiated corn breeding program for Mongolia with Mongolian Academy of Science and Agricultural University of Mongolia. Since that time approximately 2000 genotypes were planted in Agricultural Research Station in Darkhan, Mongolia. Within 4years of research we have succeeded in forming Mongolian corn population (MCP), which can be used to breed locally adapted varieties in different zones. MCP characterizes early maturity, cold and drought tolerances. In 2008, 160 S1 were planted and 16 lines were selected. For further inbreeding and population improvement we planted all 16 lines in KNU vinyl house at Kunwi in late September. F1 crosses and advanced S3 lines will be tested in 2009 first time for hybrid development in Mongolia.

In order to determine the optimum harvest time for the seed production of inbreds and hybrids in silage corn, the ears of sib-pollinated 'KS5', 'KS7rhm', and 'Ga209' and cross-pollinated 'KS5' ~times 'KS6' (Suwon19), 'KS7 rhm' ~times 'KSl17' (Suwonok), and 'Ga209' ~times 'DB544'(Kwanganok) were harvested at the one-week intervals from 4 to 10 weeks after silking. The optimum harvest time for the seed production for 'KS5', 'KS5' ~times 'KS6', 'KS7 rhm', and 'KS7rhm' ~times 'KS117' was 7 weeks after silking considering both emergence rate and plumule growth in cold test. Although earlier harvested seeds showed similar germination rate as the seeds harvested at the optimum time at 25~circC , their emergence rate were lower in cold test. Seed weight and α -amylase activity of earlier harvested seeds were lower compared to those of seeds harvested at the optimum time, while leakage of total sugars and electrolytes were higher. However, the later harvested seeds showed lower germination rates at 25~circC and emergence rates in cold test probably due to the lower α -amylase activity although they showed increased seed weight and reduced leakage of total sugars and electrolytes. In contrast, the emergence rate of 'Ga209' and 'Ga209' ~times 'DB544' in cold test increased up to 10 weeks after silking probably due to the increased seed weight and α -amylase activity and reduced sugar and electrolyte leakages during the germination. The cross-pollinated F1 hybrid seeds showed higher germination and emergence rates at 25~circC and in cold test, and higher plumule growth and α -amylase activity compared to those of sib-pollinated inbreds.

옥수수의 육성과정이나 교잡종 생산시에 암술봉투를 씌우기 전에 상부이삭이 출사하는 경우에는 출사한 개체를 버리지 않고 출사한 이삭을 제거하면 하부이삭이 발육하므로 종자 생산을 기대 할 수 있다. 본 실험은 7개의 자식계통을 공시하여 출사된 상부이삭의 제거가 하부이삭의 개화와 종자생산에 대한 반응을 검토하고자 실시하였으며 그 결과를 요약하면 다음과 같다. 1. 상부이삭을 제거하였을 때 하부이삭의 출사기는 상부이삭보다 4일 정도 지연되었으며 자식계통간에 차이가 있었다. 2. 하부이삭의 적장은 상부이삭에 비하여 평균 36% 정도 짧았으며, 자식계통 NC246은 하부 이삭이 발육출사되지 않아 자식계통간의 차이를 나타냈다. 3. 하부이삭의 이삭열수와 열당립수는 각각 28%, 37% 적었고 수당립수는 43% 적었으며. 자식계통간의 감소 범위는 0∼82% 이었다. 4. 수양구성 요소중에서 100입중의 감소 정도가 가장 적었고, 수장과 수양구성 요소에 대한 변리계수는 상부이삭에 비하여 하부이삭에서 약 2배 정도 컸다.

6개 자식계통 찰옥수수에 의한 이면교배 조합(역교배 불포함)에 대하여 식물학적 특성과 이삭 관련 특성들에 대하여 조사한 것을 요약하면 다음과 같다. 1. 6개 자식계통들의 개화기, 간장, 착수고, 엽면적 및 수경의 길이는 각 계통들 간에 차이가 있었다. 특히 보성 계통의 수경길이가 24.4cm였는데 반하여 칠보 계통은 9cm에 불과하였다. 2. 6개 자식계통들의 이삭길이, 이삭직경, 100립중, 이삭속길이, 열수 및 이삭당 립수 등 역시 계통간에 큰 차이가 있었다. 특히 보성 계통은 이삭 길이가 13.4cm로 계통 중 가장 컸으나 이삭 직경과 열수와 이삭당 총 당수가 가장 낮았으며, 100립종은 가장 무거웠다. 반면 당진 계통은 이삭 길이가 9.3cm로 짧은 대신에 이삭직경이 크고, 또 열수도 비교적 많아 이삭당 당수가 282개로 가장 많았다. 3. 자식계통들의 10a당 곡실 수량을 보면 분얼을 하고 다수성인 제원 계통이 285kg으로 가장 많았다. 4. 15개 교잡종들이 자식계통 특성 가운데 개화기, 간장, 착수고, 엽면적 등은 교배조합에 따라 큰 차이를 보였다. 5. 15개 교잡종들의 이삭관련 특성을 보면 보성 계통을 양친으로 한 조합들은 이삭길이가 길었고 100립종도 무거웠다. 반면에 당진 계통의 교잡종들은 이삭길이가 짧았다. 6.풋옥수수 수량이 높았던 것은 보성 계통과 교배된 조합들 이었으나, 곡실수량에서는 당진과 교배된 조합들이었다. 7. 당진계통의 일반조합능력은 교잡종의 간장과 착수고를 낮게 하는데 효과적이었다. 8. 제원계통은 교잡종들의 분얼수를 증가시키는 방향으로 일반조합능력이 컸다. 9. 이삭의 길이, 100립종, 열수 등 이삭 관련 형질에 대한 일반조합능력 효과는 보성 계통이 컸고, 종실 수량에 대한 일반조합능력이 컸던 계통은 제원과 단양 계통이었다. 10. 이삭의 길이, 100립종 등에 대한 특수능력이 컸던 조합은 제원/칠보조합이었고, 종실 수량에 대한 특수조합능력이 컸던 계통은 보성/당진이었다.