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.

Is backcrossing a good strategy for improving elite lines for quantitative traits in general? Results reported here demonstrate the effectiveness of a backcrossing program for improving quantitatively inherited disease resistance traits, which are strongly influenced by the environment. Through backcross breeding, we were able to improve an important commercial inbred line, FR1064, for ear rot and fumonisin contamination resistance without significantly lowering its yield potential, even with the use of a donor line with poor agronomic potential. Following one generation of selection on advanced backcross-derived lines, gains were observed for the primary trait of interest in advanced inbred generations. Following two generations of selection, we improved potential performance for ear rot resistance and reduced fumonisin accumulation in the 19 selected lines without significantly affecting important agronomic characteristics such as plant height, ear height, or flowering time compared to the recurrent parent, FR1064. The 19 selected lines were also significantly more resistant to ear rot under inoculated conditions than the FR1064 topcross without exhibiting significant reductions in topcross grain yield or other agronomic traits. Several individual lines were identified that were not statistically different from GE440 for ear rot or fumonisin content as inbreds or from the GE440 topcross for ear rot. These lines exhibited topcross yields comparable to the FR1064 topcross, although they were not competitive with commercial check yields. Thus, from a practical standpoint, the backcrossing method was effective at improving quantitative disease resistance in an elite commercial line using an unadapted donor parent. We also genotyped selected lines at DNA markers linked to ear rot and fumonisin resistance quantitative trait loci (QTL) identified in the BC1 generation of this cross to determine which QTL demonstrated allele frequency shifts due to selection.

Northern corn leaf blight caused by Exserohilum turcicum Pass is considered the most important disease infecting corn (Zea mays L.) in the Peoples' Republic of Korea (North Korea). It contributes to the food shortage in North Korea. The objectives of the current research were to study resistance expression and responses of corn crosses made between ten hybrids from North Korea and inbreeding lines (S3-4 stage) from the Republic of Korea (South Korea). The experiments were conducted in six trials with a total of 184 crosses including two commercial hybrids in each trial. The trials were conducted at two locations in North Korea (Mirim and Eunsan) and one location in South Korea (Gunwi) under natural infestation of E. turcicum. Host plant responses were rated on a scale of 1 (highly tolerant) to 9 (highly susceptible). A total of 111 crosses (62.4%) showed significant tolerant or susceptible response variations among three locations; 42 crosses (22.8%) at two locations and 69 crosses (39.0%) at one location, respectively. At least 8 crosses of high level of tolerance and 12 crosses of high level of susceptibility showed significantly different biotic responses (P = 0.05). The results of the current study and historical reviews of E. turcicum epidemics in both North and South Korea suggest that breeding of tolerance with quantitatively inherited genes should be carried out for a sustainable corn production in North Korea.

옥수수 우량 교잡종 육성을 위한 자료로 활용하고자 국내 육성 옥수수 자식계통, F1 종실 및 F2 종실의 이화학적 특성과 지방산 및 아미노산 조성을 각각 분석 검토하였다. 1. F2 종실의 단백질 함량이 9.0%로 자식계통 11.4%와 F1 종실 10.9%에 비하여 유의하게 낮은 것으로 나타났다. 지방 함량은 F2 종실이 자식계통과 F1 종실보다 높았다. 회분은 자식계통, F1 종실, F2 종실간 조성변이에 차이가 없었다. 2. 자식계통, F1 종실, F2 종실 모두 linoleic acid의 조성비가 가장 높고 oleic acid, palmitic acid, stearic acid, linolenic acid의 순으로 지방산 조성비가 높은 것으로 나타났다. F2 종실의 포화지방산의 함량은 17.6%로 F1 종실과는 비슷하였으나, 자식계통보다는 낮았다. F2 종실의 불포화지방산의 함량은 82.4%로 F1 종실과는 비슷하였으나, 자식계통보다는 높았다. 3. F2 종실의 leucine의 함량이 자식계통 및 F1 종실보다 낮았다. 반면 F2 종실의 valine, serine, threonine, cysteine, aspartic acid, lysine, arginine, histidine 등의 함량이 자식계통 및 F1 종실보다 높았다. Alanine 등 나머지 아미노산은 자식계통, F1 종실, F2 종실간 조성변이가 비슷한 경향이었다. 4. 산성아미노산인 MMA(monoamino monocarboxylic acid)가 자식계통, F1 종실, F2 종실에서 그 조성 비율이 가장 높았으며 산성 아미노산인 DMA(diamino monocarboxylic acid), 방향족 아미노산인 AAA(aromatic amino acid) 순으로 조성비가 높았다.

