Effect of Brassinolide on Soil Microorganisms in Millet Field Polluted by Tribenuron-Methyl.

Tribenuron-methyl is used to control broad-leaved weeds and has a promising application prospect in millet fields. However, its negative impact on soil ecology cannot be ignored. Brassinosteroids have been widely reported to enhance plant resistance to stress, but information on brassinosteroids for the remediation of pesticide-contaminated soils is limited. Under field conditions, brassinosteroids were applied to explore their effects on the residues of tribenuron-methyl, soil enzyme activity, soil microbiol community, and millet yield. After applying brassinosteroids according to the dose of 150 mL hm-2, the degradation rate of tribenuron-methyl accelerated. Brassinolide stimulated the activities of catalase and dehydrogenase, while the activities of sucrase and alkaline phosphatase were inhibited. The results of high-throughput sequencing showed that brassinosteroids inhibited the growth of Verrucomicrobia, Ascomycota, and Mortierellomycota and promoted the abundance of cyanobacteria. Additionally, brassinosteroids could also significantly increase the diversity index and change the community structure of soil bacteria and fungi. Further, the predicted function results indicated that brassinosteroids changed some metabolic-related ecological functions of the soil. We also found that brassinolide could increase millet yields by 2.4% and 13.6%. This study provides a theoretical basis for the safe use of tribenuron-methyl in millet fields and a new idea for the treatment of pesticide residues in soil.

Genome-Wide Identification and Expression Profiling of Cytochrome P450 Monooxygenase Superfamily in Foxtail Millet.

The cytochrome P450 monooxygenases (CYP450) are the largest enzyme family in plant metabolism and widely involved in the biosynthesis of primary and secondary metabolites. Foxtail millet (Setaria italica (L.) P. Beauv) can respond to abiotic stress through a highly complex polygene regulatory network, in which the SiCYP450 family is also involved. Although the CYP450 superfamily has been systematically studied in a few species, the research on the CYP450 superfamily in foxtail millet has not been completed. In this study, three hundred and thirty-one SiCYP450 genes were identified in the foxtail millet genome by bioinformatics methods, which were divided into four groups, including forty-six subgroups. One hundred and sixteen genes were distributed in thirty-three tandem duplicated gene clusters. Chromosome mapping showed that SiCYP450 was distributed on seven chromosomes. In the SiCYP450 family of foxtail millet, 20 conserved motifs were identified. Cis-acting elements in the promoter region of SiCYP450 genes showed that hormone response elements were found in all SiCYP450 genes. Of the three hundred and thirty-one SiCYP450 genes, nine genes were colinear with the Arabidopsis thaliana genes. Two hundred SiCYP450 genes were colinear with the Setaria viridis genes, including two hundred and forty-five gene duplication events. The expression profiles of SiCYP450 genes in different organs and developmental stages showed that SiCYP450 was preferentially expressed in specific tissues, and many tissue-specific genes were identified, such as SiCYP75B6, SiCYP96A7, SiCYP71A55, SiCYP71A61, and SiCYP71A62 in the root, SiCYP78A1 and SiCYP94D9 in leaves, and SiCYP78A6 in the ear. The RT-PCR data showed that SiCYP450 could respond to abiotic stresses, ABA, and herbicides in foxtail millet. Among them, the expression levels of SiCYP709B4, SiCYP71A11, SiCYP71A14, SiCYP78A1, SiCYP94C3, and SiCYP94C4 were significantly increased under the treatment of mesotrione, florasulam, nicosulfuron, fluroxypyr, and sethoxydim, indicating that the same gene might respond to multiple herbicides. The results of this study will help reveal the biological functions of the SiCYP450 family in development regulation and stress response and provide a basis for molecular breeding of foxtail millet.

Stronger mutualistic interactions with arbuscular mycorrhizal fungi help Asteraceae invaders outcompete the phylogenetically related natives.

