Objective Chinese milk vetch (Astragalus sinicus L.), capable of nitrogen fixation to nourish soil, improve soil quality, and support ecological conservation, is a core species in ecological agriculture. Guangdong Province has promoted the "winter cultivation of Chinese milk vetch followed by spring ploughing and deep tillage" model across 30, 000 hm², establishing a "green manure-emission reduction-yield increase" eco-economic system. The development of Chinese milk vetch germplasm resources holds strategic value for sustaining and enhancing the cropland quality improvement system.To analyze the transcriptome and gene expression characteristics of A.sinicus using high-throughput sequencing technology and bioinformatics methods, providing genetic information for resource identification and utilization of A.sinicus.

Method Total RNA was extracted from the roots, stems, leaves, and seeds of A.sinicus cultivar 'Yuelvfei No. 1, , pooled to construct a library, and subjected to high-throughput sequencing. The unigenes of A.sinicus were assembled. The transcriptomic characteristics of 'Yuelvfei No. 1, were analyzed through sequence annotation and alignment.

Result A total of 30 792 unigenes were identified in the transcriptome of 'Yuelvfei No. 1, , with an average length of 1 163 bp and an N50 of 1 946 bp. The unigenes of A.sinicus showed the highest similarity to those of Cicer arietinum (chickpea). Among the unigenes, 20 930 were functionally annotated in databases, including 13 858 annotated in the KEGG database and 17 439 annotated in the GO database, covering cellular anatomical entities, binding, and cellular processes. Flavonoids are the first step in signal exchange between legumes and rhizobia, and this study identified 41 key enzyme genes involved in the flavonoid biosynthesis pathway in A.sinicus. R genes also play a crucial role in the interaction between legumes and rhizobia, and we identified 64 members of the largest class of R genes, NBS genes. Additionally, by aligning A.sinicus unigenes with the plantTFDB database, 367 transcription factors, including MYB, AP2/ERF, WRKY, and bHLH, were identified. MISA analysis of 13 047 unigenes longer than 1 000 bp identified 4 187 SSR loci, for which corresponding primers were designed.

Conclusion The transcriptomic information of A.sinicus cultivar 'Yuelvfei No. 1, provides valuable data support for further exploration of resource identification and genetic improvement in A.sinicus.