Translocation efficiencies and allocation of nitrogen,phosphorous and potassium in rice as affected by silicon fertilizer under high daytime temperature

High temperature has become a bottleneck limiting rice production in many rice‐growing districts. Silicon is considered as a beneficial element for rice development, being involved in mitigating adversity stress. In order to ascertain how high temperature and silicon affect nitrogen (N), phosphorous (P) and potassium (K) translocation efficiencies and allocation in rice plants, a field experiment with split plot design was conducted in two consecutive years. Silicon fertilizer treatments, including applying silicon fertilizer and without applying silicon fertilizer, were regarded as main plots. Temperature treatments, including high daytime temperature (HDT) and normal temperature (NT), were assigned as subplots. The results indicated that, as compared to NT, HDT reduced the translocation efficiencies of N, P and K in leaves and stems plus sheaths except for the K translocation efficiency in stems plus sheaths. Moreover, HDT decreased grain yield and the allocation rates of N, P and K in panicles at maturity. Under HDT, the application of silicon fertilizer obviously enhanced the N translocation efficiency of leaves and stems plus sheaths, and the K translocation efficiency of leaves. The application of silicon fertilizer increased grain yield and the allocation rates of N and K in panicles at maturity under HDT. Correlation analysis showed that rice grain yield was positively significantly correlated with N, P and K translocation efficiencies of leaves and their allocation rates in panicles at maturity. Conversely, grain yield was negatively related to the N and P allocation rates in leaves and stems plus sheaths at maturity. These results imply that HDT generated adverse effect on the translocation efficiency of nutrition in rice plants, which might be another damage induced by high temperature to the formation of rice grain yield. Additionally, silicon fertilizer could play a key role in positively regulating the N and K translocation efficiencies and allocation rates in rice under HDT.     

Increasing genetic diversity by participatory varietal selection in high potential production systems in Nepal and India

On-farm varietal biodiversity was studied through household surveys in two high potential production systems in Chitwan and Nawalparasi districts of the Nepal Terai and in Lunawada sub-district, Gujarat, India. Diversity was extremely low in Chaite rice in the Nepal study area (weighted diversity 0.04) and low in main season rice in the India study area (weighted diversity 0.34). In both areas, one cultivar dominated, CH 45 in Nepal and GR11 in India. In the India study area, biodiversity varied with the socio-economic group and better-off farmers had a greater varietal diversity. Participatory varietal selection (PVS) identified new varieties that farmers preferred. Their adoption by farmers increased on-farm varietal biodiversity within the three cropping seasons studied. Despite the commonly assumed uniformity of high potential production systems, the new varieties occupied specific niches in the farming system. Farmers' preferences for different varieties – there were large differences in quality traits and maturity period among the new varieties – should help to maintain biodiversity. Overall production is expected to increase as each niche becomes occupied increasingly by the best-adapted variety. PVS is a simple and powerful method of increasing food production in the high potential production systems that produce most of the developing world's grain. This revised version was published online in August 2006 with corrections to the Cover Date.     

Methane oxidation in non-flooded soils as affected by crop production — invited paper

Methane is an important greenhouse gas, which contributes approximately 20% to global warming. The atmospheric CH₄ concentration is increasing rapidly, resulting from an imbalance between CH₄ production and consumption. The only known biological CH₄ sinks are soils where methanotrophic bacteria consume CH₄ by oxidizing it. For several reasons the CH₄ uptake potential, particularly of arable soils and grassland, is only partly exploited, as several agricultural practices have adverse impacts on the activity of the CH₄ oxidizing bacteria. The kind of land use in general has a remarkable influence with much higher oxidation rates under forest than under grassland or arable soil. Regular soil cultivation by ploughing and fertilization with ammonium or urea have been identified as main factors. Immediately after ammonium application the methanotrophic enzyme system is blocked, resulting in an inhibition of CH₄ oxidation. In addition to this short-term effect a long-term effect exists after repeated ammonium fertilization, which is most likely caused by a shift in the population of soil microbes. Crop residues affect CH₄ oxidation differently, depending on their C/N ratio: with a wide C/N ratio no effects are expected, whereas with a narrow C/N ratio strong inhibition was observed. Animal manure, particularly slurry, can cause CH₄ emission immediately after application, whereas in the long run farmyard manure does not seem to have adverse impacts on CH₄ oxidation. The methanotrophic activity decreased markedly with soil pH, although in many cases liming of acidified soils did not show a positive effect. Arable soils have a rather small pH range which allows CH₄ oxidation, and the inhibitory effect of ammonium can partly result from a concomitant decrease in soil pH. Reduced tillage was identified as a measure to improve the methanotrophic activity of arable land, set aside of formerly ploughed soil points into the same direction. Plant growth itself is not primarily responsible for observed effects on CH₄ oxidation, but secondary factors like differential pesticide treatments, changes in pH, or cultivation effects are more likely involved. Although for the overall CH₄ fluxes the oxidation processes in agricultural soils are of minor importance, all available possibilities should be exhausted to improve or at least preserve their ability to oxidize CH₄.     

