Multiple Lateral Branching Research Articles

Regulatory Mechanisms of Strigolactones on the Development of Lateral Branches in Cucumber

Cucumber (Cucumis sativus L.) belongs to the cucumber genus of the Cucurbitaceae family, and the selection of cultivars with minimal or no lateral branches can enhance the cultivation management efficiency. The growth of lateral branches is inhibited by strigolactone. To investigate the regulatory mechanism of strigolactone on the lateral branch development in cucumber, the cultivar LZ1 exhibiting multiple lateral branches was selected as the experimental material. The axillae of the plants were infiltrated with 1, 5, and 10 μmol·L−1 germination releaser 24 (GR24) at the four- to five-leaf stage. It was identified that 1 μmol·L−1 GR24 exhibited the most potent inhibitory effect on cucumber lateral branches. Additionally, exogenous strigolactone decreased the auxin content in the apical bud and axillae and increased the auxin content in the stem. This inhibited polar auxin transport in the axillary bud and promoted polar auxin transport in the apical bud. The content of strigolactone in the axilla region of cucumbers was elevated, whereas the synthesis and expression of cytokinin in the same area were reduced. A low concentration of GR24 induced the expression of cucumber branched 1 (csbrc1), whereas a high concentration of GR24 downregulated the expression of cucumber lateral suppressor (cscls) and blind (csblind), which inhibited the growth of cucumber lateral branches.

Epistatic interaction between CsCEN and CsSHBY in regulating indeterminate/determinate growth of lateral branch in cucumber

Two genetic loci, det-ma (CsCEN) and det-lb, showed epistatic interaction on indeterminate/determinate growth of LB in cucumber. CsSHBY was identified as the candidate gene for det-lb locus. Plant architecture depends on the spatial regulation of meristems from both main axis (MA) and lateral branches (LBs). Fate (indeterminate or determinate) of these meristems is a crucial source of architectural diversity determining crop productivity and management. CENTRORADIALIS/TERMINAL FLOWER 1/SELF-PRUNING (CETS) gene family have been well known as pivotal regulators for indeterminate/determinate growth of MA. Nevertheless, genes that regulate LB indeterminacy/determinacy remained unclear. Cucumber (Cucumis sativus L.) has typical monopodial growth and multiple lateral branches. Both MA and LBs had indeterminate or determinate growth, and indeterminate/determinate growth of LB was controlled by two distinct loci, det-ma (CsCEN) and det-lb. In our study, based on bulked segregant analysis (BSA) method, the det-lb locus was mapped on a 60.6kb region on chromosome 1 harboring only one gene CsaV3_1G044330, which encoded a putative vacuolar-sorting protein (designated as CsSHBY). Multipoint mutations in CsSHBY were identified in D082 and D226, compared with CCMC, including nonsynonymous SNP mutations and a 6-bp deletion in exons. Further, qPCR showed that CsSHBY was highly expressed in lateral bud of CCMC, suggesting that CsSHBY might play an active role in regulating indeterminate/determinate growth of LB. Genetic analyses showed that det-ma (CsCEN) had an epistatic effect on det-lb (CsSHBY), and CsCEN could activate CsSHBY promoter by Dual luciferase and GUS activity assays. Meanwhile, Cscen or Csshby was found to influence auxin contents and CsYUCs and CsPINs expression levels. These findings provided new insights into precisely optimizing plant architecture for yield improvements.

The Chromatin Remodeling Factor BrCHR39 Targets DNA Methylation to Positively Regulate Apical Dominance in Brassica rapa

The SHPRH (SNF2, histone linker, PHD, RING, helicase) subfamily belonging to ATP-dependent chromatin remodeling factor is the effective tumor-suppressor, which can polyubiquitinate PCNA (proliferating cell nuclear antigen) and participate in post-replication repair in human. However, little is known about the functions of SHPRH proteins in plants. In this study, we identified a novel SHPRH member BrCHR39 and obtained BrCHR39-silenced transgenic Brassica rapa. In contrast to wild-type plants, transgenic Brassica plants exhibited a released apical dominance phenotype with semi-dwarfism and multiple lateral branches. Furthermore, a global alteration of DNA methylation in the main stem and bud appeared after silencing of BrCHR39. Based on the GO (gene ontology) functional annotation and KEGG (Kyoto encyclopedia of genes and genomes) pathway analysis, the plant hormone signal transduction pathway was clearly enriched. In particular, we found a significant increase in the methylation level of auxin-related genes in the stem, whereas auxin- and cytokinin-related genes were hypomethylated in the bud of transgenic plants. In addition, further qRT-PCR (quantitative real-time PCR) analysis revealed that DNA methylation level always had an opposite trend with gene expression level. Considered together, our findings indicated that suppression of BrCHR39 expression triggered the methylation divergence of hormone-related genes and subsequently affected transcription levels to regulate the apical dominance in Brassica rapa.

