<Emphasis Type="Italic">Teratosphaeria (Mycosphaerella) nubilosa,</Emphasis> the causal agent of Mycosphaerella leaf disease (MLD), recently introduced into Uruguay

Mycosphaerella leaf disease on Eucalyptus is well known in Uruguay but none of the more serious Mycosphaerella spp. and Teratosphaeria spp. causing this disease have yet been found. In the autumn of 2007, more severe defoliation than has been known in the past and associated with symptoms resembling Mycosphaerella infections was observed on Eucalyptus globulus. Isolations and identifications based on morphology and DNA sequence comparisons showed that the causal agent of the defoliation is the well known and serious pathogen Teratosphaeria nubilosa (=Mycosphaerella nubilosa). This is the first record of the pathogen in South America. Using ten microsatellite loci previously developed for T. nubilosa, only one multilocus haplotype was found from 46 T. nubilosa collected isolates. Interestingly, this haplotype was the same as one previously found in Portugal and Spain. The results suggest that T. nubilosa has recently been introduced into Uruguay and that it most likely originated from the Iberian Peninsula where E. globulus is widely planted.     

Presence of the <Emphasis Type="Italic">Eucalyptus</Emphasis> gall wasp <Emphasis Type="Italic">Ophelimus maskelli</Emphasis> and its parasitoid <Emphasis Type="Italic">Closterocerus chamaeleon</Emphasis> in Portugal: First record,geographic distribution and host preference

The Eucalyptus gall wasp Ophelimus maskelli (Hymenoptera: Eulophidae) and its parasitoid Closterocerus chamaeleon (Hymenoptera: Eulophidae) were observed for the first time in Portugal, in 2006 and 2007, respectively. Data on the distribution of O. maskelli in Portugal, differences in the susceptibility of two host species, Eucalyptus globulus and Eucalyptus camaldulensis, and parasitism by C. chamaeleon are given.     

Leaf Smut of <Emphasis Type="Italic">Sagittaria latifolia </Emphasis>Caused by <Emphasis Type="Italic">Doassansia horiana</Emphasis>

A smut-like disease was found on the leaves of Sagittaria latifolia in Japan. Spore balls collected from the leaves of S. latifolia and S. trifolia var. edulis were used to cross-inoculate leaves of pathogen-free plants of the two species to identify the pathogen. Spots and swellings formed on leaves of the two species 10 days after inoculation. These symptoms were quite similar to those of the leaf smut disease of S. trifolia var. edulis caused by Doassansia horiana, and the spore balls were characteristic of the fungus. Therefore, the authors conclude that D. horiana caused leaf smut disease on S. latifolia. Received 18 January 2000/ Accepted in revised form 14 May 2000     

Epidemiology of <Emphasis Type="Italic">Pseudomonas syringae</Emphasis> pv. <Emphasis Type="Italic">syringae</Emphasis> on tomato

Leaf spot of tomato, incited by Pseudomonas syringae pv. syringae, has been reported recently in Italy on grafted and non-grafted tomato plants (scion Cuore di Bue, rootstock Solanum lycopersicum x Solanum hirsutum cv. Beaufort). In some greenhouses, more than 80% of plants were affected, with a marked reduction in yield. This work was undertaken in order to understand the effect of the number of hours of incubation at high relative humidity (r.h.) and temperature as well as the effect of the presence of wounds at infection time on the development of leaf spot. A difference in sensitivity to leaf spot was observed in the various cultivars tested, in terms of severity of P. syringae pv. syringae, with “Cuore di Bue” being the most susceptible of these cultivars. The development of leaf spot is mostly favored by the presence of wounds, at temperatures between 15 and 20°C. The severity of the disease is lower at 10 and 25°C and very low at 30°C. Under the most favorable temperature conditions, the presence of wounds is sufficient to allow the development of the pathogen immediately upon incubation at high r.h. The effect of wounds and the relatively low requirement of hours of incubation at high r.h. suggest the need for careful management and handling of plants when temperatures range between 15 and 25°C, and particularly within 15 and 20°C. All operations carried out, particularly at transplant and immediately after, should avoid the creation of wounds.     

