Acta Agronomica Sinica最新文献

The present study compared the sensitivity of tissue nitrogen (N) concentration, SPAD readings, Dualex readings, and SPAD/Dualex ratios for assessing the N status of corn (Zea mays L. cv. Pioneer 38B84) under different water supply conditions. A greenhouse trial was conducted with 4 rates of N fertilizer (0, 50, 50+75, and 200 kg ha⁻¹) and 3 watering levels (drought, drought followed by rewatering, and fully-watered). Tissue N concentration, SPAD, Dualex, and SPAD/Dualex values were influenced significantly by N rates and soil water content (SWC). Tissue N concentration, SPAD value, and SPAD/Dualex ratio increased with N rates, whereas Dualex value decreased. In the first phase of reaction to drought, tissue N concentration, SPAD value, and SPAD/Dualex ratio decreased rapidly, but Dualex value increased; however, the opposite pattern of response was observed in the long term. Under rewatering, tissue N concentration, Dualex value, and SPAD/Dualex ratio gradually recovered, whereas SPAD values did not change significantly as they did in the drought treatment. There were highly significant relationships between tissue N concentration and SPAD reading (r = 0.92, P ≤ 0.001), Dualex value (r = (0.86, P ≤ 0.001), or SPAD/Dualex ratio (r = 0.63, P ≤ 0.001). However, SPAD and Dualex values were better predictors of tissue N concentration under drought condition (r= 0.90, P ≤ 0.001 for SPAD; r = −0.83, P ≤ 0.001 for Dualex) than under fully-watered condition (r = 0.39, P ≤ 0.05) for SPAD; r = −;0.44, P ≤ 0.05 for Dualex) at the end of the trial. Among the indicators, Dualex is better to discriminate N treatments with consistent results across SWC levels.

The winter wheat (Triticum aestivum L.)-summer maize (Zea mays L.) relay system (W-M system) is the main cropping pattern in the Yellow-Huai-Hai River Valleys region of China. In recent years, winter freezing and drought stress occur frequently in this area, which causes great loss of wheat yield. In this study, the double-cropping maize system (M-M system) was tested in Xinxiang, Henan Province in 2009 and 2010 growing seasons to compare grain yield and resource efficiency between M-M and W-M systems. Compared to the W-M system, the M-M system produced 2.3% higher annual yield and increased 26.1% annual light energy efficiency and 6.5% annual temperature production efficiency. Besides, the economic benefit in the M-M system was 1628 RMB ha⁻¹ higher than that in the W-M system, and the total growth duration was reduced 140 d in the M-M system. This result suggests that the M-M system not only facilitates land fallow and avoids winter freezing and drought stress, but also obtains high light and temperature efficiencies and economic benefit.

The objective of this study was to explain the male sterile mechanism of wheat (Triticum aestivum L.) based on chloroplast proteome. A method for isolating intact chloroplast proteome from wheat floret was established. Using this method, the chloroplast proteomes were extracted from florets of the genic and physiological male sterile lines and their maintainer line, and separated in 2-dimensional electrophoresis (2-DE) gels. The cytoplasmic-nuclear sterile line, ms(S)-1376, had identical nuclear background with the maintainer line, (A)-1376, and the physiological male sterile line, ms(A)-1376, was derived from (A)-1376 after induction of chemical hybridizing agent SQ-1. The extraction method was effective to obtain high purity of intact chloroplast using discontinuous sucrose density gradient centrifugation with 3-step gradient densities of 30, 45, and 60%. The 2-DE result showed that the floret chloroplast protein profiles were different among the 3 lines at uninucleate anther stage, and 239 protein spots were visible on each gel (pH 4-7, molecular weight 14.4-66.2 kD). Six differentially expressed proteins were analyzed by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS) and indexed in bioinformation database. They were identified as acyl-CoA dehydrogenase domain protein, calmodulin-binding protein phosphatase, multiple catalytic peptidase, heat-shock protein 60, light receptor protein 2, and a protein of unknown function. These proteins are involved in series of physiological reactions such as metabolism of energy substances, chloroplast defendance, chloroplasts signal transduction, and plant growth. The differential expressions of these proteins among the 3 lines are likely related to the male sterility in wheat.