Mutualistic interactions with arbuscular mycorrhizal fungi (AMF) greatly affect the outcome of plant-plant competition, especially for invasive plants competing against native plants. We examined the effects of AMF on the competition between invasive Asteraceae plants and the phylogenetically related native plants. We compared the performance of seven invasive Asteraceae plants from different genera with that of their phylogenetically related native counterparts in response to AMF in monocultures and mixed cultures. We investigated how interactions with AMF impact the competition between Asteraceae relatives. Total biomass increased with AMF colonization in both invasive and native plants. Arbuscular mycorrhizal fungi improved the competitiveness of invasive plants, but decreased that of native plants. Competition increased the shoot nitrogen, phosphorus and root myristic acid concentrations and relative expression of fatty acid transporter genes (RiFAT1 and RiFAT2) in AMF-colonized invasive plants, but decreased those in AMF-colonized native plants. Structural equation models indicated that the presence of AMF increased the uptake of phosphorus, but not nitrogen, by invasive plants, which probably provided more myristic acids to symbiotic AMF in return. These results suggest that invasive Asteraceae plants have greater mutualistic interactions with AMF than their phylogenetically related native counterparts, potentially contributing to invasion success.

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The development of new herbicides based on allelochemicals is a potential strategy of weed control in arable field. Pyrone, a novel derivative of tricin, has significant inhibitory effects on weeds. Its safety for crops, especially for millet that are sensitive to commercial herbicides, is still poorly understood. In this study, germination test and pot experiments were conducted to evaluate the safety of pyrone on 20 millet varieties, compared with 2,4-D. The results showed that, except that Jinfen109 was sensitive to high concentration 2,4-D, both pyrone and 2,4-D had no effect on the germination rates of other varieties. Results of the pot experiment showed that pyrone treatment significantly increased the chlorophyll content of millet by 9.0%-67.9%, which was the greatest for Jigu 42. Pyrone treatment did not affect maximal photochemical efficiency, potential photochemical activity, actual photochemical efficiency, and non-photochemical quenching coefficient. On the contrary, 2,4-D significantly inhibited the fluorescence parameters of millet varieties. Pyrone treatment increased the activities of superoxide dismutase, peroxidase and catalase in leaves of Dunza16, Jigu 39, Jigu 41 and Jingu 28, with the magnitude of enhancement being higher than 2,4-D. The results indicated that the allelochemical derivative pyrone is highly safe to the growth of millet seedlings and has the potential to be a new herbicide to millet field.

An investigation into the beneficial effects and molecular mechanisms of humic acid on foxtail millet under drought conditions.

The aim of this study was to determine the effects and underlying molecular mechanisms of humic acid (HA) on foxtail millet (Setaria italica Beauv.) under drought conditions. The rainless climate of the Shanxi Province (37°42'N, 112°58'E) in China provides a natural simulation of drought conditions. Two foxtail millet cultivars, Jingu21 and Zhangza10, were cultivated in Shanxi for two consecutive years (2017-2018) based on a split-plot design. Plant growth, grain quality, and mineral elements were analyzed in foxtail millet treated with HA (50, 100, 200, 300, and 400 mg L-1) and those treated with clear water. Transcriptome sequencing followed by bioinformatics analysis was performed on plants in the normal control (CK), drought treatment (D), and drought + HA treatment (DHA) groups. Results were verified using real-time quantitative PCR (RT-qPCR). HA at a concentration of 100-200 mg L-1 caused a significant increase in the yield of foxtail millet and had a positive effect on dry weight and root-shoot ratio. HA also significantly increased P, Fe, Cu, Zn, and Mg content in grains. Moreover, a total of 1098 and 409 differentially expressed genes (DEGs) were identified in group D vs. CK and D vs. DHA, respectively. A protein-protein interaction network and two modules were constructed based on DEGs (such as SETIT_016654mg) between groups D and DHA. These DEGs were mainly enriched in the metabolic pathway. In conclusion, HA (100 mg L-1) was found to promote the growth of foxtail millet under drought conditions. Furthermore, SETIT_016654mg may play a role in the effect of HA on foxtail millet via control of the metabolic pathway. This study lays the foundation for research into the molecular mechanisms that underlie the alleviating effects of HA on foxtail millet under drought conditions.

Humic acid improves the physiological and photosynthetic characteristics of millet seedlings under drought stress.

