Haplotypes of ‘<Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter solanacearum’ identified in Umbeliferous crops in Spain

‘Candidatus Liberibacter solanacearum’ is a phloem-limited Gram-negative bacterium that causes serious damage to different crops of the botanical families Solanaceae and Apiaceae. Five haplotypes have been described: LsoA and LsoB are present in solanaceous crops in America and vectored by the tomato/potato psyllid Bactericera cockerelli; LsoC affects carrots from Northern and Central Europe, and is transmitted by the carrot psyllid Trioza apicalis; haplotypes LsoD and LsoE are present in Southern Europe and Morocco in carrot and celery, and are associated with the psyllid Bactericera trigonica. Thirty-four ‘Ca. L. solanacearum’ isolates were collected in six different regions of Spain from distinct Apiaceae hosts (carrot, celery, parsley and parsnip) in eight consecutive years and were analysed. Their haplotypes were determined by a sequence analysis of 16S ribosomal RNA, the 16S–26S ribosomal RNA intergenic spacer, and the 23S ribosomal RNA and rplJ and rplL genes. Both haplotypes LsoD and LsoE were found across Spain, and no host specificity appeared between these two haplotypes. This is the first report of ‘Ca. L. solanacearum’ associated with parsley and parsnip.     

A new interspecific pear cultivar Yutaka: highly resistant to the two major diseases scab and black spot on Asian pears

Phytoplasma suspected symptoms of little leaf, flat stem, witches’ broom and leaf yellowing were recorded on the four legume species, cowpea (Vigna unguiculata (L.) Walp.), pigeon pea (Cajanus cajan (L.) Millsp.), lentil (Lens culinaris Medikus) and mung bean (Vigna radiata (L.) Wilczek) in the states of Delhi, Uttar Pradesh (UP) and Kerala from 2014 to 2016. DNA specific fragments of approximately 1.3 kb were amplified from symptomatic samples of cowpea, pigeon pea, lentil and mung bean in nested PCR assays by using two sets of universal phytoplasma nested specific primers P1/P7 followed by 3Far/3Rev. No DNA amplifications were observed in any of the non-symptomatic legume samples with same primer pairs. Pair wise sequence comparison, phylogeny and virtual RFLP analysis of 16S rDNA sequences of the four legume species confirmed the association of four different groups and subgroups of phytoplasmas in the present study. The mung bean witches’ broom at Delhi was identified to be associated with strain related to ‘Ca. P. aurantifolia’ (16SrII-D), pigeon pea little leaf at Faizabad, UP with strain related to ‘Ca. P. phoenicium’ (16SrIX-C), lentil witches’ broom at Faizabad, UP with ‘Ca. P. trifolii’ (16SrVI-D) and cow pea flat stem disease at Kerala with ‘Ca. P. cynodontis’ (16SrXIV-A). Association of ‘Ca. P. cynodontis' (16SrXIV-A) infecting cowpea, ‘Ca. P. trifolii’ (16SrVI-D) in lentil and phytoplasmas strain related to ‘Ca. P. phoenicium’ (16SrIX-C) infecting pigeon pea are the new reports to the world.     

<Emphasis Type="Italic">Bradyrhizobium</Emphasis> isolated from huanglongbing (HLB) affected citrus trees reacts positively with primers for <Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter asiaticus

