Protection of potato from Rhizoctonia canker with binucleate Rhizoctonia fungi

Fifteen isolates of binucleate Rhizoctonia fungi (BNR) were studied as potential biocontrol agents for protection of potato from Rhizoctonia canker in artificially infested greenhouse soil and potato fields naturally infested with Rhizoctonia solani (AG-3). Eight of the BNR reduced incidence and severity of Rhizoctonia stem canker in greenhouse experiments by an average of 78 and 85%, respectively. In a field naturally infested with R. solani, selected isolates of BNR and the fungicide Tops 2.5D (thiophanate-methyl) were equally protective of potato from Rhizoctonia stem canker. BNR isolates gave protection of potato from Rhizoctonia stolon canker similar to PCNB and superior to Tops 2.5D. Cultivars Atlantic, Irish Cobbler, Kennebec, Norchip, Russet Burbank, and Superior were protected equally from Rhizoctonia stem canker by selected isolates of BNR under field conditions. Isolates of BNR show potential as biocontrol agents for protection of potato from Rhizoctonia canker.     

Rhizoctonia Blight of Yacon Caused by Rhizoctonia solani AG-1 (IB)

Severe blight of stems and leaves caused by Rhizoctonia solani AG-1 (IB) was found on yacon (Smallanthus sonchifolius), a Compositae tuber crop, grown in Ehime Prefecture, Japan, from August to September 1996 and 1999. We named it “Rhizoctonia blight of yacon” as a new disease. Received 15 October 2001/ Accepted in revised form 25 November 2001     

Association of Binucleate Rhizoctonia with Soybean and Mechanism of Biocontrol of Rhizoctonia solani

ABSTRACT The association of binucleate Rhizoctonia (BNR) AG-K with soybean and the interaction of BNR, R. solani AG-4, and soybean seedlings were investigated to elucidate the mechanism of biocontrol of R. solani by BNR. Sixty-hour-old seedlings were inoculated and incubated in a growth chamber at 24 degrees C; plants were examined with light microscopy and with scanning and transmission electron microscopy at various times following inoculation. BNR grew over hypocotyls, roots, and root hairs, but only colonized epidermal cells. Hyphae of BNR appeared to attach to the epidermis and, 5.5 h following inoculation, began penetrating cells by means of penetration pegs without forming distinct appressoria or infection cushions. There was evidence of cuticle degradation at the point of penetration. Infection hyphae moved to adjacent epidermal cells by direct penetration of epidermal radial walls. There were epidermal and cortical cell necrosis, beginning with the fragmentation of the tonoplast and followed by the disintegration of cytoplasm, organelles, and plasma membranes. Cell necrosis was also observed in adjacent cells where there was no evidence of BNR hyphae. Cell walls were not destroyed. After 144 h, there was noevidence of BNR hyphae in cortical cells. Attempted penetrations were observed, but papillae formed on the inside of cortical cell walls. Pre-inoculation of soybean seedlings with BNR 24 or 48 h before inoculation with R. solani (1 cm between inocula) affected the growth of R. solani on soybean tissue. There were fewer hyphae of R. solani, the hyphae branched sparingly, and infection cushions were rare when compared with hyphal growth on soybean inoculated only with R. solani. These effects were observed before the BNR hyphae began to intermingle with the hyphae of R. solani on the surface of the inoculated host. Preinoculation of soybean seedlings 24 h before inoculation with R. solani significantly (P = 0.05) reduced disease incidence and severity caused by R. solani AG-4. The lesions caused by R. solani always appeared distally, not proximally, to the BNR inoculum. The interactions of intermingling hyphae of BNR and R. solani were examined in vitro and on the surface of the host. There was no evidence of lysis, mycoparasitism, inhibition of growth, or any other form of antagonism between hyphae. The results of these studies strongly suggest that induced resistance is the mechanism of biocontrol of R. solani on soybean by BNR. The inhibition of hyphal growth of R. solani on the surface of soybean tissue preinoculated with BNR appears to be a novel characteristic of induced resistance.     

