The different forms of flowers in a species have drawn thoughtful attention of many evolutionary botanists, including Charles Darwin. Common buckwheat (Fagopyrum esculentum Moench.) is regarded as a dimorphic self-incompatible plant which bears either a pin or a thrum flower. It is revealed that the S supergene the key element to govern the self-incompatibility, flower morphology, and pollen size. Already, we have produced self-incompatible buckwheat lines by an interspecific cross between F. esculentum and F. homotropicum by using embryo rescue. We also notice that the self-compatibility allele, Sh, keeps up the heteromorphic incompatibility. In the past decades, two dimensional gel electrophoresis based proteomics approaches have been applied systematically to identify and profile proteins expressed during pollen development of model plant species. Proteome techniques have vastly been applied in the fields of plant genetics, plant development, and plant physiology and ecology to reveal plant genetic diversity, plant development, differentiation of plant tissue and organ, separation and functional identification of novel component of various organelles, mechanisms of plant adapted to abiotic or biotic stresses including high temperature, low temperature, high salt, drought, and pathogens and insects, and interaction of plant with microbe. However, the plethora of studies related to heteromorphic has added remarkably to our knowledge in the field of the multiple aspects of the breeding system and many researches have provided evidence for the connection between these two components. But in spite of its potential biological significance, the high throughput proteomics analysis of this connection has so far been grossly overlooked. So our attempts are to unravel the proteome investigation in common buckwheat.

Among the abiotic stresses, heavy metal (HM) toxicity is thought to be one of the major abiotic stresses leading to hazardous effects in plants. In spite of its potential physiological and economical significance, morphological alterations induced by heavy metals in plants have so far been grossly overlooked. In the present study, the morphological and physiological changes were observed in the leaf of sorghum plants treated with different concentrations (0, 50, 100, and 150 μM) of CdCl2. Results revealed that plants endured reduction in growth and morphological changes amazingly altered by cadmium. The growth of sorghum seedlings treated with 150 μM cadmium was more inhibited than that of sorghum seedlings treated with 100 μM Cd, 50μM and non-treated plants. The morphological characteristics revealed that the cadmium stress inhibited the root and shoot elongation after growing the rise seedling in the presence of cadmium. In the case of ion concentration, the concentrations of Zn2+, Ca2+ were decreased whereas Fe2+ concentration was increased except 100 μM under cadmium stress. In confocal microscopy, results showed that the absorption degree of cadmium was increased by the higher concentration of cadmium. The fluorescence intensity of cadmium was also increased. Thus, it seemed that cadmium has an influence on sorghum in the case of early stages of sorghum. This study reported the effects of heavy metal, cadmium on the growth and physiological characteristics of sorghum seedlings, hoping to provide references on the mechanism of heavy metal damaging plants, and phyto-remediation for heavy metal polluted soil.

국산밀을 재배하는 전국 175농가를 대상으로 2년 동안 재배 현황에 대한 자료를 수집· 분석한 결과, 평균 재배 경력과 재배면적은 7.7년과 2.4～3.3 ha였으며, 재배 품종은 금강밀이 주로 재배되었고 조경밀과 백중밀이 남부지역에서 재배 면적이 늘어나고 있다. 파종은 대부분 농가에서 10월 하순에서 11월 상순에 휴립광산파로 이루어지고 있으며, 시비는 2종 복합비료를 이용하여 평균 29.7 kg/10a이상 기비로 시용하였으며, 추비는 2월 하순～3월 상순에 질소비료를 1회 시용하는 농가가 주를 이루었는데, 농가 현장에서 표준시비량에 비해 과량의 비료가 시용되고 있기 때문에 적정 시비에 대한 관리가 필요하다. 재배 밀의 출수는 기상 영향으로 2011년은 5월 상순, 2012년은 4월 하순에 이루어졌으며, 밀 수확은 대부분 농가에서 6월 중순에 이루진 것으로 나타났다. 재배 면적 확대와 밀 재배 농가 소득 향상을 위하여, 수발아 및 붉은곰팡이병 저항성 증진과 기상이변에 대응할 수 있는 재해저항성 증진 품종 개발이 이루어져야하며, 국산밀 품질 향상을 위한 보급종 생산 및 확대가 필요하며, 지역별 밀 재배 농가의 규모화에 대한 지원과 재배 관리 체계 확립과 현장 지원 확대가 필요하다.

