Acta Agronomica Sinica最新文献

Fusarium verticillioides (Sacc.) Nirenberg [syn. F. moniliforme J. Sheld., teleomorph: Gibberella fujikuroi (Sawada) Ito in Ito & K. Kimura] is an important causal agent of diseases in maize (Zea mays L.) worldwide, which invades maize plants at all growth stages. This filamentous fungus not only incites obvious symptoms on maize root, stem, and ear, but also is able to infect plants without any visible symptom (endophytic infection). Fluorescent reporter gene-labeled filamentous fungus permits in vitro and in planta monitoring growth and development of the fungus. In this study, gene DsRed encoding red fluorescent protein was delivered into F. verticillioides strain Fv-1 via Agrobacterium tumefaciens-mediated transformation. Using the DsRed-tagged F. verticillioides, systemic colonization of the fungus in root and stem of the susceptible maize inbred line B73 was investigated to understand the interaction between F. verticillioides and maize. The fungus invaded and multiplied inside the lateral root tissues. Some conidia tended to colonize on the veins of maize root surface and grow along the veins after their germination. Whereas, some others penetrated the plant cells where they attached and formed hyphae for attacking cells nearby. Usually, the mycelia migrated from root to stem through intercellular parts of tissues, while some mycelia ran across different host cells. The colony forming unit (CFU) values from root tended to decrease following the inoculation time, but those from stem inclined to increase. This indicates that F. verticillioides is able to attack the aboveground parts of plant via systemic colonization on root. The results from the present study are useful in disclosing the interaction between F. verticillioides and maize, and can be extended to studying interactions between other soil-borne fungi and plants.

Insertional mutagenesis has now been widely used to knockout genes for functional genomics. The maize Mutator transposons hold an advantage of high activity to construct large mutant libraries. In this study, a MuDR line was used to cross with an elite Chinese maize inbred line Z31. A total of 1000 M₁ individuals were planted and self-pollinated to generate their M₂ families. Experiments were conducted to investigate the insertion specificity of MuDR related transposable elements. Six hundred and ninety-five MuDR inserted flanking sequences were isolated with a modified MuTAIL-PCR method and analyzed with bioinformatics. Three hundred and seventy-four non-redundant insertion sites were identified and 298 of them were mapped to a single locus on the integrated maize map. The results revealed some prominent features of the MuDR-related insertions of maize: random distribution across the 10 chromosomes, preferential insertion into genic sequence and favoring some classes of functional genes.

To explain the metabolic mechanism of leaf during grain filling of rice (Oryza sativa L.) in response to nitrogen application, the differential expression patterns of leaf proteins were investigated at different time points of grain filling using two-dimensional electrophoresis (2-DE) technique. Thirty-two differentially expressed proteins were detected including 27 up-regulated and 5 down-regulated proteins in response to increased nitrogen application at grain-filling stage. These proteins were classified into 5 main categories according to their deduced functions, which were involved in photosynthesis (12), response to adversity resistance (5), hormone synthesis and signal transduction (5), cell growth and differentiation (5), and unknown functions (5). The photosynthesis-related features, together with adversity-defense-related indicators, were then determined to reveal the regulation of nitrogen to rice leaf. As appropriate increase of nitrogen application at late growth stage, the adversity-defense ability of leaf was strengthened during grain filling by delaying degradation of chlorophyll and soluble protein, prolonging photosynthesis, activating superoxide dismutase, peroxidase, and catalase, and depressing lipid peroxidation. These physiological changes verified the result of proteomics. Therefore, appropriate increased nitrogen supply at late growth stage is favorable to leaf metabolisms during grain filling in rice.

