[Directional breeding of high oil content peanut variety Yuhua 9 by in vitro mutagenesis and screening].

Leaf water potential of peanut subjected to drought stress is positively related to the oil content of peanut kernels. The aim of this study was to directly screen the high oil mutants of peanut and create the new peanut varieties using hydroxyproline as water potential regulator. In vitro mutagenesis was carried out with the embryonic leaflets of peanut variety Huayu 20 as explants and pingyangmycin as a mutagen added into the somatic embryo formation medium. The formed somatic embryos were successively transferred to somatic embryo germination and selection medium containing 6 mmol/L hydroxyproline (at -2.079 MPa water potential ) to induce regeneration and directionally screen high oil content mutants. After that, these plantlets were grafted and transplanted to the experimental field and 132 high oil mutants with oil content over 55% were obtained from the offspring of regenerated plants. Finally, among them, the oil contents of 27 lines were higher than 58% and of 2 lines were higher than 60%. A new peanut variety Yuhua 9 with high yield and oil content was bred from the regenerated plant progenies combining the pedigree breeding method. The yield was 14.0% higher than that of the control cultivar in the testing new peanut varieties of Liaoning province, and also it has passed the national registration of non-major crop varieties. Yuhua 9 with an oil content of 61.05%, which was 11.55 percentage points higher than that of the parent Huayu 20, was the peanut cultivar with the highest oil content in the world. The result showed that it was an effective way for directional breeding of high oil peanut varieties by means of the three-step technique including in vitro mutagenesis, directional screening by reducing water potential in medium and pedigree selection of regenerated plant progenies.

[Breeding of peanut variety Yuhua 4 by in vitro mutagenesis].

The embryonic leaflets of peanut (Arachis hypogaea) variety Huayu 20 were used as explants and pingyangmycin as a mutagen to induce somatic embryos. Four weeks after the inoculation, the survived explants were transferred to somatic embryo germination medium containing screening reagent hydroxyproline, and finally 15 regenerated plants were obtained. Pedigree breeding method was used during the following selection breeding, and three lines with significantly increased yield and 23 lines with high oil content were obtained from these mutant offsprings. The line with both high yield and high oil content has passed peanut variety multi-location in Anhui province and was named "Yuhua 4". Its yield was 16.63% higher than that of the control variety Baisha 1016, ranking the first in all the testing varieties. Yuhua 4 showed the characteristics of early maturity, small pod and high oil content. The oil content of kernels was 56.10%, higher than that of original parent Huayu 20 with 49.50% oil content, tested by the Ministry of Agriculture of Oil and Products Quality Supervision, Inspection and Test Center (Wuhan), and the yield was 15% higher than that of Huayu 20. It was concluded that in vitro mutagenesis and target screening was an effective way on creating new germplasm and breeding new variety in peanut.