低氮诱导玉米幼苗叶片衰老过程中碳氮平衡的动态变化

叶片适时衰老对保证玉米产量有重要意义。本试验以玉米自交系PH6WC和PH4CV为研究对象,通过水培方法,设置低氮(0.04 mmol·L^-1,LN)和正常(4 mmol·L^-1,CK)氮素水平两种处理,在培养2、4、6和8 d后,对其幼苗第2和第3叶片表型、光合特性、叶片中氮素和糖分含量及碳氮比进行分析,旨在探究低氮胁迫下玉米幼苗叶片衰老过程中碳氮平衡的动态变化。结果表明: 与CK相比,LN造成两玉米自交系幼苗第2和第3叶片的面积、生物量、相对叶绿素含量、净光合速率、可溶性糖和淀粉含量均下降,而其氮物质生产能力均先后增加,但第2叶片的变化时间均早于第3叶片;在两叶片的各性状上,均为LN下PH6WC的变化幅度大于PH4CV,且仅幼苗叶片中的碳氮比在LN下显著提高;PH6WC的叶片衰老更快,PH4CV有更强的碳氮平衡能力,其叶片衰老相对滞后。综上,低氮会诱导玉米幼苗叶片衰老,高碳氮比具有促进叶片衰老的调控作用,低氮胁迫下幼苗叶片的碳氮平衡能力在两个玉米基因型间存在较大差异。     

Natural variation of ZmCGT1 is responsible for isoorientin accumulation in maize silk

Maize (Zea mays L.) silk contains high levels of flavonoids and is widely used to promote human health. Isoorientin, a natural C-glycoside flavone abundant in maize silk, has attracted considerable attention due to its potential value. Although different classes of flavonoid have been well characterized in plants, the genes involved in the biosynthesis of isoorientin in maize are largely unknown. Here, we used targeted metabolic profiling of isoorientin on the silks in an association panel consisting of 294 maize inbred lines. We identified the gene ZmCGT1 by genome-wide association analysis. The ZmCGT1 protein was characterized as a 2-hydroxyflavanone C-glycosyltransferase that can C-glycosylate 2-hydroxyflavanone to form flavone-C-glycoside after dehydration. Moreover, ZmCGT1 overexpression increased isoorientin levels and RNA interference-mediated ZmCGT1 knockdown decreased accumulation of isoorientin in maize silk. Further, two nucleotide polymorphisms, A502C and A1022G, which led to amino acid changes I168L and E341G, respectively, were identified to be functional polymorphisms responsible for the natural variation in isoorientin levels. In summary, we identified the gene ZmCGT1, which plays an important role in isoorientin biosynthesis, providing insights into the genetic basis of the natural variation in isoorientin levels in maize silk. The identified favorable CG allele of ZmCGT1 may be further used for genetic improvement of nutritional quality in maize.     

基于GIS的四川盆周北部山区夏玉米农业气象灾害风险评估——以旺苍县为例

气象灾害是制约我国农业发展的主要因素之一,明确夏玉米农业气象灾害风险对于防灾减灾具有重要意义。本研究基于自然灾害风险理论,以四川盆地北部山区的典型区域(旺苍县)1981—2018年气象数据和玉米产量数据为基础,确定影响夏玉米生产的主要致灾因子,并结合孕灾环境敏感性及承灾体脆弱性构建夏玉米综合农业气象灾害风险评估模型,对四川盆地北部山区夏玉米生产过程中的农业气象灾害风险进行评估。结果表明: 研究期间,成熟期高温、花期暴雨、成熟期暴雨、灌浆期连阴雨和孕穗期干旱是影响研究区夏玉米生长发育的主要农业气象灾害。旺苍县夏玉米农业气象灾害综合风险分布大致呈西南-东北走向,高风险和较高风险区分布区域约占旺苍县总面积的二分之一;灾害风险高值区主要位于研究区西南部,基本与致灾因子危险性高值区一致;灾害风险低值区多集中在西部边缘,此区域亦为成熟期高温、成熟期暴雨、花期暴雨气象灾害的低风险区。     

Integration of two herbivore‐induced plant volatiles results in synergistic effects on plant defence and resistance

Plants can use induced volatiles to detect herbivore‐ and pathogen‐attacked neighbors and prime their defenses. Several individual volatile priming cues have been identified, but whether plants are able to integrate multiple cues from stress‐related volatile blends remains poorly understood. Here, we investigated how maize plants respond to two herbivore‐induced volatile priming cues with complementary information content, the green leaf volatile (Z)‐3‐hexenyl acetate (HAC) and the aromatic volatile indole. In the absence of herbivory, HAC directly induced defence gene expression, whereas indole had no effect. Upon induction by simulated herbivory, both volatiles increased jasmonate signalling, defence gene expression, and defensive secondary metabolite production and increased plant resistance. Plant resistance to caterpillars was more strongly induced in dual volatile‐exposed plants than plants exposed to single volatiles.. Induced defence levels in dual volatile‐exposed plants were significantly higher than predicted from the added effects of the individual volatiles, with the exception of induced plant volatile production, which showed no increase upon dual‐exposure relative to single exposure. Thus, plants can integrate different volatile cues into strong and specific responses that promote herbivore defence induction and resistance. Integrating multiple volatiles may be beneficial, as volatile blends are more reliable indicators of future stress than single cues.     

