## 4 Discussion
### Genetic Structure Analysis of Korla Fragrant Pear Bud Mutation Materials  
Population genetic diversity analysis is an effective method to research the genetic background of different germplasm resources [73]. GBS genotyping by sequencing is a low-cost, high-throughput genotyping method. GBS technology avoids the shortcomings of traditional genotyping methods and has been widely used in genome-wide association analyses, gene diversity research, and germplasm identification [74]. In the research of the genetic diversity of 96 olive (_Olea europaea_) germplasm resources [75] in the database of the United States Department of Agriculture, it was found that 96 germplasm resources were divided into 7 subpopulations based on GBS sequencing. These seven subpopulations are inconsistent with geographical origin, indicating that they may be caused by regional selection. In the research of genetic diversity of 219 germplasm resources of _Phaseolus vulgaris_[76], it was found that 219 germplasm resources were divided into two gene pools (Mesoamerican gene pool and Andean gene pool). At the same time, it was found that there were several unique SNPs in the two gene pools. In addition, GBS technology was also used to analyze 150 jujube (_Ziziplus jujuba_) germplasms [77]. A total of 4680 SNPs were found, and 150 germplasms were divided into two groups. In our results, it is interesting to note that Korla fragrant pears and budding materials are not divided into two categories by GBS sequencing. This is slightly different from previous research results. We speculate that although the bud mutation materials are obviously expressed in the apparent traits, the degree of variation in the genetic diversity of the population is small, which is not enough to achieve the degree of population evolution, so there is no group differentiation. At the same time, because there is no reference genome for Korla fragrant pear, we selected white pear as the reference genome for comparison. There may be differences between the genomes, so that some SNP loci unique to Korla fragrant pear may not be developed.  
At present, molecular marker technology has been widely used in plant genetic breeding. Among them, SSR molecular marker technology has certain advantages in variety identification and genetic relationship analysis [78]. In the research of the identification of 423 cabbage (_Brassica campestris_ ssp. _chinensis_) varieties [79], 23 markers were finally found by SSR molecular marker technology. These 23 markers can distinguish 418 varieties. In the research of genetic diversity of 97 chrysanthemum (_Chrysanthemum morifolium_) varieties [80], it was found that 97 varieties were successfully divided into three categories by 14 SSR markers. The three categories are small flower varieties, medium flower varieties, and large flower varieties. In addition, 19 SSR markers were used to distinguish 121 tomato (_Solanum Lyopersicum_) germplasm resources [81]. Interestingly, based on the SSR molecular marker method, we successfully distinguished Korla fragrant pear and its mutant materials by 16 pairs of primers after screening. This is similar to the results of previous studies. We speculate that although there is no group differentiation at the GBS level, the two are indeed different at the DNA level. This also confirms that SSR molecular marker technology can be used to distinguish varieties with a close genetic relationship. In addition, we speculated that the gene fragments corresponding to these 16 pairs of primer sequences may be related to the bud mutation traits and may be able to distinguish the bud mutation materials from Korla fragrant pear. However, functional verification needs to be carried out in the future in order to develop and utilize these 16 pairs of primers more accurately.