Plastic film mulching has been widely used to increase maize yield in the semiarid area of China.  However, whether long-term plastic film mulching is conducive to agricultural sustainability in this region remains controversial.  A field experiment was initiated in 2013 with five different film mulching methods: (i) control method, flat planting without mulching (CK), (ii) flat planting with half film mulching (P), (iii) film mulching on ridges and planting in narrow furrows (S), (iv) full film mulching on double ridges (D), and (v) film mulching on ridges and planting in wide furrows (R).  The effects on soil organic carbon (SOC) content, storage, and fractions, and on the carbon management index (CMI) were evaluated after nine consecutive years of plastic film mulching.  The results showed that long-term plastic film mulching generally maintained the initial SOC level.  Compared with no mulching, plastic film mulching increased the average crop yield, biomass yield, and root biomass by 48.38, 35.06, and 37.32%, respectively, which led to the improvement of SOC sequestration.  Specifically, plastic film mulching significantly improved CMI, and increased the SOC content by 13.59%, SOC storage by 7.47% and easily oxidizable organic carbon (EOC) by 13.78% on average, but it reduced the other labile fractions.  SOC sequestration and CMI were improved by refining the plastic film mulching methods.  The S treatment had the best effect among the four mulching methods, so it can be used as a reasonable film mulching method for sustainable agricultural development in the semiarid area.

Mitochondria influence plant growth, fertility, and adaptation. Sugarcane (Saccharum hybrids) is the most important sugar and energy crop worldwide, and S. spontaneum and S. arundinaceum are excellent parental germplasm. However, few studies have been conducted on the mitochondrial genomes of sugarcane and related species. In this study, the mitogenomes of one S. arundinaceum, one S. spontaneum, and five sugarcane cultivars were assembled. The results showed that the sizes of these mitogenomes, encoding 33 protein-coding genes (PCGs), were between 445,578 and 533,662 bp, with a GC content of 43.43%-43.82%. The major structures of S. arundinaceum comprised three small rings, S. spontaneum had one ring and one linear structure, and sugarcane had two rings; there were multiple potential conformations due to repeat-mediated recombination. Furthermore, we developed an intron marker SAnad4i3 that can distinguish these species. Between 540 and 581 and from C to U RNA editing sites were identified in the PCGs, with six RNA editing sites were associated with the creation of start or stop codons in S. arundinaceum, and five sites each in S. spontaneum and the sugarcane hybrids were observed. Notably, 30-37 fragments homologous to chloroplast DNA were identified, with the highest number found in S. spontaneum. During evolution, these mitogenomes may have undergone multiple genomic reorganization and gene transfer events and lost eight PCGs. Collectively, this study reveals the genetic diversity and complexity of the Saccharum complex by providing a scientific basis for further germplasm identification and evolutionary research.