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BMC Genetics (1)
Journal of Experimental Botany (1)
PLoS ONE (1)
Jin, Weiwei (3)
Han, Yonghua (2)
Huang, Sanwen (2)
Zhang, Zhonghua (2)
Chen, Shaojiang (1)
Cheng, Zhouchao (1)
Dong, Xin (1)
Du, Yongchen (1)
Gu, Xingfang (1)
Ingvarsson, Pär K. (1)
Kang, Houxiang (1)
Li, Liang (1)
Li, Xuefeng (1)
Liu, Jinhua (1)
Lu, Jingyuan (1)
Melchinger, Albrecht E. (1)
Miao, Han (1)
Ren, Yi (1)
Staub, Jack E. (1)
Wang, Xiaowu (1)
Xie, Bingyan (1)
Xu, Xiaowei (1)
Year of Publication
Gametophytic and zygotic selection leads to segregation distortion through in vivo induction of a maternal haploid in maize
Melchinger, Albrecht E.
Journal of Experimental Botany
Production of maternal haploids via a male inducer can greatly accelerate maize breeding and is an interesting biological phenomenon in double fertilization. However, the mechanism behind haploid induction remains elusive. Segregation distortion, which is increasingly recognized as a potentially powerful evolutionary force, has recently been observed during maternal haploid induction in maize. The results present here showed that both male gametophytic and zygotic selection contributed to severe segregation distortion of a locus, named segregation distortion 1 (sed1), during maternal haploid induction in maize. Interestingly, analysis of reciprocal crosses showed that sed1 is expressed in the male gametophyte. A novel mapping strategy based on segregation distortion has been used to fine-map this locus. Strong selection for the presence of the sed1 haplotype from inducers in kernels with haploid formation and defects could be detected in the segregating population. Dual-pollination experiments showed that viable pollen grains from inducers had poor pollen competitive ability against pollen from normal genotypes. Although defective kernels and haploids have different phenotypes, they are most probably caused by the sed1 locus, and possible mechanisms for production of maternal haploids and the associated segregation distortion are discussed. This research also provides new insights into the process of double fertilization.
Defective kernel; haploid; maize; male gametophyte; pollen competitive ability; segregation distortion.
An integrated molecular cytogenetic map of Cucumis sativus L. chromosome 2
Integration of molecular, genetic and cytological maps is still a challenge for most plant species. Recent progress in molecular and cytogenetic studies created a basis for developing integrated maps in cucumber (Cucumis sativus L.).
In this study, eleven fosmid clones and three plasmids containing 45S rDNA, the centromeric satellite repeat Type III and the pericentriomeric repeat CsRP1 sequences respectively were hybridized to cucumber metaphase chromosomes to assign their cytological location on chromosome 2. Moreover, an integrated molecular cytogenetic map of cucumber chromosomes 2 was constructed by fluorescence in situ hybridization (FISH) mapping of 11 fosmid clones together with the cucumber centromere-specific Type III sequence on meiotic pachytene chromosomes. The cytogenetic map was fully integrated with genetic linkage map since each fosmid clone was anchored by a genetically mapped simple sequence repeat marker (SSR). The relationship between the genetic and physical distances along chromosome was analyzed.
Recombination was not evenly distributed along the physical length of chromosome 2. Suppression of recombination was found in centromeric and pericentromeric regions. Our results also indicated that the molecular markers composing the linkage map for chromosome 2 provided excellent coverage of the chromosome.
An Integrated Genetic and Cytogenetic Map of the Cucumber Genome
Staub, Jack E.
Ingvarsson, Pär K.
The Cucurbitaceae includes important crops such as cucumber, melon, watermelon, squash and pumpkin. However, few genetic and genomic resources are available for plant improvement. Some cucurbit species such as cucumber have a narrow genetic base, which impedes construction of saturated molecular linkage maps. We report herein the development of highly polymorphic simple sequence repeat (SSR) markers originated from whole genome shotgun sequencing and the subsequent construction of a high-density genetic linkage map. This map includes 995 SSRs in seven linkage groups which spans in total 573 cM, and defines ∼680 recombination breakpoints with an average of 0.58 cM between two markers. These linkage groups were then assigned to seven corresponding chromosomes using fluorescent in situ hybridization (FISH). FISH assays also revealed a chromosomal inversion between Cucumis subspecies [C. sativus var. sativus L. and var. hardwickii (R.) Alef], which resulted in marker clustering on the genetic map. A quarter of the mapped markers showed relatively high polymorphism levels among 11 inbred lines of cucumber. Among the 995 markers, 49%, 26% and 22% were conserved in melon, watermelon and pumpkin, respectively. This map will facilitate whole genome sequencing, positional cloning, and molecular breeding in cucumber, and enable the integration of knowledge of gene and trait in cucurbits.
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