Study On The Cytology Of Special Rice And The Genetic Analysis Of Hybrid Progeny Crossed By Cultivars

Since rice breeding changed from the conventional to the hybrid ,rice production and quality have been greatly increased. But hybrid seeds used only once,seeds producing year by year is time-labour consuming. Most breeders have taken great efforts to explore a way to simplify the process of hybrid breeding and some progresses have also been made . Stability in early generation (F₁ or F₂ progene ) was observed in hybridization in rice recently. The early genotype were fixed and true breeding hybrid can be used many times. So its mechanisms are important to hybrid breeding. Although 300 early stable varities have been selected out, the mechanism of stabilizing in early generation is still unclear. So many unresolved basic researches should be investigated. In this research three results were explored by using early stable rices, 429, 384, 407, 408 and 409. â‘  chromosome behavior during meiosis and embryo sac structure of early stable rices. â‘¡embryo development of pollination process of crossing early stable rice with cultivars . â‘¢ genetic analysis of progenies from the crossing of early stable rice to cultivars . The main results are as following.1. The process as the pollination and embryo sac development of early stable rice crossing cultivars were same as crosses between commons. Some single fertilizations were observed during pollination, but they did not influence the percentage of embryos (75.5%). All these indicated that early stable mechanism may be occurred in proembryo sleeping time. The proembryo that is an active cell during sleeping time supply for matters and information for latter mitosis. It needs some genes iniation, such as closing the mitosis and opening the meiosis.2.The early stable rice PMCs were observed and the results showed that the average pairing figuration was 12 â…¡at diakinsis â…  and 12â…¡at metaphase â… . Every PMCs was normal in other stages. The pollen staining ability was conducted by using 1% I2-KI. The pollen staining ability was 95% according to the PMC's results. There were no difference between early stable rice F₁ and other rices in meosis.3.The research for the embryo sac structure of early stable rice showed that 90.8% embryo sacs were normal and 9.3% were not. And in the latter, multi-eggs,multi-polarnuclei and multi-antipodal cells were observed.4.The process of self pollination and embryo sac development in early stable rice showed that its embryo development must be completed through double fertilization. In order to test if there were other patterns of reprodutive traits, seed setting investigated by excised stanmen . The seed setting was zero , no embryo formed.5.The agronomic traits were constructed in the F2 population. As a result, there was non-significant difference in plant height ,panicle length ,heading date between the F2 population and the CK Shanyou63. The stability population was further verified through microsatellite marker technique. The results showed that all individuals plants were homozygous at all loci at which the bands showed different length between the parents ,and either some bands were identical to male parent, or identical to female parent at each loci. It was concluded that the F2 population was really stable. So early stable traits may be inherited in some circumstances, but relate to its parents.