Accumulation of livestock manure-derived heavy metals in the Hexi Corridor oasis agricultural alkaline soil and bioavailability to Chinese cabbage (Brassica pekinensis L.) after 4-year continuous application.

Hexi Corridor is one of the most important base of vegetable producing areas in China. Livestock manure (LM) applied to agricultural field could lead to soil heavy metal (HM) pollution. Previous studies have focused on HM pollution following LM application in acidic polluted soils; however, fewer studies have been conducted in alkaline unpolluted soils. A 4-year field vegetable production experiment was conducted using pig manure (PM) and chicken manure (CM) at five application rates (0, 15, 30, 45, and 60 t ha-1) to elucidate potential risks of HMs in an alkaline unpolluted soil in the Hexi Corridor oasis agricultural area and HM uptake by Chinese cabbage. The results showed that LM application caused a significant build-up of Cu, Zn, Pb, Cd, and Ni content in topsoil by 30.6-99.7%, 11.4-51.7%, 1.4-31.3%, 5.6-44.9%, 14%-40.8%, respectively. The Cd, Cu, Zn could potentially exceed the soil threshold in next 8-65 years after 15-60 t ha-1 LM application. Under LM treatment, the soil DTPA-extractable Cu, Zn, Fe, the acid-extractable fraction of Cu, Zn, Fe, Cd, Ni, and the Oxidable fraction of Cu, Zn, Fe, Mn, Cd, Ni significantly increased, but the DTPA-extractable Pb, Cd, the acid-extractable fraction of Pb, and the reducible fraction of Cd significantly decreased. Cu and Zn could migrate to the deeper soil and relatively increase in DTPA-extracted Cu, Zn were found in 20-40 cm soil depth after LM application. The pH and SOM could influence the bioavailability of HMs in soil. The bioaccumulation factor and transfer factor (TF) values were <1 except Mn (TF > 1). HMs in leaf did not approach the threshold for HM toxicity due to the "dilution effect". Recommend the type of manure was the PM and the annual PM application rate was 30 t ha-1 to ensure a 20-year period of clean production in alkaline unpolluted Fluvo-aqiuc vegetable soils.

Characterization of the complete chloroplast genome of Gypsophila huashanensis Y. W. Tsui & D. Q. Lu, an endemic herb species in China.

Gypsophila huashanensis Y. W. Tsui & D. Q. Lu (Caryophyllaceae) is an endemic herb species to the Qinling Mountains in China. In this study, we characterized its whole plastid genome using the Illumina sequencing platform. The complete plastid genome of G. huashanensis is 152,457 bp in length, including a large single-copy DNA region of 83,476 bp, a small single-copy DNA region of 17,345 bp, and a pair of inverted repeat DNA sequences of 25,818 bp. The genome contains 130 genes comprising 85 protein-coding genes, 37 tRNA genes, and eight rRNA genes. Evolutionary analysis showed that the non-coding regions of Caryophyllaceae exhibit a higher level of divergence than the exon regions. Gene site selection analysis suggested that 11 coding protein genes (accD, atpF, ndhA, ndhB, petB, petD, rpoCl, rpoC2, rps16, ycfl, and ycf2) have some sites under protein sequence evolution. Phylogenetic analysis showed that G. huashanensis is most closely related to the congeneric species G. oldhamiana. These results are very useful for studying phylogenetic evolution and species divergence in the family Caryophyllaceae.

The hybridization origin of the Chinese endemic herb genus Notopterygium (Apiaceae): Evidence from population genomics and ecological niche analysis.

Hybridization is recognized as a major force in species evolution and biodiversity formation, generally leading to the origin and differentiation of new species. Multiple hybridization events cannot easily be reconstructed, yet they offer the potential to study a number of evolutionary processes. Here, we used nuclear expressed sequence tag-simple sequence repeat and large-scale single nucleotide polymorphism variation data, combined with niche analysis, to investigate the putative independent hybridization events in Notopterygium, a group of perennial herb plants endemic to China. Population genomic analysis indicated that the four studied species are genetically well-delimited and that N. forrestii and N. oviforme have originated by hybridization. According to Approximate Bayesian Computation, the best-fit model involved the formation of N. forrestii from the crossing of N. franchetii and N. incisum, with N. forrestii further backcrossing to N. franchetii to form N. oviforme. The niche analyses indicated that niche divergence [likely triggered by the regional climate changes, particularly the intensification of East Asian winter monsoon, and tectonic movements (affecting both Qinghai-Tibetan Plateau and Qinling Mountains)] may have promoted and maintained the reproductive isolation among hybrid species. N. forrestii shows ecological specialization with respect to their parental species, whereas N. oviforme has completely shifted its niche. These results suggested that the climate and environmental factors together triggered the two-step hybridization of the East Asia herb plants. Our study also emphasizes the power of genome-wide SNPs for investigating suspected cases of hybridization, particularly unravelling old hybridization events.