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.

Selection of Maize Inbred Lines with High Regeneration and Susceptibility to Agrobacterium tumifacien

Ten-maize inbred lines of maize （Zea mays L.） with high-induction rate and proliferation ability of embryonic calli were selected from 70-maize inbred lines by immature embryo culturing. Some of the embryonic calli were transferred onto regeneration medium to examine the ability of regeneration, some were transformed via Agrobacterium tumifaciens C58 carrying intron-β-glucuronidase （gus） gene, and GV3301 carrying the green fluorescent protein （gfp） gene to study the susceptibility of different genotypes in maize to A. tumifaciens. All embryonic calli initiated from 10-maize inbred lines were able to regenerate into plantlets, and the regeneration frequencies of inbred lines 6010, 6038, 6015, 6051, and 6060 were 61.11%, 31.94%, 45%, 33.33%, and 56.94%, respectively, which were higher than that of other lines. Analysis of variance indicated that the susceptibility of the various genotypes in maize to A. tumifacien C58 showed a significant difference among each other, and the inbred lines 6010, 6015, 6051, 6050, 6058, 6060, 6069, 6077 were susceptible to A. tumifacien C58, of which frequency of gus expression were over 70%. Expression of GFP was observed in six-inbred lines （6050, 6015, 6051, 6058, 6069, 6077）. The inbred lines 6051, 6010, 6015, 6060, and 6050 had the high regeneration and the susceptibility to A. tumifaciens C58; and the inbred lines 6051, 6015, and 6060 had the high regeneration and the susceptibility to Agrobacterium tumifaciens GV3301.

Genetic Relation Analysis on Ramie[Boehmeria nivea(L.)Gaud.]Inbred Lines by SRAP Markers

The objective of this article is to reveal the variations of ramie inbred lines in DNA level and discuss their molecular background to provide a theoretical basis for ramie cross breeding. In the present study, the genetic relationships among 33 inbred line accessions and two wild types that originated from China and Brazil were estimated using sequence-related amplified polymorphism （SRAP） markers. The results showed that 33 out of 81 primer combinations turned out to be polymorphic and 332 polymorphism bands were obtained. On the basis of the appearance of the markers, the genetic relationships were analyzed using unweighted pair-group method of arithmetic average cluster analysis （UPGMA）, and the genetic Jaccard similarity coefficients were calculated. The inbred-lines originating from China and Brazil formed a cluster suggesting a possibility that the Brazilian cultivars could have developed from cultivars introduced from China. Within ramie inbred-lines, the groupings also indicated that the greatest genetic relationship among cultivars was correlated to the region of origin of cultivars. The results provided the evidence that SRAP was an efficient approach, suitable for taxonomic analysis of ramie inbred lines, To the authors＇ knowledge, this is the first application of SRAP marker on the systematics of ramie inbred lines.

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.

Analysis on Breeding Potential of 17 Maize Inbred Lines from Land Races

[Objective] The primary objective of this study was to estimate combining ability and genetic parameters of 17 new inbred lines.[Method] By using 11 commonly used maize inbred lines from Southwest China as testers and incomplete diallel cross design,combining ability and heterosis of 17 new inbred lines bred from the land races in Sichuan Basin and its surrounding areas were analyzed.In addition,the genetic parameters and heterotic groups were also investigated based on combining ability.[Result] P1-1,P1-16 and P1-14 with the better comprehensive characters can be directly used in maize breeding program.The SCA of P1-10×P2-4 was high in most traits.It is more possible to obtain high-yield hybrid combinations by the pattern Sipingtou × Lancaster.GCA variance was bigger than SCA variance in four traits such as rows per ear,grains per row,which were affected by the environments slightly and should be selected at early generations;while SCA variance was bigger than GCA variance in five traits such as 100-grain weight and plant weight,which were significantly influenced by environment and thus should be selected in later generations.[Conclusion] The paper will provide theoretical basis for further improvement of local maize varieties.

Genetic Diversity for Yield and Yield Contributing Characters of Short Statured Maize Inbred Lines

Genetic diversity is one of the useful tools to select appropriate lines for hybridization. Twenty short-statured maize inbred lines were taken for present study, which were collected from CIMMYT India and Mexico through Plant Breeding Division, Bangladesh Agricultural Research Institute (BARI), Gazipur. This experiment was conducted from November 2015 to April 2016 to identify parental lines to produce single cross short statured maize hybrids. From the genetic diversity studies, the importance of both additive and non-additive gene actions for the expression of yield and yield contributing characters were found. Values of vector I and II revealed that both the vectors had positive values for date of silking, plant height, rows/cob, grains/row and yield. These results indicated that these five characters had highest contribution towards divergence. Based on the relative magnitude of D2 values;20 inbred lines were grouped into five clusters. Seven inbred lines were selected on the basis of genetic diversity and per se performance which will be crossed separately in a half-diallel fashion to develop hybrids.

