Variation in Chromosome Constitution of the Xiaoyan Series Partial Amphiploids and Its Relationship to Stripe Rust and Stem Rust Resistance

The wild relatives of wheat （Triticum aestivum L.） contain tremendous amounts of potentially useful genes and represent a promising source of genetic diversity for wheat improvement （Bommineni and Jauhar, 1997）. Thinopyrum ponticum （Popd.） Barkworth and D. R. Dewey [syn. Agropyron elongatum （Host） P. Beauv., Elytrigia pontica （Podp.） Holub, Lophopy- rum ponticum （Podp.） A. L6ve] （2n = 10x = 70）, has high crossability with various Triticum species. Numerous studies have shown that Th. ponticum carries many potentially valu- able resistance genes against biotic and abiotic stresses （Shannon, 1978; Cox, 1991; Zheng et al., 2014a,b）. Transferring the useful genes from Th. ponticum to common wheat through chromosome engineering had been a successful way to enhance the resistance of wheat to pests and diseases （Sharma et al., 1989; McIntosh, 1991）.

Predominance of constitutional chromosomal rearrangements in human chromosomal fragile sites

Chromosomal fragile sites (CFSs) are loci or regions susceptible to spontaneous or induced occurrence of gaps, breaks and rearrangements. In this work, we studied the data of 4535 patients stored at DECIPHER (Database of Chromosomal Imbalance and Phenotype in Humans Using Ensembl Resources). We mapped fragile sites to chromosomal bands and divided the 23 chromosomes into fragile and non-fragile sites. The frequency of rearrangements at the chromosomal location of clones found to be deleted or duplicated in the array/CGH analysis, provided by DECIPHER, was compared in Chromosomal Fragile Sites vs. non-Fragile Sites of the human genome. The POSSUM Web was used to complement this study. The results indicated 1) a predominance of rearrangements in CFSs, 2) the absence of statistically significant difference between the frequency of rearrangements in common CFSs vs. rare CFSs, 3) a predominance of deletions over duplications in CFSs. These results on constitutional chromosomal rearrangements are evocative of the findings previously reported by others relatively to cancer supporting the current line of evidence and suggesting that a common mechanism can underlie the generation of constitutional and somatic rearrangements. The combination of insights obtained from our results and their interrelationships can indicate strategies by which the mechanisms can be targeted with preventive medical interventions.

Perennial aneuploidy as a potential material for gene introgression between maize and Zea perennis

Hybridization,which allows for gene flow between crops,is difficult between maize and Zea perennis.In this study,we aim to initiate and study gene flow between maize and Z.perennis via a special aneuploid plant（MDT） derived from an interspecific hybrid of the two species.The chromosome constitution and morphological characters of MDT as well as certain backcross progenies were examined.Results from genomic in situ hybridization（GISH） indicate that aneuploid MDT consisted of nine maize chromosomes and 30 Z.perennis chromosomes.The backcross progenies of MDTxmaize displayed significant diversity of vegetative and ear morphology;several unusual plants with specific chromosome constitution were founded in its progenies.Some special perennial progeny with several maize chromosomes were obtained by backcrossing MDT with Z.perennis,and the first whole chromosome introgression from maize to Z.perennis was detected in this study.With this novel material and method,a number of maize-tetraploid teosinte addition or substitution lines can be generated for further study,which has great significance to maize and Z.perennis genetic research,especially for promoting introgression and transferring desirable traits.

Chromosomal Constitutions and Reactions to Powdery Mildew and Stripe Rust of Four Novel Wheat-Thinopyrum intermedium Partial Amphiploids

As a staple food crop for one-third of the world＇s population, common wheat （Triticum aestivum L., 2n = 6x = 42, AABBDD） plays an important role in humans＇ food security. However, the genetic variation of cultivated wheat has been dramatically narrowed by genetic erosion under the modem cultivation system, resulting in vulnerability to biotic and abiotic stresses （Jiang et al., 1994; Friebe et al., 1996）. The wild relatives of wheat represent a large reservoir of superior genes, and transferring these alien genes to modem cultivars through chromosome engineering is a successful method of broadening the genetic diversity of wheat （Chen et al., 2003;