Combining Ability Analysis on Yield Traits of Recombinant Inbred Lines in Hybrid Rice

A population of 140 recombinant inbred lines at F8 generation were obtained after seven successive generations of self-pollination using single seed descent（SSD） method from the F2 hybrids of three-line restorers Luhui 8258 with high combining ability and Yanghui 34. Then, the 140 inbred lines obtained above and their parents Luhui 8258 and Yanghui 34 were crossed with three different types of cyto-plasmic male sterile（CMS） lines（Gang 46 A, Ⅱ-32 A and Lu 98A） according to NCⅡ design. The resulting 426 combinations were planted at Deyang and Suining bases to test the combining ability and inheritance of five yield traits： yield per plant, panicle number per plant, filled grain number per panicle, seed setting rate and 1 000-grain weight. The results showed that the variances of both general and specific combining abilities of the five traits all reached a significant or extremely significant level at the two sites. The broad and narrow heritability of the yield traits（except 1 000-grain weight whose broad and narrow heritability were both over70%） were all below 50% at the two experimental bases, suggesting that the four traits were easily subjected to environment influence. Very significant positive correlation of general combining ability was found between yield per plant and other traits except 1 000-grain weight. The general combining ability variance showed a normal distribution among the recombinant inbred lines at two sites, right in line with inheritance of quantitative traits. So, the genes controlling rice general combining ability can be targeted by QTL mapping.

Mapping of QTLs for Sheath Blight Resistance Using Recombinant Inbred Lines of Rice(Oryza sativa L.)

A recombinant inbred line （RIL） population composed of 157 lines derived from an inter-subspecific hybrid of Daguandao/IR28 by the single seed descent method was used as materials, and the quantitative trait loci （QTLs） coffering the resistance to sheath blight in the 157 RILs and the parents were detected using the toothpick inoculation method. The disease indexes of rice sheath blight in the two parents and 157 RILs were scored and the QTLs responsible for rice sheath blight resistance were detected accordingly by QTL Cartographer software. The results showed that a total of 4 QTLs （qsbl, qsb2, qsb5-1, qsb5-2） conferring sheath blight resistance were detected on chromosomes 1, 2 and 5, and their variance explained ranged from 10.41% to 36.92%. The additive effect of qsb5-1 was negative, indicat- ing that the QTLs derived from donor parent IR 28 could enhance the resistance to sheath blight. However, the additive effects of qsbl, qsb2 and qsb5-2 were positive, indicating that the QTLs derived from donor parent Daguandao weakened the resis- tance to sheath blight.

Genetic analysis and QTL mapping of stalk cell wall components and digestibility in maize recombinant inbred lines from B73 × By804

The cell wall composition and structure of the maize stalk directly affects its digestibility and in turn its feed value.Previous studies of stem quality have focused mostly on common maize germplasm,and few studies have focused on high-oil cultivars with high grain and straw quality.Investigation of the genetic basis of cell wall composition and digestibility of maize stalk using high-oil maize is desirable for improving maize forage quality.In the present study,a high-oil inbred line(By804)was crossed as male parent with the maize inbred line B73 to construct a population of 188 recombinant inbred lines(RILs).The phenotypes of six cell-wall-related traits were recorded,and QTL analysis was performed with a genetic map constructed with SNP markers.All traits were significantly correlated with one another and showed high broad-sense heritability.Of 20 QTLs mapped,the QTL associated with each trait explained 10.0%–41.1%of phenotypic variation.Approximately half of the QTL each explained over 10%of the phenotypic variation.These results provide a theoretical basis for improving maize forage quality by marker-assisted selection.