Mapping and linkage analysis of epistatic QTLs for gynoecious trait (F) in cucumber (Cucumis sativus L.)

ABSTRACT The QTL mapping for gynoecy in cucmber (Cucumis sativus L.)was carried out by using backcross populations (BC1F2 & BC1F3) of a cross using two inbred lines; one monoecious with multiple (≥ 5) lateral branching habit cv. Pusa Uday (Indian slicing type) and gynoecious exotic line Gy14 (American pickling type) with few lateral branches (1–2). QTL detection was performed by employing QTL Ici mapping software (version 4.1) of the two mapping populations. We detected seven gynoecious QTLs in two genomic regions (chromosome 5 and 6), on which three significant QTLs (qGyn 5.1, qGyn 6.5 and qGyn 6.6) had higher LOD score (10.5, 26.2, and 24.5) and phenotypic variance (5.9, 14.5 and 14.5%) in BC1F2 population. However, two significant QTLs (qGyn 5.1 and qGyn 6.1) accounted for gynoecism which could explain 22.90 and 12.88% of the phenotypic variation with the LOD score of 15.86 and 11.82 in linkage group 5 and 6, respectively in BC1F3 population. Out of 82 simple sequence repeats (SSR) markers, three (SSR00233, SSR15516 and SSR13251) was found tightly linked and flanked to gynoecious trait QTLs (qGyn6.5 and qGyn6.6) in BC1F2 population at <1.5 cM, which could be used for marker-assisted selection (MAS) in cucumber improvement programmes. In order to increase the productivity of Indian cucumber, the introgressed Indian gynoecious cucumber lines derived from an exotic genetic background using MAS may be directly used as a variety or parent of hybrid.

Taenia Saginata in Third-Generation Capsule Endoscopy

A 60-year-old woman presented with chronic abdominal pain and iron deficiency anemia (hemoglobin, 9.8 g/dL; ferritin, 8 μg/L). The patient was white, born in France, and had never traveled outside France. Initial endoscopic evaluation, with gastroscopy and colonoscopy, was normal. Gastroduodenal biopsies were also normal. Small bowel capsule endoscopy (Pillcam SB-III, Medtronic, Dublin, Ireland) diagnosed a Taenia saginata infection. The worm was found from the proximal jejunum, where young immature proglottids consisting of a chain of small segments wider than long were visible (Figure A). Then, the segments grow and stretch out gradually to become mature proglottids (Figure B). This Taenia was extended until the terminal ileum with gradual appearance of gravid proglottids, measuring about 20 mm long and 6 mm wide (Figure C and D). Mature and gravid proglottids are the reproductive structures of this hermaphrodite parasite; with inside male and female structures. On our images, some of these sexual structures are visible, in particular on the last gravid proglottids, with multiple lateral uterine branches (Figure C, blue arrow) and uterus (Figure D, black arrow). The parasite was visible on 75% of the transit time in the small bowel, estimating a size of 2–3 m. The prognosis was favorable after eradication of the Taenia by a single dose of praziquantel. On the Visual Diagnosis of Human Taeniasis by Capsule EndoscopyClinical Gastroenterology and HepatologyVol. 16Issue 7PreviewLe Mouel et al1 recently identified a case of human taeniasis caused by Taenia saginata by means of third-generation capsule endoscopy. The authors of the article provide 4 illustrative images of the tapeworm and, specifically, gravid proglottids containing a branched uterus are shown. Because after endoscopy no additional confirmatory diagnostic method is specified, we reckon that the images of this branched uterus were meaningful enough for the specific tapeworm identification. Capsule endoscopy is a diagnostic method with high sensitivity. Full-Text PDF

Cell-Biological Studies of Osmotic Shock Response in Streptomyces spp.

Polar growth is an intricate manner of growth for accomplishing a complicated morphology, employed by a wide range of organisms across the kingdoms of life. The tip extension of Streptomyces hyphae is one of the most pronounced examples of polar growth among bacteria. The expansion of the cell wall by tip extension is thought to be facilitated by the turgor pressure, but it was unknown how external osmotic change influences Streptomyces tip growth. We report here that severe hyperosmotic stress causes cessation of growth, followed by reprogramming of cell polarity and rearrangement of growth zones to promote lateral hyphal branching. This phenomenon may represent a strategy of hyphal organisms to avoid osmotic stress encountered by the growing hyphal tip.

