Screening And Application Of Restorer Line Changhui 70 Mutants

Rice（Oryza sativa L.）is one of the main crops in China and even in the world.More than 65%of the population in China relies on rice as their staple food.With the continuous progress and deepening of research on rice genetics and breeding,exploring more favorable genes is of great significance for both basic and applied research in rice.Building a saturated mutant library is one of the most convenient and effective methods for discovering favorable genes,as well as exploring new genes,and enriching rice breeding materials.In this study,9 EMS solutions of different concentrations were used to induce the seeds of Changhui 70.Through analysis of agronomic and quality traits,a number of different types of mutants were selected,some of which can be used as genetic research materials,and some of them can be directly used as excellent strains for application and breeding.The main results are as follows:1.By analyzing the germination rate and seedling rate of Changhui 70 under nine different mutagenic concentrations of 0.4%,0.6%,0.8%,1.0%,1.2%,1.4%,1.6%,1.8%,and 2.0%,it was found that the germination rate and seedling rate were 56.0%and 15.4%at 0.6%concentration,and 33.8%and 10.4%at 0.8%concentration.When Changhui 70was exposed to these two concentrations,there was a high mutation rate.The seedling formation rate is high at concentrations lower than 0.6%,but the mutation rate is low.The seedling formation rate is extremely low at concentrations higher than 1.0%.Finally,the optimal EMS mutation concentration for Changhui 70 should be between 0.6-0.8%.2.297 mutant seedlings were obtained in M₁,and ultimately 284 individual plants survived.The seeds on the main spike were harvested,forming an M₂ population consisting of 284 plant lines.Various types of mutants were selected based on phenotypic differences in traits.Among them,71 plant lines have leaf variations,including albinism,yellowing,spots,long leaves,short leaves,broad leaves,narrow leaves,leaf drapes,and leaf curls;There are 57 plant type variations,including multiple tillers,fewer tillers,large tillering angle,high stem,and dwarfing;There are 63 plant lines with physiological variations,including premature senescence,early heading,late heading,sterility,and semi sterility;There are 4 lines with quality mutations,including chalkiness and variation in grain length to width ratio.The highest proportion of variation was found in fertility and heading stage mutations.Many mutants have mutations in more than one trait.For example,individual plants with generally lighter leaf color have the characteristics of short plant height,late heading date,and small spike shape;Most of the higher plants have a late heading date and poor seed setting rate.This indicates that there is a possibility of one cause has multiple effects on the mutants,and some mutants provide genetic material for the exploration of new genes.In the mutant population,two mutants with shorter flag leaf lengths and earlier heading dates than the wild type were selected,and other comprehensive traits,especially yield traits,did not significantly change.The mutant has a sword leaf length of 26.9 cm and 30.4 cm,respectively,which is 10.3 cm and 6.8 cm shorter than the wild type Changhui 70,respectively.It is an ideal sword leaf length and is named M70-1 and M70-2,respectively;The other two plants,named M70-3 and M70-4,have a heading date 5 and 11 days earlier than that of the wild type,respectively,which may become excellent breeding materials.3.Using 48 pairs of standard SSR molecular markers to distinguish rice characteristics,it was determined that there were no differences between M70-1,M70-2,M70-3,and M70-4 mutant individuals and Changhui 70,indicating that mutants are derived from Changhui 70.Through gene chip analysis,it was determined that the excellent alleles contained in the wild type itself were present in the mutants,and no mutations occurred.It includes genes related to yield（Gn1a,q GW8,Sd1）,genes related to rice quality（GS3,ALK,Chalk5）,genes related to nitrogen absorption（TOND1,NRT1.1B）,genes related to salt tolerance（SKC1）,genes related to fertility restoration（Rf2）,genes related to wide compatibility（S5）,and genes related to disease resistance（STV11,Pi5,Pia,Pid2,Pid3,Pita,Xa21）.4.The wild-type Changhui 70 and 4 mutants were tested by crossing with the male sterile line C6S.The hybrid offspring of Changhui 70 was the variety Chun Liang youchang 70.The main agronomic traits of the hybrid offspring were analyzed.The results showed that C6S/M70-1 significantly shortened the flag leaf length compared to the control Chun Liangyouchang 70,and significantly decreased the yield per plant compared to the control.The length of the flag leaf of C6S/M70-2 was significantly shorter than that of the control Chun Liangyouchang 70,and there was no significant difference in yield per plant compared to the control.The heading date of C6S/M70-3was 2 days earlier than that of the control Chun Liangyouchang 70,and there was no significant difference in yield per plant compared to the control.The heading date of C6S/M70-4 was 5 days earlier than that of Chun Liangyouchang 70,and the yield per plant decreased significantly compared to Chun Liangyouchang 70.There was no significant difference in other traits,indicating that the mutants had a good utilization prospect.