土壤中的氮素分布不均，在氮素富集的土壤区域内，植物根系大量的生长。然而，不同玉米基因型根系对局部施氮的响应与氮素吸收效率之间的关系尚不清楚。本研究以4个玉米品种为研究对象，探讨根系生长对局部施氮响应的基因型差异及对氮素吸收的影响。在水培采用分根培养体系局部供氮，在田间采用条施和穴施的局部施氮方法。结果表明，不同品种根系局部氮响应在水培和田间条件之间具有高度相关性（r>0.99）。在水培局部供氮条件下，强响应品种郑单958、先玉335和先锋32D22的侧根长增加了50-63%，根系生物量增加了36-53%，而弱响应品种蠡玉13的根系生长响应较小。田间条件下，3个强响应品种的根长在40-60 cm土层显著增加66-75%，而蠡玉13的根长变化幅度显著较低。此外，局部施氮肥促进强响应品种的花后氮吸收，增幅达16-88%，并且促进了郑单958的籽粒产量显著增加10-12%。相关分析发现，产量与40-60 cm土层根长呈显著正相关（r=0.39）。综上所述，可在苗期鉴定玉米品种对局部施氮的响应类型，生产中强响应型玉米品种与局部施用氮肥配套应用；同时可将“根系局部施氮响应能力”作为玉米氮高效遗传改良的目标性状。

为鉴定和利用武都白茧的抗条锈病基因，本研究将武都白茧与高感条锈病品种铭贤169杂交，分别于2015年和2016年在陕西杨凌和甘肃天水四个环境中对武都白茧、铭贤169和以及铭贤169/武都白茧杂交F_2:3代家系进行成株期抗条锈病测试。田间多年多点鉴定结果表明，武都白茧表现稳定的成株期抗条锈性，铭贤169/武都白茧F_2:3代在2015年杨凌、2016年杨凌、2015年天水和2016年天水四个环境下的相对病害曲线下面积（rAUDPC）均呈连续分布，表明武都白茧对条锈病的成株期抗性由多个QTL控制。利用集群分离分析法结合小麦660K SNP芯片、KASP和SSR标记鉴定与抗性位点连锁的多态性标记，运用完备区间作图法（BIP）和多环境表型鉴定数据（MET）两种QTL技术方法，检测到两个稳定的QTLs：QYrwdbj.nwafu-5A与QYrwdbj.nwafu-2B.1 。其中QYrwdbj.nwafu-5A位于小麦染色体5AS的缺失系5AS1-0.40-0.75和5AS3-0.75-0.98相邻的区域，解释15.02%-40.26%的表型变异；QYrwdbj.nwafu-2B.1位于小麦染色体2BS的缺失系C-2BS1-0.53上，解释9.54%-10.40%的表型变异。通过分子检测、抗病基因染色体定位和上位性分析表明，QYrwdbj.nwafu-5A很可能是一个需要与其它位点结合互作才能发挥抗条锈作用的新QTL。本研究将为进一步克隆武都白茧主效QTL，以及利用武都白茧主效QTL与其他有效抗条锈病基因或者QTL结合，培育持久抗条锈病品种提供科学依据。本研究的创新点是考虑环境对QTL的加性效应，从而提供QTL位置和效应方面更为全面遗传分析。

籽粒水分关系在玉米籽粒灌浆过程中起着重要作用。本试验以不同氮效率的杂交种为材料，在不同氮肥水平下了解玉米籽粒干重和水分关系的变化。本研究的目的是:1)了解不同施氮量对籽粒发育过程中干物质和含水率的影响，2)确定施氮是否通过调节籽粒水分关系的变化来影响籽粒灌浆。两个玉米杂交种，氮高效品种ZH311和氮低效品种XY508，在三个生长季，四种氮肥水平下生长:0、150、300和450kg N ha^-1。研究了基-中粒和顶粒的干重、含水率和含水量。玉米穗基-中粒和顶粒的最大灌浆速率和灌浆持续时间的差异导致最终粒重的显著差异。籽粒位置显著影响籽粒的干燥，顶粒的干燥速率比基-中粒的干燥速率快。基因型和粒位都影响施氮量对籽粒灌浆和干燥的影响。施氮量决定了籽粒灌浆中后期最大籽粒含水量和含水率的损失速率，从而影响最终粒重。氮高效杂交种的使用，结合氮肥施用量的减少，可以在保证产量的基础上，协调基-中粒和顶粒的干燥。这种管理策略可能会带来双赢的局面，即最大玉米产量、高效的机械收获和环境安全同时得到提高。

