Assessing genetic diversity in the web blight pathogen <Emphasis Type="Italic">Thanatephorus cucumeris</Emphasis> (anamorph = <Emphasis Type="Italic">Rhizoctonia solani</Emphasis>) subgroups AG-1-IE and AG-1-IF with molecular markers

Web blight, an important foliar disease of dry beans in the Americas, is a challenge to manage. We studied genetic variation of 92 isolates of Rhizoctonia solani subgroups AG-1-IE and AG-1-IF using DNA fingerprinting methods and mycelial compatibility grouping. The isolates were collected over 13 years from bean fields in the Dominican Republic, Honduras and Puerto Rico. Cluster and AMOVA analysis of combined data from two universal rice primers and two internal sequence repeats revealed significant genetic variation among and within populations of both subgroups. Variation was influenced by geographic origin and sampling year for AG-1-IE isolates and geographic origin for AG-1-IF isolates. Mycelial compatibility of paired isolates was mostly scored as incompatible in both subgroups and supported many unique phenotypes. Only two isolates of AG-1-IE displayed mycelial compatibility and DNA fingerprints, suggesting clonal origin. Genetic variation in these AG-1-IE and AG-1-IF isolate populations may explain the lack of durable resistance to web blight reported in dry beans.     

Ganoderma boninense basidiospores in oil palm plantations: evaluation of their possible role in stem rots of Elaeis guineensis

Basidiospores are implicated in the distribution and genetic diversity of Ganoderma boninense, cause of basal stem rot (BSR) and upper stem rot (USR) of oil palm (Elaeis guineensis). Measurement of aerial basidiospores within plantations in Sumatra showed continuous and high production over 24 h (range c. 2–11 000 spores m^?3) with maximum release during early evening. Basidiospores applied to cut surfaces of fronds, peduncles and stems germinated in situ. Equivalent, extensive wounds are created during plantation harvesting and management and represent potential sites for formation of infective heterokaryons following mating of haploid basidiospore germlings. Use of spore‐sized micro‐beads showed that basidiospores could be pulled up to 10 cm into severed xylem vessels, where they are relatively protected from dehydration, UV irradiation and competing microflora. Diversity of isolates from five locations on two plantations was assessed by RAMS fingerprinting. Isolates from within individual palms with USR were identical and represent single infections, but different USR infections had unique band patterns and revealed separate infections. Some BSR‐affected trees contained more than one isolate, and thus had multiple infections. There was one example of adjacent BSR palms with the same isolate, indicating vegetative spread, but there were no identical genets from BSR infections and adjacent fallen palms. Isolate diversity was as great within a plantation as between plantations. It is evident that basidiospores play a major role in spread and genetic variability of G. boninense. Evidence for direct basidiospore infection via cut fronds, indirectly through roots via colonized debris and less frequently, infection by vegetative, clonal spread is considered.     

Characterization of Rhizoctonia solani Associated with Soybean in Brazil

Rhizoctonia solani causes pre- and post-emergence damping-off, root and hypocotyl rot and foliar blight in soybean. Foliar blight has resulted in yield losses of 31–60% in north and northeast Brazil. The aim of this study was to characterize isolates of R. solani associated with soybean in Brazil. Among 73 Rhizoctonia isolates examined, six were binucleate and 67 were multinucleate. The multinucleate iso1ates were characterized according to hyphal anastomosis reaction, mycelial growth rate, thiamine requirement, sclerotia production, and RAPD molecular markers. Four isolates that caused hypocotyl rot belonged to AG-4 and using RAPD analysis they grouped together with the HGI subgroup. Another isolate that caused root and hypocotyl rots was thiamine auxotrophic, grew at 35°C, and belonged to AG-2-2 IIIB. All 62 isolates that caused foliar blight belonged to AG-1 IA. RAPD analysis of R. solani AG-1 IA soybean isolates showed high genetic similarity to a tester strain of AG-1 IA, confirming their classification. The teleomorph of R. solani, Thanatephorus cucumeris was produced in vitro by one AG-1 IA isolate from soybean. The AG-4 and AG-2-2 IIIB isolates caused damping-off and root and hypocotyl rots of soybean seedlings cv. FT-Cristalina, under greenhouse conditions. The AG-2-2 IIIB isolate caused large lesions on the cortex tissue, that was distinct from the symptoms caused by AG-4 isolates. The AG-1 IA isolates caused foliar blight in adult soybean plants cv. Xingu under the greenhouse and also in a detached-leaf assay.     