Bradyrhizobium sp., a slow-growing nitrogen-fixing symbiotic bacterium of legumes and common root endophyte of other plants, is closely related to Candidatus Liberibacter asiaticus (Las), the uncultured putative pathogen associated with citrus huanglongbing (HLB). In attempts to isolate Las on a low-nutrient medium that had been used for the isolation of several uncultured bacteria of the alpha subclass of proteobacteria, slow-growing Bradyrhizobium spp. were isolated and identified by sequencing of 16S rDNA. The individual isolates tested weakly positive (Ct = 31.2–36.0) with the USDA primers commonly used in qPCR assays for Las in foliar tissues. Direct DNA extracts from roots of HLB symptomatic trees that contained sequences of Bradyrhizobium sp. had Ct values ranging from 31.2 to 36.5; sequences of Las were not present in those samples. Potential cross-reaction between DNA of members of the Rhizobiales and sequences amplified by the Las primers were tested in silico with the Primer-BLAST tool in NCBI. Similar to Las, Bradyrhizobium generated predicted 16S rDNA amplicon sizes of 78–79 bp with the qPCR primers and of 1167-1172 bp with the conventional PCR primers. Bradyrhizobium sequences of 16S rDNA had 1–7 mismatches and only 1 mismatch at the 3′ end of qPCR and conventional PCR primers confirming potential cross-reactivity. As Bradyrhizobium is usually not found in foliage, the USDA qPCR primers can be safely used to check leaves for the presence of Las, but a threshold value of 31.0 is recommended for Las detection in roots. Other primers should be tested for potential cross-reaction with members of the Rhizobiales.     

Sequence and evolutionary analysis of ribosomal DNA from Huanglongbing (HLB) isolates of Western India

Citrus greening (Huanglongbing, HLB) is a widespread and economically important citrus disease all over the world. The disease is caused by a phloem-limited fastidious gram negative bacterium, “Candidatus Liberibacter spp.” which belongs to the alpha-proteobacteria group classified on the basis of its 16SrDNA sequence. Although the pathogen has been classified under three distinct groups, viz. Asian, African and American isolates, nothing is known about the status and the molecular variabilities among the Indian HLB isolates collected from different citrus cultivars grown in India. Five different HLB isolates showing variable symptoms based on their severity of infection on different citrus, viz. Mosambi, Rangpur lime, Cleopatra mandarin, acid lime and rough lemon, were studied by PCR amplification, sequence and evolutionary analysis of their 16S and 16S/23S rDNA intergenic regions. Analysis of the 16S/23S rDNA intergenic region separated all five Indian isolates from existing African isolates but failed to differentiate among Asian, American and Indian isolates. However, further analysis of complete 16S rDNA clearly indicated that Indian isolates fall within the Asian HLB group. Overall, our results suggest that all the five Indian HLB isolates taken for the current analysis belong to the Candidatus Liberibacter asiaticus strain, which showed distinct sequence variabilities and produced noticeable symptoms on the citrus trees. These results provide a robust framework for understanding how differences in pathogenicity among various HLB isolates may be related to evolutionary history.     

Biochemical,physiological, and molecular characterization of <Emphasis Type="Italic">Dickeya dianthicola</Emphasis> (formerly named <Emphasis Type="Italic"> Erwinia chrysanthemi</Emphasis>) causing potato blackleg disease in Japan

The taxonomic assignment of Japanese potato blackleg isolates of Dickeya spp. has not been confirmed after the changes in their former name, Erwinia chrysanthemi. Therefore, we investigated and identified 23 representative isolates of Dickeya spp. from symptomatic stems of potatoes in Japan, with biochemical tests and phylogenetic sequence analysis using recA, dnaX, rpoD, gyrB, and 16S rDNA sequences. Results of our biochemical tests showed that all isolates can be assigned to phenon 5 and biovar 1, which are associated with D. dianthicola. Based on the recA, dnaX, rpoD, gyrB, and 16S rDNA sequences, all isolates are in the same clade with D. dianthicola and were clearly distinguished from D. chrysanthemi, D. dadantii, D. dadantii subsp. dieffenbachiae, D. solani, D. zeae, and D. paradisiaca. Therefore, we conclude that Dickeya spp. isolated from potatoes with blackleg symptoms in Japan are D. dianthicola.     

