Genetic Control of Germination Ability under Cold Stress in Rice

An F9 recombinant inbred lines （RIL） population, derived from a cross between IR28 （Oryza sativa L. spp. indica） and Daguandao （O. sativa L. spp. japonica）, was used to construct a molecular linkage map and to identify germination ability including the traits of imbibition rate, germination rate, germination index, root length, shoot length and seed vigor at 14℃ for 23 d. A composite interval mapping approach was applied to conduct genetic analysis for germination ability. The frequency distributions of the germination ability traits under the cold stress in the RIL population showed continuous segregation, suggesting they were quantitative traits controlled by several genes. A total of seven QTLs were identified on chromosomes 4 6 and 9, including two for imbibition rate （qIR-6, qIR-9）, one for germination rate （qGR-4）, two for germination index （qGI-4-1, qGI-4-2） and two for root length （qRL-4-1, qRL-4-2）. There were no detected QTLs controlling shoot length and seed vigor. The phenotypic variance explained by a single QTL ranged from 9.1% to 37.0%, and two major QTLs, qlR-6 and qGI-4-2, accounted for over 30% of the phenotypic variance. The expressions of QTLs were developmentally regulated and growth stage-specific. Most of the QTLs observed here were located in the regions similar to the QTLs for rice cold tolerance reported previously, indicating that these QTLs were reliable. However, qRL-4-2 is not reported before.

Methods for Improving Hybrid Seed-setting Rate of a Potato Cultivar Linshu 17

[Objective] This study aimed to explore methods for improving hybrid seed-setting rate of a potato cultivar Linshu 17. [Method] L0527-4 was taken as male parent and Linshu 17 was taken as female parent to breed a new potato cul- tivar, so as to take advantage of the excellent characters of Linshu 17. [Result] The optimum pollination time of Linshu 17 was 10：00-12：00 am or after 04：00 pm. Spraying 10 mg/L of 2, 4-D, 50 mg/L of gibberellin or 20 mg/L of 6-BA ＋ 50 mg/L of gibberellin once every 7 days since the 3^rd day after hybridization all could im- prove the hybrid seed-setting rate of Linshu 17. [Conclusion] The hybrid seed-setting rate-improving effect of 2, 4-D sprayed on the 3^rd d after hybridization was best for Linshu 17. This study will provide technical references for other varieties to improve the hybrid seed-setting rate.

Effects of desiccation of seeds in nine species with morphophysiological dormancy on germination and embryo growth

Aims In species with morphophysiological seed dormancy(MPD),little is known about the effects of desiccation of imbibed seeds on embryo growth and germination.We studied seed responses to dehydration in nine species with different levels of MPD.Methods For each species,a control test was conducted by keeping seeds permanently hydrated and exposed to the optimal stratification-incubation sequenee to promote embryo growth.Simultaneously,tests were run in which seed stratification was interrupted for 1 month by desiccation at room temperature.Important Findings In Clematis vitalba and Ribes alpinum,with non deep simple MPD,desiccation affected neither embryo growth nor seed viability,but the desiccation led to a decrease of germinative ability in R.alpinum by 16%.The seeds of Narcissus pseudonarcissus subsp.munozii-garmendiae,with deep simple epicotyl MPD,tolerated desiccation in different embryo growth stages,but their germinative ability decreased slightly.The response of species with complex levels of MPD to desiccation was more variable:Delphinium fissum subsp.sordidum,with intermediate complex MPD,and Anthriscus sylvestris and Meum athamanticum,both with deep complex MPD,tolerated desiccation.In contrast,Ribes uva-crispa with nondeep complex MPD,Lonicera pyrenaica with intermediate complex MPD and Chaerophyllum aureum with deep complex MPD,had diminished germination ability by desiccation.Although seeds of the species with simple levels of MPD tolerated desiccation,those of some species with complex levels were also highly tolerant.Thus,desiccation did not induce secondary dormancy in late embryo growth stages.The desiccation tolerance of imbibed seeds of most of the nine species may show their adaptability to climate change in the Mediterranean region.