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1.
为明确中国东北地区水稻纹枯病病原菌种类及融合群的归属情况, 2015－2017年从黑龙江省、吉林省和辽宁省的17个水稻主产区采集水稻纹枯病标样, 分离获得水稻纹枯病菌214株, 运用水稻纹枯病菌的不同病原菌及融合群的特异性引物对214株水稻纹枯病菌进行病原菌种类和融合群鉴定, 并利用rDNA内转录间隔区(ITS)序列, 对供试水稻丝核菌的融合群归属进行了分析。结果表明:供试214株水稻纹枯病菌分属于茄丝核菌Rhizoctonia solani和水稻丝核菌Rhizoctonia oryzae-sativae, 菌株数分别为198株和16株, 占比分别为92.52%和7.48%。茄丝核菌菌株分属于2个融合群, 分别为AG1-IA和AG4, 菌株数分别为191株和7株, 占比分别为96.46%和3.54%。水稻丝核菌菌株均属于AG-Bb融合群, 菌株数为16株。不同年份水稻纹枯病的病原菌种类及融合群出现的频率和地域分布无明显变化, 而不同地域间水稻纹枯病病原菌的种类及融合群具有明显的分化特征, AG1-IA融合群在中国东北三省各个水稻产区均有分布且均为优势融合群, AG4融合群在辽宁省盘锦市出现频率最高, 水稻丝核菌AG-Bb融合群在吉林省吉林市、通化市和梅河口市出现频率最高。  相似文献   

2.
Methods based on internal transcribed spacers (ITS) ribosomal DNA (rDNA) polymorphism and pectic zymograms (ZG) were compared for their use in routine identification of Rhizoctonia solani isolates occurring in flower bulb fields. Thirty three AG 2-t isolates, pathogenic to tulips, could be distinguished from AG 1-IC, AG 2-2IIIB and AG 2-2IV, AG 3 and AG 5 by means of ITS rDNA fragment length and after digestion with EcoR I from AG 4 and AG 5. AG 2-t isolates and two Japanese isolates, pathogenic to crucifers and tulips, had an estimated fragment size of 710 bp, whereas Dutch AG 2-1 isolates, non-pathogenic to tulips, showed an estimated fragment size of 705 bp on agarose gel. Digestion of AG 2-t and AG 2-1 isolates with EcoR I, Sau3A I, Hae III and Hinc II revealed four and five distinct ITS rDNA digestion patterns, respectively. In AG 2 isolates 2tR114, 21R14 and 21R61 a double digestion pattern, indicating different ITS sequences within an isolate, was found. The observed ITS fragment length polymorphism between isolates pathogenic and non-pathogenic to tulips were considered too small to be used in routine screening of field isolates. Sequencing of AG 2 isolates 21R01, 21R06, 2tR002 and 2tR144 showed a total ITS rDNA fragment length of 715, 713, 714, and 728 bp. As an alternative to ITS rDNA fragment length polymorphism, pectic enzyme patterns were studied using a commercially available vertical gel-electrophoresis system and non-denaturing polyacrylamide gels amended with pectin. Anastomosis tester isolates AG 1 to AG 11 revealed different ZG. Fifty AG 2-t isolates and five AG 2-1 isolates belonged to a homogeneous pectic zymogram group. We propose to assign AG 2 isolates pathogenic to crucifers and tulip to ZG5-1. AG 2-1 isolates, non-pathogenic to tulip, formed a heterogeneous group with 4 distinct ZG. Pectic zymography provides an easy, quick and unambiguous method for routine identification of large numbers of field isolates. Such a technique is needed for research on the dynamics of Rhizoctonia populations to develop environmentally friendly control measures of rhizoctonia disease in field-grown flower bulbs.  相似文献   

