Elite Parental Lines Research Articles

Overexpression of ZmSPL12 confers enhanced lodging resistance through transcriptional regulation of D1 in maize.

Overexpression of ZmSPL12 confers enhanced lodging resistance through transcriptional regulation of D1 in maize.

Phenotypic and genetic dissection of cadmium accumulation in roots, nodes and grains of rice hybrids

Rice accumulates higher levels of cadmium (Cd) in grain than other cereals, and hybrid rice varieties cover around half of the total rice area in China. Therefore, understanding the phenotypic and genetic characteristics of Cd accumulation in rice hybrids is vital for food safety. An incomplete diallel cross design was used to analyse the heritability and combining ability of Cd accumulation in rice hybrids growing in soil contaminated with Cd. The quantitative real-time PCR was used to detect the gene expressions that related to Cd uptake and transport. The Cd contents in brown rice, nodes and roots were detected by ICPOES, and the Cd contents in xylem sap were detected by ICPMS. Additive effects dominated the Cd accumulation in brown rice, upper nodes, and the Cd translocation efficiency from roots to nodes of hybrids. The Cd accumulation in brown rice was positively correlated with Cd accumulation in upper nodes and translocation efficiency from roots to nodes. Regarding the general combining ability, the restorer lines R2292 and R2265, and the male sterile lines KeBX58S, Ke20A, Ke76-1BS and Ke244-1BS were found to be potential elite parental lines for developing hybrid rice with low Cd accumulation. Hybrid rice with low Cd accumulation in brown rice can be derived from parental lines with low general combining ability for Cd content in brown rice.

Use of single seed descent versus pedigree selection for development of elite parental lines in castor (Ricinus communis L.)

Use of single seed descent versus pedigree selection for development of elite parental lines in castor (Ricinus communis L.)

Hybrid Sorghum Product Development and Production.

There are many moving parts involved in developing and taking a new commercial hybrid to market. Sorghum [Sorghum bicolor (L.) Moench] hybrid development involves development of parental lines based on a cytoplasmic male sterile system including the pollen parent (R-line) and seed parents (A- and B-lines). New parental lines are developed by recombining existing elite parental lines to create new breeding populations or by adding specific traits of interest to existing parental lines by crossing elite lines with donor parents. Molecular markers are utilized to identify plants with particular traits of interest during parental line development. Newly developed parental lines are crossed together or with other elite parental lines to create new hybrid combinations. New hybrid combinations are evaluated in target geographies for improved yield, good agronomics, and specific traits of interest. Multi-year, multi-location evaluations are used to identify hybrid entries with improved yield, stable performance, and good agronomics. Evaluation of the parental lines involved in these new hybrids helps establish the produceability and potential cost of goods which have direct impact on the potential commercial release of new hybrid products.

Pedigree-Based Deciphering of Genome-Wide Conserved Patterns in an Elite Potato Parental Line.

Elite parental lines are more likely to breed fine varieties, but knowledge about elite parents and their genetic backgrounds is limited. In this paper, we investigated the pedigree relationships of potato varieties bred worldwide and in China. Several elite parents were identified, and these parents were more frequently used as parents in breeding programs across different time periods and countries. We next used 2b-RAD, a reduced-representation sequencing method, to genotype the elite parent Mira and 24 of its offspring. These cultivars span 5 generations, making this lineage the longest continuous pedigree among Chinese bred potatoes. A total of 47,314 tetraploid single nucleotide polymorphisms (SNPs) identified by FreeBayes were used to trace the conserved segments of the Mira genome. The conserved segments had identical or similar allele-specific SNPs across the analyzed genotypes. In Mira, 3,788 segments comprising over 10,000 bp, or 20.8% of the genome, were defined as conserved segments. These segments contain genes involved in crucial biological processes that are of special interest to breeders. These regions, which have been conserved across generations of highly selective breeding, may be helpful for further breeding and performing genome-wide breeding by design.