First report of leaf sheath rot of Welsh onion caused by nine taxa of <Emphasis Type="Italic">Rhizoctonia</Emphasis> spp. and characteristics of the pathogens

From 2007 to 2013, a disease of Welsh onion, causing leaf sheath rot and concomitant death of outer leaves was found in 20 fields in Hokkaido, Japan. We obtained 20 Rhizoctonia isolates from diseased tissues and identified them based on the number of nuclei, hyphal fusion reactions, and molecular techniques using specific PCR primers and sequence of the rDNA-ITS region. The 20 isolates consisted of 16 multinucleate and four binucleate isolates. Of the multinucleate isolates, five were found to be so far unknown and designated here as Rhizoctonia solani AG-4 hybrid subgroup between HG-I and HG-II. Others were identified as AG-1 IB (three isolates), AG-2-2 IIIB (two isolates), AG-4 HG-I (two isolates), AG-1 IC (one isolate), AG-2-1 (one isolate), AG-4 HG-II (one isolate) and AG-5 (one isolate). All four binucleate isolates were binucleate Rhizoctonia AG-U. Original symptoms were reproduced on all plants inoculated with these isolates. Thus, we revealed that as many as nine taxa of Rhizoctonia spp. were associated with the disease. This is the first report of leaf sheath rot of Welsh onion caused by Rhizoctonia spp.     

Characterization of the Crater Disease Strain of Rhizoctonia solani

ABSTRACT Crater disease (CD) of wheat is caused by a Rhizoctonia solani strain of ambiguous phylogeny. Anastomosis reactions confirmed placement of CD-causing R. solani in anastomosis group (AG) 6, with results indicating a closer affinity to AG-6 GV than to AG-6 HG. Cultures of CD isolates were initially white to cream, turning a yellowish light brown after 10 days. Concentric rings of dark and light mycelium were evident from an early stage. Mycelium generally was appressed to the agar surface, with sparse aerial growth. A few light-colored, irregularly shaped sclerotia could be discerned after 2 weeks. The mean hyphal diameter of CD-causing R. solani was 7.46 mum (ranging from 5.0 to 10.0 mum), and cells contained a mean number of four (ranging from two to eight) nuclei, compared to a mean hyphal diameter of 8.58 and 8.42 mum and a mean nuclear number of six and four for AG-6 HG and AG-6 GV, respectively. The CD isolates had a slower growth rate (15.3 mm/day) than AG-6 HG (29.1 mm/day) and AG-6 GV (22.6 mm/day) but, like AG-6, were thiamine prototrophic. Conspicuous nodulose swellings were produced by CD-causing R. solani on roots of wheat, and infection resulted in retarded shoot growth. Smaller nodules were evident on bean and soybean roots. Fingerprint patterns generated for the various isolates with four enzymes, HpaII, Sau3AI, TaqI, and CfoI, showed the presence of a unique 610-bp fragment in the pathogen. It is proposed that CD-causing R. solani isolates represent a distinct intersterility group within AG-6 that is more related to subgroup GV than to subgroup HG.     

稻瘟病菌营养体亲和配对筛选及其亲和能力遗传

 在白米玫瑰红培养基上对江苏省的稻瘟病菌Magnaporthe grisea(Hebert) Barr.不同小种间营养体亲和菌株配对组合进行了筛选。当不同小种的菌株对峙接种,在21±1℃、黑暗中培养18 d后,部分配对组合的菌落交界处出现一条肉眼明显可见的菌丝融合带,且具有稳定的重复性。出现菌丝融合带的配对菌株在玻璃纸上对峙微培养2~3 d后,镜检观察到菌丝融合现象普遍存在;未出现明显菌丝融合带的菌株组合经对峙微培养,菌丝融合现象未见或较少。从ZA₄₉、ZG₁、ZF₁和ZD₁ 4个小种的12个菌株中筛选出3对营养体亲和性强的小种间菌株配对组合。以所选菌株为亲本建立单分生孢子无性系,测定营养体亲和能力在单孢后代的遗传。结果是,营养体亲和能力在单孢后代遗传不稳定,与另一亲本的单孢株配对产生融合带的百分率为53%~74%之间。进一步研究发现,来自同一个分生孢子不同细胞的单芽管株与配对菌株的营养体亲和能力相同;亲和能力在单芽管株的单孢株后代继续发生分离。     

Characterization of AG-13, a Newly Reported Anastomosis Group of Rhizoctonia solani

