Biomedical subjects

Jack E Staub

Publications and source records attributed to Jack E Staub.

4 recordsLinked to original sources

PubMed2006

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.

Biomarkers↗

PubMed2004

Plastid sequence evolution: a new pattern of nucleotide substitutions in the Cucurbitaceae.

Nucleotide substitutions (i.e., point mutations) are the primary driving force in generating DNA variation upon which selection can act. Substitutions called transitions, which entail exchanges between purines (A = adenine, G = guanine) or pyrimidines (C = cytosine, T = thymine), typically outnumber transversions (e.g., exchanges between a purine and a pyrimidine) in a DNA strand. With an increasing number of plant studies revealing a transversion rather than transition bias, we chose to perform a detailed substitution analysis for the plant family Cucurbitaceae using data from several short plastid DNA sequences. We generated a phylogenetic tree for 19 taxa of the tribe Benincaseae and related genera and then scored conservative substitution changes (e.g., those not exhibiting homoplasy or reversals) from the unambiguous branches of the tree. Neither the transition nor (A+T)/(G+C) biases found in previous studies were supported by our overall data. More importantly, we found a novel and symmetrical substitution bias in which Gs had been preferentially replaced by A, As by C, Cs by T, and Ts by G, resulting in the G-->A-->C-->T-->G substitution series. Understanding this pattern will lead to new hypotheses concerning plastid evolution, which in turn will affect the choices of substitution models and other tree-building algorithms for phylogenetic analyses based on nucleotide data.

Base Composition↗

PubMed2003

Cucumis monosomic alien addition lines: morphological, cytological, and genotypic analyses.

Cucumis hystrix Chakr. (HH, 2n=24), a wild relative of the cultivated cucumber, possesses several potentially valuable disease-resistance and abiotic stress-tolerance traits for cucumber ( C. sativus L., CC, 2n=14) improvement. Numerous attempts have been made to transfer desirable traits since the successful interspecific hybridization between C. hystrix and C. sativus, one of which resulted in the production of an allotriploid (HCC, 2n=26: one genome of C. hystrix and two of C. sativus). When this genotype was treated with colchicine to induce polyploidy, two monosomic alien addition lines (MAALs) (plant nos. 87 and 517: 14 CC+1 H, 2n=15) were recovered among 252 viable plants. Each of these plants was morphologically distinct from allotriploids and cultivated cucumbers. Cytogenetic and molecular marker analyses were performed to confirm the genetic constitution and further characterize these two MAALs. Chromosome counts made from at least 30 meristematic cells from each plant confirmed 15 nuclear chromosomes. In pollen mother cells of plant nos. 87 and 517, seven bivalents and one univalent were observed at diakinesis and metaphase I; the frequency of trivalent formation was low (about 4-5%). At anaphase I and II, stochastic and asymmetric division led to the formation of two gamete classes: n=7 and n=8; however, pollen fertility was relatively high. Pollen stainability in plant no. 87 was 86.7% and in plant no. 517 was 93.2%. Random amplified polymorphic DNA analysis was performed using 100 random 10-base primers. Genotypes obtained with eight primers (A-9, A-11, AH-13, AI-19, AJ-18, AJ-20, E-19, and N-20) showed a band common to the two MAAL plants and C. hystrix that was absent in C. sativus, confirming that the alien chromosomes present in the MAALs were derived from C. hystrix. Morphological differences and differences in banding patterns were also observed between plant nos. 87 and 517 after amplification with primers AI-5, AJ-13, N-12, and N-20, suggesting that these plants may contain different C. hystrix chromosomes.

Agriculture↗

PubMed2003

The development and evaluation of consensus chloroplast primer pairs that possess highly variable sequence regions in a diverse array of plant taxa.

Although universal or consensus chloroplast primers are available, they are limited by their number and genomic distribution. Therefore, a set of consensus chloroplast primer pairs for simple sequence repeats (ccSSRs) analysis was constructed from tobacco (Nicotiana tabacum L.) chloroplast sequences. These were then tested for their general utility in the genetic analysis of a diverse array of plant taxa. In order to increase the number of ccSSRs beyond that previously reported, the target sequences for SSR motifs was set at A or T ( n >/= 7) mononucleotide repeats. Each SSR sequence motif, along with +/-200-bp flanking sequences from the first of each mononucleotide base repeat, was screened for homologies with chloroplast DNA sequences of other plant species in GenBank databases using BLAST search procedures. Twenty three putative marker loci that possessed conserved flanking sequence spans were selected for consensus primer pair construction using commercially available computer algorithms. All primer pairs produced amplicons after PCR employing genomic DNA from members of the Cucurbitaceae (six species) and Solanaceae (four species). Sixteen, 22 and 19 of the initial 23 primer pairs were successively amplified by PCR using template DNA from species of the Apiaceae (two species), Brassicaceae (one species) and Fabaceae (two species), respectively. Twenty of 23 primer pairs were also functional in three monocot species of the Liliaceae [onion (Allium cepa L.) and garlic (Allium sativum L.)], and the Poaceae [oat (Avena sativa L.)]. Sequence analysis of selected ccSSR fragments suggests that ccSSR length and sequence variation could be useful as a tool for investigating the genetic relationships within a genus or closely related taxa (i.e., tribal level). In order to provide for a marker system having significant coverage of the cucumber chloroplast genome, ccSSR primers were strategically "recombined" and named recombined consensus chloroplast primers (RCCP) for PCR analysis. Successful amplification after extended-length PCR of 16 RCCP primer pairs from cucumber ( Cucumis sativus L.) DNA suggested that the amplicons detected are representative of the cucumber chloroplast genome. These RCCP pairs, therefore, could be useful as an initial molecular tool for investigation of traits related to a chloroplast gene(s) in cucumber, and other closely related species.

Base Sequence↗