玉米种质资源抗南方锈病鉴定

玉米南方锈病已成为近几年我国夏玉米生产区间歇性暴发流行的病害,对玉米生产构成严重威胁,病害流行年份可造成10%以上的产量损失。目前,已确认的抗病自交系非常有限,而抗病育种急需不同抗性控制背景的自交系。为发掘和丰富可利用的南方锈病抗源,于2008～2012年,在广西南宁采用田间人工接种方法对1589份玉米种质资源进行抗南方锈病鉴定。通过高病害压力和连续多年的鉴定,从1589份玉米种质中鉴定出高抗（HR）材料26份,占鉴定总数的1.64%;抗病（R）材料137份,占鉴定总数的8.62%;中抗（MR）水平的材料382份,占鉴定总数的24.04%;感病（S）材料489份,占鉴定总数的30.77%;高感（HS）材料555份,占鉴定总数的34.93%。总体上抗南方锈病种质较少,引进种质中抗病类型材料的比例略高。经重复鉴定,筛选出赤556等18份自交系、老来秕等3份地方品种、A69等4份来自津巴布韦的材料、引自CIMMYT的Dr11表现稳定高抗南方锈病,为今后我国玉米抗南方锈病育种提供了新的抗性资源。     

玉米抗腐霉茎腐病种质标记基因型鉴定与遗传多样性分析

腐霉茎腐病(Pythium stalk rot)是玉米生产上的重要病害。本研究利用14个与8个抗玉米茎腐病基因连锁的分子标记对196份抗腐霉茎腐病玉米种质进行抗病标记基因型鉴定,并采用42对多态性SSR标记对54份抗病自交系进行遗传多样性分析,以期阐明玉米抗腐霉茎腐病种质的标记基因型和遗传背景,并为资源的有效利用、新基因的挖掘和杂种优势模式确定提供参考信息。14个与抗病基因连锁的分子标记将196份抗性种质鉴定为128种标记基因型,表明存在多样的抗性基因组合方式。191份种质获得与齐319、X178或1145中一个或多个的相同的扩增,表明97.45%种质可能含有与3个抗玉米茎腐病材料相同的抗病基因;粤61、郑653、赤L136、白53和18--14共5份种质均未扩增出与齐319、X178和1145相同的标记基因型,可能携带其他抗茎腐病基因;遗传背景相近的抗性种质分属不同的标记基因型,表明抗病种质携带的抗病基因可能在育种选择中发生了分离。42对多态性SSR引物在54份抗病材料中共检测出119个等位基因(Na),多态位点百分率(PPB)为99.17%,平均有效等位基因数(Ne)为1.7070,平均Nei′s基因多样性(H)为0.3999,平均Shannon′s信息指数(I)为0.5844,平均多态信息含量(PIC)为0.5527,变幅为0.2061～0.7844;通过UPGMA聚类分析,54份抗病材料被划分为2个类群,共6个亚群中,分别是旅大红骨亚群、BSSS亚群、塘四平头亚群、PA亚群、PB亚群、Lan亚群,表现出较高的遗传多样性。结果表明,我国6个杂种优势群中均含有较为丰富的抗腐霉茎腐病种质资源,其中PA亚群包含的抗病种质最多。     

中国灌木辣椒种质遗传多样性的SRAP和SSR分析

应用SRAP和SSR分子标记对8份辣椒种质进行了遗传多样性分析,结果表明,15对SRAP引物组合共扩增出321条带,平均每对引物扩增出21.40条,多态性位点比率为72.90%;18对SSR引物共扩增出109条带,平均每对引物扩增出6.06条,多态性位点比率为98.17%。与SRAP比较,SSR检测到的Shannon多样性指数(I)、观测等位基因数(Na)和有效等位基因数(Ne)等遗传多样性参数都较大,说明SSR有更高的多态性检测效率。基于SRAP的聚类与基于SSR的聚类之间存在极显著正相关,且都能将中国灌木辣椒种质与美洲灌木辣椒种质及一年生辣椒种质有效区分。     

玉米种质资源对六种重要病虫害的抗性鉴定与评价

在2003-2005年间,对604份玉米种质进行了抗弯孢菌叶斑病和玉米螟鉴定,筛选出抗弯孢菌叶斑病的材料93份,抗玉米螟材料22份。2006-2009年间,对836份玉米种质进行了抗大斑病、茎腐病、穗腐病和瘤黑粉病的鉴定与评价,筛选出一批高抗和多抗的资源。在836份资源中,对大斑病1、2和N号3个生理小种具有抗性的材料均为50%左右;抗茎腐病材料为41.3%,高抗和抗性种质分别为264和81份;穗腐病高抗和抗性种质分别为5和171份,占比为21.1%;瘤黑粉病高抗和抗性种质各261和14份,占总鉴定材料的32.9%。上述结果表明抗大斑病、茎腐病和瘤黑粉病的种质资源较为丰富。通过对抗性结果进行对比分析,发现不同生态区玉米种质的抗性强弱以及抗性多样性存在明显差异,黑龙江和内蒙古的种质对病虫害的抗性强弱及多样性程度明显高于四川种质。此外,玉米自交系对病虫害的抗性强弱以及多抗性程度高于农家种。     

