Physiological and Transcriptome Analysis Illuminates the Molecular Mechanisms of the Drought Resistance Improved by Alginate Oligosaccharides in Triticum aestivum L.

Alginate oligosaccharides(AOS)enhance drought resistance in wheat(Triticum aestivum L.),but the definite mechanisms remain largely unknown.The physiological and transcriptome responses of wheat seedlings treated with AOS were analyzed under drought stress simulated with polyethylene glycol-6000.The results showed that AOS promoted the growth of wheat seedlings and reduced oxidative damage by improving peroxidase and superoxide dismutase activities under drought stress.A total of 10,064 and 15,208 differentially expressed unigenes(DEGs)obtained from the AOS treatment and control samples at 24 and 72 h after dehydration,respectively,were mainly enriched in the biosynthesis of secondary metabolites(phenylpropanoid biosynthesis,flavonoid biosynthesis),carbohydrate metabolism(starch and sucrose metabolism,carbon fixation in photosynthetic organisms),lipid metabolism(fatty acid elongation,biosynthesis of unsaturated fatty acids,alpha-linolenic acid metabolism,cutin,suberine and wax biosynthesis),and signaling transduction pathways.The up-regulated genes were related to,for example,chlorophyll a-b binding protein,amylosynthease,phosphotransferase,peroxidase,phenylalanine ammonia lyase,flavone synthase,glutathione synthetase.Signaling molecules(including MAPK,plant hormones,H_(2)O_(2) and calcium)and transcription factors(mainly including NAC,MYB,MYB-related,WRKY,bZIP family members)were involved in the AOS-induced wheat drought resistance.The results obtained in this study help underpin the mechanisms of wheat drought resistance improved by AOS,and provides a theoretical basis for the application of AOS as an environmentally sustainable biological method to improve drought resistance in agriculture.

Ecofriendly Management of Wheat Panicle Blast Caused by Magnaporthe oryzae triticum

In this study, three wheat varieties were tested to determine seed germination and the incidence of Magnaporthe oryzae triticum (MoT). Among these varieties, BARI Gom 24 (Prodip) wheat seed exhibited the highest seed germination rate (93%) but also had the highest incidence (30%) of MoT. To manage blast disease in an ecofriendly manner, seven treatments were employed: T1 = Control, T2 = Garlic clove extracts, T3 = Aloe vera leaf extracts, T4 = Black cumin seed extracts, T5 = Neem leaf extracts, T6 = Nativo 75 WG, and T7 = Provax 200 WP. The experiment was conducted using a Randomized Complete Block Design (RCBD) layout with three replications using Prodip wheat variety that exhibited highest MoT infection severity based on laboratory analysis among collected varieties. Data were collected on blast disease incidence (%), disease severity, and various growth and yield parameters of wheat. The experiment’s results indicated that among all the treatments, T7 (Seed treatment with Provax 200 WP) and T5 (Foliar spraying with Neem leaf extract) performed better in controlling blast disease in wheat. The lowest blast disease incidence (%) was observed with T7 (Provax 200 WP), with values of 7.86, 9.86, and 10.19 recorded during the milking stage, soft dough stage, and hard dough stage of wheat, respectively. T5 (Neem leaf extract) also demonstrated a statistically equivalent reduction in blast disease incidence (%). In terms of disease severity, T7 (Seed treatment with Provax 200 WP) showed the lowest values of 1.03, 1.23, and 1.63 during the milking stage, soft dough stage, and hard dough stage of wheat, respectively. Foliar spraying with neem leaf extract also exhibited similar result as of Provax 200 WP regarding panicle blast severity. As a result of these findings, it can be concluded that T5 (Neem leaf extract) is recommended as an ecofriendly management approach for blast disease in wheat.

