bluuebunny/crossref_metadata_2025 huggingface dataset:
Infection of flowers and fruits of red raspberry by Botrytis cinerea
Authors: DASHWOOD E. P. , FOX R. A.
Published: April 2007

The frequency and site of symptomless infection of flower buds, flowers, and fruits of red raspberry by Botrytis cinerea was studied using surface‐disinfestation and culture techniques. Flower buds were rarely infected but open flowers were rapidly colonized and necrotic stamens and styles were an important source of infection for the developing fruit. The receptacle tissue within the drupelet cluster cavity was mostly sterile. Dichlofluanid sprays reduced symptomless infection of fruits and were more effective when applied early. Post‐harvest rot tests indicated that incidence of grey mould was not related to symptomless infection unless fruits were surface‐disinfested before subjecting to the rotting test.
Cytospora oleina causing canker and dieback of olive in Greece
Authors: RUMBOS I. C.
Published: April 2007

Cytospora oleina was isolated from dead twigs of olive associated with old cankers in the Mount Pelion region of central Greece. Inoculation of young trees with pure cultures of the fungus caused twig death in olive, especially when applied in autumn, and xylem discoloration in apple, plum, cherry, peach and apricot.
The natural occurrence of white clover mosaic virus in sweet pea (Lathyrus odoratus) in south‐east England
Authors: BROWN JACQUELINE D. , BRUNT A. A.
Published: April 2007

White clover mosaic virus was isolated from glasshouse‐grown sweet pea plants with conspicuous flower ‘break’ symptoms. Plant growth was severely affected. The virus was transmissible by sap inoculation to sweet pea and other leguminous species. It was found naturally in Trifolium repens growing nearby. No natural vector is known.
Leaf spot of St Augustine grass (Stenotaphrum secundatum) caused by Cochliobolus bicolor
Authors: MUCHOVEJ J. J.
Published: April 2007

TheBipolarisstate ofCochliobolus bicolorwas shown by isolation and inoculation to be the cause of a leaf spot of St Augustine grass in Viçosa, Minas Gerais, Brazil. Leaf spotting was much more frequent when the grass was in a mixed stand with Kikuyu grass(Pennisetum clandestinum).
The geographical distribution of sunflower diseases in China
Authors: LIU L. , LI X.
Published: April 2007

In various areas of China, the fourth largest sunflower‐producing country in the world, 25 sunflower diseases have been reported: 19 caused by fungi, one virus disease and five caused by different species of broomrape. Their geographical distribution and economic significance are discussed. Fungi are the most prevalent disease causing agents in every region. More species of broomrape have been recorded in China than in any other country in the world. Orobanche coerulescens has not previously been reported to attack sunflower but is an important cause of disease in China. The number of diseases recorded differs among the regions, with 14 in North‐east China, 11 each in North, North‐west and South‐west China, 10 in East China and six in Central and South China. This distribution broadly corresponds to the intensity of sunflower production. Only Puccinia helianthi and Septoria helianthi are reported in all the regions; 64% of the diseases are restricted to one or two regions. Alternaria helianthi, Septoria helianthi, Sclerotinia sclerotiorum and Orobanche coerulescens are considered to be the most important, causing 10‐50% losses in yield, and even crop failure in some areas in some years. Much work remains to be done on disease control to promote the development of sunflower production in China.
Pasture ecology of barley yellow dwarf viruses at Sandford, Tasmania
Authors: GUY P. L.
Published: April 2007

Samples of cocksfoot (Dactylis glomerata), fescue (Festuca arundinacea), phalaris (Phalaris aquatica) and ryegrass (Lolium perenne) were collected every 4‐6 weeks for 2.5 years from two sets of replicated plots, one on a heavy soil and the other on a light soil 200 m away. Rhopalosiphum padi was the predominant aphid species; it was more frequent at the heavy soil site. Sitobion fragariae and Metopolophium dirhodum occurred infrequently during the last 12 months of the survey.

Only PAV (57%), RPV (26%) and mixed infections (17%) of these barley yellow dwarf viruses were detected in the 4100 tillers sampled. Virus incidence increased over the sampling period and was consistently higher at the heavy soil site. RPV only became frequent during the last 12 months.

Virus incidence was higher in fescue (21%) and ryegrass (27%), in which PAV predominated, than in cocksfoot (6%) and phalaris (7%), in which RPV finally predominated.
Competition between metalaxyl‐sensitive and metalaxyl‐resistant isolates of Phytophthora infestans in the absence of metalaxyl
Authors: KADISH D. , COHEN Y.
Published: April 2007

Three metalaxyl‐sensitive (MS, wild type) and three metalaxyl‐resistant (MR) field isolates of Phytophthora infestans were compared, in the absence of metalaxyl, for non‐competitive and competitive fitness on potato leaf and tuber tissues. When inoculated singly onto intact plants MR isolates produced larger lesions in leaflets than MS isolates, but no significant differences were recorded in infection frequency or sporulation capacity. When mixtures of MS and MR isolates were inoculated onto intact plants, all MR isolates exhibited a strong competitive ability: their proportion increased in the sporangial populations from 10 to 100% after eight to 10 sporulation cycles. In contrast, when mixtures were inoculated onto detached leaflets or tuber slices in a moisture‐saturated atmosphere, only MR2 was a strong competitor; MR1 was a weak and MR3 a moderate competitor. The results showed that in intact plants all MR isolates were able to compete successfully with their MS partner isolates, because of the larger lesions they produced and the unlimited availability of host tissue. However, in detached tissues only MR2 was able to compete successfully with MS2, because of its higher infection and sporulation capabilities compared to MS2. The results explain the severe MR‐induced late blight epidemics in potato crops in Israel.
Opine utilization by Spanish isolates of Agrobacterium tumefaciens
Authors: LÓPEZ M. M. , GORRIS M. T. , MONTOJO A. M.
Published: April 2007

Among 115 Spanish isolates of Agrobacterium tumefaciens from 13 hosts and 47 locations, biotypes 1, 2, and 3 were identified. Most isolates were of biotype 2. Biotype 3 isolates were obtained only from grapevine, and all were resistant to agrocin 84. Nopaline was utilized by 84% of isolates. Only three isolates did not utilize either octopine, nopaline or mannopinic acid.

