白菜型冬油菜在北方寒旱区的适应性分析

采用多点试验,对白菜型冬油菜在北方地区的越冬率、生育期及产量进行比较,以分析其适应性.结果表明,不同冬油菜品种越冬率存在较大差异,依次表现为陇油6号＞陇油7号＞陇油8号＞陇油9号＞天油2号(CK)＞天油5号＞天油8号＞天油7号,其中陇油6号和陇油7号越冬率最高,分别为86.40％和85.53％,明显高于CK,而天油7号与天油8号的越冬率仅分别为54.07％和55.50％,均低于CK;同一参试品种在不同试点生育期差异较大,如陇油6号在秦王川试点,生育期长达300 d,而在和田,其生育期仅为251 d,较秦王川试点提前49 d;不同冬油菜品种间生育期差异也较大,在秦王川,陇油6号和陇油7号的生育期最长,为300 d,陇油8号为295 d,而其它各参试品种的生育期均为290 d,较陇油6号缩短了10 d;在不同试点,冬油菜农艺性状和含油率均存在较大差异.综合分析,陇油8号、陇油7号、陇油6号的丰产性和稳定性最好,其次为陇油9号;不同生态区区域适宜种植的冬油菜品种也有差异,其中陇油6号、陇油7号可成为北京及周边地区、新疆乌鲁木齐以西地区、甘肃中北部与河西走廊以及陕西靖边周边地区的主栽品种,而新疆乌鲁木齐以南地区应以陇油8号与陇油9号为主栽品种,天油2号、天油5号及天油8号也适宜在该地区种植.     

北方旱寒区冬油菜根系抗寒指标分析

为了研究北方旱寒区冬油菜根部生理特性与其抗寒性的相关性,对6个不同抗寒性冬油菜品种整个生育期根部的干物质积累、含水量、可溶性蛋白含量及相关保护性酶活性的变化进行了分析,并将各指标与越冬率进行了相关性分析,用与越冬率相关性显著、极显著的6个指标对冬油菜进行聚类分析。结果表明,降温前,各指标与越冬率的相关性均不显著;降温后,越冬率与可溶性蛋白含量、SOD活性极显著正相关,与POD、APX活性显著正相关,与根直径、根冠比、CAT活性正相关,与根含水量负相关;根据聚类分析结果,可将试验材料分为3类,第1类：07－G01,天油2号,天油4号,此类抗寒性弱,为耐寒性品种;第2类：上党,74－1,此类抗寒性一般,为中抗寒性品种;第3类：陇油6号,此类抗寒性强,为强抗寒性品种。由此推断,在北方旱寒区,冬油菜越冬前根直径大、根冠比高、根含水量低有利于冬油菜安全越冬;降温后,冬油菜可溶性蛋白、SOD、POD 、CAT和APX酶活性值越高,其抗寒性越强。     

北方强冬性区白菜型冬油菜临界安全越冬率及产量补偿效应分析

以3个不同抗寒性的白菜型冬油菜品种为材料,在模拟不同越冬条件下,探讨越冬率对强抗寒性白菜型冬油菜产量、株型性状、角粒性状、生育期等的影响。结果表明:当越冬率在30%～100%范围内,随越冬率的增加,白菜型冬油菜产量呈先增加后降低的趋势,陇油7号、冬油2号越冬率为85%时产量分别为4 462.2 kg·hm~(-2)和4 057.0 kg·hm~(-2),达到最高值;天油4号越冬率为90%时产量最高,为3 591.8 kg·hm~(-2)。方差分析表明,陇油7号和天油4号越冬率大于75%,冬油2号越冬率大于70%时,越冬率变化对其产量水平无显著影响,而越冬率低于这一阈值时,其产量显著降低。回归分析表明,白菜型冬油菜越冬率与其产量的关系符合线性模型;相关性分析表明,白菜型冬油菜越冬率变化与植株分枝部位呈显著正相关(P0.05),与单株分枝数、角果长度和数量、粒数和粒重、单株重量等呈显著负相关(P0.05),种子、角果和侧枝的干鲜质量及蔗糖含量与越冬率变化呈显著或极显著负相关(P0.01或P0.05)。因此,冬前播种密度保持在65万株·hm~(-2)时,我国北方强冬性区白菜型冬油菜安全越冬临界值范围为70%～75%,不同品种的安全临界越冬率存在差异;在一定范围内,增加白菜型冬油菜的分枝和结实性能,对返青群体不足导致的产量损失具有补偿效应。     