水分管理和秸秆还田对稻田甲烷排放及固碳的影响研究进展

综述了水分管理对稻田甲烷产生、氧化和传输排放的影响以及秸秆还田对稻田甲烷排放和固碳的影响,并提出了今后中国稻田CH4排放应加强以下2方面的研究：（1）水分管理对稻田甲烷产生机理的研究;（2）秸秆还田对稻田甲烷排放和土壤固碳的综合影响研究,旨在为以后的水稻生产如何进行水分管理和秸秆还田提供参考和依据,以期充分发挥稻田的生态效益。     

Quality retention and potential shelf-life of fresh-cut lemons as affected by cut type and temperature

The effects of four cut types (wedges, slices, 1/2 and 1/4 slices) of ‘Lisbon’ lemons (Citrus lemon L.) and storage at four temperatures (0, 2, 5 and 10 °C) on post-cutting life were studied. Respiration rates of all cut types that were stored at 0, 2 and 5 °C up to 8 days were 2–5 times higher than those of the whole lemons, while the increase was up to 12-fold at 10 °C. Small differences among treatments were observed in the post-cutting changes of color parameters and chemical composition. Based on sensory analysis, the four cut types remained marketable for up to 7 days at all tested temperatures, but only the wedges, slices, and 1/2 slices stored at 0, 2 and 5 °C preserved their sensory attributes for up to 10 days. Good retention of vitamin C (about 85% ascorbic acid and 15% dehydroascorbic acid) and antioxidant capacity were found after 10 days at 0, 2, and 5 °C. Ethanol was the main fermentative metabolite found (88% of the total) and its concentration increased by up to three-fold in slices, 1/2 and 1/4 slices after 10 days at 10 °C. Total phenolics concentrations decreased gradually throughout the storage period in all cases.     

Fixation of hybrid vigor in rice: opportunities and challenges

Rice, one of most important crops, is emerging not only as a model plant for molecular biological studies in cereal crops, but also as a model system for hybrid breeding methodologies, which include three-line system, two-line system and one-line system, corresponding to inter-varietal heterosis, inter-subspecific heterosis and heterosis of distant hybridization based on enhancing heterosis level, respectively. The developmental goal and direction of rice breeding are to simplify procedure of hybrid breeding and to enhance heterosis level. One-line breeding is not only to use distance cross for enhancing heterosis but also to lock hybrid vigor and to produce permanent hybrid. Rice of early generation stability, sporophytic apomictic rice or gametophytic apomictic rice might be used as a genetic tool for one-line breeding, and also represent three main methods and three development stages in one-line breeding.     

Enhanced grain yield in rice hybrids through complementation of fertility restoration by Rf3 and Rf4 genes as revealed by multilocation evaluation of tropical japonica derived rice (Oryza sativa) hybrids

Thirty-one tropical japonica derived Rf gene carrying rice hybrids were classified into three classes as Rf3, Rf4 and Rf3 + Rf4 hybrids. These hybrids were tested under three different mega-environments. Between Rf3 class and both the classes of hybrids possessing Rf4 genes, significant variation for spikelet and pollen fertility and grain yield was found. The pollen fertility was five times higher among Rf4 hybrids than that of hybrids carrying Rf3 alone. Likewise, spikelet fertility among Rf4 hybrids was two times higher than that of Rf3 hybrids. Parallel grain yield increase in Rf4 hybrids was 2.4 times than in Rf3 hybrids. However, Rf3 gene was found complementing Rf4 to truncate the range of pollen and spikelet fertility. Hybrids possessing Rf3 alone exhibited partial pollen and spikelet sterility, and significant negative standard heterosis for grain yield. The high yielding hybrid, “HYB36” carrying both the Rf genes was found to be widely adapted. The present study established that Rf4 gene is essential either alone or in combination with Rf3 for fertility restoration to achieve enhanced grain yield in WA-CMS based hybrids.     

