| Oryza.officinalis Wall.ex Watt originated from Yunnan and South China,is a valuable natural resource.Previous studies have shown that medicinal wild rice has accumulated a large number of favorable genes lacking in cultivated rice during long-term natural selection and adaptation to the environment.However,wild rice is difficult to be cultivated and utilized directly because of its low yield,poor plant type and strong grain drop.Therefore,in rice breeding,it is expected to cultivate new rice varieties with high quality by integrating the favorable characters of medicinal wild rice into the excellent production varieties.Interspecific hybridization between cultivated rice and wild rice is one of the main ways to realize the transfer of favorable genes from wild rice to cultivated rice,difficulty in reproduction is a major limiting factor for gene exc hange and hybrid utilization.Chromosome doubling can help overcome the problem of distant hybridization incompatibility.In this study,the tissue culture system of hybrids between O.officinalis and O.sativa was established and the method of polyploid ind uction was explored.The mechanism of hybrid sterility was found by cytological observation,it provided a new way to preserve genetic diversity and create new germplasm resources,and provided practical experience and theoretical basis for further utilization of favorable genes in Oryza officinalis and rice breeding.The main findings are as follows:（1）Cytological study on anther and embryo sacsterility of interspecific hybrids of O.officinalis and O.sativa.The distant hybridization between the medicinal wild rice and the cultivated rice was incompatible,and there was reproductive isolation.There were many abnormalities in the development of anther and embryo sac in hybrids.During pollen development,pollen mother cells degenerate,cells divide unequally,daughter cells divide unsynchronously,forming trisomes,abnormal giant tetrads and so on.The highest percentage of abnormal mature pollens was the typical abortive pollens（81.94%）.The embryo sac degenerated,egg apparatus degenerated,antipodal cell mass degenerated,egg apparatus degenerated,female reproductive unit degenerated and small embryo sac degenerated.The largest percentage of embryo sac degenerated was 46.48%.There are some problems in meiosis chromosome pairing.Anther and embryo sac showed very low fertility,pollen fertility was lower than embryo sac,the normal rate was only 0.72%,the normal rate of embryo sac was 9.86%.The induced polyploidy is expected to overcome the fecundity of the hybrid to some extent.（2）The tissue culture system of interspecific hybrids of O.officinalis and O.sativa was established.The suitable medium for Callus induction was N6+2.0 mg·L-1 2,4-D,the induction rate was 80.56%,N6+2.0 mg·L-12,4-D+0.2 mg·L-16-BA was propitious to callus multiplication culture,the multiplication rate was 1036.43%in 26 days,MS+2.0mg·L-16-BA+0.2mg·L-1NAA was the most suitable differentiation medium,the differentiation rate was 75.00%,the emergence rate was 28.97%;2.0 mg·L-1IAA or NAA+0.2-0.5 mg·L-16-BA+0.5 g·L-1AC were suitable for rooting and seedling culture.（3）In vitro induction of allotetraploid in interspecific hybrids of O.officinalis and O.sativa.The results showed that the seedling rate of interspecific hybrid callus induced by co-culture was higher than that induced by soaking,and the seedling rate of interspecific hybrid callus induced by co-culture was higher than that by Colchicine,when the concentration of Colchicine was 400 mg·L-1 or 500 mg·L-1,the seedling yield was 13.33%and 7.41%respectively after 3 days of co-culture.Most of the abnormal seedlings died in the culture period,which showed the effect of Colchicine treatment on Callus differentiation and seedling formation.Three polyploidy strains were detected by Flow cytometry ploidy.In conclusion,the abnormal development of pollen and embryo SAC is the cytological cause of high sterility in the interspecific hybrid of Oryza Officinalis.The tissue culture system of the interspecific hybrid was successfully established and three hybrid plants were obtained. |
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