冬油菜覆盖对土壤理化性状及微生物的影响

于2021—2022年在甘肃省兰州市永登县上川镇甘肃农业大学油菜育种基地设置5个不同类型冬油菜覆盖处理，即‘陇油7号’覆盖(SC)、‘天油2号’覆盖(WC)、‘陇油99’覆盖(LX)、‘陇油88’覆盖(SR)、‘天油2288’覆盖(WR),以冬闲无覆盖为对照(CK),通过研究冬闲田不同类型冬油菜覆盖对土壤理化性质及微生物的影响，以期为该区筛选适宜秋冬闲田覆盖的油菜类型提供依据。结果表明：五叶期白菜型覆盖量比甘蓝型高，进入越冬期后甘蓝型覆盖量高于白菜型；白菜型品种和甘蓝型品种均具有良好的覆盖效果，甘蓝型品种‘陇油88’和白菜型品种‘陇油99’在不同时期的覆盖效果各有优势，二者均可以作为冬闲覆盖材料。冬前甘蓝型覆盖各项光合指标均高于白菜型，甘蓝型品种较白菜型具有覆盖优势。冬油菜覆盖具有降低土壤容重和提高土壤孔隙度的作用，随土层深度的增加土壤容重和土壤孔隙度均表现为先升高后降低；冬油菜覆盖可以增加0～30 cm土层土壤含水量，白菜型覆盖的保水效果优于甘蓝型覆盖。与CK相比，覆盖处理0～30 cm土层土壤全氮、全磷、全钾、铵态氮、硝态氮含量分别增加了54.00%、85.00%、20.62%、1...     

外源ABA浸种对冬油菜种子萌发及幼苗抗寒性的诱导效应

为探讨外源脱落酸（ABA ）对北方寒旱区冬油菜幼苗抗寒性的诱导效应,试验分别用不同浓度的ABA对超强抗寒性白菜型冬油菜品种“陇油6号”和弱抗寒性品种“天油2号”进行浸种处理,研究不同浓度ABA浸种对冬油菜种子萌发及常温和低温胁迫条件下相关抗寒指标的影响。结果表明,10～70 mg · L－1 ABA处理促进了种子萌发,80 mg·L－1ABA处理对发芽率和发芽势有抑制作用;30 mg·L－1浓度的ABA对冬油菜抗寒性诱导效果最佳,可显著（P＜0．05）提高冬油菜幼苗抗氧化酶（SOD、POD和CAT）活性,延缓叶绿素含量的降低,增加叶片脯氨酸含量,减缓膜脂过氧化产物丙二醛的积累;外源ABA处理在品种上存在差异,对抗寒性强的品种陇油6号效果明显。     

白菜型冬油菜和春油菜杂交后代抗寒性与植物学特性

对强抗寒性白菜型冬油菜陇油7号和陇油9号与优质白菜型春油菜品种Parkland杂交后代群体的感温性(冬春性)、植物学特性、越冬率等进行了初步分析研究。结果表明:(1)两个杂交组合的F1代植株全部表现为冬性,可见冬性为显性,F2代和BC1冬春性发生分离,F2代冬春性均符合4∶1的分离,而BC1中以Parkland为轮回亲本时,后代冬春性符合1∶1的分离,以陇油7号和陇油9号为轮回亲本时,后代冬春性之比为4∶1。(2)以越冬率为抗寒指标分析发现陇油7号×Parkland杂交后代的抗寒性比陇油9号×Parkland杂交后代抗寒性强,这与冬性亲本抗寒性强弱一致,各世代抗寒性强弱依次是:以冬性为轮回亲本的BC1F2F1春性为轮回亲本的BC1。(3)相关性和灰色关联分析表明,越冬率与冬春杂交后代主要生物学特性紧密相关,相关程度依次为:心叶色生长习性冬春性叶色。分析得出,植株形态特征与抗寒性有密切的关系,一般心叶为紫色、叶色深绿或浅绿、匍匐或半直立生长的幼苗,其越冬率较大,抗寒性较强。     

