Comparison of Biological and Genetic Characteristics between Two Most Common Broad-Leaved Weeds in Paddy Fields: Ammannia arenaria and A. multiflora (Lythraceae)

The Complete Chloroplast Genome and the Phylogenetic Analysis of Fimbristylis littoralis (Cyperaceae) Collected in Cherry Blossom Nursery

Fimbristylis littoralis, also known as globe fringerush, is one of the most troublesome annual Cyperaceae weeds in dryland fields and nurseries in the Yangtze Plain, Middle and Lower in China. The chloroplast (cp) genome of F. littoralis, and even this genus, has not been studied yet. In this study, the feature of the cp genome of F. littoralis and its phylogenetic relationships has been reported for the first time. It exhibited a typical circular tetramerous structure, with 86 protein-encoding genes. There were 149 simple sequence repeats (SSRs) and 1932 long repeats (LRs) detected. The IR expansion and contraction revealed the uniqueness of F. littoralis because there is a special cross-boundary gene, rps3, located at the LSC/IRb junction. Phylogenetic and divergence time dating analysis showed the close relationship between F. littoralis and the genus Cyperus, as well as many evolutionary directions of Cyperaceae family plants. The most recommended chemical method for removing this weed from nurseries is to spray 13 g ai ha-1 (the amount of active ingredient applied per hectare) of saflufenacil before emergence or 7.5 g ai ha-1 of halosulfuron-methyl after emergence. In conclusion, this study was the first to report the complete cp genome of a plant in the genus Fimbristylis. Our findings also provided valuable biological information for studying the phylogenetic relationships and evolution among the family Cyperaceae.

Complete chloroplast genome and comparison of herbicides toxicity on Aeschynomene indica (Leguminosae) in upland direct-seeding paddy field

BACKGROUND

Indian jointvetch (Aeschynomene indica) is a common and pernicious weed found in the upland direct-seeding rice fields in the lower reaches of the Yangtze River in China. However, there are few reports on the degree of harm, genetic characteristics, and management methods of this weed. The purpose of this study is to clarify the harm of Indian jointvetch to upland direct-seeding rice, analyze the genetic characteristics of this weed based on chloroplast genomics and identify its related species, and screen herbicides that are effective in managing this weed in upland direct-seeding rice fields.

RESULTS

In a field investigation in upland direct-seeding rice paddies in Shanghai and Jiangsu, we determined that the plant height and maximum lateral distance of Indian jointvetch reached approximately 134.2 cm and 57.9 cm, respectively. With Indian jointvetch present at a density of 4/m2 and 8/m2, the yield of rice decreased by approximately 50% and 70%, respectively. We further obtained the first assembly of the complete chloroplast (cp.) genome sequence of Indian jointvetch (163,613 bp). There were 161 simple sequence repeats, 166 long repeats, and 83 protein-encoding genes. The phylogenetic tree and inverted repeat region expansion and contraction analysis based on cp. genomes demonstrated that species with closer affinity to A. indica included Glycine soja, Glycine max, and Sesbania cannabina. Moreover, a total of 3281, 3840, and 3838 single nucleotide polymorphisms were detected in the coding sequence regions of the cp. genomes of S. cannabina voucher IBSC, G. soja, and G. max compared with the A. indica sequence, respectively. A greenhouse pot experiment indicated that two pre-emergence herbicides, saflufenacil and oxyfluorfen, and two post-emergence herbicides, florpyrauxifen-benzyl and penoxsulam, can more effectively manage Indian jointvetch than other common herbicides in paddy fields. The combination of these two types of herbicides is recommended for managing Indian jointvetch throughout the entire growth period of upland direct-seeding rice.

CONCLUSIONS

This study provides molecular resources for future research focusing on the identification of the infrageneric taxa, phylogenetic resolution, and biodiversity of Leguminosae plants, along with recommendations for reliable management methods to control Indian jointvetch.