干旱胁迫下冬小麦(Triticum aestivum)高光谱特征和生理生态响应

2006年于冬小麦（Triticum aestivum）孕穗期、开花期和灌浆期，采用ASD Fieldspec HH光谱仪测定了不同水分胁迫下冬小麦高光谱反射率、红边参数和对应的冬小麦生理生态参数叶绿素a（Chla）、叶绿素b（Chlb）、叶绿素a＋b（Chla＋b），叶片水分含量（LWC），叶面积指数（LAI）。结果表明，冬小麦生理生态参数随生长发育呈现先上升后下降趋势，Chla、Chlb和Chla＋b开花期达最大值；LWC和M，孕穗期达最大值。随干旱胁迫程度增加，Chla、Chlb和Chla＋b、LWC和M，减少。不同水分处理下冬小麦高光谱反射率具有绿色植物特征。用红边一阶微分光谱特征参数分析，冬小麦孕穗期和开花期红边（λred）位于728-730nm，灌浆期红边（λred）移到734nm。Chla、Chlb和Chla＋b与Dλ730、Dλ702、Dλ730、Dλ718，LWC与Dλred、Dλ718以及LAI与Dλ718、Dλred、Sred均呈正相关，相关系数大于0．5（P〈0．05）。经回归分析，Chl与Dλ730 Dλ702、LWC与Dλred呈线性关系（R^2=0．87），LAI与Sred呈二次关系（R^2=0.68）。因此，用冬小麦高光谱特征及红边参数能判断冬小麦生育后期长势和农田水分胁迫程度。

条锈病对小麦(Triticum aestivum L.)叶片光合功能及光合功能蛋白D1表达的影响

测定了小麦(Triticum aestivum L.)感染小麦条锈病后的光合常数,以及叶绿素含量、类囊体膜光合电子传递速率和光合反应中心D1蛋白的变化。实验显示,条锈病侵染导致感病小麦叶片净光合速率与叶绿素含量降低;抗病小麦经侵染后净光合速率却有恢复过程,叶绿素含量先降后升。此外,感病小麦叶片被侵染后全链电子传递速率受到抑制,PSII电子传递速率的变化与全链电子传递速率的变化趋势相似,但PSI电子传递速率受到的影响较小;抗病小麦小麦叶片被侵染后电子传递速率所受影响较小。同时发现,病程中,感病和抗病小麦PSII的光合反应中心D1蛋白含量变化总是与PSII电子传递速率的变化类似,推测D1蛋白的表达量变化是引起PSII电子传递活性与全链电子传递速率变化的主要因素之一。

重金属Cd、Cu对小麦(Triticum aestivum)幼苗生理生化过程的影响及其毒性机理研究

对Cd、Cu单因子处理下小麦幼苗叶片和根系的SOD、POD酶活、可溶性蛋白含量以及叶片中叶绿素含量的变化进行了研究.结果表明,Cd、Cu胁迫下,小麦幼苗受到损伤的明显症状之一是叶片叶绿素含量下降;小麦植株叶片POD、SOD酶活能够被诱导而升高;重金属Cd、Cu对小麦幼苗根系的损伤较叶片大;重金属对小麦幼苗的毒害机理之一是抑制了蛋白质的生物合成;重金属引起的各个生化指标随着处理浓度和处理时间的变化远比有机污染物(如豆磺隆)简单.

“云南小麦”(Triticum aestivum ssp.yun-nanense King)的考察与研究

1979年和1980年我们对金善宝教授命名的“云南小麦”亚种进行了考察和研究。查明“云南小麦”分布在云南省澜沧江和怒江下游十二个县,约在北纬22°54′—25°03′和东经95°36°—100°85′左右。“云南小麦”生长在海拔1500米至2500米之间的高山区,而以1900米至2300米地带种植较多。原产地年均温15℃、年雨量1480mm 左右。小麦苗期和成熟期正置雨季,而孕穗至灌浆期处于旱季。晚熟,生育前期尤长。在原产地九、十月播种,二月拔节,三、四月抽穗,五、六月成熟。能避抗一月重霜,耐瘠,抗穗发芽,抗鸟兽害。穗长芒、短芒或无芒。颖有毛或无毛,有白、红、黑壳白底、白壳黑边、白壳黑斑等色。粒红色(过去曾发现白色的)。已定名十六个变种,其中此次新定名十个变种。经种间杂交和根尖细胞学观察,确定它具有 AABBDD 染色体组,并认为它在小麦属中的地位是一个原始栽培六倍体种。如按新分类法,即染色体组相同的都属一个种,则“云南小麦”是普通小麦的云南小麦亚种。