Buckwheat sprout is used as vegetable, and also flour for making noodles, and so on. Currently, information about tissue culture in buckwheat is limited and restricted to micro-propagation. We carried out somatic embryogenesis and plant regeneration using hypocotyl segments as explant of the cultivated buckwheat species, Fagopyrum esculentum which differs from existing studies in the growth regulator combinations used. Maximum callus regeneration was induced on MS medium containing 2,4-dichlorophenoxyacetic acid (2,4-D) 2.0 mg · L-1, benzyladenine (BA) 1.0 mg · L-1 and 3% sucrose. Friable callus was transferred to solidified MS media containing BA (1.0 mg · L-1) with various concentrations of 2,4-dichlorophenoxyacetic acid for the induction of embryogenesis. The optimum concentrations of growth regulators (for regeneration of plantlet) were indole-3-acetic acid (2.0 mg · L-1), Kinetin (1.0 mg · L-1), BA (1.0 mg · L-1). Only 2,4-D did not show any significant effect on callus induction or embryogenesis. Regeneration of embryonic callus varied from 5% to 20%. Whole plants were obtained at high frequencies when the embryogenic calli with somatic embryos and organized shoot primordia were transferred to MS media with 3% sucrose. The main objective of this research was to develop an efficient protocol for plant regeneration for common buckwheat, and to apply in future for genetic transformation.

국산밀을 재배하는 전국 175농가를 대상으로 2년 동안 농업형질과 원맥 특성을 조사 한 결과, 간장, 수장, 경수와이형주율은 년차간 차이를 나타내었다. 시비량이 많았던 남부지역에서 재배된 밀의 간장이 중북부 지역 보다 길었으며, 추비시기는 간장에 영향이 없었지만, 3월 중순 이후에늦게 추비를 준 농가의 수장은 다른 농가에 비하여 길었으나 경수는 감소하였다. 추비 횟수는 농업형질에 영향을 미치지 않는 것으로 나타났다. 농업형질과 마찬가지로 원맥특성도 연차간 변이가 있었으며, 남부지역에서 재배된 밀은중북부지역에서 재배된 밀에 비하여 천립중이 높았으며, 리터중은 낮았으며, 전라북도는 다른 지역에 비하여 낮은 회분 함량과 높은 단백질 함량을 나타냈으며, 전라남도는 다른 지역에 비하여 높은 회분 함량을 나타내었다. 추비시기가 리터중에는 영향을 주었지만 천립중과 회분 및 단백질함량에는 영향을 주지 않았으며, 추비 횟수도 원맥 특성에영향이 없는 것으로 나타났다. 시비량에 따라 간장이 증가하고, 천립중과 단백질 함량이 증가하였으며, 수장과 회분함량은 시비량과 부의 상관을 나타내었다. 단백질 함량은천립중과 정의 상관을 나타내었지만 회분 함량은 천립중 및리터중과 부의 상관을 나타내었다. 간장이 증가할수록 천립중은 증가하고 리터중은 감소하였으며, 수장은 천립중과 부의 상관을 나타내었다. 시비량이 간장 및 원맥 특성에 영향을 미치기 때문에 품종별 용도에 맞는 밀 품종을 재배하기위해서는 적정 시비기술에 대한 농가 지도가 필요하다. 또한, 국산 밀의 생산성 증진과 품질 향상 및 균일성 확보를위해서는 용도별 가공적성에 적합한 품종에 대한 집단 재배단지를 조성하고 철저한 생산 관리와 체계적인 수확 후 관리 구축에 대한 종합적인 고려가 있어야 할 것이다.

