Morphological Observation, Genetic Analysis And Molecular Tagging Of Genes For Two Floral Organ Mutants From Rice (O.Sativa L)

The acquisition and research on the mutants related to reproductive development play an important role in uncovering the function and interaction of genes in reproductive process, especially in floral development. Research on rice reproductive mechanism is significant both in theory and in human agriculture.We obtained two floral organ mutants from rice hybrid progency. Floral malformed structures and their morphogenesis were observed by anatomical microscopy, paraffin slices and scanning electron microscopy. Furthermore, genetic analysis of mutant traits, molecular mapping of related genes and allelic analysis of several floral mutants have also been carried out. Main results as below: 1. About the rice long hull mutant(1) Identification of floral morphology, anatomical structure and pollen fertility: The long hull floral organ mutant in rice(Oryza sativa L.) was firstly discovered in the hybrid progeny of wild rice variety(<9. nivara Sharma et Shastry) and cultivar (O. sativa subsp. indica Kato) rice. Compared with normal rice spikelets, paleas and lemmas of mutant florets which exhibit open, leafy hulls become thinner and longer. Usually palea is longer than lemma. In some florets, there are a few lemma/palea-like structures. Most of florets are made up of 3-5 stamens (90%), and 41.14% of them consist of two pistils, 58.86% one pistil. Besides, the percentage of 6~10 stamens in the same floret which has two or more pistils is about 10%. The number of ovarys (1-4) is changeable and 1-5 stigmas are on the same ovary. Stamens and pistils from 11.5% florets are fused and bulged tissues are observed in 34.5% florets. Sometimes two ovules in the same floret are seen with paraffin slices. Another obvious character is low seed settling rate (17.13%). Pollen fertility rate is 63.23%.(2) Observaton by SEM: Mutant phenotype appears apparent at the beginning of pistil and stamen primordium differentation. Usually, the differentation of stamen and pistil primordia is irregular, and development of stamens in the same floret is at the different stage.(3) Genetic analysis: Lh mutant was crossed with Jodan, Maylielle, Shuhui527, and Clustered spikelets mutant respectively. Floral phenotype of FI progency is the same as theirnormal parents. Investigation for F2 population shows that the segregation of normal plants and mutant plants fits a ratio of 3:1. Thus the mutant traits are controlled by single recessive gene which is tentatively designated as Ih (long hull).(4) Morlecular mapping of Ih gene: The F2 population, cl/lh mutant, was used to screen molecular marker linked with Ih gene. Subsequently, the gene is mapped on the short arm of chr.3 with a distance of 7.9cM between the gene and RM157.(5) Conclusion: A few lemma/palea-like structure and partly homeotic con-version of stamens into pistils are very similar to the phenotype for loss of B functional gen es in arabidopsis. Simultaneously, a few lemma/palea-like structure, reduction of stam ens and two ovules in the same ovary show that Ih gene also influences floral organnumber. 2. About the rice malformed hull mutant(1) ^identification of floral morphology, anatomical structure and pollen fertility: The malformed hull floral organ mutant in rice(Oryza saliva L.) is from the hybrid progeny of Japonica and Indica rice. Paleas of the mutant florets which exhibit open are partly degenerated. In some florets, there are a few lemma/palea-like structures. Most of florets are made up of 3-5 stamens (81.25%) and 1 pistil. Whereas the number of 6-9 stamens florets with two pistils is fewer (18.75%). The percentage for two florets on the same rachilla is 30.43%. Another obvious character for the mutant is comparatively lower seed settling rate (50.91%). Pollen fertility rate is 68.25%.(2) Observaton by SEM: Different appearance is intuitive at the beginning of stamen and pistil primordium differentiation. A normal floret consists of six stamens among which one stamen in middle of lemma primordium develops behind. In mutant florets, the numbe...