[Nie, XZ ] Agr & Agri Food Canada, Potato Res Ctr, POB 20280,850 Lincoln Rd, Fredericton, NB E3B 4Z7, Canada.;Agr & Agri Food Canada, Potato Res Ctr, POB 20280,850 Lincoln Rd, Fredericton, NB E3B 4Z7, Canada.
A previous study has identified two types of recombinant variants of Potato virus Y strain NTN (PVYNTN) in China and sequenced the complete genome of the variant PVYNTN-HN2. In this study, the complete genome of isolate PVYNTN-HN1 was fully sequenced and analyzed. The most striking difference between the two variants was the location of recombinant joint three (RJ3). In PVYNTN-HN1, like other typical European-PVYNTN isolates such as PVYNTN-Hun, the RJ3 was located at nucleotide (nt) 9183, namely the 3' proximal end of the CP gene (nt. 8571-9371), thus leading to most (the first 613 nucleotides from the 5' proximal end) of the CP gene (801 bp) with a PVYN origin and PVYN-serotype; whereas in contrast, the RJ3 in PVYNTN-HN2 was located at nt 8572, consequently leading to a CP gene of PVYO origin and PVYO-serotype. The varied genome composition among PVYO, PVYN, PVYN:O, PVYNTN-HN1 and PVYNTN-HN2 made them useful for the investigation of possible roles of gene segment(s) in symptom formation on host plants. When Physalis floridana plants were infected with different PVY isolates, two types of symptoms were induced. PVYN and PVYNTN-HN1 induced mild symptoms (mainly mild mottling) whereas PVYO, PVYN:O and PVYNTN-HN2 induced serve symptoms including leaf and stem necrosis, leaf-drop and stunting. These results, together with a previous study using artificial PVY chimeras, demonstrate that the CP gene, especially the 5' proximal segment (nt 8572-9183), and/or CP likely determine the pathogenicity of PVY in P. floridana.
Agronomic management;Grain yield;Nitrogen fertilizer use efficiency;Nitrogen partitioning;Radiation use efficiency;Super rice hybrid
Options to increase resource use efficiency and climatic yield potential of locally adapted super rice hybrids including combined water, nutrient and other agronomic management are limited. Hence, the aim of our three-year (six seasons) experiments during early-season (ESR; Luliangyou996) and late-season (LSR; C-liangyou396) rice in southern China was to identify key yield parameters and optimum resource use options to enhance the crop's climatic yield potential. Grain yield averaged across all three years with effective N management combined with post-anthesis shallow wetting and drying was 32.8% and 37.1% higher than the normal farmers’ practice in Liuyang County in ESR and LSR, respectively. More spikelets m−2 were the key to achieving high yield potential, further supported by increased leaf area index and high radiation interception and internal use efficiency. The split application of nitrogen in combination with shallow wetting and drying allowed for better N uptake, use efficiency and partitioning, leading to enhanced biomass and yield. The high yield potential, however, was not just a function of genetics and management but also depended on the climatic conditions prevailing, particularly temperature and radiation. In ESR, lower temperature during vegetative stage reduced overall biomass and sink size while subsequent higher temperature reduced the total grain filling period by 17 days compared with LSR, indicating a climatic condition-driven decline in yield potential rather than lower genetic potential of the super hybrids. A lack of correlation of spikelets panicle−1 and spikelets m−2 with grain-filling percentage in LSR provided evidence that a larger sink does not necessarily result in poor grain filling when sufficient time and assimilates for grain filling are provided, which is more climate dependent. Our work highlights the benefits of integrating nutrient, water and agronomic management options to achieve high NUE and grain yield.
Expression profiles of 12 class A rice heat shock transcription factor genes (OsHsfAs) were analyzed by semi-quantitative reverse transcriptase polymerase chain reaction. The OsHsfA genes exhibited tissue-specific expressions under normal condition. OsHsfA1a, A2d, and A9 were predominantly expressed in young spike. Expression responses of the 12 OsHsfAs under abiotic stresses were analyzed in the shoots of rice seedling. Most OsHsfA genes responded quickly to heat stress except for OsHsfA1a, A3, and A9 which were almost unaffected. In particular, OsHsfA2a expression in response to heat stress was highest among the heat shock factors examined. However, the majority of the increased OsHsfAs expression responses to salt, polyethylene glycol (PEG), and cold treatments primarily occurred during the later stages (3 to 24 h) of stress exposure. Furthermore, most of OsHsfA gene expressions were little affected and only a few (OsHsfA3, A4d, A7, and A9) genes had slow responses to cold treatment. The results indicate that the transcript levels of OsHsfAs during heat stress exposure were distinct from those of plants subjected to salt, PEG, and cold stresses, suggesting that there might be different regulatory networks between heat and non-heat stress.