基于GGE双标图对向日葵品种丰产性和稳定性的综合评价

为了测试不同油用型向日葵品种的丰产性和稳定性以及各试验点的区分力和代表性，利用GGE双标图对我国油葵主产区12个试点的11个品种的产量、茎粗、株高和籽仁率进行综合分析评价。结果表明：基因型(G)、环境(E)及基因型与环境的互作效应(GE)对产量都有极显著影响(P<0.01),其中E和GE是引起产量变异的主要原因，两者分别占总变异的84.84%和8.35%。利用GGE双标图模型分析可知，高产稳产品种中表现最好的是‘LJ199’,其次是‘NK175’和‘LKZ18-1’,它们都适合在沈阳和公主岭等类似地区推广种植，‘NK50’也具有较高的产量和稳定性且在甘南县、兰州市和汾阳市等类似地区的适应性较好；综合区分力和代表性，最理想的试点为公主岭。兰州市、呼和浩特和乌鲁木齐分别是茎粗、株高和籽仁率最理想的试点。文中初步确定了适合在不同生态环境下种植的向日葵品种，为品种推广及后续区域试验提供了理论依据。     

微管调节试剂对白菜型冬油菜萌动种子内源激素及抗寒基因表达的影响

以‘陇油7号’和‘天油4号’2个抗寒性不同的白菜型冬油菜为试验材料,通过添加400μmol·L^-1秋水仙碱(微管聚合抑制剂)和50μmol·L^-1紫杉醇(微管聚合促进剂)试剂后,在20℃和0℃下分别处理12 h和24 h,随后采用液相色谱质谱联用仪和荧光定量PCR测定萌动种子内源激素含量及抗寒基因表达量,研究微管调节试剂对白菜型冬油菜萌动种子内源激素和抗寒基因的影响。结果表明：与对照相比,添加秋水仙碱后,在0℃和20℃处理下‘陇油7号’和‘天油4号’ABA、IAA、GA₃、ZT含量明显降低;添加紫杉醇后,‘陇油7号’和‘天油4号’ABA、IAA、GA₃、ZT含量明显升高。添加秋水仙碱后,与0℃处理12 h相比,0℃处理24 h时,‘陇油7号’α-tubulin、β-tubulin、MKK2、ICE1、CBF1、BrAFP1的表达量增加,‘天油4号’α-tubulin、β-tubulin、CBF1表达量增加,但MKK2、ICE1、BrAFP1的表达量降低;与20℃处理12 h相比,20℃处理24 h时...     

越冬前北方不同类型强冬性冬油菜形态及生理响应研究

为了研究比较越冬前北方两种不同类型冬油菜的生长特性,于2020年10—11月选用强冬性白菜型冬油菜和强冬性甘蓝型冬油菜品种,分析其越冬前降温过程中的形态特征、光合特性和渗透调节物质含量变化,并与越冬率进行了相关性分析。结果表明,越冬前随着温度的降低,白菜型冬油菜根冠比增加164.7%,甘蓝型冬油菜根冠比变化不大,两个品种间差异显著,但二者组织含水量变化为69%~89%,变化幅度较小。随着温度的降低,白菜型冬油菜和甘蓝型冬油菜的叶面积逐渐减小,下降幅度为5%~16%,叶绿素SPAD值整体呈现增加的趋势;光合速率、蒸腾速率、气孔导度均逐渐下降,降幅为54%~64%,胞间CO₂浓度逐渐上升19%~29%。叶片和根部的可溶性蛋白、脯氨酸含量均增大,增幅为26%~91%;叶片可溶性糖含量先增加后降低,根部可溶性糖含量先降低后增加。叶片的钠离子和钾离子含量逐渐降低了20%~47%,钙离子含量先增加后降低;根部钾离子和钙离子含量先下降后上升;白菜型冬油菜根部钠离子含量呈现出逐渐上升的趋势,甘蓝型冬油菜呈现出先上升后下降的趋势。由此推断白菜型冬油菜陇油6号的抗寒性强于甘蓝型冬油菜2019-QL-GAU-30。     

