Foxtail millet (Setaria italica) is an important grain crop that is grown in arid regions. Here we sequenced 916 diverse foxtail millet varieties, identified 2.58 million SNPs and used 0.8 million common SNPs to construct a haplotype map of the foxtail millet genome. We classified the foxtail millet varieties into two divergent groups that are strongly correlated with early and late flowering times. We phenotyped the 916 varieties under five different environments and identified 512 loci associated with 47 agronomic traits by genome-wide association studies. We performed a de novo assembly of deeply sequenced genomes of a Setaria viridis accession (the wild progenitor of S. italica) and an S. italica variety and identified complex interspecies and intraspecies variants. We also identified 36 selective sweeps that seem to have occurred during modern breeding. This study provides fundamental resources for genetics research and genetic improvement in foxtail millet.

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Panicle architecture and grain weight, both of which are in uenced by genetic and environmental factors, have signi cant effects on grain yield potential. Here, we used a recombinant inbred line population (RIL) of 333 lines, which were grown in 13 trials with varying environmental conditions, to identify quantitative trait loci (QTL) that control differences in 9 agronomic traits related to panicle architecture and grain yield.We nd that panicle weight, grain weight per panicle, panicle length, panicle diameter, and panicle exsertion length varied across different geographical locations. QTL mapping revealed 159 QTL for nine traits, of these, 34 QTL were identi ed in 2 to 12 environments, suggesting that the genetic control of panicle architecture in foxtail millet is sensitive to photoperiod or other environmental factors. 88 QTL controlling different traits formed 34 co-located QTL clusters, including the triple QTL cluster qPD9.2/qPL9.5/qPEL9.3, the genomic region of which was detected by 23 times in 13 environments. Several candidate genes were identi ed in the genomic intervals of multi-environmental QTL or colocated QTL clusters, including Seita.2G388700, Seita.3G136000, Seita.4G185300, Seita.5G241500, Seita.5G243100, Seita.9G281300, and Seita.9G342700. Among these, Seita.9G342700 was the candidate gene of qPD9.2/qPL9.5/qPEL9.3 QTL cluster, it is homologous to rice OsMADS56, which encodes a putative MADS-box transcription factor that determines inflorescence architecture in rice. These results not only provided a basis for further ne mapping, functional studies and marker-assisted selection of panicle architecture related traits in foxtail millet, but also bene ted comparative genomics of cereal crops.

Foxtail millet [Setaria italica (L.) P. Beauv.] is one of the most important nutritious food crops in China. In August 2020, plants of the foxtail millet cultivar Xiao Huang Miao were found that were wilted and root rot symptoms of 25-75% incidence in a field production area of about 3000 m2 near Tongliao of Inner Mongolia and Chaoyang cities of Liaonning province. The wilted plants showed yellowing, stunting, and the lower stalk became straw colored, softened, with gray-white mould on the surface of the stem nodes. The root system was poorly developed, brown and rotted. Symptomatic roots were surface-disinfested with 70% ethanol for 1 min and in 2% sodium hypochlorite (NaOCl) for 3 min, rinsed with sterilized water three times, and placed on potato dextrose agar (PDA) and incubated at 26ºC for 5 days. Ten pure cultures were obtained from single conidia with an inoculation needle under stereomicroscope. The cultures were transferred to carnation leaf agar (CLA) medium and incubated two weeks in the dark at 26ºC for microscopic observation. Macroconidia had one to four septa (three septa dominated), and were slender and straight with curved apical cell and foot-shaped basal cell, 25.5 - 30.5 × 2.5 - 4.5 μm (n=50). Microconidia were non-septate, oval, and were formed in short chains or false heads on monophialides, 2.5 - 15 × 2.75 - 4.0 μm (n=50). Chlamydospores were singly or in chains, circular or subcircular, 5.25 - 11.5 μm in diameter (n=50). Morphologically, the fungus was identified as Fusarium nygamai Burgess & Trimboli (Klaasen and Nelson,1998; Leslie and Summerell, 2006,). To validate this identification, rDNA internal transcribed spacer (ITS), partial translation elongation factor 1 alpha (TEF-á) gene, and RNA polymerase II second largest subunit (rpb2) of the ten isolates were amplified and sequenced (White et al.1990;O’Donnell K. et al. 2015,2010). Identical sequences were obtained and the sequence of the isolate GZGF23 was submitted to GenBank. BLASTn analysis of the ITS (OL964384), TEF-á (OL961517) and RPB2(ON756204) sequence of isolate GZGF23 revealed 99.86% (MH862671, 557/565bp), 100% (MT011009, 713/1770bp) and 100% (MT010976, 1002/3907bp) sequence similarity respectively with F. nygamai (CBS749.97). Pathogenicity studies were conducted on outdoor potted ground and with the foxtail millet cultivar “Xiao Huang miao”. Five 12-L pots were filled with sterilized field soil mixed with 300ml conidial suspension at 3 × 105 spores/ml. Another five 12-L pots were filled with sterilized field soil mixed with 300ml sterilized water that served as controls. About twenty seeds per pot were surface disinfected in 2% NaOCl for 3 min, and rinsed with sterilized water. The foxtail millet seeds were sown the same day as soil inoculation and 6 plants were left in each pot when seedling emerged. Five weeks after seedling emergence, all inoculated plants exhibited symptoms similar to the syptoms observed in the field but control plants had no symptoms. The same results were obtained when pathogenicity tests were repeated two times in the same manner. Fusarium nygamai was reisolated from inoculated plants and its morphological and molecular characteristics matched the original isolate, but the fungus was not reisolated from control plants. This is the first report of root rot caused by F. nygamai on foxtail millet in China. The disease might bring a threat to foxtail millet production and effective control measures should be identified to reduce losses. References: Klaasen J. A. and Nelson P. E. 1998. Mycopathologia 140: 171–176. Leslie J. F. and Summerell B. A. 2006. Blackwell Publishing, Oxford, U.K. O’Donnell K., et al. 2015. Phytoparasitica 43:583-595. White T. J., et al. 1990. Academic Press, San Diego, CA, pp 315-322. O’Donnell K et al. 2010. J.Clin.Microbiol. 48:3708.