Triticum spelta 1BS染色体对K型小麦不育系花粉发育的影响

利用非1B/1R与1B/1R类型小麦雄性不育系及保持系,对2类K型不育系及其保持系花粉发育过程中丙二醛含量、花粉细胞膜透性、SOD活性、花粉发育形态等几个方面进行比较研究。结果表明,2类型小麦不育系花粉丙二醛含量和花粉提取液电导率从减裂期到散粉成熟期变化趋势基本一致,都呈上升趋势,而保持系在花粉发育全过程中2项指标都基本保持平稳。2类型不育系SOD活性从单核期到三核期都一直呈下降趋势。与保持系相比,2类不育系的SOD活性从单核期到二核期均显著高于其相应的保持系,三核期均低于其相应的保持系,且呈继续下降趋势。推断2类不育系的败育过程和败育时期基本一致,花粉败育的关键时期可能均为单核期到三核期。但花粉发育形态的染色观察表明,非1B/1R不育系从二核期出现花粉形态异常,而1B/1R不育系到三核期才出现,似乎又反映出非1B/1RK型不育系花粉败育稍早于1B/1RK型不育系。

水肥不同层次组合对冬小麦(Triticum aestivum L．)氮磷养分有效性和产量效应的影响

以肥熟土垫旱耕人为土为供试土样，用分层土柱试验法研究了不同层次水分、氮、磷组合对冬小麦（Triticum aestivum L．）氮磷养分有效性和产量效应的影响。结果表明，不同土层水肥处理的氮磷养分有效性和产量效应差异显著。氮素养分有效性在4．73％-41．19％之间，磷素养分有效性在4．11％-13．58％之间。对氮素养分有效性，单施氮整体湿润时（0-90cm土层湿润）较上干下湿（0-30cm土层干旱胁迫，30-90cm土层湿润）低4．87％，而氮磷配施在整体湿润时较上干下湿高6．38％，差异均达显著水平；对磷素养分有效性，氮磷配施时，在整体湿润时较上干下湿增加5．01T（P〈0．05）。从不同施肥土层看，氮素养分有效性均以0-90cm土层施肥处理最高；对氮磷配施处理，在上干下湿时分别比0-30cm、30-60cm和60-90cm土层施肥处理高9．5％、10．1％和20．2个％；对磷素养分有效性，整体湿润处理，以0-30cm土层施肥显著高于其它土层施肥处理。单施氮或磷，上干下湿时氮磷养分的产量效应均高于整体湿润处理，但氮磷配施时均以整体湿润处理较高；从不同土层施肥看，氮素养分的产量效应以0-90cm土层施肥最高；磷素养分的产量效应则表现为0-90cm与0-30cm土层施肥处理显著高于30-60cm和60-90cm土层施肥处理。分析0-90cm土层残留硝态氮和有效磷累积量可以看出，不同处理土壤残留硝态氮含量存在显著差异，上干下湿时CK、单施氮、单施磷和氮磷配施土壤残留硝态氮分别比整体湿润相应施肥处理增加125．8％、20．1％、21．9％和2．1％；不同处理有效磷差异性不及硝态氮明显。整体看，在两种水分状况下，均以0-90cm和0-30cm土层施肥有利于提高氮磷养分对冬小麦的有效性和产量效应，减少硝态氮和有效磷在土壤中的残留累积。考虑到生产上的可操作性，仍以施人0-30cm土层最适，说明即使在上千下湿情况下，保证上层有效养分供应仍具重要作用。

Identification of Triticum aestivum-Haynaldia villosa Translocation Line T6BS·6BL-2VS

