Differential seedling resistance to the eyespot pathogens,Oculimacula yallundae and Oculimacula acuformis,conferred by Pch2 in wheat and among accessions of Triticum monococcum

Eyespot is an economically important stem‐base disease of wheat caused by two fungal species: Oculimacula yallundae and Oculimacula acuformis. This study investigated the efficacy of two sources of resistance, viz. the genes Pch1, introgressed into hexaploid wheat from Aegilops ventricosa, and Pch2, identified in wheat cv. Cappelle Desprez, against O. yallundae and O. acuformis separately. In a series of seedling bioassays Pch1 was found to be highly effective against both species. Although Pch2 was found to confer resistance against both pathogen species, it was significantly less effective against penetration from O. yallundae than O. acuformis. Furthermore, a quantitative trait locus (QTL) analysis was not able to locate any resistance to O. yallundae on chromosome 7A of Cappelle Desprez. This has important implications for the use of Pch2 in commercial cultivars as it is necessary to have genes that confer resistance to both pathogens for effective eyespot control. In addition, a set of 22 T. monococcum accessions was screened for resistance to both O. yallundae and O. acuformis to identify potentially novel resistances and to assess the accessions for evidence of differential resistance to the eyespot species. Significant differences in resistance to the two pathogens were identified in four of these lines, providing evidence for differential resistance in T. monococcum. This study demonstrates that future screening for novel sources of eyespot resistance should investigate both pathogen species.     

Spatial variability of fusarium head blight pathogens and associated mycotoxins in wheat crops

The spatial pattern of Fusarium‐infected kernels and their mycotoxin contamination was studied in four wheat fields in Germany using geo‐referenced sampling grids (12–15 × 20–30 m, 28–30 samples per field) at harvest. For each sample, frequency of Fusarium‐infected kernels and spectrum of species were assessed microbiologically; mycotoxin contents were determined by HPLC‐MS/MS analysis. Spatial variability of pathogens and mycotoxins was analysed using various parameters including Spatial Analysis by Distance IndicEs (sadie^® ). Microdochium majus, the most frequent head blight pathogen in 1998, was less frequent in 1999 and could not be detected in kernels from two fields in 2004. Fusarium avenaceum, F. graminearum and F. poae were the most frequent Fusarium species, with 7–8 species per field. The frequency of Fusarium‐infected kernels was 3–15% and the incidence of species showed considerable within‐field variability. Spatial patterns varied among Fusarium species as well as from field to field. Although pathogens and mycotoxin were often distributed randomly in the field, F. avenaceum, F. graminearum, F. poae, F. sporotrichioides, F. tricinctum and the mycotoxin moniliformin had an aggregated pattern in at least one field. Patterns are discussed in relation to spread of Fusarium species depending on inoculum sources, spore type, kind of dispersal, availability of susceptible host tissue and micro‐climate. Sampling of wheat fields for representative assessment of mycotoxins is complicated by random patterns of Fusarium‐infected kernels, especially where the frequency of infection is small.     

Relationship between brown foot rot and DNA of Microdochium nivale, determined by quantitative PCR, in stem bases of winter wheat

Relationships between the incidence and severity of brown foot rot and of pathogenic fungi, determined by diagnostic and quantitative PCR, were investigated during the growth of nine winter wheat crops in three cropping seasons. Microdochium nivale vars nivale and majus were the only brown foot rot pathogens present in significant amounts. Relationships between disease symptoms and amounts of pathogen DNA were often weak in early spring (when shoot-base symptoms are usually most difficult to ascribe to particular pathogens by visual examination) because of indistinct symptoms and small amounts of pathogen. Relationships were strongest during stem elongation. The amount of M. nivale in the tissues tended to decline in the summer as the plants matured, apparently disappearing partially from necrotic lesions to which it contributed, resulting in a weakened relationship between symptoms and pathogen DNA. Regression analyses of brown foot rot on amounts of M. nivale DNA for different wheat cultivars generally produced lines with similar slopes but were often most significant for the cultivar with most eyespot resistance (i.e. with least confounding eyespot) or most apparently genuine brown foot rot. DNA of Fusarium spp. was rarely present in amounts sufficient to quantify.     

