秸秆还田条件下不同有机肥对土壤养分和冬小麦养分积累的影响

为了解秸秆还田条件下不同类型有机肥在麦田的施用效果,采用田间试验,设置T1(6 000kg·hm~(-2)玉米秸秆粉碎深翻还田)、T2(6 000kg·hm~(-2)玉米秸秆粉碎+有机肥A 1 500kg·hm~(-2)深翻还田)、T3(6 000kg·hm~(-2)玉米秸秆粉碎+有机肥B 1 500kg·hm~(-2)深翻还田)3个处理,研究了秸秆还田条件下不同类型有机肥对冬小麦越冬期、孕穗期和成熟期土壤微生物量碳(MBC)、氮(MBN)、土壤速效养分含量、冬小麦植株养分积累量以及冬小麦产量和当季经济效益的影响。结果表明,与T1处理相比,T2处理冬小麦各生育时期土壤微生物量碳、氮、土壤矿质态氮和土壤速效钾含量、植株氮和钾的积累量、冬小麦孕穗期和成熟期土壤速效磷含量、植株磷的积累量均显著提高;冬小麦实际产量和当季相对净收益亦均显著增加,分别提高了17.5%和22.0%。T3处理冬小麦越冬期土壤微生物量碳、越冬期和孕穗期土壤微生物量氮、各生育期土壤矿质态氮和越冬期土壤速效钾、各生育期植株氮和钾的积累量、孕穗期和成熟期植株磷的积累量亦均显著提高;冬小麦实际产量提高10.3%,达显著水平,但其当季经济效益并未显著提高。本试验条件下,综合施用两种有机肥对不同指标的影响,以T2处理效果更佳。     

On-farm soil N supply and N nutrition in the rice–wheat system of Nepal and Bangladesh

On-farm research to evaluate the productivity and nitrogen (N) nutrition of a rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping system was conducted with 21 farmers in the piedmont of Nepal and with 21 farmers in northwest Bangladesh. In Nepal, two levels of N-fertilizer (0–22–42 and 100–22–42 kg N–P–K ha⁻¹) and farmers’ nutrient management practices were tested in the rice season, and three levels of N (0–22–42, 70–22–42, and 100–22–42) and farmers’ practices were evaluated in the wheat season. The treatments in Bangladesh included a researchers managed minus-N plot (0–22–42) and the farmers’ practices. Rice and wheat yields were higher in all treatments than the 0–22–42 control plots, with the exception of rice with the farmers’ practices at one location in Bangladesh. The researchers’ treatment of 100–22–42 in Nepal resulted in larger yields of both rice and wheat than the farmers’ practices, indicating that farmers’ rates of N-fertilizer (mean 49 kg N ha⁻¹) were too low. Delaying wheat seeding reduced yields in the fertilized plots in both countries, especially as N-fertilizer dose increased. Soil N-supplying capacities (SNSC), measured as total N accumulation from the zero-N plots (0–22–42), and grain yields without N additions were greater for rice than for wheat in both Nepal and Bangladesh. Higher SNSC in rice was probably due to greater mineralization of soil organic N in the warm, moist conditions of the monsoon season than in the cooler, drier wheat season. However, SNSC was not correlated with total soil N, two soil N availability tests (hot KCl-extractable NH₄⁺ or 7-day anaerobic incubation), exchangeable NH₄⁺ or NO₃⁻. Wheat in Nepal had greater N-recovery efficiency, agronomic efficiency of N, and physiological efficiency of N than rice. Nitrogen internal-use efficiency of rice for all treatments in both countries was within published ranges of maximum sufficiency and maximum dilution. In wheat, the relationship between grain yield and N accumulation was linear indicating that mobilization of plant N to the grain was less affected by biotic and abiotic stresses than in rice.     