Isolates from fruit trees were mostly biotype 2 and utilized only nopaline; some isolates from a peach x almond hybrid utilized mannopinic acid. Rose and osier isolates were biotype 1 and utilized only nopaline. Most grapevine isolates were biotype 3, but varied widely in opine utilization.

With one exception all isolates sensitive to agrocin 84 catabolized nopaline; no biotype 3 strains catabolized mannopinic acid and no biotype 1 or 2 strains catabolized octopine.
Peronosclerospora maydis found on maize, sweetcorn and plume sorghum in Far North Queensland
Authors: RAMSEY M. D. , JONES D. R.
Published: April 2007

Symptoms of a downy mildew disease were recognized on maize growing in the Atherton Tableland and Lakeland Downs areas of Far North Queensland in 1985. Quarantine measures were invoked to prevent the spread of this potentially serious disease to other parts of Australia.

The pathogen was identified as Peronosclerospora maydis in 1986 following examination of conidiophores with conidia and host range studies. An alternative host was strongly suspected and a survey near fields where the disease had been prevalent led to the identification of P. maydis on Sorghum plumosum, a grass indigenous to northern Australia. All downy mildew outbreaks on maize and sweetcorn in northern Australia since 1970 have been in areas where S. plumosum occurs. It seems likely that P. maydis has been present in Australia for many years.
Cuneiform blight‐a new bacterial disease of Tanier spinach
Authors: ROMEIRO R. S. , SOUZA R. M. , MUCHOVEJ J. J. , FRIGO P. J. G. , KIMURA O.
Published: April 2007

Tanier spinach (Xanthosoma brasiliense, Araceae) is a common leafy vegetable in south‐eastern Brazil. A cuneiform leaf blight which started at the edges of leaves and resulted in complete leaf decay has recently been observed. The causal agent was identified as Pseudomonas cichorii. This appears to be the first report of the disease.
Diaporthe perniciosa associated with plum dieback
Authors: HARRIS D. C.
Published: April 2007

An outbreak of dieback on plum trees at the Institute of Horticultural Research, East Mailing, in the summer of 1983 resembled a disease prevalent in Britain earlier this century attributed to Diaporthe perniciosa. Numerous isolates of this fungus were obtained from diseased tissues but an attempt to reproduce the disease by inoculation was unsuccessful. Dieback appeared following exceptionally wet spring weather.
Studies on the inheritance of resistance to metalaxyl in Phytophthora infestans
Authors: SHATTOCK R. C.
Published: April 2007

Single‐oospore progeny from matings between field isolates of Phytophthora infestans either highly resistant or sensitive to metalaxyl were analysed for fungicide sensitivity in vitro, mating type and, in some cases, allozyme variation at the locus for glucosephosphate isomerase (GPI‐1.) In each cross the majority of first‐generation (F1) progeny showed intermediate sensitivity to metalaxyl. Frequency distributions were skewed towards sensitivity and a few progeny were either wholly sensitive or resistant phenotypes. Allozyme analysis of F1 progeny from a cross between parents of Dutch and Mexican origin showed that c. 10% were selfs of both parents and of parental phenotype for metalaxyl sensitivity. The selfs of the A2 but not the Al parent segregated for mating type. Two backcross generations to the metalaxyl‐resistant Dutch parent gave unexpected phenotypic frequency distributions and aberrant ratios for genotypes at the GPI‐I locus.

Progeny of another backcross between an F1 isolate of intermediate sensitivity and its sensitive Egyptian parent gave a 1:1 ratio for sensitive: intermediate phenotypes. F2 progeny from a related sibmating between intermediate phenotypes segregated in a ratio close to 1:2:1 for sensitive: intermediate: resistant phenotypes. Segregation was also observed among sexual progeny of an intermediate self‐fertile isolate from the backcross generation but not among progeny of a resistant self‐fertile phenotype. Mating type segregated in both cases.

These data are consistent with resistance to metalaxyl in P. infestans being governed by a single nuclear locus exhibiting incomplete dominance. This hypothesis is discussed in relation to the incidence of resistance to metalaxyl in natural populations of P. infestans.
The effect of sunlight on symptom expression of Alternaria alternata on cotton
Authors: ROTEM J. , WENDT U. , KRANZ J.
Published: April 2007

Exposure of naturally infected or inoculated cotton plants (Gossypium hirsutum cv. Acala) to sunlight greatly increased the expression of Alternaria alternata symptoms. Exposure for 8 h was sufficient to produce the effect, which occurred in plants of different age and under a range of conditions of temperature and wetness. The latter included marginal but recurrent dew periods interrupted by dryness by day. The effect of sunlight was also evident in G. barbadense (cv. Pima). Symptomless infections were detected in apparently healthy tissue of inoculated plants and were more frequent in those not exposed to sunlight. It is postulated that sunlight triggers the development of symptomless infections into visible lesions.
Relative effects of Alternaria alternata and A. macrospora on cotton crops in Israel
Authors: ROTEM J. , EIDT J. , WENDT U. , KRANZ J.
Published: April 2007