Effect of Sowing Date on Grain Endosperm Chalkiness of Different Rice Varieties

Grain chalkiness is a major cause of low quality in many rice-producing areas of the world. Though, little is known about the relationship between different sowing dates and the characters of grain chalkiness for grain quality improvement in rice. In this study, the grain chalkiness characters of twenty-one and seven rice varieties were investigated across four and six sowing dates in two years. The results showed a wide range variation of grain chalkiness in diverse varieties across sowing dates, and a positive correlation between chalkiness rate (CR) and the temperature during grain filling phase for all of the varieties. Slight correlation between grain chalkiness area (CA) and the temperature during grain filling phase was also observed for the test varieties in 2015. The chalkiness characters of some varieties were dramatically sensitive to heading dates, while other varieties had a low level of CA and CR across different sowing dates. Improvement of grain chalkiness could be realized by selecting optimum sowing dates in rice production and varieties with low and stable chalkiness could be considered as the elite parental lines in the artificial breeding of the new rice varieties. Therefore, our results have paved the way for the improvement of grain chalkiness in rice.

Genome-wide indel/SSR scanning reveals significant loci associated with excellent agronomic traits of a cabbage (Brassica oleracea) elite parental line \u201801\u201320\u2019

Elite parental lines are of great significance to crop breeding. To discover unique genomic loci associated with excellent economic traits in the elite cabbage inbred-line ‘01–20’, we performed comparisons of phenotypes as well as whole-genome insertion-deletion/simple sequence repeat loci between ‘01–20’ and each of its five sister lines. ‘01–20’ has a range of excellent agronomic traits, including early-maturing, and improvements in plant type and leaf colour. Eight unique loci were discovered for ‘01–20’ and ‘01-07-258’, another elite line similar to ‘01–20’ at the whole-genome level. In addition, two excellent double-haploid lines derived from a cross of ‘01–20’ also inherited these loci. Based on the quantitative trait locus association results, five of these loci were found to be associated with important agronomic traits, which could explain why the elite parent ‘01–20’ possesses greener outer leaves, a more compact and upright plant-type, rounder head, shorter core length, and better taste. Additionally, some of these loci have clustering effects for quantitative trait loci associated with different traits; therefore, important genes in these regions were analysed. The obtained results should enable marker-assisted multi-trait selection at the whole-genome level in cabbage breeding and provide insights into significant genome loci and their breeding effects.

QTL mapping for agronomic traits using multi-parent advanced generation inter-cross (MAGIC) populations derived from diverse elite indica rice lines

In rice many QTL have been reported for yield and related traits using various bi-parental mapping populations. However, few of the well characterized genes/QTL have been successfully used in breeding for improved trait performance. One of the reasons is that the mapping populations used are irrelevant to breeding. Association mapping has also been used in identifying marker-trait associations that are effective in more complex background. However, the results from association mapping using diversity panels are difficult to be exploited in breeding, since most of the accessions had poor performance in many important agronomic traits. In this study, a genome-wide association study (GWAS) was performed using three multi-parent advanced generation inter-cross (MAGIC) populations derived from elite indica lines (DC1, DC2 and 8-way) to identify QTL for 14 traits including yield, yield components and other related traits. The three MAGIC populations were phenotyped in the dry season (DS) and wet season (WS) of 2014 at the headquarters of the International Rice Research Institute (IRRI) and genotyped with a Rice SNP chip containing 4,500 markers. A total of 26 QTL on all chromosomes except 7, 9 and 11 were identified for 10 traits in the DS or WS. Six, two, 12, 10 and 20 out of the 26 QTL were identified in the DC1, DC2, 8-way, DC12 (DC1+DC2) and RMPRIL (DC1+DC2+8-way) populations, respectively. Nine of the QTL corresponded to known QTL/genes, including qFLW4 for FLW, qTGW3 and qTGW5 for TGW, qFGN4 for FGN, qSBN4 for SBN, qPH1.1 and qPH1.2 for PH, qHD3 and qHD6 for HD. All these nine QTL were identifiable using the RMPRIL population while only eight, seven, six and one could be identified using the 8-way, DC12, DC1 and DC2 populations, respectively. The 8-way population was more powerful than the DC1, DC2 and DC12 populations. The joint analysis, which combines different populations (e.g., DC12 and RMPRIL), increased the number of QTL identified and mapping resolution. The study showed that MAGIC populations derived from diverse elite parental lines can be used to detect QTL, which are ideal for linking gene identification and practical breeding. GWAS using such MAGIC populations had higher detection power (compared to assembled populations) and higher resolution (compared to biparental populations). The identified QTL are directly applicable, since the populations are good breeding populations as well.