ABSTRACT Rhizoctonia solani anastomosis group (AG)-13 was collected from diseased roots of field grown cotton plants in Georgia in the United States. Isolates of AG-13 did not anastomose with tester isolates of AG-1 through AG-12. Mycelium of all isolates of AG-13 were light brown but darkened as cultures aged. All isolates produced aerial mycelium. Concentric rings were visible after 3 to 4 days of growth but disappeared as cultures aged and darkened. Individual sclerotia were up to 1.5 mm in diameter, similar in color to the mycelium, and generally embedded in the agar. Clumps of sclerotia up to 5 mm in diameter were produced on the agar surface. All attempts to induce basidiospore production were unsuccessful. The 5.8S region of the rDNA from isolates of AG-13 was identical in length and sequence to isolates of all other AGs of R. solani. Length and sequence of the internal transcribed spacer (ITS) regions of rDNA from isolates of AG-13 were unique among AGs of R. solani. Similarity between AG-13 and other AGs of R. solani ranged from 68 to 85% for ITS region 1 and 85 to 95% for ITS region 2. Selected isolates of AG-13 caused minor or no damage to barley, cauliflower, cotton, lettuce, potato, and radish in laboratory or greenhouse studies.     

华北地区十字花科芸薹属蔬菜上立枯丝核菌的病原生物学研究

 由丝核菌引起的十字花科蔬菜叶腐和茎基腐病在中国华北地区普遍发生,其中以河北、内蒙以及北京较为严重。2011~2018年,从华北地区不同省份具有典型叶腐和茎基腐症状的芸苔属蔬菜上分离获得95个丝核菌(Rhizoctonia spp.)分离物,大多数分离自发病植株的叶部,少数分离自茎基部。通过细胞核染色,87株菌属于多核丝核菌,另外8株属于双核丝核菌;经菌丝融合鉴定、rDNA-ITS区及TEF-1α(translation elongation factor 1-alpha, TEF-1α)序列分析,大多数多核丝核菌属于立枯丝核菌(Rhizoctonia solani)AG-2-1(74％),其他少数分别属于AG-1-IB(16％)、AG-4-HG II(2％)和双核丝核菌AG-A(8％)。温室条件下进行寄主范围致病力测定,各分离物对原寄主都表现出致病力,呈现典型叶腐或茎基腐症状;对其他作物的致病力差异较大。不同融合群(Anastomosis group,AG)的菌株对寄主致病力大小存在差异,AG-2-1致病力最强,只有AG-A对叶部没有致病力。AG-2-1对寄主叶部的致病力和对茎基部的致病力呈显著正相关,AG-1-IB对寄主叶部的致病力和对茎基部的致病力无显著相关性。     

Aetiology of Rhizoctonia in sheath blight of maize in Sichuan

Rhizoctonia isolates obtained from maize grown in commercial fields in 33 representative counties (or cities) in Sichuan province in China were characterized according to colony morphology, hyphal anastomosis and pathogenicity. Of 141 isolates, 116 were identified as R. solani , 23 as R. zeae and two as binucleate Rhizoctonia . The isolates of R. solani were assigned to four anastomosis groups (AG): AG-1-IA (101 isolates, accounting for 71.6% of the total), AG-1-IB (2, 1.4%), AG-4 (9, 6.4%) and AG-5 (4, 2.8%). The two isolates of binucleate Rhizoctonia belonged to AG-K. On maize, isolates of AG-1-IA caused typical sheath blight symptoms. Lesions produced by isolates of AG-4, AG-5, AG-1-IB and AG-K were darker than those of AG-1-IA. Rhizoctonia zeae usually caused discontinuous lesions with a dark brown margin and a brown centre on the leaf sheaths, as well as ear rot. Isolates of AG-1-IA were the most virulent to maize, with an average lesion length of approximately 15 cm. Isolates of R. zeae produced lesions approximately 12 cm long, while those of AG-4, AG-5, AG-1-IB and AG-K were progressively shorter. On potato dextrose agar (PDA; pH 6.4), the minimum temperature for mycelial growth of R. zeae isolates was 14–18°C, the maximum 38–40°C and optimum 30°C. Isolates of R. zeae did not grow on PDA (28°C) at pH 2.0, the optimum for growth being pH 6.4.     

