Melia azedarach L. is a native tree species that can be used in a comprehensive way and is widely distributed in all provinces south of the Yellow River in China. Genetic diversity analysis of different M. azedarach germplasm sources is an important basic work for the selection, evaluation, and genetic improvement of M. azedarach germplasm resources. In this study, 100 pairs of SSR primers were designed and synthesized based on M. azedarach transcriptome data, and 16 pairs of reliable SSR primers were finally selected. The developed primers were used to analyze the genetic diversity of M. azedarach from 15 sources in 10 provinces in East, Central, and South China. The results showed that the frequency of the M. azedarach transcriptome SSR loci was high, and the distribution density was high. There were 15 sources of M. azedarach genetic diversity at a moderate level, and genetic variation was mainly present within the sources. The present study further enriches the existing SSR marker database of the M. azedarach family and can provide a reference for genetic diversity analysis and molecularly assisted breeding of M. azedarach plants at the genomic level.

Hibiscus syriacus, a woody ornamental plant with great economic value, is vulnerable to salinity. Hence, its cultivation in saline areas is severely restricted. Although grafting H. syriacus onto H. hamabo rootstock can greatly improve H. syriacus’s salt resistance, the photosynthetic response of H. syriacus to grafting and salt stress remains largely unknown. To address this question, self-rooted (Hs), self-grafted (Hs/Hs), and H. hamabo-grafted (Hs/Hh) H. syriacus were exposed to 0 or 300 mM NaCl. Salt significantly reduced the net and maximum photosynthetic rates, chlorophyll content, and maximum (Fv/Fm) and actual (ΦPSII) photochemical quantum yield of photosystem II (PSII), as well as the apparent electron transport rate, in Hs and Hs/Hs. However, these reductions were largely alleviated when H. syriacus was grafted onto H. hamabo. In line with the changes in the chlorophyll fluorescence parameters, the expression of genes encoding subunits of PSII and PSI in Hs/Hh was higher than that in Hs and Hs/Hs under saline conditions. Moreover, H. hamabo rootstock grafting upregulated the genes involved in the Calvin–Benson–Bassham cycle in H. syriacus under salt conditions. These results indicate that grafting can ameliorate the inhibition of salinity on the photosynthetic capacity of H. syriacus, mainly resulting from alleviated limitations on photosynthetic pigments, photochemical efficiency, and the Calvin–Benson–Bassham cycle.