Interaction of Fusarium solani f. sp. glycines and Heterodera glycines in Sudden Death Syndrome of Soybean

ABSTRACT Sudden death syndrome (SDS) of soybean is caused by the soilborne Fusarium solani f. sp. glycines (synonym F. virguliforme). In a sequential approach, two multifactor factorial-design microplot experiments were conducted to investigate the effects of fungal infestation levels and soil moisture on both root necrosis and foliar SDS severity, and the interaction between F. solani f. sp. glycines and Heterodera glycines in fumigated versus nonfumigated soil. In 2003, soybean cv. Spencer was grown in nonfumigated or methyl bromide-fumigated soil and infested with increasing levels of F. solani f. sp. glycines, either under rainfall or irrigated after growth stage V6/R1. In 2004, interactions between F. solani f. sp. glycines and H. glycines were explored in a factorial inoculation design in fumigated or nonfumigated soil, planted to Williams 82 or Cyst-X20-18. In both years, higher levels of foliar SDS severity and root necrosis were found in F. solani f. sp. glycines-infested soils with H. glycines than in soils without the nematode on the soybean cultivars susceptible to both pathogens. Both natural infestations of H. glycines in 2003 and artificially amended populations of H. glycines in 2004 contributed to higher foliar SDS severity. More severe foliar SDS symptoms always were associated with more root necrosis, but elevated levels of root necrosis did not predict severe leaf symptoms. In contrast to the critical role of H. glycines, increasing fungal infestation levels had no significant effects on increasing either foliar SDS symptoms or root necrosis. Effects of moisture regime and fungal infestation levels also were examined in factorial greenhouse and growth chamber experiments. High soil moisture resulted in higher levels of SDS root necrosis. In the greenhouse, root necrosis increased at a higher rate in low soil moisture than the rate in high soil moisture. The two pathogens acted as a complex and the disease development was strongly dependent on high soil moisture.     

Integrated control of Rhizoctonia solani by methyl bromide and Trichoderma harzianum

Under laboratory conditions, isolate TH–203 of Trichoderma harzianum was found to be tolerant of up to 20 000 ppm methyl bromide (MB) (v/v), whereas the plant pathogen Rhizoctonia solani was susceptible to a dose of less than 9000 ppm (v/v). Exposure to sub–lethal concentrations of MB had no effect on the in vitro antagonistic ability of T. harzianum . Soil fumigation with MB at the equivalent of a commercial dose of 500 kg/ha did not reduce the population of Trichoderma in soil and allowed rapid colonization of Trichoderma to develop in the soil.
Under greenhouse conditions a combination of T. harzianum and a reduced dose of MB (equivalent to 200 kg/ha) completely controlled disease incidence of R. solani in bean seedlings compared with controls in untreated soils. Similar disease control was achieved with the recommended dose of MB. Under field conditions, the combination of 200 kg/ha MB and T. harzianum gave a significant synergistic effect on damping–off of carrot seedlings caused by R. solani , and had a similar effect on growth, yield and disease control to that of the recommended dose.
T. harzianum was also able to prevent reinfestation by R. solani in fumigated soils.     

Transfer of Biological Soil Suppressiveness Against Heterodera schachtii

ABSTRACT Heterodera schachtii-suppressive soil at a rate of either 1 or 10% (dry wt/wt) transferred suppressiveness against the beet cyst nematode to fumigated field plots when mixed into the upper 10-cm soil layer. Soil suppressiveness was established after 1 month of moist fallow and 77 days of Swiss chard cropping in the 10% transfer treatment and after 230 days in the 1% transfer treatment. The number of infective second-stage juveniles (J2) of H. schachtii, monitored initially at 150 degree-day intervals and later at 300 degree-day intervals, indicated the status of suppressiveness in the different treatments during the cropping period. In a greenhouse experiment, amending fumigated field soil with 0.1, 1.0, or 10% suppressive soil, suppressed multiplication of H. schachtii when soils were infested with an additional 5,000 J2. In a second greenhouse experiment, a fumigated sandy loam amended with 10 or 25% suppressive soil and a fumigated loam amended with 25% suppressive soil had significantly fewer eggs per cyst than the nonamended fumigated treatments when 1,000 J2 were added.     

