茄科蔬菜立枯丝核菌的融合群鉴定

 Sixty-five samples were collected from rhizosphere soil, hot pepper and tomato plants showing damping-off, root rot and stem rot in Taian, Shouguang of Shandong province and Zhouzhi, Taibai of Shaanxi province. Thirty-nine Rhizoctonia solani isolates were obtained from these samples. The results of anastomosis group (AG) identification and sequence analysis of 5.8S rDNA-ITS of the isolates showed that thirty-six isolates (92.3%) belonged to AG-4, while only three (7.7%) belonged to AG-5. The isolates of AG4 could further be divided into two subgroups of AG4-HG-Ⅰ and AG4-HG-Ⅲ. The 5.8S rDNA-ITS sequences of the selected isolates of the two subgroups had the 99%-100% identity with standard isolates of AG4-HG-Ⅰ and AG4-HG-Ⅲ (from GenBank). Among the analyzed isolates, AG4-HG-Ⅰ subgroup was the dominant with the frequency of 79.5%. Subgroup AG-4-HG-Ⅲ with the frequency of 12.8% was the second. This is the first report that subgroup AG4-HG-Ⅲ of R. solani isolated from Solanaceae vegetable crops in China.     

草莓轻型黄边病毒3'末端序列多态性研究

 The 930 bp segment in 3' terminal region of Strawberry mild yellow edge virus(SMYEV) genome was amplified by 3' rapid amplification of cDNA ends(RACE).Ten Chinese isolates were sequenced,and 7 of them were the same.Nucleotide and amino acid identities and phylogenesis were analyzed between Chinese isolates and 24 isolates from other regions of the world.Sequence analysis of the 878 nt stretch within 3' terminal region of SMYEV genome showed that nucleotide acid identities ranged from 79.5% to 100%,deduced amino acid sequences of coat protein gene identity were 86.4% to 100%.Phylogenetic analysis showed that all isolates of SMYEV fell into four clades.To a certain extent,the clades were related with the geological distribution of SMYEV.Chinese isolates SY01 and SY04 lay in the same clade with European and American isolates,but formed a small separate branch.Isolates SY03 and SY02,derived from Fragaria×ananassa cv.Changhong-2 and F.pentaphylla respectively,had a far relationship with other isolates and fell into one clade.They were likely to be the special isolates that existed only in China.     

引起玉米粗缩病的水稻黑条矮缩病毒山东分离物的分子特性

 Four isolates of Rice black-streaked dwarf virus (RBSDV) were collected from the maize plants showing rough dwarf symptom in Linyi and Tai'an,Shandong province.The S10 genomic sequences of these isolates were determined and compared with those of 14 other RBSDV isolates.All of the four sequences were 1 801 base pairs (bp) long including the 5'-UTR of 21 bp and the 3'-UTR of 103 bp.They all contained an open reading frame of 1 677 bp (22-1698),encoding the coat protein (CP) of 558 amino acids.The sequences of these four RBSDV isolates and those of the major cp gene of 14 other isolates available in the GenBank were divided into two groups in the phylogenetic tree.Recombination analysis indicated that the isolate Lym2 was likely a recombinant of isolates Lym1 and Zhjs.     

湖南柑橘衰退病调查分析及弱毒系筛选

 The investigation showed that stem-pitting Citrus tristeza virus (CTV)occurred commonly in citrus production areas in several varieties of Hunan Province. Accurate detection of CTV strains was performed by p23/PCR method, PCR and the results indicated that the most samples were infected with several CTV isolates. Three mild strains were isolated and their pathogenicity was identified by biological identification, it indicated that p23/PCR groups had uniformity with the pathogenicity of CTV isolates. Furthermore, three mild isolates were tested in the cross protection by analysis of biological symptoms and composition of p23 gene. Different protecting effects were observed among these strains and W17 mild isolate was effective.     

青海海东地区马铃薯晚疫病菌生理小种的组成及分布

 50 isolates of Phytophthora infestans potato plants were collected and tested with 11 monogene R1-R11 of potato late blight differential host in Qinghai province from 2006 to 2007.The results showed that there were 15 races in the Haidong Region of Qinghai province and the dominant race was race 3.4.10 with frequency of 36.0%.They were distributed in all collection areas.Race 3.10 with frequency of 16.0% was distributed in Huzu,Ledu,Huangyuan,Datong and Ping'an.Race 3 with frequency of 10.0% was distributed in Huzhu,Xunhua,Huangyuan and Xining.     

中国不同地理来源稻曲病菌rDNA-IGS的初步分析

 The rDNA-IGS of 11 Ustilaginoidea virens isolates from different geographical regions in China were amplified by PCR and sequenced. The results showed that the rDNA-IGS fragments consisted of one cen-tral variable region and two lateral conservative regions. The two conservative sequences among the11 isolates shared the sequence similarity of 99.44%. The variable region consisted of 2, 4, or 6 of 77 bp-length-repeats in the isolates and the sequences of the repeat units were high conservative. Primers UIGS Ⅲ and UIGS IV were designed for amplification of the variable region in the rDNA-IGS.     

