The complete chloroplast genome of Cuscuta australis R. Br. (Convolvulaceae) and its phylogenetic implication.

The genus Cuscuta (Convolvulaceae) is an annual parasitic twining herb. There are about 200 species in this genus, which are widely distributed in tropical and subtropical areas. Cuscuta is mainly parasitic on crops bringing significant losses to the production of agriculture. Furthermore, dried seeds of C. chinensis and C. australis are used as a Chinese traditional herbal medicine. Despite the importance of Cuscuta species, it is difficult to distinguish these plants by the naked eye. Moreover, plastid sequence information available for Cuscuta species is limited. In this study, the complete chloroplast (cp) genome sequence of C. australis was determined using next-generation sequencing. The entire cp genome was determined to be 85,263 bp in length. It contained large single-copy (LSC) and small single-copy (SSC) regions of 50,384 and 6727 bp, respectively, which were separated by a pair of 14,076 bp inverted repeat (IR) regions. The genome contained 98 genes, including 61 protein-coding genes, 29 tRNA genes, and 4 rRNA genes. The overall GC content of the genome is 37.8%. A phylogenetic tree reconstructed by 26 chloroplast genomes reveals that C. australis is most related with Cuscuta pentagona in Convolvulaceae, with bootstrap support values of 100%.

[Characteristics of paddy field nitrogen leakage and runoff in rice-duck farming system].

A field experiment was conducted to study the characteristics of paddy field nitrogen (N) leakage and runoff under rice-duck farming (MRD), conventional farming (MR), and conventional farming with flooding (CK). Comparing with that under MR, the paddy field under MRD had a notable decrease of N (especially NO3- -N) concentration in its leaked liquid; but this concentration was tended to be increased, compared with that under CK. After 7-9 days of fertilization, the NH4+ -N and NO3- -N concentrations in paddy field surface water were higher under MRD than under MR. However, owing to the no draining and the higher band, the paddy field under MRD had a notable reduction of drainage, resulting in a marked decrease of N runoff than that under MR. Comparing with MR, the paddy field under MRD had an addition of nitrogen supply from duck dung, a reduction of N leakage and runoff, a lesser application of chemical nitrogen fertilizer, and more nitrogen uptake by rice plant. Both the reduction of N input and that of N output in rice-duck farming system were nearly equal in quantity.