In large commercial fields, the ratio of Alternaria macrospora to A. alternata lesions was 1:0‐4 in cv. Pima and 1:19 in cv. Acala. The frequency of A. alternata on Pima and of A. macrospora on Acala increased in an experimental field with mixed Pima and Acala plots. In both cultivars disease was inhibited by fungicidal treatment and by removal of flowers. For all parameters measured (leaf area, number of leaves, flowers and bolls, and yield), the responses to treatments were greater in Pima than in Acala.
Development of ELISA for Ophiostoma ulmi using antigen‐coated wells
Authors: DEWEY F. M. , BRASIER C. M.
Published: April 2007

A simple sensitive ELISA test has been developed that detects either antibodies to, or antigens of, the Dutch elm pathogen, Opiostoma (Ceratocystis) ulmi. The dilution end point for antisera raised in mice againt mycelial antigens was 10‐4. The minimum amount of antigen detected in wells passively coated with antigens solubilized in phosphate‐buffered saline was 500 pg/ml. The assay proved an effective method for rapidly screening large numbers of hybridoma supernatants for monoclonal antibodies that recognize O. ulmi antigens and it has also been used to detect fungal antigens in saline extracts of diseased tissue. Non‐specific binding of preimmune antiserum to plant extracts was markedly higher in extracts from diseased than non‐diseased tissue. Production by the diseased host or by the pathogen in vivo of a protein A or lectin‐like molecule that binds non‐specifically to immunoglobulins is postulated.
Effects of growth stage, leaf position and temperature on adult‐plant resistance of wheat infected by Puccinia recondita f.sp. tritici
Authors: PRETORIUS Z. A. , RIJKENBERG F. H. J. , WILCOXSON R. D.
Published: April 2007

Growth stage, leaf position and temperature effects on components of resistance to Puccinia recondita f.sp. tritici in wheat (Triticum aestivum) were studied. Inoculation of Era, Glenlea, Sinton and RL6044 plants at five growth stages showed that latent period increased and uredinium numbers decreased as each adult‐plant‐resistant wheat matured. Growth stage had little effect on latent period in the susceptible cultivar Morocco. No significant differences in latent period determined on the flag, flag ‐1 and flag ‐2 leaves of the same plant were observed for Era, Glenlea and RL6044. However, leaf age should be considered in assessing adult‐plant resistance because the latent period of P. recondita f.sp. tritici in flag leaves of Sinton was shorter than that determined for the flag‐1 and flag ‐2 leaves. Fewer uredinia developed on the flag ‐2 leaf of Glenlea than on the flag leaf. The latent period of leaf rust in Era, Glenlea, RL6044 and Morocco was significantly longer at 15°C than at 21°C, but temperature did not affect Sinton to the same degree. Uredinium size was a sensitive criterion of adult‐plant resistance. Uredinium development in line RL6044 was significantly restricted at 15°C, but uredinia on Era, Glenlea and Sinton at 15°C were as large as those at 21°C. On the susceptible Morocco uredinia were larger at 15°C than at 21°C.
Variation in the pine stem rust fungus Peridermium pini in the United Kingdom
Authors: GIBBS J. N. , ENGLAND N. , WOLSTENHOLME R.
Published: April 2007

Peridermium pini aeciospores from lesions on Scots pine (Pinus sylvestris) in Scotland and in Thetford Forest, East Anglia, differed in terms of germ tube morphology and cytology. The former produced long aseptate germ tubes containing a pair of nuclei. The latter produced short septate germ tubes, each cell containing a single nucleus. One third of the ‘Scottish’ germ tubes ended in a vesicle. Nuclei could be counted in only a small proportion of ungerminated aeciospores. On average 83% of Scottish spores had two nuclei and 4% had one. The equivalent figures for Thetford spores were 66 and 20%. A small number of aeciospore samples from other parts of England resembled Scottish spores rather than Thetford spores in germ tube morphology and cytology.

Both Scottish and Thetford spores proved capable of causing infection of wounded Scots pine shoots. In addition, some Thetford spores caused infection on leaf discs taken from certain Paeonia cultivars. From these results it is concluded that two distinct forms of Peridermium pini exist in the UK. The implications of this finding are discussed in relation to the history of pine stem rust in the country and the genetics and taxonomy of P. pini.
The genetic analysis of resistance to fusarium crown and root rot of tomato
Authors: VAKALOUNAKIS D. J.
Published: April 2007

The tomato line IRB‐301‐31, resistant to fusarium crown and root rot (Fusarium oxysporum f.sp. radicis‐lycopersici) was crossed with two susceptible cultivars, Motelle and Earlypak No. 7. When F1, F2 and backcross progenies were inoculated at the one‐leaf stage with a suspension of spores of the pathogen, all could be classified as either resistant (healthy) or susceptible (dead). The ratios of resistant to susceptible plants indicated that resistance was conferred by a single dominant gene, designated Fr1.
Characterization of maize streak virus: description of strains; symptoms
Authors: PINNER M. S. , MARKHAM P. G. , MARKHAM R. H. , DEKKER L.
Published: April 2007

