Drought Tolerance Identification and Eevluation of Maize during Flowering Stage in Guangxi

Total 20 maize varieties were subjected to drought stress at flowering stage, and then the relative water content, soluble sugar content, chlorophyll content, malondialdehyde (MDA) content and superoxide dismutase (SOD) activity in their leaves, as well as their yields were determined. The drought tolerance of the physiological and biochemical indexes was scored by five-level scoring method, and the drought tolerance index was calculated by the yield index to comprehensively evaluate the drought tolerance of maize during flowering stage. The results showed that the scores of drought tolerance of the maize varieties ranged from 1.929 3 to 5.659 5. Among them, the scores of Zhengda 619, Guidan 162 and Guidan 0810 were greater than 5.0, followed by Dika 008, Xianyu 30T60, Xianzhengda 901, Qingnong 68, South America No.1 and Wanchuan 1306 of which the scores were in the range of 4.0-5.0. The drought tolerance indexes were in the range of 0.410 4-1.096 3. Among the test maize varieties, the drought tolerance indexes of Guidan 0810, Pacific 99 and Zhengda 619 were greater than 1.0, and those of Xianyu 30T60, Dika 008 and South America No.1 were in the range of 0.9-1.0. The correlation between the two kinds of evaluation results was 0.588 7 and was extremely significant. The five-level scoring method and the drought tolerance index can be used simultaneously for the evaluation of drought tolerance of maize during flowering stage. The two aspects of evaluation results showed that Guidan 0810, Zhengda 619, Xianyu 30T60, Dika 008 and South America No.1 were drought-tolerant varieties, among which Guidan 0810 and Zhengda 619 were extremely highly drought-tolerant varieties

Effect of Drought Stress on Proteome of Maize Grain during Grain Filling

Based on isobaric tags for relative and absolute quantification (iTRAQ) technology, the proteome of grains of a maize cultivar Huangzao 4 under drought stress at grain filling stage was analyzed. The results show that under drought stress, 438 proteins were differentially expressed in the maize grains during grain filling. Among them, 200 were up-regulated and 238 were down-regulated. The gene ontology (GO) analysis shows that the biological processes in which differential proteins are more involved are cellular processes, metabolic processes and single biological processes; proteins in the cell component category are mainly distributed in cells, cell parts and organelles; and the proteins the molecular function category mainly possess catalytic activity and binding function. Differentially expressed proteins classified by COG are mainly involved in protein post-translational modification and transport, molecular chaperones, general functional genes, translation, ribosomal structure, biosynthesis, energy production and transformation, carbohydrate transport and metabolism, amino acid transport and metabolism, etc. The subcellular structure of the differentially expressed proteins is mainly located in the cell chloroplast and cytosol. The proportions are 35.01% and 30.21% respectively. KEGG metabolic pathway enrichment analysis shows that the differentially expressed proteins are mostly involved in antibiotic biosynthesis, microbial metabolism in different environments, and endoplasmic reticulum protein processing; the metabolic pathways with higher enrichment are the carbon fixation pathway and estrogen signaling pathway of prokaryotes; and the higher enrichment and greater significance are in the tricarboxylic acid cycle, carbon fixation of photosynthetic organisms and proteasome. The results of this study preliminarily reveal the adaptive mechanism of maize grains in response to drought stress during grain filling, providing a theoretical reference for maize drought-resistant molecular breeding

Physiological Characteristic Changes and Transcriptome Analysis of Maize (Zea mays L.) Roots under Drought Stress

Water deficit is a key limiting factor for limiting yield in maize (Zea mays L.). It is crucial to elucidate the molecular regulatory networks of stress tolerance for genetic enhancement of drought tolerance. The mechanism of drought tolerance of maize was explored by comparing physiological and transcriptomic data under normal conditions and drought treatment at polyethylene glycol- (PEG-) induced drought stress (5%, 10%, 15%, and 20%) in the root during the seedling stage. The content of saccharide, SOD, CAT, and MDA showed an upward trend, proteins showed a downward trend, and the levels of POD first showed an upward trend and then decreased. Compared with the control group, a total of 597, 2748, 6588, and 5410 differentially expressed genes were found at 5%, 10%, 15%, and 20% PEG, respectively, and 354 common DEGs were identified in these comparisons. Some differentially expressed genes were remarkably enriched in the MAPK signaling pathway and plant hormone signal transduction. The 50 transcription factors (TFs) divided into 15 categories were screened from the 354 common DEGs during drought stress. Auxin response factor 10 (ARF10), auxin-responsive protein IAA9 (IAA9), auxin response factor 14 (ARF14), auxin-responsive protein IAA1 (IAA1), auxin-responsive protein IAA27 (IAA27), and 1 ethylene response sensor 2 (ERS2) were upregulated. The two TFs, including bHLH 35 and bHLH 96, involved in the MAPK signal pathway and plant hormones pathway, are significantly upregulated in 5%, 10%, 15%, and 20% PEG stress groups. The present study provides greater insight into the fundamental transcriptome reprogramming of grain crops under drought

Effect of Foliar Application of Selenium Fertilizer on Yield, Selenium Content and Heavy Metal Contents of Waxy Maize

[Objectives] This study aimed to explore the effect of different concentrations of selenium fertilizer on the yield, selenium content and heavy metal contents of waxy maize, thereby providing reference for the scientific application of selenium fertilizer on waxy maize. [Methods] Different varieties of waxy maize (Guitiannuo 611, Guinuo 615 and Guiheinuo 609) were used as test materials. They were sprayed with different concentrations (0, 0.5, 1.0, 1.5 and 2.0 g/L) of water-soluble selenium fertilizer (Xinxibao) at the big flare stage, and the effect on the yield, selenium content and heavy metal contents of the waxy maize was analyzed. [Results] Foliar application of different concentrations of selenium fertilizer showed no significant effect on the yield and yield components of waxy maize. As the concentration of selenium fertilizer increased, the grain selenium content of different varieties of waxy maize increased. Among them, the increase of Guinuo 615 was the largest, of which the selenium content reached 0.265 mg/kg, 2.82 times that of the control (water). The cadmium and arsenic contents of different varieties of waxy maize decreased with the increase of the concentration of selenium fertilizer sprayed. Among the waxy maize varieties, the cadmium and arsenic contents of Guitiannuo 611 dropped the most significantly, up to 52.94% and 77.78%. In waxy maize, the correlation coefficients between selenium content and cadmium, arsenic contents were -0.550 9 (P<0.05) and -0.853 0 (P<0.01), respectively. [Conclusions] Spraying exogenous selenium fertilizer had no obvious effect on the yield of waxy maize. However, the increase of the concentration of exogenous selenium fertilizer could significantly increase the selenium content and reduce the cadmium and arsenic contents in grains of different varieties of waxy maize