北方旱寒区冬油菜抗寒性相关指标的QTL定位

以抗寒性不同的白菜型冬油菜品种陇油7号与陇油9号为亲本构建的F2群体为材料,对白菜型冬油菜抗寒性相关的生理指标进行了QTL定位分析。在白菜型油菜的10条染色体上定位了SOD活性、POD活性、CAT活性、MDA含量、游离脯氨酸含量和可溶性蛋白含量共6个性状的24个QTL位点,可解释表型变异为11.1783%~81.1753%;10个显性效应表现为显性正效应,LOD值在3.2787~163.7958之间。染色体2A的Br ID90127-Br ID10421区、Br ID10421-Br ID10709区及Br ID10709-Br ID101165区,5A的BRMS034(R5)-Ra3-H10区、6A的Ra1-F06-Ra2-D04区、8A的Br ID10839-Ra2-E12区和10A的Br ID90115-Ra2-E07区是多个性状QTL共享的标记区间。研究结果对冬油菜抗寒性基因精确定位具有一定价值。     

Epidemiology and simulation of population development of Sitobion avenae in winter wheat

The epidemiology ofSitobion avenae and its natural enemies in winter wheat was studied in 1975, 1976 and 1977. Immigration was important until the end of flowering. The alate immigrants had apterous offspring. These became the driving force in population growth. Their offspring were mostly alatae which usually left the field. A model of the epidemic was developed. Quantitative relations between the aphids and their environment were obtained from literature or established in laboratory trials. The model simulated population development and population composition from the beginning of June till the population peak at the end of June or early in July. Because quantitative data on relations between aphids and their natural enemies and pathogens are scarce, and since the knowledge on wing formation is still limited, the population collapse could not be predicted. In the future, prognosis over a period of three weeks seems possible.Samenvatting De toenemende betekenis van graanbladluizen (vooralSitobion avenae) gepaard gaande met een sterke toename van het gebruik van insecticiden op granen maakte verbetering van de prognose over het schadelijk optreden wenselijk. Door gedetailleerde tellingen in het veld (Fig. 1–7) werden gegevens verkregen over het verloop van de epidemie en het optreden van natuurlijke vijanden in 1975, 1976 en 1977.Een immigratieperiode tot in de bloei kon worden vastgesteld. Daarna lijkt de aantrekkelijkheid van het gewas voor alate luizen te verminderen. De alate immigranten krijgen aptere nakomelingen. Deze vormen de stuwende kracht van de populatiegroei. De nakomelingen van apteren zijn merendeels alaat. Zij verlaten het gewas.Een model van de populatieontwikkeling gedurende de epidemie werd opgesteld. De relatiediagrammen Fig. 9 en 10 laten groei en ontwikkeling vanS. avenae en een predator (Syrphus corollae) zien. Kwantificering van de betrekkingen werd mogelijk door literatuurgegevens en laboratoriumexperimenten.Met het model kon de populatieontwikkeling vanS. avenae vanaf begin juni tot aan de populatiepiek in 1975, 1976 en 1977 vrij goed worden gesimuleerd (Fig. 12). Ook de populatieopbouw kon worden gesimuleerd (Fig. 14). De teruggang van de populatiedichtheid blijkt moeilijker te voorspellen door het ontbreken van gegevens over natuurlijke vijanden.Het lijkt waarschijnlijk dat in de toekomst met het model een prognose over de piek van de bladluispopulatie circa 3 weken tevoren mogelijk zal zijn.     

Tumours of Begonia and some other ornamentals,induced by Corynebacterium fascians