玉米种质资源抗灰斑病鉴定与评价

2001-2004年,于田间应用人工注射接种的方法对413份玉米自交系和59份玉米杂交种进行抗灰斑病(Gray leaf spot)鉴定,筛选出病级1级高抗(HR)自交系6份、3级抗病(R)自交系28份和杂交种7份.鉴定结果表明,在供试的不同玉米自交系及杂交种间的抗病性存在明显差异,而表现高抗的玉米自交系较少,没有发现高抗杂交种.加强玉米抗灰斑病种质资源的收集和评价,对玉米抗病育种非常必要.     

120份欧美玉米自交系的遗传多样性分析

为了拓宽黄淮海区玉米自交系的遗传基础,加快欧美优异种质的融入与利用,本研究利用SSR分子标记对120份来自美国和塞尔维亚及2份中国的玉米自交系进行遗传多样性和聚类分析。结果表明:29个多态性SSR标记共检测到115个等位位点,平均3.97个,位点多态性信息指数(PIC)平均为0.50,较好地揭示了自交系间的遗传多样性;观测杂合度(Ho)仅为0.03,表明参试自交系遗传稳定、纯合度高;美国SS、美国NSS、塞尔维亚和中国骨干自交系4个群之间相比,美国NSS群的等位位点数(3.55)、Shannon信息指数(0.93)最高,而塞尔维亚群的有效等位位点数(2.37)最高,表明美国NSS和塞尔维亚自交系群比其他两个群遗传多样性高;4个自交系群间的遗传距离介于0.1403~0.4695之间,美国NSS群与美国SS群、塞尔维亚群之间较小(0.1419,0.1403),与中国骨干自交系群之间最大(0.4695),4个群的遗传一致度介于0.6253~0.8691之间,美国NSS群与美国SS、塞尔维亚两个群之间的遗传一致度较高,表明美国与塞尔维亚自交系之间基因交流频繁,亲缘关系较近;聚类分析将122份玉米自交系分为9大主要类群,美国SS种质、NSS种质自交系被明显的区分开,并且SS种质被分为2个主要类群(Ⅰ和Ⅸ),NSS种质被分为6个主要类群(Ⅱ-Ⅶ),来自塞尔维亚的材料分散在美国NSS种质类群。本研究结果为来自欧美的自交系在玉米育种中合理利用提供可靠依据。     

玉米种质资源抗弯孢菌叶斑病特性研究

针对近年弯孢菌叶斑病日益严重的发生趋势,对1698份玉米种质(自交系、群体、杂交种以及特殊材料)进行了抗弯孢菌叶斑病鉴定.结果表明,中国玉米种质抗性较引进种质抗性好;不同省份所供种质抗性存在差异,北京、四川、广西种质总体抗性较好;在新选育的自交系中,鉴定出12份高抗材料;在当前培育的杂交种中,有22份高抗或抗弯孢菌叶斑病;玉米对弯孢菌叶斑病抗性在相同核基因、不同细胞质种质间无差异;玉米抗大斑病基因对抗弯孢菌叶斑病无效.     

玉米种质资源抗弯孢菌叶斑病特性研究

针对近年弯孢菌叶斑病日益严重的发生趋势,对1698份玉米种质(自交系、群体、杂交种以及特殊材料)进行了抗弯孢菌叶斑病鉴定。结果表明,中国玉米种质抗性较引进种质抗性好;不同省份所供种质抗性存在差异,北京、四川、广西种质总体抗性较好;在新选育的自交系中,鉴定出12份高抗材料;在当前培育的杂交种中,有22份高抗或抗弯孢菌叶斑病;玉米对弯孢菌叶斑病抗性在相同核基因、不同细胞质种质间无差异;玉米抗大斑病基因对抗弯孢菌叶斑病无效。     