Unconventional Shale Play: Multilateral Technology and Selective Fracturing

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 163959, ’Unconventional-Shale-Play Selective Fracturing Using Multilateral Technology,’ by Doug G. Durst, SPE, and Mario Vento, SPE, Halliburton, prepared for the 2013 SPE Middle East Unconventional Gas Conference and Exhibition, Muscat, Oman, 28-30 January. The paper has not been peer reviewed. Drilling, completing, and fracturing of unconventional-formation wells in North America have become commonplace for producing natural gas. It is less common to drill, complete, and fracture treat multiple lateral branches from a single main wellbore. Augmenting a multilateral well with selective fracturing of each leg is as straightforward as fracturing a single-horizontal well. In this project, a plug-and-perforate system was used to address ten or more intervals in each leg, with average stimulation pressures of up to 9,000 psi. Introduction Multilateral solutions enable working within a limited surface area, generating a reduced footprint while draining a much larger volume of reservoir from a single surface location. A few multilateral wells can minimize the effect, visibility, and liability of drilling operations to drain the entire reservoir, especially in environmentally sensitive or protected areas. Potential advantages of a multilateral system can be broken into two broad categories. First, reserves can be increased or production can be increased or accelerated over the life of the well. Second, the tangible and intangible costs of the project can be reduced. Stimulating a Multilateral Well Earlier techniques in vertical wells used conventional perforating, typically followed by ball diversion for isolation. Horizontal wellbores were treated with a few widely spaced intervals (four to eight zones), then longer horizontal sections were treated (with up to 90 zones) by use of newly developed techniques and systems. Originally, ball-actuated fracturing-sleeve completions were limited to 15 to 20 intervals because ball-size increments were limited by the internal diameter (ID) of the fracturing string. New systems are available in which additional subintervals are created within the original primary intervals. With this system, five metering valves, plus one baffled valve, can be placed within the previously defined single interval. Thereby, it is possible to have six valves within each of the (up to) 15 primary intervals, for a maximum of 90 valves or 90 points to initiate fractures within a horizontal wellbore, compared with the previous limit of approximately 15 intervals.

Effects of jasmonic acid, branching and girdling on carbon and nitrogen transport in poplar

• Here, we examined the impact of jasmonate (JA) treatment, branching and phloem girdling on ¹³C and ¹⁵N import, invertase activity and polyphenol accumulation in juvenile tissues of unbranched and branched hybrid poplar saplings (Populus nigra × P. deltoides). • The import of ¹³C to juvenile tissues was positively correlated with invertase activity at the treatment site and enhanced by JA. Both invertase activity and ¹³C import were greater in shorter, younger branches and smaller, younger leaves. By contrast, JA treatments, branching and girdling had little or no impact on ¹⁵N import. • In poplar saplings with multiple lateral branches, we observed almost no ¹³C movement from subtending source leaves into lateral branches above them, with or without JA treatment. The presence of potentially competing branches, treated with JA or not, girdled or not, had no impact on carbohydrate (CHO) import or polyphenol accumulation in target branches. • We conclude that poplar branches comprise modules that are relatively independent from each other and from the stem below in terms of CHO movement, carbon-based defence production and response to elicitors. By contrast, branches are closely linked modules in terms of nitrogen movement. This should produce trees that are highly heterogeneous in quality for herbivores.