Identification and characterization of the <Emphasis Type="Italic">Enterobacter</Emphasis> complex causing mulberry (<Emphasis Type="Italic">Morus alba</Emphasis>) wilt disease in China

Mulberry wilt disease (MWD) was recently identified in Hangzhou, Zhejiang province, China. Typical symptoms of the disease are browning of vascular tissues, leaf wilt, defoliation, and tree decline. Unlike the symptoms of bacterial wilt disease caused by Ralstonia solanacearum, symptoms of MWD generally started from the bottom of the plants and moved upward. In inoculation experiments, four selected MWD strains caused mulberry shoot leaf wilt, discoloration, and defoliation. They also induced whole plant leaf wilt, defoliation and dark brown discoloration of vascular tissue. Based on Biolog metabolic profiles, fatty acid methyl ester analysis (FAME) and sequence analysis of the partial 16S rDNA and rpoB genes four MWD strains were identified as members of the genus Enterobacter. The 16S rDNA and rpoB gene sequences revealed a close relationship among two isolates, R2-2 and R6-2, and the E. asburiae type strain JCM6051. The isolates showed >98% similarity to E. asburiae JCM6051 in their rpoB gene. These results indicated that isolates R2-2 and R6-2 belonged to E. asburiae. No similarity in 16S rDNA sequences above 97% was found between either of the remaining isolates, R11-2 or R18-2, and any recognized Enterobacter species, suggesting that the two isolates may represent novel Enterobacter species. rpoB gene similarity values between the isolates and Enterobacter spp. type strains were <98%, providing further evidence that the two isolates may represent a novel species within the Enterobacter. The causal agent for MWD was previously reported to be E. cloacae, however, this study found that other Enterobacter spp. (E. asburiae and Enterobacter sp.) also cause MWD.     

Host range and phytotoxicity of <Emphasis Type="Italic">Stemphylium solani</Emphasis>, causing leaf blight of garlic (<Emphasis Type="Italic">Allium sativum</Emphasis>) in China

Since 2004, a new leaf blight disease on garlic of high severity has been observed in Dangyang County, Hubei province, China. Initial symptoms consisted of multiple, small, irregular to oval, white leaf spots, which enlarge to produce sunken purple lesions, sometimes surrounded by a bright yellow margin. As the disease progressed, lesions expanded and merged, resulting in withering of leaf tips. After isolation and pathogenicity testing, the causal agent of leaf blight of garlic was identified as Stemphylium solani from cultural and morphological characteristics, and subsequent analysis of the internal transcribed spacer region of ribosomal DNA. When fungal plugs of two S. solani isolates were inoculated onto 11 garlic cultivars and 20 other crop species, leaf spots appeared on all inoculated plants, but two garlic cultivars (Qingganruanye and Ruanruanye) and three crop species (Capsicum annuum, Brassica napus and Amaranthus mangostanus) showed the smallest leaf spots. In cross-inoculation experiments, no indications of host specificity were observed, but S. solani isolated from garlic was generally the most virulent on five plant species, while the isolate from leek (Allium odorum) was generally the least virulent. Toxicity testing of the crude culture filtrates indicated that garlic isolates produced toxin(s) that were not heat-labile and induced different levels of phytotoxicity toward various garlic cultivars and crops.     

First report of blueberry red ringspot disease caused by <Emphasis Type="Italic">Blueberry</Emphasis><Emphasis Type="Italic">red</Emphasis><Emphasis Type="Italic">ringspot</Emphasis><Emphasis Type="Italic">virus</Emphasis> in Japan

Virus-like symptoms—red ringspots on stems and leaves, circular blotches or pale spots on fruit—were found on commercial highbush blueberry (Vaccinium corymbosum) cultivars Blueray, Weymouth, Duke and Sierra in Japan. In PCR testing, single DNA fragments were amplified from total nucleic acid samples of the diseased blueberry bushes using primers specific to Blueberry red ringspot virus (BRRV). Sequencing analysis of the amplified products revealed 95.7–97.7% nucleotide sequence identity with the BRRV genome. This paper is the first report of blueberry red ringspot disease caused by BRRV in Japan. The nucleotide sequence data reported in this paper are available in the GenBank/EMBL/DDBJ database as accessions AB469884 to AB469893 for BRRV isolates from Japan.     

