[Studies of inheritance and application in rice breeding of the large grain mutant induced in space environment].

The inheritance and utilization of a stable large-grain mutant,selected from the induced generation derived from japonica Nongkeng 58 after space treatment carried by recoverable satellite, were analyzed. The results indicated that the grain volume of the large-grain mutant was quantitative trait controlled by multiple genes. The large-grain mutant had characteristics of slender grain,favorable scent, high apparent grain quality and good compatibility with japonica,and can be used as a valuable resource for improving grain quality. When high yield japonica variety with bad looking quality was used as a recurrent parent to cross with the mutant and a procedure of a limited backcross combined with identification of brown rice quality in segregation generations was applied,some japonica lines with good looking quality were developed. The utility of the limited backcross method for improvement of quantitative traits was discussed.

[Extraction of coumarins from Angelica dahurica by supercritical extraction and GC-MS analysis].

OBJECTIVE: To extract coumarins from Angelica Dahurica by supercritical CO2. METHOD: Six-factor and three-level orthogonal experimental design was used to optimize the SFE conditions as guided by the content of total coumarins in the extract. Constituents of the coumarins were analyzed by GC-MS, and their relative contents were determined by normalization method of areas. RESULT: Total 15 coumarins were separated, the relative contents of oxyimperatorin, imperatorin and isoimperatorin being up to 42.40%, 22.14% and 12.12% respectively. Optimum extraction process was established: 21 MPa as extraction pressure, 50 degrees C as extraction temperature, 3 h as time for extraction, 20 mesh as pulverized degree, 6.5 MPa as separation pressure and 30 degrees C as separation temperature. CONCLUSION: Changes in extraction pressure, temperature, time, pulverized degree and separation pressure affect the extracting results remarkably.

Heavy genetic load associated with the subspecific differentiation of japonica rice (Oryza sativa ssp. japonica L.).

Genetic load in the genome of the model species, rice, was genetically dissected by mapping quantitative trait loci (QTLs) affecting the radiosensitivity of 226 recombinant inbred lines (RILs) to gamma-ray- and spaceflight-induced radiation. The parents and RILs varied considerably in their radiosensitivity to gamma-ray irradiation. A total of 28 QTLs affecting the two index traits, seedling height (SH) and seed fertility (SF), of radiosensitivity were identified. The japonica parent, Lemont, was much more sensitive to gamma-ray irradiation than the indica parent, Teqing, and its alleles at almost all QTLs were associated with increased radiosensitivity, suggesting a much higher genetic load in the japonica genome of rice. Six QTLs (QSh2a, QSh2b, QSh5a, QSh7, QSf3b, and QSf10b) were located in the genomic regions particularly sensitive to radiation and thus might represent possible 'mutation hot spots' in the japonica genome. Detailed characterization of these genomic regions may shed light on the evolution and subspecific differentiation of rice.