Development of Jatropha hybrids with enhanced growth, yield and oil attributes suitable for semi-arid wastelands

Attention has been focused on the utilization of useful genetic resources in developing elite parental lines and making Jatropha hybrids for incorporating superior traits in Jatropha germplasm. Evaluations of morphological and yield contributing traits in F1 progeny have been made and hybrids having high seed yield and oil content have been identified. Multiplication of these hybrid lines was undertaken through stem cuttings. To develop Jatropha hybrids through intraspecific hybridization, twenty three accessions were collected from different parts of the country and grown on wastelands under semi-arid conditions. All the germplasm were assessed for desirable traits and cross-combinations were made between identified accessions of J. curcas based on considerable seed yield and higher oil content. Growth and yield performance was recorded from plants raised through stem cuttings of various cross combinations and studies were undertaken in four leading hybrids along with their respective parents. Two years old plants developed from the cross IC565735 × IC565739 proved to be the best with 75 % fruit set, 300 g seed yield per plant and 39.02 % oil content.

Soybean [Glycine max (L.) Merrill]: Importance as A Crop and Pedigree Reconstruction of Korean Varieties

Chaeyoung Lee, Man-Soo Choi, Hyun-Tae Kim, Hong-Tai Yun, Byungwook Lee, Young-Soo Chung, Ryan W. Kim, and Hong-Kyu Choi. Plant Breeding and Biotechnology -0001;3:179-96. https://doi.org/10.9787/PBB.2015.3.3.179

QTL mapping for combining ability in different population-based NCII designs: a simulation study

The NCII design (North Carolina mating design II) has been widely applied in studies of combining ability and heterosis. The objective of our research was to estimate how different base populations, sample sizes, testcross numbers and heritability influence QTL analyses of combining ability and heterosis. A series of Monte Carlo simulation experiments with QTL mapping were then conducted for the base population performance, testcross population phenotypic values and the general combining ability (GCA), specific combining ability (SCA) and Hmp (midparental heterosis) datasets. The results indicated that: (i) increasing the number of testers did not necessarily enhance the QTL detection power for GCA, but it was significantly related to the QTL effect. (ii) The QTLs identified in the base population may be different from those from GCA dataset. Similar phenomena can be seen from QTL detected in SCA and Hmp datasets. (iii) The QTL detection power for GCA ranked in the order of DH(RIL) based > F2 based > BC based NCII design, when the heritability was low. The recombinant inbred lines (RILs) (or DHs) allows more recombination and offers higher mapping resolution than other populations. Further, their testcross progeny can be repeatedly generated and phenotyped. Thus, RIL based (or DH based) NCII design was highly recommend for combining ability QTL analysis. Our results expect to facilitate selecting elite parental lines with high combining ability and for geneticists to research the genetic basis of combining ability.