In U.S.A. maize breeding, exotic germplasm is considered as high-risk and usually introduced by backcrossing specific traits into elite lines. The U.S.A. maize germplasm base is narrow. Only a few open-pollinated varieties are well represented in current programs. Currently, the barrier in using of exotic germplasm in the U.S.A is less formidable than in the 1980s. The major reason is that U.S.A materials are now used in tropical breeding to accelerate earlier maturity and lodging resistance. These exotic materials, developed with U.S.A germplasm, are being introduced back into the U.S.A.Since1994, the ARS-led Germplasm Enhancement of Maize (GEM) project has sought to help broaden the genetic base of America’s corn crop by promising exotic germplasm and crossing it with domestic lines. New hybrids derived from such crosses have provided corn researchers and the producers. These may include improved or alternative native source of resistance to insect pests such as corn rootworms and diseases like northern leaf blight. GEM’s aim is to provide source of useful genetic maize diversity to help the producers to reduce risks from new or evolving insect and disease threats or changes in the environment or respond to new marketing opportunities and demand. During the 2009 growing season, the Ames (Iowa) and Raleigh (North Carolina) locations managed or coordinated evaluations on 17,200 nursery plots as well as 14,000 yield trial plots in Ames and 12,000 in Raleigh. A new “allelicdiversity” study is devoted to exploring and capturing the genetic variation represented by over 300 exotic corn races. Since 2001, GEM has released 221 new corn lines to cooperators for further development into elite commercial new hybrids. GEM has already identified about 50%-tropical, 50%-temperate families tracing primarily to tropical hybrids that are competitive with commercial checks. In North Carolina State University program, they have examined the potential of tropical inbredand hybrids for U.S.A. breeding by crossing temperate-adapted, 100%-tropical lines to U.S.A hybrids. There should be favorably unique alleles or genomic regions in temperate germplasm that can be helpful in tropical maize improvement as well as utilization of tropical lines in temperate areas.

Common buckwheat has the sporophytic self-incompatibility mechanism and that’s why it has the ability to cross pollinate between two plants with different styles (thepin type and thrum type). The S supergene is thought to govern self-incompatibility, flower morphology and pollen size in buckwheat. Already, we have produced self-compatible buckwheat lines by an interspecific hybridization between Fagopyrum esculentum and F. homotropicum by embryo culture. The pollen size of F1 plants produced by a cross between a pin type plant and the self-compatible plant was similar to that of the self-compatible lines and segregated together with flower morphology without exception. The pollen tubes of the self-compatible plants were compatible with styles of the pin plants but incompatible with the styles of thrum plants. But, the pollen tubes of thrum flowers were compatible with the styles of self-compatible plants. Also, the pollen tubes of pin flowers were incompatible with the styles of self-compatible plants. Already, from these results, we have reported a tentative genotype for heterostyle and homostyle flower types. Homomorphism was controlled by a single allele Sh, while the pin/thrum-complex gene was governed by a single genetic locus S, with two alleles, S and s, which control Ss (thrum-type) as well as the ss (pin-type), respectively. Corresponding represents the case of a single locus S with three alleles, Sh, S and s, and the phenotypes, homomorphic, pin and thrum. It can be characterized by relationship of dominance, S>Sh>s. Using the two self-fertile lines, one is considered as the long-homostyle flowers and the other is considered as the short homostyle flowers. If the short-homostyle trait had arisen by recombination in the S supergene, its genotype would be considered to be GIs ip a/GIs ip a. The pollen tubes of the short-homostylous plant should be compatible with the styles of thrum plants. Also, the pollen tubes of short-homostylous plants should be incompatible with the style of long-homostylous plants, and the reciprocal cross also should be incompatible, because the genotype of long homostyle is gis Ip PA/gis Ip PA. Furthermore, the flower morphology of F1plants produced by the cross between cross and short homostyle flowers should be thrum or short homostyle and only short-homostylous plants should be produced by the cross between pin and short homostyle flowers. However, the compatibility or incompatibility of short homostyle flower was not clarified. So, we need to clarify the compatibility or incompatibility of the style of short homostyle flowers for the next step.