3.
Rhizoctonia -diseased specimens were collected from various host species growing in or near maize fields in different geographic regions of the Philippines. A greater range of host species, with varying types of disease symptoms, was found in Mindanao than in Luzon. Fifty-two isolates belonged to anastomosis group AG1-IA and caused banded leaf and sheath blight in maize ( Zea mays ), but they showed considerable variation in virulence. The most and least virulent isolates recovered from maize were both collected from Mindanao. Isolates from necrotic spots/foliar blight of durian and coffee, which were collected from the same region, showed the lowest lesion heights. UPGMA-SAHN clustering analysis from RAPD fingerprint data of 30 haplotypes of R. solani AG1-IA isolates from the Philippines and Japan resolved seven groups of AG1-IA at the 75% similarity level. Variation among isolates from upland crops seemed to be partially correlated with geographical origin and virulence. In the case of paddy rice isolates from Japan and the Philippines, some were closely related, with over 75% similarity, suggesting a common origin. In PCR-RFLP analysis of the rDNA internal transcribed spacer region, no polymorphism was observed among the AG1-IA isolates but they were differentiated from subgroups AG1-IB and AG1-IC using the endonucleases Eco RI, Mbo I and Hin fI.  相似文献   

4.
Two-hundred and forty-eight isolates of Rhizoctonia spp, were obtained from 13 locations in Gifu Prefecture in Japan using the plant debris particles isolation, colonization of bait tissue, and soil-clump plating methods. Of the isolates, 143 were binucleate Rhizoctonia spp., 60 were R. solani and 45 were R. zeae. Three isolates of R. solani and 54 of binucleate Rhizoctonia spp, were hypovirulent on radish, whilst all isolates of R. zeae were highly virulent, Hypovirulent strains were isolated most frequently by the plant debris particles isolation method, Hypovirulent isolates of R. solani belonged to anastomosis group 4, whilst the hypovirulent binucleate Rhizoctonia isolates belonged to AG A, AG Ba, AG G, and AG O.
Thirty-two isolates of Rhizoctotria spp, selected for hypovirulence on radish were tested on cucumber in vitro. Only five binucleate Rhizoctonia isolates and one R. solani isolate were hypovirulent on both species, and these isolates were also hypovirulent on seven other crop species. Cucumber showed wide variation in disease susceptibility to different isolates but hypovirulent isolates exhibited a consistent reaction on five different host cultivars, Pathogenicity tests using cucumber grown in soil also showed consistent reactions with isolates selected either for hypovirulence or virulence. The results support the use of cucumber in bioassays for identifying hypovirulent isolates of binucleate Rhizoctonia spp.  相似文献   

5.
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.  相似文献   

6.
The rDNA-ITS sequence of Rhizoctonia solani AG 1-ID was determined and compared to those of R. solani AG 1-IA, AG 1-IB, and AG 1-IC. The similarity of the isolates from each AG 1 subgroup was almost identical (99%–100%), whereas it was lower between subgroups (91%–95%) than within subgroups. Phylogenetic analysis indicated that isolates of AG 1-ID and other subgroups were separately clustered. Isolates of R. solani AG 1 were clearly separated from R. solani AG 2-1, AG 4, and binucleate Rhizoctonia AG-Bb and AG-K. These results showed that analysis of the rDNA-ITS sequence is an optimal criterion for differentiating R. solani AG 1-ID from other subgroups of R. solani AG 1.  相似文献   

7.
Mazzola M 《Phytopathology》1997,87(6):582-587
ABSTRACT Rhizoctonia spp. were isolated from the roots of apple trees and associated soil collected in orchards located near Moxee, Quincy, East Wenatchee, and Wenatchee, WA. The anastomosis groups (AGs) of Rhizoctonia spp. isolated from apple were determined by hyphal anastomosis with tester strains on 2% water agar and, where warranted, sequence analysis of the rDNA internal transcribed spacer region and restriction analysis of an amplified fragment from the 28S ribosomal RNA gene were used to corroborate these identifications. The dominant AG of R. solani isolated from the Moxee and East Wenatchee orchards were AG 5 and AG 6, respectively. Binucleate Rhizoctonia spp. were recovered from apple roots at three of four orchards surveyed and included isolates of AG-A, -G, -I, -J, and -Q. In artificial inoculations, isolates of R. solani AG 5 and AG 6 caused extensive root rot and death of 2- to 20-week-old apple transplants, providing evidence that isolates of R. solani AG 6 can be highly virulent and do not merely exist as saprophytes. The effect of binucleate Rhizoctonia spp. on growth of apple seedlings was isolate-dependent and ranged from growth enhancement to severe root rot. R. solani AG 5 and AG 6 were isolated from stunted trees, but not healthy trees, in an orchard near Moxee, WA, that exhibited severe symptoms of apple replant disease, suggesting that R. solani may have a role in this disease complex.  相似文献   