In the Yangtze River basin, winter fallow is popular for the double cropping rice (Oryza sativa L.). In this study, the possibility of adding a rapeseed cropping season after late rice harvest in this area was studied with the purpose of extending direct-seeding rapeseed under no-tillage cultivation pattern. In a 2-year field experiment from 2008 to 2010, the rapeseed cultivar Huashuang 5 (Brassica napus L. cv. Huashuang 5) were planted in 3 locations in Hubei Province of China after harvesting late rice. At both individual and population levels, the effects of plant density and nitrogen (N) application rate on rapeseed growth and yield formation were measured at seedling, budding, flowering, podding, and maturity stages. The cultivation pattern of no-tillage and direct-seeding after late rice harvest shortened the growth duration of rapeseed, especially at seedling stage, but prolonged the late budding stage in spring. The biomass accumulation from emergence to early budding was deficient severely, resulting in quick growth from budding to flowering of rapeseed. Application of N fertilizer had significant effects on enhancing the growth and yield formation of rapeseed through improving the individual and population qualities. Under the N rate of 270 kg ha⁻¹ condition, the highest yield of rapeseed was approximately 2250 kg ha⁻¹ at the density of 4.5 × 10⁵ plants or 6.0 × 10⁵ plants per hectare. The yield level was higher than that of average local rapeseed production. In the practice of no-tillage and direct seeding cultivation technique in the double rice cropping rice area, both nitrogen application rate and planting density should be considered simultaneously to obtain high quality of plant population and high yield of rapeseed.

The objectives of this study were to investigate the changes in plant hormones during tiller bud growing in rice (Oryza sativa L.) and the mechanism that underlies the effect of hormonal regulation on tiller bud growth. Rice cultivars Yangdao 6 (indica) and Nanjing 44 (japonica) were used to investigate the effects of exogenous abscisic acid (ABA, 50 mg L⁻¹), gibberellic acid 3 (GA₃, 50 mg L⁻¹), and α-naphthalene acetic acid (NAA, 50 mg L⁻¹) on tiller bud outgrowth and the changes of endogenous hormones. After foliar spray of the exogenous hormones, the tiller bud growth was completely inhibited in treatments of GA₃ and NAA applies; but exogenous ABA application slowed down the growth rate of tiller bud. Both exogenous GA₃ and NAA increased the ABA contents in tiller node and tiller bud and decreased the zeatin + zeatin riboside (Z+ZR) contents. Exogenous GA₃ increased the IAA content in tiller node; besides, the variation of IAA and Z+ZR occurred earlier than that of ABA. Suggestively, these 3 endogenous hormones are closely associated with tiller bud growth, of which only IAA and Z+ZR play key roles, although ABA can affect the growth velocity of tiller bud. Exogenous hormones regulate tiller bud growth through changing the contents of endogenous ABA, IAA, and Z+ZR in rice plant.

The purposes of this study were to understand the root activity and root exudates of rice (Oryza sativa L.) in response to different levels of potassium (K) and calcium (Ca) nutrients and the effect of K and Ca on rice grain quality. Cultivars Yangdao 6 (indica) and Yangjing 9538 (japonica) were cultured in hydroponical solutions and treated with different Espino nutrition solutions from heading to maturity, which were supplemented with complete K and Ca (standard Espino nutrition solution, control), half K (1/2K), zero K (0K), half Ca (1/2Ca), and zero Ca (0Ca) nutrition. Compared to the control, the 0K treatment significantly decreased root activity, ATPase activity, and concentrations of citric acid, Ca²⁺, K⁺, and NH₄⁺ in the root exudates, but accelerated root senescence; and the 0Ca treatment significantly decreased concentrations of oxalic acid, Ca²⁺, K⁺, and NH₄⁺ in the root exudates. The oxalic acid concentration in root exudates was positively correlated (P < 0.01) with chalky grain percentage, chalkiness, and gel consistency of rice grain; whereas the citric acid concentration in exudates was negatively correlated (P < 0.01) with chalky grain percentage, chalkiness, and breakdown value, but positively correlated (P < 0.05) with setback value. At early (10 d after heading) and mid grain-filling (20 d after heading) stages, the concentrations of K⁺ and Ca²⁺ in root exudates were negatively correlated (P < 0.05) with chalky kernel percentage, chalkiness, and amylose contents, and the NH₄⁺ concentration was also negatively correlated (P < 0.05) with amylose content of grain. This result indicates that root exudates are closely associated with grain quality. K and Ca nutrition regulate root exudates and consequently affect grain quality of rice.