Low-Temperature Response to Major Agronomic Traits by Using Recombinant Inbred Line(RIL) Populations Derived from Towada × Kunmingxiaobaigu

Development of the recombinant inbred line populations （RILs） is important basis to detect QTLs for cold tolerance at booting stage in rice. A set of 230 RILs derived from the cross of Towada and Kunmingxiaobaigu were used for evaluation of low-temperature response on major agronomic traits of plant height （PH）, panicle length （PL）, panicle exsertion （PE）, spikelet fertility （SF）, specific spikelet fertility （SSF）, and spikelets per panicle （SPP） under natural low-temperature growing environments in Yunnan Province, China. The results showed PH, PE, and SPP were mainly attributed by genotypes. PL was mainly influenced interactively by the genotypes × environments. SF and SSF were mainly controlled by the environments. Under the five different growth environments, F values of the six agronomic traits mentioned above ranged from 4.019 to 97.284. Significant difference was revealed between the lines. Under every environment, it indicated significantly positive correlation between SF and SSF, with correlation coefficients ranged from 0.826 to 0.885. It indicated significantly positive correlation between PH, PL, and PE. Under five different growing environments, variation coefficients of the six characters ordered in SSF （66.3%） 〉 PE （57.4%） 〉 SP （37.2%） 〉 SPP （16.2%） 〉 PH （9.6%） 〉 PL （6.4%）. SSF, PE and SF were most sensitive to low temperature stress at booting stage, while SPP, PH and PL being least. The RILs of Towada/ Kunmingxiaobaigu can be used as a genetic population to investigate cold tolerance at booting stage. SSF, PE and SF are most sensitive to cold tolerance at booting stage in rice. So far the the variation of PH, PL, and SPP related to cold tolerance are not clear under natural low-temperature environment. More tested environments and years are required to identify and evaluate cold tolerance at booting stage in rice.

Identification of QTLs for Blast, Bacterial Blight, and Planthopper Resistance Using SNP-Based Linkage Maps from Two Recombinant Inbred Rice Lines

Rice is the most significant global food security. Several biotic factors limit rice production, breeding biotic-resistant rice has, therefore, become an increasingly important goal. Two elite rice lines, IR71033-121-15 (IR71033) and IR57514-PMI-5-B-1-2 (IR57514), provide potential genes for biotic stress resistance traits. In this study, genotyping by sequencing (GBS) for single nucleotide polymorphism (SNP)-based linkage map construction was used to detect quantitative trait loci (QTLs) for blast (BL), bacterial blight (BB), whitebacked planthopper (WBPH), and brown planthopper (BPH) resistance. IR71033 was derived from Oryza minuta and carried BL, BB, WBPH, and BPH resistance QTLs. IR57514 is a well-adapted rainfed lowland line that carries BL and BB resistance QTLs. Two sets of recombinant inbred line (RIL) populations derived from crosses of KDML105 × IR71033 and KDML105 × IR57514 were used to dissect the genetic basis of disease and insect pest resistance. The RIL populations were evaluated for BL, BB, WBPH, and BPH resistance from 2016 to 2018 at four rice research centers in Thailand. From these, we identified a large number of SNPs through GBS and constructed high-resolution linkage maps. By combining phenotypic evaluation with the GBS data, a total of 24 QTLs on four chromosomes were detected that confered pest resistance and explained 7.3% - 61.4% of the phenotypic variance. These findings should facilitate identifying novel resistance genes and applying marker-assisted selection for resistance to the four major rice pests investigated here. These strategies will improve the resilience and reliability of rice varieties adapted to the low-yielding environment of rainfed lowland areas worldwide.

Genetic analysis and QTL mapping of growth period traits and plant height traits in soybean recombinant inbred lines from Dongnong 47 × PI 317334-B

High and stable yield is the main goal of soybean genetic improvement.In this study,association analysis was used to detect the quantitative trait loci(QTL)for the plant height,and soybean growth period using 182 SSR markers in the RIL population of 136 F_(4:8) lines,which developed from a cross between photoperiod-insensitive cultivar‘Dongnong 47’and photoperiod-sensitive variety PI317334–B.The results showed that 33 QTLs related to soybean growth period and plant height traits were detected by compound interval mapping,and were located on 12 linkage groups including N,C1,C2,J,D1a,B2,E,G,A2,O,L,I,with the contribution rate of 7.85–33.84%.These QTL loci and linkage markers related to soybean photoperiod sensitivity,would be helpful to identify key genes that control soybean photoperiod sensitivity,and provide an important basis for the breeding of new photoperiod-insensitive soybean varieties based on molecular design breeding.