Important genetic diversity of ‘<Emphasis Type="Italic">Candidatus</Emphasis> Phytoplasma solani’ related strains associated with bois noir grapevine yellows and planthoppers in Azerbaijan

Bois noir (BN) is an important grapevine yellows endemic to the Euro-Mediterranean basin caused by ‘Candidatus Phytoplasma solani’ (‘Ca. P. solani’), a non culturable plant pathogenic Mollicute. Bois noir symptoms could be associated with ‘Ca. P. solani’ in two Azerbaijanian vineyards where disease incidence and severity were recorded for five local Vitis vinifera cultivars. In order to gain insight into the epidemiology of Bois noir in Azerbaijan, ‘Ca. P. solani’ isolates infecting plants were characterized by multi-locus sequence analysis and their secY and stamp gene sequences compared to that of the strains detected in other plants and in local Cixiidae planthoppers. Genotypes were determined for two non-ribosomal house-keeping genes, namely tuf and secY, as well as two variable markers namely Stamp and mleP1 genes, that respectively encode the antigenic membrane protein AMP and a 2-Hydroxycarboxylate transporter. The Azerbaijanian BN phytoplasma isolates corresponded to three tufB and secY genotypes. A finer differentiation of Azerbaijanian ‘Ca. P. solani’ isolates was obtained with mleP1 as five different mleP1 genetic variants were found. Finally, Stamp gene allowed differentiating four new genotypes in grapevine among the 10 new Stamp genotypes detected in various plants in Azerbaijan. The preliminary survey for infected insects conducted in northern Azerbaijan, led to the identification of Hyalesthes obsoletus and Reptalus noahi as potential vectors for two ‘Ca. P. solani’ new genotypes phylogenetically distant from the known genetic clusters. Altogether these results indicate an important genetic diversity of BN phytoplasmas in Azerbaijan that certainly result from spread through local insect vectors.     

Multilocus sequence analysis supports a low genetic diversity among ‘<Emphasis Type="Italic">Candidatus</Emphasis> Phytoplasma australasia’ related strains infecting vegetable crops and periwinkle in Egypt

‘Candidatus Phytoplasma australasia’ causes important damages to the Egyptian vegetable crop production. A prerequisite for controlling the different diseases it causes to eggplant, tomato and squash, is to trace its propagation pathways. To allow the differentiation of ‘Ca. P. australasia’ strains, a multilocus sequence analysis protocol was developed. Four conserved phytoplama genes namely tuf, secY, dnaK and dppA, were selected among the CDS of a ‘Ca. P. aurantifolia’ genome draft. The corresponding genes were PCR amplified from tomato, eggplant and squash collected in 2010 from the governorates Sharkia, Elmynia and Beni sueif, as well as from Catharanthus roseus periwinkles collected in 2013 from Kafrelsheikh governorate. Sequence comparisons showed no diversity among the Egyptian isolates of ‘Ca. P. australasia’ that also constitute a distinct cluster within the 16SrII-D taxonomic subgroup. This low diversity supports a common epidemiology for the different diseases affecting vegetable crops and periwinkle in Egypt and suggests that future investigations on insect vector should focus on polyphagous leafhoppers.     

Genetic variability within <Emphasis Type="Italic">Septoria carvi</Emphasis> Syd.- a pathogen of caraway <Emphasis Type="Italic">Carum carvi</Emphasis> L

Genetic variability within Septoria carvi isolates obtained from various organs of caraway cultivated in south-eastern and central Poland was studied using the RAPD-PCR technique. The tests were performed using randomly selected primers. The DNA profiles obtained using four primers proved useful in determining genetic variability among the genotypes of Septoria carvi isolates. The present study characterized the differences in the nucleotide sequence within the internal transcribed spacer region of rDNA (ITS1, 5.8S, ITS2) of selected S. carvi isolates and reference strains of Septoria spp. Moreover, eight isolates were sequenced for three loci: actin, calmodulin and translation elongation factor 1-alpha, and the obtained sequences were compared with the sequences of Septoria reference strains affecting other plants of the family Apiaceae. Phylogenetic analysis showed distinct differences of the tested isolates, which allowed to treat them Septoria carvi species affecting the above-ground organs of caraway Carum carvi L. This study is the first report on the genetic characteristics of the species S. carvi.     