Combining Ability and Correlation of Ear Characteristics of Twenty Maize Inbred Lines

The combining ability and correlation of eight ear characteristics in 99 maize hybrids generated by crossing nine female parents with 11 male parents were analyzed by incomplete diallel cross （NC II ） design. The results showed that the line F6 had the highest general combining ability （GCA） for yield, followed by F7, M3, M4 and M8. All of the five lines have great potential in maize breeding. The cross combination M3xF10 had the highest specific combining ability （SCA） for yield, showing strong heterosis. Heritability analysis of ear characteristics showed that GCA variance was higher than SCA variance in ear diameter, number of rows per ear and seed rate, and they were mainly controlled by the additive gene effect, indicating that that the selections for these traits are effective at early generations. The other three traits had lower SCA, for which the selections should be carried out at late generations. The correlation analysis revealed that ear length, number of grains per row, ear diameter, number of rows per ear, 100-seed weight and seed rate had extremely significant positive correlations with grain yield per plant. Among them, number of grains per row had the most significant effect on yield per plant. Barren tip length had a significant negative correlation with grain yield per plant. Therefore, we concluded that the combinations with more grains per row and shorter barren tip should be selected to achieve high yield of maize.

Analysis on Combining Ability and Genetic Parameters of Main Agronomic Characters of 22 Maize Inbred Lines

The general combining ability（GCA）, special combining ability（SCA） and genetic parameter of ten characters of 22 maize inbred lines including plant height and ear height were analyzed using 10×12 through incomplete diallel cross（NC Ⅱ）.The results showed that：（1） Among the 22 maize inbred lines, the yield GCAs of11 HN 097, 11 HN 099, 11 HN 105 and 11 HN 110 were high, which were elite inbred lines to collocate hybridized combinations with strong heterosis. The yield of11 HN110 × 11 HN097, 11 HN110 × 11 HN105, 11 HN112 × 11 HN 097 and 11 HN 106 × 11 HN 104 were in the first four place. The yielding abilities, adaptabilities and yielding stabilities of the four combinations can be further identified by experiment. The heredities of the ten characters were mainly controlled by additive gene effect whereas the influence of non-addictive gene effect was small. The narrow heritabilities of plant height, ear height, ear rows, ear length, kernels per row,100-grain weight and seed-producing percentage were more than 50%. The variances were mainly caused by heredity and early-generation selection should be conducted. The narrow heritabilities of ear diameter, bare tip length and yield was low, which should not be selected in early-generation.

Combining Ability Analysis of Panicle Traits in Six CIMMYT Maize Inbred Lines

In this study, six CIMMYT maize inbred lines and five representative do- mestic maize inbred lines were used as parental lines. By using incomplete diallel cross design, 30 hybrid combinations were developed to analyze the general com- bining ability （GCA）, specific combining ability （SCA） and total combining ability （TCA） of seven panicle traits in six CIMMYT maize inbred lines. The results showed that CIMBL98 and GEMS13 were excellent inbred lines with good compre- hensive performance; CIMBL98 × 340 and GEMS13×Chang 7-2 were superior combinations.

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.

Results of Selection Studies of Alfalfa Based on Inbred Lines

The collection of alfalfa in the context of ecology-geographical groups was studied, consisting of 1,078 samples, including 985 samples of the cultivated species--M, sativa L. and M. varia Mart., and 93 samples for other wild species. Highly productive samples are allocated in the three-year cycle of using the grass stand in the haymaking regime. Individual genotypes of isolated samples are used for selection of inbred lines required for the formation of synthetic varieties. Inbred lines were created by forced self-pollination on genotypes with signs of self-fertility. Methodical experiments established the efficiency of bringing inbred lines to generations J2 and J3. In this case, the overall combinational ability reaches a potential value, and further incubation outside of J2 and J3 does not significantly affect its value. With the selection of the best inbred lines in J2 and J3, the lucerne varieties： Kokorai, Osimtal and Kokbalausa, which are protected by patents and author＇s certificates, have been created in accordance with the general combination ability and their inclusion in the structure of synthetic varieties.

Determination of the Number of SSR Alleles Necessary for the Analysis of Genetic Relationships Between Maize Inbred Lines

The amount of molecular marker information has considerable impact on the results of studies of crop germplasm genetic relationships in crop. The number of alleles required to reveal genetic relationship in maize inbred lines is a theoretical issue that needs to be addressed. In this study, 112 pairs of SSR （simple sequence repeat） primers and 97 maize inbred lines were selected to study the relationship between the number of inbred lines and the number of SSR primers and alleles required for a stable cluster. The results showed that the number of SSR primers is not tightly associated with the stability of the cluster analysis results, while an increase in the number of alleles can significantly improve the stability of cluster analysis results. The number of inbred lines （X） is significantly associated with the number of alleles required for stable cluster analysis （Y）, and the regression equation is Y- 600.8xe（-15.9/x）. This equation can be used to calculate the number of SSR alleles required for a genetic relationship study of maize inbred lines. These results provide a reference for determining of SSR alleles number in genetic relationship analysis of maize inbred line and other crop germplasm.