Identification of Stable Quantitative Trait Loci for Sheath Blight Resistance Using Recombinant Inbred Line

To identify stable quantitative trait loci(QTLs)responsible for sheath blight resistance,a recombinant inbred line mapping population consisting of 219 lines was developed by crossing Lemont and Yangdao 4.Average disease rating,average lesion length,maximum disease rating and maximum lesion length were assayed in six different environments.A total of 128 minor effect QTLs were detected by multiple interval mapping.These QTLs explained less than 11.2%of the phenotypic variations individually,and 106 QTLs were clustered in 20 QTL-rich regions/putative loci.Significant QTL×environment interactions were detected at three putative loci(qSBR11.1,qSBR11.2 and qSBR11.3),indicating that these three loci were not stable.The other 17 stable loci(qSBR1.1,qSBR1.2,qSBR2.1,qSBR2.3,qSBR3.1,qSBR3.2,qSBR3.5,qSBR3.6,qSBR5.1,qSBR7.1,qSBR8.1,qSBR9.1,qSBR9.2,qSBR9.3,qSBR12.1,qSBR12.2 and qSBR12.4)provided a foundation for marker-assisted selection in breeding.Analysis of allelic effect on the 20 putative loci identified 7 highly stable loci,including qSBR3.2,qSBR7.1,qSBR8.1,qSBR9.2,qSBR9.3,qSBR12.1 and qSBR12.2.

Diversity, Structure, and Marker-Trait Association Analysis of the Maize Recombinant Inbred Line Population

Association mapping has emerged as a new tool to elucidate complex quantitative trait loci in maize, but there are few reports about systematic association analysis for the specific SSR markers with agronomic traits of interest in China. We investigated the morphological and genetic diversity and population structure for 76 maize recombinant inbred lines, and then association analysis were further performed between 48 simple sequence repeat loci and 17 morphological traits, consisting of nine ear-related traits and eight other traits. The 48 SSR markers were screened out and further classified into two groups including a group of loci in regions harboring reported quantitative trait loci that affect ear shape and a group of markers distributing on the whole genome randomly. The result indicated that the population of recombinant inbred lines was structured, showing five subpopulations. Our association results revealed that there were 82, 59, and 40 significant associations detected by K-test, logistic regression, and both analysis, respectively. When the 17 traits were considered separately, the significant associations between Q-SSRs and E-traits were raised to 27.8%, whereas the other groups of combinations ranged between 2.3 and 6.3%. As the proportion of significant associations is higher among the Q-SSR subset of markers and the subset of traits related to ear shape than those for all of the other combinations, we conclude that this approach is valid for establishing true positive marker-trait relationships. Our results also demonstrated that association mapping could complement and enhance previous QTL information for marker-assisted selection.

Identifying Genomic Regions Conferring Morphological and Yield-related Traits in Soybean Based On A Four-way Recombinant Inbred Line Population

Improvement of seed yield of soybean(Glycine max(L.)Merr.)is generally achieved by combining morphological and yield-related traits,such as plant height(PH),node number on main stem(NN),pod number per plant(NP),seed number per plant(NS),100-seed weight(HSW)and seed weight per plant(SWPP).Identifying quantitative trait loci(QTLs)for morphological and yield-related traits is therefore important for breeding.In this study,a four-way recombinant inbred line population comprising 160 lines derived from the cross(Kenfeng14×Kenfeng15)×(Heinong48×Kenfeng19)was planted in five different environments and morphological and yield-related trait data were used to identify QTLs by the inclusive composite interval mapping method.Totally 38 QTLs for PH,40 QTLs for NN,26 QTLs for NP,10 QTLs for NS,26 QTLs for HSW and 49 QTLs for SWPP were detected in 125 genomic regions.Single QTLs explained 2.17%-14.60%,2.00%-10.04%,2.37%-9.77%,2.62%-8.61%,0.47%-6.51%and 0.14%-12.39%of the phenotypic variation for PH,NN,NP,NS,HSW and SWPP,respectively.Among these 125 genomic regions,120 were newly associated with morphological and yield-related traits.The results would facilitate the molecular breeding of morphological and yield-related traits in soybean.