The escalating threat of Rhizoctonia cerealis, the causal agent of sharp eyespot in wheat

Rhizoctonia cerealis, the causal agent of sharp eyespot on wheat, was not considered to be an important pathogen for many years. Recently, the disease has become endemic in many countries except for South America. The disease has created a new threat to world wheat production because the damage of wheat sharp eyespot has become increasingly severe. In this paper, previous studies on this pathogen, including the disease geographical distribution, pathogen identification, life cycle, symptoms, favourable environmental conditions, effects on wheat yield and control strategy, are reviewed. Such information will be helpful in management of sharp eyespot.     

Genetic structure and population diversity in the wheat sharp eyespot pathogen Rhizoctonia cerealis in the Willamette Valley,Oregon, USA

Wheat sharp eyespot, caused by the soilborne basidiomycete fungus Rhizoctonia cerealis group D subgroup I (AG-DI), is a common disease of wheat stems that has increased in global importance in recent years. The disease caused a severe and extensive epidemic throughout the Willamette Valley of Oregon in 2014 and has remained one of the most important wheat diseases in this region subsequently. The population structure of this pathogen is still not well understood. In this study, 572 pure cultures of R. cerealis AG-DI were isolated from five commercial fields and two experimental fields in the Willamette Valley, Oregon, in the spring of 2017 and 2018. Population structure studies were conducted using six microsatellite markers. Polymorphisms were observed at all six loci, and all seven subpopulations showed moderate gene and genotype diversity. Most of the loci were in Hardy–Weinberg equilibrium in the subpopulations, the entire population combined over locations and five of seven subpopulations were in gametic equilibrium, and the AMOVA and Mantel’s test demonstrated no differentiation among subpopulations. Though direct evidence is currently lacking, these results suggest that the sexual stage of the pathogen may be having a significant impact on pathogen population structure, and that the presence of basidiospores could be contributing to the extensive spread of this disease in the Willamette Valley in recent years.     

河南省小麦根、茎部内生真菌多样性及平板拮抗活性研究

To investigate the community composition and diversity of fungal endophytes in wheat roots and stems from different soil types in Henan Province, tissue isolation method was used to isolate and purify endophytic fungi from wheat plants collected from 22 counties/districts in five soil types, and the identification of the fungal endophytes fungi was based on morphology and internal transcribed spacer (ITS) sequence. The community composition and diversity of endophytic fungi were analyzed. The results showed that 426 endophytic fungi were affiliated with 23 genera, among which Chaetomium spp. had the highest number accounting for 23.2% of the total strain number, followed by Penicillium spp.. Five strains were tested for the antifungal activity against both Rhizoctonia Cerealis and Fusarium pseudograminearums on plate, and their inhibition rates against R. Cerealis ranged from 44.8% to 70.5% (zone widths 2.00~9.67 mm)while from 35.4% to 49.3% (zone widths 3.67~6.67 mm) against F. pseudograminearum. This paper clarifies the major taxa and their diversity of fungal endophytes in the roots and stems of wheat in different soil types in Henan Province, and their inhibitory effects on soil-borne fungi, providing a basis for the biological control of sharp eyespot and crown rot of wheat.     

5种种衣剂防治小麦主要土传病害研究

研究了5种种衣剂对小麦土传病害纹枯病、全蚀病和根腐病的防治效果。结果表明,230g/L吡虫啉·苯醚·咯悬浮种衣剂综合防治效果优于其他药剂处理,对小麦纹枯病的防治效果为73.51%～95.05%,对小麦全蚀病的防治效果为73.01%～87.41%,对小麦根腐病的防治效果为65.51%～92. 09%。按药效其次依次是60g/L戊唑醇悬浮种衣剂、30g/L苯醚甲环唑悬浮种衣剂、25g/L咯菌腈悬浮种衣剂、15%多·福悬浮种衣剂。随着小麦的生长,各处理的防效逐渐降低,但直到枯白穗期还有一定防治效果。同时230g/L吡虫啉·苯醚·咯悬浮种衣剂对小麦增产作用明显。     

