bluuebunny/crossref_metadata_2025 huggingface dataset:
The effectiveness of fungicides used against Claviceps purpurea attacking male‐sterile barley in field trials
Authors: WOOD G. , SMITH J. R. COLEY
Published: February 2008

Sprays of benomyl applied during the flowering period to artificially inoculated barley heads were shown to be effective against ergot disease of male‐sterile barley. Under natural conditions, using germinating ergots as a source of ascospore inoculum, the effectiveness of benomyl was reduced — the reasons for this are discussed. Timing of fungicide application was critical as none of the fungicides tested showed marked eradicant properties. Sprays of benomyl just before and at maximum flower opening were best.
Host range and properties of artichoke yellow ringspot virus
Authors: RANA G. L. , GALLITELLI D. , KYRIAKOPOULOU P. E. , RUSSO M. , MARTELLI G. P.
Published: February 2008

The biological, serological and physico‐chemical properties of one isolate of artichoke yellow ringspot virus (AYRV) from Greece and another from Italy were compared.

Both isolates infected 56 herbaceous species and there were few differences between them in the symptoms they caused.

During purification they behaved identically and both tended to aggregate. Virus particles were isometric and measured c. 30 nm in diameter. In CsCl, virus sedimented as mixed aggregates of empty and full particles with buoyant densities varying from 1.20–1.30 g/ml and from 1.40–1.53 g/ml, respectively.

The coat protein of AYRV contains a single polypeptide of mol. wt 53000 and the genome consists of two species of single‐stranded RNA with mol. wts 2.17 × 106 (RNA‐1) and 1.85 × 106 (RNA‐2) daltons, estimated under denaturing conditions.

The two virus isolates are serologically very closely related but are unrelated to 28 other plant viruses with isometric particles. The characteristics of AYRV suggest that it is a possible member of the nepovirus group.
Groundnut eyespot virus, a new member of the potyvirus group
Authors: Dubern J. , DOLLET M.
Published: February 2008

A virus causing ‘eyespot’ leaf symptoms in groundnut plants was transmitted by sap‐inoculation and by Aphis craccivora in the non‐persistent manner. It infected 16 of 72 species from five of 12 families and was easily propagated in Arachis hypogaea and Physalis floridana. The virus has particles c. 13 × 755 nm and is serologically closely related to soybean mosaic and pepper veinal mottle viruses, and more distantly to four other potyviruses. The virus differs in host range, in vitro properties and serological properties from previously described strains of soybean mosaic and pepper veinal mottle viruses. It seems to be a distinct member of the potyvirus group and we propose the name groundnut eyespot virus.
Host range, purification and some properties of hop mosaic virus
Authors: ADAMS A. N. , BARBARA D. J.
Published: February 2008

Hop mosaic virus (HMV) causes severe symptoms in sensitive hop (Humulus Zupulus) cultivars, but over 90% of hop plants grown in England belong to tolerant cultivars and most of these plants are infected. HMV infected 11 herbaceous species symptomlessly but infection was systemic in only three of these: Nicotiana clevelandii, N. debneyi and Urtica urens. HMV did not infect 33 other species in 13 families. The virus was transmitted in the non‐persistent manner by the aphids Myzus persicae, Macrosiphum euphorbiae and Phorodon humuli. It was not seed‐borne in N. clevelandii, U. wens or hop.

HMV was purified by precipitation from N. clevelandii extracts with polyethylene glycol followed by centrifugation in sucrose density gradients. The preparations contained filamentous particles c. 14 × 650 nm composed of c. 6% single‐stranded RNA of mol. wt c. 3.0 × 106 and a single protein species of mol. wt c. 34 000. HMV showed distant serological relationships to carnation latent, potato M, cowpea mild mosaic and hop latent viruses but it did not react with antisera to six other carlaviruses. The cryptogram for HMV is R/1: 3.0/(6): E/E: S/Ve/Ap.
Variation in the pathogenicity of three viruses of tomato
Authors: FRANCKI R. I. B. , GOULD A. R. , HATTA T.
Published: February 2008

Tomato plants from Queensland with severe necrotic disease symptoms were shown to be co‐infected with a strain of cucumber mosaic virus (CMV), referred to as the 0 strain (OCMV) and alfalfa mosaic virus (AMV) designated as the T strain (TAMV). TAMV alone was responsible for the necrotic reaction in tomato. OCMV and four other strains of the virus, did not acquire satellite RNA or an ability to cause necrosis in tomato by passage through Nicotiana tabacum cv. Xanthi‐nc.