QTL mapping of grain appearance quality traits and grain weight using a recombinant inbred population in rice(Oryza sativa L.)

supported by a grant from the National High-Tech R＆D Program of China （2014AA10A603, 2014AA10A604）;a grant from the Youth Foundation in Sichuan, China （2011JTD0022）;the special fund for China Agricultural Research System （CARS-01-08）;the Provincial Specialized Funds for Innovation Ability Promotion in Sichuan, China （2013GXJS005）

甘蓝型油菜RIL群体苗期根系耐铝性鉴定及评价方法研究

为减少铵肥的大量施用以及酸雨频降引发的耕地酸化,从而影响作物的生长,利用综合评价方法通过幼苗期根系表型筛选耐铝种质.以甘蓝型油菜重组自交系(RIL)亲本10D130和中双11为材料筛选苗期适宜的铝胁迫浓度,使用该浓度处理RIL内138个品种(系)幼苗,对其根长、根表面积、根平均直径、根体积、根交叉数、根尖数和根干质量7个根系指标的铝毒单项耐性系数进行变异系数分析、相关性分析、主成分分析、系统聚类分析和逐步回归分析,并采用隶属函数法综合评价不同油菜品种(系)根系的耐铝特性.结果表明:138份油菜品种(系)间各项根系指标差异有统计学意义(p<0.05);筛选出甘蓝型油菜幼苗期耐铝毒品种(系)27034,27036和27007等.根据灰色关联度及逐步回归分析结果,认为根据根长、根表面积、根体积、根交叉数等7个关键指标,可以初步判断甘蓝型油菜种质幼苗期的耐铝毒特性.通过这些方法综合评价油菜对铝的耐受性,可以避免单一指标的片面性和不稳定性,结果更为可靠.

QTL Mapping of Yield and Yield Components for Elite Hybrid Derived-RILs in Upland Cotton

A population of 180 recombinant inbred lines （RILs） was developed by single seed descended from the cross of high yield Upland cotton （Gossypium hirsutum L.） varieties Zhongmiansuo12 （ZMSI2） and 8891, the two parents of Xiangzamian2 （XZM2）. A genetic linkage map consisting of 132 loci and covering 865.20 cM was constructed using the RIL population chiefly with SSR markers. Yield and yield components were investigated for RILs in three environments in China. The purpose of the present research was to analyze the relationship between yield and its components and to map QTL for yield and yield components in cotton. QTL were tagged with data sets from single environment （separate analysis） and a set of data from means of the three environments （joint analysis）. A total of 34 QTL for yield and yield components were independently detected in three environments, whereas fifteen QTL were found in joint analysis. Notably, a stable lint percentage QTL qLP-A10-1 was detected both in joint analysis and in two environments of separate analysis, which might be of special value for marker-assisted selection. The QTL detected in the present study provide new information on improving yield and yield components. Results of path analysis showed that bolls/plant had the largest contribution to lint yield, which is consistent with the mid-parent heterosis value in F1. Accordingly, in cotton breeding, bolls/plant can be considered first and other yield components measured as a whole to implement variety enhancement and hybrid selection of cotton.

籼粳RILs孕穗期耐冷性研究

以昆明小白谷和大理早籼杂交培育的孕穗期耐冷性重组近交系(RIL)为材料进行籼粳稻区水稻耐冷性研究。结果表明: (1)籼粳稻区株高、穗下节长、穗长和总粒数均呈数量性状的分布特征。(2)籼粳稻区一些性状间的相关性存在一定的差异,冷凉粳稻区株高与结实率等性状密切关性;相反高温粳稻区穗颈长与穗部4个性状达极显著或显著相关。 (3)遗传研究表明对低温和高温均敏感的穗颈长和结实率受主效基因控制,多数弱耐冷单株的耐热性相对较强。

