ABSTRACT

In order to solve the problem of trace pollen on Polima cytoplasmic male sterility (Pol CMS), male gametocide No.2(MG2) of different concentrations were applied to L17A, one of the Pol CMS lines, at the sporogenic stage, meiosis stage and uninucleate stage. The results showed that the uninucleate stage of L17A were most sensitive and 0.0075-0.01% MG2 could significantly decrease the selfing seed ratio, selfing pod ratio, selfing seeds/plant and pods/plant, the hybridization ratio increased, which was proved that MG2 could stop the normal development of trace pollen at the meiosis stage and uninucleate stage of the pollen mother cell in Pol CMS and consequently reduced and even eliminated trace pollen.

INTRODUCTION

Polima cytoplasmic male sterility is one of the most important cytoplasmic male sterility in rapeseed (Brassica napus L.), but there are a lot of the environment factors to affect the infertility of Pol CMS lines, especially lower or higher temperature will cause normal pollen appearing in the sterile plant and 10%50% sterile plants in the hybrid F1 (T. Fu, 1995; Z. Tang et al, 1995). Chemical Hybridization Agent(CHA) MG2 (CH3AsO3NaH2O) can impede the formation of pollen and suppress normal development of pollen in rice and rapeseed (C. Guang,1997). The study on the suitable stage and concentration of MG2 applied to Pol CMS lines is very important in production of rapeseed hybrid.

MATERIAL AND METHOD

Material and treatment

The Pol CMS line L17A and the dominance no-wax material W1047 were used as the experiment materials, they were sow on 25 September 1996 and 20 September 1997, L17A: W1047 were 4:2, each block had 60 plants. The random block design of time and concentration was hold in 1996 and repeated in 1997. Every year 0.005%0.01% MG2 were applied to L17A at the sporogenous cell stage, meiosis stage and uninucleate stage (the stage was determined by Liuhou Li’s method, 1985), each plant was applied 5ml.

Fertility investigation

30 plants of each block were investigated randomly in the beginning, middle and end blooming stage, the no-pollen, trace pollen and much pollen plants of L17A were count. Before blooming , the main inflorescence and two branched of 15 plants of each block were self crossed, and the total pods/plant, the effective pods/plant and the seeds/plant were counted, from the data the selfing seed ratio, selfing pod ratio and mean seeds/plant were calculated.

Hybrid produce and purity

The block yield had been gotten. The natural seeds of each treatment were sow in next autumn, the seedling with no-wax was considered as the hybrid and the seedling with wax as the selfing seed from sterility line, from which the hybrid ratio was calculated .

RESULTS AND ANALYSIS

Effect of MG2 on blooming stage and fertility

The data of table 1 showed that MG2 could increase the ratio of no pollen sterility plants significantly, and the effect of 0.0075% and 0.001% MG2 applied in meiosis stage and uninucleate stage of pollen mother cell was best. After full blooming stage, the effect of MG2 treatment became unsignificant. After 0.01% treatment in uninucleate stage, the stamen of L17A was shorten , the anther degenerated completely and became triangle, the anther dry and no pollen, the shape was as same as nuclear male sterility, the blooming stage of the treatment postponed 4-5days and some buds were dead.

Table 1 Effect of MG2 on Pol CMS L17A (%)

Influence of MG2 treatment on selfing seed ratio

The results of self cross inflorescences showed time and concentration of treatment could affect significantly selfing seed ratio, selfing pod ratio, the effective pods/plant and the seeds/plant. Among the treatments, one in monocyte pollen had a better effect, especially 0.01% concentration treatment in monocyte made the mean selfing ratio of two year descend to 1.24% and the seeds/plant to 23.3 seeds, these were much lower than CK. The treatment can be used in the production of hybrid.

Effect of MG2 on the yield of cross seed and purity of hybrid

The cross-seed yield of the treatments of MG2 applied in meiosis or monocyte pollen stage was lower 4%13% than CK, but the purity of hybrid increased significantly. The purity of hybrid of the treatment of 0.01% MG2 in monocyte pollen stage could reach the first standard of the hybrid purity, and one of the treatment of 0.0075% MG2 could reach the second standard of the hybrid purity. The results also prove that the suitable stage and concentration of MG2 would make the production of hybrid of Pol. CMS more safe and effective.

Table 2 Effect of MG2 on the yield and purity of hybrid

CONCLUSION

The spring sow in northern area or delayed one month sow in local area often are used to solve the problem of trace pollen of Polima CMS line, but the spring sow in northern area makes the cost of hybrid increase and the seeds can not be used in the same year; delayed one month sow in local area makes the cross-seed yield drop and the purity of hybrid is not assured still. CHA can control trace pollen effectively and increase yield and purity of hybrid using Polima CMS line, this is one of the efficient method in production of hybrid of Polima CMS lines.

REFERENCE

1. Banga S.S. et al 1983 Production of F1 hybrid using ethereal induced male sterility in Indian mustar (B. juncea) Journal of Agricultural Science Camb. Vol. 101:453-455

2. Fu Tingdong , 1995. Breeding and utilization on hybrid rapeseed. Hubei Science and Technology Press, Wuhan, 170-172

3. Guang Chunyun , 1997. Studies of mechnism on male sterility in rapeseed induced by CHA, ACTA Agronomica SINICA Vol.23(5): 513-518

4. Tang Z, J. Li, L. Chen, and X. Zhang, 1997: Temperature influence on sterility of CMS lines and their F₁ in rapeseed (Brassica napus). Journal of Southwest Agricultural University 19, 425-430