土壤施硅对小麦和麦蚜的影响

为明确土壤施硅对小麦蚜虫的防控效果,本研究在小麦种植前分别配施0（CK）、40、80和120 kg/hm²四个浓度的硅肥,测量施硅后小麦生育期、生物量、叶面积、株高、产量指标以及荻草谷网蚜Sitobion miscanthi和禾谷缢管蚜Rhopalosiphum padi发生量。结果表明,施硅对小麦株高和穗数无显著影响,但80 kg/hm²和120 kg/hm²浓度施硅处理后小麦叶面积分别为1 786.03 mm²和2 033.54 mm²,生物量分别为133.68 g和134.50 g,小麦穗粒数分别为35.61粒和35.92粒,小麦千粒重分别为45.34 g和45.59 g,小麦产量分别为9 684.45 kg/hm²和9 835.05 kg/hm²,均显著高于对照,且小麦成熟期较对照提前3 d;80 kg/hm²和120 kg/hm²浓度施硅处理后禾谷缢管蚜发生量分别为90头和86头,均显著低于对照;40、80和120 kg/hm²浓度施硅处理后荻草谷网蚜发生量分别为128、117和105头,均显著低于对照。因此,田间土壤施硅80 kg/hm²和120 kg/hm²可以明显改善小麦农艺性状,提高小麦产量,并能减少麦蚜发生量。     

不同前茬作物对小麦田土壤养分及小麦光合性能的影响

在天山北坡棉花主产区,设置棉花-棉花-春小麦(C-C-W)、春小麦+复播饲料油菜-棉花-春小麦(W-C-W)两种轮作模式,以春小麦+复播饲料油菜连作为对照(CK),研究轮作倒茬后麦田土壤养分含量的变化规律,以及轮作倒茬后对小麦光合特性、产量的影响.结果表明:(1)W-C-W模式和CK土壤有机质含量分别提高1.61 g?...     

西北春小麦和麦田土壤中15种常用农药残留的检测

为掌握西北春小麦和麦田土壤的农药残留污染状况,在调研和总结分析了西北春小麦的病、虫、草害发生和防治措施基础上,采集了我国西北地区甘肃、青海、宁夏的9个春小麦产区的小麦籽粒和麦田土壤样品。针对春小麦病虫草害防治中常用的农药,使用HPLC-MS/MS和GC-MS方法,测定了吡虫啉、高效氯氰菊酯、辛硫磷、毒死蜱等4种杀虫剂,三唑酮及其代谢物三唑醇、戊唑醇、多菌灵、三环唑、苯醚甲环唑等6种杀菌剂,精噁唑禾草灵、苯磺隆、2,4-滴丁酯、炔草酯及其代谢物炔草酸等5种除草剂,共15种农药及代谢物在小麦籽粒和麦田土壤中的残留量。通过与小麦中农药残留限量相比较,评价了西北春小麦的食品安全。结果显示,仅在采自甘肃金昌的小麦籽粒样品中检出了戊唑醇,且未超过最大残留限量,在其他样品中均未检出15种农药的残留,表明西北春小麦和麦田土壤的农药安全性均较高。本研究为掌握小麦籽粒的农药残留和麦田土壤的农药污染情况提供了研究数据,为进一步指导西北春小麦的绿色无公害病虫害防治提供了参考。     

生物炭施用对冬麦田土壤水热环境及土壤呼吸的影响

探究施用生物炭对冬麦田土壤水热因子及土壤呼吸的影响,对生物炭在麦田应用及农田固碳减排有重要的实践意义。2018年10月至2021年6月在关中灌区连续3 a进行了麦田生物炭施用试验,试验设置生物炭施用量水平分别为：0 t·hm^-2·a^-1（C0）、10 t·hm^-2·a^-1（C10）、20 t·hm^-2·a^-1（C20）,通过测定小麦生长季的土壤温度、土壤水分、土壤呼吸速率及产量,明确不同施炭量对冬小麦田土壤水热因子及土壤呼吸的影响。各处理生育期内土壤呼吸速率及全生育期CO₂排放量存在显著性差异（P<0.05）,均表现为C0>C20>C10。生物炭施入增加了生育期内的平均土壤温度,同时显著提高了0～20 cm土壤含水量（P<0.05）,并减弱了土壤水分在生育期内的变化幅度。C10、C20处理3 a平均土壤含水量较C0分别增加了17.0%、29.0%。5 cm及10 cm土壤温度能分别解释土壤呼吸变化的54.7%～...     

