Chlorophyll (Chl) content, especially Chl b content, and stomatal conductance (G_s) are key factors that greatly affect net photosynthetic rate (P_n).  Setaria italica, a diploid C₄ panicoid species with a simple genome and high transformation efficiency, has been widely accepted as a model in photosynthesis and drought-tolerance research.  In the current study, Chl content, G_s, and P_n of 48 Setaria mutants induced by ethyl methanesulfonate were characterized.  A total of 24, 34 and 35 mutants had significant variations in Chl content, G_s, and P_n, respectively. Correlation analysis showed that positive correlation exists between increased G_s and increased Pn, and a weak correlation between decreased Chl b content and decreased P_n was also found. Remarkably, two mutants behaved significantly decreased Chl b content but increased P_n when compared that of Yugu 1. Seven mutants behaved significantly decreased G_s but non-decreasing P_n when compared that of Yugu 1.  The current study thus identified various genetic lines, further exploration of which would be beneficial to elucidate the relationship between Chl content, G_s and P_n and the mechanism underlying why C₄ species are efficient at photosynthesis and water saving.

    Kernel color is an important trait for assessing the commercial and nutritional quality of foxtail millet.  Yellow pigment content (YPC) and carotenoid components (lutein and zeaxanthin) of 270 foxtail millet accessions, including 50 landraces and 220 improved cultivars, from four different eco-regions in China were surveyed using spectrophotometry and high performance liquid chromatography methods.  Results indicated that YPC had rich variance, ranging from 1.91 to 28.54 mg kg^–1, with an average value of 17.80 mg kg^–1.  The average YPC of improved cultivars (18.31 mg kg^–1) was significantly higher than that of landraces (15.51 mg kg^–1).  The YPC in cultivars from the Loess Plateau spring sowing region (LPSSR) was the highest (20.59 mg kg^–1), followed by the North China summer sowing region (NCSSR, 18.25 mg kg^–1), the northeast spring sowing region (NSSR, 17.25 mg kg^–1), and the Inner Mongolia Plateau spring sowing region (IMPSSR, 13.92 mg kg^–1).  The variation coefficients of YPC in cultivars from NSSR, LPSSR, and IMPSSR were higher than that from NCSSR.  A similar carotenoid profile was also obtained for 270 foxtail millet cultivars.  Lutein and zeaxanthin accounted for approximately 55–65% of YPC in accessions.  The lutein content was higher than zeaxanthin content in all cultivars.  The ratio of lutein to zeaxanthin ranged from 1.51 to 6.06 with an average of 3.34.  YPC was positively correlated with lutein (r=0.935, P<0.01), zeaxanthin (r=0.808, P<0.01), and growth duration (r=0.488, P<0.01), whereas it was negatively correlated with grain protein (r=−0.332, P<0.01) and 1 000-kernel weight (r=−0.153, P<0.05).  Our study is useful for screening and selecting cultivars with high levels of yellow pigment and for enhancing phytochemical concentrations in breeding programs.

Inter simple sequence repeat (ISSR) analysis was applied to samples of foxtail millet and its wild ancestor and other close relatives of the genus Setaria in order to detect domestication-related geographical structure and phylogenetic relationship of those species. Eighty-one accessions of nine Setaria species that originated from different regions were used in this study. Fourteen out of the 27 ISSR primers screened amplified successfully and a total of 156 markers were scored for all the accessions, with a high level of polymorphism being detected. The dendrogram based on UPGMA cluster analysis showed clear geographic structure among foxtail millet and its wild ancestor green foxtail, which implies that northern China is the domestication center for both the Chinese and European foxtail millet landraces used in this study. This result did not support the hypothesis that China and Europe are independent domestication centers for foxtail millet proposed by several previous studies based on morphological and isozyme data. The dendrogram also clearly classified the Setaria sample used into two groups, a viridis and a pumila groups. The viridis group was composed of S. viridis, S. italica, S. faberii, S. verticillata, S. leucopila, and S. queenslandica, and the pumila group consisted of S. parviflora and S. pumila, which is consistent with the recently proposed hypothesis of multiple origin of Setaria species. The phylogenetic relationships among different species are discussed.