Twenty‐four isolates of maize streak virus (MSV) derived from maize, sugarcane and grasses were compared to a maize isolate of the virus (M(N)M) from Nigeria, using symptoms, gel diffusion and ELISA. Fourteen isolates were identified as maize strains, eight other isolates were serologically related to M(N)M but were distinct. In most cases the maize strain could be identified by the symptoms in Zea mays cv. Golden Bantam but symptom expression in grasses was not always sufficient to identify the economically important maize strain. In general, however, symptoms were similar in both grass and maize hosts. Identification by symptoms alone was further complicated by the possibility that some isolates were mixtures. There was no evidence that adaptation to grass hosts occurred, as all isolates could be transmitted to maize. It was not possible to transmit certain strains to the host species from which they were derived, even though they were transmissible to other hosts. This was assumed to be related to vector feeding behaviour. Insect toxin was responsible for certain stunting symptoms, leaf curling and vein enations often associated with MSV.
Inheritance of rust resistance in Macroptilium atropurpureum
Authors: BRAY R. A.
Published: April 2007

Sixteen accessions of Macroptilium atropurpureum showed a range of reaction types when seedlings were inoculated with a single‐urediniospore isolate of Uromyces appendiculatus (rust). Analysis of F2 families of crosses with the susceptible cv. Siratro showed that in seven accessions resistance was dominant, regulated by a single locus in four of these but by more than one locus in the three others. At least three of these loci were identified as non‐allelic. In one accession resistance was near‐recessive and regulated at a single locus, while combinations of dominant and recessive alleles at different loci explained the segregation of resistance in other accessions. Loci with partial dominance and expressivity varying with environment were also observed. There was some evidence that the expression of resistance could be temperature sensitive and that the fungus exhibited differential virulence.
Negative cross resistance between benzimidazole and N‐phenylcarbamate fungicides and control of Botrytis cinerea on grapes
Authors: ELAD YIGAL , SHABI EZRA , KATAN TALMA
Published: April 2007

Isolates of Botrytis cinerea resistant to benzimidazoles (BenR), dicarboximides (DicR), or both (BenR DicR) were found on table grapes in vineyards in Israel. In vineyards treated for one or two seasons with benomyl and dicarboximides, 41% of the isolates were benomyl‐resistant, 18% were dicarboximide‐resistant and 21 % were resistant to both fungicides. The frequency of resistant strains was very low in non‐treated vineyards. Negatively correlated cross resistance (NCCR) was manifested by 46 BenR isolates which were sensitive to isopropyl N‐(3,4‐diethoxyphenyl) carbamate (NPC) and 73 benomyl‐sensitive (Bens) isolates which were insensitive to NPC; NCCR was not influenced by sensitivity to dicarboximides. A mixture of Bens DicR plus BenR Dics isolates, inoculated on rose petals, was inhibited by mixtures of benzimidazoles plus NPC but not by benomyl, NPC or iprodione alone. Grey mould, incited on maturing grape berries by a vineyard population composed of Bens and BenR strains, was not controlled by benomyl, while the mixture of NPC plus carbendazim was effective.
Identification of oat‐adapted isolates of cereal Septoria in the UK using a detached leaf technique
Authors: JOHNSTON H. W. , SCOTT P. R.
Published: April 2007

Isolates of Septoria spp. from cereals were tested for their relative pathogenicity to detached seedling leaves of three cereal species. Each of 23 isolates showed unequivocal adaptation to either oats, or wheat, or barley. Five oat‐adapted isolates were from Prince Edward Island, Canada, where S. avenue is prevalent on oats; three were from the UK, where there are few oat crops and where adaptation to oats has not been reported.

Oat‐adapted isolates tended to have pycnidiospores of above‐average length and could be referred to S. avenae. Wheat‐adapted and most barley‐adapted isolates had shorter spores and could be referred to S. nodorum. UV‐fluorescent pigment was produced on oxgall agar by all wheat‐adapted isolates, but only by a minority of oat‐adapted and barley‐adapted isolates.

It is suggested that adaptation to cereal species is a more useful character than spore length for classifying isolates.
Effect of yellow rust on yield components of winter wheat in China
Authors: YANG X. B. , ZENG S. M.
Published: April 2007

Experiments were done in 1983,1984 and 1985 in Beijing and Zhengzhou, People's Republic of China, to determine the relationship of yield components of wheat to the severity of yellow rust (Puccinia striiformis f.sp. tritici). Epidemics were manipulated by timing inoculation and fungicide applications. Disease, plant yield, number of ears per plant, number of grains per ear and 1000‐grain weight were measured. Analysis indicated that there were interactions among the yield components. However, path coefficient analysis did not detect any statistically significant compensation and showed that there was a positive correlation among yield components. The correlation coefficients between AUDPC (area under disease progress curve, accumulated to each growth stage) and each yield component increased gradually with growth stage, thus providing no evidence of a critical stage at which a yield component was most affected by disease.
Monoclonal antibodies to specific components of the Dutch elm disease pathogen Ophiostoma ulmi
Authors: DEWEY F. M. , MUNDAY C. J. , BRASIER C. M.
Published: April 2007