Factors influencing seed reserve utilization during seedling establishment in maize inbred lines

Strong seedlings are essential for high yield.To explore the foundation of strong seedlings,we investigated various factors influencing the conversion and distribution of seed storage reserves during seedling establishment in maize inbred lines.Three maize inbred lines were used to explore the effects of seed size,seed vigor,illumination duration,temperature,water content,and salt concentration of the seedling medium on the utilization of seed storage reserves during seedling establishment.The results showed that the conversion rate of small seeds was 3.69 to 17.71%higher than that of large seeds.Moreover,prolonged illumination time was conducive to the formation of strong seedlings.However,low temperature,drought stress and salt stress reduced the conversion rate of seed storage reserves and increased the root/shoot ratio.These results could be used to guide field management during seedling emergence and develop improved germplasm with a high conversion rate of seed storage reserves.

Genetic Diversity Analysis of 13 Maize Inbred Lines by SSR Molecular Markers

This paper used SSR molecular markers to perform the genetic diversity analysis on 13 ordinary inbred lines of maize of different sources in order to divide heterotic groups of maize inbred line and predict heterosis. Using 12 pairs of SSR primers,a total of 47 allelic variants were detected in 13 inbred lines,2-5 alleles were detected for each pair of primers,an average of 3. 9,and polymorphism information content varied from 0. 379 to 0. 828. According to the cluster analysis,the 13 inbred lines could be divided into 5 groups.

Breeding Technology of Sunflower Inbred Lines with Four Generations in One Year

The breeding technology of sunflower inbred lines with four generations in one year was explored through the research on the biological characteristics of sunflower itself and the breeding status of sunflower inbred lines using the young embryo culture technology,the greenhouse seedling technology and field test planting,based on sunflower field breeding and planting combined with greenhouse planting.The reasonable selection of planting sites as the core of the breeding technology of sunflower inbred lines with four generations in one year is a guarantee.Embryos can be taken 7-10 d after pollination to enter the next generation of cultivation,thus shortening the generational cultivation cycle.The establishment of a breeding method of sunflower inbred lines with four generations in one year reduces the cost of breeding and has a practical role and significance for the field of sunflower inbred line breeding technologies.

Quantitative trait locus analysis of lateral branch-related traits in cucumber(Cucumis sativus L.)using recombinant inbred lines

A group of 224 recombinant inbred lines (RILs) was derived from a narrow cross between 2 cucumber (Cucumis sativus L.) lines, namely, S94 (Northern China type with weak lateral branch growth potential and early lateral branch sprouting time) and S06 (Northern European type with strong lateral branch growth potential and late lateral branch sprouting time). These lines were then used for investigating lateral branch-related traits. A total of 36 quantitative trait loci (QTLs) were detected for the following 4 lateral branch-related traits: lateral branch average length (LBAL), lateral branch total length (LBTL), lateral branch number (LBN), and first lateral branch node (FLBN). Further, each QTL explained 3.1% (lbtl2.1, spring) to 32.3% (lbn2.3, spring) of the observed phenotypic variance. Eleven QTLs (lbal1.1, lbtl1.1, lbn1.2, flbn1.2, etc.) for different traits were found to be clustered on the e23m18d-ME23EM6c section (7.4 cM) of linkage group (LG) 1; further, 15 QTLs (lbal2.1, lbtl2.1, lbn2.1, flbn2.1, etc.) were found to be clustered on the S94A1-ME4SA4a section (13.9 cM) of LG2. Twenty-one QTLs explained more than 10% of the phenotypic variance. Moreover, lbtl1.3 (autumn, 26.2%, logarithm of odds (LOD) = 17.4; spring, 26.9%, LOD = 17.9) had stable position and contribution in both seasons. Several se-quence-anchor markers (CMBR40, F, CS30, S94A1, CSWTA11B, etc.) were closely linked with some QTLs for LBAL, LBTL, LBN, and FLBN, which can be used for the marker-assisted selection to improve the plant architecture in cucumber breeding.

Evaluation of drought tolerance in ZmVPP1-overexpressing transgenic inbred maize lines and their hybrids

The vacuolar proton-pumping pyrophosphatase gene(VPP)is often used to enhance plant drought tolerance via genetic engineering.In this study,the drought tolerance of four transgenic inbred maize lines overexpressing ZmVPP1(PH4CV-T,PH6WC-T,Chang7-2-T,and Zheng58-T)and their transgenic hybrids was evaluated at various stages.Under normal and drought conditions,the height and fresh weight were greater for the four transgenic inbred maize lines than for the wild-type(WT)controls at the germination and seedling stages.Additionally,the transgenic plants exhibited enhanced photosynthetic efficiency at the seedling stage.In irrigated and non-irrigated fields,the four transgenic lines grew normally,but with increased ear weight and yield compared with the WT plants.Moreover,the ear weight and yield of the transgenic hybrids resulting from the PH4CV-T×PH6WC-W and Chang7-2-T×Zheng58-W crosses increased in the non-irrigated field.Our results demonstrated that the growth and drought tolerance of four transgenic inbred maize lines with improved photosynthesis were enhanced by the overexpression of ZmVPP1.Moreover,the Chang7-2 and PH4CV transgenic lines may be useful for future genetic improvements of maize hybrids to increase drought tolerance.

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）

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.