USDA, ARS Beit Alpha Cucumber Inbred Backcross Line Population

Beit Alpha cucumber (Cucumis sativus L.) is a Mediterranean fresh-market or processed type that originated in Israel for use in openfield and protected production (Shaw et al., 2000; Villalta et al., 2003). This market type develops moderately small (15 to 18 cm in length), slightly curved, uniform green, fruit with fine, and white spines without ridges, which is economically important in many Mediterranean production areas and has potential for protected production in the United States (Hochmuth et al., 2004; Shaw et al., 2007; Villalta et al., 2003). The cultivation of Beit Alpha cucumber is relatively recent, and this market type originated as a selection from a local landrace. Selection was reportedly initiated around 1950 on the Beit Alpha (synonym Beit Alfa or Bet Alfa) Kibbutz (a collective agrarian community) found in northern Israel near the Gilboa ridge (Davidi, 2009; Shaw et al., 2004). The initial breeding on this market type eventually produced a monoecious uniform variety for open-field production (Davidi, 2009). Public research on this market class in the United States has focused on best management practices to maximize its production (Shaw et al., 2000, 2004, 2007) and Israeli breeding efforts [public and private (Hazera Seeds)] that have yielded such varieties as ‘Delilah’ (Davidi, 2009). Using Japanese, Indian, Chinese, Dutch, and American germplasm, more modern commercial varieties possess resistances to viruses and downy mildew. Based on DNA polymorphisms, the genetic base of cucumber is extremely narrow {3% to 8% among elite and exotic germplasm and 12% between botanical varieties [C. sativus var. sativus L. and var. hardwickii (R.) Alef.]} (Dijkhuizen et al., 1996; Horejsi and Staub, 1999). The genetic base of several cucumber market types has been estimated using various molecular markers, and the genetic distance (GD) among Mediterranean-types (including the Beit Alpha type) is considered relatively broad (GD = 0.09–0.55) when compared with other cucumber market classes such as the European Long type (GD = 0.00– 0.24) (Dijkhuizen et al., 1996). Although genetic information regarding Beit Alpha types is limited (Hochmuth et al., 2004; Soleimani et al., 2009), Beit Alpha market type germplasm has potential as source material for U.S. breeding programs that develop cultivars for protected (gynoecious, mutiple pistillate, parthenocarpic) and open-field production (vegetative vigor, shortened days to anthesis, multiple lateral branching) environments (Sun et al., 2006). Dutch and Israeli seed companies have conducted intensive breeding of Beit Alpha cucumber. However, there are few public institutions directing efforts toward reporting the genetics and diversity of Beit Alpha germplasm, and none have provided highly inbred, genetically diverse germplasm for unfettered use in public breeding programs. Because of the lack of genetic information, insufficient publicly released germplasm, and its recent, single source origin (Israel), the genetic base of Beit Alpha cucumber germplasm should be diversified to maximize its use in plant improvement. The inbred backcross breeding method (Wehrhahn and Allard, 1965) has been useful for broadening the genetic base of cucumber and providing novel populations for genetic analysis of complex traits (Owens et al., 1985a, 1985b). This breeding method, when used in conjunction with marker-assisted selection (MAS) for maximum genetic diversity, can provide an array of homozygous lines that are heterogeneous with large percentages of the recurrent parent genotype ( 87%). Therefore, a series of Beit Alpha inbred backcross lines (BC2S3; IBL) were developed through MAS and phenotypic selection and released in January 2011 by the Agricultural Research Service, U.S. Department of Agriculture through its web-based documentation system (ARIS). Markers used in MAS were single sequence repeats (SSR), sequence characterized amplified regions (SCAR), and single nucleotide polymorphisms (SNP), in which their complete description is given in Delannay (2009) and Delannay and Staub (2010). This is the first public release of genetically diverse but highly inbred Beit Alpha germplasm. The IBL were made available to cucumber breeders to supply a source from which they may develop Beit Alpha market types with increased genetic diversity and yield potential suitable for open-field and greenhouse production. These IBL have use for the genetic analysis of complex traits (e.g., yield and quality components) that are common to most cucumber improvement programs (e.g., characterization of epistatic interactions; Robbins et al., 2008; Tanksley et al., 1996).

