The Photosynthetic Characteristics And Inheritance Of Leaf Color Mutant In Rice (Oryza Sativa L.)

A mutant named Biao 810S was founded in thermo-sensitive genie male sterile rice 810S populations in Huaihua Vocational and Technical College.It has yellow green leaf,gets the normal growth and has the same leaf structure with 810S.In this research,compared with 810S,the photosynthetic characteristics as well as the ultrastructure and protein of chloroplast of this mutant were investigated,and a systematical analysis of agronomy attributes was also carried out.We have also mapped the causative gene of this mutant using SSR markers and discussed the principle of screening sterile strains from segregated populations of hybrid progenies.The main results are as follows:1,There were significant difference in the total photosynthetic pigment content between the mutant Biao 810S and wild type 810S. Compared with 810S,the total photosynthetic pigment content of Biao 810S was aabout 50%lower;which was the main cause of the yellow green leaf.2,The spikelet numbers,stigma exsertion rate and flowering time of Biao 810S were same as that of 810S.There were no significant difference of the agronomic traits between the the cross combination which came from the maintainers D100 and R96-1 and the combination from 810S.3,The photosynthetic rate of Biao810S was higher than 810S under strong light and lower under weak light.Biao 810S had no light saturation point and'Midday depression' phenomenon in some scope of intensity(2400μmol·m^-2·s^-1) while 810S got the light saturation point when the intensity was 1500μmol·m^-2·s^-1.Compared with 810S,the CO₂ compensate point of Biao 810S was lower while the stomatal conductance was highly increased.4,The Fv'/Fm',ΦPSâ…¡and qP of Biao 810S were significantly higher than that of 810S,which indicated that the light energy conversion and primary light capture of photosystemâ…¡of Biao 810S were much higher than 810S.It also suggested that the quantum yield of PSâ…¡which was used to absorbing light and transporting photosynthetic electron was bigger and non cyclic electron transport was higher.At the same time,the NPQ of Biao 810S was much lower,which means that the portion of light intensity being dissipated in form of heat energy from PSâ…¡was little.5,The activity of PEPCase and NADP-ME of Biao 810S were significantly higher than 810S,which were respectively 189.94%and 178.48%of that of 810S.6,The separate ratio of leaf color in the F₂ populations which came from Biao 810S and some other varieties was 3:1,through which the yellow green leaf mutant had been defined to be controlled genetically by single recessive gene.Further linkage analysis of rice SSR markers in F₂ populations(Biao 810S/Nipponbare) were carried out,from which two SSR markers-RM3838 and 18457 were obtained.Both RM3838 and 18457 were tightly linked to yellow green leaf mutant gene with genetic distances of 4.2 cM and 10.6cM,respectively.According to the position of this two markers,we located the mutant gene on chromosome 5.7,The hybrid offspring populations of Biao 810S/Nipponbare has separated in to groups by the different leaf colors,and the total photosynthetic pigment content changed from 0.9 to 1.70 mg.g^-1FW,so the photosynthetic characteristics and agronomic traits were also differentiated in to 3 groups:the group which was the best green and had highest photosynthetic pigment content got the photosynthetic rate at about 28.38μmolCO₂·m^-2·s^-1,the group which was the best yellow and had lowest photosynthetic pigment content got the photosynthetic rate at about 21.27μmolCO₂·m^-2·s^-1,while the photosynthetic rate of the group which was the intermediate type was the biggest,with the maximum value 30.43μmolCO₂·m^-2·s^-1.All the analysis indicated that the main cause of the yellow green leaf was the decline of the chlorophyll content.The photosynthetic rate of Biao810S was lower than 810S because of the fewer Chlorophyll Content and decreases in capacity of chloroplasts capturing lights of Biao 810S.But under strong light Biao810S got no light saturation point,this physiological characteristics of high photosynthetic efficiency might be related to high electron transport rate on the photosynthetic membrane, higher PEPC activity and increased stomatal conductance.This physiological characteristics might make up for the deficiency of chlorophyll so that the plant could grow normally,and this also the physiological basis for the breeding usage of this yellow green leaf.Although the yellow green leaf mutant had been defined to be controlled genetically by single recessive gene,here were differences in the yellow-green degree of leaf colour and photosynthetic rate of hybrid offsprings populations of Biao 810S/Nipponbare.As a result the plants which had obvious yellow green leaf color(but not to yellow),high photosynthetic rate and larger growth increment were considered to be the breeding object of sterile line.