In 1975 many tumours were observed in plants ofBegonia Schwabenland grown in Aalsmeer. Submersion of the roots ofNicotiana megalosiphon seedlings in a homogenate of tumorous tissue, induced tumours after two weeks. Short periods of submergence yielded results similar to those obtained after longer periods. Tumour homogenates lost their infectivity after ten min at 50°C. Aphids transmitted the infectious agent.Treatment with propylene oxide did not inhibit infectivity completely. Filtration through a 450 nm filter removed the infectious agent.Tobacco tumor virus or a viroid could not be isolated. Cultures ofCorynebacterium fascians, isolated from tumours ofN. megalosiphon were highly infectious and induced tumours in healthyN. megalosiphon andBegonia. Tumorous tissue homogenates ofPelargonium zonale, Dahlia sp.,Gladiolus sp., andLilium sp. also caused tumours inN. megalosiphon, from whichC. fascians was isolated. It was not possible to produce tumours inN. megalosiphon with homogenates from roses with symptoms of bud proliferation.Samenvatting In 1975 werden vele tumoren waargenomen inBegonia Schwabenland op Aalsmeerse bedrijven (Fig. 1). De infectiositeit van tumorweefsel kon goed en snel worden vastgesteld door de wortels van zaailingen vanNicotiana megalosiphon in een homogenaat van tumorweefsel te dompelen. Tumoren ontstonden na twee weken, de eindbeoordeling geschiedde na een maand (Fig. 2). Ook verschillende andereNicotiana spp.,Melilotus officinalis (Fig. 3) enPisum odoratum (Fig. 4) werden aangetast.Bij de infectiositeitstoets gaven zeer korte dompeltijden even goede resultaten als langere (Tabel 1). Infectieus sap verloor zijn infectievermogen na 10 min verhitting bij 50°C. Bladluizen brachten de smetstof over. Propyleenoxide verminderde de infectiositeit wel, doch onderdrukte deze niet totaal. Bij filtratie door een 450 nm filter bleef het infectieuse agens op het filter achter. Het tumor-inducerende agens was ook aanwezig in die delen van planten met tumoren welke gezond leken en het ging voor een gering deel over met zaad (Tabel 2).Uit tumoren konden wij geen tabakstumorvirus of een viroïde isoleren. Culturen vanCorynebacterium fascians, geïsoleerd uit tumoren vanN. megalosiphon bleken zeer infectieus en veroorzaakten tumoren inN. megalosiphon enBegonia. Homogenaten van tumorweefsel vanPelargonium zonale, dahlia (Fig. 5), gladiool (Fig. 6) enLilium Mid Century Hybrid Enchantment (Fig. 7) veroorzaakten ook tumoren opN. megalosiphon, waaruitC. fascians werd geïsoleerd. Met sap van kroeskopzieke rozen konden wijN. megalosiphon niet besmetten.     

A Survey of Trunk Disease Pathogens within Rootstocks of Grapevines in Spain

Grapevine trunk disease pathogens, and specifically Petri disease pathogens, can be spread by planting infected plants. Due to the increasing incidence of Petri disease and other young grapevine declines reported lately in Spain, a sampling of plants used before for new vineyards were carried out in 2002 and 2004. A total number of 208 plants (grafted and non grafted) were collected, of which 94 plants (45.2%) were infected with at least one of the following pathogens: Phaeomoniella chlamydospora, and species of Phaeoacremonium, Botryosphaeria, Cylindrocarpon, and Phomopsis. Species of the genera Phaeoacremonium and Botryosphaeria isolated in 2004 were identified using morphological and molecular characters. Species of Phaeoacremonium identified were P. aleophilum and P. parasiticum; and those of Botryosphaeria were B. obtusa, B. dothidea and B. parva. This is the first report of P. parasiticum and B. parva occurring on grapevines in Spain. Distribution of pathogens within the plants was studied in 2004. Phaeomoniella chlamydospora was not detected in the graft union of any plant; however, species of Botryosphaeria and Phomopsis were detected along the plant, but mainly in the graft union; Phaeoacremonium aleophilum was detected along the grafted plants, but not in rooted rootstocks. The results suggest that infected plants used for new plantings in Spain are an important source of primary inoculum of the pathogens associated with grapevine trunk diseases in the field.     

A new <Emphasis Type="Italic">Rhizoctonia</Emphasis> sp. closely related to <Emphasis Type="Italic">Waitea circinata</Emphasis> causes a new disease of creeping bentgrass