8.
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.  相似文献   

9.
Characterization of Rhizoctonia solani from potato in Great Britain   总被引：1，自引：1，他引：1  
One hundred and thirty five isolates of Rhizoctonia solani were obtained from British potato crops between 2001 and 2003. Isolates were assigned to anastomosis group (AG) using conventional PCR assays for AG2-1 or AG3 or through the observation of hyphal interactions, where appropriate. A previously published primer set was modified in this study to enhance specificity for AG3PT. Most of the isolates (92·6%) belonged to AG3PT whilst some (6·7%) belonged to AG2-1. Only one isolate recovered (0·7%) belonged to AG5. Isolates of AG2-1 were diverse, with variation in both the length of the rDNA intergenic spacer 1 (IGS1) region and the categories of hyphal interaction observed between pairings of AG2-1 isolates. No variation in the length of the rDNA IGS1 region was observed amongst the AG3 isolates collected. Tests carried out on potato stems with a sub-set of the isolates revealed a wide range of aggressiveness amongst AG2-1 isolates. Sequencing of the rDNA internal transcribed spacer (ITS) region of the AG2-1 isolates and construction of a neighbour joining tree with other AG2-1 sequences available indicated that AG2-1 isolates with the short IGS1 region were closely related. This is the first investigation which provides evidence of the relative AG composition of R. solani populations causing disease in potato crops in Great Britain.  相似文献   

10.
Sheath blight, caused by Rhizoctonia solani AG1‐IA, is one of the most serious diseases of rice. In this study, a total of 175 isolates of R. solani AG1‐IA were collected from five rice‐growing regions in China. Pathogenicity tests revealed that all isolates were virulent to five cultivars with different levels of resistance at the rice seedling stage in the greenhouse. There was considerable variation in aggressiveness, and the isolates were classified into three pathotypes based on disease severity, with moderately virulent isolates prevalent in the population. Forty‐three haplotypes were identified based on ITS sequencing, and 39 haplotypes were distinct among isolates. There were high levels of haplotype diversity and nucleotide diversity within the populations of R. solani AG1‐IA. High gene flow (Nm = 1·63–5·22) was detected, consistent with relatively low differentiation between pairs of populations. Five populations were divided into two distinct clusters by the unweighted pair group method with arithmetic mean (UPGMA), and no spatial population differentiation was discernible. The majority (97·8%) of genetic diversity was distributed among isolates within populations, with only 2·2% of the genetic diversity attributed to differences among populations. The star‐like shape of the haplotype network provided evidence of signatures of population expansion in recent history. No significant relationships were found between the genetic diversity and aggressiveness or geographic origin among populations of R. solani AG1‐IA. These results highlight that the population characteristics of R. solani AG1‐IA should be taken into account in evaluating the germplasm resistance of rice cultivars to sheath blight.  相似文献   

