| Grain number per panicle is one of the key factors that constitute rice yield.Spikelets degeneration caused grain number decrease,seriously affect rice yield.Leaves are the main sites for photosynthesis in plants,and 90% to 95% of the yield of rice comes from photosynthesis in leave chloroplasts.Therefore,the genetic analysis and localization of spikelet degradation and leaf color mutation genes in rice will provide a basis for further gene cloning and function research,which can help to analyze the molecular mechanism of the spikelet degradation and leaf color mutation in rice,and provide the basis for rice genetic improvement.In this study,Using the top spikelet degradation line(spd7)since Changhui 121 family and a natural mutation of white striped leaf(wlp6)mutant as experimental materials,Phenotypic and agronomic characters,genetic pattern,gene mapping and candidate gene of spikelet degeneration and leaf color mutants were analysis.The main results are as follows:Part 1Genetic analysis and fine location of spikelet degradation genes in RiceAt the heading stage,the top spikelets of the spd7 plants degenerated,abortion and Shedding after maturity.The spikelet degradation rate of spd7 in Sanya is 18.55%,Nanchang middle season is 8.66% and late season 14.00%,the difference of the degradation rate between the two regions and the different seasons showed that the gene was greatly influenced by the environment.Some agronomic traits of spd7 and Changhui121 were investigated in Nanchang.It was found that the number of branches and grains per panicle of spd7 was significantly lower than that of Changhui 121,but there was no significant difference in growth period,plant height,effective panicle and 1000 grain weight,but the panicle length and seed setting rate of spd7 were slightly lower than Changhui 121.The genetic behavior of spd7 was analyzed by F1 and F2 populations obtained from spd7 and Changhui 121.It was found that the trait was controlled by the dominant nuclear gene.The spikelet degradation rate of 791 single plants in the F2 population was investigated in Nanchang,there were 214 individuals without degradation and 577 individuals are degraded,Chi square test(chi 2=1.67 < 3.84)accords with the separation ratio of 3:1.The gene was located in the seventh chromosome long arm and In Del marker M-6～M-8,physical distance was 115 kb by using 600 degraded individuals and 100 normal individuals in the F2 population of spd7 backcross Changhui 121.20 candidate genes were annotated in the interval,and the relative expression of spd7 and Changhui 121 young ears were analyzed by q PCR.It was found that the relative expression of LOC＿Os07g47320 was significantly down regulated in spd7.Sequencing found that the base of 725～726 site replacement from GC to AG in the coding region of the gene,resulted in the change from arginine to glutamine.Therefore,it is speculated that LOC＿Os07g47320 is the candidate gene of Spd7,but the function of the gene is unknown.Spd7 is a new spikelet degenerate gene,because there are no reports of spikelet degeneration related genes in this area.Part 2Identification and gene mapping of white stripe leave mutantThe wild and mutant seeds were seeded in the early,middle and late 3 seasons in Nanchang.The mutant plant’s leaves and leaf sheaths were white stripes in the 3 season,from first leaves to mature.The mutant glumes and branches of early and late season were albino,the panicle color have no difference with wild type in middle season.Investigated some of the agronomic traits in middle and late season,It was found that the plant height,number of effective tillering and number of spikes of wlp6 were significantly lower than the wild type in 2 season,In late season the seed setting rate and 1000 grain weight of wlp6 also significantly lower.The chlorophyll content of leaves was measured at 3 leaf stage,tiller stage and heading stage,results showed that wlp6 was significantly lower than wild type.The chlorophyll content of spikelet of wlp6 was significantly lower than the wild type in early and late season,no significant difference in middle.The mesophyll cells of heading stage were observed by electron microscopy,in wlp6 the number of chloroplasts decreased,the volume became smaller,and there was no obvious lamellar structure.Temperature and light sensitivity experiments showed that the mutant was insensitive to light intensity.Leaf color affected by temperature and sunshine duration,and chlorophyll content increased with the temperature and sunshine duration increase,but the effect of temperature on leaf color is greater than that of sunshine.WLP6 was located on the sixth chromosome short arm by 616 F2 populations obtained from wlp6/02428,In Del marker R-7～R-8,and the physical distance 137 kb,21 candidate genes were predicted in this interval.Through candidate genes analysis and sequencing,we found that LOC＿Os06g14620 encodes a small chain of RNA reductase,142 nd and 158 th base of the coding region was replaced T with C,and the base A was inserted at the 288 th position.The insertion of the base leads to termination of the gene translation.Therefore,it is speculated that LOC＿Os06g14620 is the candidate gene for WLP6.LOC＿Os06g14620 is the candidate gene of the white stripe gene St1 which has been cloned,WLP6 is the allele of St1,but the mutation sites and phenotypes are different. |