华北平原不同灌水条件下两冬麦品种土壤水分动态与产量差异

采用LSD法对华北平原不同灌水条件下(设4个水分处理:0水、1水、2水和3水)两品种(科麦一号和石家庄8号)冬小麦田土壤水分动态变化进行了观测,并对产量、产量构成要素及其生态指标进行了定量分析,以探讨品种间的差异.研究发现:所有灌水处理0～140 cm土层土壤水分变化较大,而0水处理的0～40 cm和80～140 cm土层含水量变化比较活跃,其幅度低于灌水处理.品种间相同水分处理的土壤含水量变化趋势一致,除1水处理科麦一号变幅较大外,其他3个处理均以石家庄8号变幅较大.科麦一号与石家庄8号均以3水处理的产量最高,比0水处理分别增产44.44%、42.88%,但由于该处理灌水充足,小麦相对晚熟耗水量大,致使收获前土壤含水率急剧下降.在各水分处理中,产量构成要素穗数皆以3水最高;穗粒重皆以1水最高(两个品种穗粒重1水与2水差异不显著);千粒重皆以0水最高.穗粒数以1水最高.收获指数皆以0水最高.科麦一号对水分较为敏感,但耗水量明显小于石家庄8号.要达到经济高产的目标,科麦一号灌2水较为合适,石家庄8号需灌3水.     

微咸水灌溉对河北低平原土壤盐分动态和小麦、玉米产量的影响

在河北低平原有咸水区的2个试验站,通过田间小区试验,连续3年研究了2g·L-1咸淡混合水灌溉对土壤盐分动态和小麦、玉米产量的影响.结果表明,2g·L-1咸淡混合水灌溉显著提高了主根层和0～120 cm土体的含盐量.麦收后微咸水灌溉处理的根层土体ECe值3年平均比淡水灌溉分别增加0.092和0.091 dS·m-1,0～120 cm土体ECe3年平均比淡水灌溉分别增加0.051 dS·m-1和0.147 dS· m-1;玉米收获后微咸水灌溉处理的根层土体ECe3年平均比淡水灌溉分别增加0.059 dS·m-1和0.127 dS·m-1,0 ～ 120 cm土体ECe3年平均比淡水灌溉分别增加0.082 dS· m-1和0.131 dS·m-1.总体上2g·L-1咸淡混合水灌溉对小麦、玉米的产量没有影响.因此从微成水长期安全利用的角度,对土壤盐分动态进行长期监测,定期淡水淋盐是非常必要的.     

Evidence that wheat cultivars differ in their ability to build up inoculum of the take‐all fungus,Gaeumannomyces graminis var. tritici,under a first wheat crop

The effect of wheat cultivar on the build‐up of take‐all inoculum during a first wheat crop was measured after harvest using a soil core bioassay in field experiments over five growing seasons (2003–2008). Cultivar differences in individual years were explored by analysis of variance and a cross‐season Residual Maximum Likelihood (REML) variance components analysis was used to compare differences in those cultivars present in all years. Differences between cultivars in the build‐up of inoculum were close to or at significance in two of the five trial years (2004 P < 0·05; 2006 P < 0·07), and current commercially listed cultivars were represented at both extremes of the range. In 2007 and 2008, when environmental conditions were most favourable for inoculum build‐up, differences were not significant (P < 0·3). In 2005 the presence of Phialophora spp. at the trial site restricted the build‐up of take‐all inoculum under all cultivars. The cross season REML variance components analysis detected significant differences (range: 3·4–47·8% roots infected in the soil core bioassay; P < 0·01) between the nine cultivars present in all years (excluding 2005). This is the first evidence of relatively consistent differences between hexaploid wheat cultivars in their interactions with the take‐all fungus, and this could give an indication of those cultivars that could be grown as a first wheat crop, in order to reduce the risk of damaging take‐all in a second wheat crop. This phenomenon has been named the take‐all inoculum build‐up (TAB) trait.     

