Adaptation of tropical maize germplasm to temperate environments

Maize (Zea mays L.) is one of few crops that can offer significant genetic gains with the utilization of genetic diversity. Genetically broad-based germplasm has the potential to contribute useful and unique alleles to U.S. Corn Belt breeding programs not present in current U.S. genome sequences (e.g. B73, NAM, etc.). Our objectives were to determine if unique tropical genetic materials have been effectively adapted to temperate environments and how their agronomic performance was relative to adapted populations. An important long-term objective of the Iowa and North Dakota maize breeding programs has been, in addition to the typical elite by elite line pedigree selection cultivar development process, to adapt exotic and unique germplasm, maximize their genetic improvement, and develop unique products for breeding and commercial uses. Stratified mass selection methodology for earliness has been utilized for the adaptation of tropical and temperate populations to Iowa and North Dakota environments. This method has allowed screening of up to 25,000 genotypes per population cycle at a rate of one cycle per year. In addition, the estimated cost per year our programs had for the adaptation of each population was less than $2,000 which could successfully be applied in any breeding program across the globe. This cost has been less than 1 % of the total cost for finding minor genes on the same trait. Our results showed the successful adaptation of exotic populations was independent from genetic background. We can speculate there are a few major genes responsible for most of flowering date expression. We encourage the use of technology to target traits according to their genetic complexity. Stratified mass selection at the phenotypic level has been successful. Each of the populations with either 25 of 100 % tropical germplasm are available for anyone who may desire to expand the germplasm base of their breeding programs with tropical germplasm adapted to temperate mid- and short-season U.S. Corn Belt environments.     

柱花草种质抗旱性综合评价

对我国目前主要推广种和部分引进的柱花草种质进行抗旱性综合评价。采用完全随机区组设计,4梯度人工控水干旱,测试其各项形态指标和生理指标,选出与水分胁迫达极显著相关的8项指标,用隶属函数值法,对44份柱花草种质的抗旱性综合评价。与抗旱性成正相关的指标为：相对生物量、相对株高、叶片抗旱级别、相对qP、相对脯氨酸含量、相对Fv/Fm、相对Fv’/Fm’;负相关的有：相对电导率。抗旱性综合评价显示,抗旱性最强的依次为：热研5号、USTPRC90139、爱德华①、爱德华②和CIAT11369;最弱的依次为：CPI18750A、TPRC90037②、TPRC90037③和TPRC90028。聚类分析将44份柱花草种质抗旱性可分为3类：高抗旱性10份、中抗旱性15份、低抗旱性19份。本研究为筛选柱花草优良种质和育种材料提供了理论和实践的科学数据。     

Introgression of temperate germplasm to improve an elite tropical maize population

The effect of introgression of temperate germplasm into an elite tropical maize population, EV8443SR, was studied for different traits. Two temperate lines, FS14 and DEA, were crossed with EV8443SR. The F1 of each cross was backcrossed to EV8443SR to produce the BC1. F1 and BC1 were subjected to two cycles of random mating. Random sets of S1 families were derived from the tropical-temperate populations and the tropical parent for evaluation in two tropical locations. Introgression of FS14 and DEA into EV8443SR significantly increased earliness, and reduced plant height, number of grains per ear, 1000 grains weight and grain yield. Significant harvest index increases were observed. The effect of introgression on genetic variance of EV8443SR varied with trait and sometimes with cross and location. The highest expected genetic progress was obtained in a tropical-temperate population for most of the traits studied. EV8443SR appeared better than, or pratically equal to, the tropical-temperate populations as a foundation population to improve grain yield and husk cover. This revised version was published online in July 2006 with corrections to the Cover Date.     

Heterosis and combining ability of seven maize germplasm populations

Understanding the combining ability and heterosis of available germplasm is a prerequisite for successful maize improvement and breeding. The objectives of this study were to analyze the combining ability and heterosis of seven representative maize germplasm populations, and further, to evaluate their potential utility in germplasm improvement. A total of 21 crosses were made among these seven populations in a complete diallel without reciprocals. The parental populations and 21 crosses were evaluated for days to silking (DS), ear height (EH), and grain yield (GY) in the Northeast and Yellow and Huai River maize growing areas in China in 2012. Csyn5, Csyn7, Cpop.11, and Cpop.12 had desirable general combining ability (GCA) effects for DS and EH in both the Northeast China mega-environment (NCM) and the Yellow and Huai River Regions of China mega-environment (YHCM). Cpop.11 possessed a favorable GCA effect for GY in the NCM, as did Csyn5, Cpop.17, and Cpop.18 in the YHCM. Csyn6 and Csyn7 exhibited tremendous yield-enhancing potential in both mega-environments. Additionally, six combinations including Csyn7 × Csyn6, Csyn5 × Csyn6, Cpop.11 × Cpop.18, Cpop.12 × Cpop.17, Csyn7 × Cpop.17, and Csyn5 × Csyn7 exhibited better specific combining ability effects for GY, yield performance, and mid-parent heterosis in the appropriate mega-environment. These results indicated that the seven populations would be very useful for the improvement of related agronomic traits, and the six candidate combinations possessed great potential for further improvement and utilization.     