11.
Sixty-two isolates of Rhizoctonia spp. were collected from Belgian cauliflower fields during 2005 and 2006. The majority of the isolates (60 out of 62) had multinucleate cells and were identified as Rhizoctonia solani . Characterization of anastomosis groups (AGs) was performed using pectic zymograms, PCR-RFLP and sequencing of the rDNA-ITS region. The most prevalent AG was AG 2-1 (55% of isolates), followed by AG 2-1 subset Nt (11%), AG 1-1C (8%), AG 5 (8%), AG 4 HGII (6%), AG 3 (5%) and AG 1-1B (3%). Pathogenic potential towards different vegetable crops and towards maize was determined. Damage to cauliflower and endive was caused by different AGs, with the isolates aggressive towards cauliflower belonging to AG 2-1, AG 2-1 subset Nt, AG 4 HGII, AG 1-1C, AG 1-1B and AG 2-2, and those aggressive towards endive belonging to AG 1-1B, AG 1-1C, AG 2-1 subset Nt, AG 2-2, AG 4 HGII and AG 5. The most aggressive isolates towards bean belonged to AG 2-1 subset Nt and AG 2-2, for lettuce to AG 1-1B and AG 2-1, on carrot to AG 4 HGII and towards maize to AG 2-2. Within the isolates of AG 2-1, variability was observed in PCR-RFLP pattern and in aggressiveness towards several crops, indicating this subgroup to be heterogeneous. This is the first study concerning the occurrence of R. solani AGs causing wirestem in Belgian cauliflower fields and the first report of aggressive isolates of AG 1-1C, AG 2-1 subset Nt and AG 4 HGII associated with cauliflower.  相似文献   

12.
由立枯丝核菌引起的马铃薯黑痣病是一种常见的土壤和种薯传播病害,在世界各地均有发生。本试验对分离纯化的67个丝核菌菌株进行融合群测定,结果表明:67个菌株都属于AG3融合群;对其中来自6个不同地域的11个菌株进行ITS测定,11个菌株的相似度为99%。8种药剂对马铃薯黑痣病菌的毒力测定结果表明,20%氟胺·嘧菌酯水分散粒剂50mg/L和25g/L咯菌腈悬浮种衣剂50mg/L的抑菌效果较好,室内抑菌效果可达100%。  相似文献   

13.
ABSTRACT A murine hybridoma cell line GD2 secreting an immunoglobulin (Ig)M monoclonal antibody (MAb) was produced against surface antigens from an anastomosis group (AG) 4 isolate of Rhizoctonia solani (teleomorph: Thanatephorus cucumeris). Ascites were produced in mice using GD2 hybridoma cells and used to develop a rapid immunochromatographic lateral flow device (LFD) for the detection of antigens from R. solani and certain related Rhizoctonia spp. The LFD was tested for specificity against surface antigens from related and unrelated soil fungi. Antigens from representative isolates of R. solani AGs 1, 2-1, 2-3, 2-t, 3, 4, 5, 6, 7, 8, 9, 10, 11, and BI gave a positive response in LFD tests, as did antigens from Thanatephorus orchidicola, T. praticola, R. fragariae (teleomorph: Ceratorhiza fragariae), Ceratorhiza goodyerae-repentis, Ceratobasidium cornigerum, and binucleate AGE. Antigens from R. solani AGs 2-2, 2-2IIIB, and 2-2IV and from the related fungi R. carotae, R. cerealis (teleomorph: Ceratobasium cereale), R. crocorum (teleomorph: Helicobasidium brebissonii), R. oryzae (teleomorph Waitea circinata), and R. zeae gave negative responses, as did antigens from a range of unrelated fungi and oomycetes including Fusarium, Gliocladium, Trichoderma, Pythium, and Phytophthora spp. The usefulness of the LFD to detect R. solani was demonstrated in soils naturally infested with R. solani AG3. There was close agreement between results of LFD tests and conventional plate enrichment tests employing selective medium. The specificity of the technique was confirmed by polymerase chain reaction PCR using R. solani AG3-specific primers and by analyses based on sequences of the internal transcribed spacer (ITS)1-5.8S-ITS2 rRNA-encoding regions of unrelated fungi recovered from soil samples. The LFD was used to quantify R. solani AG4 in artificially infested soil samples (chopped potato soil inoculum). Estimates of CFU per gram of soil were derived using a most-probable number technique, which was based on the presence or absence of a detectable signal in the LFD. Estimates of CFU obtained in LFD tests and those obtained in a plate-trapped antigen enzyme-linked immunosorbent assay incorporating MAb GD2 were identical (449 CFU g(-1) of soil).  相似文献   