USDA, ARS European Long Greenhouse Cucumber Inbred Backcross Line Population

Cucumber (Cucumis sativus L.; 2n = 2x = 14) is produced worldwide and is consumed as a fresh (fresh or slicing types) or as a processed vegetable [processing or pickling types and as a cooked vegetable (e.g., China)] product in several market classes (Staub et al., 2008). The European Long market-type cucumber is grown for the fresh market in protected-culture environments (primarily glasshouse and plastic ‘‘hoop houses’’). Harvestable fruit are 32 to 40 cm in length, smooth, dark green, fine-spined, and seedless (parthenocarpic, non-pollinated fruit set). Plants are gynoecious and develop multiple lateral branches that are pruned continuously, where single stems of plants are trained on trellis systems. Cucumber has an extremely narrow genetic base with 3% to 8% polymorphisms among elite and exotic germplasm and 12% between botanical varieties [C. sativus var. sativus L. and var. hardwickii (R.) Alef.] (Dijkhuizen et al., 1996; Horejsi and Staub, 1999; Meglic and Staub, 1996). The European Long market class has the narrowest genetic diversity [genetic distance (GD) = 0.00 to 0.24] among the major commercial cucumber market classes (e.g., Mediterranean types; GD = 0.09 to 0.55; Dijkhuizen et al., 1996; Horejsi and Staub, 1999). This is in large part the result of the initial use of relatively few PIs in germplasm development and the extensive use of the germplasm ‘‘Corona’’ in modern (since 1950) breeding (Staub et al., 2008; Kees Hertogh and Gerhard Reuling, personal communication, 2002). To our knowledge the last intensive, long-term public breeding effort for this market type ended in the 1950s (Andeweg, 1956). European Long Greenhouse cucumber breeding and genetics have been hampered by not only its lack significant genetic diversity, but also by the lack of appropriate genetic stocks for rapid genetic mapping of economically important traits and the inability to carry on strategic assessments of epistatic interactions. The inbred backcross breeding method (Wehrhahn and Allard, 1965) has been useful for broadening the genetic base of cucumber and providing novel populations for genetic analysis of complex traits in cucumber (Owens et al., 1985a, 1985b). Given the narrow germplasm base and the lack of ongoing public breeding efforts, a series of 116 European Long Greenhouse market-type IBL were developed (according to Wehrhahn and Allard, 1965) and released in Jan. 2011 by the Agricultural Research Service, U.S. Department of Agriculture. The IBL were developed by initially crossing an elite commercial European Long Greenhouse line and PI 432858 (China; long-fruited, Northern Chinese protected-culture type) followed by markerassisted backcrossing and self-pollination (Delannay, 2009; Delannay and Staub, 2010). A broad array of genetically diverse IBL is now available to cucumber breeders for developing long-fruited greenhouse market types with increased genetic diversity and yield potential suitable for protected-culture production. These IBL have use for the genetic analysis of complex traits (e.g., yield and quality components; characterization of epistatic interactions) that are common to most cucumber improvement programs (Robbins et al., 2008; Tanksley et al., 1996) and/or to evaluate cross-progeny derived from IBL and elite long-fruited germplasm during cultivar development.

The effects of hydroxy fatty acids on the hyphal branching of germinated spores of AM fungi

Two hydroxy fatty acids, tentatively identified previously in carrot root exudates, were tested for their effects on hyphal growth of the arbuscular mycorrhizal (AM) fungus, Gigaspora gigantea (Nicol. and Gerd.) Gerdemann and Trappe. Best results were achieved with a long-term bioassay (7–8 d) with nanomolar concentrations throughout the Petri dish in contrast to the rapid microinjection bioassay (16–24 h) in which nanogram quantities were injected near growing hyphal tips. When 5 nM 2-hydroxy fatty acids of various chain length were tested, the length of the hydroxyl fatty acid was significant since only 2-hydroxytetradecanoic acid (2OH-TDA) and to a slightly lesser degree, 2-hydroxydodecanoic acid (2OH-DDA) induced a hyphal growth response while 2-hydroxydecanoic acid (2OH-DA) and 2-hydroxyhexadecanoic (2OH-HDA) acid did not. The position of the hydroxyl group was critical since 5 nM 3-hydroxytetradecanoic acid (3OH-TDA) had no effect on hyphal growth. The length of the non-hydroxy containing straight chain fatty acid, per se, did not appear significant since none of these fatty acids had an effect on hyphal growth. The morphological growth response promoted by 2OH-TDA consisted of multiple lateral branches, spaced fairly regularly apart, along the primary germ tubes as well as some lateral branch formation off the major secondary hyphae. This growth response was identical to that observed when germinated spores were allowed to grow towards cultured carrot roots in vitro. This response to 2OH-TDA also was observed with an unidentified Gigaspora species but no morphological response was observed with Glomus intraradices Schenck and Smith. The results indicate that 2-hydroxy fatty acids are another putative category of root exudate signals perceived by Gigaspora species, stimulating an increase in elongated lateral branches.

Effects of radicular dentin treatments and luting materials on the bond of quartz fiber posts: scanning electron microscope study

To investigate the effects of radicular dentin treatments of sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) on the regional root canal bonding interface of quartz fiber posts using 2 luting materials with SEM analysis. Nine intact maxillary central incisors were sectioned and endodontically treated. Standardized post space preparations and acid etch were performed. All specimens were randomly divided into 3 groups (n = 3). D.T.LIGHT posts were placed into the root canal using one of three radicular dentin treatments (0.9% NaCl for 60 s, 10% NaOCl for 60 s, 17% EDTA for 60 s followed by 5.25% NaOCl for 60 s) in combination of one of two luting materials (DuoLink, LuxaCore) respectively (factorial design). Cervical, middle, apical sections of each teeth are used for SEM study and spectroscopy of dispersion energy (EDS) microanalysis. With the radicular dentin treatment with 10% NaOCl alone or with 17% EDTA followed by 5.25% NaOCl, longer and increased number of penetration of resin tags into the dentinal tubules were observed at the resin-dentin interfaces, and adhesive lateral branches could be found easily. EDS microanalysis showed increase in the infiltration behavior of the luting cement. Radicular dentin treatments provide good resin infiltration, which can produce a three-dimensional interlocking micronetwork of resin tags in the dentin tubules with multiple lateral branches that penetrate the intertubular dentin, thus positively influence the adhesion between dentin and the luting materials.