玉米耐低温种质资源的初步鉴定和筛选

摘要：本试验对654份玉米自交系的耐低温特性进行了鉴定,在常温（25℃）和低温（10℃）胁迫下分别测定种子的发芽率以及低温胁迫下的发芽时间。以相对发芽率和平均发芽时间作为耐低温特性评价指标,通过聚类分析筛选到30份强耐低温自交系和43份对低温胁迫强敏感自交系,为培育耐低温玉米新品种和挖掘耐低温相关基因提供种质资源。     

Breeding potential of U.S. maize germplasm for utilization in Chinese temperate conditions

U.S. maize germplasm has been considered as a new alternative source of favorable alleles to broaden the narrowing genetic base of temperate germplasm. However, direct utilization of diverse U.S. germplasm in target mega-environments could be hampered by limited adaptation-related information on parental performance or heterotic response in crosses with local germplasm. The objective of this study was to measure the performance of U.S. maize populations for broadening the Chinese germplasm base. Fifteen diverse U.S. populations were testcrossed to three local tester lines, representing Chinese heterotic groups A, B, and D, to evaluate parental adaptation and combining abilities for days to silking (DS), ear height (EH), and grain yield (GY) in target and intermediate mega-environments in northern China. There was genetic variability among U.S. maize populations for additive and non-additive effects for DS and GY, and predominant additive genetic effects for EH. All 15 U.S. populations, except for BS27 and BS31 due to slightly high EH, could be directly used in target mega-environments similar to the U.S. Corn Belt. U.S. populations BS11(HI)C7, BS13(S)C7, BS17(CB)C4, BS31, BSCB1(R)C12, and BSBB(SRCB)C4 had better effects for increasing GY. Favorable effects for DS were also observed in BS11(HI)C5 and BS31, for DS and EH in BS13(S)C7 and BSCB1(R)C12, and for EH in BSBB(SRCB)C4. The best strategies for utilizing these germplasms may be to introgress BS13(S)C7 and BS17(CB)C4 into group A, BS11(HI)C5 into group B, and BSCB1(R)C12 and BSBB(SRCB)C4 into group D to increase genetic variation within Chinese heterotic pools.     

大豆出苗期耐盐性鉴定方法建立及耐盐种质筛选

土壤盐渍化是影响农业生产的重要问题,筛选耐盐大豆资源对于大豆主产区盐渍化土壤的利用具有重要意义。以中黄35、中黄39、Williams82、铁丰8号、Peking和NY27-38为供试材料,以蛭石为培养基质,设0、100和150 mmol L?1 NaCl 3个处理,进行出苗期耐盐性鉴定,分析与生长相关的6个指标,旨在明确大豆出苗期耐盐性鉴定指标和评价方法。结果表明, 150 mmol L?1NaCl处理显著降低大豆的成苗率、株高、地上部鲜重、根鲜重、地上部干重和根干重,并且不同材料间差异显著。基于幼苗生长发育状况的耐盐指数方法与耐盐系数方法对6份种质耐盐性评价结果显著相关。耐盐指数法对植株无损坏、可省略种植对照,节约人力和物力,提高种质鉴定的效率。因此,以150 mmol L?1 NaCl作为出苗期耐盐鉴定浓度,以耐盐指数作为大豆出苗期耐盐鉴定评价指标,鉴定27份大豆资源,获得出苗期高度耐盐大豆(1级) 3份、耐盐大豆(2级) 7份,其中4份苗期也高度耐盐(1级),分别为运豆101、郑1311、皖宿1015和铁丰8号。本研究建立了一种以蛭石为基质,利用150 mmol L?1 NaC...     