The objective of this study was to establish information on resistance to powdery mildew [Blumeria graminis (DC.) f. sp. tritici E.O. Speer] in wheat (Triticum aestivum L.) cultivars and germplasm lines. Reactions to 8 isolates of B. graminis f. sp. tritici were tested in the commercial wheat cultivars, wheat lines involved in the national yield trials, and core collection entries. The presence of resistance genes Pm4a, Pm8, and Pm21 was detected using gene-specific markers. Among 148 commercial wheat cultivars released since the 1980s, 16.9% exhibited resistance to multiple isolates, most of which were released in the 2000s. Over 50% of the cultivars released in different decades were susceptible to all the isolates tested. The frequencies of resistant cultivars from different wheat producing regions seemed to be associated with the significance of powdery mildew epidemic in a given region. Out of 1160 entries in the core collection, the proportions of entries resistant to isolate E09 were 3.4% and 4.2% in the landrace and improved cultivars, respectively. The Southwestern Autumn-Sown Spring Wheat Zone and the Xinjiang Winter-Spring Wheat Zone had higher percentages of E09-resistant cultivars than other wheat zones. None of the cultivar from the Southern Autumn-Sown Spring Wheat Zone, Northern Winter Wheat Zone, and Northern Spring Wheat Zone was resistant. The results of multiple-isolate test demonstrated that 33.7% were resistant among the 263 mini-core collection entries, most of which were resistant to 1 or 2 isolates. This indicates that there is a need to select resistant entries as recurrent parents for efficient use of existing core collection and to construct applied core collection for resistance to powdery mildew. Using the markers specific for resistance genes, the results of molecular detection demonstrated that 43.2% of the commercial cultivars contained gene Pm8. This gene was detected in the wheat lines involved in the national wheat yield trails at a high frequency. Genes Pm4a and Pm21 were detected mainly in the wheat lines or cultivars that were developed in the Yangtze River region. Some cultivars highly resistant to powdery mildew may carry other resistance genes that warrant further determination.

A yellow-green leaf mutant ygl98 was isolated by ethyl methane sulfonate (EMS) mutagenesis. The whole plant exhibited yellow-green character throughout the growing period. The contents of chlorophyll and carotenoid decreased by 45.3% and 45.6%, respectively, compared with its wild-type parent 10079. At maturity stage, the number of productive panicles per plant, seed-setting rate, and plant height of the mutant were reduced by 14.4%, 10.7%, and 7.4%, respectively. Under electron microscope, the chloroplasts in the ygl98 mutant were out-of-shape. A lot of cystic structures and poor thylakoids were observed in the chloroplasts of the ygl98 mutant, and grana stacks appeared to be less dense compared to those of the wild type. Genetic analysis showed that the yellow-green leaf character of the ygl98 mutant was controlled by one pair of recessive nuclear genes. Genetic mapping of the mutant gene was conducted using 771 yellow-green leaf individuals from the F₂ mapping population of ygl98/Zhefu 802. Finally, the mutant gene was mapped between insert/deletion (InDel) markers I3 and I4 on the long arm of chromosome 3 with the genetic distances of 0.07 cM and 0.19 cM, respectively. The physical distance between the 2 markers was 44.2 kb harboring 8 predicted genes annotated. Sequencing analysis of these candidate genes between the mutant and its wild type revealed that the single base change (G1 522A) of the gene for magnesium-chelatase ChlD subunit resulted in a missense mutation (A508T) in the encoded product. The same gene mutation caused by OsChlD (Chlorina-1) was documented previously. The Chlorina-1 mutant displays a severe yellowish-green leaf phenotype only at seedling stage, and the abnormal leaf color is first observed on the leaves of 2- to 3-week-old seedlings, while the ygl98 mutant exhibits yellow-green character throughout the growing period. The different phenotypes of the 2 mutants may be caused by the different mutational sites of OsChlD genomic sequence.

To understand the genetic mechanism of the semidwarf rice (Oryza sativa L.) mutant, iga-1, isolated by mutagenesis of outer space treatment, the mutant gene was identified through genetic analysis and molecular marker-aided fine mapping. Two iga-1 lines, CHA-2 and CHA-2N, showed great variations in agronomic traits compared to their wild-type parent Texianzhan 13, but their internodes had normal ratio in length, which indicated that they are dn type of dwarfing. Exogenous gibberellic acid (GA₃) could neither restore the wild-type plant height in CHA-2 and CHA-2N nor elongate plants of both lines as tall as Huiyang Zhenzhuzao and Aijiaonante treated with the same concentrations of GA₃; the concentrations of endogenous GA₃ in both iga-1 lines were not affected by the presence of iga-1 gene; and the activities of α-amylase in endosperm of both iga-1 lines were enhanced the same as their wild-type parent. Thus, iga-1 gene proved to be independent of GA₃. Using a large F₂ population (3000 individuals) derived from the cross between CHA-2 and a semidwarf japonica rice variety, 02428 (sd1sd1Iga-1Iga-1), the iga-1 gene was fine mapped between the insert/deletion (InDel) markers DL18 and DL19 on chromosome 5, with the physical distance of 32.01 kb. In this region, 5 open reading frames were predicted, including the gibberellin-insensitive dwarf mutant gene D1. However, D1 gene was not the candidate locus of iga-1 because there was no sequence difference between Texianzhan 13 and CHA-2 or CHA-2N.