14.
Isolates of Rhizoctonia solani AG2-2 obtained from turf with symptoms of large-patch disease of warm-season turfgrasses were compared with known AG2-2 isolates belonging to cultural types IIIB and IV. Some isolates that were previously identified as type IV have been separated here and named LP isolates. Comparisons among isolates were based on cultural morphology, hyphal growth rate, pathogenicity and restriction fragment length polymorphism (RFLP) analysis in the nuclear encoded ribosomal DNA (rDNA) genes. The cultural characteristics of LP isolates varied from those of types IIIB and IV. LP isolates did not show distinct sclerotial formation and zonation, and the colour of their mycelia and pigment deposition was dark brown. LP isolates had slower hyphal growth rates than types IIIB and IV, with an optimum temperature of 25°C compared with 28°C for types IIIB and IV. LP isolates were less virulent on radish but highly virulent on zoysia grass when compared with isolates of types IIIB and IV. Genomic DNA was digested separately with Eco RI, Ban III, Xba I and Sal I, and probed with cloned rDNA from Alternaria alternata in Southern hybridizations. LP isolates had one RFLP pattern, while both IIIB and IV possessed four different patterns each. Cluster analysis of RFLPs showed that R. solani AG2-2 is divided into three genetic subgroups, consisting of the IIIB, IV and LP isolates, respectively. The polymerase chain reaction (PCR) amplified rDNA internally transcribed spacer (ITS) regions of the IIIB, IV and LP isolates had the same length but produced different restriction patterns when digested with Msp I and Taq I. These results indicate that there are three cultural types in R. solani AG2-2, namely IIIB, IV and LP.  相似文献   

15.
Cellular fatty acids were analyzed to characterize and differentiate 34 isolates of Rhizoctonia species representing binucleate Rhizoctonia AG-D (I), AG-D (II), R. solani AG 2-2 IIIB, AG 2-2 LP, R. circinata var. circinata and var. oryzae associated with turfgrass diseases in Japan. Myristic, pentadecanoic, palmitic, palmitoleic, stearic, oleic, linoleic and linolenic acids were consistently present in varying quantities in all isolates. Heptadecanoic and 9-heptadecenoic acids were present in isolates of Rhizoctonia AG-D (I), AG-D (II), R. solani AG 2-2 IIIB and AG 2-2 LP but not in isolates of R. circinata var. circinata and var. oryzae. Palmitic, oleic and linoleic acids were the major fatty acids found, constituting 88.30-98.37% of the whole-cell fatty acid content. The remaining fatty acids were present in smaller amounts. Isolates within a single group were closely clustered, whereas isolates from different groups were clearly distinguishable based on average linkage cluster analysis of cellular fatty acids. Principal component analysis, based on all fatty acids detected, confirmed the distinct separation of isolates representing the six groups of Rhizoctonia species obtained from turfgrasses. These results suggested that fatty acid analysis is useful for the characterization and differentiation of isolates of Rhizoctonia species associated with turfgrass diseases. Received 21 May 2001/ Accepted in revised form 28 September 2001  相似文献   

16.
小麦纹枯病菌核糖体基因内转录区序列比较   总被引：13，自引：1，他引：12  
 对7个从江苏省小麦纹枯病样本分离到的丝核菌菌株,进行形态学鉴定、融合群分类和致病性测定,提取病菌的DNA,采用通用引物ITS1(TCC GTA GGT GAA CCT GCG G)和ITS4(TCC TCC GCT TAT TGA TAT GC),扩增病菌的rDNA内转录区(ITS),并对扩增产物进行了测序.用这些序列在NCBI中进行BLAST分析,得到与这些菌株亲缘关系最近的菌株序列,并明确了这些菌株的分类地位.对以上的菌株序列进行Alignment分析,结果表明,病菌的5.8S rDNA序列高度保守,而ITS区的可变性则相对较高,在双核和多核丝核菌、双核丝核菌CAG1融合群和非CAG1融合群菌株间存在差异,可用于反映菌株间的进化关系和双核丝核菌种下分类.  相似文献   