华北地区十字花科芸薹属蔬菜上立枯丝核菌的病原生物学研究

 由丝核菌引起的十字花科蔬菜叶腐和茎基腐病在中国华北地区普遍发生,其中以河北、内蒙以及北京较为严重。2011~2018年,从华北地区不同省份具有典型叶腐和茎基腐症状的芸苔属蔬菜上分离获得95个丝核菌(Rhizoctonia spp.)分离物,大多数分离自发病植株的叶部,少数分离自茎基部。通过细胞核染色,87株菌属于多核丝核菌,另外8株属于双核丝核菌;经菌丝融合鉴定、rDNA-ITS区及TEF-1α(translation elongation factor 1-alpha, TEF-1α)序列分析,大多数多核丝核菌属于立枯丝核菌(Rhizoctonia solani)AG-2-1(74％),其他少数分别属于AG-1-IB(16％)、AG-4-HG II(2％)和双核丝核菌AG-A(8％)。温室条件下进行寄主范围致病力测定,各分离物对原寄主都表现出致病力,呈现典型叶腐或茎基腐症状;对其他作物的致病力差异较大。不同融合群(Anastomosis group,AG)的菌株对寄主致病力大小存在差异,AG-2-1致病力最强,只有AG-A对叶部没有致病力。AG-2-1对寄主叶部的致病力和对茎基部的致病力呈显著正相关,AG-1-IB对寄主叶部的致病力和对茎基部的致病力无显著相关性。     

Characterization of Pseudoperonospora cubensis isolates from Europe and Asia using ISSR and SRAP molecular markers

Downy mildew caused by Pseudoperonospora cubensis is a major disease of cucurbits worldwide. New genotypes of the pathogen have recently appeared in the USA, EU and Israel causing breakdown of genetic resistance, expansion of host range, and the appearance of a new A2 mating type. Seventy-eight P. cubensis isolates were collected during 1996–2011 from cucurbits fields in different regions of Turkey, Israel and the Czech Republic and genetic diversity was analysed using highly polymorphic ISSR and SRAP molecular markers. The data acquired showed remarkable genetic diversity within and among the isolates. While isolates from Turkey and Czech Republic exhibited uniform genetic background, the isolates from Israel were clearly distinguished from the others. The results may indicate on migration and/or frequent sexual reproduction of the pathogen in Israel. Moreover the selected markers can be suggested for monitoring genetic diversity within P. cubensis isolates in further studies.     

利用UP-PCR、ISSR和AFLP标记分析玉米丝黑穗病菌遗传多样性

利用UP-PCR、ISSR和AFLP分子标记方法研究了我国主要玉米产区34株玉米丝黑穗病菌的遗传多样性。从供试引物中筛选获得具多态性的UP-PCR引物9个、ISSR引物11个和AFLP引物组合22对,分别扩增出113、72和293条谱带,多态性条带比率分别为91.15%、84.7%和83.27%。聚类分析表明,玉米丝黑穗病菌存在丰富的遗传变异,与地理来源无明显相关性。3种分子标记的遗传相似系数矩阵相关性分析表明,UP-PCR与AFLP具有较高的相关性,相关系数为0.698;UP-PCR与ISSR、ISSR与AFLP的相关系数分别为0.659和0.633。从多态性水平、稳定性和可操作性可以看出,UP-PCR技术更适于分析玉米丝黑穗病菌遗传多样性。此外,UP-PCR、ISSR和AFLP标记划分的类群与鉴别寄主划分的致病类型之间存在一定的相关性,吻合率分别为50.0%、60.0%和47.6%。     

Characterization of a New Subgroup of Rhizoctonia solani Anastomosis Group 1 (AG-1-ID), Causal Agent of a Necrotic Leaf Spot on Coffee

ABSTRACT A new foliar disease on coffee leaves was observed in Mindanao, Philippines, in 1996. The symptoms appeared as large circular or irregularly shaped necrotic areas with small circular necrotic spots (1 mm or less in diameter) usually found around the periphery of the large necrotic areas. Rhizoctonia solani was consistently isolated from these diseased coffee leaves. Isolates obtained were multinucleate (3 to 12 nuclei per hyphal cell), had an optimum temperature for hyphal growth at 25 degrees C, prototrophic for thiamine, and anastomosed with tester isolates belonging to R. solani anastomosis group 1 (AG-1). Mature cultures on potato dextrose agar (PDA) were light to dark brown. Sclerotia, light brown to brown, were formed on the surface of PDA and covered the whole mature colony culture. Individual sclerotia often aggregated into large clumps (3 to 8 mm in diameter) and their color was brown to dark brown. In pathogenicity tests, isolates from coffee caused necrotic symptoms on coffee leaves, whereas isolates of AG-1-IA (not isolated from coffee), 1-IB, and 1-IC did not. The results of analyses of restriction fragment length polymorphism of ribosomal DNA internal transcribed spacer, random amplified polymorphism DNA, and fatty acid profiles showed that R. solani isolates from coffee are a population of AG-1 different from AG-1-IA, 1-IB, and 1-IC. These results suggest that R. solani isolates from coffee represent a new subgroup distinct from AG-1-IA, 1-IB, and 1-IC. A new subgroup ID (AG-1-ID) is proposed.     

