Updated foxtail millet genome assembly and gene mapping of nine key agronomic traits by resequencing a RIL population.

Foxtail millet (Setaria italica) provides food and fodder in semi-arid regions and infertile land. Resequencing of 184 foxtail millet recombinant inbred lines (RILs) was carried out to aid essential research on foxtail millet improvement. A total 483 414 single nucleotide polymorphisms were determined. Bin maps were constructed based on the RILs' recombination data. Based on the high-density bin map, we updated Zhanggu reference with 416 Mb after adding 16 Mb unanchored scaffolds and Yugu reference with some assembly error correction and 3158 gaps filled. Quantitative trait loci (QTL) mapping of nine agronomic traits was done based on this RIL population, five of which were controlled by a single gene. Meanwhile, two QTLs were found for plant height, and a candidate gene showed 89% identity to the known rice gibberellin-synthesis gene sd1. Three QTLs were found for the trait of heading date. The whole genome resequencing and QTL mapping provided important tools for foxtail millet research and breeding. Resequencing of the RILs could also provide an effective way for high-quality genome assembly and gene identification.

Taxonomic structure and functional association of foxtail millet root microbiome.

The root microbes play pivotal roles in plant productivity, nutrient uptakes, and disease resistance. The root microbial community structure has been extensively investigated by 16S/18S/ITS amplicons and metagenomic sequencing in crops and model plants. However, the functional associations between root microbes and host plant growth are poorly understood. This work investigates the root bacterial community of foxtail millet (Setaria italica) and its potential effects on host plant productivity. We determined the bacterial composition of 2882 samples from foxtail millet rhizoplane, rhizosphere and corresponding bulk soils from 2 well-separated geographic locations by 16S rRNA gene amplicon sequencing. We identified 16 109 operational taxonomic units (OTUs), and defined 187 OTUs as shared rhizoplane core OTUs. The ß-diversity analysis revealed that microhabitat was the major factor shaping foxtail millet root bacterial community, followed by geographic locations. Large-scale association analysis identified the potential beneficial bacteria correlated with plant high productivity. Besides, the functional prediction revealed specific pathways enriched in foxtail millet rhizoplane bacterial community. We systematically described the root bacterial community structure of foxtail millet and found its core rhizoplane bacterial members. Our results demonstrated that host plants enrich specific bacteria and functions in the rhizoplane. The potentially beneficial bacteria may serve as a valuable knowledge foundation for bio-fertilizer development in agriculture.

[Characteristics of accumulated temperature demand and its utilization of maize under different ecological conditions in northeast China].

To understand the accumulated temperature (ACT) demand of maize for its normal maturation among years and regions as well as the use efficiency of local ACT, a group of work-net field experiments was conducted at 55 sites in 28 regions of Northeast China spring maize planting area (40 degrees 07'-48 degrees 08' N) in 2007-2009, taking an eurychoric maize variety Zhengdan 958 as test object. The meteorological conditions in the area had large difference. In the same regions, the active accumulated temperature above 10 degrees C in whole corn growth season (ACT10 for short) demand of Zhengdan 958 for completing its whole growth and development process had little difference among different years (P > 0.1). However, in different regions, this demand differed significantly (P < 0. 001) in the same years, with the largest difference occurred from seedling stage to emergence stage, followed by at post-silking stage, and the least at pre-silking stage. The maturity degree of Zhengdan 958 had significant correlations with local heat conditions, and there was a linear relationship between use efficiency and latitude. Zhengdan 958 could be safely matured in the regions with the ACT10 being more than 3000 degrees C, and had a risk of immaturity in the regions with the ACT10 less than 3000 degrees C. In conclusion, under certain meteorological conditions, the ACT demand of Zhengdan 958 for completing its growth process was relatively stable, and, due to the self physiological adjusting, the ACT10 demand of Zhengdan 958 at its different growth stages showed a significant difference among different regions.