“云大— 120 ”浸种对水稻秧苗素质及产量影响的研究

试验结果表明：用“云大— 120 ”浸稻种对种子的发芽势、发芽率、秧苗素质、有效穗和稻谷产量具有一定的促进作用，发芽势比对照提高 12.68% — 23.94% ；发芽率提高 3.75% — 18.75% ；有效穗提高 0.5% — 7.43% ；产量增加 1.03% — 8.49% 。其使用方法简单易行，在生产上具有重要的推广价值。     

A novel procedure for raising rice seedlings and its potential application for mass-screening of rice strains for salt tolerance

Summary A soilless culture system is described whereby all the necessary steps of raising rice seedlings, including seeding, surface-sterilization, germination and growing of seedlings, can be conveniently achieved within a small plastic container. The system is especially suited for experiments with massive number of entries and can e.g. be used for screening of rice genotypes for salt tolerance.     

Genetic organization of aromatic rice as revealed by RAPD markers: A case study in conserving crop genetic resources on farm

Summary On-farm conservation of landraces is one strategy to maintain the diversity of crop germplasm in local agro-ecosystems. The genetic structures of landraces are a key biological factor in on-farm conservation strategies. To accumulate a genetic understanding that will help establish a methodology for on-farm conservation, the genetic organization of landraces of aromatic rice in Namdinh province, Vietnam was analyzed using RAPD markers. Eighteen RAPD markers detected 38 genotypes among 320 aromatic rice samples growing at 23 sites of farmers' fields and in the experimental field that derived from 13 sites. Geographical variation was observed in the frequency of genotypes, whereas individual landraces could not be distinguished by RAPD markers. Genetic variation within a site was generally smaller than that among sites. The degree of genetic similarity of the plants in a site varied among sites, as did the number of genotypes. Changes in genetic structure over time were investigated using experimental populations each derived from approximately 30 plants from 13 farmers' fields. The differences detected by DNA markers between the genetic structural in the farmers' fields and those in experimental fields suggested that genetic drift is a major cause of these differences. The present study suggests that DNA markers are an essential means to monitor the genetic structures of heterogeneous landraces of rice, and are useful for selecting study sites for the on-farm conservation of genetic diversity as well as for successive monitoring.     

Erratum to: Biomass and nutrient accumulation by cover crops and upland rice grown in succession under no-tillage system as affected by nitrogen fertilizer rate

Journal of Crop Science and Biotechnology - Due to an unfortunate oversight the author’s name and affiliation have been given erroneously. It should be read:     

Root pulling resistance in rice: Inheritance and association with drought tolerance

Summary Avoidance of drought stress is commonly associated with root system characteristics and root development. The inheritance of root pulling resistance in rice (Oryza sativa L.) was investigated and its relationship with visual field scores for drought tolerance was studied. Transgressive segregation for high root pulling resistance was observed in 3 crosses (high x high, low x high, and intermediate x intermediate). Both dominant and additive genes control the variation. F₁ superiority for high root pulling resistance was observed and could be exploited in an F₁ hybrid breeding program. F₂ distribution curves indicated that plants highly resistant to root pulling can be obtained not only from low x high and high x high crosses, but also from intermediate x intermediate crosses. Root pulling resistance in rice has a low heritability (39 to 47%). Thus, breeding for a high root pulling resistance may best be accomplished by selection based on line means rather than individual plant selection. Field screening showed significant differences in leaf water potential among random F₃ lines. F₃ lines with higher leaf water potential had better visual scores for drought tolerance. Visual drought tolerance scores were correlated with root pulling resistance. Plants with high root pulling resistance had the ability to maintain higher leaf water potentials under severe drought stress. The usefulness of the root pulling technique in selecting drought tolerant genotypes was confirmed.     