Analysis of population structure of Rosellinia necatrix on Cyperus esculentus by mycelial compatibility and inter-simple sequence repeats (ISSR)

Genetic diversity was studied in a population of 24 isolates of Rosellinia necatrix obtained from Cyperus esculentus and 16 from other hosts by means of mycelial compatibility groups (MCGs) and inter-simple sequence repeat (ISSR) techniques. All isolates obtained from C. esculentus belonged to a unique MCG, irrespective of their geographical origin or year of isolation, and were incompatible with the isolates from other hosts. ISSR analysis gave results which were in agreement with the MCG determination; selected ISSR primers grouped a subset of eight representative isolates from C. esculentus in a unique cluster. The homogeneity found within the population of R. necatrix from C. esculentus in Valencia province could suggest that the pathogen was introduced recently and has spread further via infected tubers inadvertently used as propagating material, as well as by cull tubers swept away by irrigation water.     

The first report of tomato foot rot caused by <Emphasis Type="Italic">Rhizoctonia solani</Emphasis> AG-3 PT and AG-2-Nt and its host range and molecular characterization

Foot rot of mature tomato plants was found in four cities of Hokkaido, Japan, from 2004 to 2007. Six of eight isolates obtained from damaged tissues were identified as Rhizoctonia solani anastomosis group (AG)-3, and the remaining two isolates belonged to AG-2-1. We compared these isolates with nine reference isolates including the different subgroups in AG-3 (PT, TB and TM) and AG-2-Nt (pathogen of tobacco leaf spot) within AG-2-1 in terms of pathogenicity to tomato, tobacco and potato. All eight isolates caused foot rot on tomato. The six AG-3 isolates caused stem rot on young potato plants. While, all reference isolates of AG-3 PT causing stem rot of young potato plants incited foot rot on tomato. The two AG-2-1 isolates and an AG-2-Nt reference isolate caused severe leaf spot on tobacco leaves. The sequences of rDNA- ITS region and rDNA-IGS1 region of the AG-3 isolates showed high similarity to that of AG-3 PT isolates. Phylogenetic tree based on ITS and IGS1 regions of rDNA indicated that the AG-2-1 isolates from tomato formed a single clade with AG-2-Nt isolates and that they were separate from Japanese AG-2-1 isolates (culture type II). Pathogenicity tests and DNA sequence evaluation of the causal fungi revealed that the present isolates of AG-3 and AG-2-1 belonged to AG-3 PT and AG-2-Nt, respectively. This is the first report of tomato foot rot caused by R. solani in Japan.     

新疆北疆棉田立枯丝核菌不同菌丝融合群致病力的研究

从新疆北疆棉区采集了典型的棉花立枯病病苗及棉田土标样686份,按常规分离方法分离得到399个分离物,从中鉴定出272个纯化的立枯丝核菌(Rhizoctonia solani Kühn)菌株。用标准菌株,通过载玻片菌丝融合试验测定,将纯化的272个菌株划归为3个菌丝融合群:即AG-2、AG-4和AG-5,分别占总菌株的6.24%、84.2%和1.1%。另有23个菌株不与任何标准菌株融合,占8.46%,说明新疆北疆棉田立枯丝核菌的优势菌系是多核丝核菌的AG-4融合群。通过从10种不同配方培养基中筛选效果好的麦芽蛋白胨(MPDA)配方培养基(Ⅱ)进行对峙培养,将纯化获得的272个丝核菌菌株,划分为6个不同的营养亲和群。将多核的不同菌丝融合群及其各营养亲和群代表菌株在3种不同主栽棉花品种上(每品种都加不接菌的对照)进行温室盆栽致病力测定,结果以AG-4对棉花的致病力最强,其次是非融合类,AG-2和AG-5虽致病,但并不致死苗,其平均病指数分别为94.9、81.4、53.1、43.5。     