[Objective] The aim of experiment was to provide a new germplasm for wheat breeding by further using desirable genes in 2V chromosome of Haynaldia villosa.[Method] Through hybridization between common wheat(Triticum aestivum)-Haynaldia villosa disomic substitution line and common wheat Nonglin26-3C chromosome of Aegilops triuncialis disomic addition line,the analysis methods such as chromosome C-banding,genomic in situ hybridization and molecular marker technique were comprehensively applied and combined characters investigation.[Result] The wheat-Haynaldia villosa translocation line(T6BS·6BL-2VS)was selected from hybrid progenies to conduct characters investigation,which found some bristles on glume ridge of T6BS·6BL-2VS.[Conclusion] The translocation line induced by gametocidal chromosome was a small segment translocation line and the gene of bristle on glume ridge of Haynaldia villosa was located between the middle and the terminal of 2VS.

Construction and Characterization of a Bacterial Artificial Chromosome Library for Triticum boeoticum

A bacterial artificial chromosome library has been constructed for Triticum boeoticum Boiss (A bA b) using the bacterial artificial chromosome (BAC) vector pECBAC1. The library consists of about 170 000 clones. A random sampling analysis of 200 BAC clones indicates that the average insert size is 104 kb. Based on the genome size of T. boeoticum, the library is about three times as large as T. boeoticum haploid genome (5 600 Mb). Screening the BAC library with cpDNA sequence psbA gene and mtDNA sequence atp6 gene as probe shows that contamination of the library with chloroplast and mitochondrial clones is less than 1%. The library will be a useful platform in gene clone and genomic research of wheat.

Agronomic Trait and Protein Component of F_2 Hybrid Originated from Intergeneric Somatic Hybridization Between Triticum aestivum and Agropyron elongatum

Protoplasts derived from common wheat (Triticum aestivum L,. cv. Jinan 177) were fused with UV-treated protoplasts of Agropyron elongatum. (Host) Nevski by PEG method, and fertile asymmetric somatic hybrid plants resembling wheat morphology were obtained. The F-2 hybrid plants could be divided into 3 types according to their morphology. Type I hybrids had high and loosely standing stalks with big spikes and grains. Type ii hybrids were dwarf and compact in shape with high tillering ability and smaller spikes. Type III hybrids were similar to type I as a whole but had more compact and erect spikes. All the F-2 hybrid lines were superior to wheat in seed protein content, although some difference existed between themselves. Protein analysis of immature embryos and flag leaves from hybrids by two-dimensional electrophoresis showed that they possessed characteristic proteins of both parents and some new proteins. There existed also some different kinds of proteins in different lines.

Hybrid Effects on the Release of Phytosiderophores in Winter Wheat (Triticum aestivum)

Fe (iron) deficiency is an important nutritional problem particularly in crop plants grown on calcareous soils. Phytosiderophore (PS) release has been suggested to be linked to the ability of graminaceous species and genotypes to overcome Fe_deficiency chlorosis. Thus, enhancing PS release is a critical step to improve Fe nutrition of plants grown on Fe stressed soils. The heterosis of PS release rate in common wheat was studied by analyzing PS release from roots of three hybrids and their four parents grown in Fe_deficiency nutrient solution under controlled environmental conditions. PS release rates were determined at two or three day intervals after onset of Fe_deficiency symptoms by the measurement of Fe mobilizing capacity of root exudates from freshly precipitated FeⅢ hydroxide. High amounts of phytosiderophores were released from the roots of all wheat genotypes under Fe_deficiency, and the amount progressively increased with the development of Fe_deficiency chlorosis. The results revealed that the hybrids had more sensitive feedback systems which secreted more phytosiderophores under Fe_deficiency than their parents. By analyzing the relationship between each hybrid and its parents, it was also found that the parents should be selected on the basis of the rate of PS release and the combining ability by using the heterosis to improve Fe utilizability of crop plants.