Production and evaluation of transgenic sorghum for resistance to stem borer

Transgenic sorghum plants were produced through particle bombardment and Agrobacterium methods in two elite, but recalcitrant genotypes of Sorghum bicolor L. Moench. Use of target cells from developing tissues (immature embryos and multiple shoot buds), pre-culture of target tissue, small size of target tissue (2–3 mm), and regular subculture improved the selection and regeneration efficiencies. Addition of amino acid l-cysteine during co-cultivation and blotting sheet interface was helpful for complete decontamination of Agrobacterium tumefaciens and regeneration of transgenic plants. We demonstrated production of transgenic sorghum plants expressing a Bacillus thuringiensis lepidopteran toxin, through tailored in vitro protocols. Our results showed that decontamination of agrobacteria employing subtle treatments aided recovery of transgenic plants in recalcitrant genotypes. We generated 14 independent transgenic lines carrying different classes of B. thuringiensis toxin genes, cry1Aa and cry1B. Many single copy events were generated in two elite parental lines, CS3541 and 296B. Accumulation of the B. thuringiensis protein in leaves during the susceptible period of plant growth ranged from 35 to 500 ng/g fresh leaf tissue. Comprehensive insect bioassays for tolerance to spotted stem borer (Chilo partellus) were conducted through leaf disk and whole plant assays. Transgenic progeny plants showed 20–30% of damage as compared to 70–80% in non-transformed controls.

Improving rice yield and quality by QTL pyramiding

To facilitate marker-assisted transfer of desirable genes for improvement of yield traits, we used a set of backcross recombinant inbred lines (BRIL) derived from two elite parental lines, ‘Zhenshan97’ and ‘93-11’, to resolve a quantitative trait loci (QTL) cluster for heading date and yield-related traits in rice. Four main-effect QTL (qHD6.1, qHD6.2, qHD7, and qHD8) and four epistatic QTL affecting heading date in the BRIL were detected in two experimental trials. The major QTL (qHD8) was confirmed in three heterogeneous inbred families (HIF) that segregated for this target region, and narrowed down to a 20-kb segment in a large HIF-derived population. qHD8 was found to interact with qHD7 and had a pleiotropic effect responsible for heading date and yield components. To test usability of the identified QTL in rice improvement, we further developed near-isogenic lines (NIL) containing one or more target genes by marker-assisted transfer of ‘93-11’ alleles at qHD8, qHD7, and qHD6.1, and the GS3 gene for grain size into ‘Zhenshan97’. The pyramid line NIL(qHD8 + GS3) had higher yield potential, longer grains, and a more suitable heading date than ‘Zhenshan97’. Comparison of the NIL showed existence of epistasis between alleles at different loci and background effect on qHD8, which are very important for pyramiding of desirable alleles at the target QTL. These results will be particularly useful not only to understand the genetic basis of yield-related traits but also to improve the efficiency of marker-assisted selection for favorable loci in rice breeding programs.

Fine mapping a major QTL for flag leaf size and yield-related traits in rice

Leaf size is a major determinant of plant architecture and yield potential in crops. A previous study showed that the genomic region of chromosome 1 contains a major quantitative trait locus (QTL) for flag leaf size in a set of backcross recombinant inbred lines derived from two elite parental lines (Zhenshan 97 and 93-11). In the present study, the QTL (qFL1) was shown to explain a large proportion of the variation in flag leaf size (leaf length, width and area) in derived populations (BC(2)F(3) and BC(3)F(2)) in multiple environments. Using a large segregating population, we narrowed the location of qFL1 to a 31kb region containing four predicted genes. Expression of one of these genes, OsFTL1, differed between leaves in near-isogenic lines carrying alleles of Zhenshan 97 and 93-11. qFL1 had a pleiotropic effect on flag leaf size and yield-related traits. Conditional QTL analysis of the derived population (BC(3)F(2)) supports the assertion that qFL1 is the QTL for flag leaf length and exhibits pleiotropy. Pyramiding of qFL1 with two known genes (GS3 and Wx) from 93-11 into Zhenshan 97 enlarged flag leaves, improved grain size and amylose content, and increased yield per plant, but slightly delayed heading date. These results provide a foundation for the functional characterization of the gene underlying the pleiotropic effects of qFL1 and for genetic improvement of the plant architecture and yield potential of rice.