Abscisic acid (ABA) is a phytohormone and mediates response and adaptation of higher plants to various environmental stresses during vegetative growth. The basic leucine zipper (bZIP) transcription factors are also important regulators of plant development and abiotic resistance, acting through either ABA-dependent or ABA-independent mechanisms. In this study, the involvement of the AtbZIP1 gene in plant responsiveness to ABA was investigated and characterized. As confirmed by PCR and reverse transcription PCR (RT-PCR), AtbZIP1 has been silenced in mutant Arabidopsis ko-1 (SALK_059343) and ko-2 (SALK_069489C). The AtbZIP1 knockout plants reduced the sensitivity to ABA both at the seed germination stage and the seedling stage, with improvement in rates of germination, leaf opening/greening, and primary root length. For investigating whether the regulation of AtbZIP1-mediated ABA responsiveness depended on the ABA-responsive elements (ABRE), the AtbZIP1 HIS6 fusion protein was expressed in Escherichia coli. The AtbZIP1 HIS6 was specifically bound to the ABRE cis-elements. According to the results of semiquantitative RT-PCR analysis, AtbZIP1 disruption altered expressions of some ABA responsive genes, such as NCED3, RD22, KIN1, and RD29A. The results indicated that AtbZIP1 regulates ABA signal transduction by binding to the ABREs and altered the expressions of the ABA responsive genes.

To understand the mechanism of male sterility induced by gametocide SQ-1 in wheat (Triticum aestivum L.), TaPDC-E1α gene was isolated using silcon cloning technique. The open reading frame of this gene is 1401 bp in length, putatively encoding 388 amino acid residues. This gene possesses the conserved TPP domains. Two potential phosphorylation sites of serine residues might be present in the TaPDC-E1α protein of wheat. According to semiquantitative reverse transcription polymerase chain reaction (RT-PCR) analysis, the expression levels of TaPDC-E1α in the physiological and genetic male sterile lines were lower than those in the fertile lines. Compared with the fertile lines, the expression of PDK was obviously down-regulated in the physiological male sterile line induced by SQ-1. However, PDK gene was highly expressed in the genetic male sterile lines. The expression levels of PDP gene were similar in the fertile and the male-sterile lines. These results suggest that the pathway of energy metabolism in the SQ-1 induced sterile line is more susceptible than that of the genetic male-sterile line. The upstream signal mechanism of mediating PDK gene may be inconsistent between the male-sterile line induced by SQ-1 and the genetic male-sterile line.

For evaluating the environmental adaptability and stability of soybean [Glycine spp.] germplasm, the data of important agronomic traits in a mini core collection were analyzed using the additive main effects and multiplicative interaction (AMMI) model. The mini core collection contained 60 accessions of soybean germplasm, and their agronomic traits were investigated in 6 trail sites in Hebei, Henan, and Shandong provinces of China from 2008 to 2009. The interactions between genotypes and environment (G × E) were significant (P < 0.01) in plant height, effective branch number, 100-seed weight, and yield per unit area, which accounted for 16.7–24.6% of total variations. Thus, it is necessary to dissect the environmental stability of the mini core collection. Adaptabilities of genotypes varied across planting sites in different traits. Some genotypes showed wide adaptability and good stability with small phenotypic variations in different sites; whereas, strong G × E interaction was observed in some other genotypes. This result provides a theoretical basis for effectively using the mini core collection in soybean breeding in the Huang-Huai Rivers Region of China.

High temperature after anthesis may degrade the grain quality of rice (Oryza sativa L.). To understand the effect of stress duration (initial and mid grain filling stages) and the influence to grain quality at different spikelet positions, an indica cultivar and a japonica cultivar, Yangdao 6 and Yangjing 9538, were used in a pot experiment under 35 °C during the initial (8–18 d after anthesis) and mid (18–28 d after anthesis) terms of grain filling. The treatment under normal atmospheric temperature (25–27 °C) served as the control. The high-temperature treatment at initial filling stage had larger influence on grain quality than the stress imposed at mid filling stage, and the grain quality varied with cultivars and spikelet positions. Both treatments with high temperature reduced milled rice rate and head milled rice rate, but increased crude protein content; grains on the primary branches received larger effect than those on the secondary branches. In the same branch, later-flowered grains were affected greater than early-flowered grains. When high temperature was imposed at initial grain filling stage, the chalkiness degree and chalky grain percentage were significantly increased in the early-flowered grains, whereas the amylose content was significantly decreased; such variations were larger in grains on the primary branches than those on the secondary branches. Besides, the 2 cultivars showed different responses of grain quality to high-temperature stress, which indicated the fact of phenotypic difference on temperature sensitivity. Generally, the influence of temperature on rice quality was greater when the stress imposed at the earlier stage of grain filling.