본 연구는 총 50개의 SSR 마커를 이용하여, 찰옥수수 및 종실용 옥수수 핵심집단(찰옥수수 40계통, 종실용 옥수수 40계통)의 자식계통들의 유전적 다양성, 집단구조 및 계통유연관계를 분석하였다. 1. 그 결과 65bp에서 225bp 크기의 범위로 총 242개의 대립단편들을 증폭시켰다. SSR primer들에서 증폭된 대립단편의 수는 최소 2개에서부터 최대 9개까지의 범위로 나타났고, 평균 4.84개가 증폭되었다. 그리고 GD값은 0.420에서 0.8

The effect of nitric oxide (NO) on antioxidant system and protective mechanism against oxidative stress under UV-B radiation was investigated in leaves of maize (Zea mays L.) seedlings during 3 days growth period. UV-B irradiation caused a decrease of leaf biomass including leaf length, width and weight during growth. Application of NO donor, sodium nitroprusside (SNP), significantly alleviated UV-B stress induced growth suppression. NO donor permitted the survival of more green leaf tissue preventing chlorophyll content reduction and of higher quantum yield for photosystem Ⅱ than in non-treated controls under UV-B stress, suggesting that NO has protective effect on chloroplast membrane in maize leaves. Flavonoids and anthocyanin, UV-B absorbing compounds, were significantly accumulated in the maize leaves upon UV-B exposure. Moreover, the increase of these compounds was intensified in the NO treated seedlings. UV-B treatment resulted in lipid peroxidation and induced accumulation of hydrogen peroxide (H2O2) in maize leaves, while NO donor prevented UV-B induced increase in the contents of malondialdehyde (MDA) and H2O2. These results demonstrate that NO serves as antioxidant agent able to scavenge H2O2 to protect plant cells from oxidative damage. The activities of two antioxidant enzymes that scavenge reactive oxygen species, catalase (CAT) and ascorbate peroxidase (APX) in maize leaves in the presence of NO donor under UV-B stress were higher than those under UV-B stress alone. Application of 2-(4-carboxyphenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3- oxide (PTIO), a specific NO scavenger, to the maize leaves arrested NO donor mediated protective effect on leaf growth, photosynthetic pigment and free radical scavenging activity. However, PTIO had little effect on maize leaves under UV-B stress compared with that of UV-B stress alone. Nω -nitro-L-arginine (LNNA), an inhibitor of nitric oxide synthase (NOS), significantly increased H2O2 and MDA accumulation and decreased antioxidant enzyme activities in maize leaves under UV-B stress. This demonstrates that NOS inhibitor LNNA has opposite effects on oxidative resistance. From these results it is suggested that NO might act as a signal in activating active oxygen scavenging system that protects plants from oxidative stress induced by UV-B radiation and thus confer UV-B tolerance.

본 연구는 유전자 조작 옥수수의 유전자 유출을 막기 위한 관리방법 개발의 목적으로 고려대학교 GMO 격리포장에서 2010년에 수행된 화분 비산실험의 결과를 이용하여 Yamamura(2004)의 Gamma model로 모델링하였다. 1. 모델의 결정계수는 0.44로 예측치가 실측치를 잘 설명하였다. 2 옥수수 화분의 최대 비산 방향은 북서쪽으로 나타났다. 3. 최대 비산 방향으로 타가수분율이 0.001까지 낮아지는 거리인 '유전자유출 한계거리(0.001)'는 525 m 그리고 국내법상 비의도적 GMO 혼입허용치인 0.03 까지 낮아지는 거리인 '최소 동일작물 재배 한계거리(0.03)'는 35 m로 나타났다.