施氮量与栽培密度对Ⅱ优航1号作再生稻产量的影响

采用两因素随机区组田间试验方法,研究氮肥施用量与栽培密度对Ⅱ优航1号作早稻再生稻栽培产量的影响。结果表明：头季施氮量、栽培密度、施氮量与栽培密度互作对头季稻产量差异极显著,但对再生季产量差异不显著。栽培密度对两季总产量差异显著。头季每公顷施纯N 150kg与栽培密度22.5~30万丛搭配和每公顷施纯N 195~240kg与栽培密度15~30万丛搭配,配套其他高产栽培措施,再生栽培能获得两季高产。再生季有效穗与头季有效穗呈显著正相关     

Towards development of Al-toxicity tolerant lines in indica rice by exploiting somaclonal variation

Somaclonal variations, induced in vitro, were used to enhance tolerance to aluminium (Al) toxicity in rice. Tolerant plants were developed through in vitro screening of embryogenic calli. The calli were derived from mature seed embryos and cultured on medium stressed with different concentrations of Al₂(SO₄)₃⋅18H₂O. Seed germination, callus induction, plantlet regeneration and callus health declined with increased concentration of Al. At higher Al concentrations, callus health deteriorated drastically with partial to total necrosis. Plantlet regeneration varied largely among varieties and treatments. The variety IR72 produced maximum plantlets among all genotypes tested. An amount of 60 ppm or more Al was highly toxic, which greatly reduced plantlet regeneration from callus. R₀ plantlets were grown under glasshouse. Based on the appearance of bronzing symptoms on leaves, the tolerant R₁ plants were selected. R₁ and R₂ lines derived from putative tolerant somaclones, were evaluated in fiberglass tanks filled with Al-toxic soil. R₃ population was evaluated in the field. A few lines derived from IR72 showed high yield and good plant type. The progenies at R₃ showed normal root growth under stressed environment in sand culture. The study revealed that in vitro screening would be an appropriate alternative to conventional breeding in evolving Al-tolerant lines as observed in case of other abiotic stresses. The technique was useful in creating de novo synthesized Al-tolerance character in rice.     

利用ORYZA2000模型分析北京地区旱稻产量潜力及需水特征

在模型验证的基础上，利用ORYZA2000模型分析表明，北京地区旱稻产量潜力30年平均为8 573 kg hm^-2，变化范围为6 747~11 278 kg hm^-2，年际间变异系数为16.3%。而雨养产量的多年平均值为4 084 kg hm^-2，变化范围223~8 018 kg hm^-2，年际间的变异系数高达51.1%。产量潜力与雨养产量之差表明北京地区旱稻尚有一定的增产潜力。旱稻全生育期需水量的多年平均值为713 mm，年际间变异为8.5%。其中，出苗—穗分化阶段由于持续时间长，需水量最大，占全生育期的49.7%。全生育期的平均需水强度为5.3 mm d^-1，需水强度最大的时期为穗分化—开花阶段，平均为5.5 mm d^-1。北京地区生育期内的降水量不能完全满足旱稻的需水要求，50%的年份水分亏缺量在250 mm以上，水分亏缺量多年平均值为226 mm，年际间变异较大，变异系数高达81.4%。     

水稻单倍体诱导基因Os MATL突变体的创制与分析

MTL基因是玉米中控制单倍体诱导性状的关键基因,该基因在作物中的功能高度保守。OsMATL是MTL在水稻中的同源基因,已有研究证实该基因的突变可以诱导水稻单倍体产生,但不同遗传背景下,OsMATL基因的突变效应有待明确。本研究以日本晴(粳稻)和华航48(籼稻)为材料,利用CRISPR/Cas9技术对OsMATL基因启动子区和编码区的不同位点进行编辑,成功获得OsMATL基因不同遗传背景系列突变体。分析了不同突变位点对结实率的影响,发现OsMATL基因编码区突变后结实率为2%~15%,且存在不同类型的败育籽粒,而启动子区域的大片段缺失对结实率没有显著影响;此外,籼稻背景突变体的结实率高于粳稻突变体。本研究创制的不同类型OsMATL突变体为进一步研究水稻孤雌生殖单倍体诱导的机制提供了基础材料。     

Ectopic expression of GmPAP3 enhances salt tolerance in rice by alleviating oxidative damage

GmPAP3, a purple acid phosphatase from soybean (Glycine max), was previously shown to alleviate salt stress in BY‐2 cells and Arabidopsis thaliana by reducing oxidative damage. To make use of GmPAP3 for crop improvement, we investigated whether the protective function of GmPAP3 is persistent in rice. Compared with the untransformed wild type, the transgenic rice plants exhibited enhanced germination rate, longer shoots and roots, and higher survival rate under salt stress, when compared to the untransformed control. In addition, the transgenic plants also showed increased activity of superoxide dismutase (SOD) and catalase (CAT), proline content, water content and chlorophyll content, but decreased electrolyte leakage and malondialdehyde content in leaves. These results indicate that the expression of GmPAP3 could be used to enhance salt tolerance in rice.     