甘薯(Ipomoea batatas (L.) Lam.)作为一种重要的杂粮作物，在世界各地广泛种植，但深受甘薯病毒病(SPVD)的影响。本研究利用短串联靶标模拟物（STTM）成功抑制甘薯miR397的表达，上调其靶基因漆酶（IbLACs）的表达，使木质素合成途径的上游基因，包括苯丙氨酸解氨酶（PAL）、4-香豆酸辅酶A连接酶（4CL）、羟基肉桂酰CoA:莽草酸/奎宁酸羟基肉桂酰转移酶（HTC）、咖啡酸O-甲基转移酶（COMT）、肉桂醇脱氢酶(CAD)等基因被反馈调控而广泛上调表达。同时，导致PAL和LAC的酶活性显著增加，促进木质素的合成与积累。木质素在细胞壁中的沉积增加了转基因甘薯植株的物理防御能力，有效减少了烟粉虱对SPVD的传播，保证甘薯的健康生长。本研究为甘薯抗病育种和绿色生产提供了新思路。

Nitrogen (N) is a critical element for plant growth and productivity that influences photosynthesis and chlorophyll fluorescence. We investigated the effect of low-N stress on leaf photosynthesis and chlorophyll fluorescence characteristics of maize cultivars with difference in tolerance to low N levels. The low-N tolerant cultivar ZH311 and low-N sensitive cultivar XY508 were used as the test materials. A field experiment (with three N levels: N0, 0 kg ha^–1; N1, 150 kg ha^–1; N2, 300 kg ha^–1) in Jiyanyang, Sichuan Province, China, and a hydroponic experiment (with two N levels: CK, 4 mmol L^–1; LN, 0.04 mmol L^–1) in Chengdu, Sichuan Province, China were conducted. Low-N stress significantly decreased chlorophyll content and rapid light response curves of the maximum fluorescence under light (F_m´), fluorescence instable state (F_s), non-photochemical quenching (q_N), the maximum efficiency of PSII photochemistry under dark-adaption (F_v/F_m), potential activity of PSII (F_v/F_o), and actual photochemical efficiency of PSII (ΦPSII) of leaves. Further, it increased the chlorophyll (Chl) a/Chl b values and so on. The light compensation point of ZH311 decreased, while that of XY508 increased. The degree of variation of these indices in low-N tolerant cultivars was lower than that in low-N sensitive cultivars, especially at the seedling stage. Maize could increase Chl a/Chl b, apparent quantum yield and light saturation point to adapt to N stress. Compared to low-N sensitive cultivars, low-N tolerant cultivars maintained a higher net photosynthetic rate and electron transport rate to maintain stronger PSII activity, which further promoted the ability to harvest and transfer light. This might be a photosynthetic mechanism by which low-N tolerant cultivar adapt to low-N stress.

Heat stress seriously affects wheat production in many regions of the world.  At present, heat tolerance research remains one of the least understood fields in wheat genetics and breeding and there is a lack of effective methods to quantify heat stress and heat tolerance in different wheat cultivars.  The objective of this study was to use various wheat cultivars to evaluate stress intensity (δ) and a new method for quantification of heat tolerance and compare this technique with three other currently utilized methods.  This new parameter for heat tolerance quantification is referred to as the heat tolerance index (HTI) and is an indicator of both yield potential and yield stability.  Heat treatments were applied in a controlled setting when anthesis had been reached for 80% of the wheat.  The stress intensity evaluation indicated heat shock was the main factor associated with kernel weight reduction while grain yield reduction was mainly associated with chronic high temperature.  The methods evaluation showed that a temperature difference of 5°C from natural temperatures was a suitable heat treatment to compare to the untreated controls.  HTI was positively correlated with yield under heat stress (r=0.8657, δ₂₀₁₀=0.15, in 2009–2010; r=0.8418, δ₂₀₁₁=0.20, in 2010–2011; P<0.01), and negatively correlated with yield reduction rate (r=–0.8344, in 2009–2010; r=–0.7158, in 2010–2011; P<0.01).  The results of this study validated the use of HTI and temperature difference control for quantifying wheat heat tolerance that included the yield potential and the stability of different wheat cultivars under heat stress.  Additionally, 10 wheat cultivars showed high HTI and should be further tested for their heat confirming characteristics for use in wheat heat tolerance breeding.