玉米种质资源主要品质性状鉴定与评价

对2003—2004年收集、整理的400份玉米种质资源的主要品质性状进行了鉴定评价。结果表明，不同类型的玉米种质资源中地方品种的粗脂肪、粗淀粉性状和自交系粗蛋白、赖氨酸性状具有更大的遗传多样性。通过鉴定，筛选出一批品质性状优异的玉米种质资源．并对现行玉米种质资源品质的评价标准进行了讨论。     

绿豆种质资源苗期耐盐性鉴定及耐盐种质筛选

土壤盐渍化已成为影响中国农业生产的重要问题,筛选耐盐绿豆种质资源对于盐渍化土地利用具有重要意义。本研究对346份国内外绿豆种质苗期用150 mmol L–1 NaCl进行胁迫处理,测定了株高、地上部鲜重、根鲜重、地上部干重、根干重、根长、根体积等12个指标,采用主成分分析和隶属函数分析、耐盐性综合评价分析及聚类分析对各样本的耐盐性进行了综合评价和归类,并采用逐步回归分析建立了耐盐性预测回归方程。结果表明,处理组与对照组各性状评价指标存在极显著差异,且12个指标的耐盐系数间均存在着不同程度的相关性。结合盐害症状等级划分与耐盐性综合评价结果,筛选到苗期高耐盐(1级)绿豆26份,耐盐(3级)绿豆65份,对盐分敏感(7级)绿豆74份,对盐分极敏感(9级)绿豆18份。其中来自江西的C04125、菲律宾的C06310等10份耐盐能力最强,可作为绿豆耐盐育种的优异种质资源。地上部鲜重、根鲜重、根干重、根长、根体积和根分枝数可以作为绿豆苗期耐盐性评价指标。     

玉米热带亚热带种质资源在温带利用中出现的问题与对策

近年来在育种工作中处于种质扩增的需要,很多育种单位引进热带亚热带种质资源进行群体改良和杂交、回交选择,培育出了一批遗传基础丰富的优良自交系,并以这些自交系配制了一批优良杂交种推广应用于生产实践.但在利用热带亚热带玉米种质资源过程中也存在很多问题,本文就这些问题和解决对策作初步阐明.     

Genetic location and evaluation of chromosomal segments for drought tolerance at flowering stage in maize using selected backcross populations

Development and evaluation of introgression lines have become one of the promising approaches to understanding genetic mechanisms of important traits in crops. In this study, three sets of drought tolerance (DT) selected backcross populations in maize, including two BC₂S₁ populations and one BC₃S₁ population, from a cross of Qi319 and Huangzaosi (recurrent parent) were developed by selecting for short anthesis-silking interval (ASI) under the condition of serious water stress at flowering stage. The introgression of chromosome segments was identified using microsatellite markers. The results showed that the marker allele introgression frequencies in the three DT populations significantly increased compared with the expected value under no selection. There was a notable increase of introgression frequency for the most of these markers which were located on all chromosomes except chromosome 8, but most concentrated on some chromosomes, especially on chromosomes 4 and 5. For example, chromosome 4 harboured the largest number of introgression regions, on which five segments were detected. The ASI in the DT populations significantly shortened compared with the initial BC₂ population.     

Development of highly sprouting tolerant wheat germplasm with reduced germination at low temperature

The development of sprouting tolerant spring and winter wheat varieties that retain dormancy in cool, wet conditions is a long-term objective in Hokkaido, Japan. A highly tolerant spring dwarf line, “OS21-5”, derived from “Tordo” × “Zenkoji”, was used to develop transgressive spring, “OS38” and “OS74”; and winter, “OW77”, “OW104” and “OW93” wheats. More recently, winter lines with improved agronomic performance, though still deficient in quality and scab resistance, have been identified. In general, germination percentage of mature grain at 10 ^°C was closely related to the mean temperature experienced during the 5 days prior to maturity (dough–yellow ripening stage) and to the capacity to maintain a high amylograph paste viscosity. Dormancy at 10 ^°C appeared to be determined by a combination of genotype and variation in sensitivity to temperature during the later stages of ripening. Genotypes such as “OS38” and ‘OWl04’ were both highly tolerant to germination at 10 ^°C and insensitive to temperature during ripening. By comparison, most of the other cultivars showed a similar, intermediate sensitivity to ripening temperature, and dormancy decreased as ripening temperature increased. Dormancy of‘RL4137’ at maturity, and to a lesser extent ‘Gifukomugi’ and ‘KKI354’, was very sensitive to ripening temperature and useful levels of dormancy only developed under cool ripening temperatures, mean temperature < 18–20 ^°C.     

