Calibration Experiments of CR-39 with ^(20)Ne,^(28)Si,^(40)Ar and ^(56)Fe Ions of more than 100 MeV/u

A calibration experiment of CR-39 with Ne ions for space heavy ion identification has been performed. It is necessary for studying the mechanism of mutation breeding induced by space particles. In the experiment, 20Ne ion beams with nominal energy of 230 MeV/u and density of 500 cm-2 supplied by HIMAC were used to irradiate a stack of 25 pieces of CR-39 films vertically. After degraded by a binary filter,

Genetic and physical fine- mapping of the Sc locus conferring indica-japonica hybrid sterility in rice (Oryza sativa L.)

Hybrid sterility is a major hindrance to utiliz-ing the heterosis in indica-japonica hybrids. To isolate a gene Sc conferring the hybrid sterility, the locus was mapped us-ing molecular markers and an F2 population derived from a cross between near isogenic lines. A primary linkage analysis showed that Sc was linked closely with 4 markers on chro-mosome 3, on which the genetic distance between a marker RG227 and Sc was 0.07 cM. Chromosome walking with a rice TAC genomic library was carried out using RG227 as a starting probe, and a contig of ca. 320 kb covering the Sc locus was constructed. Two TAC clones, M45E14 and M90J01 that might cover the Sc locus, were partially se-quenced. By searching the rice sequence databases with se-quences of the TACs and RG227 a japonica rice BAC se-quence, OSJNBb0078P24 was identified. By comparing the TAC and BAC sequences, six new PCR-based markers were developed. With these markers the Sc locus was further mapped to a region of 46 kb. The results suggest that the BAC OSJNBb0078P24 and TAC M45E14 contain the Sc gene. Six ORFs were predicted in the focused 46-kb region.

Genomic polymorphism in consecutive generation rice plants from seeds on board a spaceship and their relationship with space HZE particles

Dry rice seeds(Oryza sativa,subspecies indica)were sandwiched between nuclear track detectors,aboard the Chinese spaceship Shenzhou-3 for seven days.The seeds were recovered and the genomic polymorphism in 201 plants developed from these seeds was studied using random amplified polymorphism DNA analysis.When compared with plants from ground-based control seeds,the genomic polymorphic bands were amplified in 30.2%of the plants from the seeds exposed in space.The results for sequencing and SNP analyses of the polymorphic bands verified the single nucleotide variations in these plants.Genomic poly-morphisms in the consecutive generations of individual plants of the seeds from space were also discovered.Seven seeds receiving hits of HZE(high atomic number and high energy)particles from space were selected for further analyses and variable genomic polymorphisms were detected in all plants that developed from these seeds.Among them,the embryos of three seeds were hit at least once,and mutants with significant changes in agronomic traits were only found in later generations of these seeds.This result implies that the HZE particles of space are effective in inducing the changes of plant genome of inherited phenotypes.