聚丙烯酰胺施用方式对土壤水热及春小麦生产的影响

为了寻找聚丙烯酰胺在春小麦生产中的最佳施用方式,2010年在河套灌区,采用田间试验,以不施用聚丙烯酰胺为对照,开展了沟施、混施、撒施聚丙烯酰胺对土壤水分、土壤温度和春小麦生长状况的影响研究.结果表明:不同施用方式均提高了土壤水分含量,特别是在缺乏灌溉的开花期具有显著作用,其中撒施效果较强,沟施、混施较弱;不同施用方式降低了土壤最高温度,提高了最低温度,缩小了日温差,降低了日均温,其中撒施对地表温度影响较大,沟施对10 cm土层土壤温度影响较大;沟施、混施、撒施均提高了春小麦的总生物量及根系生物量,促进了根系向深层土壤分布,分别较对照增产9.11％、3.94％和28.82％;不同施用方式提高了水分利用效率、水分产出率和灌溉水分产出率,其中撒施效果较强,沟施较弱.在河套灌区,春小麦播种时施用聚丙烯酰胺,撒施应是最适宜的方式.     

Assessment of the pest status of Pratylenchus curvicauda and ultrastructural changes in roots of infected wheat and barley

Pratylenchus curvicauda, which was first described in metropolitan Perth in 1991, was recently identified in grain-growing areas in Western Australia. The biology of this root-lesion nematode, and especially its pest status, is unknown. We investigated its life cycle and interaction with host plants, because such information is essential for its management. The life cycle took 45 days to complete in a wheat cultivar maintained at 23°C. Over 10 weeks, the nematode multiplied in 26 of 61 genotypes; these host plants were all cereals and included widely grown cultivars of wheat and barley. Eighteen other cereal genotypes and 13 cultivars including canola, chickpea, ryegrass, lupin, soybean, and tomato, sustained the nematodes to different degrees without multiplication. Four cover crops were not suitable hosts. The patterns of attraction of the nematodes and penetration into roots of the host and tolerant plants were similar. The nonhosts attracted fewer nematodes, none of which penetrated the roots. Browning of infected roots was atypical—it occurred late in some roots, 55 days after inoculation, and in the presence of a fungus. The nematodes were confined to, and fed from, cortical cells. The ultrastructure of infected wheat and barley cells showed typical signs of damage caused by Pratylenchus spp. and included cell disorganization and lack of membrane integrity, disintegration of cytoplasm, hypertrophy of some nuclei, and deposition of tannin-like granules. This detailed characterization of P. curvicauda–host interaction indicates the nematode is likely to be a pest of major crops, and attention should be given to its management.     

不同覆草量苹果园土壤水温效应及对树体生长的影响

将麦草覆盖应用于果园,研究不同覆盖用量22 000 kg·hm-2(T1)、33 000 kg·hm-2(T2)、44 000 kg·hm-2(T3)和清耕(CK)在整个生长期对19年生长富2号苹果园0~100 cm土壤水分、5~25 cm土壤温度、树体生长量及果实品质的影响。结果表明:在旱情较重的4—7月,3种覆草处理的平均含水量随覆草量的增加而增大,其中T2和T3处理极显著(P0.01)高于CK,高出8.98%~27.09%;且3种覆草处理0~20、20~40 cm土层的含水量极显著(P0.01)高于CK,高出9.36%~73.77%;4—8月3种覆草处理的各深度地温低于CK,4—6月份极显著(P0.01)低于CK,低出2.11℃~8.02℃;相反,9—11月份高于CK。覆草处理5~20 cm深度土温日变幅极显著(P0.01)低于CK,低出0.39℃~3.63℃。果实单果重和产量以T2处理最高,3种覆草处理每公顷产量较CK极显著(P0.01)提高,高出10.70%~20.83%;产量水分利用效率覆草处理较CK极显著(P0.01)增高,高出9.87%~20.87%。覆草对树体生长量、枝类比例影响不大。综合各种效应及投入产出比,陇东黄土高原苹果园覆草量以22 000~33 000 kg·hm-2较经济适宜。     