Occurrences of Yttrium in Soil and Its Potential Impacts on Paddy Rice Triticum aestivum

[Objective] The effects of yttrium nitrate （YNO3） on biomass and antioxi- dant systems of paddy rice （Yttrium （Y）; Oxidative stress; Dismutases （SOD）; Per- oxidases （POD）, Catalases （CAT）, Paddy rice （Triticum aestivum）） together with the occurrences of Y in soils were investigated to assess its ecotoxicological effects on plant. [Method]Y solutions with various concentrations were sprinkled on soil sam- ples, which were well mixed and then put into culture dishes to culture paddy rice seeds for further evaluation. [Result] The results indicated that 25-100 mg/kg Y treatments significantly increased the biomass （total weight, root weight, shoot weight and leaf weight）, chlorophyll （CHL） content and protein content of paddy rice, whereas 200-800 mg/kg Y treatments had a converse effect. Similarly, biomarker for the antioxidant systems including superoxide dismutases （SOD）, peroxidases （POD） and catalases （CAT） all exhibited similar trends in both shoots and roots of paddy rice. At the same time, the malonaldehyde （MDA） content increased at from 25 to 100 mg/kg and decreased with concentrations of Y from 100 to 800 mg/kg in both shoots and roots of paddy rice. This indicated that Y could stimulate the growth of plant at low concentration, but inhibit the growth at relatively high concen- tration. [Conclusion] The levels of Y were 641＋49, 328_＋16 and 473_＋40 mg/kg in soils collected from mining area, farmland and navel orange orchard respectively. The levels of Y in the investigated area were higher than the benefit level （100 mg/kg）, which could cause low biomass as well as low activity of SOD, POD and CAT in paddy rice. Therefore, a more careful use of Y is necessary in crop management.

Mutation Classification and Genetic Diversity Analysis of Triticum aestivum ssp. yunnanense King Based on Agronomic Traits

[Objective] The present study was conducted to provide basis for researches on breeding new wheat varieties and conserving rare species in Yunnan Province.[Method] 29 materials of Triticum aestivum ssp.yunnanense King（Yunnan Hulled Wheat）were taken for the research on classification and genetic diversity analysis based on 14 agronomic traits.[Result] Yunnan hulled wheat A14 could be an unnamed white seed variety,and other 28 materials were divided into 10 named mutation types;Yunnan hulled wheat was rich in variability of agronomic traits,in which the coefficient of variance（CV）of sterile spikelet number was the largest（22.59%）,while the CV of earing period was the lowest（3.71%）;the diversity indexes of seven qualitative characters ranged from 1.55-2.04.Moreover,the 29 Yunnan hulled wheat could be divided into 3 clusters by the UPGMA analysis.However,Yunnan hulled wheat varieties originating from similar mutation types did not completely cluster together.The genetic relationship was relatively close among A13（YT-35）,A14（YT-36）and A21（YT-37）,but the faster genetic relationship was observed between them and other Yunnan hulled wheat varieties.[Conclusion] Yunnan hulled wheat had an extensive genetic diversity in agronomic traits.

小冰麦(Triticum aestivum-Agropyron intermedium)对盐胁迫和碱胁迫的生理响应

将两种中性盐(NaCl和Na2SO4)和两种碱性盐(NaHCO3和Na2CO3)按摩尔质量比1∶1混合,在60～300mmolL-1盐浓度内模拟出5种强度的盐胁迫条件,在30～180mmolL-1盐浓度内模拟出6种强度的碱胁迫条件,并以此对小冰麦苗胁迫处理12d。测定相对生长率(RGR)、含水量、丙二醛(MDA)、电解质外渗率、叶绿素、类胡萝卜素6项胁变指标和Na+、K+、脯氨酸、甜菜碱、有机酸5种溶质含量。结果表明,碱胁迫下小冰麦的各项胁变反应均明显大于盐胁迫下。在本试验条件下,小冰麦可耐受的最高盐胁迫浓度为300mmolL-1,而碱胁迫仅为150mmolL-1。碱胁迫造成小冰麦光合色素含量急剧下降,可能是其危害甚于盐胁迫的原因之一。碱胁迫下有机酸大量积累可能是小冰麦响应碱胁迫的特殊生理机制。试验结果证明盐、碱胁迫是两种性质不同的胁迫,不仅对植物的作用机制不同,而且植物的适应机制也不同。