不同大豆品种与SCN 3号生理小种互作效应研究

 在田间研究了不同大豆品种对大豆胞囊线虫(soybean cyst nematode,SCN)的发育及繁殖的影响不同。结果表明,辽K89102为抗侵入型品种,Peking、PI90763、应县小黑豆、磨石豆和Franklin等的根内线虫从J2向J3或J3向J4发育过程中受到抑制,这些品种均有不同程度的抗线虫发育特性;不同品种对其根内SCN的雌雄分化有较大影响,感病品种根内SCN雌雄比远大于抗病品种,辽豆10根内线虫雌雄比例最高,为11.5:1.0,Peking根内线虫雌雄比例最低,为0.1:1.0;不同品种根围SCN最终群体量有较大差异,辽豆10根围土壤中胞囊量增加了331.5%,Peking和磨石豆的增幅最小,为16.7%。SCN侵染后,不同品种产生的组织病理学反应不同,抗病品种产生明显的组织病理学反应,表现在品种Peking和PI437654的根内线虫虫体附近根组织细胞有坏死现象,而感病品种辽豆10和开育10则没有坏死现象。     

Influence of methyl bromide soil fumigation method on fungicidal efficacy and bromide residues

Highest inorganic bromine residues (30 ppm) were found when soil was fumigated with liquid methyl bromide (MB) introduced by conventional means into evaporating dishes. With preheated (vaporized) MB or injection of MB/chloropicrin (CP) mixtures, bromide concentrations were reduced by 50%. They were uniform throughout the soil (0 to 60 cm) except after MB/CP injection, when larger residues were found in the 30-60 cm layer. Leaching with 2000 m^p3/ha (20 cm) of water always reduced bromide content to 7.5 and 10 ppm at the 0-30 and 30-60 cm depth, respectively. Organic amendments to soils substantially increased bromide levels up to 118 ppm, most of which was found in the upper soil layers; two teachings with 2000 m^p3 /ha water were required to return the soils to their normal state.Sclerotium rolfsii andFusarium oxysporum f. sp.dianthi cultures buried in soil were eliminated from the upper 30 cm with MB applied either conventionally or preheated. At 50 cm, 500 kg/ha of the preheated gas was superior to 1000 kg/ha of the cold gas. All MB fumigations suppressed carnation flower yields compared with CP alone but were superior to no treatment. After leaching, MB-fumigated soils yielded the highest number of flowers.     

Biological Control Efficiency of Fusarium Wilt of Tomato by Nonpathogenic Fusarium oxysporum Fo-B2 in Different Environments

ABSTRACT Efficiency of nonpathogenic Fusarium oxysporum Fo-B2 for the biological control of Fusarium wilt of tomato, caused by F. oxysporum f. sp. lycopersici CU1, was examined in different environments: a growth chamber with sterile soil-less medium, a greenhouse with fumigated or nonfumigated soil, and nonfumigated field plots. Inoculation of Fo-B2 onto tomato roots significantly reduced the severity of disease, but the efficiency of disease suppression decreased as the experimental environment became less controlled. Relationships between the recovery of Fo-B2 from hypocotyls and the disease severity indicated that the biocontrol agent was most effective when it colonized vascular tissues intensively. Moreover, the degree of Fo-B2 colonization was greatly reduced when the seedlings were grown in nonfumigated soil. Dose-response models (negative exponential, hyperbolic saturation, and logistic) were fit to observed data collected over a range of inoculum densities of the pathogen and the antagonist; the logistic model provided the best fit in all environments. The ratios of an 50% effective dose parameter for Fo-B2 to that of CU1 increased as the environment became less controlled, suggesting that environmentally related efficiency reduction impacted the antagonist more than the pathogen. The results suggest that indigenous soil microbes were a primary factor negatively influencing the efficiency of Fo-B2. Therefore, early establishment of the antagonist in a noncompetitive environment prior to outplanting could improve the efficacy of biological control.     