Tryptophanyl-tRNA Synthetase Gene WRS1 Regulates Rice Seed Development

【Objective】Aminoacyl-tRNA synthetases (aaRSs) are closely related to the transmission of genetic information. Besides translation, aaRSs in plants participate in gametogenesis and embryo development, early plastid development, immune signal perception and disease defense. In this study, we used a rice endosperm defective mutant to analyze the function of tryptophanyl-tRNA synthase (WRS1) during seed development, proving that WRS1 gene encodes a key factor affecting rice endosperm development. 【Method】In this study, a stably-inherited rice floury endosperm mutant (wrs1) was screened from the mutant library of indica cultivar N22 (Oryza sativa subsp. indica) induced by ethyl methane sulfonate (EMS). Map-based cloning and complementation test identified the target gene. Morphological observation and starch physicochemical properties of wrs1 mature seeds were analyzed. Semi-thin sections were prepared to observe the developing endosperm structure with a scanning electron microscope. qRT-PCR and GUS staining were performed to analyze the expression of WRS1. The expression of starch synthesis related genes in the endosperm at 12 days after flowering was determined by qRT-PCR, and these protein expression levels in mature seed were detected by immunoblotting. The free amino acid contents of mature seeds were measured with a fully automatic amino acid analyzer. 【Result】The seedlings of wrs1 were featured by obvious delay in development and finally withered and died. The floury grains isolated from the heterozygous mutant (WRS1wrs1) showed shrunken belly, decreased grain thickness and thousand-grain weight. Total starch contents, the peak viscosity and breakdown viscosity of pasting starch were lower in wrs1. The compound starch granules in developing endosperm of wrs1 were smaller and loosely arranged. WRS1 was restricted to the 183 kb region of the long arm of chromosome 12. Sequencing revealed a single base substitution in exon 6 of the tryptophanyl-tRNA synthetase gene (WRS1), resulting in a substitution of methionine. The expression of most starch synthesis-related genes in wrs1 was down-regulated, while these proteins showed different accumulation levels. The contents of proteins in wrs1 grains were decreased, while free amino acids contents were significantly increased. 【Conclusion】WRS1 encodes tryptophanyl-tRNA synthase. Mutation of this gene affects amino acid homeostasis and protein synthesis in rice endosperm, resulting in abnormal expression of the genes in starch synthesis pathway which affects starch synthesis and accumulation, and eventually lead to seed development defects.     

Effect of emergence time,inter- and intra-specific competition on growth and fecundity of Echinochloa crus-galli in dry-seeded rice

Since 2005, the evolution and spread of herbicide-resistant Echinochloa crus-galli biotypes have posed a serious threat to crop production in the Philippines. A comprehensive knowledge of E. crus-galli ecology and fecundity is fundamental in managing different biotypes of this weed. It was hypothesized that (a) high weed plant density produces more biomass and fertile seeds per unit area, (b) rice interference reduces the biomass and fecundity of the weed, and (c) a delay in weed emergence reduces the soil seed bank. In 2013, experiments were conducted in the wet season (WS) and dry season (DS), to understand the effect of E. crus-galli densities (40 and 80 plants m⁻²) on its growth, survival, and fecundity, with varying emergence times of 2, 15, 30, and 45 d after rice emergence (DARE). Relative to the weed plants grown without rice interference, E. crus-galli growth and seed production was lower in the presence of rice. Percent survival and plant height of E. crus-galli declined in a linear manner in the DS, and declined in a quadratic manner in the WS. Tiller number, inflorescence number, inflorescence biomass, and shoot biomass per plant declined in an exponential manner, with a delay in emergence of each cohort relative to rice. Across rice seeding rate, weed density, and emergence time, there was a linear relationship (y = 110x − 272 in the DS and y = 100x − 220 in the WS) between E. crus-galli shoot biomass and the number of seeds plant⁻¹. Relative to the late-emerging weed cohorts, E. crus-galli seed production (1320–1579 seeds plant⁻¹), 1000-seed weight (2.2–2.9 g), and seed yield (2808–2334 kg ha⁻¹) were higher when seedlings emerged with the crop (2 DARE). None of the seedlings that emerged 45 DARE produced viable seeds. Seed germination of the first two cohorts (2 and 15 DARE) ranged from 84 to 91%. The delay in emergence of E. crus-galli beyond 30 DARE reduced the percentage of germinable and viable seeds, and increased the percentage of non-viable seeds produced plant⁻¹. The results suggest that cultural weed management approaches that delay the emergence of E. crus-galli can reduce weed biomass and seed production, and is thus valuable for preventing seed rain to the seed bank by noxious weed biotypes in the field.     