陕西省苹果树腐烂病菌基因多态性的ISSR分析

为了从分子水平上揭示苹果树腐烂病菌的群体遗传多样性,采用正交设计对ISSR-PCR体系进行了4因素3水平的筛选,并从47条ISSR引物中筛选出11条多态性较好的引物。对供试的87个分离株进行扩增的结果显示,11条引物在129个位点扩增出稳定的条带,其中多态性位点119个,多态性位点率为92.25%。POPGENE分析显示,病菌种群的遗传多样性和基因多态性丰富,群体间的遗传分化系数(Gst)为0.109,群体内为0.891,群体内多样性大于群体间多样性。两个地理种群间的居群每代迁移数(Nm)为2.046,两者之间存在广泛的基因交流。在遗传相似系数为0.88时,可将21个自然种群划分为9个不同的类群,表明陕西省苹果树腐烂病菌的各个自然种群之间的遗传亲缘关系与其地理来源之间无明显的相关性。     

Rhizoctonia species and anastomosis groups isolated from barley and wheat in Erzurum, Turkey

Ninety-eight isolates of Rhizoctonia spp. were obtained from barley and wheat grown in Erzurum, Turkey. Of these, 78% were Rhizoctonia solani (AG-2 type 1, AG-3, AG-4, AG-5 and AG-11), 10% were binucleate Rhizoctonia (AG-I and AG-K) and the remainder were Waitea circinata var circinata ( Rhizoctonia sp.). Among the binucleate Rhizoctonia , AG-I was not recovered from barley. In pathogenicity tests on barley and wheat, the highest disease severity was caused by isolates of AG-4 and AG-11, whereas isolates of AG-2 type 1, AG-3, AG-5 and W. c . var  circinata were moderately virulent. Isolates of binucleate Rhizoctonia were all nonpathogenic. This is the first report of R. solani AG-11 and W. c . var  circinata from Turkey.     

Characterization of Mycorrhizal Isolates of Rhizoctonia solani from an Orchid, Including AG-12, a New Anastomosis Group

ABSTRACT Isolates of Rhizoctonia solani collected from mycorrhizal orchid (Pterostylis acuminata) plants and adjacent leaf litter were characterized. Of 23 selected isolates, 20 were members of a new anastomosis group (AG-12) and the rest were members of AG-6. There were no bridging anastomosis reactions observed between AG-12 and other AGs of R. solani. Among the 20 isolates of AG-12 evaluated, 18 vegetatively compatible populations were detected, indicating diversity within the AG. Mature cultures were dark brown, as were mature sclerotia. Some cultures produced alternating dark- and light-colored concentric rings, with sclerotia forming in the darker rings. Most cultures were appressed to the agar surface. In tests run to characterize pathogenic potential, selected mycorrhizal isolates of AG-12 and AG-6 did little damage to potato and barley seedlings, moderate damage to head lettuce seedlings, and more extensive damage to seedlings of cauliflower and radish. Isolates of AG-12 have not been observed to fruit in nature, and all attempts to induce formation of the teleomorph (Thanatephorus cucumeris) in the laboratory by selected isolates of AG-12 failed.     

Characterization ofRhizoctonia solani isolates from potatoes in turkey and screening potato cultivars for resistance to AG-3 isolates

A total of 304Rhizoctonia solani isolates and 60 binucleateRhizoctonia-like fungi were recovered from stems and tubers of infected potato plants over a 2-yr period in northeast Turkey.R. solani isolates were identified to 11 anastomosis groups (AGs): AG-1 (0.66%), AG-2-1 (5.6%), AG-2-2 (0.99%), AG-3 (83.9%), AG-5 (4.6%), AG-6 (0.66%), AG-8 (1.32%), AG-9 (0.33%), AG-10 (1.32%), AG-12 (0.33%), and AG-13 (0.33%). In the greenhouse tests, most of the AG-3 isolates were significantly more virulent than isolates belonging to other AGs on potato cv. Batum. Isolates of other anastomosis groups differed in their virulence. Results indicated that AG-3 is an important pathogen on potatoes grown in the study area. Five of 22 commercial and local potato cultivars evaluated for their reaction toR. solani AG-3 isolates (TP-2) under greenhouse conditions were highly resistant; the remaining cultivars exhibited different levels of susceptibility to the pathogen isolate. http://www.phytoparasitica.org posting July 14, 2005.