Fu Yaping

Somaclonal genetics of rice, Oryza sativa L.

SummaryThe inheritance and variations of some traits of more than 2,000 somatic cell derived plants of rice (Oryza sativa L.) were investigated in the second and third generations (T2 and T3) of regenerated plants (somaclones). The percentages of multiploids occurring in somaclones ranged from 0–13.3 in nine varieties (or hybrids) of ‘Hsien’ (indica) group, but no multiploid was found in nine varieties (or hybrid) of ‘Keng’ (japonica) group. A dwarf mutant with the height of only 20 cm was isolated in the T2 of ‘Tai-Zhong-Yu 39’. Genetic analysis indicated that it was controlled by a single recessive gene. The frequencies of chlorophyll mutations probably controlled by cytoplasmic genes decreased gradually with the advance of generations. The variations of five quantitative traits — plant height, grain weight, etc. — in 950 T2 pedigree lines of four varieties were also studied. Only 24.4% of the lines were normal in all the traits studied. Variation frequencies of different traits were from 11.5% to 39.5%. And there was an obvious tendency for the plant height to become shorter, number of productive tillers to increase and 1,000 grain weight to be lighter, whatever the variety studied. Traits were uniform within each of more than 90% of all T2 lines studied. What is more interesting, variations phenotyped in T2 proved to breed true. Causes of somaclonal variations are discussed, as well as their potentials in breeding.

Rapid generation of genetic diversity by multiplex CRISPR/Cas9 genome editing in rice

The clustered regularly interspaced short palindromic repeats (CRISPR)-associated endonuclease 9 (CRISPR/Cas9) system has emerged as a promising technology for specific genome editing in many species. Here we constructed one vector targeting eight agronomic genes in rice using the CRISPR/Cas9 multiplex genome editing system. By subsequent genetic transformation and DNA sequencing, we found that the eight target genes have high mutation efficiencies in the T0 generation. Both heterozygous and homozygous mutations of all editing genes were obtained in T0 plants. In addition, homozygous sextuple, septuple, and octuple mutants were identified. As the abundant genotypes in T0 transgenic plants, various phenotypes related to the editing genes were observed. The findings demonstrate the potential of the CRISPR/Cas9 system for rapid introduction of genetic diversity during crop breeding.

Pedigree Analysis of Photoperiod-thermo Sensitive Genic Male Sterile Rice

A great progress has been made in two-line hybrid rice in China. Up to 2010, a total of 427 two-line hybrid combina- tions (cultivars) had been registered. In recent years, two-line hybrid rice has become an important type in rice production in China. Photoperiod-thermo sensitive genic male sterile (PTGMS) lines are the basis of two-line hybrid rice. In this paper, the rela- tionship of 130 PTGMS lines used as parents of registered hybrid combinations and/or with the right of protection of new varieties was analyzed, and 126 of 130 PTGMS lines that the relationship defined were traced back to their original PTGMS lines as a starting point. The pedigree of the 73 PTGMS lines used for producing hybrid combinations with large scale planting and/or the right of protection of new varieties was analyzed in detail, and the breeding methods of the 126 PTGMS lines were analyzed. The relationship between the photoperiod-thermo response type and the pedigree of the PTGMS lines was discussed. We also pro- posed that selecting the proper PTGMS materials by pedigree analysis is as important as photoperiod and temperature controlling for studying the molecular mechanism of photoperiod-thermo response in PTGMS lines. Open sharing of the PTGMS resources has the great significance for accelerating the breeding of new practical PTGMS lines and minimizing the adverse environmental