Characteristics of chloroplast genome of Litsea elongata （Wall. ex Nees）Benth. et Hook. f.

【Objective】Research of Litsea elongata（Wall. ex Nees）Benth. et Hook. f. chloroplast genome possessed essential theoretical and practical significance for species identification，analysis of genetic diversity，and resource protection of Litsea.【Method】The chloroplast genome of L. elongata was sequenced and annotated based on Illumina HiSeq 2000 high-throughput sequencing platform. The chloroplast genome was annotated using GeSeq. The genome structure， gene number，repeats，codon usage bias，phylogenetic development were analyzed by using the bioinformatics softwares such as REPuter，MISA，codonW and IQ-TREE.【Result】The size of chloroplast genome of L. elongata was 154028 bp， with a typical quadripartite structure. The genome contained 126 genes，including 82 protein coding genes，8 rRNA genes，and 36 tRNA genes.Among the annotated genes of chloroplast genome，nine genes contained one intron，three genes contained two introns. None of the remaining genes contained introns. Forty-four proteins were involved in the photosynthetic signal pathway，and 21 proteins constituted large/small subunit ribosome. The chloroplast genome of L. elongata contained 32 long repeats，and 90 simple sequence repeats（SSR）. Among them，the forward repeats（12）and palindrome repeats（12）were the most，followed by the reverse repeats（6）and complementary repeats（2）. 95.56% of the SSR loci were located in the single copy regions［large single copy region（LSC）and small single copy region（SSC）］， and only 4.44% of SSR loci were located in the reverse repeat regions（IR）. The guanine and cytosine（GC）content and synonymous third codons positions（GC3s）of chloroplast protein coding genes of L. elongata were 39.14% and 27.95%， respectively. And the average effective codon number（ENC）was 49.04，indicating that the codon bias of the chloroplast genome was weak. There were 31 codons with relative synonymous codon usage（RSCU）was greater than 1.00，of which 13 ended with A and 16 ended with U（T）. Phylogenetic analysis showed that 14 Litseas pecies were clustered into two clades，and L. elongata gathered together with other ten Litsea species and shared the closest genetic relationship with L. japonica.【Conclusion】The chloroplast genome structure of L. elongata is conservative and prefers codons ending in A or U（T）. The identified SSR loci can be used for species identification and population genetics.