Sub-cellular proteomics provide insight into the molecular mechanisms of plant cell modulation of protein accumulation in intracellular compartments regarding various perturbations, and thus provides rectified knowledge about signal transduction in organelles. Mitochondria are important organelles for cellular respiration within the eukaryotic cell and serve many important functions including vitamin synthesis, amino acid metabolism and photorespiration for the cell as well. To define the mitochondrial proteome of the roots of wheat seedling, a systematical and targeting analysis were carried out on the mitochondrial proteome from 15 days-old wheat seedling roots material. Mitochondria were isolated by Percoll gradient centrifugation; and extracted proteins were separated and analyzed using Tricine SDS-PAGE along with LTQ-FTICR mass spectrometry. From the isolated mitochondrial proteins, a total of 140 proteins were identified. The identified proteins were functionally classified into 12 classes using ProtFun 2.2 server based on cellular roles, Proteins were shown to be involved in including amino acid biosynthesis (17.1%), biosynthesis of cofactors (6.4%), cell envelope (11.4%), central intermediary metabolism (10%), energy metabolism (20%), fatty acid metabolism (0.7%), purines and pyrimidines (5.7%), regulatory functions (0.7%), replication and transcription (1.4%), translation (22.1%), transport and binding (1.4%), and unknown (2.8%). These results indicated that many of the protein components present and functions of identified proteins are common to other profiles of mitochondrial proteomes performed to date. The data presented here will begin to reveal a better understanding the characteristics of proteins and metabolic activity in mitochondria in wheat roots.

High temperature impediment in developing stages of crops has been occurred due to the impact of global warming. Rice production is notable to be sensitive to increasing environmental temperature and grain filling temperatures are already approaching threatening levels in many countries with rice cultivation. Recent proteomic analyses exposed impulsive changes of metabolisms during rice grain development. Interestingly, proteins involved in glycolysis, citric acid cycle, lipid metabolism, and proteolysis were accumulated at higher levels in mature grain than those of developing stages. High temperature (HT) stress in rice ripening period enhances damaged (chalky) grains which have loosely compacted shape starch granules. We carried out two-dimensional gel electrophoresis to analyze protein profiles during grain filling and different developmental stages of rice seed maturation. Proteins were separated from the fertilized seeds (seeds from 7 days and 21 days after fertilization) and seed maturation stage using IEF in the first-dimension and SDS-PAGE in the second dimension along with MALDI-TOF mass spectrometry. More than 1,000 protein spots were detected on a two-dimensional gel electrophoresis. A total of 120 different protein spots out of 140 protein spots were identified by MALDI-TOF and nano LCQ-TOF mass spectrometer. The identified proteins were categorized into six (6) different groups according to their expression patterns during grain filling and seed maturation. Some proteins were confirmed during seed development stages such as cytoplasmic malate dehydrogenase, whereas others were appeared at a specific stage like putative subtilisin-like protease, germin-like, seed allergenic proteins. Furthermore, the chalking mechanism of rice grain under the HT stress could be discussed in terms of grain starch glycome, transcriptome, and proteome.

Grain sorghum (Sorghum bicolor) is a major staple for a large portion of the world. The crop ranks fifth among the cereals world-wide with respect to its importance for food and feed applications. To this end, the grain harvested from sorghum, and the millets provides an important source for dietary calories and protein for approximately one billion people in the semi-arid regions of the world. However, grain sorghum products are known to have relatively poor digestibility, only approximately 50%–70%, in comparison with other grains, such as wheat and maize, which tend to have digestibility percentages over 80% and 70%, respectively. Protein with high digestibility is by definition nutritionally superior owing to the increased availability of amino acids. Digestibility can be impacted by both protein–protein and⁄or protein–nonprotein interactions. However, with respect to grain sorghum, it is thought that the major factor influencing digestibility is the former because of high protein cross-linking around the protein body. To understand the mechanism of seed storage proteins in the sorghum, the proteomic analysis was carried out between the wild(BTX623) and mutant(M271207) genotypes of sorghum. Proteins were separated from the mature seed using IEF in the first-dimension and SDS-PAGE in the second dimension along with hybrid LTQ-FTICR mass spectrometry. After image analysis using Progenesis SameSpot software, we identified the 62 differential expressed protein spots out of 293 protein spots. Out of total differential expressed spots, 35 differential expressed protein spots (more than2-fold) were analyzed by mass spectrometry. Out of 35 protein spots, we were identified 20 protein spots as up-regulated and 15 protein spots as downregulated, significantly. In our proteomic investigation, the candidate proteins may provide novel clues for better understanding the characteristics of seed proteins in Sorghum.