Isolates of an unidentified Rhizoctonia sp. (UR isolates) were obtained from creeping bentgrass and Kentucky bluegrass with reddish brown sheath and foliar rots. Because the UR isolates anastomosed with isolates of three varieties of Waitea circinata (var. oryzae, var. zeae, and var. circinata), colony morphology, hyphal growth rate at different temperatures, pathogenicity, sequence analysis of the internal transcribed spacers (ITS) region of ribosomal RNA genes (rDNA) were compared. The colony color of mature UR isolates was distinct from isolates of the other three varieties of W. circinata. In pathogenicity tests on creeping bentgrass, the severity of the disease caused by UR isolates was significantly higher than that caused by the three varieties of W. circinata. Sequence similarities of the rDNA-ITS region between UR isolates and between isolates within each variety were high (97–100%), but they were lower among isolates from UR and the varieties of W. circinata (88–94%). In a phylogenetic tree based on the rDNA-ITS sequences, UR isolates formed a cluster separate from each of the clusters formed by the three varieties of W. circinata. These results indicate that the UR isolates clearly differ from the three varieties of W. circinata. We therefore propose that the UR isolates be classified as new Rhizoctonia sp. that are closely related to W. circinata and that the disease on creeping bentgrass should be called Waitea reddish-brown patch disease (Sekikasshoku-hagusare-byo in Japanese).     

Identification,incidence and characterization of <Emphasis Type="Italic">Fusarium proliferatum</Emphasis>on ornamental palms in Spain

During a survey conducted from 1998 to 2002, Fusarium proliferatum was found associated with young and adult palms belonging to the genera Chamaerops, Phoenix, Trachycarpus and Washingtonia showing symptoms of wilt and dieback. The fertility and toxicological profile of 36 strains representing different locations and hosts were studied. All of them except two, which were infertile, belonged to mating population D. Both mating types (MATD-1 and MATD-2) were isolated from the same host species, showing a high potential of genetic recombination in the field. Additionally, eight strains were fertile once crossed as female. Toxin analysis showed differences in the ability of strains to produce fumonisin B₁, moniliformin, beauvericin, fusaric acid and fusaproliferin. Only 17 of them produced all the toxins analyzed. Pathogenicity tests were conducted on Phoenix dactylifera and P. canariensis using nine F. proliferatum Spanish strains and two reference strains from Saudi Arabia. Eight months after inoculation all strains caused disease, with palms showing lesions on the bases of leaves and development of wilt symptoms similar to those originally observed in affected plants. This is the first report on the occurrence of F. proliferatum on P. dactylifera in Spain and also the first report of this pathogen on C. humilis, P. canariensis, P. reclinata, T. fortunei, W. filifera and W. robusta.     

橡胶树白粉菌Oidium heveae侵染寄主拟南芥的筛选

为筛选出橡胶树白粉菌Oidium heveae Steimnann新的寄主载体,通过接种野生型拟南芥Col-0、突变体Sr1-4D及eds1,观察了橡胶树白粉菌侵染不同拟南芥突变体的过程,PCR扩增测序法验证相关致病基因,构建橡胶树白粉菌-拟南芥互作体系。结果表明,在Col-0、Sr1-4D叶片上面,橡胶树白粉菌产生部分菌丝后停止生长,不能形成典型的橡胶树白粉病症状;但能成功侵染eds1叶片,在叶片的正、背面有银白色辐射状菌丝,后期在病斑上出现一层粉层,表现橡胶树白粉病的典型症状。组织染色和显微观察结果显示,在突变体eds1叶片上橡胶树白粉菌完成了侵染过程。PCR扩增测序结果表明接种后突变体eds1叶片上及组织中病菌均为橡胶树白粉菌;使用橡胶树白粉菌3个致病相关基因作为靶标,验证了eds1和橡胶树上白粉菌基因组中的3个致病相关基因相似度均达到99%~100%。表明橡胶树白粉菌可侵染拟南芥突变体eds1。     

Nematicidal Activity of Chrysanthemum coronarium

Organic amendments and green manure are potential alternatives to the harmful chemical control means currently used against plant-parasitic nematodes. In this work, Chrysanthemum coronarium was applied to the soil as a green manure to control the root-knot nematodes Meloidogyne incognita and M. javanica. Chrysanthemum coronarium significantly reduced nematode infection of tomato roots and improved plant-top fresh weight, both in the greenhouse and in microplots. Other green manures, derived from Anthemis pseudocotula, wild chickpea (Cicer pinnatifidum), Geranium spp. and wheat, were not as effective as C. coronarium. Chrysanthemum coronarium, retained its nematicidal activity even when applied as a dried material. Only mature C. coronarium plants, in their flowering stage, exhibited nematode control activity, but the green plant parts were more effective than the flowers. An aqueous extract of C. coronarium exhibited in vitro, nematostatic activity towards M. incognita and M. javanica second-stage juveniles and inhibited their hatching from eggs and egg-masses; its nematostatic activity was expressed also against other phytonematode species such as Heterodera avenae and Pratylenchus mediterraneus, but did not affect the beneficial entomopathogenic nematode Steinernema feltiae.     