Methyl bromide and PCNB for sclerotium crown rot control in iris

Methyl bromide (MB) at rates of 500, 1000 and 1500 kg/ha, Terraclor 75 WP (PCNB) at 150 and 300 kg/ha, and combinations of the two, were studied for control ofSclerotium rolfsii prior to iris cultivation. Sclerotia buried 10 cm deep in soil were all killed by MB at 500 kg/ha; at greater depths higher doses were required. Bulbs harvested from PCNB- and PCNB + MB-treated plots were healthy; 75% of the bulbs in control plots were infected at harvest. When MB was used alone, the soil became re-infested (2–6% diseased plants). Bromide toxicity, correlated with the MB dose applied, appeared 41/2 months after planting; leaves yellowed and senesced prematurely. MB treatments also reduced bulb size, and residual phytotoxicity was found when the bulbs from treated plots were planted in the following year.     

淡紫拟青霉发酵滤液对大豆胞囊线虫趋化性的影响

 实验室条件下,研究了大豆胞囊线虫幼虫对大豆根和根浸出液的趋化性以及淡紫拟青霉代谢产物对其趋化性的影响。结果表明,大豆胞囊线虫二龄幼虫(J₂)对大豆根存在着一定的趋化性,而淡紫拟青霉发酵滤液对J₂存在明显的驱避性。在根浸出液、真菌滤液及其混合液剂处理下,大豆胞囊线虫J₂在WA平板上靠近处理液的0~1cm区间中分布率存在极显著差异(P <0.0 1),而加样时间(液剂与线虫同时放置或提前2 4h处理)对其分布率没有显著影响。大豆幼根蘸取滤液后对线虫J₂在该区间的分布与不经处理的幼根差异显著(P <0.0 5),证明淡紫拟青霉发酵滤液可以明显地降低线虫与大豆根的亲和力,并强烈抑制线虫对大豆根的侵染。     

肥料减施下玉米-大豆间作对作物产量和昆虫群落组成及多样性的影响

为探究肥料减施下玉米-大豆间作对作物产量和昆虫群落组成及多样性的影响,在玉米、大豆单作及二者间作下施以标准肥料750 kg/hm~2和减半肥料375 kg/hm~2,于作物生长期调查田间昆虫群落组成及多样性,并在收获期对玉米和大豆进行测产。结果表明:与单作玉米相比,间作玉米在施用标准肥料下的百株生物量、百株籽粒重和千粒重分别显著增加78.33%、85.35%和38.71%,而在施用减半肥料下则分别显著增加90.91%、135.73%和33.33%;相同种植模式下,与施用标准肥料相比,减半肥料使单作玉米百株籽粒重显著降低22.45%。与单作大豆相比,在施用标准肥料下,间作大豆的百株籽粒重和千粒重分别显著降低49.47%和11.54%,在施用减半肥料下,间作大豆的百株生物量、百株籽粒重和千粒重分别显著降低73.94%、50.51%和17.39%;相同种植模式下,与施用标准肥料相比,减半肥料使大豆在单作和间作下的百株籽粒重分别显著降低65.02%和65.73%,使间作下大豆的百株生物量和千粒重分别显著降低73.14%和17.39%。与单作相比,间作均显著降低了标准肥料和减半肥料处理下玉米和大豆害虫群落的物种数、多样性指数和均匀度指数,还显著降低了标准肥料和减半肥料处理下玉米天敌昆虫群落的物种数和优势度指数以及大豆天敌昆虫群落的物种数和均匀度指数。表明玉米-大豆间作能有效提高玉米产量,降低虫害发生,但对大豆生产不利,而间作条件下减施肥料对玉米产量的影响更小。建议在田间生产中可将夏玉米和大豆间作种植,更有利于通过生态学方法控制田间害虫发生和增加作物总体产量。     