玉米重要自交系的肿囊腐霉茎腐病抗性鉴定与评价

由肿囊腐霉菌(Pythium inflatum Matthews)引起的玉米茎腐病是影响玉米产量的一种重要病害。为进一步拓展可利用的抗源,于2010-2011年在田间采用人工接种方法对287份重要的玉米自交系种质进行了玉米茎腐病的抗性鉴定评价。结果表明,287份鉴定材料中有171份自交系对茎腐病的抗性达到中抗以上水平,占鉴定材料的59.58%,其中高抗自交系共43份,占鉴定材料总数的14.98%;感病类型自交系共116份,占鉴定材料的40.42%,其中高感自交系共95份,占鉴定材料总数的33.10%。Lancaster、Reid及P群种质中具有丰富的茎腐病抗源,而塘四平头种质群中茎腐病抗源相对缺乏,多为感病类型。该研究结果可为今后我国玉米茎腐病抗性种质的引进和改良提供重要参考。     

美国玉米自交系对4种病原茎腐病的抗性鉴定及遗传多样性分析

对外引玉米种质进行抗病鉴定是对其充分利用并选育抗病品种的基础和前提。本研究于2017-2018年连续2年采用人工接种技术评价了149个美国自交系对分别由禾谷镰孢(Fusarium graminearum)、拟轮枝镰孢(Fusarium verticillioides)、层出镰孢(Fusarium proliferatum)和芒孢腐霉(Pythium aristosporum)4种病原菌引起的茎腐病的抗性表现,并选择30个抗性较好的与6个骨干自交系进行遗传多样性分析。结果表明,149个美国自交系中,对禾谷镰孢、拟轮枝镰孢、层出镰孢和芒孢腐霉表现中抗及以上抗性的自交系分别有62个、44个、41个和54个,其中对4种茎腐病全部表现高抗的自交系有23个,全部表现中抗及以上抗性的自交系有32个,对3种镰孢菌茎腐病全部表现高抗的自交系有27个;所有供试材料中,88个自交系对4种茎腐病的抗性表现一致,61个自交系对4种茎腐病的抗性存在差异;共筛选出20条多态性引物,每个引物可检测出5～11个等位基因,平均等位变异数为7.7个,聚类分析将36个材料划分为6个类群,其中2FACC、J8608、黄早四分别被单独聚为一类,剩余自交系被划分为3个类群,分别包含自交系个数为26、5和2,第Ⅰ类群又分为3个亚群。本研究结果明确了外引美国自交系对不同病原菌引起的玉米茎腐病的抗性差异,为抗病育种中抗源的选择提供参考。     

广西玉米种质资源对纹枯病的抗性鉴定

在人工接种条件下,对860份玉米材料进行了纹枯病抗性鉴定和评价,旨在为进一步开展玉米纹枯病抗性育种和分子生物学研究奠定基础。结果显示,在鉴定的860份玉米材料中,没有发现免疫的材料,高抗、抗、中抗、感和高感的比例分别为3．49％、28．60％、26．16％、10．35％和31．40％;在农家种、群体种和杂交种（组合）等杂合体中,抗病材料所占比例较大,而自交系等纯合体中,感病材料所占比例较大,表明玉米杂合体种质资源材料中可能蕴藏着不同的抗纹枯病基因,特别是广西农家种中可能存在对纹枯病具有稳定抗性的材料,值得进一步研究和利用。     

广西玉米种质资源对纹枯病的抗性鉴定

在人工接种条件下,对860份玉米材料进行了纹枯病抗性鉴定和评价,旨在为进一步开展玉米纹枯病抗性育种和分子生物学研究奠定基础。结果显示,在鉴定的860份玉米材料中,没有发现免疫的材料,高抗、抗、中抗、感和高感的比例分别为3.49%、28.60%、26.16%、10.35%和31.40%;在农家种、群体种和杂交种（组合）等杂合体中,抗病材料所占比例较大,而自交系等纯合体中,感病材料所占比例较大,表明玉米杂合体种质资源材料中可能蕴藏着不同的抗纹枯病基因,特别是广西农家种中可能存在对纹枯病具有稳定抗性的材料,值得进一步研究和利用。     

玉米种质资源抗矮花叶病鉴定

采用摩擦接种方法,鉴定了3995份玉米种质对玉米矮花叶病毒(SCMV-MDB)的抗病性。经重复鉴定,筛选出抗病优良自交系73份,抗病丰产杂交种80份。玉米不同类群种质,对SCMV-MDB的抗病性有明显差异,改良Reid、Lancaster、旅大红骨类群种质大部分表现感病;塘四平头、外杂先锋选系类群种质大多数表现抗病。在不同类型种质中,硬粒型、马齿型和半马齿型表现抗病的较多,糯质型较少,甜质型和爆裂型中尚未发现抗源。     

Recovery of exotic alleles in semiexotic maize inbreds derived from crosses between Latin American accessions and a temperate line