We aimed to determine whether humic acid (HA) can alleviate the injury of millet caused by drought and its potential mechanism. Millet seeds (Jingu 21 and Zhangza 10) were soaked in different concentrations of HA (0, 50, 10, 200, and 300 mg L-1) for 12 h. The physiological and photosynthetic characteristics of millet seedlings, including growth parameters, osmotic regulators, antioxidase activity, photosynthesis, chlorophyll fluorescence, and P700 parameters, were determined before and after drought stress. HA significantly promoted the growth of millet seedlings under drought stress. Pretreatment with 100 mg L-1 or 200 mg L-1 HA significantly increased free proline, soluble protein, and activity of the antioxidant enzyme system (superoxide dismutase, peroxidase, and catalase) in both Zhangza 10 and Jingu 21. The accumulation of reactive oxygen species ([Formula: see text] and H2O2) was reduced in HA treatments compared with that of the control (P < .05). Moreover, HA (100 mg L-1) significantly increased net photosynthetic rate, stomatal conductance, effective quantum yield of photosystem II, relative photosynthetic electron transfer rate of photosystem II, and photochemical quenching. HA also reduced intercellular CO2 concentration and non-photochemical quenching. Furthermore, 200 mg L-1 HA significantly increased the maximum P700, effective quantum yield of photosystem I, and relative photosynthetic electron transfer rate of photosystem I in Zhangza 10 and decreased non-photochemical energy dissipation in Jingu 21 and Zhangza 10 under drought stress. HA promoted the growth of millet seedlings under drought stress by promoting the osmotic adjustment ability and antioxidant capacity of seedlings and increased photosynthesis.

Comprehensive evaluation of fluroxypyr herbicide on physiological parameters of spring hybrid millet.

Foxtail millet (Setaria italic L.) is an important food and fodder crop that is cultivated worldwide. Quantifying the effects of herbicides on foxtail millet is critical for safe herbicide application. In this study, we analyzed the effects of different fluroxypyr dosages on the growth parameters and physiological parametric of foxtail millet, that is, peroxidation characteristics, photosynthetic characteristics, and endogenous hormone production, by using multivariate statistical analysis. Indicators were screened via Fisher discriminant analysis, and the growth parameters, peroxidation characteristics, photosynthesis characteristics and endogenous hormones of foxtail millet at different fluroxypyr dosages were comprehensively evaluated by principal component analysis. On the basis of the results of principal component analysis, the cumulative contribution rate of the first two principal component factors was 93.72%. The first principal component, which explained 59.23% of total variance, was selected to represent the photosynthetic characteristics and endogenous hormones of foxtail millet. The second principal component, which explained 34.49% of total variance, represented the growth parameters of foxtail millet. According to the principal component analysis, the indexes were simplified into comprehensive index Z, and the mathematical model of comprehensive index Z was set as F = 0.592Z 1 + 0.345Z 2. The results showed that the comprehensive evaluation score of fluroxypyr at moderate concentrations was higher than at high concentrations. Consequently, one L (active ingredient, ai) ha-1 fluroxypyr exerted minimal effects on growth parameters, oxidase activity, photosynthetic activity, and endogenous hormones, and had highest value of comprehensive evaluation, which had efficient and safe benefits in foxtail millet field.

Spraying Brassinolide improves Sigma Broad tolerance in foxtail millet (Setaria italica L.) through modulation of antioxidant activity and photosynthetic capacity.

To explore the role of Brassinolide (BR) in improving the tolerance of Sigma Broad in foxtail millet (Setaria italica L.), effects of 0.1 mg/L of BR foliar application 24 h before 3.37 g/ha of Sigma Broad treatment at five-leaf stage of foxtail millet on growth parameters, antioxidant enzymes, malondialdehyde (MDA), chlorophyll, net photosynthetic rate (P N), chlorophyll fluorescence and P700 parameters were studied 7 and 15 d after herbicide treatment, respectively. Results showed that Sigma Broad significantly decreased plant height, activities of superoxide dismutase (SOD), chlorophyll content, P N, PS II effective quantum yield (Y (II)), PS II electron transport rate (ETR (II)), photochemical quantum yield of PSI(Y (I)) and PS I electron transport rate ETR (I), but significantly increased MDA. Compared to herbicide treatment, BR dramatically increased plant height, activities of SOD, Y (II), ETR (II), Y (I) and ETR (I). This study showed BR pretreatment could improve the tolerance of Sigma Broad in foxtail millet through improving the activity of antioxidant enzymes, keeping electron transport smooth, and enhancing actual photochemical efficiency of PS II and PSI.