Diversity of Mycosphaerella spp. and Teratosphaeria spp. in Eucalyptus globulus plantations in Brazil

Among the most important diseases affecting Eucalyptus is Mycosphaerella Leaf Disease (MLD) caused by Mycosphaerella spp. and Teratosphaeria spp. MLD has led to significant losses in eucalypt plantations in the South and Southeast Region of Brazil, as well as in several countries such as Portugal, Spain, South Africa and Australia. Symptoms of MLD include localized necrotic spots, early defoliation in juvenile plants, stem cankers, early death of branches, and in some cases, atrophy and death. In the present study, single spore isolations from leaves of E. globulus from five locations in Brazil allowed the differentiation of species of Mycosphaerella and Teratosphaeria based on ascospore germination and growth in culture. These isolates were also subjected to sequence analysis of the ribosomal RNA internal transcribed spacer regions, which allowed their identification to species level. The results of this study showed that six species of Mycosphaerella and four species of Teratosphaeria were associated with leaves showing symptoms of MLD in E. globulus plantations in various locations of Brazil.     

Resistance to <Emphasis Type="Italic">Penicillium</Emphasis><Emphasis Type="Italic">hirsutum</Emphasis> Dierckx in garlic accessions

Among the factors affecting the quality and yield of garlic production, blue mold caused by -- Penicillium spp. -- is responsible for economical losses in many countries. Allicin, present in garlic bulbs, has been suggested as having antifungal activity against some Penicillium species. This study was conducted to evaluate the response of garlic accessions against Penicillium hirsutum infection and to compare this response with bulb allicin content. Twelve garlic accessions were inoculated with P. hirsutum, and assayed in greenhouse and growth chamber experiments. Plant growth parameters and the fungal production of conidia were evaluated. Significant differences were found among the accessions. Accessions Castaño and Morado were most resistant whereas AR-I-125 and Fuego were always severely affected by the disease. A low correlation was found (r = 0.17) between allicin content and tolerance, indicating that allicin is not the main factor involved in the resistance against P. hirsutum.     

A new leaf blight disease of <Emphasis Type="Italic">Trifolium dasyurum</Emphasis> caused by <Emphasis Type="Italic">Botrytis fabae</Emphasis>

A new disease was observed on Trifolium dasyurum, with symptoms beginning as a halo spot and developing into a leaf blight. The causal organism was identified by microscopy and DNA sequence studies as Botrytis fabae. This strain of B. fabae was also demonstrated to cause disease on foliage of a range of pulse crops, including Vicia faba, Pisum sativum, and Lens culinaris. This study demonstrates the potential of this strain of B. fabae to not only pose a significant threat to T. dasyurum but also to pulses grown in rotation with T. dasyurum that are susceptible to this strain of B. fabae.     

Inheritance of resistance in <Emphasis Type="Italic">Solanum nigrum</Emphasis> to <Emphasis Type="Italic">Phytophthora infestans</Emphasis>

Solanum nigrum, black nightshade, is a wild non-tuber bearing hexaploid species with a high level of resistance to Phytophthora infestans (Colon et al. 1993), the causal agent of potato late blight, the most devastating disease in potato production. However, the genetic mode of resistance in S. nigrum is still poorly understood. In the present study, two S. nigrum accessions, 984750019 (N19) and #13, resistant (R) and susceptible (S), respectively, to three different isolates of P. infestans, were sexually crossed. The various kinds of progeny including F1, F2, F3, and backcross populations (BC₁; F1 × S), as well as two populations produced by self-pollinating the R parent and S parent, were each screened for susceptibility to P. infestans isolate MP 324 using detached leaf assays. Fifty seedling plant individuals of the F1 progeny were each resistant to this specific isolate, similarly to the seedling plants resulting from self-pollination of the resistant R parent. Thirty seedling plants obtained from self-pollination of the S parent were susceptible. Among a total of 180 F2 plants, the segregation ratio between resistant and susceptible plants was approximately 3: 1. Among the 66 seedling plants of the BC₁ progeny originating from crossing an F1 plant with the susceptible S parent, there were 26 susceptible and 40 resistant plants to P. infestans. The segregation patterns obtained indicated monogenic dominant inheritance of resistance to P. infestans isolate MP 324 in S. nigrum acc. 984750019. This gene, conferring resistance to P. infestans, may be useful for the transformation of potato cultivars susceptible to late blight.     