Effect of exogenous ammonium gluconate on growth,ion flux and antioxidant enzymes of maize (Zea Mays L.) seedlings under NaCl stress

• Ammonium gluconate (AG) provides both an organic carbon source and a nitrogen source, which can positively improve soil fertility and delay soil degradation.
• We investigated the underlying mechanisms of both NH₄⁺‐ and C₆H₁₁O₇^?‐mediated resistance to high salt concentrations in maize (Zea mays L.), and how they relate to antioxidant cellular machinery, root system architecture, root activity and lignin content in roots.
• Seedlings treated with AG maintained lower Na⁺ content, higher chlorophyll content, higher CAT and POD activity, compared with those without AG and ammonium carbonate (AC). The total size of the root system, primary root length and number of lateral roots detected on the primary root treated with AG decreased compared with those not treated with AG at the same NaCl concentration. However, average root diameter and root activity when treated with AG were significantly higher than roots without AG at the same NaCl concentration. Furthermore, total size of the root system, primary root length and number of lateral roots detected on primary rootsof seedlings treated with AG were higher than those treated with AC at the same NaCl concentration.
• These results suggested that AG may be a good organic fertiliser under salt stress by decreasing Na⁺ content and increasing chlorophyll content, activity of antioxidant enzymes, root diameter and root activity in maize seedlings.

     

Comparative proteomics combined with analyses of transgenic plants reveal ZmREM1.3 mediates maize resistance to southern corn rust

Southern corn rust (SCR), which is a destructive disease caused by Puccinia polysora Underw. (P. polysora), commonly occurs in warm‐temperate and tropical regions. To identify candidate proteins related to SCR resistance and characterize the molecular mechanisms underlying the maize–P. polysora interaction, a comparative proteomic analysis of susceptible and resistant maize lines was performed. Statistical analyses revealed 1489 differentially abundant proteins in the resistant line, as well as 1035 differentially abundant proteins in the susceptible line. After the P. polysora infection, the abundance of one remorin protein (ZmREM1.3) increased in the resistant genotype, but decreased in the susceptible genotype. Plant‐specific remorins are important for responses to microbial infections as well as plant signalling processes. In this study, transgenic maize plants overexpressing ZmREM1.3 exhibited enhanced resistance to the biotrophic P. polysora. In contrast, homozygous ZmREM1.3 UniformMu mutant plants were significantly more susceptible to P. polysora than wild‐type plants. Additionally, the ZmREM1.3‐overexpressing plants accumulated more salicylic acid (SA) and jasmonic acid (JA). Moreover, the expression levels of defence‐related genes were higher in ZmREM1.3‐overexpressing maize plants than in non‐transgenic control plants in response to the P. polysora infection. Overall, our results provide evidence that ZmREM1.3 positively regulates maize defences against P. polysora likely via SA/JA‐mediated defence signalling pathways. This study represents the first large‐scale proteomic analysis of the molecular mechanisms underlying the maize–P. polysora interaction. This is also the first report confirming the remorin protein family affects plant resistance to SCR.     

Integrated use of plant residues,phosphorus and beneficial microbes improve hybrid maize productivity in semiarid climates

Phosphorus unavailability and lack of organic matter in calcareous soils under semiarid climates are the major reasons for low crop productivity. A field experiment was conducted at The Agronomy Research Farm of The University of Agriculture Peshawar (semiarid climate), during summer 2015. The objective of the research was to investigate the effect of plant residues, organic and inorganic phosphorus management on improving yield and yield components of hybrid maize (CS-200) with (+) and without (?) phosphate solubilizing bacteria. The experiment was laid out in randomized complete block design with split plot arrangement, using three replications. A combination of plant residues and phosphorus sources were used as mainplot factor, and phosphate solubilizing bacteria were used as a subplot factor. The results revealed that plant residues, phosphorus sources and phosphate solubilizing bacteria significantly affected all parameters under study except number of plants at harvest. Application of legume residues (Faba bean) increased ear length (22.9 cm), grains row^?1 (46) and ear^?1 (419), 1000 grains weight (365 g), grain yield (6175 kg ha^?1) and shelling percentage (83) as compared to paper mulberry and garlic residues. Phosphorus application at the higher rate of 120 kg ha^?1 from inorganic source (single super phosphate) was superior in terms of higher ear length (24.4 cm), number of grains row^?1 (48) and ear^?1 (455), 1000 grains weight (380 g), grain yield (6558 kg ha^?1), harvest index (42.7%) and shelling percentage (83%) than the lower rate of phosphorus (60 kg P ha^?1). Inoculation of maize seeds with beneficial microbes (phosphate solubilizing bacteria) significantly increased ear length (22.9 cm), number of grains row^?1 (45) and ear^?1 (413), 1000 grains weight (364 g), grain yield (6237 kg ha^?1), harvest index (41.8%) and shelling percentage (82) than without seed inoculation. On the basis of our results from this study, we concluded that application of faba bean residues, 120 kg P ha^?1 as single super phosphate along with seed inoculation with phosphate solubilizing bacteria could improve yield and yield components of hybrid maize under semiarid climates.