The Regulation Mechanism Of Plant Growth Regulators On Apomixis Of Kentucky Bluegrass

Abstract: Apomixis breeding, a new filed of breeding science, is considered to be a big push to heterosis. In recent years, more and more scientists have been paying attention to apomixis breeding due to its great potential in agriculture application. However, the actual studies on apomixis still have many problems: mechanisms of apomixis are less understood, while it is known that plant hormone may play an important part in regulating apomixis, unfortunately there is no systematic research has done about plant hormone regulation on apomixis. So our study mainly concentrates on two parts. The first is, comparing the difference between apomixis cultivars, medial cultivars and sexual cultivars of Kentucky bluegrass in term of the dynamic change of auxin level in different developing stages. The second is focused on inductive effect of auxin on poly-embryonic seedlings by spraying plant growth regulators, from which we try to demonstrate the mechanism of plant hormone regulation on apomixis. The principal results are as follows:(1)Changes of plant hormone contents were different in the fringe of three varieties at different developing stages. Content of ABA in apomixis cultivar is significantly higher than that in sexual cultivars at booting stage,two days after heading and anthesis, hower it is much lower at heading stage. Content of ZR in apomixis cultivar is significantly higher than that in sexual cultivar at different developing stages, except half of heading stage and anthesis. The content of ZR/ ABA was significant lower than that in Rite at heading period, while before or after meiosis, the number were much higher than that in Rite. The trend of changes of auxin level in.the middle cultivar is between apomixis cultivar and sexual cultivar, and more similar to the sexual. Content of auxin by ELISA in fringe and immuno-colloidal gold research both suggested: megaspore mother cell and meiosis stages are critical stages of apomixis, and higher ZR content, lower ABA content or higher ZR/ABA in ovule and megaspore may be important regulating factors of apomixis.(2) Different plant growth regulators (except Gibberellic acid (GA3)) had good effects on the inducement of poly-embryo seedlings, but effects were not obvious (except GA3) among different plant growth regulators, however spraying the same plant growth regulator, with different concentrations and times had certain regularities.①6-Benzyladenine(6-BA), daminozide(B9) 2,4-Dichlorophenoxyacetic acid (2,4-D) in medium concentration, the inducement rate of poly-embryo seedlings decreased with increasing spraying times ,in general, spraying one time or 3 times was better than 5 times, but the difference between spraying one time and 3 times was not significant;②With same spraying time, the rate of poly-embryo seedlings with medium concen- tration of 6-BA was significant higher than with lower, higher concentration and CK. 6-BA sprayed at earlier stages was better than that at later stages, but the result was opposite with B9 ; While treatment of 2,4-D was not significant different among lower, medium and higher concentration.③Combination of 6-BA and 2,4-D had good effect at four developing stages, and the regularity was similar to the inducement of single 2,4-D;④100mg/L GA3 sprayed one time were not good at four developing stages and all the treatments were lower than CK except sprayed at heading stage, which the poly-embryo seedlings was 2.00%, a little higher than CK. As for developing stages, the effects of sprayed at heading stage were better than others.(3) It is difficult to identify the induced progeny directly because there are too many chromosomes in kentucky bluegrass, so we utilized the longer diameter and density of leaf stoma to identify them directly. Our results showed: the varation of induced progeny we got were much more than CK, and different progeny were remarkable distinct, this maybe the results of variation of chromosomes.(4) POD isozymes in leaf of induced progeny were remarkable distinct from CK. Our results showed: all plant growth regulators could induced the expres– sion of c,d POD isozymes ,especially c isozymes was much more notable, indicating that activity of POD isozymes was remarkable increased. But the activities of POD isozymes with different plant growth regulators and developing stages were different. These results suggested that POD isozymes of the progeny varied to CK, so it can be used for identifying apomixis materials.