English

To explore the possibility to improve N6 medium for callus induction and plant regeneration from maize immature embryos, comparative experiments were conducted to screen the optimal calcium concentration for the callus induction medium and the subculture medium modified from N6 medium and to examine the effects of uniconazole and ABT root promoting powder supplement on plant regeneration and root generation. According to the results, the calcium concentration of N6 medium was increased from 1.13 to 5 mmol/l for callus induction and subculture. Uniconazole from 0.25 and 0.5 mg/l and ABT root-promoting powder of 0.5 mg/l were suggested to be supplemented to the regeneration medium and the root generation, separately. On these improved media, the frequency of callus induction, the relative proliferation rate of callus subculture, the regeneration rate and the average root biomass of the regenerated plantlets increased significantly. All these improvements facilitate the establishment of acceptor system from elite parental inbred lines of commercial hybrids andprovide a solid basis for transgenic manipulation of maize.   Key words: ABT root-promoting powder, calcium, callus induction, immature embryo, maize, N6 medium, plant regeneration, uniconazole.

Quality characteristics and field performance of selectable marker-free transgenic rice with antisense Wx gene and improved quality derived from the elite parents of hybrid indica rice

In rice grains, high amylose content (AC) is correlated with poor grain quality, particularly in indica hybrid rice. To obtain indica hybrid rice with improved cooking and eating qualities, we introduced the antisense Waxy ( Wx) gene into 2 elite parental lines of indica hybrid rice by using co-transformation methods. Subsequently, we selected several elite homozygous transgenic lines that did not contain the selectable marker. The expression of the endogenous Wx gene of the selected transgenic lines was significantly downregulated, resulting in low AC in the mature seeds; moreover, the AC in some lines reduced to the level observed in glutinous rice. With the decrease in AC, the gel consistency of the transgenic rice became softer, and the gelatinization temperature tended to be higher than those of the wild types, especially in the case of the Longtefu-derived transformants. We also analyzed the pasting properties of the selected transgenic low-AC lines, and we noted an improvement in the pasting properties of the transgenic rice lines. The results from a field trial indicated that the grain weights of the transgenic lines with lower AC exhibit remarkable reduction compared with those of the wild types.

Determination of phenolic content, composition and their contribution to antioxidant activity in specialty potato selections

In order to identify elite parental lines for use in breeding programs emphasizing human health benefits, specialty (colored) potato selections from the Texas Potato Variety Development Program were analyzed for antioxidant activity (AA) using 2,2-diphenyl-l-picrylhy-drazyl (DPPH) and 2,2-azinobis (3-ethyl-benzothiazo-line-6-sulfonic acid) (ABTS) radical assays, total phenolic content (TP) using Folin-Ciocalteu reagent (FCR), and phenolic composition using high performance liquid chromatography (HPLC). Total AA ranged from 157 μg trolox equivalents (TE)/gfw to 832 μg TE/gfw and 810 μg TE/gfw to 1622 μg TE/gfw using the DPPH and ABTS assays, respectively. TP ranged from 221 μg chlorogenic acid equivalents (CGAE)/gfw to 1252 μg CGAE/gfw. Selection COH2F2-2P/P had the highest AA and TP. Purple flesh selections had the highest AA and TP, followed by red flesh and yellow flesh selections. Selections with similar flesh color did not differ significantly in AA and TP. A significant positive correlation was observed between AA and TP. Chlorogenic acid, gallic acid, catechin, caffeic acid, and malvidin-3-(p-coumaryl rutinoside)-5-galactoside were the major polyphenols identified. Chlorogenic acid accounted for 50 to 70% of TP, followed by catechin, gallic acid and caffeic acid. Contribution of individual phenolics in specialty potatoes to AA was calculated using pure standards. Chlorogenic acid contributed 28 to 45% to AA, followed by gallic acid, catechin and caffeic acid.