The potential of polyclonal antisera and monoclonal antibodies to differentiate the EAN and NAN aggressive subgroups of Ophiostoma ulmi was explored. Polyclonal antisera, when tested by ELISA, cross‐reacted widely with unrelated species and failed to distinguish between the two aggressive subgroups but small quantitative differences were found, particularly between antigens secreted overnight, by EAN and NAN germlings. Monoclonal antibodies were raised in mice against mycelial homogenates. From two fusions, 33 cell lines were raised that secreted antibodies positive for O. ulmi. Approximately one third were non‐specific; 11 were specific either to species or subspecies. Two cell lines differentiated mycelial antigens of the aggressive isolates of O. ulmi from those of the non‐aggressive subgroup, but not antigens from surface washings. Only quantitative differences were detected between the EAN and NAN aggressive subgroups. Almost all the monoclonal antibodies and antiserum recognized antigens present in surface washings of cultures on solid medium, in cell‐free extracts of mycelial homogenates, in cell‐free culture fluids, and in substances secreted overnight by germinating spores. Specific detection of such molecules promises to provide a highly sensitive mechanism for studying early pathogen/host plant interactions. Most of the monoclonal antibodies appeared to have potential diagnostic value; they gave readings twofold to tenfold higher with extracts from diseased than from healthy tissue. However, one cell line that secreted antibodies specific to O. ulmi cross‐reacted strongly with extracts of healthy tissue.
Airborne inoculum as a major source of Septoria tritici (Mycosphaerella graminicola) infections in winter wheat crops in the UK
Authors: SHAW M. W. , ROYLE D. J.
Published: April 2007

The pattern and extent of primary infection by Septoria tritici were compared over a period of 3 years in winter wheat grown at sites with differing histories and from seed stocks obtained in different countries, in the open, under airtight cover and in sterilized soil. Only the airtight cover altered the number of lesions found, substantially reducing it. Lesions were evenly distributed. Lesions were found throughout the autumn and occasionally in the winter and spring on wheat seedlings exposed in trays to the open air for periods of 1 week, then given good conditions for infection to occur. This was true even at a site 0.4 km distant from wheat residues. The results show that the main source of primary infection of winter wheat in these experiments was evenly dispersed and airborne. It probably consisted mainly of ascospores of Mycosphaerella graminicola.
Vertical dispersal of plant pathogens by splashing. Part II: experimental study of the relationship between raindrop size and the maximum splash height
Authors: WALKLATE P. J. , McCARTNEY H. A. , FITT B. D. L.
Published: April 2007

This paper describes a simple experimental test of the theoretical relationship between raindrop diameter and maximum splash height proposed by Walklate (1989). This relationship contains two empirical parameters to model the characteristics of a splash target that limits upward movement of splash droplets. These parameters are estimated by fitting the proposed relationship to measurements of the maximum height of splashing from a variety of targets including leaves, straw and water films on horizontal plane surfaces. The experimental technique provides a simple and meaningful way to characterize the behaviour of splashing from plant material. This information can be applied to describe the upward movement of inoculum in crop canopies during rainfall.
Somatic recombination in Rhynchosporium secalis
Authors: NEWTON A. C.
Published: April 2007

Drug‐resistant mutants were induced in strains of Rhynchosporium secalis. Two mutants resistant to hygromycin‐B and 5‐fluorouracil, respectively, were stable and easily selected in culture. Mixtures of the two mutants failed to yield any recombinants, whether under selection pressure or not, on agar and on barley leaves. After protoplast production and fusion, followed by selection on media containing both drugs, two recombinants were isolated. Single‐spore derivatives expressed the drug resistances of both parental strains.
Two new species of Bipolaris
Authors: SISTERNA MARINA N.
Published: April 2007

Two new fungal species, Bipolaris secalis, isolated from rye seed, and B. triticalis, isolated from triticale seed, arc described and shown to reduce germination of rye seed.
Rhizomania disease of sugar beet in England
Authors: HILL S. A. , TORRANCE L.
Published: April 2007

Rhizomania disease was first detected in the UK in 1987, in a single crop in Suffolk. Affected plants had pale leaves, often upright, narrow and rolled; roots were small, often with constrictions, warty outgrowths, proliferation of fibrous roots, and vascular staining. Disease occurred in strips at right angles to one another, parallel with directions of cultivation, suggesting that the previous beet crop had also been infected. Beet necrotic yellow vein virus was detected by ELISA, by electron microscopy, and by transmission to indicator species. It was sometimes associated with beet soil‐borne virus. The affected crop was destroyed with herbicide. No other outbreaks were detected in subsequent surveys of crops in 1987.
The relationship between Alternaria leaf spot and potassium deficiency causing premature defoliation of cotton
Authors: HILLOCKS R. J. , CHINODYA R.
Published: April 2007

Investigations into the relative roles of Alternaria leaf spot and potassium deficiency in causing premature defoliation of cotton showed that severe leaf spotting developed only on plants already showing deficiency symptoms. Defoliation was delayed or reduced by either the application of potassium fertilizer or by fungicide sprays, but significant yield increases required both fertilizer and fungicide. Removal of flowers also prevented the development of deficiency symptoms and prevented the leaf spot disease. Differences between cultivars in susceptibility to the disease were linked to their sensitivity to low levels of available potassium.
Resistance to organomercury in Pyrenophora graminea
Authors: JONES D. R. , SLADE M. D. , BIRKS KATHRYN A.
Published: April 2007

Isolates of Pyrenophora graminea resistant to organomercury were obtained from barley crops in England and Scotland in 1984–6. Resistant isolates were approximately 100 times less sensitive in vitro than sensitive isolates to phenyl mercuric acetate (PMA), but the difference was only four times for methoxyethyl mercuric acetate (MEMA). In small‐plot field trials, seed treatment with either PMA or MEMA gave good control of leaf stripe disease caused by organomercury‐sensitive strains of P. graminea but neither compound gave commercially acceptable control of resistant strains. Fungicides with different modes of action (triadimenol + fuberidazole, flutriafol + ethirimol + thiabendazole, carboxin‐+‐ thiabendazole + imazalil, and guazatine + imazalil) were effective against organomercury‐sensitive and organomercury‐resistant strains. The few cases of resistance found do not justify a change from the use of organomercury as the standard seed treatment for barley.
Parietaria mottle virus, a possible new ilarvirus from Parietaria officinalis (Urticaceae)
Authors: CACIAGLI P. , BOCCARDO G. , LOVISOLO O.
Published: April 2007

A previously undescribed virus, probably a new member of the ilarvirus group, was isolated from Parietaria officinalis showing symptoms of yellow mosaic or mottling. This virus, for which the name parietaria mottle virus (ParMV) is proposed, differs in host range from other ilarviruses. ParMV was purified from Chenopodium quinoa by sap clarification with chloroform, and differential and sucrose density gradient centrifugation.

