| To investigate the factors influencing the efficiency of haploid induction, the male parent of gynogenesis-inducer TY1 and the female parents of different maize materials were used. And the doubling effeciency was screened using two different kinds of chemical treatment (Hydroxyurea and Colchicine, Hydroxyurea and Oryzalin) with three treatments (immersing seed,germinating seed,coleoptile seed). Our results showed that:1.TY1 had higher average induction rate of 4.16% in the afternoon (17:00-18:00) than that in the morning (10:00-11:00) (2.19%) for hybrid Pioneer 335.2.Five typical hetorotic groups of Reid, TangSP, Lancaster, Lvda Red Cob and PB and five hybrids of Nongda 108, Zhengdan 958, Pioneer 335, Xundan 18 and Yudan 811 were induced by TY1 in Hainan, Zhengzhou and Gansu, respectively. The difference of induction rate was significant among different heterotic groups with the highest average induction rate in Reid (4.96%) and the least in PB (1.63%). Similar sinificant level was also detected in different hybrids. 4.48%, 4.29% of average induction rate manifested in Zhengdan 958 and Xundan 18, but only 2.06% of average induction rate manifested in Nongda 108. In addition, the highest average induction rate was identified in Gansu (4.5% and 5.26%) and the lowest was identified in Zhengzhou (3.08% and 2.99%) not only for different heterotic groups but also for different hybrids when compared the induction rate difference between locations.3.The natural fertility recovery rate of ear was up to 90% which is significantly higher than 12% of fertility recovery rate of tassel.4.Haploid of Zhengan958 was conducted with two different doubling method (Colchicine and HU, Oryzalin and HU) with five concentrations (0.02%, 0.04%, 0.06%, 0.08% ,0.1%) and three treatments (immersing seed,germinating seed,coleoptile seed) for 9 h (maize meristem cell division cycle). The combination of 0.06% colchicine (containing 2% DMSO) and germinating seed was best based on the investigation of survival rate and pollen-shedding rate.5.Based on the above study, the five heterotic groups and the five hybrids were conducted with the treatment combination both in Gansu and in Hainan. After immersed in HU for 6 h (2 h washing) and 0.06% colchicine (containing 2% DMSO) 9 h along with 2 h washing, the germinating seed was sowed in the field. Groups of Reid and Lancaster manifested high average pollen-shielding rate of 58.75% and 56.96%, respectively, implying high doubling efficiency. However, group of PB only had 14.6% of average pollen-shielding rate. Among the different hybrids, Zhengdan 958 and Xundan 18 manifested high doubling efficiency with 59.69% and 59.38% of average pollen-shielding rate, respectively. Only 23.75% of average pollen-shielding rate was found in hybrid of Nongda 108. Strikingly, Gansu should be the best place for doubled haploid development. High average pollen-shielding rate of 47.75% and 53.25% was realized in Gansu than what found in Hainan (39.16% and 41%) for five heterotic groups and five hybrids tested here, respectively. In Gansu the average pollen-shielding rate was 53.25%, which was significantly higher than the average setting rate of 28.25% for the haploid of five hybrids. |
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