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is one of the most damaging diseases to wheat in the world.  The cultivation of resistant varieties of wheat is essential for controlling the powdery mildew epidemic.  Wheat landraces are important resources of resistance to many diseases.  Mapping powdery mildew resistance genes from wheat landraces will promote the development of new varieties with disease resistance.  The Chinese wheat landrace Baiyouyantiao possesses characteristic of disease resistance to powdery mildew.  To identify the resistance gene in this landrace, Baiyouyantiao was crossed with the susceptible cultivar Jingshuang 16 and seedlings of parents and F₁, BC₁, F₂, and F_2:3 were tested with Bgt isolate E09.  The genetic results showed that the resistance of Baiyouyantiao to E09 was controlled by a single recessive gene, tentatively designated PmBYYT.  An Illumina wheat 90K single-nucleotide polymorphism (SNP) array was applied to screen polymorphisms between F₂-resistant and F₂-susceptible DNA bulks for identifying the chromosomal location of PmBYYT.  A high percentage of polymorphic SNPs between the resistant and susceptible DNA bulks was found on chromosome 7B, indicating that PmBYYT may be located on this chromosome.  A genetic linkage map of PmBYYT consisting of two simple sequence repeat markers and eight SNP markers was developed.  The two flanking markers were SNP markers W7BL-8 and W7BL-15, with genetic distances of 3 and 2.9 cM, respectively.  The results of this study demonstrated the rapid characterization of a wheat disease resistance gene and SNP marker development using the 90K SNP assay.  The flanking markers of gene PmBYYT will benefit marker-assisted selection (MAS) and map-based cloning in breeding wheat cultivars with powdery mildew resistance.

Even though the impact of Bacillus thuringiensis (Bt) cotton on pesticide use has been well documented, all previous studies focus on the mean value of pesticide use.  Using seven unique waves of panel data collected between 1999 and 2012 in China, we show that Bt cotton adoption has not only caused a reduction of the mean value of pesticide use, but also a reduction of the standard deviation of pesticide use.  We conclude that Bt technology adoption has also contributed to the stability of pesticide use in cotton production.  We believe that this contribution is theoretically and practically relevant because of the long length of our unique dataset.

Soil salinity causes the negative effects on the growth and yield of crops. In this study, two sweet potato (Ipomoea batatas L.) cultivars, Xushu 28 (X-28) and Okinawa 100 (O-100), were examined under 50 and 100 mmol L^–1 NaCl stress. X-28 cultivar is relatively high salt tolerant than O-100 cultivar. Interestingly, real-time quantitative polymerase chain reaction (RT-qPCR) results indicated that sweet potato high-affinity K⁺ transporter 1 (IbHKT1) gene expression was highly induced by 50 and 100 mmol L^–1 NaCl stress in the stems of X-28 cultivar than in those of O-100 cultivar, but only slightly induced by these stresses in the leaves and fibrous roots in both cultivars. To characterize the function of IbHKT1 transporter, we performed ion-flux analysis in tobacco transient system and yeast complementation. Tobacco transient assay showed that IbHKT1 could uptake sodium (Na⁺). Yeast complementation assay showed that IbHKT1 could take up K⁺ in 50 mmol L^–1 K⁺ medium without the presence of NaCl. Moreover, Na⁺ uptake significantly increased in yeast overexpressing IbHKT1. These results showed that IbHKT1 transporter could have K⁺-Na⁺ symport function in yeast. Therefore, the modes of action of IbHKT1 in transgenic yeast could differ from the mode of action of the other HKT1 transporters in class I. Potentially, IbHKT1 could be used to improve the salt tolerance nature in sweet potato.

