Primary trisomic of rice: orgin, morphology, cytology and use in linkage mapping

Twelve primary trisomics of Oryza sativa L. were isolated from the progenies of spontaneous triploids and were transferred by backcrossing to the genetic background of IR36, a widely grown high yielding rice variety. Eleven trisomics can be identified morphologically from one another and from diploids. However, triplo 11 is difficult to distinguish from diploid sibs. -The extra chromosome of each trisomic was identified cytologically at pachytene stage of meiosis, and the chromosomes were numbered according to their length at this stage. The major distinguishing features of each pachytene chromosome were redescribed. -The female transmission rates varied from 15.5% for triplo 1, the longest chromosome, to 43.9% for triplo 12, the shortest chromosome. Seven of the 12 primary trisomics transmitted the extra chromosome through the male. The low level of chromosomal imbalance tolerated by rice and other evidence are interpreted to indicate that this species is a basic diploid. -Genetic segregation for 22 marker genes in the trisomic progenies was studied. Of a possible 264 combinations, involving 22 genes and 12 trisomics, 120 were examined. Marker genes for each of the 12 chromosomes were identified. The results helped establish associations between linkage groups and cytologically identifiable chromosomes of rice for the first time. Relationships between various systems of numbering chromosomes, trisomics, linkage groups and marker genes are described, and a revised linkage map of rice is presented

Rice BRITTLE CULM 5 (BRITTLE NODE) is Involved in Secondary Cell Wall Formation in the Sclerenchyma Tissue of Nodes

Several brittle culm (bc) mutants known in grasses are considered excellent materials to study the process of secondary cell wall formation. The brittle phenotype of the rice bc5 (brittle node) mutant appears exclusively in the developed nodes, which is distinct from other bc mutants (bc1, 2, 3, 4, 6 and 7) that show the brittle phenotype in culms and leaves. To address the defects of the rice bc5 mutant in node-specific cell wall formation, we analyzed tissue morphology and cell wall composition. The bc5 mutation was found to affect the cell wall deposition of node sclerenchyma tissues at 1 week after heading, the stage at which the cell wall sugar content is reduced, in the bc5 nodes, compared with wild-type nodes. Moreover, decreased accumulation of lignin and thickness of cell walls in the sclerenchyma tissues were also observed in the bc5 nodes. The amounts of cellulose and hemicellulose were reduced to 53 and 65% of those in the wild-type plants, respectively. Sugar composition and glycosidic linkage analyses of the hemicellulose showed that the accumulation of glucuronosyl arabinoxylan in bc5 nodes was perturbed by the mutation. The bc5 locus was narrowed to an approximately 3.1 Mb region of chromosome 2, where none of the other bc genes is located. The bc5 mutation appeared to reduce the expression levels of the OsCesA genes in the nodes after heading. The results indicate that the BC5 gene regulates the development of secondary cell walls of node sclerenchyma tissues

Parent and Peer Influences on Adolescent Delinquent Behavior and the Mediating Role of Self-Regulation

This study examined the influence of parent and peer variables on delinquent behavior, and explored whether the relationships were mediated by adolescent self-regulation. Two hundred thirty-eight third- and fourth year Filipino high school students responded to measures of parental induction and power-assertive discipline, parental nurturance, self regulation, peer delinquency, and self-reported delinquency. Correlation analysis indicated that power-assertive discipline and peer delinquency were associated with higher levels of delinquency and lower self-regulation. Conversely, inductive discipline and nurturance were associated with less delinquency and higher self-regulation. Regression analysis showed that peer delinquency and self-regulation contributed significantly to the prediction of delinquent behavior. Tests of mediation revealed that self regulation fully mediated the influence of parents\u27 power-assertive and nurturing behaviors and partially mediated the influence of peers \u27 delinquency on delinquent behavior

Chromosomal location of some mutant genes through the use of primary trisomics of rice

The chromosomal location of eight mutant genes was determined through primary trisomic tests. Each of the mutant genes was crossed with 12 primary trisomics, and genetic segregation was studied in the F<SUB>2</SUB> or backcross populations. Of the 96 possible combinations 78 were examined. The results permitted the localization of gene mp-1 on chromosome 1; mp-2, ch, and bc-4 on chromosome 3; Hg on chromosome 4; eui on chromosome 5; ygl on chromosome 10; and aul on chromosome 12

Relations between harsh discipline from teachers, perceived teacher support, and bullying victimization among high school students

This study examined how the experience of harsh discipline from teachers is related to students\u27 experience of bullying victimization in a Philippine high school. Respondents were 401 first- to fourth-year high school students of an urban public school in the Philippines. Using structural equation modeling, a hypothesized model with direct associations between harsh discipline and bullying victimization, and an indirect path via students\u27 perception of teacher support, was tested. The data adequately fit the model and showed that experiences of harsh teacher discipline predicted higher bullying victimization and students\u27 negative perception of teacher support. There were no significant indirect effects. The findings suggest that school discipline strategies may have repercussions on students\u27 behaviors and relationships, highlighting the teacher\u27s role in modeling and setting norms for acceptable behaviors. Future studies can examine further how teachers\u27 harsh or positive discipline behaviors relate to bullying