Purified particles were quasi‐isometric to ovoid with diameters of about 24, 29 and 36 nm; no bacilliform particles were detected. Buoyant density in caesium chloride, determined on glutaraldehyde‐fixed virus, was 1.35 g/cm3.

An antiserum to ParMV was obtained with a titre of 1:32 in agar gel double‐diffusion tests. ParMV did not react with eight other viruses or virus strains belonging to the ilarvirus group or to pelargonium zonate spot virus.

Polyacrylamide gel electrophoresis indicated that ParMV contains a single major protein species of estimated molecular weight 24300 Da and four RNA species of estimated molecular weight 1 37, 1.19, 0.86 and 0.36 × 106 Da.
Unusual or interesting records of plant pathogenic Oomycetes
Authors: HALL G.
Published: April 2007

The following records from the UK are discussed: Peronospora grisea on Hebe gauntlettii (forming oospores), H. elliptica x pimelioides cv. Carl Teschner and H. hulkeana; Peronospora fragariae on Potentilla recta; Peronospora hariotii on Buddleia davidii cv. Pink Delight and B. globosa; Pythium tracheiphilum on Lactuca sativa. The following records from other countries are discussed: Phytophthora erythroseptica var. erythroseptica on Cymbidium sp. in Western Australia; Phytophthora palmivora on Zizyphus jujuba in Taiwan (a new record on this host); Plasmopara halstedii on Arctotis sp. in New Zealand (a new record of this species for Australasia).
A new disease of sorrel (Hibiscus sabdariffa var. sabdariffa) caused by Coniella musaiaensis var. hibisci from Trinidad and Tobago
Authors: PERSAD C. , FORTUNE M.
Published: April 2007

A serious leaf spot and stem canker observed on Hibiscus sabdariffa var. sabdariffa is reported for the first time from Trinidad and Tobago. Symptoms are described and the pathogen is identified as Coniella musaiaensis Sutton var. hibisci.
Expression of adult plant resistance and its effect on the development of Puccinia striiformis f.sp. tritici in some Australian wheat cultivars
Authors: PARK R. F. , REES R. G.
Published: April 2007

The onset of adult plant resistance (APR) to Puccinia striiformis was examined in seven Australian wheat cultivars under field conditions and in 14 cultivars under controlled environmental conditions. In most cultivars under field conditions the percentage leaf area affected by stripe rust at mid‐tillering (GS 22–26; third leaf) was significantly less (P < 0.05) than on the more susceptible cultivar Teal. The expression of APR was more conspicuous during tillering to node formation; at these growth stages chlorosis and/or necrosis developed in association with rust colonies on the most resistant cultivars. Under controlled conditions, the primary leaves of all cultivars except Olympic and Flinders displayed some resistance when compared with Teal (lower infection types, longer latent periods and/or less percentage leaf area affected). Studies on the spread of stripe rust from infection foci established in selected cultivars in the field indicated that the resistance detected at early growth stages in Suneca in controlled environmental studies also appeared to be effective in the field.
A revision of the species concept in Sarocladium, the causal agent of sheath‐rot in rice and bamboo blight, based on biochemical and morphometric analyses
Authors: BRIDGE P. D. , HAWKSWORTH D. L. , KAVISHE D. F. , FARNELL P. A.
Published: April 2007

Fifty strains of Sarocladium (11 dried specimens and 39 living cultures) were examined for variation in conidial size, utilization of several carbon sources, hydrolysis of several substrates, esterase isozymes after gel electrophoresis, and secondary metabolites after thin‐layer chromatography. The results showed that there was insufficient justification to maintain the separation of the genus into the two species S. oryzae and S. attenuatum; S. attenuatum is, therefore, considered a synonym of S. oryzae. Strains isolated from outbreaks of bamboo blight in Bangladesh could be distinguished from strains isolated from rice in 12 countries by pigment production in culture; a strain isolated from bamboo leaf‐litter in India was identical to the rice isolates in this respect.
Factors affecting development of Septoria tritici in winter wheat and its effect on yield
Authors: THOMAS M. R. , COOK R. J. , KING J. E
Published: April 2007

Severe infection with Septoria tritici occurred in four of five experiments designed to create a series of different disease epidemics. These experiments successfully identified periods suitable for infection. They also indicated the effect of sprays, timed before and after these periods, on disease development and yield.

Analysis of disease progress and weather records suggested that critical conditions for initial development of S. tritici occurred during early May at four sites. Heavy rain giving at least 10 mm on 1 day or a total of 10 mm or more on 2 or 3 successive days occurred at all four sites prior to the appearance of symptoms on a particular leaf layer, though less heavy rain may suffice to splash inoculum onto upper leaves in shorter, immature canopies where stem elongation is incomplete. At the fifth site, infection occurred later in May and disease failed to develop to a significant degree. At all sites, the length of the incubation period on any of the top three leaves was found to be between 396 and 496 degree days.