It was observed that ‘fern leaf’ symptoms in tomato, usually ascribed to CMV infection, could also be caused by some strains of tobacco mosaic virus (TMV). On the other hand, the range of symptoms produced by strains of CMV could be confused with those produced by strains of TMV and some other viruses, including tomato mosaic and tomato golden mosaic viruses.
A freeze/thaw technique for estimation of nitrogenase activity in detached nodules of Vigna mungo
Authors: SRIVASTAVA R. C. , MUKERJI D. , MATHUR S. N.
Published: February 2008

Freezing (under inert conditions) of detached root nodules (with active rhizobia) in the presence of 0.05 ml toluene followed by thawing allowed N2‐dependent evolution of ammonia. The activity of the frozen/thawed and toluene‐treated nodules was affected similarly to that expected of nitrogenase by various known effectors of the enzyme. This freezehhaw technique thus offers an alternative method for estimation of nitrogenase activity in whole nodule preparations.
The effects of barley yellow dwarf virus and powdery mildew in oats and barley with single and dual infections
Authors: POTTER L. R.
Published: February 2008

Prior infection by barley yellow dwarf virus (BYDV) initially suppressed, then subsequently enhanced the amount of powdery mildew (Erysiphe graminis DC ex Mérat) on oat cv. Maldwyn and barley cv. Proctor. Carbendazim applied as a spray decreased mildew on virus‐free and BYDV‐infected plants, but had no effect on virus symptoms. In oats, both mildew and BYDV infection significantly increased the number of heads but decreased the number of grains per head. Mildew infection of BYDV‐infected plants had no further effect. BYDV significantly increased the 1000 grain weight of oats, but mildew caused no significant alteration in grain weights of either virus‐free or BYDV‐infected plants. Both mildew and BYDV reduced the yield of oats, but mildew infection of BYDV‐infected plants caused no further significant alteration. Percentage crude protein was increased in grain from both BYDV‐infected and mildew‐infected oats, but significantly only in BYDV‐infected plants.

In barley, the number of spikelets on the main shoot, the number of heads and the number of grains per head were all significantly reduced by BYDV but not by mildew. Mildew infection of BYDV‐infected plants had no further effect. Both BYDV and mildew significantly reduced the 1000 grain weight of barley, but mildew infection of BYDV‐infected plants caused a significant increase in 1000 grain weight compared to mildew‐free, virus‐infected plants. The yield of barley was significantly reduced by mildew and by BYDV, but no additional yield loss was caused by mildew infection of BYDV‐infected plants. The percentage crude protein of barley was increased, but not significantly, by mildew and by BYDV.
Effects of controlled epidemics of powdery mildew on grain yield of spring barley
Authors: SCOTT S. W. , GRIFFITHS ELLIS
Published: February 2008

Pot‐grown barley plants were exposed to infection by powdery mildew at different growth stages and for different periods of time. Mildew attacks up to G.S. 5·0 (Feekes scale, Large, 1954) greatly reduced the number of fertile tillers at harvest and also reduced the number of grains per head and grain size, even when the disease was controlled during later stages of growth. Mildew infection after G.S. 5·0 still reduced tiller numbers but to a lesser extent and yield loss at these later stages was due mainly to loss in grain size and grain number. In one experiment the size of the root system was recorded at harvest. Mildew, particularly when the infection occurred early (before G.S. 7·0), reduced the size of the root system. Root weight per plant was strongly correlated with grain yield per plant and tiller number per plant.
Hedgerow hawthorn (Crataegus spp.) and blackthorn (Prunus spinosa) as hosts of fruit tree viruses in Britain
Authors: SWEET J. B.
Published: February 2008

Apple chlorotic leafspot virus (CLSV) was detected in 27 of 109 hawthorn and three of 67 blackthorn plants sampled in various parts of Britain. The CLSV isolates possessed similar properties to those isolated from other rosaceous species but differed in the severity of symptoms they induced in woody indicators. No seed or aphid transmission of CLSV was detected.

Prunus necrotic ringspot (PNRV) and prune dwarf (PDV) viruses were detected in four and three respectively of 67 blackthorn plants. The PNRV and PDV isolates were serologically closely related to isolates from cherry. Arabis mosaic virus was detected in one blackthorn plant, but plum pox virus was not found in any of the tested plants.
A study of populations of black‐grass (Alopecurus myosuroides) in winter wheat, as influenced by seed shed in the previous crop, cultivation system and straw disposal method
Authors: MOSS S. R.
Published: February 2008

A two year experiment was conducted in winter wheat infested with black‐grass.