Diversity and potential impact of Botryosphaeriaceae species associated with <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> plantations in Portugal

Eucalyptus globulus, a non-native species, is currently the most abundant forest species in Portugal. This economically important forest tree is exploited mainly for the production of pulp for the paper industry. The community of Botryosphaeriaceae species occurring on diseased and healthy E. globulus trees was studied on plantations throughout the country. Nine species from three different genera were identified, namely Botryosphaeria (B. dothidea), Diplodia (D. corticola and D. seriata) and Neofusicoccum (N. australe, N. algeriense, N. eucalyptorum, N. kwambonambiense, N. parvum and Neofusicoccum sp.). Of these, N. algeriense, D. corticola and D. seriata are reported for the first time on E. globulus, while N. algeriense, N. eucalyptorum and N. kwambonambiense correspond to first reports in Portugal. The genus Neofusicoccum was clearly dominant with N. australe and N. eucalyptorum being the most abundant species on both diseased and healthy trees. In artificial inoculation trials representative isolates from all nine species were shown to be pathogenic to E. globulus but there were marked differences in aggressiveness between them. Thus, D. corticola and N. kwambonambiense were the most aggressive while B. dothidea and D. seriata were the least aggressive of the species studied.     

Pythium rot of figmarigold (<Emphasis Type="Italic">Lampranthus spectabile</Emphasis>) caused by <Emphasis Type="Italic">Pythium aphanidermatum</Emphasis>

A new leaf rot disease was found on the leaves of figmarigold (Lampranthus spectabile). The causal organism, identified as Pythium aphanidermatum was found to cause the same symptoms after artificial inoculation and was then reisolated from the inoculated plants. We propose to name the disease Pythium rot of figmarigold.     

Black leaf spot of Japanese persimmon (<Emphasis Type="Italic">Diospyros kaki</Emphasis>), a new disease caused by <Emphasis Type="Italic">Adisciso kaki</Emphasis> sp. nov.

A new defoliating disease with severe leaf spot of Japanese persimmon (Diospyros kaki) was found in Shimane Prefecture. A fungus, isolated from the ascospores that had formed on the leaf spot, was demonstrated to reproduce the symptoms on leaves and described as a new species, Adisciso kaki, based on morphological and molecular phylogenetic analyses. This fungus is characterized by small ascomata without clypeus, obclavate to broadly cylindrical asci with an amyloid apical apparatus, and hyaline ascospores with a submedian septum. We coined the name black leaf spot (Kurohoshi-rakuyo-byo, in Japanese) for the new disease.     

<Emphasis Type="Italic">Fusarium langsethiae</Emphasis> pathogenicity and aggressiveness towards oats and wheat in wounded and unwounded <Emphasis Type="Italic">in vitro</Emphasis> detached leaf assays

In vitro detached leaf assays involving artificial inoculation of wounded and unwounded oat and wheat leaves were used to investigate the potential pathogenicity and aggressiveness of F. langsethiae, which was linked recently to the production of type A trichothecenes, HT-2 and T-2 in cereals in Europe. In the first two experiments, two assays compared disease development by F. langsethiae with known fusarium head blight pathogen species each used as a composited inoculum (mixture of isolates) at 10°C and 20°C and found all fungal species to be pathogenic to oat and wheat leaves in the wounded leaf assay. In the unwounded leaf assay, F. langsethiae was not pathogenic to wheat leaves. Furthermore, there were highly significant differences in the aggressiveness of pathogens as measured by lesion length (P < 0.001). In the second two experiments, pathogenicity of individual F. langsethiae isolates previously used in the composite inoculum was investigated on three oat and three wheat varieties. The wounded leaf assay showed that all isolates were pathogenic to all oat and wheat varieties but only pathogenic towards oat varieties in the unwounded assay. Highly significant differences (P < 0.001) in lesion length were found between cereal varieties as well as between isolates in the wounded assay. Significant differences in lesion lengths (P = 0.014) were also observed between isolates in the unwounded assay. Results from the detached leaf assays suggest that F. langsethiae is a pathogen of wheat and oats and may have developed some host preference towards oats.     

