Selection And Multi-point Evaluation Of Good Seeds From SP7-SP8 Generation Of Aerially Mutagenized Cassia Obtusicassia L.

The dried mature seeds of cassia(Cassia obtusifolia L.)are the traditional dual-use Chinese herb cassia seeds,which are grown in a wide area and have medicinal values such as laxative,liver-clearing and eye-opening.However,because there is no specific high-quality variety of cassia and perfect harvesting method,the quality of cassia herbs sold in the market varies.Therefore,our group attempted to breed new varieties of high quality cassia by aerospace mutagenesis breeding to enrich cassia germplasm resources.In this study,we used SP7-SP8(7th to 8th generation of aerospace mutagenesis)cassia,with a total of 10 mutant lines.The effects of different levels of drought stress on the germination and seedling stages of the mutagenized cassia seeds were investigated,and the DNA transcribed spacer region(ITS)sequences of different mutagenized lines were analyzed.The main findings were as follows.1.In this study,the phenological periods of mutagenized cassia and common cassia were observed and recorded for two consecutive years,and the results showed that the phenological periods of the mutagenized strains were approximately the same as those of common cassia,except for the earlier phenological period of strain 7.7 could be used as an early-maturing strain for the next variety selection.2.The mutagenic strains were classified according to the characteristics of agronomic traits as:Thick-stemmed type(No.1): the stem thickness value of No.1 is significantly greater than other mutagenized strains,up to 16.19 mm,and is 17.6% higher than that of common cassia.High-stemmed type(No.4): No.4 had the highest plant height of 155.82 cm,which was significantly higher than other cassia mutant strains and common cassia.High-yielding type(No.6): No.6 had the highest yield per plant,reaching about 190 g,significantly higher than that of common cassia.Multi-branching type(No.7): the number of branches of each strain was from largest to smallest: No.7,No.10,No.6,No.4,No.5,No.8,No.2,No.3,No.1,No.9.The number of branches of No.7 was significantly higher than that of other mutant strains and common cassia,reaching about 35 branches.Based on the comprehensive evaluation of each agronomic trait index based on the affiliation function method,the average affiliation function values of the agronomic traits of each mutant strain and common cassia in descending order were: No.6,No.5,No.7,No.8,No.1,No.4,No.10,No.9,No.3,No.2,and ck,and the best performance of each agronomic trait was No.6.3.There were differences in orange-yellow cassia and rhubarb phenol contents in Shangluo area at different harvesting periods.The highest peak of orange-yellow castorein and rhubarb phenol content in different harvesting periods showed a single-peak curve,in which the highest peak of orange-yellow castorein content appeared around the 30 th day after the yellow color of castoreum pods,and the highest peak of rhubarb phenol content appeared around the 40 th day after the yellow color of castoreum pods.Therefore,it is suggested that the best harvesting period of cassia pods is from the 30 th to the 40 th day after the yellow color of the pods,and the content of orange cassia and rhubarb phenol in the seeds of cassia is higher in this interval.4.There were differences in the contents of the six anthraquinones among the mutagenic strains.Among the mutagenized strains,strains 4,5 and 6 had the highest content of orange-yellow cassia with more than 0.1%;strains 1 and 3 had more than 0.18% of rhubarb phenol,significantly higher than other strains and common cassia;strain 3 had significantly higher content of rhubarbin than other mutagenized strains and common cassia,reaching 0.023%;strain 6 had the highest content of rhubarbin methyl ether,reaching The highest rhodoxanthin content of strain 3 and 6 was above 0.04%,which was significantly higher than other strains and common cassia;the highest rhodoxanthin content of strains 2and 7 was above 0.005%,which was significantly higher than other strains and common cassia.Based on the comprehensive evaluation of the content of the six anthraquinones in different strains by the affiliation function method,the values of the affiliation functions of each strain were,in descending order: No.6,No.3,No.1,No.4,No.5,No.2,No.10,No.7,ck,No.9,and No.8.5.The degree of tolerance to drought stress varied among the deciduous mutant strains.Under drought stress simulated by different concentrations of PEG-6000,the germination rate,germination potential,germination index,root length and shoot length of seeds of each mutant strain showed a decreasing trend with increasing stress.the activities of stress-resistant enzymes(SOD,POD,CAT,MDA)of No.6,No.3,No.1,No.5 and common cassia were increased.The results showed that the SOD activity increased and then decreased with the increase of PEG-6000 concentration,and the SOD enzyme activity of the mutagenic cassia was higher than that of the common cassia;the MDA content increased with the increase of the stress,and the MDA content of the mutagenic cassia was significantly lower than that of the common cassia.The differences in ITS sequence lengths of 6.21 samples were mainly in the ITS1 region,with ITS1 sequence lengths ranging from 233 to 254 bp and GC contents ranging from 59% to 67%;the homology rates between mutagenic and common cassia and congeners ranged from 80% to 90%,while the homology rates between mutagenic and common cassia and congeners in the database ranged from 98.8% to The homology rates between mutagenic cassia and common cassia and the same plants in the database ranged from 98.8% to 100%;mutagenic cassia were clustered separately in the evolutionary tree,with No.2,No.3,No.5,No.8,and common cassia in the same branch as KT279730,KY968917,and MN244678,No.4 and No.7 in the same branch,and No.1,No.6,and No.9 in the same branch.In terms of traits,the mutagenized strains showed greater differences from other mutagenized strains in terms of stem thickness value of No.1,highest plant height of No.4,single plant yield of No.6,and number of branches of No.7;the combined performance of No.6,No.3,No.1,and No.4 was better than other mutagenized strains in terms of anthraquinone content;in terms of tolerance to drought,No.6,No.3,No.1,and No.5showed better drought resistance than other In the evolutionary tree,the different mutant strains were clustered separately and in different branches.