In the first year black‐grass was either allowed to develop and shed seed freely or was completely controlled by herbicides.

In the second year straw was either burnt or removed by baling and three cultivation systems were compared – ploughing, tine cultivations and direct drilling. No black‐grass herbicides were applied in the second year.

The presence of seeds shed in the previous crop greatly influenced the black‐grass infestation in the direct drilled crop where it was calculated that 80–90% of plants were derived from these recently shed seeds. In the crop established after ploughing, the black‐grass infestation was unaffected by seed production in the previous crop. Tine cultivations gave results similar to those found with direct drilling. It is suggested that these differences between cultivations were due to the presence of old seeds in the soil which were brought up to the soil surface by ploughing, but not by cultivations which did not invert the soil.

Straw burning destroyed many freshly shed seeds on the soil surface and resulted in less black‐grass in the crop although the effect tended to be masked by cultivations.

The practical implications of the results are discussed.
Linkage between genes for resistance to downy mildew (Bremia lactucae) in lettuce
Authors: NORWOOD JUDITH M. , CRUTE I. R.
Published: February 2008

Data are presented for the joint segregation of the gene combinations: Dm‐2/Dm‐3, Dm‐3/Dm‐6, Dm‐2/Dm‐6 and Dm‐6/Dm‐8, following inoculation with five races of B. lactucae. It is postulated that Dm‐2, 3 and 6 comprise a tight linkage group but that Dm‐6 and Dm‐8 are not linked as has been proposed previously. Information on the reaction of some resistant lettuce cultivars to certain B. lactucae races and some new postulated host genotypes is also presented.
Acid phosphatase isoenzymes of Brassica oleracea seedlings and their application to sib testing in F1 hybrids
Authors: WILLS A. B. , WISEMAN EVELINE M.
Published: February 2008

Crude extracts from cotyledons of 2‐day‐old seedlings were separated by electrophoresis on polyacrylamide gels and stained for acid phosphatase. At least 22 bands were recognised, distributed over seven zones. Analysis of zone 1 allowed estimation of sib frequencies in 12 out of 19 hybrid cultivars. By applying either seedling zone 1 or acp‐1 seed acid phosphatase analysis, sib estimates could be made in 15 of these hybrids. It is suggested that this technique offers a practical and rapid means of estimating sib frequencies in commercial seed stocks.
Aerial dispersal of the potato gangrene pathogen, Phoma exigua var. foveata
Authors: CARNEGIE S. F.
Published: February 2008

A semi‐selective medium for isolating the potato gangrene pathogen, Phoma exigua var. foveata, from air is described. Airborne propagules of P. exigua var. foveata were generated for at least 57 min after the start of simulated raindrop impaction on senescent potato stems bearing pycnidia from a natural infection. The number of propagules generated as aerosols was 0·17% of that available for aerosolisation. The aerodynamic particle size of at least 92% of the aerosols was in the range 2·1–4·7 μm in diameter. Using a Casella High Volume Bacterial Sampler airborne propagules of P. exigua var. foveata were detected in the open air during rainfall from September to November at three sites in Southern Scotland. They were recovered at least 800 m down wind from the nearest potato crop. P. exigua var. exigua and P. eupyrena were also recovered from the air during rainfall. Very low numbers of P. exigua var. foveata were occasionally detected in the absence of rain. The role of airborne inoculum of P. exigua var. foveata is discussed in relation to reinfection of virus‐tested stocks of seed potatoes derived from stem cuttings.
The effect of seed treatment with benzimidazole‐based fungicides on infection of the foliage of overwintered salad onions by Botrytis cinerea
Authors: PRESLY A. H. , MAUDE R. B.
Published: February 2008

Seed treatments of carbendazim (Bavistin 50% W.p.) and thiophanate‐methyl (Mildothane 50% W.p.) applied to overwintered salad onions at 250 g a.i./kg seed protected the foliage of plants from infection by Botrytis cinerea during the seasons 1973–1976. Crop establishment and yield were also improved. Seed treatment with calomel was not effective. Chemical analysis of treated non‐viable seeds, retrieved from the soil, indicated that 73% carbendazim and 46% thiophanate‐methyl remained attached to the seeds after 9 months in the soil. Analyses of onion leaves revealed that each fungicide was represented by similar quantities of carbendazim, 5 μg/g fresh weight in October 1975 reducing to 1 μg/g fresh weight in May 1976. Bioassay tests showed that the fungicide was acropetally distributed and was present in all leaves early in the season (October) but was absent from some new leaves formed in the following spring.