施钾和秸秆还田对栗钙土区土壤养分及小麦产量的长期效应研究

1993～2006青海省栗钙土区施钾与小麦秸秆还田对耕层(0～20 cm)土壤钾素与其它养分指标以及小麦产量的长期影响定位试验结果表明:长期施钾或秸秆还田处理土壤速效钾、缓效钾和全钾含量均高于长期不施钾处理(NP),其中钾肥配合秸秆还田处理(NPK+St)三种类型钾含量均与NP处理差异显著;施钾或秸秆还田可提高速效钾和缓效钾在全钾中的比例,同时降低矿物钾的比例;与原始土壤相比,钾肥投入处理(NPK与NPK+St)的速效钾及NPK+St处理的缓效钾含量均高于原始土,其它处理三种类型钾含量均不同程度低于原始土壤;不同处理土壤钾素年均消耗K2O在175.5 kg/hm2以上,四个处理中只有NPK+St处理土壤钾素表观有盈余,其钾素平衡系数为1.55;相比只施氮磷肥,长期施钾或秸秆还田可降低土壤铵态氮、有效硫、钙、镁以及全磷的含量而提高有机质、有效磷、铜、铁、锰、锌以及全氮的含量,影响程度不一;定位14年间小麦产量基本不受施钾与秸秆还田措施的影响,处理之间差异不显著.     

冬小麦田大穗看麦娘种群动态及对小麦产量的影响

为明确麦田杂草大穗看麦娘Alopecurus myosuroides的田间种群发生动态规律,采用固定样方和随机样方取样方法于2013—2015年在山东省济南市研究了冬小麦田大穗看麦娘田间种群的萌发和生长动态,并分析了不同密度大穗看麦娘对小麦产量及其构成因素的影响。结果表明:在济南市小麦播后20~40 d为大穗看麦娘出苗高峰期,至11月下旬出苗量占全年出苗总量的97.1%。11月上旬,大穗看麦娘开始出现分蘖,至翌年4月上中旬结束,分蘖数平均每株为6.3个,比小麦多3.1个。3月下旬大穗看麦娘开始拔节,4月中旬平均株高超过小麦,5月下旬平均株高达到75.6 cm,高出小麦2.5 cm。5月上旬大穗看麦娘单茎平均鲜重达到最大为1.7 g,小麦为12.6 g。大穗看麦娘出苗、株高、分蘖和鲜重的变化与小麦变化趋势一致,与时间、温度密切相关。随着大穗看麦娘密度的增加,小麦产量急剧下降,当密度达到420株/m~2时,小麦产量损失率高达65.8%。大穗看麦娘对小麦产量构成因素中的穗密度影响最大,其次是穗粒数,对千粒重影响不显著,当密度为420株/m~2时,小麦穗密度减少55.2%,穗粒数减少26.4%。     

Detection and recovery of Rhizoctonia solani in naturally infested glasshouse soils using a combined baiting, double monoclonal antibody ELISA

A combined baiting, double monoclonal antibody immunoassay was developed that allows specific and sensitive detection of the economically important soil-borne plant pathogen Rhizoctonia solani in naturally infested soils. The assay is quick, taking only three days to complete from receipt of soil samples and the immunoassay format allows recovery of Rhizoctonia isolates from colonized baits for determination of anastomosis group (AG) affiliation and pathogenicity. The assay was tested on naturally infested soils from commercial glasshouses used to grow lettuce. Using the immunoassay, conventional anastomosis tests against known AG isolates, and pathogenicity tests, it was shown that R. solani isolates recovered from soil samples were pathogenic towards lettuce and belonged to AG4. Furthermore, those isolates that exhibited strong pathogenicity towards lettuce were recovered from sites that had experienced severe Rhizoctonia damage in previous lettuce crops. The possibility of developing a preplanting test to predict damage to specific crop plants due to the presence of particular AGs in the soil is discussed.