上海地区草莓炭疽病病原鉴定

 Seventeen isolates of strawberry anthracnose were obtained from Shanghai suburb. According to the temperature test for mycelial growth, these isolates were divided into two groups:one was strain CMf-04 with optimal temperature of 24℃, the other was including 16 strains with optimal temperature of 28℃, and most of which could produce sexual stage on PSA media, e.g. QPg-961. Conidia of CMf-04 were hyaline, unicellular, straight and fusiform, (12.1-16.4) μm×(3.6-5.4) μm. Conidia of QPg-961 were hyaline, unicellular and ovoid to oblong, (13.0-19.7)μm×(4.1-7.3) μm. On basis of morphologcal, biological characteristics and the sequences of ribosome rDNA ITS, isolate CMf-04 from the strawberry rotten fruits was identified as Colletotrichum acutatum; while all the other isolates from the diseased leaf stalks, runners and root crowns at strawberry plantlet propagation stage were belonged to Colletotrichum gloeosporioides. It proved that C. gloeosporioides was the main pathogen of the strawberry anthracnose in summer strawberry propagation fields in Shanghai and it is of significance for the breeding of resistant strawberry and its control.     

花生斑驳病毒青岛分离物cp基因序列克隆与分析

 Peanut mottle virus(PeMoV) was detected via RT-PCR from two peanut samples(QD5 and QD6) with mottle symptom collected from Qingdao, Shandong Province.The 3'-terminal 892 bp fragments of their genome were cloned and sequenced.The cp genes of QD5 and QD6 were 837 bp in length and encoded 278 amino acids(aa), with DAA at aa sites regulating aphid transmission.QD5 and QD6 shared nucleotide identities of 95.3%-99.4% and aa identities of 93.5%-99.6% in cp genes with other PeMoV isolates available in the GenBank.The phylogenetic results showed that PeMoV were clustered to three groups, America, Asia and Australia, which were consistent with their geographical origins.This is the first molecular evidence on the incidence of PeMoV in China.     

水稻纹枯病菌菌核上的真菌和细菌种类及其对水稻纹枯病菌生长的影响

 A total of 136 fungal and 86 bacterial isolates were isolated from the sclerotia of Rhizoctonia solani,collected from three different sources.These fungal isolates were identified as the following 12 genera:Alternaria,Aspergillus,Cladosporium,Coniothyrium,Curvularia,Gliocladium,Fusarium,Metarhizium,Peni-cillium,Phoma,Phytophthora and Trichoderma.Some isolates of Trichoderma and Gliocladium were found to inhibit the growth of R.solani strongly in vitro.Among the 86 bacterial isolates,20 of them could inhibit the growth of R.solani,whereas 5 isolates were found to promote the growth of mycelia and the formation of sclerotia of R.solani.These bacterial isolates with antagonistic actives to R.solani were identified as Bacillus and Pseudomonas.     

Characteristics and pathogenicity of isolates of Rhizoctonia spp. associated with damping-off of sugar beet

Rhizoctonia solani and R. cerealis were isolated from diseased sugar-beet seedlings in Ireland. Isolates of R. solani were assigned to anastomosis groups AG-2, AG-4, AG-5 and an unidentified group that did not anastomose with recognized tester isolates. Cultures of AG-2 were similar to those of AG-5 on oatmeal agar (OA) and potato-dextrose-marmite agar (PDMA). Cultures of AG-4, the unidentified group and R. cerealis were morphologically distinct from one another, AG-2 and AG-5. The optimum temperature for growth of AG-2 was 225 C, with optimum growth of AG-4, AG-5 and the unidentified group at 275-C. R. cerealis grew slower than all groups of R. solani, with optimum growth at 225°C. Hyphae of R. cerealis were significantly narrower than those of the groups of R. solani studied. In glasshouse pathogenicity tests, some AG-2 and all AG-4, AG-5 and isolates from the unidentified group caused damping-off of beet seedlings. In controlled environments of 10-25°C, an AG-2 isolate was the most aggressive at 10 C whilst AG-4, AG-5 and the unidentified group caused most disease at or above 15°C. R. cerealis was also pathogenic to beet seedlings, causing damping-off at 10 and 15 C.     

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.     