Panicle architecture and grain weight, both of which are influenced by genetic and environmental factors, have significant effects on grain yield potential. Here, we used a recombinant inbred line population (RIL) of 333 lines, which were grown in 13 trials with varying environmental conditions, to identify quantitative trait loci (QTL) that control differences in 9 agronomic traits related to panicle architecture and grain yield. We find that panicle weight, grain weight per panicle, panicle length, panicle diameter, and panicle exsertion length varied across different geographical locations. QTL mapping revealed 159 QTL for nine traits, of these, 34 QTL were identified in 2 to 12 environments, suggesting that the genetic control of panicle architecture in foxtail millet is sensitive to photoperiod or other environmental factors. 88 QTL controlling different traits formed 34 co-located QTL clusters, including the triple QTL cluster qPD9.2/qPL9.5/qPEL9.3, the genomic region of which was detected by 23 times in 13 environments. Several candidate genes were identified in the genomic intervals of multi-environmental QTL or co-located QTL clusters, including Seita.2G388700, Seita.3G136000, Seita.4G185300, Seita.5G241500, Seita.5G243100, Seita.9G281300, and Seita.9G342700. Among these, Seita.9G342700 was the candidate gene of qPD9.2/qPL9.5/qPEL9.3 QTL cluster, it is homologous to rice OsMADS56, which encodes a putative MADS-box transcription factor that determines inflorescence architecture in rice. These results not only provided a basis for further fine mapping, functional studies and marker-assisted selection of panicle architecture related traits in foxtail millet, but also benefited comparative genomics of cereal crops.

Drought significantly affects foxtail millet [Setaria italica (L.) Beauv.] yield, and its adverse effects can be mitigated via genetic improvement to generate drought‐tolerant varieties. This study aimed to screen drought‐tolerant materials and genes in foxtail millet germplasm resources to improve the efficiency of breeding for drought tolerance. A field experiment was conducted in a randomized incomplete block design (α‐lattice design) and repeated thrice with 30 foxtail millet genotypes treated under drought stress or normal water supply (control) for 2 yr. The agronomic traits and drought tolerance coefficient (DC) of each genotype were assessed during the entire growth period. The soil water environment and genotype significantly affected the indices. Moreover, the interaction between genotype and soil water environment significantly affected the growth traits of foxtail millet. A genotype plus genotype × environment interaction (GGE) biplot revealed mixed correlations among the DC indices. Various indices had different effects on the drought tolerance of foxtail millet. The drought tolerance performance and evaluation indices of foxtail millet were ranked according to the distance from the “ideal” drought tolerance genotype and index. The drought tolerance was classified into five categories according to the comprehensive evaluation index (D‐value) cluster analysis. Discriminant analysis showed that the plant height and spike weight could be used as indices for identifying drought tolerance identification in foxtail millet. The GGE biplot results were consistent with the results based on the D‐value. Therefore, multiple agronomic traits combined with D‐value as an evaluation parameter can effectively and accurately identify drought‐tolerant foxtail millet.