Search for reservoirs of ‘<Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter solanacearum’ and mollicutes in weeds associated with carrot and celery crops

Currently, the main arthropod vectored pathogens associated with carrot and celery crop diseases are ˋCandidatus Liberibacter solanacearum´, Spiroplasma citri and different phytoplasma species. Mitigation strategies require elucidating whether these pathogens survive in the weeds of these Apiaceae crops, which can act as reservoirs. Weed surveys were conducted in a vegetative cycle (April to October 2012) in the spontaneous vegetation that surrounded crops affected by ˋCa. L. solanacearum´, S. citri and/or phytoplasmas. Sixty-three species of 53 genera that belong to 23 botanical families were collected in the main carrot and celery Spanish production area. Species were identified, estimating coverage and abundance, and conserved in herbarium. Samples were analysed by nested-PCR with universal primers for phytoplasmas detection, and were sequenced for identification purposes; by conventional PCR for S. citri and real-time PCR for ˋCa. L. solanacearum´. The only detected pathogens were ˋCa. Phytoplasma trifolii´ (clover proliferation group 16Sr VI-A) in Amaranthus blitoides and Setaria adhaerens and ˋCa. P. solani´ (stolbur group 16Sr XII-A) in Convolvulus arvensis. These pathogens were also sporadically detected in celery or carrot crops. Unexpectedly, neither ˋCa. L. solanacearum´ nor S. citri was detected in the weed samples, despite the relatively high prevalence of these pathogens (less than 66 % and 25 %, respectively) in the surveyed plots. This suggests that weeds do not play an epidemiological role as reservoirs in the spread of such organisms in the studied region. The use of pathogen-free seed lots and the control of vectors are crucial for preventing the introduction and spread of these economical important pathogens to new areas.     

Efficacy of some rhizospheric and endophytic bacteria <Emphasis Type="Italic">in vitro</Emphasis> and as seed coating for the control of <Emphasis Type="Italic">Fusarium culmorum</Emphasis> infecting durum wheat in Tunisia

Sixty two rhizospheric and endophytic bacterial strains were evaluated for their biocontrol effect on two aggressive Fusarium culmorum isolates (Fc2 and Fc3). We observed that 35 % and 23 % of the tested strains inhibited the in vitro growth of Fc2 and Fc3 respectively. The observed antagonism was due to inhibition by contact (13–19 % of the strains) or at distance (10–16 % of the strains) for both fungal isolates. Some of the antagonistic bacteria showed the ability to produce diffuse and/or volatile compounds that inhibit the growth, the sporulation and macroconidia germination of F. culmorum. None of the tested antagonistic bacteria showed chitinase activity on synthetic medium. The sequencing of the 16S rDNA genes of some antagonistic bacteria showed that they belong to the genera Bacillus, Pseudomonas and Microbacterium. The double inoculation of durum wheat seeds by the antagonistic bacterial strains (B13, B18, BSE1, BSE3 and B16E) and the two F. culmorum isolates showed that germination and seedling vigor were generally improved in vitro. The percentage of infected seeds was also reduced. In greenhouse trials, the biocontrol effectiveness of F. culmorum was dependant from the virulence of the fungal strain and the specificity of the antagonistic interaction between bacterial and fungal strains. The bacterial strains B18 and B16E reduced F. culmorum infection on durum wheat plants probably due to their antagonistic and plant growth promoting activities and they may be used in a mixture as seed biopriming inoculum for plant growth bio-promoting and Fusarium wheat diseases biocontrol.     

Molecular and experimental evidence of multi-resistance of <Emphasis Type="Italic">Cercospora beticola</Emphasis> field populations to MBC,DMI and QoI fungicides

Binucleate Rhizoctonia (BNR) spp. isolates were collected from taro (Colocasia esculenta (L.) Schott) and ginger (Zingiber officinale (Willd.) Roscoe) (Yunnanxiaojiang cv.) in Yunnan province. These Yunnan (YN) isolates did not anastomose with any of the tester isolates of the known AGs of binucleate Rhizoctonia spp. The growth of YN cultures on PDA was appressed, mealy and matlike after 4 days of incubation, then turned white brown, producing brown to dark brown, irregularly shaped sclerotia were embedded in the PDA medium after 14 days. All attempts to induce basidiospore production were unsuccessful, but the length and sequence of the internal transcribed spacer (ITS1 + 5.8S rDNA + ITS2) regions of 5.8S rDNA from the YN isolates were identical in length and sequence to isolates of all the other AGs of binucleate Rhizoctonia /Ceratobasidium spp. The sequences of 5.8S rDNA-ITS from the YN isolates were unique among AGs of BNR. The YN isolates had sequence similarities of 94% with isolates of AG Fb and P, 93% with AG E, 91% with AG R, 79–94% with AG S, and 74–87% with AG A, Ba, Bb, Bo, C, DI, DII, DIII, Fa, G, H, I, K, L, O, and Q. Four isolates of AG YN caused minor virulence (lesions ≦1mm²⁾ to ginger or taro in growth chamber studies. It was concluded that the YN isolates belong to a new anastomosis group AG-V of the Ceratobasidium spp..     