Differentiation of Three Homogeneous Groups of Rhizoctonia solani Anastomosis Group 4 by Analysis of Fatty Acids

ABSTRACT Profiles of fatty acids from 70 isolates of Rhizoctonia solani anastomosis group (AG)-4 clustered into three groups, corresponding to homogeneous group (HG)-I, HG-II, and a newly described HG-III. Isolates from Georgia peanuts exhibiting limb rot were characterized as gas chromatography (GC) subgroup 1 (GC-1) and contained HG-I isolates. Isolates from diseased soybean hypocotyls grown in North Dakota and sugar beet seedlings, taproots, and tare soil in Minnesota and North Dakota were characterized as GC subgroup 2 (GC-2) and contained predominantly HG-II isolates but also included three distinct isolates based on fatty acid methyl ester (FAME) analysis and morphological features. Selected isolates from North Carolina cucumbers clustered into three distinct groups that corresponded to HG-I, HG-II, and the newly described HG-III. Distinct isolates from the soybean and sugar beet populations clustered with HG-III. Fatty acid profiles of AG-4 were compared with FAME library profiles of AG-1, AG-2 type 2, and AG-3, which were developed in previous studies and were sufficiently different that they could be used to support speciation of this group from R. solani. It is suggested that binomial R. practicola may be appropriate for the portion of AG-4 identified as HG-II.     

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.     

Anastomosis group and pathogenicity of isolates of Rhizoctonia solani from potato crops in South Australia

Isolates of Rhizoctonia collected from the stems, roots, tuber sclerotia and soil of potato crops in Virginia and Lenswood, South Australia, were identified to anastomosis groups (AG). Of the 301 multinucleate isolates of Rhizoctonia solani tested, 90% were AG-3, 7% were AG-4 and 2% were AG-5; 12 isolates were binucleate Rhizoctonia spp. This is the first report of isolates of AG-4 and AG-5 causing disease in potato crops in South Australia. All AG-3, AG-4 and AG-5 isolates tested caused rhizoctonia disease symptoms on the potato cultivar Coliban in pathogenicity trials conducted under glasshotise conditions. Both AG-3 and AG-5 isolates caused black scurf and stem cankers, although symptoms of black scurf were less severe with AG-5. AG-4 isolates produced the most severe stem and stolon cankers of all isolates tested. The pathogenicity of tuber-borne inoculum was confirmed by growing plants from sclerotia-infested tubers. AG-8 isolates from diseased barley and wheat produced severe root cankers and caused loss of feeder roots on inoculated potato plants. Results suggest that rhizoctonia disease in potato fields in South Australia is caused by a combination of different anastomosis groups and this has important implications for crop rotations.     

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.     

新疆11种豆科作物立枯丝核菌菌丝融合群及营养亲和群研究

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。     

Factors affecting infection cushion development by Rhizoctonia solani AG-1 IA and IB on soybean leaves

Infection cushions were formed by isolates of Rhizoctonia solani , anastomosis group 1 IA (AG-1 IA, aerial blight) and AG-1 IB (web blight) on leaves of all 10 soybean cultivars tested. Isolates of AG-1 IA and IB did not form infection cushions on soybean leaf surface replicas of either resistant or susceptible cultivars. More infection cushions were formed by isolates of AG-1 IA and IB on collodion membranes placed over leaves of susceptible cultivars compared with resistant cultivars. Isolates of AG-1 IC. AG-4 and AG-5, also formed infection cushions on soybean leaves. However, the isolates of other anastomosis groups did not form infection cushions on soybean leaves. Differential induction of infection cushion formation by the leaves of various plant species was observed, AG-1 IA formed infection cushions on more graminaceous hosts than AG-1 IB, Our results suggest that a chemical stimulus is needed for infection cushion formation. Glucose and 3- O -methylglucose repressed disease severity caused by AG-1 IA and IB isolates to the same extent. Disease severity and the number of infection cushions formed on leaves of ten soybean cultivars were correlated. Fewer infection cushions were formed on resistant cultivars than on susceptible cultivars.     

Identification of sugar beet germplasm EL51 as a source of resistance to post-emergence Rhizoctonia damping-off

Resistance of sugar beet seedlings to Rhizoctonia damping-off caused by Rhizoctonia solani has not been described. A series of preliminary characterisations using a single susceptible host and four different R. solani isolates suggested the disease progression pattern was predictable. Two AG-4 isolates and a less virulent AG-2-2 isolate (W22) showed a comparable pattern of disease progression in the growth chamber where disease index values increased for the first 5–6 days, were relatively constant for the next 7–8 days, and declined thereafter. Seedlings inoculated with a highly virulent AG-2-2 isolate (R-1) under the same conditions showed similar patterns for the first 4 days post-inoculation; however disease index values continued to increase until seedling death at 13–14 days. Similar results were observed in the greenhouse, and a small expanded set of other germplasm lines were screened. One tested germplasm accession, EL51, survived seedling inoculation with R. solani AG-2-2 R-1, and its disease progress pattern was characterised. In a field seedling disease nursery artificially inoculated with R. solani AG-2-2 R-1, seedling persistence was high with EL51, but not with a susceptible hybrid. Identification of EL51 as a source of resistance to Rhizoctonia damping-off may allow investigations into the Beta vulgaris–Rhizoctonia solani pathosystem and add value in sugar beet breeding.