冬小麦(Triticum aestivum)分蘖冗余生态学意义以及减少冗余对水分利用效率的影响

通过盆栽试验,以旱作冬小麦(Triticum aestivum)为材料,分别在拔节和抽穗期对分蘖进行人工干扰,来模拟不可预测的自然干扰,对冬小麦分蘖冗余的生态学意义以及减少这些冗余对水分利用效率影响进行研究。设置3个处理:从拔节期开始剪去所有小的分蘖,仅保留主茎和一个大的分蘖(A);在拔节期剪去主茎和两个大的分蘖,保留所有小的分蘖(B);在孕穗期剪去主茎和有效分蘖,保留无效分蘖(C)。没有被干扰的植物作为对照(CK)。通过花期测定叶片的叶绿素含量、叶绿素荧光参数、气孔导度和蒸腾速率等生理指标来评价植物的生理与生化活性。结果显示,在拔节期和抽穗期去除主茎和大蘖后,无效分蘖的生理活性被激活,开始执行有效分蘖的功能。到花期时,这些无效分蘖已经在生理活性上满足了补充和替代有效茎的要求。虽然株高和穗的整齐度、穗数和产量显著下降,但并没有防碍小麦的繁衍子代,因此,正是这些由早期"无效分蘖"补充而来的有效茎,避免了小麦绝种的风险。而在拔节期去除无效分蘖后,对小麦产量没有显著影响,但提高了水分利用效率,和对照相比水分利用效率提高了10%。因此,可以认为小麦在分蘖上存在着对水分利用不利的生长冗余,减少这些冗余有望节约用水、提高作物的水分利用效率。

碱胁迫对小麦(Triticum aestivum Linn)叶片代谢过程的影响

【目的】阐明碱胁迫对小麦叶片离子平衡、初生及次生代谢产物的影响及其涉及的代谢途径,讨论其生长代谢变化规律及应答机制。【方法】以普通小麦(Triticum aestivum Linn)为材料,采用盆栽试验利用Na HCO_3﹕Na2CO_3=1﹕1混合模拟不同盐度碱胁迫条件,在苗期连续胁迫12 d后测定叶片生长、光合、离子和代谢产物。【结果】当碱胁迫强度超过小麦自身调节能力时,叶片中Na^+含量剧增,加上高p H危害,造成叶绿体遭到破坏、叶绿素含量降低、光系统Ⅱ活性受抑制、气孔导度及碳同化能力急剧下降,最终导致生长率降低。碱胁迫下Na^+大量增加的同时阴离子明显减少,造成叶片内负电荷亏缺和p H不稳定,导致离子平衡遭到破坏,进而引起一系列代谢途径的协变反应。通过GC-MS检测出73个代谢物,主要包括碳水化合物、氨基酸、有机酸等,其中,分别有25和48个代谢物在中度和重度碱胁迫下发生明显改变。主成分分析(PCA)结果显示全部样本均分布在95%的置信区间内,2个主成分得分达到89%。单因素方差分析表明,与对照组比较,在高浓度碱胁迫下发生的显著性变化明显高于低浓度碱胁迫。碱胁迫导致5种参与三羧酸(TCA)循环和6种参与糖酵解途径的代谢物含量明显降低,且引起大部分氨基酸(谷氨酸、丙氨酸、γ-氨基丁酸、天冬氨酸等)和糖类及多元醇(果糖、蔗糖、塔罗糖、肌醇等)大量降低。与此同时,碱胁迫诱导小麦有机酸大量积累,随胁迫强度的增加而上升,这种现象可能是小麦被动的适应调节过程,主要用于维持离子平衡并调节p H浓度。【结论】碱胁迫引起了TCA循环、糖酵解途径、卡尔文循环、莽草酸途径、细胞膜脂代谢、转氨基反应和γ-氨基丁酸(GABA)途径等代谢网络系统广泛变化,暗示了碱胁迫不仅对糖类、氨基酸类、脂肪和蛋白质合成代谢过程造成负面影响,而且限制C-N转变过程影响植物对N素的利用,造成营养匮乏抑制植物生长发育。