利用重组自交系(RILs)群体进行质量—数量性状的遗传分析——遗传模型和小麦产量性状遗传

本文提出了利用 RIL s群体进行质量数量性状分析的 4个遗传模型及统计分析方法。其中 ,模型 、 、 、 分别表示性状受 1对主基因、 2对独立的主基因、 2对 AABB× aabb型连锁的主基因、 2对 AAbb× aa BB型连锁的主基因与微效基因共同控制。可估算出主基因的加性效应 (dma,dmb)、互作效应 (im)、遗传方差 (σ2m)和连锁图距 (R) ,以及微效基因的遗传方差 (σ2 )等参数。利用 2个RIL s群体对小麦 8个产量性状分析结果表明 ,不但不符合正态分布的性状都能在表现型水平上检测到主基因的存在 ,符合正态分布的性状也都能在表现型水平上检测到主基因的存在 ,所分析的性状均是由主基因和微效基因共同控制的 ;主基因配适的模型有模型 、模型 和模型 ,其中 ,模型 即 2对主基因相斥型连锁所占比例较大 ;在 2对主基因存在时 ,大都有主基因间的互作效应 ,其值一般小于加性效应 ;主基因对变异的贡献大于微效基因 ,平均为 5 8.2 %。

利用籼粳交RILs群体的水稻粒形QTLs定位

为了深入剖析水稻粒形性状的遗传调控机理,以典型籼稻品种七山占（Qishanzhan）和典型粳稻品种秋光（Akihikari）为亲本构建的重组自交系群体为材料,于2011-2013年分别对各株系的粒长、粒宽和粒厚3个粒形性状进行表型测定,并基于完备区间作图法（ICIM）进行粒形性状基因定位研究。试验结果表明：共检测到27个控制粒形性状的QTLs,包括3个粒长QTLs,11个粒宽QTLs和13个粒厚QTLs,它们分布于第1,2,3,4,5,11和12号染色体上,可分别解释14.45%-38.48%,28.98%-52.36%和38.77%-44.23%的表型变异;进一步分析发现,在第3,5和12号染色体上检测到的粒形性状QTL位点较多,且呈簇分布;此外,检测到q GL12a,q GL12b,q GW1,q GW5a,q GT11a和q GT12b等6个较新的QTLs位点,其中控制粒宽的q GW5a连续3年表达稳定,是一个重演性极好的QTL位点。以上结果将为水稻粒形性状的QTL克隆和遗传改良奠定基础。

02428×合系35 RILs群体糙米和发芽糙米γ-氨基丁酸、抗性淀粉的遗传分析

以水稻02428×合系35的RILs群体及其亲本糙米和发芽糙米为材料,对糙米、发芽糙米各222个群体样品的γ-氨基丁酸、抗性淀粉含量进行测定,以期选育出高γ-氨基丁酸、高抗性淀粉的水稻新品种。研究结果表明,重组自交系糙米、发芽糙米γ-氨基丁酸含量差异不大,群体间存在广泛变异,由主效基因控制。重组自交系糙米、发芽糙米抗性淀粉含量差异大,发芽糙米抗性淀粉平均含量是该群体糙米的1.2倍,群体间存在广泛变异,呈偏态分布。高海拔冷凉气候有利于糙米高抗性淀粉含量的提升与进化。本研究可以为功能水稻的遗传及品种选育提供一定的理论依据。

籼粳交RILs剑叶气孔与光合特性的初步研究

以典型籼稻七山占和典型粳稻秋光构建的重组自交系(RILs)F10的202个株系为试材,研究剑叶气孔性状与光合特性及其相互关系的结果表明:七山占气孔密度显著高于秋光,RILs呈接近正态的连续分布,峰值接近中亲值,向正负双向表现明显的超亲遗传;按程氏指数分类,气孔密度表现为偏粳型>偏籼型>籼型>粳型,且粳型与籼型、偏籼型、偏粳型的差异分别达到了极显著水平,而籼型与偏籼型、偏粳型的差异不明显;气孔密度和气孔大小与光合特性的相关性均未达到显著水平,总体上气孔导度与光合速率和蒸腾速率呈极显著正相关,但是不同类型气孔导度与光合速率的关系以及气孔导度的主要影响因素还有待进一步深入研究。