The antioxidant enzyme and DPPH radical scavenging activity with variations in drying methods of diploid and tetraploid in Platycodon grandiflorum were determined. Antioxidant enzyme activities were measured as superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), and ascorbate peroxidase (APX). The roots of Platycodon grandiflorum were freeze-dried, indoor-dried, hot-air dried, and microwave dried. The root extract of P. grandiflorum have shown the highest SOD enzyme activity of 92% in tetraploid of freeze-dried and indoor-dried while diploid of microwave dried showed the lowest SOD enzyme activity of 47.5%. The activity of CAT showed higher values in the root of tetraploid than in the diploid of P. grandiflorum in all drying methods. The APX activity showed relatively higher values in the root extract of freeze-dried both the diploid and tetraploid, but the difference in comparison with other extracts was not significant. The POX activities according to drying methods of diploid and tetraploid in P. grandiflorum showed relatively high values in freeze-dried and indoor-dried compared with other drying methods, and the POX activity between the diploid and tetraploid was not significant difference in each drying method. The DPPH radical scavenging activity with variation in drying methods of diploid and tetraploid in P. grandiflorum was the highest in the freeze-dried, and was higher in tetraploid than diploid in all the concentrations. In conclusion, the root of P. grandiflorum had the potent biological activities in both diploid and tetraploid. In particular, the tetraploid root of P. grandiflorum showing high antioxidant enzyme activity could be good materials for development of source of functional healthy food.

Allelic variations in glutenin and puroindolines of 26 Korean wheat cultivars were evaluated to determine their effects on the physicochemical properties of flour and quality of white salted noodles. Cultivars carrying Pina-D1b and Pinb-D1b exhibited a coarser particle size of wheat flour and a higher ash and damaged starch content than those with Pina-D1a and Pinb-D1a. Glu-B1b, Glu-D1f, Glu-B3d and Pina-D1a alleles exhibited lower protein content than other alleles. Glu-A1c, Glu-B1b, Glu-D1f Glu-B3d, Glu-B3i and Pinb-D1b alleles appeared to be related to a lower SDS-sedimentation volume than other alleles. In dough rheological properties, Glu-A1a and Glu-D1d alleles showed a longer mixing time on the mixograph and maximum dough height but Glu-A3e and Glu-B3i alleles had a lower mixing time on the mixograph and a lower maximum dough height than other alleles at Glu-1 and Glu-3 loci. Regarding the quality of white salt noodles, about 10% of the variations in the hardness of cooked noodles were explained by Glu-A1 and Glu-B3 loci. Hardness rankings of cooked noodles were Glu-A1a > Glu-A1c > Glu-A1c at the Glu-A1 locus. Glu-B3h showed higher cooked noodle hardness (5.10 N) than other alleles at the Glu-B3 locus (< 4.66 N).