Integrative identification and molecular phylogeny of dagger and needle nematodes associated with cultivated olive in Tunisia

The occurrence and geographic distribution of longidorid nematode species inhabiting the rhizosphere of cultivated olive (cvs. Chemlali and Chétoui) in Tunisia were investigated. Morphological and morphometrical studies identified three Longidorus and six Xiphinema species, with frequencies of prevalence as following: Longidorus africanus (23.0 %), L. euonymus (4.5 %), L. glycines (13.7 %), Xiphinema conurum (13.7 %), X. italiae (36.4 %), X. meridianum (13.7 %), X. pachtaicum (18.2 %), X. robbinsi (9.1 %), and Xiphinema sp. (4.5 %). The three Longidorus species were reported for the first time in Tunisia, in addition to two species of Xiphinema (viz. X. meridianum and X. robbinsi). Molecular characterisation using D2-D3 expansion regions of 28S rRNA and ITS1-rRNA was carried out and Bayesian inference analysis was used to reconstruct phylogenetic relationships among these species and with other longidorids. Twenty-five new D2-D3 of 28S rRNA gene sequences were obtained in the present study, seven for Longidorus and 18 for Xiphinema spp., as well as 14 new ITS1 rRNA gene sequences (seven for Longidorus and seven for Xiphinema spp.).     

Comparison among Japanese isolates of <Emphasis Type="Italic">Pseudomonas savastanoi</Emphasis> pv. <Emphasis Type="Italic">savastanoi</Emphasis>, causal agent of olive knot disease

Olive knot disease in Japan was first reported in Shizuoka Prefecture in 2014, and the causal agent was identified as Pseudomonas savastanoi pv. savastanoi. Subsequently, olive trees having knots were also found in Aichi and Kanagawa Prefectures in 2015, and the isolates from knots were also suspected to be P. savastanoi pv. savastanoi through preliminary examinations. Therefore, the Aichi and Kanagawa isolates were identified through comparison of isolates from three prefectures. Phylogenic analysis based on 16S rDNA and housekeeping genes (gyrB, rpoD, gltA and gap1) revealed that the isolates belonged to the same cluster as the pathotype strain, ICMP4352^PT. The iaaM, H and L genes, which are involved in promotion of symptoms, and the ina gene coding the ice nucleation protein, were detected by PCR from all the isolates. In rep-PCR (ERIC and REP) analyses, the isolates yielded DNA fragment-banding patterns that were nearly identical to that of ICMP4352^PT, but slight variations in banding patterns were observed among them. In a pathogenicity test, the isolates formed distinct knots on olive and pink jasmine. Phenotypic properties of the isolates were almost identical to those of ICMP4352^PT, with the exception of d-sorbitol utilization. Consequently, Aichi and Kanagawa isolates from olive were identified as P. savastanoi pv. savastanoi, and several genetic diversities in terms of rep-PCR were found in the Japanese population of P. savastanoi pv. savastanoi, indicating their heterogeneity.     