东方小麦(Triticum turanicum Jakubz.)醇溶蛋白遗传多样性分析

为了进一步利用东方小麦(TriticumturanicumJakubz.)遗传资源,对来自埃塞俄比亚、伊拉克、伊朗、阿塞拜疆、阿富汗、摩洛哥等国家共87份东方小麦醇溶蛋白位点的遗传多样性进行了分析。结果发现,供试材料存在丰富的遗传变异,87份材料共产生72种谱带类型,分离出33条带纹,每份材料可电泳11～2 2条带,平均16条;在α、β、γ和ω四个区均差异较大,分别有16、11、2 0和2 0种谱带变异类型。聚类分析发现,醇溶蛋白揭示的材料间遗传多样性与其地理来源有一定关系。

Wheat powdery mildew resistance gene Pm64 derived from wild emmer (Triticum turgidum var.dicoccoides) is tightly linked in repulsion with stripe rust resistance gene Yr5

Stripe rust and powdery mildew are both devastating diseases for durum and common wheat.Pyramiding of genes conferring resistance to one or more diseases in a single cultivar is an important breeding approach to provide broader spectra of resistances in wheat improvement. A new powdery mildew resistance gene originating from wild emmer(Triticum turgidum var.dicoccoides) backcrossed into common wheat(T. aestivum) line WE35 was identified. It conferred an intermediate level of resistance to Blumeria graminis f. sp. tritici isolate E09 at the seedling stage and a high level of resistance at the adult plant stage. Genetic analysis showed that the powdery mildew resistance in WE35 was controlled by a dominant gene designated Pm64. Bulked segregant analysis(BSA) and molecular mapping indicated that Pm64 was located in chromosome bin 2 BL4-0.50–0.89. Polymorphic markers were developed from the corresponding genomic regions of Chinese Spring wheat and wild emmer accession Zavitan to delimit Pm64 to a 0.55 cM genetic interval between markers WGGBH1364 and WGGBH612, corresponding to a 15 Mb genomic region on Chinese Spring and Zavitan 2 BL, respectively. The genetic linkage map of Pm64 is critical for fine mapping and cloning. Pm64 was completely linked in repulsion with stripe rust resistance gene Yr5. Analysis of a larger segregating population might identify a recombinant line with both genes as a valuable resource in breeding for resistance to powdery mildew and stripe rust.

Effects of Different Tillage Systems on Soil Properties,Root Growth,Grain Yield,and Water Use Efficiency of Winter Wheat (Triticum aestivum L.) in Arid Northwest China

Studies on root development, soil physical properties, grain yield, and water-use efficiency are important for identifying suitable soil management practices for sustainable crop production. A field experiment was conducted from 2006 through 2008 in arid northwestern China to determine the effects of four tillage systems on soil properties, root development, water-use efficiency, and grain yield of winter wheat （Triticum aestivum L.）. The cultivar Fan 13 was grown under four tillage systems：conventional tillage （CT） without wheat stubble, no-tillage without wheat stubble mulching （NT）, no-tillage with wheat stubble standing （NTSS）, and no-tillage with wheat stubble mulching （NTS）. The soil bulk density （BD） under CT system increased gradually from sowing to harvest, but that in NT, NTSS, and NTS systems had little change. Compared to the CT system, the NTSS and NTS systems improved total soil water storage （0-150 cm） by 6.1-9.6 and 10.5- 15.3% before sowing, and by 2.2-8.9 and 13.0-15.1% after harvest, respectively. The NTSS and NTS systems also increased mean dry root weight density （DRWD） as compared to CT system. The NTS system significantly improved water-use efficiency by 17.2-17.5% and crop yield by 15.6-16.8%, and the NTSS system improved that by 7.8-9.6 and 7.0-12.8%, respectively, compared with the CT system. Our results suggested that Chinese farmers should consider adopting conservation tillage practices in arid northwestern China because of benefits to soil bulk density, water storage, root system, and winter wheat yield.