SSR Mapping And Resource Utilization Of Yellow-Green Leaf Traits Of Two-line Male Sterile Rice Line Gy157

In the process of producing two-line hybrid rice seeds,the two-line male sterile line is susceptible to varying degrees of fertility recovery if exposed to low temperatures during the temperature-sensitive period,which lowers hybrid purity and reduce the reliability of seed production.Using two-line sterile lines with marker characters is an efficient technique to increase the security of two-line hybrid rice seed production.In this work,the superior two-line male sterile line C815S,one of the parents of gy157S,was used as the control and the two-line male sterile line gy157S,carrying yellow and green leaf markers,was used as the research object.The phenotypic characteristics of gy157S,genetic control and gene mapping of leaf color markers,agronomic traits,fertility characteristics,flowering habits and combining ability were systematically studied,and the aim is to provide a theoretical and practical basis for the innovation of two-line hybrid rice germplasm and the selection of two-line hybrid rice with suitable birth and breeding period,high seed setting rate,good plant and leaf morphology,and strong lodging resistance.The main results are as follows:1.From the seedling stage to the final flowering stage,the color of the leaves of gy157S changed naturally from yellow to yellow-green to light green.The leaves of gy157S exhibit a yellow-green phenotype at 20℃,and the chloroplast development is severely damaged,and at 30°C,the leaves displayed a light green phenotype,with the chloroplast development largely returning to normal.The levels of total chlorophyll,chlorophyll a,chlorophyll b,and carotenoid in gy157S leaves were considerably lower than those of C815S normal green leaves at 20°C and 30°C.2.The separation ratio of normal leaf color and yellow-green plants in both F₂generation segregating populations matched 3:1 in a forward and backward cross test between gy157S and R1638（green leaves）,demonstrating that the yellow-green leaf marker phenotype of gy157S was regulated by a nuclear recessive genes;BSA analysis and linkage analysis identified the gene at a physical distance of 2.4 Mb on chromosome 3 between RM15678 and RM15824.Functional analysis,sequencing,and q RT-PCR results of candidate genes revealed that the ferredoxin（Os Fd C2）-encoding gene,Os R498G0306815500.01,had a single nucleotide polymorphism（SNP）mutation in exon 7 that changed the coding amino acid from T to G,tyrosine（Y）to aspartic acid（D）,which may be the site causing the yellow-green leaf mutation phenotype.It is suggested that the gene regulating the yellow-green leaf phenotype of gy157S may be allelic with Os Fd C2（Os R498G0306815500.01）.3.Staged sowing studies revealed that gy157S had a steady and continuous sterility period of 15 days,99.97-100%pollen abortion,and 100.00%self-fertility under Guiyang ecological circumstances.Single plants and spikes of the gy157S species took 15.9 and 10.2 days,respectively,to finish the flowering stage.From 12:00-13:30,there was a clear peak in blossoming.Under normal circumstances,the blooming rate was 60.9%before noon,the glume opening angle was 34.0°,and the stigma exsertion rate was 65.0%.4.30 hybrid combinations were matched with 6 male sterile lines and 5 restorer lines,such as gy157S.From the comprehensive yield of the six male sterile lines,the combination 21G2556 and gy157S performed the best,and the general combining ability effect value of single plant yield was larger,13.0 and 8.1,respectively,and there was no significant difference between the two;21G2556 and gy157S combinations 21G2556/Meixiangzhan-2,gy157S/Guiyefeng,21G2556/Yuehe silk seedling,gy157S/Meixiangzhan-2,gy157S/Yuehe silk seedling（arranged from large to small）had positive specific combining ability effect values for single plant yield,and ranked in the top ten among all hybrid combinations;Among the 9 agronomic traits observed,the genetic law of each trait is jointly affected by additive effect and non-additive effect,and the additive effect is the main one.This study suggests that Os Fd C2（Os R498G0306815500.01）may be a candidate gene that causes phenotypic changes in gy157S.Temperature can affect the leaf color phenotype of gy157S,mainly due to changes in photosynthetic pigment content caused by the development of chloroplasts.The phenotypic changes in leaf color of gy157S also ensure that timely screening and auxiliary impurity removal can be carried out based on the leaf color at the seedling stage during seed production,effectively reducing the risk of hybrid seed production and the cost of impurity removal.And the later turning green is also beneficial for better photosynthesis of the leaves.As a two-line male sterile line,it has the following advantages:excellent agronomic traits,stable sterility The flowering habit is good and the outcrossing dynamics are good:the general combining ability and special combining ability relative effects of the gy157S trait are good,but there are also shortcomings such as high indusive necking rate that need further improvement.