Identification of S-RNase genotype and analysis of its origin and evolutionary patterns in Malus plants

Identification of the S genotype of Malus plants will greatly promote the discovery of new genes, the cultivation and production of apple, the breeding of new varieties, and the origin and evolution of self -incompatibility in Malus plants. In this experiment, 88 Malus germplasm resources, such as Aihuahong, Xishuhaitang, and Reguanzi, were used as materials. Seven gene -specific primer combinations were used in the genotype identification. PCR amplification using leaf DNA produced a single S-RNase gene fragment in all materials. The results revealed that 70 of the identified materials obtained a complete S-RNase genotype, while only one S-RNase gene was found in 18 of them. Through homology comparison and analysis, 13 S-RNase genotypes were obtained: S 1 S 2 (Aihuahong, etc.), S 1 S 28 (Xixian Haitang, etc.), S 1 S 51 (Hebei Pingdinghaitang), S 1 S 3 (Xiangyangcun Daguo, etc.), S 2 S 3 (Zhaiyehaitang, etc.), S 3 S 51 (Xishan 1), S 3 S 28 (Huangselihaerde, etc.), S 2 S 28 (Honghaitang, etc.), S 4 S 28 (Bo 11), S 7 S 28 (Jiuquan Shaguo), S 10 S e (Dongchengguan 13), S 10 S 21 (Dongxiangjiao) and S e S 51 (Xiongyue Haitang). Simultaneously, the frequency of the S gene in the tested materials was analyzed. The findings revealed that different S genes had varying frequencies in Malus resources, as well as varying frequencies between intraspecific and interspecific. S 3 had the highest frequency of 68.18%, followed by S 1 (42.04%). In addition, the phylogenetic tree and origin evolution analysis revealed that the S gene differentiation was completed prior to the formation of various apple species, that cultivated species also evolved new S genes, and that the S 50 gene is the oldest S allele in Malus plants. The S 1 , S 29 , and S 33 genes in apple -cultivated species, on the other hand, may have originated in M. sieversii , M. hupehensis , and M. kansuensis , respectively. In addition to M. sieversii , M. kansuensis and M. sikkimensis may have also played a role in the origin and evolution of some Chinese apples.