AtMBD9 modulates Arabidopsis development through the dual epigenetic pathways of DNA methylation and histone acetylation

Mutations within the Arabidopsis METHYL-CpG BINDING DOMAIN 9 gene (AtMBD9) cause pleotropic phenotypes including early flowering and multiple lateral branches. Early flowering was previously attributed to the repression of flowering locus C (FLC) due to a reduction in histone acetylation. However, the reasons for other phenotypic variations remained obscure. Recent studies suggest an important functional correlation between DNA methylation and histone modifications. By investigating this relationship, we found that the global genomic DNA of atmbd9 was over-methylated, including the FLC gene region. Recombinant AtMBD9 does not have detectable DNA demethylation activity in vitro, but instead has histone acetylation activity. Ectopic over-expression of AtMBD9 and transient DNA demethylation promotes flowering and causes partial recovery of the normal branching phenotype. Co-immunoprecipitation assays suggest that AtMBD9 interacts in vivo with some regions of the FLC gene and binds to histone 4 (H4). Gene expression profile analysis revealed earlier up-regulation of some flower-specific transcriptional factors and alteration of potential hormonal and signal transducer axillary branching regulatory genes. In accordance with this result, AtMBD9 itself was found to be localized in the nucleus and expressed in the flower and axillary buds. Together, these results suggest that AtMBD9 controls flowering time and axillary branching by modulating gene expression through DNA methylation and histone acetylation, and reveal another component of the epigenetic mechanism controlling gene expression.

Comparative analysis of marker-assisted and phenotypic selection for yield components in cucumber

Theoretical studies suggest that marker-assisted selection (MAS) has case-specific advantages over phenotypic selection (PHE) for selection of quantitative traits. However, few studies have been conducted that empirically compare these selection methods in the context of a plant breeding program. For direct comparison of the effectiveness of MAS and PHE, four cucumber (Cucumis sativus L.; 2n = 2x = 14) inbred lines were intermated and then maternal bulks were used to create four base populations for recurrent mass selection. Each of these populations then underwent three cycles of PHE (open-field evaluations), MAS (genotyping at 18 marker loci), and random mating without selection. Both MAS and PHE were practiced for yield indirectly by selecting for four yield-component traits that are quantitatively inherited with 2-6 quantitative trait loci per trait. These traits were multiple lateral branching, gynoecious sex expression (gynoecy), earliness, and fruit length to diameter ratio. Both MAS and PHE were useful for multi-trait improvement, but their effectiveness depended upon the traits and populations under selection. Both MAS and PHE provided improvements in all traits under selection in at least one population, except for earliness, which did not respond to MAS. The populations with maternal parents that were inferior for a trait responded favorably to both MAS and PHE, while those with maternal parents of superior trait values either did not change or decreased during selection. Generally, PHE was most effective for gynoecy, earliness, and fruit length to diameter ratio, while MAS was most effective for multiple lateral branching and provided the only increase in yield (fruit per plant).

Pyramiding QTL for multiple lateral branching in cucumber using inbred backcross lines

Multiple lateral branching (MLB) is a quantitatively inherited trait associated with yield in cucumber (Cucumis sativus L.; 2n = 2x = 14). Although quantitative trait loci (QTL) have been identified for MLB and QTL-marker associations have been verified by marker-assisted selection, the individual effects of these QTL have not been characterized. To test the effects of pyramiding QTL for MLB, molecular genotyping was utilized to create two sets (standard- and little-leaf types) of inbred backcross (IBC) lines possessing various numbers of QTL that promote branching. These IBC lines were evaluated for lateral branch number in two Wisconsin environments at three plant densities. Highly significant differences in the number of primary lateral branches were detected between spacings, leaf types, and lines, but not between locations. Lateral branch number decreased at higher plant densities in all genotypes, while genotype by environment and QTL by environment interactions were marginally non-significant. As the number of QTL increased among IBC lines, the number of branches did not generally change in the little-leaf lines, but decreased in the standard-leaf lines, demonstrating an epistatic effect related to genetic background during lateral branch development. The genomic location with the greatest effect on MLB was confirmed as the QTL that was previously mapped near the little-leaf locus (ll), while the addition of one specific QTL consistently decreased the number of lateral branches in standard-leaf lines. Although pyramiding QTL for MLB did not uniformly increase the number of lateral branches, pyramiding QTL in IBC lines allowed further characterization of individual QTL involved in MLB. Our results, coupled with those of previous studies indicate that lateral branch development in cucumber is determined by growing environment (i.e., plant spacing), genetic background, and QTL composition.