Brassica juncea, a worldwide cultivated crop plant, produces seeds of different colors. Seed pigmentation is due to the deposition in endothelial cells of proanthocyanidins (PAs), end products from a branch of flavonoid biosynthetic pathway. To elucidate the gene regulatory network of seed pigmentation in B. juncea, transcriptomes in seed coat of a yellow-seeded inbred line and its brown-seeded near- isogenic line were sequenced using the next-generation sequencing platform Illumina/Solexa and de novo assembled. Over 116 million high-quality reads were assembled into 69,605 unigenes, of which about 71.5% (49,758 unigenes) were aligned to Nr protein database with a cut-off E-value of 10(-5). RPKM analysis showed that the brown-seeded testa up-regulated 802 unigenes and down-regulated 502 unigenes as compared to the yellow-seeded one. Biological pathway analysis revealed the involvement of forty six unigenes in flavonoid biosynthesis. The unigenes encoding dihydroflavonol reductase (DFR), leucoantho-cyanidin dioxygenase (LDOX) and anthocyanidin reductase (ANR) for late flavonoid biosynthesis were not expressed at all or at a very low level in the yellow-seeded testa, which implied that these genes for PAs biosynthesis be associated with seed color of B. juncea, as confirmed by qRT-PCR analysis of these genes. To our knowledge, it is the first time to sequence the transcriptome of seed coat in Brassica juncea. The unigene sequences obtained in this study will not only lay the foundations for insight into the molecular mechanisms underlying seed pigmentation in B. juncea, but also provide the basis for further genomics research on this species or its allies.
[Jagadish, Krishna S. V.; Shi, Wanju; Oane, Rowena] Int Rice Res Inst, Manila, Philippines.;[Jagadish, Krishna S. V.; Craufurd, Peter] Univ Reading, Plant Environm Lab, Reading RG2 9AF, Berks, England.;[Craufurd, Peter] Int Crops Res Inst Semi Arid Trop, Patancheru 502324, Andhra Pradesh, India.;[Shi, Wanju] Hunan Agr Univ, Coll Agron, Changsha 410128, Hunan, Peoples R China.;[Jagadish, Krishna S. V.] Int Rice Res Inst, DAPO Box 7777, Manila, Philippines.
[Jagadish, Krishna S. V.] Int Rice Res Inst, DAPO Box 7777, Manila, Philippines.
flag leaf;heat stress;microsporogenesis;rice;spikelet;tetrad formation
Gametogenesis in rice (Oryza sativa L.), and particularly male gametogenesis, is a critical developmental stage affected by different abiotic stresses. Research on this stage is limited, as flowering stage has been the major focus for research to date. Our main objective was to identify a phenotypic marker for male gametogenesis and the duration of exposure needed to quantify the impact of heat stress at this stage. Spikelet size coinciding with microsporogenesis was identified using parafilm sectioning, and the panicle (spikelet) growth rate was established. The environmental stability of the marker was ascertained with different nitrogen (75 and 125kg ha(-1)) and night temperature (22 degrees C and 28 degrees C) combinations under field conditions. A distance of -8 to -9cm between the collar of the last fully opened leaf and the flag leaf collar, which was yet to emerge was identified as the environmentally stable phenotypic marker. Heat stress (38 degrees C) imposed using the identified marker induced 8-63% spikelet sterility across seven genetically diverse rice genotypes. Identifying the right stage based on the marker information and imposing 6 consecutive days of heat stress ensures that >95% of the spikelets in a panicle are stressed spanning across the entire microsporogenesis stage.
Tillering ability is one of the most important traits of the rice plant because it plays a major role in determining grain yield. However, it is not clear whether rice yield potential could be further increased if unproductive tillers were reduced or eliminated. Two field experiments were conducted to determine the effects of tiller reduction on plant growth and grain yield in two varieties with different tillering ability. Two methods were used to reduce tillers: the first was the removal of tillers manually at different crop growth stages and the second was to grow rice plants through holes in styrofoam slats, which provided a physical restriction on tiller emergence. Tiller number declined by 12–57% with the first method and by 18–47% with the second method compared with the control. Despite the significant reduction in tiller number and unproductive tiller percentage, none of the treatments with manual tiller removal and physical restriction of tillering resulted in a significant increase in grain yield compared with the control. Decreases in leaf area and biomass at heading and panicle number at maturity were observed when tiller number declined significantly, but grain yield was not necessarily reduced because it was compensated for by more biomass production after heading and increased spikelet number per panicle. The two varieties with different tillering ability had similar responses to tiller reduction. Based on the two methods of tiller reduction used in this study, we conclude that a further increase in rice yield potential may not be possible by reducing or eliminating unproductive tillers.