Assessment of drought tolerance among Algerian maize populations from oases of the Saharan

Maize (Zea mays L.) is severely affected by drought and this challenge is expected to worsen with climate change. One of the most promising solutions is breeding for drought tolerance that requires the identification of sources of drought tolerance. Eighteen maize populations from the Algerian Sahara were evaluated along with three European and two American checks in two Algerian locations under drought and control conditions. Under drought conditions, Algerian populations had large variability for most traits and the populations BTM and LOM out yielded most checks. The ratio yield under drought/yield under control conditions was 65.90, 65.33, and 53.23% for BTM, TAO and LOM, respectively. These populations maintained also yield components such as grain weight, ear length, number of kernel rows, ears per plant, and leaf area under stress conditions; furthermore, they have reduced leaf rolling. TAO and BTM presented the highest relative water content, and LOM had the highest proline content. Algerian populations can be considered as a novel source of favorable alleles for drought tolerance and show a wide variety of mechanisms of response to drought.     

Breeding potential of maize germplasm populations to improve yield and predominant heterotic pattern in Northeast China

Increasing the frequency of favorable alleles in elite germplasm is necessary for germplasm improvement and innovation in maize (Zea mays L.) breeding programs. Jidan27 (Si287 × Si144), an elite commercial single cross hybrid that represents the predominant heterotic pattern Chinese Sipingtou × Stiff Stalk Synthetic, has been widely cultivated in the Northeast China Corn Belt. However, the use of the hybrid Jidan27 has been hampered gradually due to its low yield potential, lack of resistance to lodging, and considerable incidence of head smut disease. Previous studies have evaluated yield potential of exotic populations, but few have considered using these germplasms as donors with favorable alleles to overcome these deficiencies in the hybrid Jidan27. In the present study, 12 exotic populations from CIMMYT and the U.S. and three semi-exotic populations were investigated as sources of favorable alleles to increase yield and lodging resistance, and reducing head smut susceptibility of the hybrid Jidan27. The performance of a set of 30 inbred × populations crosses, the hybrid Jidan27, and the two parental inbred lines Si287 and Si144 was evaluated in three locations for 2 years. Two populations, BS10(FR)C10 and Pop43, were identified as the best donors of favorable alleles lacking in the hybrid for improving the target traits. Further, BS13(S)C7 and Cpop.16 were also found to be better choices for improving grain yield and head smut resistance of the hybrid. These results suggest that the elite exotic germplasms evaluated here could provide useful genetic variability to improve other Chinese Sipingtou × Stiff Stalk Synthetic crosses related to Si287 × Si144 that are widely grown in Northeast China.     

突破玉米"种质瓶颈"加快新优势群的开发

玉米种质基础狭窄,即玉米育种界所说的“种质瓶颈”现象已经成为我国玉米生产可持续发展的首要限制因素。要解决我国玉米种质基础的脆弱性,使玉米产量尽快有所突破,必须开发利用新的种质资源。1突破“种质瓶颈”的紧迫性自从自交系间杂交种利用以来,典型的杂种优势模式就是来自于不同玉米带种质的杂交,在这种模式下,国内几十年来所形成的杂种优势群不外乎本土的四平头、旅大红骨,外引的Reid、Lancaster等有限几个。其他系统很少应用。有限的种质,相对我国复杂的玉米生态环境,多层次的生产和商业需求而言,便显得过于狭窄了。要突破这种“瓶…     

Testcross performance of maize lines from backcross populations containing highland Mexican or highland Peruvian germplasm

Summary Backcross populations of maize (Zea mays L.) were produced by crossing the early maturing inbred line W153R with the highland Mexican race Cónico then backcrossing to W153R (Q1 population) and by crossing W153R with the highland Peruvian race San Gerónimo then backcrossing to W153R (Q3 population). The populations were recombined by one generation of random mating. Testcrosses were produced from S₀ plants in the original and recombined versions and these were evaluated in New Zealand for grain yield, grain moisture and other traits.Unexpected changes occurred during recombination for increased grain yield in the Q1 population and for decreased grain moisture in the Q3 population. This indicates strong, unplanned selection. Many testcrosses were higher yielding than check hybrids of W153R, but most were later maturing.S₁ lines selected for high grain yield and acceptable grain moisture in testcrosses were advanced to the S₂ generation and re-tested. All produced testcrosses with lower grain moisture than late maturing hybrid checks. Testcross grain yields of one Q1 line were equivalent to those of late maturing checks and its testcross had a lower grain moisture. The high yield potential of hybrids of this line was confirmed in the S₄ generation.