The information of single nucleotide polymorphisms (SNPs) is quite unknown in sweetpotato.  In this study, two sweetpotato varieties (Xushu 18 and Xu 781) were sequenced by Illumina technology, as well as de novo transcriptome assembly, functional annotation, and in silico discovery of potential SNP molecular markers.  Tetra-primer Amplification Refractory Mutation System PCR (ARMS-PCR) is a simple and sufficient method for detecting different alleles in SNP locus.  Total 153 sets of ARMS-PCR primers were designed to validate the putative SNPs from sequences.  PCR products from 103 sets of primers were different between Xu 781 and Xushu 18 via agarose gel electrophoresis, and the detection rate was 67.32%.  We obtained the expected results from 32 sets of primers between the two genotypes.  Furthermore, we ascertained the optimal annealing temperature of 32 sets of primers.  These SNPs might be used in genotyping, QTL mapping, or marker-assisted trait selection further in sweetpotato.  To our knowledge, this work was the first study to develop SNP markers in sweetpotato by using tetra-primer ARMS-PCR technique.  This method was a simple, rapid, and useful technique to develop SNP markers, and will provide a potential and preliminary application in discriminating cultivars in sweetpotato.

Sweetpotato (Ipomoea batatas (L.) Lam.) breeding is challenging due to its genetic complexity. In the present study, interval mapping (IM) and multiple quantitative trait locus (QTL) model (MQM) analysis were used to identify QTLs for starch content with a mapping population consisting of 202 F1 individuals of a cross between Xushu 18, a cultivar susceptible to stem nematodes, with high yield and moderate starch, and Xu 781, which is resistant to stem nematodes, has low yield and high starch content. Six QTLs for starch content were mapped on six linkage groups of the Xu 781 map, explaining 9.1-38.8% of the variation. Especially, one of them, DMFN_4, accounted for 38.8% of starch content variation, which is the QTL that explains the highest phenotypic variation detected to date in sweetpotato. All of the six QTLs had a positive effect on the variation of the starch content, which indicated the inheritance derived from the parent Xu 781. Two QTLs for starch content were detected on two linkage groups of the Xushu 18 map, explaining 14.3 and 16.1% of the variation, respectively. They had a negative effect on the variation, indicating the inheritance derived from Xu 781. Seven of eight QTLs were co-localized with a single marker. This is the first report on the development of QTLs co-localized with a single marker in sweetpotato. These QTLs and their co-localized markers may be used in marker-assisted breeding for the starch content of sweetpotato.

Stripe rust (yellow rust), caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating diseases of wheat throughout the world. H9020-1-6-8-3 is a translocation line originally developed from interspecific hybridization between wheat line 7182 and Psathyrostachys huashanica Keng and is resistant to most Pst races in China. To identify the resistance gene(s) in the translocation line, H9020-1-6-8-3 was crossed with susceptible cultivar Mingxian 169, and seedlings of the parents, F1, F2, F3, and BC1 generations were tested with prevalent Chinese Pst race CYR32 under controlled greenhouse conditions. The results indicated that there is a single dominant gene, temporarily designated as YrH9020a, conferring resistance to CYR32. The resistance gene was mapped by the F2 population from Mingxian 169/H9020-1-6-8-3. It was linked to six microsatellite markers, including Xbarc196, Xbarc202, Xbarc96, Xgpw4372, Xbarc21, and Xgdm141, flanked by Xbarc96 and Xbarc202 with at 4.5 and 8.3 cM, respectively. Based on the chromosomal locations of these markers and the test of Chinese Spring (CS) nullitetrasomic and ditelosomic lines, the gene was assigned to chromosome 6D. According to the origin and the chromosomal location, YrH9020a might be a new resistance gene to stripe rust. The flanking markers linked to YrH9020a could be useful for marker-assisted selection in breeding programs.