Hemibiotrophic pathogens are some of the most destructive plant pathogens, causing huge economic losses and threatening global food security. Infection with these organisms often involves an initial biotrophic infection phase, during which the pathogen spreads in host tissue asymptomatically, followed by a necrotrophic phase, during which host-cell death is induced. How hemibiotrophic pathogens trigger host necrosis and how plants inhibit the transition from the biotrophic stage to the necrotrophic stage in disease symptom expression are mainly unknown. The rice blast fungus Magnaporthe oryzae spreads in rice biotrophically early during infection, but this biotrophic stage is followed by a pronounced switch to cell death and lesion formation. Here, we show that the M. oryzae effector AvrPiz-t interacts with the bZIP-type transcription factor APIP5 in the cytoplasm and suppresses its transcriptional activity and protein accumulation at the necrotrophic stage. Silencing of APIP5 in transgenic rice leads to cell death, and the phenotype is enhanced by the expression of AvrPiz-t. Conversely, Piz-t interacts with and stabilizes APIP5 to prevent necrosis at the necrotrophic stage. At the same time, APIP5 is essential for Piz-t stability. These results demonstrate a novel mechanism for the suppression of effector-triggered necrosis at the necrotrophic stage by an NLR receptor in plants.
Journal of Integrative Agriculture,2011年11(1):134-143 ISSN：2095-3119
[Yang Sheng-hai; Qin Jian-quan; Chen Li-jun; Tang Qi-yuan; Zhang Yun-bo; Li Di-qin; Zou Ying-bin; Li Hu] Hunan Agr Univ, State Key Lab Hybrid Rice, Changsha 410128, Hunan, Peoples R China.;[Peng Shao-bing] Huazhong Agr Univ, CPPC, Wuhan 430070, Peoples R China.
[Tang Qi-yuan] Hunan Agr Univ, State Key Lab Hybrid Rice, Changsha 410128, Hunan, Peoples R China.
super hybrid rice;real-time N management;fixed-time adjustable-does N management;grain yield;sheath blight;radiation use efficiency;agronomic-nitrogen use efficiency
Poor nitrogen use efficiency in rice production is a critical issue in China. Site-specific N managements (SSNM) such as real-time N management (RTNM) and fixed-time adjustable-dose N management (FTNM) improve fertilizer-N use efficiency of irrigated rice. This study was aimed to compare the different nitrogen (N) rates and application methods (FFP, SSNM, and RTNM methods) under with- and without-fungicide application conditions on grain yield, yield components, solar radiation use efficiency (RUE), agronomic-nitrogen use efficiency (AEN), and sheath blight disease intensity. Field experiments were carried out at Liuyang County, Hunan Province, China, during 2006 and 2007. A super hybrid rice Liangyou 293 (LY293) was used as experimental material. The results showed that RTNM and SSNM have great potential for improving agronomic-nitrogen use efficiency without sacrificing the grain yield. There were significant differences in light interception rate, sheath blight disease incidence (DI) and the disease index (ShBI), and total dry matter among the different nitrogen management methods. The radiation use efficiency was increased in a certain level of applied N. But, the harvest index (HI) decreased with the increase in applied N. There is a quadratic curve relationship between grain yield and applied N rates. With the same N fertilizer rate, different fertilizer-N application methods affected the RUE and grain yield. The fungicide application not only improved the canopy light interception rate, RUE, grain filling, and harvest index, but also reduced the degree of sheath blight disease. The treatment of RTNM under the SPAD threshold value 40 obtained the highest yield. While the treatment of SSNM led to the highest nitrogen agronomic efficiency and higher rice yield, and decreased the infestation of sheath blight disease dramatically as well. Nitrogen application regimes and diseases control in rice caused obvious effects on light interception rate, RUE, and HI. Optimal N rate is helpful to get higher light interception rate, RUE, and HI. Disease control with fungicide application decreased and delayed the negative effects of the high N on rice yield formation. SSNM and RTNM under the proper SPAD threshold value obtained high-yield with high efficiency and could alleviate environmental pollution in rice production.
Rice production in China has been constrained by changes in socioeconomic and physical environments such as decreased labor availability and degraded soil. No-tillage (NT) may be an alternative system for rice production in China because it has potential benefits including labor saving and soil conservation. Here, we conducted a meta-analysis to evaluate the effect of NT on rice yield in China and to investigate how the effect varies with the environmental and management factors. Results showed that decrease in panicle number per unit land area was observed in NT rice across a wide range of environmental and management conditions in China, but grain yield was not reduced because it was compensated for by more spikelet number per panicle and higher spikelet-filling percentage. Grain yield responses to NT were affected by region (climate), soil, cropping system and proportion of N applied during the vegetative period (PNVP). Typically, grain yield showed a positive response to NT in south-west region (where the climate during rice-growing season is characterized by frequent fog and clouds, high humidity and insufficient sunlight). NT resulted in a decreased grain yield in soils with pH lower than 6.0 and low fertility. Grain yield was decreased in rice-rice cropping systems but increased in rice-upland cropping systems by NT. NT had negative effect on grain yield under PNVP of 70% and 80% but had no significant effect under PNVP of 90%. However, responses of grain yield to NT did not vary with establishment method (transplanting vs. seedling throwing vs. direct seeding), cultivar type (hybrid vs. inbred), duration of NT adoption (<3 years vs. 3-6 years vs. >6 years) and residue management practice (removal vs. retention). We conclude that adoption of NT for rice production in China should be site-specific and depend on agronomic practices including cropping system and N management. (C) 2015 Elsevier B.V. All rights reserved.