立枯丝核菌的生物防治

本文扼要叙述了立枯丝核菌生防因子的种类生防几生防因子在根部的定殖,并讨论了有关问题。     

立枯丝核菌重寄生真菌的筛选

 从捕食线虫的真菌中筛选到立枯丝核菌(Rhizoctonia solani)的8种重寄生真菌,即粉红粘帚霉(Gliocladium roseum),少孢节丛孢(Arthrobotrys oligospora),弯孢节丛孢(A.musiformis),贵州节丛孢(A.guizhouense),圆锥节丛孢(A.conoides),指状节丛孢(A.dactyloides),多孢节丛孢(A.superba),蠕虫状节丛孢(A.vermicola)。平板测试表明这8种重寄生菌能不同程度地影响立枯丝核菌的生长,减少菌核的形成数量。其中粉红粘帚霉的寄生力最强,可使菌核数减少58.67%,交叉菌落内几乎所有的立枯丝核菌菌丝被寄生。营养条件对重寄生有明显的影响,在低营养培养基CMA和WA上寄生程度严重,在营养相对较高的PDA和CSA上寄生程度较轻。太高的C:N (300:1)和太低的C:N (1:1,10:1)都不利于重寄生,只有适当的C:N (50:1,100:1)才有利于重寄生     

Degradation of Nitralin by Rhizoctonia solani

Degradation studies of nitralin [4-(methylsulfonyl)-2.6-dinitro-N.N-dipropylaniline] were performed with pure cultures of Rhizactoma solani Kühn. Czapek Dos Broth was selected as the growth medium and contained no components which interfered with extraction and subsequent TLC analysis. Ten to I I degradation products were detected after 14 to 21 days incubation at 33°C, The nonpolar fraction (ethyl acetate exlraclahkl contained at least nine compounds visible on TLC plales. Only one product other than the parent nitralin was identified the monoalkylated derivate. 4-(meihylsulfonyl)-2.6-dinitro-N-pro-pylanilinc. After 21 days approximately 10% of the original nitralin could be detected. The aqueous phase (after ethyl ace-late extraction) was concentrated, placed on a Sephadex G10 column and separated into at leasi two products. No ¹⁴CO₂ evolution was detected from ¹⁴C-ring labeled nitralin. Dégradation de la nilralinepar Rhizoclonia solani Dcs ètudes de dégradation de la nitraline [4-(méthylsulfonyl)-2,6-dinitro-N,N-dipropilanihne) ont été effectuées avec des cultures pures de Rhizurtvnia solani Kühn. Le milieu de culture de Czapek. Dox, Broth, a été choisi; il ne contenait pas de composés qui auraient pu interférer a vet I'extraction el avec l'analyse chromalographique en couchc mince ulténeure. Dtx à 11 produits de dégradation ont été décelés après 14 à 21 jours d'incubation à 33 C, La fraction non polaire (extructible par l'acétate d'éthyle) contenait iu minimum 9 composés visibles sur les chromatogrammes Un produit seulement. autre que la nitralinc apparentée. a été identific. le dèrivé monoalkylé. 4-(methylsulfonyl)-2.6-dinilro-N-propylflniline, Aprés 2l jours. 10% environ de la nitralinc origmale avait pu ètre décelée. La phase aqueuse (aprés extraction à l'acétate d'ethyle) a été con-centrée. placée sur une colonne de Scphadex G10 el séparée en deux produits au moins. II n'a pas été décelé d'èevolution du ¹⁴CO₂ provenant du cycle marqué au ¹⁴C de la nitraline. Abhau van Nitrulirt durch Rhizoctonia solani Es wurden Abbaustudien mit Nitralin unter Verwendung von Rcinkulturen von Rhizoctonia solani Kühn durchgeführt. Also Wuchsmedmm wurde Czapek Dox Broth verwendet. das keine Substanzen enthielt. die die Extraktion und die daraffogende dünnschichtchromatographische Analyse störten. Nach einer Inkuhationszeit von 14 bis 21 Tagen nei einer Temperatur von 13°C. fturden 10 bis 11 Abbauprodukte nachgewiesen. Die nicht-polare Fraktion (extrahierbar mil Äthylacetal) enthielt mindestens 9 auf Dünnschichtplatten sichtbare Verbindungen Eine Substanz wurde identifiziert—das monoalkylierte Derivat 4-(Methylsulfonyl)-2.6-dinitro-N-propylanilin Nach 21 Tagen konnten noch ungefähr 10% des ursprünglichen Nitralins nach. gewiesen werden. Die wässrige Phase (nach Extraktion mit Äthylacetat) wurde eingeengt und auf einer Sephadex G 10 Säule in mindestens 2 Verbindungen aufgetrennt. Aus ^l4C-ring-markiertem Nitralin konnte keine ¹⁴CO₂ -Freisetzung nachge-wiesen werden.     

