Study On Hybridization And Fertilized Ovule Culture Of Hydrangea Macrophylla

Cross breeding is the main way to cultivate new varieties of Hydrangea macrophylla,but its breeding process is slow due to hybridization barriers.In this study,five H.macrophylla varieties（‘Hatsukohi’,‘Coerulea’,‘Spike’,‘Endless Summer’and‘Otaksa’）and one H.macrophylla var.nomalis variety（‘Taube’）were used as hybrid parents to carry out intraspecific and interspecific hybridization of H.macrophylla.The intra-and interspecific hybridization barriers and the growth laws of hybrid fruits were studied.And the fertilized ovule culture was established,in order to overcome the hybridization barriers and obtain hybrids.The main results are as follows:（1）The growth behavior of pollen tubes was observed,the setting of seeds and fruits as well as seeds germination were counted.It was found that different hybrid combinations had different hybridization barriers.In the intraspecific hybridization of‘Hatsukohi’בCoerulea’,a large number of pollen germinated on the stigma,the pollen tubes grew normally,there was no obvious callose reaction,indicated that there was no pre-fertilization barriers.However embryo abortion occurred in the late stage of seed development.The seeds germination rate was extremely low,and the seedling growth is extremely slow.The results indicated that it was affected by post-fertilization barriers.In the intraspecific hybridization of‘Spike’בEndless summer’,the amount of pollen germination on the stigma was small,the pollen tubes showed abnormal growth behaviors,and a large amount of callose was produced,indicated that there were serious pre-fertilization barriers.A small amount of ovules were successfully fertilized,but did not develop normally,indicated that post-fertilization barriers also existed.In the interspecific hybridization of‘Otaksa’בTaube’,pollen germinated in large numbers in stigma but at a slow rate,a few pollen tubes grew abnormally,but there was no obvious callose reaction.And the fruits setting rate and fruits swelling rate were high.The results indicated that there were pre-fertilization barriers,but less affected by it.In addition,the proportion of full seeds was low,the full seeds germination rate was extremely low,and the seedling growth is extremely slow.The results indicated that there were serious post-fertilization barriers.The longitudinal and transverse diameters of the hybrid fruits were measured,and the exocarp color were observed.The results showed that the growth of the hybrid fruit of‘Hatsukohi’בCoerulea’was a single S-curve,and showed a trend of“slow-fast-slow-stop”.And the growth of the hybrid fruit of‘Otaksa’בTaube’was a single S-curve,showed a trend of“slow-fast-slow”.（2）60-100 d after pollination,ovules were used to observe and culture in vitro.The results showed that after the fruit was treated with 70%ethanol solution for 30 s,the disinfection effect of sodium hypochlorite solution（effective chlorine content 1%）for 10 min was the best.Light and dark alternation(15 h·d^-1 illumination time and 2000-3000 lx illuminance)was conducive to the induction of ovules germination.The optimum medium for inducing ovule germination was MS+1.5 mg·L^-1 6-BA+0.2 mg·L^-1 NAA+1.5 mg·L^-1 GA₃.The induction efficiency of‘Hatsukohi’בCoerulea’increased gradually with the increase of embryo age,and reached the highest at 100 d.The induction efficiency of‘Otaksa’בTaube’increased firstly and then decreased with the increase of embryo age,and reached the highest at 90 d.The induced plantlets had the best growth in MS medium with 0.1 mg·L^-1 NAA.