Morphological and molecular characterisation of <Emphasis Type="Italic">Ditylenchus stenurus</Emphasis> n. sp. (Nematoda: Anguinidae) from western Iran

A new species in the genus Ditylenchus, D. stenurus n. sp. collected from western Iran, is described and illustrated herein based on morphological and molecular studies. The new species is characterised by a body length of 772 (663–863) μm, delicate stylet 6 (5–7) μm long, six lines in the lateral field. Median bulb of pharynx well-developed, muscular with crescentic valve. Post-vulval uterine sac well-developed, 35 (30–45) μm long, female tail elongate-conoid, becoming narrow suddenly with finely rounded terminus. The new species comes close in morphology and morphometrics to five known species of the genus, namely D. arachis, D. caudatus, D. clarus, D. myceliophagus, and D. nanus. DNA sequencing data was obtained on the partial 18S, D2/D3 expansion segments of the 28S rRNA gene and internal transcribed spacer (ITS). The phylogenetic relationships of this species with other Ditylenchus spp. using partial 18S–rDNA and D2/D3 indicated that D. stenurus n. sp. clustered together with several species belongs to the D. triformis-group i. e. D. africanus, D. destructor and D. halictus: all sharing a rounded tail terminus and six lines in lateral fields.     

西瓜细菌性果斑病菌的16S rDNA序列分析及特异性引物的设计

 利用细菌16S rDNA基因的通用引物对16个供试菌株进行PCR扩增,把扩增产物进行核苷酸序列测定。将获得的序列与GenBank中相关菌株的16S rDNA序列进行同源性分析。以此设计出检测A.a.c的特异性引物,并利用最大简约法构建了16S rDNA系统演化树。系统演化关系分析表明,6~9号供试菌株的16S rDNA序列与A.a.c标准菌株仅有3个位点的差异,其同源性均在99.8%以上,在构建的系统演化树上,它们聚为同一个族群。利用设计的一对特异性引物(BFB64/65),对各供试菌株进行PCR检测,结果只有A.a.c相关菌株产生扩增条带,产物大小与预期一致。     

Detection and identification of a ‘<Emphasis Type="Italic">Candidatus</Emphasis> phytoplasma aurantifolia’-related strain (16SrII-A subgroup) associated with <Emphasis Type="Italic">corchorus aestuans</Emphasis> phyllody in China

In September 2015, a phyllody that is typical of phytoplasma infection was observed on Corchorus aestuans plants in Haikou, Hainan Province, China. Total DNA from symptomatic and asymptomatic plants was extracted for molecular diagnosis. On the basis of sequence analysis and phylogenetic trees based on 16S rDNA and rp genes, the phyllody phytoplasma was ascertained to be related to ‘Candidatus phytoplasma aurantifolia’. To the best of our knowledge, this is the first report of a phytoplasma infecting C. aestuans in the world.     

Conidial sporulation of <Emphasis Type="Italic">Stemphylium solani</Emphasis> under laboratory conditions and infectivity of the inoculum produced <Emphasis Type="Italic">in vitro</Emphasis>

Potato virus Y (PVY) is the type-species of the genus Potyvirus, family Potyviridae, being reported as a major tomato (Solanum lycopersicum L.) pathogen in several regions of the world. Pepper yellow mosaic virus (PepYMV) was originally described as a resistance-breaking Potato virus Y (PVY) isolate on Capsicum annuum L. cultivars, and afterwards it was also reported infecting tomatoes in Brazil. In the present work, a search for sources of resistance to both PepYMV and PVY was conducted in a collection of 119 accessions belonging to seven Solanum (section Lycopersicon) species. This germplasm was initially evaluated to PepYMV reaction by mechanical inoculation followed by symptom observations and ELISA. Potential PepYMV resistance sources were identified for the first time in S. habrochaites, S. peruvianum, S. corneliomuelleri, S. chilense, S. pimpinellifolium, and one accession derived from an interspecific cross (S. lycopersicum x S. peruvianum). A sub-group of 24 accessions with negative serology for PepYMV was also challenged with a PVY isolate, followed by serological and molecular detection with universal primers. Solanum habrochaites ‘L.03683’ and ‘L.03684’ were the only accessions found with stable resistance to both viruses. These results confirm S. habrochaites as the most important source of multiple resistance factor(s) to distinct Potyvirus species.     