Carbendazim‐insensitive isolates of B. cinerea occurred after three seasons' use of this chemical. Sensitive isolates failed to grow on agar containing 1 μg/ml benomyl but all insensitive isolates (31 total) grew normally at this concentration and some were capable of growth on agar containing 1000 μg/ml benomyl. The emergence of foliar isolates of the fungus insensitive to the benzimidazole‐based compounds used in the treatment of seeds indicated that these fungicides did not provide a permanent solution to the disease problem.
Control of Botrytis cinerea and Botrytis squamosa in overwintered salad onions by fungicide sprays
Authors: PRESLY A. H. , MAUDE R. B.
Published: February 2008

In 1974/75, 13 sprays of 0·2% a.i. thiram applied at 14 day intervals to overwintered salad onions reduced the incidence of Botrytis cinerea and significantly increased onion yields. In 1977/78 both B. cinerea and B. squamosa occurred, and 12 iprodione sprays at 0·1% a.i. applied at 14‐day intervals or 6 sprays at 0·2% a.i. applied at 28‐day intervals gave good control of B. cinerea and B. squamosa and significantly increased onion yields. Benomyl (0·1% a.i. at 14‐day intervals, or 0·2% a.i. at 28‐day intervals) failed to control either pathogen because of the development of carbendazim‐insensitive strains of the fungi. Effective control of both pathogens and increased yields were obtained with an application of 0·4% a.i. thiram in October and November followed by an application of 0·2% a.i. iprodione in December and January.
Effects of treating seed potatoes from commercial and stem cutting stocks with benomyl, thiabendazole and 2‐aminobutane on yield and disease
Authors: HIDE G. A. , BELL F.
Published: February 2008

Potato seed tubers of six cultivars from commercial stocks and from stocks derived from stem cuttings (healthier seed) were fumigated with 2‐aminobutane 2 wk after lifting or treated with benomyl or thiabendazole in January. 2‐aminobutane prevented skin spot and gangrene developing on treated tubers. Experiments were planted at Rothamsted (clay with flints soil) and at Woburn (sandy loam soil) in 1973–75.

Healthier seed produced more stems/plant than commercial stocks and yielded on average 8% more at Rothamsted in 1973 and 1974 and respectively 5 and 10% more at Woburn in 1973 and 1975. Seed treatments did not consistently affect stem numbers or increase yield although all treatments tended to decrease tuber size.

Infection of stem bases and tubers by Polyscytalum pustulans and Rhizoctonia solani was usually less from healthier than from commercial seed and was decreased by benomyl and thiabendazole in 1973 and 1974. Infection by Helminthosporium solani of the skin around tuber eyes was greater from healthier than from commercial seed but was decreased by benomyl and thiabendazole. 2‐aminobutane sometimes decreased infection of tubers by P. pustulans and R. solani but neither of stem bases nor of tubers by H. solani. Gangrene on tubers uniformly wounded at lifting was not consistently affected by seed source or seed treatment.

Treating seed with benomyl or thiabendazole in 1975 decreased skin spot and black scurf in tubers stored until March 1976. These treatments also decreased silver scurf on the produce of commercial seed at Rothamsted but gangrene was not consistently affected by seed treatments.
An assessment of fungicides for the control of wilt and die‐back caused by Phytophthora cinnamomi in container‐grown Chamaecyparis lawsoniana cv. Ellwoodii
Authors: SMITH PAULINE M.
Published: February 2008

In fungitoxicity tests against Phytophthora cinnamomi on Chamaecyparis lawsoniana cv. Ellwoodii, a drench of furalaxyl (1000 mg a.i./l) applied to the compost in which 1‐yr‐old plants were growing, 1 wk before they were inoculated with 650 000 zoospores, controlled disease for at least 12 months. With an inoculum dose of 650 zoospores/plant, furalaxyl at 500 mg a.i./l controlled disease even when inoculation was 12 wk after fungicide treatment.

Aluminium tris (ethyl phosphonate) (2000 mg a.i./l) applied as a drench 1 wk before inoculation with 650 000 zoospores/plant did not prevent root infection but delayed foliar symptoms for 9 months: the same treatment, using etridiazole (500 mg a.i./l) only slightly reduced disease incidence.

When applied as a single drench 2 days before inoculation, prothiocarb (2000 mg a.i./l) and cuprammonium compounds (200 mg a.i./l) were much less effective than furalaxyl (1200 mg a.i./l), sodium ethyl phosphonate (1500 mg a.i./l), aluminium tris (ethyl phosphonate) (1500 mg a.i./l) or etridiazole (500 mg a.i./l).