不同机械化栽培方式下控释肥配比对迟熟中粳水稻产量形成及氮素吸收利用的影响

以优质食味粳稻南粳9108为材料,纯氮270 kg hm–2施氮条件下,设置了钵苗机插、毯苗机插2种栽培方式,将控释肥与速效氮肥以5∶5的比例混合,其中控释肥由4种不同释放期(40、80、100、和120 d)肥料按照1∶4的比例混合形成了3种配比方式,分别为40+80、40+100、40+120,同时设置常规分次施肥(CK)为对照,研究不同机械化栽培方式下控释肥配比对迟熟中粳水稻产量形成以及氮素积累的影响。结果表明,相同肥料处理下,钵苗机插2年产量较毯苗机插分别增加了3.9%和4.9%,其原因是钵苗机插能够提高中后期的光合物质积累,获得较大的穗型,具有更高的每穗粒数、结实率以及千粒重。钵苗机插与毯苗机插栽培方式下,40+80和40+100控释肥处理2年产量均高于CK, 40+100控释肥处理产量最高, 2年较CK分别显著增加7.3%和9.2%,其原因在于40+100控释肥处理具有更高的有效穗数和群体颖花量。与40+80和40+120控释肥处理相比,40+100控释肥处理与南粳9108的养分吸收规律更为匹配,即保证了前期分蘖的发生,又保证了后期稳定的光合物质生产,获得稳定的穗数、穗粒数...     

镉胁迫对不同抗性水稻品种幼苗生长和生理特性的影响

以耐镉性不同的两个水稻品种（水稻秀水63和秀水09）为试验材料,采用溶液培养方法,研究不同浓度镉（0、1、5、10、25、50、100μmol/L-1）对水稻幼苗生长和生理特性的影响。结果表明：随Cd浓度增加水稻幼苗生长明显受抑,株高、叶绿素含量、叶片干重明显下降,且秀水63的下降幅度大于秀水09。总体上,脯氨酸含量、超氧化物歧化酶（SOD）、过氧化物酶（POD）活性均呈上升趋势,其中,在较低浓度Cd胁迫下,秀水63叶片中脯氨酸含量、POD活性增加幅度较大,而在较高浓度Cd胁迫下,秀水09的增加幅度较大。过氧化氢酶（CAT）活性表现为先上升后下降。丙二醛（MDA）含量随着Cd胁迫浓度的提高而增加, 且增加幅度秀水63大于秀水09。从实验结果表明,秀水09对Cd胁迫的抗性大于秀水63。     

Spear yield and quality of white asparagus as affected by soil temperature

In three consecutive years two asparagus cultivars (Gijnlim, Grolim) were cultivated at three different temperatures in the ridge surface ranging from 12 to 26 °C to assess (1) the onset of spear yield, (2) the mean daily yield increase per plant, and (3) the establishment of spear quality defects. The objective was to determine the temperature dependence of the spear growth and quality of white asparagus with respect to different cultivars and the harvest year.

The mean time interval Δt from the beginning of the temperature treatment to harvest start was 16.5 d at the reference temperature of 20 °C. This time interval corresponded to a thermal time of 255 °C d at a base temperature of 4.4 °C. The mean yield increase per plant at the reference temperature was 17.4 g d⁻¹. The temperature dependence of Δt and was expressed by the relative change of these quantities per 1 °C alteration, which were on average 0.08 and 0.14 °C⁻¹, respectively. The frequency of quality defects (rusted spears, split spears, hollow/club-shaped spears, spears with open heads) and grade I quality depended significantly (P < 0.05) on the temperature, cultivar, and harvest year. Generally, ‘Gijnlim’ showed fewer quality defects than ‘Grolim’, whereas spears without defects were most frequent for those grown between 18 and 22 °C. With rising temperatures, the frequency of split or hollow/club-shaped spears and spears with open heads increased, while the frequency of rusted spears decreased. The derived functions of yield and quality parameters should improve the controlling of the yield and quality of white asparagus spears at varying temperatures in the ridge.