Control of winter epidemics of S. tritici had little effect on yield, whereas spray sequences commencing later than growth stage (GS) 31 but immediately prior to the critical periods provided the best disease control and yield benefit. Regression models incorporating, as independent variables, area under the S. tritici disease progress curve for any of the top three leaves from their emergence (GS 32‐37) satisfactorily explained yield loss at the four sites where disease was severe. Consideration of leaf 2 or leaf 3 alone accounted for more than 82% of the variance at each site and a yield loss from infection of leaf 2 related to thermal time is suggested as 0.00265% per C per day from the appearance of symptoms.
Antifungal activity, acid and sugar content in the wood apple (Limonia acidissima) and their relation to fungal development
Authors: ADIKARAM N. K. B , ABHAYAWARDHANE YAMUNA , GUNATILAKA A. A. LESLIE , BANDARA B. M. RATNAYAKE , WIJERATNE E. M. KITHSIRI
Published: April 2007

Unripe wood apple fruit is generally free from visible fungal growth before and at harvest but a succession of fungi appears on the fruit shell, and sometimes in the pulp, during ripening. A TLC‐Cladosporium bioassay of the chloroform extract taken from unripe fruit shell demonstrated three inhibition areas. Similar extracts from stem‐bark and root‐bark produced these three, and one additional, inhibition areas. The four compounds responsible for inhibition were identified as psoralene, xanthotoxin, 2,6‐dimethoxybenzoquinone and osthenol.

Concentrations of the three antifungal compounds on unripe fruit shell increased during the first 4 days after harvest and then declined. They remained much below those required to inhibit the development of three fungi on TLC plates. Titratable acidity of the unripe fruit pulp was high but decreased by about 50% during ripening. Levels of reducing sugars were very low in the unripe fruit pulp but increased by about five times during ripening. Levels also increased in the fruit shell and its washings. The possible role of these factors in restricting fungal growth in unripe fruits is discussed.
A comparison of infection of resistant and susceptible lines of field bean (Vicia faba) by Ascochyta fabae
Authors: PRITCHARD P. R. , ROWE P. S. , ROSSALL S.
Published: April 2007

In a series of growth room experiments, a determinate line of Vicia faba was shown to be more susceptible to infection by Ascochyta fabae than a conventional indeterminate line. On the determinate line, lesions developed more quickly on younger leaves. No evidence of systemic infection was found and disease transfer to the emerging seedling was probably by physical contact with the infected seed testa. Successful establishment of the disease required leaf wetness for periods of 4 h at 20–25° C to 12 h at 10 C. The rate of pycnidiospore germination on leaves decreased with temperature over this range, but did not differ between the determinate and indeterminate lines.
Effect of Gliocladium and Trichoderma on damping‐off and blight of snapbean caused by Sclerotium rolfsii in the greenhouse
Authors: PAPAVIZAS G. C. , LEWIS J. A.
Published: April 2007

Aqueous suspensions of conidia of 285 wild‐type strains and mutants of Gliocladium virens, Trichoderma hamatum, T. harzianum and T. viride were tested against Sclerotium rolfsii in the greenhouse. Ten strains of G. virens and four strains of T. harzianum suppressed damping‐off of snapbean by 30‐50% and blight by 36‐74%. All strains of T. hamatum and T. viride tested as conidia were ineffective. In general, strains of G. virens were more effective in suppressing disease in the greenhouse than strains of T. harzianum. Several strains of G. virens and T. harzianum used alone were equal to or more effective than double and triple mixtures of such strains in disease suppression. Of four formulations of G. virens tested, germlings, alginate‐bran‐fermenter biomass pellets, and Pyrax‐fermenter biomass mixtures reduced disease considerably and all three formulations were more effective than conidia in aqueous suspension. Strain G1‐3 of G. virens added to soil as Pyrax‐fermenter biomass mixtures in amounts to provide colony‐forming units ranging from 1 ‐5 × 103 to 1 ‐2 × 104 per g soil provided statistically significant protection of the host at all concentrations. The extent of biological control with strains G1‐3 and G1‐21 of G. virens also depended on the strain of the pathogen used. Both strains effectively suppressed disease caused by strain Sr‐1 (small sclerotia) of S. rolfsii. They were partially effective against strain Sr‐116 (medium size sclerotia) and ineffective against strain Sr‐3 (large sclerotia). Although strains G1‐3 and G1‐21 colonized the sclerotia of all three strains of S. rolfsii in soil effectively, they only reduced germinability of sclerotia of strain Sr‐1.
A new foliar disease of rubber
Authors: RADZIAH N. Z. , CHEE K. H.
Published: April 2007

Fusicoccum sp. is reported as a pathogen of fully expanded leaves of Hevea brasiliensis in Malaysia. A short description is given. The fungus was isolated and shown to be pathogenic by inoculation of attached leaves and leaf discs under controlled conditions.
Molecular variation in populations of Erysiphe graminis on barley, oats and rye
Authors: O'DELL M. , WOLFE M. S. , FLAVELL R. B. , SIMPSON C. G. , SUMMERS R. W.
Published: April 2007

DNA isolated from the formae speciales of Erysiphe graminis that grow on barley, wheat, rye and oats was studied using restriction endonucleases and DNA/DNA hybridization procedures. DNA fragments were purified by molecular cloning and a few containing repeated sequences were used to demonstrate the many variations in restriction fragments both within and between the fourformae speciales. In an analysis of six single‐colony isolates of the barley mildew pathogen collected from different UK sites in different years, more than a quarter of the fragments scored varied among isolates. One isolate, with an uncommon pathogenicity character, differed from the remainder in the distribution of DNA bands. Isolates of rye mildew were also distinct from one another but isolates of oat mildew from a population of similar size appeared to belong to a single clone.