The research on nuclear gene codon composition, usage pattern, and influencing factors in soybean can provide theoretical basis for applying genetic engineering techonology to improve soybean [Glycine max (L.) Merr.] varieties. In this paper, a total of 46 430 high confidence predicted coding sequences obtained from soybean genome database and 2071 full-length transcripts obtained from cDNA libraries were used for analyzing the composition and characteristics of soybean nuclear gene codons. The nucleotide composition, relative synonymous codon usage, and other parameters of soybean genome and full-length transcripts were calculated using CondonW software. The results showed that gene expression levels were significantly and positively correlated with the contents of G+C and GC3s, and genes with high G+C and GC3s contents had high codon preference. UCC and GCC were identified as optimal codons in soybean. Analysis of coding sequences in different lengths showed that codon preference reduced as the coding sequence (CDS) length increased, and longer CDS tended to select codons randomly. The CDS with 400 to 600 bp in length had the highest expression level according to the full-length transcripts data. The codon preference and expression level were almost identical between leaf-specific and seed-specific genes. However, seed-specific genes had significantly higher G+C and GC3s contents than leaf-specific genes, and the contents of aromatic amino acids encoded by seed-specific genes were significantly lower than that encoded by leaf-specific genes.

Water shortage is one of the major problems in wheat (Triticum aestivum L.) production in northern plain in China, and water-saving technique is of great importance in wheat cultivation in this area. A water-controlled irrigation strategy based on measuring soil moisture at jointing and anthesis stages (SMJ+SMA) was adopted in a 2-year field experiment in Shandong Province, China from October 2008 to June 2010, using the famous commercial wheat cultivar Jimai 22. The dynamics of photosynthetic parameters and dry matter accumulation were determined during grain filling period. In the 2008–2009 growing season, 3 irrigation treatments were designed under the plant densities of 150 (M1) and 225 seedlings m⁻² (M2), whose SMJ+SMA percentages were 65%+60% (W0), 75%+75% (W1), and 75%+75% at 7 d after jointing or anthesis (W2). In the 2009–2010 growing season, the irrigation treatments were conducted under only M1 density because M1 showed higher yield and water use efficiency (WUE) than M2 density in last season. The SMJ+SMA percentages in the 3 irrigation treatments of 2009–2010 were adjusted to 75%+60% (W'0), 85%+75% (W'1), and 85%+75% at 7 d after jointing or anthesis (W'2). Under the same irrigation condition, the maximal photochemical efficiency of PSII (F_v/F_m) and actual photochemical efficiency of PSII (ϕ_PSII) in M1 treatment were higher than those in M2 treatment from middle to late grain-filling stage, and the dry matter accumulation amount after anthesis and dry matter translocation to grains in M1 treatment were significantly higher than those in M2 treatment. Under the same plant density condition, the F_v/F_m and ϕ_PSII values were significantly higher in W2 treatment than in W1 treatment from middle to late grain-filling stage; and the photosynthetic rate (P_n), evapotranspiration (T_r), leaf WUE, and stomatal conductance (G_s) were higher in W'2 treatment than in W'1 treatment. The management of soil moisture to 75–85% at 7 d after jointing or anthesis showed the largest dry matter accumulation amount after anthesis and its contribution to grains, grain yield, and WUE under the M1 density. In the practical point of view, plant density of 150 m⁻² and the SMJ+SMA percentages of 75%+75% at 7 d after jointing or anthesis are proposed in water-saving wheat production with environment similar to this experiment.

A molecular marker-assisted selection (MAS) strategy was used to improve resistance to Rice stripe virus (RSV) in rice (Oryza sativa L. subsp. japonica cv. Wuyunjing 8). Rice variety “Aoikaze” with resistance to RSV was used as the donor. Sequence-tagged site (STS) markers STS11-31, STS11-7, STS11-19, and STS11-43 anchoring the resistance loci were used for MAS in the backcross progenies. In 2008, 70 lines of BC₃F₅ and 115 lines of BC₄F₄ population were obtained with stable agronomic traits after MAS assay. Further evaluation of agronomic traits, yield, grain quality, and resistance to RSV were carried out in these backcross progenies, and 10 BC₄F₅ lines and 2 BC₃F₆ lines showed similar phenotypes to Wuyunjing 8. The 12 lines were finally selected for the improved resistance to RSV and the high-yield and elite-quality of Wuyunjing 8.

YF2-1 is obtained by distant cross between rice (Oryza sativa) and Echinochloa caudate. To assess its osmotic stress resistance at physiological level, the gas exchange, chlorophyll a fluorescence, and antioxidation enzyme activities under osmotic stress simulated by PEG-6000 were studied in seedlings of upland rice YF2-1 and H65. The results showed that YF2-1 maintained higher net photosynthetic rate and stomatal conductance under osmotic stress condition, indicating that YF2-1 suffered less inhibition in photosynthesis. This may be related to its high water retaining capacity and its effective functions for high excessive light energy dispersing (high non-photochemical quenching) and high activities of antioxidation enzymes effectively clearing reactive oxygen species) produced by excessive light energy. The result shows that distant crossing may increase the resistance to osmotic stress in rice.