Agronomic, Genetic And Physiological Characteristics Of A Rice (Oryza Sativa L) Xantha Mutant

In the production of two line hybrid rice, due to the influence from abnormal weather, the male sterile ability of T/PGMS is always changing, this will cause the drop of varietal purity and negative effect on rice production. Rice leaf- colour mutant can play special role in testing varietal purity.For many years, the reseachers have pay more attention on them.In 2003, reseacher from Anjiang hybrid rice institute found one pale yellowish leaf mutant in the multiplication field of Annong 810S, through many generatoin,the mutant can maitain its character.In 2006,it passed the identification organized by Hunan science and technology department, and it was named as Anong biao 810S.In this paper, the morphological characters, agricultural traits, physiological characteristics and chloroplast ultrastructure of this xantha mutant were studied. Genetic action of the xantha character was analyzed by using the F₁ and F₂ progenies, the mutant gene was mapped preliminarily with microsatellite marker. Furthermore, DNA chip technology was used to analyze gene different expression of this mutant. The results are as follows:1. The observation about leaf colour and strcture of Annong biao 810S showed that the mutant always appeared yellowish from the first leaf of seedling to the whole plant at maturity, independent of cultivation place, season, and year. Therefore, the yellowish seedlings/plants of Annong biao 810S could be easily distinguished from the green ones either as being a minority, e.g., self-pollinated Annong biao 810S seedlings in F₁ populations, or as a majority, e.g., Annong biao 810S seedlings/ plants in seed multiplication field.The leaf structure of Annong biao 810S, compared with that of Annong 810S didn't change significantly. And also, the chloroplast ultrastructure didn't change significantly observed by electronic microscope.2. The testing on Annong biao 810S showed that except yellowish leaf, other characters such as morphological characters, agricultural traits are not changed significantly.3. In comparison with those of Annong 810S, the SPAD value and phtosynthetic pigments of Annong biao 810S were significantly reduced at different stages. At heading stage,the decrease of Chl content in Annong biao 810S was 43.8%,the decrease of Car was 23.0%. During the whole stages, the Chla/Chlb ratio was about 7, the Chla/Chlb ratio was about 4 in Annong 810S.Interestingly, the contents of all photosynthetic pigments and ratio in hybrid Annong biao 810S/D100 were similar to those in Annong 810S/D100.4. The photosynthetic rate, of both Annong biao 810S and Annong 810S, increased with increase of PPFD from 0 to about 2000umol m^-2s^-1. Both Annong biao 810S and Annong 810S had saturation light intensity of around 1200μmolm^-2s^-1. But the photosynthetic rate of Annong biao 810S was consistently higher (5.4-12.8%) than that of Annong 810S when light intensity was above 200μmolm^-2s^-1. Interestingly, the F₁ hybrids of Annong biao 810S/D100 and Annong 810S/D100 had PPFD curves similar to their corresponding GTMS lines, and the photosynthetic rate of Annong biao 810S/D100 was consistently higher (7.2-15.9%) than that of Annong 810S when light intensity was above 200μmolm^-2s^-1.During different stages and different times of a day, the photosynthetic rate of Annong biao 810S was higher than that of Annong 810S.5. The chlorophyll fluorescence kinetic parameters of Annong biao 810S showed that higher maximal photochemical efficiency (Fv/FM), higher excitation energy capture efficiency of photosystem 2 (PS II ) reaction centres (Fv'/Fm'), higher photochemical quenching (qp), higher effective PS II quantum yield (Φ_PSII), and higher non-cyclic electron transport rate (ETR)but lower non-photochemical quenching (qN) than Annong 810S .This tells us the mutant can take use of photo energy more efficiently.6. The super-oxide dismutase (SOD) activities, catalase activities (CAT) and ATPase activities in Annong biao 810S are higher than that of Annong 810S during different stages.7. The combinations of Annong biao 810S crossed with three normal green varieties were used in genetic analysis. The result showed that leaf color of each F₁ progenies represented normal green, and segregation ratio of normal green seedlings to yellowing seedlings fitted the expected ratio of 3:1 in each F₂ population, which suggested that the yellowing trait of Annong biao 810S was controlled by one pair of recessive nuclear gene.The mutation gene was tentatively named pyl (t).8. The results showed that the mutant gene of Annong biao 810S was mapped on the rice chromosome 9. It located between RM288 and RM533. The genetic distances from the target gene to the markers RM288 and RM533 were 4.3 cM and 2.4 cM, respectively.9. DNA chip technology was used to analyze gene different expression of between a natural new rice pale yellow leaf mutant (Annong biao 810S) and its wild type. Results showed that related to chloroplast, more than forty gene expression were up-regulated in mutant, but only one gene expression was up-regulated in wild type, namely SGR gene. The change in SGR gene may cause the yellowing leaf, and this also coincides with the phenomenon which the phenotype was controlled by a recessive mutation in a single nuclear-encoded gene.