The domestication process of cultivated barley in China remains under debate because of the controversial origins of barley. Here, we analyzed transcriptomic and non-targeted metabolic data from 29 accessions together with public resequencing data from 124 accessions to explore the domestication process of cultivated barley in China (Cb-C). These analyses revealed that both Cb-C and Tibetan wild barley (Wb-T) were the descendants of wild barley from the Near East Fertile Crescent (Wb-NE), yielding little support for a local origin of Wb-T. Wb-T was more likely an intermediate in the domestication process from Wb-NE to Cb-C. Wb-T contributed more genetically to Cb-C than Wb-NE, and was domesticated into Cb-C about 3300 years ago. These results together seem to support that Wb-T may be a feralized or hybrid form of cultivated barley from the Near East Fertile Crescent or central Asia. Additionally, the metabolite analysis revealed divergent metabolites of alkaloids and phenylpropanoids and these metabolites were specifically targeted for selection in the evolutionary stages from Wb-NE to Wb-T and from Wb-T to Cb-C. The key missense SNPs in the genes HORVU6Hr1G027650 and HORVU4Hr1G072150 might be responsible for the divergence of metabolites of alkaloids and phenylpropanoids during domestication. Our findings allow for a better understanding of the domestication process of cultivated barley in China.

Soil quality is the basis for the development of sustainable agriculture and may be used for evaluating the sustainability of soil management practices. Soil quality status and integrated soil quality index (SQI) in sampled 97 farmlands distributed in 7 barley agro-ecological areas of China were analyzed by using 13 soil chemical parameters. The results showed six principal components totally explained 72% variability for the 13 parameters and identified 9 parameters (includes pH, NH4+-N, NO3--N, available P, available K, exchangeable Mg, DTPA-Fe, DTPA-Cu and Cl-) with high factor loading values as the minimum data set (MDS) for assessing soil quality. Average soil quality of all farmlands is moderate (SQI = 0.62). The SQI of barley farmlands in 7 agro-ecological areas showed the following order: Inner Mongolia Plateau (0.75 ± 0.02) > Yunnan-Kweichow Plateau (0.72 ± 0.06) > Qinghai-Tibet Plateau (0.63 ± 0.08) > Yangtze Plain (0.62 ± 0.10) > Huanghuai Region (0.58 ± 0.09) > Northeast China Plain (0.56 ± 0.07) > Xinjiang Province (0.54 ± 0.07). Total 29 out of 97 farmlands in 7 areas have low SQI level (< 0.55). Hence, these farmlands require urgent attention for soil quality improvement through modification of the soil parameters in the MDS.