Efficiency of Recurrent Selection by Marker and Phenotype for Multiple, Quantitative Yield Components in Four Cucumber Populations

Four cucumber (Cucumus sativus L.) inbred lines were intermated then bulked maternally to create four base populations denoted as cycle 0 (i.e., Pop.1 C0, Pop.2 C0, Pop.3 C0, Pop.4 C0). Each of these populations underwent phenotypic selection (PHE; open-field evaluations), selection by marker (MAS; genotyping at 20 marker loci), and random mating (RAN; no selection) for three cycles. The four traits under selection, multiple lateral branching (MLB), gynoecious sex expression (GYN), earliness (EAR), and fruit length to diameter ratio (L:D), are quantitatively inherited, controlled by relatively few (two to six) QTL per trait and are directly related to yield. Using the same C0 populations and selection scheme allowed a direct comparison of the effectiveness of MAS and PHE. Because each C0 population varied for any given trait, the response to MAS and PHE was not the same for each population. In general, C0 populations that were inferior for a trait either responded favorably to selection or remained constant, while those with superior trait values either did not change or decreased. Both MAS and PHE provided improvements in all traits under selection in at least one population, with the exception of MAS for EAR. MAS and PHE were equally effective at improving MLB and L:D, but PHE was generally more effective than MAS for GYN and EAR. When considering all traits, responses to PHE were superior in three of the four populations. The population for which MAS was superior, however, showed the only increase in yield (fruit per plant), which was not under direct selection. These results indicate that both MAS and PHE are useful for multi-trait improvement in cucumber, but their effectiveness depends on the traits and populations under selection.

Population development by phenotypic selection with subsequent marker-assisted selection for line extraction in cucumber (Cucumis sativus L.)

Cucumber (Cucumis sativus L.; 2n = 2x = 14) has a narrow genetic base, and commercial yield of US processing cucumber has plateaued in the last 15 years. Yield may be increased by altering plant architecture to produce unique early flowering (days to flower, DTF), female (gynoecious, GYN), highly branched (multiple lateral branching, MLB), long-fruited (length:diameter ratio, L:D) cultivars with diverse plant statures. The genetic map position of QTL conditioning these quantitatively inherited yield component traits is known, and linked molecular markers may have utility in marker-assisted selection (MAS) programs to increase selection efficiency, and effectiveness. Therefore, a base population (C0), created by intermating four unique but complementary lines, was subjected to three cycles (C1-C3) of phenotypic (PHE) mass selection for DTF, GYN, MLB, and L:D. In tandem, two cycles of marker-assisted backcrossing for these traits began with selected C2 progeny (C2S) to produce families (F1[i.e., C2S x C2S], and BC(1) [i.e., F1 x C2S]) for line extraction, and for comparative analysis of gain from selection by PHE selection, and MAS. Frequencies of marker loci were used to monitor selection-dependent changes during PHE selection, and MAS. Similar gain from selection was detected as a result of PHE selection, and MAS for MLB (approximately 0.3 branches/cycle), and L:D (approximately 0.1 unit increase/cycle) with concomitant changes in frequency at linked marker loci. Although genetic gain was not realized for GYN during PHE selection, the percentage of female flowers of plants subjected to MAS was increased (5.6-9.8% per cycle) depending upon the BC1 population examined. Selection-dependent changes in frequency were also detected at marker loci linked to female sex expression during MAS. MAS operated to fix favorable alleles that were not exploited by PHE selection in this population, indicating that MAS could be applied for altering plant architecture in cucumber to improve its yield potential.