Stripe rust, caused by Puccinia striiformis Westend. f. sp. tritici (Pst), is a severe foliar disease of common wheat (Triticum aestivum L.) in the world. Resistance is the best approach to control the disease. The winter wheat cultivar Lantian 1 has high-temperature resistance to stripe rust. To determing the gene(s) for the stripe rust resistance, Lantian 1 was crossed with Mingxian 169 (M169). Seedlings of the parents, and F1, F2 and F2-3 progenies were tested with races CYR32 of Pst under controlled greenhouse conditions. Lantian 1 has a single partially dominant gene conferred resistance to race CYR32, designated as YrLT1. Simple sequence repeat (SSR) techniques were used to identify molecular markers linked to YrLT1. A linkage group of five SSR markers was constructed for YrLT1 using 166 F2 plants. Based on the SSR marker consensus map and the position on wheat chromosome, the resistance gene was assigned on chromosome 2DL. Amplification of a set of nulli-tetrasomic Chinese Spring lines with SSR marker Xwmc797 confirmed that the resistance gene was located on the long arm of chromosome 2D. Because of its chromosomal location and the high-temperature resistance, this gene is different from previously described genes. The molecular map spanned 29.9 cM, and the genetic distance of two close markers Xbarc228 and Xcfd16 to resistance gene locus was 4.0 and 5.7 cM, respectively. The polymorphism rates of the flanking markers in 46 wheat lines were 2.1 and 2.1%, respectively; and the two markers in combination could distinguish the alleles at the resistance locus in 97.9% of tested genotypes. This new gene and flanking markers should be useful in developing wheat cultivars with high level and possible durable resistance to stripe rust.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most widespread and destructive wheat diseases in many wheat-growing regions of the world. The winter wheat translocation line H9014-14-4-6-1 has all stage resistance. To identify stripe rust resistance genes, the segregating populations were developed from the cross between H9014-14-4-6-1 and Mingxian 169 (a wheat cultivar susceptible to all Pst races identified in China). The seedlings of the parents and F1 plants, F2, F3 and BC1 generations were tested with Pst races under controlled greenhouse conditions. Two genes for resistance to stripe rust were identified, one dominant gene conferred resistance to SUN11-4, temporarily designated YrH9014 and the other recessive gene conferred resistance to CYR33. The bulked segregant analysis and simple sequence repeat (SSR) markers were used to identify polymorphic markers associated with YrH9014. Seven polymorphic SSR markers were used to genotype the F2 population inoculated with SUN11-4. A linkage map was constructed according to the genotypes of seven SSR markers and resistance gene. The molecular map spanned 24.3 cM, and the genetic distance of the two closest markers Xbarc13 and Xbarc55 to gene locus was 1.4 and 3.6 cM, respectively. Based on the position of SSR marker, the resistance gene YrH9014 was located on chromosome arm 2BS. Amplification of a set of nulli-tetrasomic Chinese Spring lines with SSR marker Xbarc13 indicated that YrH9014 was located on chromosome 2B. Based on chromosomal location, the reaction patterns and pedigree analysis, YrH9014 should be a novel resistance gene to stripe rust. This new gene and flanking markers got from this study should be useful for marker-assisted selection (MAS) in breeding programs for stripe rust.

Sequence-related amplification polymorphism (SRAP) markers closely linked to stem nematode resistance gene were developed in sweetpotato, Ipomoea batatas (L.) Lam. Using bulked segregant analysis (BSA), 200 SRAP primer combinations were screened with the resistant and susceptible bulked DNA from the 196 progenies of an F1 single-cross population of resistant parent Xu 781×susceptible parent Xushu 18, 77 of them showed polymorphic bands between resistant and susceptible DNA. Primer combinations detecting polymorphism between the two bulks were used to screen both parents and 10 individuals from each of the bulks. The results showed that primer combination A9B4 produced 3 specific bands in the resistant plants but not in the susceptible plants, suggesting that the markers, named Nsp1, Nsp2 and Nsp3, respectively, linked to a gene for stem nematode resistance. Primer combination A3B6 also produced a SRAP marker named Nsp4 linking to the resistance gene. Amplified analysis of the 196 F1 individuals indicated that the genetic distance between these markers and the resistance gene was 4.7, 4.7, 6.3, and 9.6 cM, respectively.

The free putrescine (Put) content, the hydrogen peroxide (H2O2) content and the polyamine oxidase (PAO) activity in roots of Malus hupehensis Rehd. var. pinyiensis Jiang (PYTC) were significantly increased, and reached its peak at 1, 2 and 6 h, respectively, under cadmium treatment. The free spermine (Spm) and spermidine (Spd) contents were dramatically decreased, and reached the minimum value at 4-6 h, then remained relatively stable. The change in total free polyamines (PAs) content was consistent with that of free Put. The number of root dead cells was gradually increased after treatment for 24 h, and the typical characteristics of programmed cell death (PCD) were displayed at 48 h. Throughout the Cd treatment process, changes in PAs metabolism appeared to be prior to cell death increase, and the H2O2 content was always maintained at a high level. These results indicated that polyamines could initiate cell death by generating H2O2 in roots of Malus hupehensis Rehd. under CdSO4 stress.