大豆种质资源对大豆孢囊线虫3号和4号生理小种的抗性鉴定

选育和利用抗病品种是控制大豆孢囊线虫病的最经济有效方法.本研究通过测定国内外大豆种质资源对大豆孢囊线虫2个生理小种的抗性水平,以期获得抗大豆孢囊线虫的品种与种质资源.2009年9月-2010年6月,采用PVC柱法在温室内鉴定了300份大豆种质资源分别对大豆孢囊线虫(SCN)3号和4号生理小种的抗性.用3号生理小种测定得到了抗性表现免疫的种质资源12份,表现高抗的28份,表现中抗的39份,分别占测试材料的4.0％、9.3％和13.0％;用4号生理小种测定得到了免疫的种质材料8份,高抗的18份和中抗的51份,分别占测试材料的2.7％、6.0％和17.0％.对2个生理小种的毒力差异比较表明,20份大豆种质资源的抗性表现差异明显,4号生理小种的毒力比3号生理小种强.本研究所鉴定出的抗病品种与资源,不仅对农业生产中利用抗病品种合理布局具有指导意义,而且为大豆抗孢囊线虫病的品种培育提供了重要的抗源材料.     

The critical period of weed control in double-cropped soybean

Double-cropped soybean after winter cereals is the most common soybean production system in the eastern Mediterranean region of Turkey. Weeds are among the main obstacles to double-cropped soybean. A study was conducted in 2002 and 2003 to determine the critical period of weed control (CPWC) for double-cropped soybean. The treatments consisted of either allowing weeds to infest the crop for increasing durations after sowing, or maintaining plots weed-free for increasing durations after sowing. The Gompertz and logistic equations were fitted to relative yields representing the critical weed-free period and the critical time of weed removal, respectively. Johnsongrass (Sorghum halepense), common cocklebur (Xanthium strumarium) and field bindweed (Convolvulus arvensis) were the dominant weeds. For 5% crop loss level, the CPWC was almost all season long, whereas it was from V1 to R6-R7 growth stages for 10% yield loss level. These findings indicate that pre-sowing or pre-emergence control methods should be applied in the region to avoid greater crop losses.     

大豆种质资源对大豆孢囊线虫的抗性评价

 大豆孢囊线虫(Heterodera glycines Ichinohe,SCN)是大豆(Glycine max (L.) Merrill)生产中的毁灭性害虫,种植抗性品种是控制其危害、减少产量损失的最佳途径。本研究通过温室盆栽实验评价了300份大豆种质对大豆孢囊线虫3号和4号生理小种的抗性。分别筛选到高抗和中抗3号生理小种的大豆种质27份和21份;高抗和中抗4号生理小种的大豆种质11份和9份。在所有供试材料中有10份材料同时对大豆孢囊线虫3号和4号生理小种表现高抗。线虫侵染实验表明,抗性材料对大豆孢囊线虫的发育有阻碍作用,并能显著降低最终形成的孢囊数。     

连作和轮作对大豆胞囊线虫群体数量及土壤线虫群落结构的影响

大豆胞囊线虫Heterodera glycinesIchinohe病害是大豆生产中的毁灭性病害,对世界大豆生产造成重大损失。采用根染色法和常规土壤线虫分类鉴定技术研究了连作和轮作两种耕作方式下大豆胞囊线虫群体数量和土壤线虫群落结构的变化。结果表明,连作使大豆田土壤中胞囊和根系上各龄期胞囊线虫数量显著增加(95.6→335.5),而轮作积累很少(10.3→31.8),感病品种中J2的侵入数量决定了大豆胞囊线虫形成胞囊的数量(22.8→95.6,129.4→335.5)。玉米-玉米-大豆的轮作方式使胞囊积累最少(10.3)。轮作大豆田土壤线虫总数高于连作,主要由于轮作大豆田土壤线虫的优势属Helicotylenchus和优势营养类群植物寄生线虫PP的相对丰度高于连作,但大豆胞囊线虫的相对丰度正相反,连作(33.65%)高于轮作(0.91%),说明Heterodera glycines可以作为土壤线虫的关键属种用以指示土壤发病的严重程度。研究中重要的优势属和关键属种cp值均为3,说明其繁殖和抗干扰能力比较强。研究证明土壤线虫优势营养类群、优势属种和关键属种可以有效地指示农业土壤健康状况和大豆田的大豆胞囊线虫病害的发生程度。     