Retrocruzamento como uma estratégia de identificar genótipos e desenvolver populações segregantes promissoras em aveia

O objetivo deste trabalho foi estimar a utilização do método de retrocruzamento entre genitores elite para obtenção de maior probabilidade de desenvolver progênies superiores de aveia que propiciem elevado êxito na seleção. Foram coletados dados dos caracteres: número de panículas por planta e rendimento de grãos da planta individual em kg ha-1. Foram utilizados cinco genótipos de aveia (UPF 16, UPF 18, UFRGS 7, UFRGS 17 e URPel 95/015), cruzados de forma dialélica. Através de retrocruzamentos, foram desenvolvidas as populações RC1P1, RC1P2, RC1P1F2, RC1P2F2, RC2P1 e RC2P2, e, a partir dos genitores, foram produzidas as gerações F1 e F3. Os híbridos F1, as populações F3 e os retrocruzamentos foram avaliados a campo no ano agrícola de 2003. A superioridade dos retrocruzamentos, em relação à população F3, foi dependente do cruzamento. Os genitores UPF 16, UFRGS 7 e UFRGS 17 produziram progênies progressivamente melhores quando as constituições dos mesmos foram incrementadas na população. Estes resultados foram evidenciados em 75% dos cruzamentos, nos quais os referidos genótipos participaram. Por outro lado, UPF 18 e URPEL 95/015 evidenciaram genes menos favoráveis para elevar o potencial genético do rendimento de grãos nas combinações testadas, com tendência a reduzir o desempenho das progênies com o aumento de suas participações nas hibridações.

Development of stem borer resistant transgenic parental lines involved in the production of hybrid rice

Stem borer resistant transgenic parental lines, involved in hybrid rice, were produced by Agrobacterium-mediated gene transfer method. Two pSB111 super-binary vectors containing modified cry1Ab/ cry1Ac genes driven by maize ubiquitin promoter, and herbicide resistance gene bar driven by cauliflower mosaic virus 35S promoter were, used in this study. Embryogenic calli after co-cultivation with Agrobacterium were selected on the medium containing phosphinothricin. Southern blot analyses of primary transformants revealed the stable integration of bar, cry1Ab and cry1Ac coding sequences into the genomes of three parental lines with a predominant single copy integration and without any rearrangement of T-DNA. T 1 progeny plants disclosed a monogenic pattern (3:1) of transgene segregation as confirmed by molecular analyses. Furthermore, the co-segregation of bar and cry genes in T 1 progenies suggested that the transgenes are integrated at a single site in the rice genome. In different primary transformants with alien inbuilt resistance, the levels of Cry proteins varied between 0.03 and 0.13% of total soluble proteins. These transgenic lines expressing insecticidal proteins afforded substantial resistance against stem borers. This is the first report of its kind dealing with the introduction of Bacillus thuringiensis (Bt) cry genes into the elite parental lines involved in the development of hybrid rice.

Mapping wound-response genes involved in post-harvest physiological deterioration (PPD) of cassava (Manihot esculenta Crantz)

The genome locations of the wound-response genes that were expressedduring the post-harvest physiological deterioration (PPD) of cassava, suchas phenylalanine ammonia lyase, β-1.3 glucanase, hydroxyprolinerich glycoprotein, catalase, 1-aminocyclopropane 1-carboxylate, cysteineprotease inhibitor, aspartic protease, a partial cDNA for serine/threonineprotein kinase and peroxidase, have been identified on the frameworkmolecular genetic map of cassava. Also, molecular markers linked toputative quantitative trait loci (QTLs) influencing PPD of cassava weremapped using an F1mapping population derived from elite parentallines (TMS 30572 × cm 2177-2). A molecular linkage map previouslyconstructed based on the segregation of 240 RFLP, 100 RAPD, 85microsatellite and five isoenzyme markers on 144 F1 individuals wasused for the QTL mapping.A set of 10 molecular markers with a significant association with putativeQTLs for PPD were identified based on probability values < 0.005in order to minimize the detection of false positives. Based on single-markerregression, eight putative QTLs located on the linkage groups G, P, L, U,and X of the female-derived framework map were found to explain between 5–12% of the phenotypic variance of the PPD. In the male-derived frameworkmap, two putative QTLs on linkage groups C and L explained 13% and11% of this variance, respectively. This study thus identified the majorgenome regions of cassava related to physiological post-harvestdeterioration, thereby providing tools for the identification of gene(s)controlling this trait.