It is concluded that the chromosomes of E. graminis contain many families of dispersed repeated sequences and that there may be extensive polymorphism for restriction endonuclease cleavage sites associated with these repeats. Such unselected polymorphisms could be useful in helping to understand and discriminate among the factors affecting population structure in the pathogen as it responds to different agricultural practices.
The incidence of barley yellow dwarf virus isolates in perennial ryegrass (Lolium perenne) in south‐western Victoria
Authors: EAGLING D. R. , CUNNINGHAM P. J. , SWARD R. J. , HALLORAN G. M.
Published: April 2007

Barley yellow dwarf virus (BYDV) was detected in perennial ryegrass cultivars examined from three sites in south‐western Victoria (Balmoral, Mininera and Hamilton); the frequency of BYDV infection varied with cultivar. PAV‐related isolates were prevalent at all sites, but the incidence of MAV‐ and RPV‐related isolates varied with the site and cultivar. The PAV‐related isolate was less frequent in cv. Ellett than in cv. Victorian at all sites. The implications for the epidemiology of the disease and its agronomic importance in Victoria are discussed.
Purification, serology and properties of five zucchini yellow mosaic virus isolates
Authors: HUANG C. H. , HSEU S. H. , TSAI J. H.
Published: April 2007

Five zucchini yellow mosaic virus (ZYMV) isolates designated ZYMV‐1, ‐3, ‐5, ‐7 and ‐FL were purified from zucchini plants grown under the same environmental conditions. Isolates were divided into three groups on the basis of yield of purified virus: group one (ZYM V‐5 and ‐7) yielded 18‐24 mg/100 g tissue, group two (ZYMV‐3) 5.0‐5.7 mg/100 g tissue, and group three (ZYMV‐1 and ‐FL) low yields of 0‐5‐1‐5 mg/100 g tissue. The yield of purified virus was positively correlated with the number of local lesions produced by inoculation of Chenopodium amaranticolor with extracts from infected zucchini leaf tissue. No serological differences were exhibited among the isolates in SDS‐immunodiffusion tests. Results of ELISA tests indicated that ZYMV‐FL differed from the other isolates and that antiserum to ZYMV‐7 absorbed with ZYMV‐FL failed to react with ZYMV‐FL but retained some serological activity to ZYMV‐7 and the other three Taiwanese isolates. The relative molecular masses of capsid proteins for the four ZYMV isolates from Taiwan and ZYMV‐FL were similar.
Factors affecting the efficacy of post‐harvest fungicide applications for the control of blue mould (Penicillium expansum) in stored apples
Authors: PENROSE L. J. , KOFFMANN W. , RIDINGS H. I.
Published: April 2007

The effects of apple fruit maturity, temperature of fruit or dip solution, period of time in fungicidal dip, storage conditions, and spore inoculum concentration, on the efficacy of fungicides for control of blue mould (Penicillium expansum) were examined in various experiments.

Iprodione and imazalil were only effective when inoculum concentration was low, whilst prochloraz was highly effective in controlling rot on fruit inoculated with 3 × 106 spores/ml. There was no consistent effect of dip temperature or fruit maturity on the efficacy of the fungicides. Iprodione was more effective on warm fruit (19°C) than cold fruit (6°C) whilst the reverse was true of imazalil. Extended periods of immersion in the fungicides slightly reduced the incidence of rotting but not to any useful degree.

The incidence of rotting in fruit treated with prochloraz and etaconazole was less in fruit stored under controlled‐atmosphere cold storage conditions than in fruit stored in air cold‐storage. Both fungicides were also effective for short‐term storage at 20 C in air. Captan, benomyl, captan plus benomyl or vinclozolin were either ineffective or of poor efficacy under all storage conditions.
Strains of Botrytis cinerea resistant to dicarboximide and benzimidazole fungicides in New Zealand vineyards
Authors: BEEVER R. E. , LARACY E. P. , PAK H. A.
Published: April 2007

In a survey of New Zealand vineyards at harvest 1985, isolates of Botrytis cinerea resistant to benzimidazole and to dicarboximide fungicides were common. The mean frequency of resistance in the major vine‐growing districts ranged from 8 to 41% for benzimidazoles, and from 51 to 59% for dicarboximides. All benzimidazole‐resistant isolates showed high levels of resistance (EC50 greater than 100 mg/l carbendazim based on radial growth response), and all dicarboximide‐resistant isolates showed low levels of resistance. Two subgroups of dicarboximide‐resistant isolates were recognized, distinguished in the first instance by their osmotic response. Low‐level resistant isolates, which formed a dense margin on osmotically amended medium, exhibited an EC50 for mycelial growth on iprodione of c. 3‐2 mg/l; ultra‐low‐level resistant isolates, which formed a fibrillose margin on osmotically amended medium identical to that of sensitive isolates, exhibited an EC50 of c. 1‐3 mg/1. In agar culture, radial growth rate, and conidial and sclerotial production of both subgroups were similar to those of sensitive isolates. Virulence (lesion size) and conidial production on grape berries were highest in sensitive isolates, intermediate in ultra‐low‐level dicarboximide‐resistant isolates, and lowest in low‐level dicarboximide‐resistant isolates. Evidence is presented indicating that ultra‐low‐level dicarboximide‐resistant strains have progressively replaced low‐level dicarboximide‐resistant strains in the vineyard population. The presence of dicarboximide‐resistant strains was linked with a partial loss of fungicide efficacy.