17.
绿豆立枯丝核菌研究初报   总被引：1，自引：0，他引：1  
本研究通过形态学、菌丝融合群和致病力测定研究,对从河北省石家庄地区绿豆种植区分离的90个立枯丝核菌进行鉴定。在90个分离物中有71个属于AG4,占供试分离物的78.89%,2个属于AG2-2,占供试分离物的2.22%,另外17个分离物与标准菌株不融合,占供试分离物的18.89%;属于AG4的71个分离物中,55个与AG4完全融合（占77.46%）,16个与AG4不完全融合（占22.54%）。在温室条件下采用人工接菌法对40个代表性分离物的致病力进行测定,发现不同分离物对同一品种的致病力存在差异,其中分离物R3、R6、R9、R35致病力最强,分离物R23、R31-1致病力最弱。属于AG 4的分离物R3、R6、R9、R35与其他供试分离物致病力差异极显著;属于未知群体的分离物R20、R29和R24之间致病力差异极显著;属于AG2-2的分离物R21、R31-1致病力较弱,且差异不显著。  相似文献   

18.
黑龙江省水稻纹枯病菌的致病力分化与AFLP分析   总被引：3，自引：0，他引：3  
为了明确黑龙江省水稻纹枯病菌遗传多样性,为水稻抗病育种和水稻纹枯病的综合防治提供依据。本文对采自13个水稻种植地区的29个水稻纹枯病菌菌株进行了致病力测定和AFLP分析。结果表明9对AFLP引物对供试菌株扩增出396条带,其中多态性带187条,占总扩增带数的47.22%。黑龙江省水稻纹枯病菌的遗传距离变化在0.50~0.92之间,平均为0.71,群体遗传多样性较为丰富。UPGMA法可以将供试菌株分成4个AFLP聚类组群(Ⅰ、Ⅱ、Ⅲ和Ⅳ),相同地理来源的菌株基本上聚集在同一组群内,表明AFLP类群划分与菌株的地理来源有较强的相关性。黑龙江省水稻纹枯病菌致病性分化较为明显,并且AFLP类群划分与菌株的致病性鉴定之间存在一定相关性。  相似文献   

19.
杨金红 《植物保护》2009,35(6):83-86
从新疆11种豆科作物病株上或病株根围土样中分离纯化出250个立枯丝核菌（Rhizoctonia DC）,番红O KOH染色后观察细胞核数目,经测试全部菌株均为多核,用标准菌株测定融合群, 250个菌株分属为AG 1、AG 2、AG 3、AG 4和AG 5共5个融合群,出现频率分别为16.4%、33.2%、0.4%、32.4%和17.6%,营养亲合群判别结果表明,AG 1、AG 2、AG 4和AG 5下各有2个VCG,说明新疆豆科作物立枯丝核菌各主要菌丝融合群内均有不同程度的分化。  相似文献   

20.
Bottom rot caused by Rhizoctonia solani is an increasing problem in field-grown lettuce in Germany. During the growing seasons of 1999 and 2000, 95 isolates of R. solani from lettuce plants with bottom rot symptoms were collected from eight locations. The isolates were characterised using hyphal anastomosis, pectic zymograms and morphological characteristics. Ninety-three isolates were identified as anastomosis group (AG) 1-IB, one as AG 1-IC and one as AG 2-1. Optimum hyphal growth was measured over a temperature range of 20–30 °C with an optimum at 25 °C. Aggressiveness of the AG 1-IB isolates varied from weak to strong when tested on detached lettuce leaves. The pathogenic potential of six AG 1-IB isolates was determined on 14 plant species in comparison with lettuce under conditions favourable for the fungus. Radish, broccoli, kohlrabi, spinach and millet seedlings were as severely infected as lettuce seedlings. The same isolates caused little symptoms on maize, tomato and onion. Knowledge about the host range of AGs of R. solani are important for planning an effective crop rotation as part of a control management system.  相似文献   

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