利用RILs群体分析小麦粉品质性状与面条品质的关系

利用132个小麦重组自交系群体(R ILs),测定了不同群体小麦面粉蛋白品质性状、面条感官品质和面条质构特性,研究了品质性状与面条品质的相关关系,在此基础上,用逐步回归法筛选了影响面条感官品质和质构特性的关键因素,对影响面条品质的所有性状做了通径分析。结果表明,面筋指数、吸水率和干湿面筋含量是影响面条感官总评分的关键性状,而且面筋指数对总评分的直接效应正向最大;面筋指数、面团形成时间和干湿面筋含量是影响面条硬度的关键性状,面筋指数的直接作用和间接作用均为正向较大,与硬度呈极显著正相关关系;吸水率和蛋白质含量是影响煮熟面条最大拉力的关键性状,蛋白质的作用大于吸水率。面筋指数极大地影响着面条品质。

利用重组自交系(RILs)群体进行甜瓜第一雌花节位主基因+多基因混合遗传模型分析

以美国厚皮甜瓜品系WI998为母本,中国薄皮甜瓜品系3-2-2为父本杂交所得的包括185个家系的重组自交系群体(RILs)为试验材料,通过RIL主基因+多基因混合遗传模型分析法,在不同季节研究第一雌花节位(NFF)的遗传特点。结果表明:春季性状遗传受2对重叠性主基因+加性-上位性多基因混合遗传模型(E_1_8)控制,主基因遗传率为79.17%,多基因遗传率分别为20.83%;秋季受2对互补性主基因+加性-上位性多基因混合遗传模型(E_1_7)控制,主基因遗传率为61.94%,多基因遗传率分36.77%。甜瓜第一雌花节位受2对主基因控制,还受环境变异的影响。

基于F2和RIL群体鉴定棉花抗黄萎病主效QTL

【目的】通过对棉花抗黄萎病性状进行数量性状位点(quantitative trait locus,QTL)定位,鉴定可以应用于育种实践的能稳定检测到的主效QTL,为棉花抗黄萎病遗传改良奠定分子基础。【方法】以抗黄萎病品种中植棉2号和感黄萎病品种冀棉11号为亲本杂交的F2群体和重组自交系(recombinant inbred lines,RIL)群体作为作图群体,在对2个群体进行多环境黄萎病抗性鉴定和简单重复序列(simple sequence repeat,SSR)分子标记检测的基础上进行遗传连锁图谱构建,利用完备区间作图法进行QTL定位,并对获得的主效QTL置信区间进行候选基因挖掘。【结果】在F2:3家系和RIL群体中共检测到7个抗黄萎病QTL,能够在多个环境条件下重复检测到的QTL有4个,包括q VW-D05-1、qVW-D05-2、q VW-D05-4和qVW-D05-5。共线性分析表明上述4个QTL集中分布于D05染色体上2293776~3205058 bp和62407897~62582344 bp 2个区域。4个抗性QTL的聚合可以显著降低棉花黄萎病病情指数。qVW-D05-1在多个环境中的表型变异解释率均在10%以上,为抗黄萎病主效QTL。对qVW-D05-1置信区间内的基因进行了功能注释、黄萎病菌诱导后的表达模式分析和单核苷酸多态性(single nucleotide polymorphism,SNP)变异分析,初步推测Ghir_D05G038990、Ghir_D05G039060、Ghir_D05G039100、Ghir_D05G039110和Ghir_D05G039130为可能控制棉花黄萎病抗性的候选基因。【结论】在不同环境中共检测到7个抗黄萎病QTL,其中4个QTL被重复检测到,在主效QTL q VW-D05-1区间内筛选获得5个棉花抗黄萎病候选基因。这些稳定的抗黄萎病相关的QTL及其候选基因可应用于棉花抗黄萎病性状的分子标记辅助选择育种。