水稻纹枯病拮抗菌的筛选及田间小区防治水稻纹枯病的效果

水稻纹枯病 (Ｒｈｉｚｏｃｔｏｎｉａｓｏｌａｎｉ)是水稻三大病害之一。当前 ,生产上主要用井冈霉素加以防治 ,但长期使用此药 ,已使纹枯病菌产生了抗药性。本研究针对四川稻区纹枯病菌ＡＧ Ｉ融合菌丝群 ,进行拮抗细菌的筛选及生防潜力研究。1　材料和方法1 1　供试菌　水稻纹枯病菌菌丝融合群ＡＧ Ｉ菌株及供试木霉 (Ｔｒｉｏｈｏｄｅｒｍａｖｉｒｄｅ) ,由四川农业大学水稻研究所病理研究室分离 ;水稻品种两优 6 81Ｆ1代种 ,由四川农业大学水稻研究所杂交稻中试开发公司提供。1 2　拮抗细菌的分离和筛选　将从各地采集的水稻根、茎、…     

人参立枯病的发生与防治

人参立枯病是人参苗期的主要病害,在靖宇县各参区普遍发生,一般发病率为８％～２５％,严重时可造成参苗成片死亡,损失严重。目前已成为影响靖宇县参苗生产的一个主要限制因子。为了解决这一生产难题,１９９８年,我们对人参立枯病的发生特点及防治技术进行了初步的研究和探讨,结果如下：１　症状立枯病不仅为害１～２ａ生幼苗,而且３ａ以上的参苗在出土初期亦受害,但以１～２ａ生幼苗受害最重。其主要症状是：在参苗的茎基部,即距土表３～５ｃｍ的干湿土交界处,初现浅黄褐色的病斑,后呈黄褐色凹陷长斑,严重时茎基部腐烂或缢缩呈…     

Resistance in Rhizoctonia solani to tolclofos-methyl

Isolates ofRhizoctonia solani were adapted in vitro to grow on a medium amended with tolclofos-methyl at a concentration 500 times that which initially almost completely inhibited growth.Acquired resistance was retained after five transfers on a fungicide-free medium. Pathogenicity of resistant isolates was not reduced, but their growth rates on PDA were significantly lower than those of the original isolates. Recovery of the resistant isolates was not improved on a selective medium amended with tolclofos-methyl.Samenvatting Na overenting op een medium dat tolchlofos-methyl bevatte, raakten enkele isolaten vanRhizoctonia solani gewend aan 500 maal de dosis die oorspronkelijk bijna alle groei verhinderde.Resistente isolaten vanR. solani bleven minder gevoelig voor tolchlofos-methyl na vijf overentingen op een medium zonder het fungicide. De pathogeniteit van resistente isolaten was niet verminderd, maar hun groeisnelheid op PDA was significant vertraagd vergeleken bij die van de oorspronkelijke isolaten. Isolatie van de resistente stammen werd niet verbeterd op een selectief medium waaraan tolchlofos-methyl was toegevoegd.     

Rhizoctonia foliar blight of Rosmarinus officinalis

Symptoms of severe leaf blight observed on rosemary ( Rosmarinus officinalis ) at Bangalore, India, were demonstrated to be caused by Rhizoctonia solani (anamorph of Thanatephorus cucumeris ). This is thought to be the first recorded incidence of this pathogen causing disease on rosemary.     

水稻纹枯病的发生流行与控制技术

水稻纹枯病自20世纪60年代在大冶地区流行以来，发病程度逐年加重，成为大冶水稻3大病害之首，对水稻生产构成严重威胁。近几年，通过试验研究，逐步形成了一套行之有效的综合防治方法，能有效地控制水稻纹枯病的发生与危害。     

水稻纹枯病防治药剂筛选试验研究

噻呋酰胺240k/L悬浮剂13mL/667m2、嘧茵酯250k/L悬浮剂40mL/667m2对水稻纹枯病病指防效分别为98.4％、97.0％,显著优于其它各药剂防效;丙环唑25％乳油45mL/667m2、己唑醇50％水分散粒剂l0g/667m2病指防效分别为88.1％、84.9％;井冈霉素5％水剂200mL/667m2、咪鲜胺25％乳油80mL/667m2防效最差,分别为44.4％、37.0％.因此,噻呋酰胺、嘧菌酯对水稻纹枯病具有良好的预防及治疗效果,且对水稻生长安全,水稻纹枯病重发年份首选使用;丙环唑、己唑醇是取代井冈霉素的优良药剂,生产上可加以推广.     