(255) A Comparison of Phenotypic and Marker-assisted Selection in Cucumber

To increase yield in cucumber (Cucumussativus L.), we designed a recurrent selection program utilizing phenotypic (PHE) and marker-assisted (MAS) selection for the development of multiple lateral branching (MLB; branches per plant), gynoecious, early genotypes possessing high fruit length to diameter ratio (L:D). These yield components are under genetic control of few quantitative trait loci (QTL; 2-6 per trait), which have been placed on a moderately saturated molecular linkage map. Four inbred lines, complementary for the target traits, were intermated and the resulting population underwent MAS and PHE, as well as random mating (RAN), for three cycles. Selections by PHE were visually made for all four traits at the whole plant level. Selections based on MAS contained the highest number of desired marker genotypes from 20 marker loci (SSR, RAPD, SCAR, SNP). Using the same selection scheme and intensity allowed a direct comparison of MAS to PHE. Selection was equally effective for MLB and L:D by MAS (3.5 and 3.0) and PHE (3.6 and 3.0), which were both superior to RAN (2.8 and 2.8). For earliness (days to anthesis) and gynoecy (percent female), MAS (41.8 and 26.6) was less effective than PHE (40.5 and 81.8) and RAN (41.0 and 80.9), which were equal. For yield (fruit per plant), RAN (1.90) and MAS (1.88) were equal, but less than PHE (2.15). After three cycles of PHE, further selection by MAS identified superior genotypes, which were intermated. Superior hybrids were selected by MAS and underwent one backcross generation. In some backcrosses, gains were made in every trait compared to the PHE Cycle 3 mean, while in other backcrosses, gains were made only in some traits. Improvement by MAS was very effective during line extraction for these yield components.

Development and Characterization of PCR Markers in Cucumber

Highly polymorphic microsatellites or simple sequence repeat (SSR), along with sequence characterized amplified region (SCAR) and single nucleotide polymorphisms (SNP), markers are reliable, cost-effective, and amenable for large scale analyses. Molecular polymorhisms are relatively rare in cucumber (Cucumis sativus L.) (3% to 8%). Therefore, experiments were designed to develop SSR, SCAR and SNP markers, and optimize reaction conditions for PCR. A set of 110 SSR markers was constructed using a unique, strategically applied methodology that included the GeneTrapper (Life Technologies, Gaithersburg, Md.) kit to select plasmids harboring microsatellites. Of these markers, 58 (52%) contained dinucleotide repeats (CT, CA, TA), 21 (19%) possessed trinucleotide repeats (CTT, ATT, ACC, GCA), 3 (2.7%) contained tetranucleotide repeats (TGCG, TTAA, TAAA), 4 (3.6%) enclosed pentanucleotide repeat (ATTTT, GTTTT, GGGTC, AGCCC), 3 (2.7%) contained hexanucleotide repeats (CCCAAA, TAAAAA, GCTGGC) and 21 possessed composite repeats. Four SCARs (L18-3 SCAR, AT1-2 SCAR, N6-A SCAR, and N6-B SCAR) and two PCR markers based on SNPs (L18-2H19 A and B) that are tightly linked to multiple lateral branching (i.e., a yield component) were also developed. The SNP markers were developed from otherwise monomorphic SCAR markers, producing genetically variable amplicons. The markers L18-3 SCAR and AT1-2 SCAR were codominant. A three-primer strategy was devised to develop a codominant SCAR from a sequence containing a transposable element, and a new codominant SCAR product was detected by annealing temperature gradient (ATG) PCR. The use of a marker among laboratories can be enhanced by methodological optimization of the PCR. The utility of the primers developed was optimized by ATG-PCR to increase reliability and facilitate technology transfer. This array of markers substantially increases the pool of genetic markers available for genetic investigation in Cucumis.

Morphological characteristics of Impatiens flanaganiae Hemsl. grown under different light conditions

Impatiens flanaganiae Hemsl. is a rare plant which preferentially grows in shady conditions and exhibits strong apical dominance. The morphological plasticity of I. flanaganiae in response to light intensity in laboratory conditions was investigated. Unbranched plantlets of I. flanaganiae propagated from tubers were exposed to three light regimes: 30, 55 and 280 microeinsteins m− 2 sec− 1 for a period of seven weeks. Plants grown under lower light intensity (30–55 microeinsteins m− 2 sec− 1) developed long unbranched stems about 65 cm in length and fewer leaves with a large leaf area. In contrast, reduced stem extension (up to 35 cm) and multiple lateral branches were observed in plants exposed to higher light intensity (280 microeinsteins m− 2 sec− 1). A significant increase (at 5% level) in the number of leaves in plants from this variant was found to be inversely proportional to the leaf area. Extended exposure of the plants to higher light intensities seems to be stressful and resulted in abnormal biochemical and morphological changes such as chlorosis, necrosis and curling of the leaves. The strong increased premium on lateral growth of I. flanaganiae, induced by light intensity of 280 microeinsteins m− 2sec− 1 resulted in a greater number of lateral branches which were found to be suitable for its rapid and more efficient propagation in vivo by cuttings or in vitro by shoot tip culture.