大豆玉米间作和同穴混播对大豆病虫发生的综合效应研究

１９９３～１９９５年进行了大豆玉米间作和同穴混播对大豆病虫发生的综合效应研究。结果表明,间作和同穴混播豆田的病虫发生危害轻于纯作豆田,与纯作比较,间作田和同穴混播田主要害虫降低率分别在１１．４％～８１．４％和２０．９％～７６．０％之间;其病害降低率分别为７０．０％～１００％和５６．７％～１００％。间作只有豆天蛾和蛴螬可达防治指标,同穴混播田仅豆天蛾达防治指标。由于间作和同穴混播田提高了生物多样性,增强了自然生态控害功能。捕食性天敌,瓢虫分别较纯作增加８４．０％和８６．５％,草蛉增加５８．９％和８０．６％,蜘蛛增加４１．３％和５２．３％;寄生性天敌显著增加,蚜茧蜂对蚜虫寄生率增加２３．９％和２９．９％,赤眼蜂对豆天蛾卵寄生率增加１３．０％和２０．０％,银纹夜蛾幼虫被寄生率增加１８．７％和２５．３％。这２种种植方式产生的经济效益较纯作田增加３２．９％和３３．７％。     

Coinfection of soybean plants with Phytophthora sojae and soybean cyst nematode does not alter the efficacy of resistance genes

The soybean cyst nematode (SCN) Heterodera glycines and the oomycete Phytophthora sojae are among the most damaging pathogens of soybean worldwide. Resistant cultivars are commonly used to manage these diseases. As it is known that the presence of SCN can facilitate the development of other pathogens, it is important to verify if there is a synergistic activity between SCN and P. sojae. The purpose of this study was to evaluate a possible interaction on susceptible and resistant soybean lines. The plants were inoculated with one or both organisms at different stages (5 or 10 days old). Two levels of SCN inoculum (2,000 and 10,000 eggs/plant) and different timing between SCN and P. sojae inoculation (2, 5, or 8 days) were compared. The results on 5-day-old plants showed that SCN did not influence P. sojae development. The resistant cultivar to P. sojae remained effective (0% mortality) and susceptible cultivars exhibited high mortality (100%) in the presence or absence of SCN. Experiments on 10-day-old plants showed that SCN resistance was not affected by the presence of P. sojae. SCN inoculum density and timing of P. sojae infection did not affect the virulence of these pathogens and the efficacy of resistance genes. However, the number of SCN cysts was decreased by more than 50% (p < .001) when P. sojae was coinfesting the susceptible cultivar. This suggests that P. sojae might indirectly influence SCN development by reducing the root mass. This study confirmed that resistant cultivars remain a valid option for the management of P. sojae and SCN.     

控制大豆孢囊线虫生物种农剂的研制及沈阳田间小区防效的初步试验

以“辽豆15”为材料,采用田间小区试验,探讨了自行研制的生物种衣剂对大豆孢囊线虫数量的影响。试验结果表明：2007年在沈阳汪家的试验中,处理4（复配菌株F1024,B482,A4+微量元素组合3+助剂）对大豆根外孢囊的抑制率达65.66%,与对照有显著差异。2008年对处理4进行了精细的试验设计,并在2个不同地点布置试验,结果处理5（复配菌株F1024,B482,A4+元素组合+助剂）在汪家和康平2个试验点的根外孢囊数量及根内线虫数量都与对照差异达到显著水平,2个试验点的根外孢囊抑制率分别为 62.13%和46.45%,根内线虫抑制率分别为62.50%和81.78%。     

新疆大豆孢囊线虫病的初步研究

大豆孢囊线虫病是威胁大豆生产的主要病害之一。随机调查了大豆孢囊线虫（Heterodera glycines Ichinohe）在新疆的分布;运用鉴别寄主法鉴定新疆大豆孢囊线虫的生理小种;室内盆栽法测定新疆主栽大豆品种对大豆孢囊线虫的抗病性。结果表明大豆孢囊线虫主要分布在新疆阿勒泰地区,为4 号生理小种,新疆主栽大豆品种均为高感品种,研究结果将为控制新疆地区大豆孢囊线虫的危害提供理论依据。     