2007년부터 2009년까지 3년간 보리이모작으로 옥수수를 6월 만파 시 사료용 및 종실용으로의 생육 및 수량변화를 2007 및 2009년의 4월 하순 적파 및 2008년 5월 하순 옥수수와 대비하여 살펴보았는데 그 결과는 다음과 같다. 1. 4월 하순 적파에 비해 보리 이모작으로 6월 중 하순 만파 시 옥수수의 생육 많이 감소하여 사료 종실의 수량성이 20~30% 감소하였지만, 이모작으로 동계 재배한 보리의 사료 종실의 수량성을 합할 경우 년간 전체 수량성은 30~40% 증가하였다. 2. 6월 만파 시 옥수수 부위별로는 간엽보다 이삭(종실)의 감소가 적었다. 사료 및 종실용으로 수량감소가 가장 적었던 품종은 광평옥이었으며, 6월 만파에서도 850 kg 10a1의 수량성을 얻을 수 있었다. 따라서 이모작 옥수수는 사료용 보다 종실용으로 만파적응 품종 및 재배법의 개발이 필요한 것으로 나타났다. 3. 6월 만파 옥수수는 4월 적파 옥수수보다 유효적산온도의 증가와 더불어 출사일수는 40일 가량 단축되었고, 만파에 따라 출사기는 1달 정도 늦어 수확적기는 사료용이 9월 하순, 종실용이 10월 중순으로 4월 적파 옥수수에 비해 수확 시 기후조건은 좋은 것으로 나타났다.

Maize (Zea mays.L) is the third important crop after wheat and rice in Afghanistan. The productivity is low 2.14 ton/ha due to lack of diversity and well-adapted varieties. 65% of maize production is used as feed and 17.5% as food. Afghanistan is facing seriously malnutrition and poverty, therefore more maize is required to recover food security. Popcorn is also important snack food in Afghanistan, but it is luck of breeding donors. The main objective of this work is to evaluate and identify the introduced hybrids of Korean germplams. International Corn Foundation (ICF), Kyungpook National University (KNU) and Institute of Asian Culture and Development (IACD) collaboratively planted three different types of maize (Silage1, KNU waxy1, Popcorn) in two locations (Isharak and Sherabad) in Mazar-i-sharif. All hybrids have shown good performances and can easily be adapted in Afghanistan climate. Among them KNU waxy1 was the most attractive which has been planted first time. Farmers showed highly interest on new taste and they were so enthusiasm to replant. Maize breeding laboratory at KNU is developing new popcorn cultivar for commercial use in Korea that has shown outstanding result in Afghanistan climate. This experiment described that introducing of new maize hybrids especially KNU waxy1 and popcorn can have great potential to fill up food demand in Afghanistan.

Maize (Zeae mays L.) is a second important crop in the country and it is first staple food in high land region. The national average yield is 2.2 t/ha. About 80% maize areas falls in this region. An introduced fungus Gray Leaf Spot (GLS) caused by Cercospora zeae-maydis has caused yield loss an average of 75%. Genetic resistance has been effective control strategy to manage this disease. The main objectives of this work were to develop, evaluate and identify high yielding cultivars tolerant to GLS. Three sets of trials were conducted in Nepal and Korea. GLS evaluation trial-I consisted of 73 genotypes, GLS evaluation trial-II composed of 38 genotypes and mid altitude hybrid evaluation trial-III consisted of 12 genotypes. Exotic, semi exotic and local germplasm of different origins were used. Among these tested genotypes, tolerant genotypes were Thai 717S31-21-3×[TZMi407 × TZMi211-11- 2-1-1-B-B-B-B-B (5.2t/ha), Pioneer12 × MASynVAR-5 F2 (5.0 t/ha) and MA SynVAR-5 F2 × Thai 919 S3 4-5-4 (4.7t/ha) with GLS mean score 2.7, 1.5 and 1 respectively in trial-I. In trial-II, superior genotypes were KYM33 × TZi3 (7.6t/ha), KYM33 × TZi18 (7.5 t/ha) and KYM33 × P45 (7.4 t/ha) with GLS scores 1.4, 2.4 and 2.5 respectively. Similarly in trial-III, high yielding genotypes were MASynVAR-5 (11.0t/ha), and TZMi407×87036- 9-1-1-1-B-B-B/TZMi102×90113-5-3-2-2-B-B-B-B (9.8t/ha). These hybrids and their parents will use to introgress resistant genes to breed better tolerant maize cultivars for Nepal.

