Phenotypic Characterization and QTL/Gene Identification for Internode Number and Length Related Traits in Maize

Internode number and length are the foundation to constitute plant height, ear height and the above-ground spatial structure of maize plant. In this study, segregating populations were constructed between EHel with extremely low ear height and B73. Through the SNP-based genotyping and phenotypic characterization, 13 QTL distributed on the chromosomes (Chrs) of Chr1, Chr2, Chr5-Chr8 were detected for four traits of internode no. above ear (INa), average internode length above ear (ILaa), internode no. below ear (INb), and average internode length below ear (ILab). Phenotypic variation explained (PVE) by a single QTL ranged from 6.82% (qILab2-2) to 12.99% (qILaa5). Zm00001d016823 within the physical region of qILaa5, the major QTL for ILaa with the largest PVE was determined as the candidate through the genomic annotation and sequence alignment between EHel and B73. Product of Zm00001d016823 was annotated as a WEB family protein homogenous to At1g75720. qRT-PCR assay showed that Zm00001d016823 highly expressed within the tissue of internode, exhibiting statistically higher expression levels among internodes of IN4 to IN7 in EHel than those in B73 (P Zm00001d016823 might provide novel insight into molecular mechanism beyond phytohormones controlling internode development in maize.

Mathematical expression for the relationship between internode number and internode length for bamboo, Phyllostachys pubescens

We analyzed the relationship between internode number and intemode length for one of the largest bamboo, Phyllostachys pubescens Mazel ex Houz. For 50 sample culms with various sizes felled in a pure stand of P. pubescens, the intemode number was assigned from base to tip and the length for each internode was directly measured. The result indicated that the intemode length should be cumulated from base to tip, and then the cumulated internode length should be relativized by the total culm length. It was inappropriate to relativize the internode length by the maximum intenode length. In addition, the relationship between the relative internode number （the intemode number relativized by the total number of intemodes） and the relative cumulated internode length should be described not by a power function but by a sigmoid function such as the third-order function. The determined function enabled us to estimate the actual internode length, with the root mean squared error being 4 cm. In conclusion, the mathematical expression presented here, i.e., the relativization of the cumulated internode length by the total culm length and the application of the sigmoid function, will be useful in describing the relationship between internode number and internode length for P. pubescens.

The Genetic Analysis of Internode Length in Bitter Gourd

Performing the genetic mechanism research of internode length in bitter gourd has important guiding significance for making breeding strategy. A cross was made between CN19-1 and Thai4-6, and an F2 segregation population was constructed. The genetic characteristic of the internode length was analyzed through employing the major gene plus polygene mixed genetic model. The results showed that the internode length was continuous distribution in the F2 population. The optimum model for internode length genetic analysis was B-1. The additive effect values of two pairs of major genes controlling the internode length were 3.206 3 and 2.638 3, respectively, which showed a positive effect. The dominant effect values were-3.434 6 and-1.459 6, respectively, which showed a negative effect. The dominant degree of major genes is-1.07 and-0.55, respectively, indicating that the first pair of major genes was over dominant and the second pair of major genes was incompletely dominant. The heritability of the major gene was 82.25%, indicating the genetic stability was high. This study could provide a theoretical reference for the breeding of bitter gourd.

Morphogenetic responses of Populus alba L. under salt stress

The morphogenetic responses to salt stress of TunisianPopu-lus alba clones were studied in order to promote their plantation in dam-aged saline areas. One year-old plants of threeP. alba clones （MA-104, MA-195 and OG） were subjected to progressive salt stress by irrigation during two consecutive years. The plants were grown in a nursery, inside plastic receptacles containing sandy soil and were irrigated with tap water （control） or 3-6 g/l NaCl solution. During this study, leaf epinasty, elongation rate, vigor, internode length, plant architecture, and number of buds were evaluated. Test clone response was highly dependent on the applied treatment and degree of accommodation.The most pronounced alterations were induced under 6g/l of NaCl treatment including leaf epinasty, leaf elongation rate delay, vigor decrease, internode length shortening, and morphogenetic modifications. These responses were less noticeable in the MA-104 clone with respect to the two other clones. The salt effect induced a delay in the leaf elongation rate on the MA-195 and OG clones leading to an early leaf maturity. The vigour and internode length of the MA-104 clone was less affected than the other clones. The OG clone was the most salt-sensitive thus, it developed shorter branches and more buds number than MA-195 and MA-104. The effect of long-term salt stress was to induce early flowering of theP. alba clones which suggests that mechanism of salt accommodation could be developed.

Effect of Dominant Semi-Dwarf Gene on Plant Height and Its Related Traits and Sensitivity to Gibberellic Acid in Rice

Six pairs of tall and dwarf near-isogenic lines derived from a dominant semi-dwarf mutant （Y98149） were selected to study height expression and sensitivity to gibberellic acid （GA3）. The lengths of the 4-5th internode, the 3rd, 2nd, 1st internodes from the top and the panicle length in the six dwarf near isogenic lines were 97.2%, 53.3%, 65.1%, 61.9% and 94.7% of those in the six tall ones, respectively, indicating that the dominant semi-dwarfing gene significantly inhibited the internode elongation. Moreover, Y98149 （mutant type） was more sensitive to GA3 than Y98148 （wild type）, and had a lower GA3 concentration in plant, about 78% of Y98148.