Construction of a recombinant strain of <Emphasis Type="Italic">Pseudomonas fluorescens</Emphasis> producing both phenazine-1-carboxylic acid and cyclic lipopeptide for the biocontrol of take-all disease of wheat

Four Neofabraea species are responsible for bull’s eye rot, which is an important postharvest disease of apples and pears. The species diversity of its causal agents in Europe has not been thoroughly explored using molecular genetic methods. Eighty-one Neofabraea isolates were obtained mostly from apples with bull’s eye rot symptoms in the Czech Republic over a two year period. The isolates were identified using PCR fingerprinting and DNA sequencing of the ITS rDNA region, the mitochondrial SSU rDNA and the β-tubulin and EF1α genes. The most common species was N. alba (89 %), followed by N. perennans (5 %) and N. kienholzii (5 %). This is the third published record of N. kienholzii in Europe. The species identity of the isolate CPPF507, which was placed close to N. kienholzii, remains unclear. EF1α was shown to be a suitable marker for the identification of species of the genus Neofabraea and was comparable to the previously used β-tubulin gene. Furthermore, the aggressiveness of individual species was compared and species distribution across Europe was summarized. N. perennans and isolate CPPF507 proved to be the most aggressive, whereas the least aggressive was N. kienholzii. Two N. alba isolates isolated from symptomless apple fruits and leaves were pathogenic to apples in the infection tests.     

Morphological and molecular analysis of <Emphasis Type="Italic">Paratrichodorus teres</Emphasis> (Hooper 1962) (Nematoda: Trichodoridae): a groundwork for discussion on the phylogeny and pathogenicity of <Emphasis Type="Italic">Paratrichodorus</Emphasis> species

Due to its ability to transmit plant viruses, Paratrichodorus teres (Hooper in Nematologica, 7, 273–280, 1962) is recognized as an economically important trichodorid species. Morphological and molecular analyses (18S and 28S rDNA) were performed, and 10 new plant hosts are reported for Polish P. teres populations. Major morphological features and the measurements obtained for the investigated specimens were within the wide ranges indicated for this species. However, a more detailed comparative analysis of Polish and Iranian P. teres showed significant morphological differences, particularly, in the shape and the structure of the walls of pars proximalis vaginae and the shape of the rectum.Phylogenetic study based on the 18S rDNA data suggests positioning of the Polish P. teres sequences within a cluster of sequences originating from the Netherlands. A comparison of the 28S rDNA fragment from Polish populations with the only P. teres 28S rDNA sequence available (from Iran) in GenBank revealed a sequence variability of 9.3%. The variation across these two representatives was higher than in the case of many other pairs of Trichodoridae species. The results obtained on the Polish P. teres specimens are discussed in the framework of the species taxonomy and phylogenetic relationships.     

Biological control of green mould on <Emphasis Type="Italic">Agaricus bisporus</Emphasis> by a native <Emphasis Type="Italic">Bacillus subtilis</Emphasis> strain from mushroom compost

Fifty bacterial isolates obtained from compost were tested in vitro against the causal agents of green mould in Agaricus bisporus. Isolate B-38 which induced 48.08% in vitro growth inhibition of T. harzianum T54 and 52.25% of T. aggressivum f. europaeum T77 was identified as Bacillus subtilis, based on 16S rDNA sequence and used in mushroom growing room experiments. B. subtilis B-38 did not decrease mycelial growth rate of Agaricus bisporus A15 in mushroom compost in glass tubes. After applying prochloraz-manganese, B. subtilis B-38 and B. subtilis QST 713, no significant differences in BE values among treatments were found concerning both total yield and the weight of healthy mushrooms. Statistical analyses showed that only inoculation significantly influenced the healthy mushroom yield. In plots inoculated with T. harzianum T54 disease incidence was significantly lower after treatments with prochloraz-manganese (11.81%), B. subtilis QST 713 (12.26%) and B. subtilis B-38 (14.19%) compared to the control (28.16%), as well as in plots inoculated with T. aggressivum f. europaeum T77 11.88%, 12.2% and 15.03%, respectively, in comparison with the control (23.47%). Statistically significant differences were not found among the efficacy values of tested bio-fungicides based on B. subtilis and the commercial fungicide prochloraz-manganese suggesting the use of B. subtilis B-38 and B. subtilis QST 713 as good alternatives to chemical fungicides.