Genetic diversity of elite maize germplasm in the United States is narrow relative to the species worldwide. Tropical maize represents the most diverse source of germplasm. To incorporate germplasm from tropical maize landraces into the temperate gene pool, 23 Latin American maize accessions were crossed to temperate inbred line Mo44. During inbred line development, selection was practiced in temperate environments, potentially resulting in the loss of substantial proportions of tropical alleles. Genotyping 161 semiexotic inbreds at 51 simple sequence repeat (SSR) loci permitted the classification of their alleles as either Mo44 or tropical and allowed estimation of the proportion of detectable tropical alleles retained in these lines. On average, the percentage of detectable tropical alleles ranged among lines from 15% to 56%, with a mean of 31%. These are conservative, lower-bound estimates of the proportion of tropical germplasm within lines, because it is not known how frequently Mo44 and the tropical maize accession parental populations shared SSR alleles. These results suggest that substantial proportions of exotic germplasm were recovered in the semiexotic lines, despite their selection in temperate environments. The percent of tropical germplasm in semiexotic lines was not correlated to grain yield or moisture of lines testcrossed to a Corn Belt Dent tester, indicating that the incorporation of a substantial percentage of tropical germplasm in an inbred line does not necessarily negatively impact its combining ability. Thus, tropical maize accessions represent a good source of exotic germplasm to broaden the genetic base of temperate maize without hindering agronomic performance.     

Genetic characterization of a core set of a tropical maize race Tuxpeño for further use in maize improvement

The tropical maize race Tuxpe?o is a well-known race of Mexican dent germplasm which has greatly contributed to the development of tropical and subtropical maize gene pools. In order to investigate how it could be exploited in future maize improvement, a panel of maize germplasm accessions was assembled and characterized using genome-wide Single Nucleotide Polymorphism (SNP) markers. This panel included 321 core accessions of Tuxpe?o race from the International Maize and Wheat Improvement Center (CIMMYT) germplasm bank collection, 94 CIMMYT maize lines (CMLs) and 54 U.S. Germplasm Enhancement of Maize (GEM) lines. The panel also included other diverse sources of reference germplasm: 14 U.S. maize landrace accessions, 4 temperate inbred lines from the U.S. and China, and 11 CIMMYT populations (a total of 498 entries with 795 plants). Clustering analyses (CA) based on Modified Rogers Distance (MRD) clearly partitioned all 498 entries into their corresponding groups. No sub clusters were observed within the Tuxpe?o core set. Various breeding strategies for using the Tuxpe?o core set, based on grouping of the studied germplasm and genetic distance among them, were discussed. In order to facilitate sampling diversity within the Tuxpe?o core, a minicore subset of 64 Tuxpe?o accessions (20% of its usual size) representing the diversity of the core set was developed, using an approach combining phenotypic and molecular data. Untapped diversity represents further use of the Tuxpe?o landrace for maize improvement through the core and/or minicore subset available to the maize community.     

A USA–Africa collaborative strategy for identifying, characterizing, and developing maize germplasm with resistance to aflatoxin contamination

Aflatoxin contamination of maize by Aspergillus flavus poses serious potential economic losses in the US and health hazards to humans, particularly in West Africa. The Southern Regional Research Center of the United States Department of Agriculture, Agricultural Research Service (USDA-ARS-SRRC) and the International Institute of Tropical Agriculture (IITA) initiated a collaborative breeding project to develop maize germplasm with resistance to aflatoxin accumulation. Resistant genotypes from the US and selected inbred lines from IITA were used to generate backcrosses with 75% US germplasm and F₁ crosses with 50% IITA and 50% US germplasm. A total of 65 S₄ lines were developed from the backcross populations and 144 S₄ lines were derived from the F₁ crosses. These lines were separated into groups and screened in SRRC laboratory using a kernel-screening assay. Significant differences in aflatoxin production were detected among the lines within each group. Several promising S₄ lines with aflatoxin values significantly lower than their respective US resistant recurrent parent or their elite tropical inbred parent were selected for resistance-confirmation tests. We found pairs of S₄ lines with 75–94% common genetic backgrounds differing significantly in aflatoxin accumulation. These pairs of lines are currently being used for proteome analysis to identify resistance-associated proteins and the corresponding genes underlying resistance to aflatoxin accumulation. Following confirmation tests in the laboratory, lines with consistently low aflatoxin levels will be inoculated with A. flavus in the field in Nigeria to identify lines resistant to strains specific to both US and West Africa. Maize inbred lines with desirable agronomic traits and low levels of aflatoxin in the field would be released as sources of genes for resistance to aflatoxin production.