禾谷丝核菌(Rhizoctonia cerealis)原生质体制备与再生的研究

禾谷丝核菌(Rhizoctonia cerealis)是引起我国小麦纹枯病的主要致病菌。为了建立高效稳定的禾谷丝核菌遗传转化体系,本试验比较研究了不同细胞壁降解酶、酶液浓度、酶处理温度和时间等因素对禾谷丝核菌原生质体制备的影响,利用正交设计试验优化了原生质体再生条件。结果表明,液体培养6d的菌丝,采用15mg/mL溶壁酶+10mg/mL蜗牛酶组成的混合酶液,30℃下酶解4h,可以获得较高的原生质体释放量,可达到3.0×106个/mL;禾谷丝核菌原生质体再生的最佳条件是以SuTC缓冲液作为渗透压稳定剂悬浮原生质体,采用单层混菌法接种于TB3再生培养基,原生质体再生率可达到58.6%。禾谷丝核菌原生质体制备和原生质体再生条件的优化,为深入研究禾谷丝核菌生长发育的分子遗传学基础和进一步探索小麦纹枯病的致病机理奠定了基础。     

Sensitivity of Rhizoctonia species to different fungicides

Of 14 fungicides with different modes of action, cyproconazole and tolclofos-methyl were generally inhibitory both in vitro and in vivo against all tested isolates of five Rhizoctonia species belonging to the teleomorphs Thanatephorus cucumeris, Waitea circinata or Ceratobasidium cereale. Triadimenol and carboxin provided considerable variation in activity against different species and isolates, whereas prochloraz was ineffective against all isolates. Imazalil and fenarimol showed moderate control, whereas flusilazole, propiconazole, fenpropimorph and benomyl showed strong activity against R. zeae and R. oryzae, but were much less effective against R. sasakii, R. cerealis and R. solani. Benodanil and iprodione controlled all isolates of R. cerealis and R. solani, but were not very effective against R. zeae and R. oryzae. Pencycuron showed strong activity against R. sasakii and most R. solani isolates, moderate activity against R. zeae, and was ineffective against R. oryzae and R. cerealis.     

禾谷丝核菌在土壤中生长的研究

 1980年从小麦发病的茎秆上分离到病菌,并对小麦等多种植物进行了致病力测定。     

Nonpathogenic Binucleate Rhizoctonia spp. and Benzothiadiazole Protect Cotton Seedlings Against Rhizoctonia Damping-Off and Alternaria Leaf Spot in Cotton

ABSTRACT Recent reports have shown induction of resistance to Rhizoctonia root rot using nonpathogenic strains of binucleate Rhizoctonia spp. (np-BNR). This study evaluates the biocontrol ability of several np-BNR isolates against root and foliar diseases of cotton in greenhouse trials, provides evidence for induced systemic resistance (ISR) as a mechanism in this biocontrol, and compares the disease control provided by np-BNR with that provided by the chemical inducer benzothiadiazole (BTH). Pretreatment of cotton seedlings with np-BNR isolates provided good protection against pre- and post-emergence damping-off caused by a virulent strain of Rhizoctonia solani (AG-4). Seedling stand of protected cotton was significantly higher (P < 0.05) than that of nonprotected seedlings. Several np-BNR isolates significantly reduced disease severity. The combination of BTH and np-BNR provided significant protection against seedling rot and leaf spot in cotton; however, the degree of disease reduction was comparable to that obtained with np-BNR treatment alone. Significant reduction in leaf spot symptoms caused by Alternaria macrospora occurred on cotyledons pretreated with np-BNR or sprayed with BTH, and the np- BNR-treated seedlings had significantly less leaf spot than BTH-treated seedlings. The results demonstrate that np-BNR isolates can protect cotton from infections caused by both root and leaf pathogens and that disease control was superior to that observed with a chemical inducer.     

Evaluation of Brassica species for resistance to Rhizoctonia solani and binucleate Rhizoctonia (Ceratobasidum spp.) under controlled environment conditions

Isolates of R. solani AG 2–1, AG 8, AG 10 and binucleate Rhizoctonia (Ceratobasidium spp.) were tested for virulence on Brassica crops in growth chamber experiments. Isolate virulence and genotype resistance were determined based on percent of seedling survival, shoot length reduction, and shoot fresh weight. Isolates had significant effects on all tested measurements, compared to the non-inoculated controls. Rhizoctonia solani AG 2–1 appears to be the most aggressive pathogen on all tested genotypes followed by R. solani AG 8, binucleate Rhizoctonia and R. solani AG 10, respectively. Genotype by isolate interaction effects were found to be significant for percent of seedling survival and shoot length reduction. None of the tested genotypes exhibited any level of resistance to R. solani AG 2–1, but three promising genotypes with moderate levels of resistance to R. solani AG 10, R. solani AG 8 and binucleate Rhizoctonia were identified. Moderate heritability (0.57) was observed for the percent of seedling survival in the resistant genotype KS4022.