Cereal seeds, sorghum, foxtail millet, hog millet, adlay, and corn are traditionally used as health assistant as well as energy supplying food in Korea. While beneficial phytochemicals to human have revealed in cereals, the information on peptides from cereals is far less accumulated than major reserve protein. Here, we analyzed peptide profiles using surface enhanced laser desorption/ionization time of flight mass spectrometry (SELDI-TOF MS) in cereal seeds for construction of peptide information and attempted to develop peptide biomarkers for cereal identification. To optimize the analysis condition of SELDI-TOF MS, the effect of dilution factor on binding affinity to protein chips was tested using CM10 and Q10 arrays. Peptide clusters were significantly different at the level of 0.01 p-value. Peak spectra were the most stable in 1:50 of dilution factor in both chip arrays. Numbers of detected peak of 5 cereal seeds were 131 in CM10 and 74 in Q10 array. Each cereal was grouped as a cluster and well discriminated into different cluster in the level of 0.01 p-value. Numbers of potentially identified peptide biomarkers are 11, 13, 9, 5 and 12 in sorghum, foxtail millet, hog millet, adlay and corn, respectively. This study demonstrates that each cereal seed have own distinguishable specific peptides although their function are not identified yet in this study. In addition, the proteomic profiling using SELDI-TOF MS techniques could be a useful and powerful tool to discover peptide biomarker for discrimination and assess crop species, especially under 20 kDa.

Recently, proteome analysis is becoming a powerful tool for the functional characterization of plants. Due to the availability of vast nucleotide sequence information and based on the progress achieved in sensitive and rapid protein identification by mass spectrometry, proteome approaches open up now perspectives to analyze the complex functions of model crop species at different level. In this study, we have N-terminal sequencing data for the 100 embryo and 53 seed proteins of rice separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) were collected and systematically organized for a protein sequence data-file. An attempt was made to link the embryo proteins of rice to DNA sequences for understanding their functions. One hundred proteins of the 700 spots were detected in the embryo using 2-DE gels whereas we used micro sequenced. Of these, 28% of the embryo proteins were matched to DNA sequences with known functions, but 72% of the proteins were identified to be unknown functions as previously reported by Woo et al.,. In addition, twenty-four spots of protein with 100% of homology and nine with over 80% were matched to ESTs (expressed sequence tags) after expanding the amino acid sequences of the protein spots by Database searches using the available EST databases of rice at the NCBI (http://www/ncbi.nlm.nih.gov/) and DDBJ (http://www.ddbj.nig.ac.jp/). Also, a total of 53 proteins out of 700 protein spots separated on the 2-DE gels were analyzed by the peptide mass fingerprinting method (MALDI-TOF/MS). High-quality mass spectra suitable for peptide mass fingerprinting were obtained from 41 spots. Using the ESI-Q-TOF/MS, however, we were able to identify 53 seed proteins of rice, including 12 proteins not registered in database. The rapid expansion of DNA sequence databases to the utilization of EST now provides the whole or partial gene sequences of model organisms, and the recent advances in protein micro-characterization by mass spectrometry allow the possibility of linking these DNA sequences to the proteins in functional complexes. Proteome Database of rice is updated, and is available on the World Wide Web at http://gene64.rda.affrc.go. This work shows that the proteome analysis could be a useful strategy to link the sequence information to the functional genomics.

We improved the separation of the basic proteins from the soybean cotyledon, Glycine max L. Merr. by searching N-terminal sequences data in proteins isolated by two-dimensional electrophoresis (2-DE). After removed Hexane, proteins were extracted from cotyledon with a urea/Triton/2-mercaptoetanol solution. Using this method, the highly reproducible isoelectric focusing (IEF) can formed with polyacrylamide gels with pH 4.0-9.8. The IEF tube gels were used as the first dimension, and proteins were visualized by second-dimensional gel electrophoresis, and identify a number of soybean cotyledon proteins using mass spectrometry in the proteome analysis. These instruments of 2-DE and IEF tube gels were used 27 cm and investigate under various conditions. The total number of spots and features was obtained by PDQuest software (Bio-Rad). In this experiments performed, the IEF tube gels and instruments afforded good reproducibility in the number of PDQuest-detected spots from gel to gel while IPG offered better reproducibility in the total number of manually detected spots from gel to gel. In conclusion, we have separated of the basic 13 proteins in soybean. The glycinin subunit separations are also considered to play important roles in soybean breeding and biochemical characterization. The improved technique will be useful to dissect the genetic control of glycinin expression in soybean.

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.

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.