大豆孢囊线虫大豆和烟草群体寄生性比较分析

通过盆栽试验,测定大豆孢囊线虫(Heterodera glycines,soybean cyst nematode,SCN)大豆群体(SCNS)和烟草群体(SCN_T)对5个大豆品种(SCN生理小种鉴别寄主)和9个烟草栽培品种的寄生性。结果发现,SCNS在5个大豆品种上的平均繁殖系数(Rf=P_f/P_i)为0.60(0.14~1.90),在感病对照品种‘Lee’上平均Rf高达1.90;SCN_T在5个大豆品种上的平均Rf为0.18(0.06~0.44),在感病对照品种‘Lee’上Rf为0.44。SCNS对9个烟草品种几乎无寄生性,平均Rf为0.06(0.00~0.10);SCN_T则能寄生9个烟草品种,平均Rf为1.26(0.45~1.95)。接种35d后,在不同大豆品种根内SCNS和SCN_T的幼虫数量均极少,侵染率基本相同;在不同烟草品种根内SCNS的幼虫数量均为0,而SCN_T的幼虫数量平均为26.5(14.6~57.0)。研究表明,供试SCNS属于14号生理小种,但供试SCN_T与之寄生性差异大,属于新的SCN致病类型。     

Residues of atrazine, simazine, linuron and diuron after repeated annual applications in a peach orchard

Annual applications of the herbicides atrazine, simazine, linuron and diuron at 45 kg/ha were made to the same plots for 9 consecutive years from 1963 to 1971 in a peach (Prunus persica (L.) Batsch.) orchard located on sandy loam soil near Harrow, Ontario. Soil samples from these plots were collected in late October for the last 3 years (1969–1971) and trees were cut down in December, 1969. Herbicide residues were determined by bioassays based on the fresh and dry weight of oats (Avena sativa L.) and in one year results were confirmed by chemical analysis. Significant accumulation of herbicides was not observed. The maximum residue levels measured in October over the 3 years of sampling were 7′3 kg/ha for diuron, 3–8 kg/ha for linuron, 1–6 kg/ha for simazine and 04 kg/ha for atrazine in the top 15 cm of the soil profile. Simazine and atrazine showed a rapid decrease in amount after treatment but diuron and linuron were degraded more slowly. Measurable residues of all herbicides were confined to the upper 15 cm of the soil profile and the majority of herbicide remained in the 0–5-cm soil layer. Oats were planted in the orchard plots from 1972 to 1974 to follow the disappearance of the herbicides. All herbicides caused highly significant yield decreases in 1972, atrazine causing the least (38%) and diuron the greatest (86%) reductions. Diuron reduced the yield of oats in 1973 and caused a highly significant decrease in the weight of young oat plants in 1974.     

Monitoring glyphosate residues in transgenic glyphosate-resistant soybean

The availability of Roundup Ready (RR) varieties of soybean has increased the use of glyphosate for weed control in Argentina. Glyphosate [(N-phosphonomethyl)glycine] is employed for the eradication of previous crop vegetation and for weed control during the soybean growing cycle. Its action is effective, and low environmental impact has been reported so far. No residues have been observed in soil or water, either of glyphosate or its metabolite, AMPA (aminomethylphosphonic acid). The objective of this work was to monitor glyphosate and AMPA residues in soybean plants and grains in field crops in Santa Fe Province, Argentina. Five sites were monitored in 1997, 1998 and 1999. Individual soybean plants were sampled from emergence to harvest, dried and ground. Analysis consisted in residue extraction with organic solvents and buffers, agitation, centrifugation, clean-up and HPLC with UV detection. In soybean leaves and stems, glyphosate residues ranged from 1.9 to 4.4 mg kg(-1) and from 0.1 to 1.8 mg kg(-1) in grains. Higher concentrations were detected when glyphosate was sprayed several times during the crop cycle, and when treatments approached the flowering stage. AMPA residues were also detected in leaves and in grains, indicating metabolism of the herbicide.