Downy mildew (DM) caused by the fungus Peronosclerospora sorghi is one of the most serious diseases reducing maize (Zea mays L.) production in East Timor. We have conducted three trials of DM resistant (R) and non-DMR source populations in three locations; Loes, Dili and Lospalos. Materials were developed by using DMR-ESR-Y and MO5-5-RUVT-EE (TZEE-Y) (IITA) and Suwan 5 (Thailand). Three sets of random mating, incomplete diallel crosses and parent populations were planted with three replications in one meter row with RCBD. Data assessment of DM infection was rated based on 1 – 9 rating score (1 = highly tolerant and 9 = highly susceptible) from 2 and 4 weeks before flowering. In Comoro, Dili, 32 genotypes exhibited very low DM infection with coefficient of variance and mean 17.2% and 3.9, respectively. BISI-2 (Indonesian hybrid) and TH2 (Timor Hybrid 2 crossed from two DMR OPVs, Indonesian Arjuna and Suwan 5) showed outstanding commercial value (CV). Twelve cultivars of MO5 were varied in CV. At Loes Research Station, genotypes showed high variation in DM infection. Average heterotic effect of 36 F1 crosses for DM tolerance was 29.5%. Mean parent value and F1 indicated negative correlation for DM infection. The result showed that to breed high resistance is difficult. However, breeding for host tolerance with polygenic system with a threshold nature is possible.

Maize is expected to be planted in June after harvest of winter barley for the double cropping of forage maize-barley. But maize yield tends to be reduced rapidly with late planting after mid-May, so the pre-requisite of maize variety for the double cropping of maize-barley is less reduction of growth and yield at the condition of late planting in June. In order to select domestic forage maize variety adapted to late planting in June after barley harvest, Kwangpyeong-ok, Gangda-ok and Jangda-ok in 2007 and Kwangpyeong-ok, Gangda-ok and Cheongan-ok in 2008 were planted on June 13 and June 21, and plant growths and yields were compared with early planting on April 24 and May 31, respectively. In 2007, Ear number per plant was as high as 0.98 at Kwangpyeong-ok compared to 0.89 and 0.56 of Gangda-ok and Jangda-ok, respectively, at late planting on June 13. TDN and grain yield of Kwangpyeong-ok were the highest among three variety as 1,037 and 710 kg/10a, and yield reduction of Kwangpyeong-ok compared to early planting were 24% and 28 %, which were 7% and 8% lower than Gangda-ok and 22% and 50% lower than Jangda-ok, respectively. In 2008, TDN and grain yield at late planting on June 21 of Kwangpyeong-ok were also the highest among three varieties as 1,157 and 854 kg/10a at late planting on June 24, and yield reduction of Kwangpyeong-ok by late planting were 21% and 19%, which were 10% and 11% lower than Gangda-ok and 22% and 50% lower than Jangda-ok, respectively. It was concluded that proper maize variety adapted to late planting for the double cropping of forage maize-barley was Kwangpyeong-ok because of its higher ear bearing, less reduction of TDN and grain yields at the condition of late planting.

평안옥은 자식계통 KS140과 KS94의 교잡으로 육성된 다수성인 단교잡종이다. 2005년 생산력검정시험을 거쳐, 2006~2008년 3년 동안 4지역에서 지역적응시험을 실시한 결과 그 우수성이 인정되어 2008 농작물 직무육성 신품종선정위원회에서 신규우량품종으로 결정되었다. 이 품종의 주요특성을 요약하면 다음과 같다. 1. 평안옥의 종피색은 황색이며 입질은 반경립종이고, 출사일수는 광평옥보다 3일 늦다. 간장 및 착수고는 광평옥과 비슷하였으며, 후기녹