Antifungal activity of polyacetylenes isolated from Cirsium japonicum roots against various phytopathogenic fungi

Antifungal substances from a methanol extract of Cirsium japonicum roots were purified and characterized, and their antifungal activities against various plant pathogens were evaluated. Three polyacetylene substances were isolated from roots of C. japonicum using repeated column chromatography; these were identified as ciryneol A, ciryneol C and 1-heptadecene-11,13-diyne-8,9,10-triol by mass and nuclear magnetic resonance spectral analyses. In vitro antifungal activity of the three substances varied according to compound and target species. Magnaporthe oryzae, Colletotrichum coccodes, Colletotrichum acutatum, Pythium ultimum and Botrytis cinerea were relatively sensitive to the three polyacetylenes, with IC₅₀ values below 50 μg mL⁻¹. In vivo, they all showed similar and broad antifungal spectra against the seven plant diseases tested. At 500 μg mL⁻¹, all three compounds effectively suppressed the development of rice blast, rice sheath blight, tomato late blight, wheat leaf rust and red pepper anthracnose, with control values over 90%. They were highly active especially against wheat leaf rust; they controlled the development of this disease more than 88% even at a concentration of 125 μg mL⁻¹. In addition, ciryneol C effectively suppressed barley powdery mildew. This is the first report on the antifungal activities of the three polyacetylenes from roots of C. japonicum against plant pathogenic fungi. Polyacetylenes from roots of C. japonicum may contribute to the development of environmentally safer alternatives to protect crops from various phytopathogenic fungi.     

A Wheat Xylanase Inhibitor Protein (XIP-I) Accumulates in the Grain and has Homologues in Other Cereals

We have measured xylanase inhibitor activity against an Aspergillus niger xylanase in different parts of the wheat plant at different stages of development and used immunodetection to determine the spatial and temporal distribution of xylanase inhibitor protein I (XIP-I) in Triticum aestivum var. Soisson. Although xylanase inhibitor activity was detected in all parts of the wheat plant throughout development, XIP-I was located predominantly in the grain tissue, where it appears at a late stage in grain development and persists after germination, indicating that the different xylanase inhibitor proteins are under different regulatory controls. (1,4)-β-Xylanase activity was detected in wheat grains during development and post-germination. Pure XIP-I and a crude sample containing TAXI inhibitors but not XIP-I did not have the ability to inhibit this endogenous (1,4)-β-xylanase activity. Protein extracts from the seeds of various monocots were also tested for the presence of XIP-I, where it was found to be present in the grains of several wheat varieties, rye and barley, but was not detected in rice, sorghum or maize.     

Modeling plant carbon flow and grain starch accumulation in wheat

The process of starch accumulation in grain directly influences the yield and quality formation in wheat. Since few studies have been aimed at modeling the grain starch accumulation, this study was undertaken to develop a simplified process model for predicting the rate of starch accumulation in wheat grain by focusing on the variation of plant carbon dynamics post-anthesis. Five different experiments involving genotypes, nitrogen rates and water regimes were conducted to support model development and model evaluation. The model proposed that the starch accumulation rate (STR) in individual grain was determined by the availability of carbon source in plant (GCA_i) and the ability of starch synthesis in grain (f(A_i)), as influenced by the factors of temperature, water and nitrogen conditions within plants. The f(A_i) could be described in a two-section curve with post-anthesis growing degree days (GDD), first exponential increase and then linear decrease. The GCA_i was determined by post-anthesis carbon assimilation and carbon remobilization from vegetative organs to grains. A genotypic parameter was incorporated into the model algorithm, i.e. the maximum rate of individual grain starch accumulation, to differentiate the ability of starch accumulation among cultivars. The overall performance of the model was validated with different data sets from three field experiments spanning 3 years and comprising various genotypes, nitrogen and water levels. The RMSE values for all treatments were averaged as 12.51%, indicating a good fit between the simulated and observed data. It appears that the model can give a reliable prediction for grain starch accumulation of different wheat cultivars under various growing conditions.     

Genotypic variation in grain phosphorus concentration,and opportunities to improve P-use efficiency in rice

Continual removal of phosphorus (P) from fields in rice grains at harvest results in lower soil fertility in low-input farming systems and drives the need for fertiliser inputs in high-input farming systems. High-P content in rice grains (the majority as phytate) contributes little to human nutrition and agronomic practices such as growing seedlings in high-P media or seed P coating at sowing (in direct-sown crops) may overcome the reported need for high-P seed for seedling establishment. Thus, reducing the amount of P in rice grains at maturity through breeding may represent a novel means to reduce ‘mining’ of soil P. We investigated the uptake and partitioning of P in rice plants and examined the scope for breeding rice with lower grain P by assessing genotypic variation for phosphorus harvest index (PHI) and seed P concentrations among a set of 38 rice genotypes in the field. At maturity approximately 75% of total plant P was found in grains and translocation of P from stems and leaves contributed substantially to grain P. However, unlike other cereals such as wheat, rice plants continued dry matter and P accumulation until maturity with approximately 40% of total plant P taken up post anthesis. In the field study, PHI differed significantly among genotypes (from 57 to 87) but was highly correlated to HI (P ≤ 0.001), suggesting that exploiting genotypic variation for this trait may be counterproductive. Grain P concentrations varied from 1.96 to 3.18 mg P g⁻¹, and were neither associated with reductions in grain yield or seed size, nor significantly correlated to HI. Grain P concentration therefore appears to be a suitable screening criterion and the 50% variation observed among genotypes suggests that scope exists for breeding rice with lower grain P concentration to reduce the off-take of P from rice fields at harvest.     