Biocontrol agents in combination with Moringa oleifera extract for integrated control of Sclerotium-caused cowpea damping-off and stem rot

Damping-off and stem rot disease-causing Sclerotium rolfsii has been reported as a destructive soil-borne pathogen of numerous crops, especially in the tropics and subtropics. Trials were conducted to test the efficacy of biocontrol agents alone or combined with Moringa oleifera leaf extracts for the control of the disease. In the laboratory, PDA was amended with Moringa leaf extract, and mycelial growth of S. rolfsii was measured. In the greenhouse and field, Trichoderma Kd 63, Trichoderma IITA 508 and Bacillus subtilis were evaluated as seed treatments, soil drench or sprinkle, separately or combined with Moringa leaf extracts. Percentage disease incidence, severity and control were recorded. In the laboratory, the higher the extract concentration the less the mycelial growth and no mycelial growth occurred on extract at 15 or 20 g leaves 10 ml⁻¹ water. In the greenhouse, the highest disease control was observed at a Moringa extract concentration of 15 kg leaves 10 l⁻¹ water (w/v). Seed treatments using Trichoderma Kd 63, and soil sprinkle using Trichoderma IITA 508 had a significantly (P = 0.05) higher effect on a disease incidence than Bacillus. Disease severity followed the same pattern. Moringa seed treatment combined with Trichoderma soil sprinkle resulted in significantly more than 94% and 70% disease control in the greenhouse and field, respectively, with significant yield increase in the field. This is the first report of Moringa leaf extract combined with Trichoderma as an integrated control for Sclerotium damping-off and stem rot of cowpea in the field.     

Population structure of the rice sheath blight pathogen <Emphasis Type="Italic">Rhizoctonia solani</Emphasis> AG-1 IA from India

The population structure of Rhizoctonia solani AG-1 IA causing rice sheath blight from India was evaluated for 96 isolates using seven RFLP loci. Nineteen of the isolates did not hybridise to R. solani AG-1 IA RFLP probes and rDNA analyses subsequently confirmed that they were either Ceratobasidium oryzae-sativae isolates or another Rhizoctonia sp. The population structure of the remaining 77 R. solani AG-1 IA Indian isolates was similar to that of a previously characterized Texas population. Clonal dispersal of R. solani AG-1 IA in India was moderate within fields and no clones were shared among field populations. Low levels of population subdivision and small genetic distances among populations were consistent with high levels of gene flow. Frequent sexual reproduction was indicated by the fact that most populations were in Hardy–Weinberg equilibrium (HWE). The two loci (R68 and R111) that deviated significantly from HWE showed an excess of heterozygosity. Although Texas and Indian populations were geographically very distant, they exhibited only moderate population subdivision, with an F_ST value of 0.193.     

Inactivation of soil-borne plant pathogens during small-scale composting of crop residues

Samples of heavily infested crop residues were incorporated in static compost heaps (2.5–4.6 m³) of the Indore type. Temperature increased to 50–70°C within 6 days depending on the type of crop residues used and the location within the heap. The heat phase (>40 °C) lasted 2–3 weeks and was followed by a c. 5-months maturation phase (<40 °c).=" among=" the=" 17=" pathogens=" tested,=">Olpidium brassicae and one of the four formae speciales ofFusarium oxysporum that were tested survived composting, but also their inoculum was greatly reduced.Survival during specific phases of composting was studied by incorporation and retrieval of samples at various stages of the process.F. oxysporum f. sp.melonis was completely inactivated andO. brassicae andPlasmodiophora brassicae were almost completely inactivated during the short heat phase. The three pathogens survived the long-lasting maturation phase without loss of viability. Heat evolved during composting was found to be the most important factor involved with sanitation of crop residues. The possible involvement of fungitoxic conversion products and microbial antagonism is discussed.