<Emphasis Type="Italic">Botrytis cinerea</Emphasis> induces senescence and is inhibited by autoregulated expression of the <Emphasis Type="Italic">IPT</Emphasis> gene

Botrytis cinerea is a non-specific, necrotrophic pathogen that attacks many plant species, including Arabidopsis and tomato. Since senescing leaves are particularly susceptible to infection by B. cinerea, we hypothesized that the fungus might induce senescence as part of its mode of action and that delaying leaf senescence might reduce the severity of B. cinerea infections. To examine these hypotheses, we followed the expression of Arabidopsis SAG12, a senescence-specific gene, upon infection with B. cinerea. Expression of SAG12 is induced by B. cinerea infection, indicating that B. cinerea induces senescence. The promoter of SAG12, as well as that of a second Arabidopsis senescence-associated gene, SAG13, whose expression is not specific to senescence, were previously analyzed in tomato plants and were found to be expressed in a similar manner in the two species. These promoters were previously used in tomato plants to drive the expression of isopentenyl transferase (IPT) from Agrobacterium to suppress leaf senescence (Swartzberg et al. in Plant Biology 8:579–586, 2006). In this study, we examined the expression of these promoters following infection of tomato plants with B. cinerea. Both promoters exhibit high expression levels upon B. cinerea infection of non-senescing leaves of tomato plants, supporting our conclusion that B. cinerea induces senescence as part of its mode of action. In contrast to B. cinerea, Trichoderma harzianum T39, a saprophytic fungus that is used as a biocontrol agent against B. cinerea, induces expression of SAG13 only. Expression of IPT, under the control of the SAG12 and SAG13 promoters in response to infection with B. cinerea resulted in suppression of B. cinerea-induced disease symptoms, substantiating our prediction that delaying leaf senescence might reduce susceptibility to B. cinerea. Contribution from the Agriculture Research Organization, The Volcani Center, Bet Dagan, Israel, No. 127/2006 series.     

<Emphasis Type="Italic">Eremothecium coryli</Emphasis> and <Emphasis Type="Italic">E.</Emphasis><Emphasis Type="Italic">ashbyi</Emphasis> cause yeast spot of azuki bean

Yeast-like fungi were isolated from lesions on azuki bean (cv. Shin-Kyotodainagon) seeds that had been sucked by bean bugs in Kyoto Prefecture, Japan. On the basis of morphological and physiological characteristics and sequence data of the internal transcribed spacer (ITS) regions including the 5.8S rDNA, these yeasts were identified as Eremothecium coryli and E. ashbyi. Pathogenicity of those yeasts was confirmed by a reinoculation test. To our knowledge, this is the first report of the occurrence of yeast spot in azuki bean in Japan. The nucleotide sequence data reported are available in the GeneBank/EMBL/DDBJ database as accessions AB478291–AB478309 for E. coryli AZC1–19 and AB478310–AB478317 for E. ashbyi AZA1–8.     

Pathogenicity and reproductive fitness of <Emphasis Type="Italic">Pratylenchus coffeae</Emphasis> and <Emphasis Type="Italic">Radopholus arabocoffeae</Emphasis> on Arabica coffee seedlings (<Emphasis Type="Italic">Coffea arabica</Emphasis> cv. Catimor) in Vietnam

The pathogenicity and reproductive fitness of Pratylenchus coffeae and Radopholus arabocoffeae from Vietnam on coffee (Coffea arabica) seedlings cv. Catimor were evaluated in greenhouse experiments. The effect of initial population densities (Pi = 0, 1, 2, 4, 8, 16, 32, 64, 128, and 256 nematodes per cm³ soil) was studied for both species at different days after inoculation (dai). The data were adjusted to the Seinhorst damage model Y = m + (1-m).z^Pi-T. Tolerance limit (T) for P. coffeae was zero for the height and the diameter of the coffee plants. For the diameter, the T-value for R. arabocoffeae was 25.6 for 30 and 60 dai and 12.8 for 90 and 120 dai. After 4 months T was zero. The low tolerance limits indicate that Arabica coffee is highly intolerant to both nematode species. At the end of the experiment (180 dai), all plants were infected and most were dead when inoculated with R. arabocoffeae at initial densities of 32, 64, 128 and 256 nematodes/cm³ soil. For P. coffeae plant death was already observed at the lowest inoculation densities. Growth of coffee was reduced at all inoculation levels for both species. Pratylenchus coffeae and R. arabocoffeae caused intense darkening of the roots, leaf chlorosis and a strong reduction of root and shoot growth. It was observed that P. coffeae mainly destroyed lateral roots rather than tap roots, whereas R. arabocoffeae reduced tap root length rather than the lateral roots. At the lowest inoculum densities, the reproduction factor of P. coffeae was 2.38 and 2.01 for R. arabocoffeae, indicating that arabica coffee is a host for both species. Plant growth as expressed by shoot height and shoot and root weight measured 60 dai was negatively correlated with nematode (both species) density as expressed by the geometric mean of nematode numbers at 30 and 60 dai.