Cd、Cr、Pb复合胁迫下小麦植株重金属的积累与分布

为了预测重金属复合胁迫对小麦的危害,采用溶液培养、田间土柱栽培等毒理试验方法,分析了小麦幼苗期及成熟期Cd、Cr、Pb在植株不同器官的富集,并对小麦受重金属胁迫的安全限量值进行了研究。结果表明,①Cd、Cr、Pb二元或三元胁迫条件下,小麦幼苗期植株各器官对重金属的富集浓度均极显著高于单一胁迫处理,说明复合胁迫加剧了重金属向小麦体内的迁移累积。成熟期小麦对Cd、Cr、Pb的富集比较依赖于土壤中相应Cd、Cr、Pb的浓度水平,其他两种重金属的协同作用在根系所占比例大约为5.09%～21.66%。②各器官中重金属的富集表现:幼苗期为根系>叶鞘>叶片,成熟期为根系>茎叶>籽粒。但幼苗期复合胁迫促进了重金属向地上部分的转移。③幼苗期植株各器官对重金属富集系数的大小为Cr>>Pb>Cd,表明幼苗期小麦根系对Cr的富集能力最强;植株地上部分的重金属平均富集量Cd为68.68%、Cr为51.63%、Pb为70.83%,说明Cd、Pb运输到地上部的能力较强。成熟期Cd在小麦地下、地上各器官的转移速率最快,Cr次之,而Pb转移到籽粒中去的量很少。     

提高水稻成熟种胚体细胞培养力

实验结果认为,水稻成熟胚是一种“竞争性”外植体。高浓度的脱落酸（ABA）能有效地抑制胚芽和胚根的生长,而对水稻盾片愈伤组织的生长影响较小,从而促进盾片愈伤组织的同步健壮生长。这些愈伤组织致密,呈乳白色且分化频率高。调节分化培养基的浓度可减少愈伤组织变褐老化,有效地提高愈伤组织绿苗分化率。在诱导培养期间,较高的2,4－D浓度（大于1 mg/L）和6－BA会抑制种胚体细胞愈伤组织的诱导,其中籼稻比粳稻敏感。在诱导培养基中附加2,4－D 0.5 mg/L,BA 0.5 mg/L,ABA 5 mg/L,B_1 (5－10 mg/L)对成熟籼稻种胚培养是较合适的。     

Nucleus-Encoded Thylakoid Protein,OsY3IP1, Confers Enhanced Tolerance to Saline and Alkaline Stresses in Rice

Abiotic stress confers serious damage to the photosynthetic machinery, often resulting in plant growth inhibition. Hypothetical chloroplast open reading frame 3 (Ycf3)-interacting protein 1 (Y3IP1) is a nucleus-encoded thylakoid protein and plays an essential role in the assembly of photosystem I. The full-length cDNA over-expresser (FOX) gene-hunting system is an approach using systemically generated gain-of-function mutants. Among the FOX-rice lines, a line CE175 overexpressing rice Y3IP1 gene (OsY3IP1) displayed less inhibition of root growth under saline (NaCl) stress. The expression of OsY3IP1 was up-regulated under saline and alkaline (Na₂CO₃) stresses in the rice variety Kitaake. After saline and alkaline treatments, transgenic Kitaake overexpressing OsY3IP1-GFP (OsY3IP1-GFPox/Kit) displayed higher levels of chlorophyll content compared to Kitaake. Under the stress conditions, the maximum quantum yield of photosystem II photochemistry levels was higher in OsY3IP1-GFPox/Kit than in Kitaake. The increased tolerance conferred by OsY3IP1 overexpression correlated with reduced reactive oxygen species accumulation. Our data provide new insights into the possible role of OsY3IP1 in the pathway suppressing photooxidative damage under stress conditions. These features can be further exploited to improve saline and alkaline tolerances of rice plants in future.