基于SSR标记的不同组群杂交中籼稻亲本配组优势分析

本研究利用48个SSR标记将12个不育系(保持系)、8个恢复系划分为4个组群,并利用NCⅡ设计共配制96个组合,研究不同组群亲本配组的杂种优势表现。研究结果表明,不育系和恢复系分别被分为3和2个组群,共产生6种配组模式,两系主栽不育系×扬稻6号类群恢复系(G2×G3)、三系保持系×三系恢复系(G4×G1)、扬稻6号类群不育系×三系恢复系(G3×G1)三类配组模式杂种优势明显。进一步研究显示遗传距离与杂种优势之间相关不显著。生育期是三系恢复系与两系主栽不育系配组(G2×G1)杂种低产的限制因子。扬稻6号类群不育系×三系恢复系(G3×G1)是一种新的杂种优势模式,因此,筛选、培育与扬稻6号属于同一类群的新型不育系,可进一步拓宽现有三系恢复系的利用范围,提高籼型杂种优势利用水平。

杂交早稻稻米品质的改良

本文是关于改良杂交早稻米质方面的研究报道．通过以美国品种和中国品种杂交，选育出米质优良的温敏型雄性不育系香１２５Ｓ，所配制的香１２５Ｓ／Ｄ６８是一个早熟、高产、优质杂交水稻．作者认为“优势组群”和“强光生态型”在杂交早稻稻米品质改良中是非常重要的两个方面．

Identification of the Parentage of Corn Variety Using SSR Markers

[Objective] The study was to explore the molecular interpretation standards on parentage in the seeds of corn variety. [Method] With 16 hybrids and their parents and 202 inbred elites as materials for screening primers, the artificial groups of two standard diad and two standard triad were respectively established as the verification materials. Genomic DNA of seedlings was extracted by using CTAB method. 137 pairs of SSR primers were selected for SSR amplification and product detection, which was used for the parentage identification of maize varieties. [ Result] Twenty pairs of corn primers with high polymorphism information content （ PIC value）, clearly amplified bands and good reproducibility were screened from 137 pairs of corn SSR primers tested. The identification results of using SSR molecular were consistent with the actual situation. [ Conclusion] It is feasible to identify the parentage of maize variety using SSR markers.

Plant community composition and interspecific relationships among dominant species on a post-seismic landslide in Hongchun Gully, China

The 5.12 Earthquake in 2008 and 8.14 Debris Flow in 2010 resulted in large-scale landslides that disturbed vast areas of vegetation in the Hongchun Gully, Wenchuan County, China. To define the specific characteristics of vegetation restoration during natural recovery after catastrophic events,vegetation species composition and interspecific associations were investigated on this typical landslide. Field survey data selected from a total of 51 sample plots belonged to seven belt transects and were analysed by Schluter's variance ratio, pearson's chi-squared test, Spearman's correlation coefficients and ecological species groups. Plant communities on the landslide consisted of 78 species, 65 genera and52 families. Of the total of 78 species, 25 are identified as dominant species, among which Camptotheca acuminate, Toxicodendron vernicifluum, Coriaria nepalensis, Robinia pseudoacacia, Buddleja alternifolia, Anemone vitifolia and Nephrolepis auriculata play a constructive role during the natural afforestation. Moreover, according to environmental and ecological factors, these 25 dominant species could be divided into four ecological species groups.This study found that even though the landslide had frequently suffered from interference due to heavy rain, the vegetation succession processes are ongoing,and it is now at a shrub–herb community succession stage, which indicates that vegetation can naturally recover in the denuded sites. This study provides a useful insight into the ecological interactions and interdependence between plant species during the natural recovery of vegetation and provides valuable information on vegetation recovery modelling in the landslide area.

Social organization of a flock of Helmeted Guineafowl(Numida meleagris)at the Krugersdorp Game Reserve,South Africa

The social organization of marked Helmeted Guineafowl(Numida meleagris) was studied in the Krugersdorp Game Reserve(Gauteng Province,South Africa) during March 1982 to February 1984.Flock members(7-10 guineafowl) did not associate randomly.Helmeted Guineafowl must live in a sociable flock to survive in the wild.The highest ranking male(male A) formed the pivot of the daily activities of the flock,such as determining foraging direction.High ranking males(males A and B) associated closely to repulse conspecific intruders.Breeding females associated more often with the high ranking males during the breeding season.Although a pecking order was established among males,the frequency of agonistic actions within the flock was very low,which suggests that agonistic interactions are limited to maintain cohesion.Adult females remained between the dominant male and the juveniles to minimize victimization.The second highest ranking male(B) took center stage while the dominant male and his female left temporarily to breed and then the rest of the flock clustered around him to maintain the cohesive nature of the flock.Most adults assisted with the brooding of the chicks of the highest ranking male.Flocking is,among other functions,a predator surveillance strategy that enables the Helmeted Guineafowl to forage under conditions with very limited ground cover and to maximize food finding during winter.

Study of group discussion in EFL classroom teaching

Communicative Language Teaching （CLT） lays emphasis on communication in the classroom, pair and group activities and student involvement in the learning process. Amid the classroom activities, group discussion predominates in almost all EFL classroom teaching, characterized by maximized participation of language learners. Several elements contribute to a fruitful group discussion, namely, grouping, topic selection, process control and outcome presentation. The interdependence and interaction of all the elements help to build up a productive group discussion and finalize with novice ideas. In spite of all the advantages, some constraints on group discussion still deserve our attention.