However, a drench of furalaxyl at 1000 mg a.i./l, aluminium tris (ethyl phosphonate) at 2000 mg a.i./l or etridiazole at 500 mg'a.i./l did not eradicate P. cinnamomi from compost containing infected root debris. Pre‐planting drenching of the compost was ineffective.

All fungicide treatments were non‐phototoxic to 1‐yr‐old C. lawsoniana cv. Ellwoodii.

These results are of special relevance to the control of P. cinnamomi on container‐grown woody ornamentals.
Insect transmission of okra mosaic virus in the Ivory Coast
Authors: GIVORD L. , BOER L. DEN
Published: February 2008

The Ivory Coast and Nigerian strains of okra mosaic virus (OMV) were transmitted by the flea‐beetle Podagrica decolorata, a serious pest of okra in the southern Ivory Coast. The Ivory Coast strain was also transmitted by the orthopteran, Zonocerus variegatus. The Ivory Coast strain was acquired faster than it was inoculated by P. decolorata. When groups of five beetles were given acquisition and inoculation access periods of 24 and 48 h, respectively, 60% of the okra test plants were infected. OMV‐carrying P. decolorata remained infective for up to 6 days. The virus was readily detected in extracts of crushed beetles that had fed on infected plants for 20 h. The beetle was also able to transmit to and from plants of Hibiscus sabdariffa and Corchorus olitorius; as a food source it preferred C. olitorius to okra or H. sabdariffa. The beetle is active throughout the year, and presumably can spread OMV at any time between plants of these species. A considerable and unexplained decrease in frequency of transmission was observed in experiments done in the rainy season. The revised cryptogram of OMV is R/l:*/32:S/S:S/Ve/Cl.
I. Pathogenic variation in fungi and bacteria and mycorrhizal compatibility: The genetic architecture of aggressiveness in Ustilago maydis
Authors: BASSI F. G. A. , BURNETT J. H.
Published: February 2008

Isolates of Ustilago maydis (D.C.) Cda are known to differ in the degree to which they can parasitise maize and, as no differential reaction occurs between pathogen and host, these differences must be differences in aggressiveness.

Inoculation of juvenile maize plants induced morphological changes which provided a means of assessing and distinguishing U. maydis isolates in respect of their aggressiveness. Thus it was possible to carry out a survey of the genetic architecture of aggressiveness in natural populations of the pathogen.

The distribution of aggressiveness within a single gall suggested that selection had taken place over a number of generations in favour of genes or gene systems tending to increase aggressiveness. Diallele analyses of isolates from two natural populations revealed that aggressiveness had a low heritability and was determined by genes exhibiting mainly non‐allelic interaction.

It has been proposed that horizontal resistance in host cultivars would have a more long lasting protective effect against disease. However, the genetic architecture of aggressiveness in U. maydis should enable the pathogen to respond rapidly to changes in host resistance and the skewed distribution found within a single gall tends to support this. Therefore, the use of higher levels of host resistance should rapidly select for higher aggressiveness in the pathogen.
I. Pathogenic variation in fungi and bacteria and mycorrhizal compatibility: Intraspecific variation in a mycorrhizal association
Authors: MASON P. A.
Published: February 2008

Laboratory studies with combinations of the fly agaric, Amanita muscaria (L. ex Fries) Hooker and birch (Betula pendula (Roth.)) suggest that the genetical control of mycorrhizal formation has features in common with the legume/Rhizobium symbiosis. There are at least four factors that can be genetically controlled by either the host or the fungus: (a) mycorrhizal formation; (b) the extent of mycorrhizal development; (c) the pattern of mycorrhizal branching, and (d) the shape and size of the host root system.
II. Cereal disease: the interplay between resistance and pathogenicity: Inheritance of pathogenicity in Gaeumannomyces graminis var. tritici
Authors: BLANCH P. A.
Published: February 2008

The purpose of the research was to discover whether pathogenicity in G. graminis is under major gene or multiple gene control and how pathogenic variation is generated in the field. The shoot dry weight of infected wheat seedlings was used as a measure of pathogenicity.

Crosses were made between isolates differing in pathogenicity using a weakly pathogenic auxotrophic mutant requiring para‐aminobenzoic acid for growth as one of the parental isolates in each cross. A nuclear marker was necessary since G. graminis is homothallic. The mutation was produced by irradiating macerated hyphal strands with ultra‐violet light.

Analysis of the progeny indicated that pathogenicity is under multiple gene control and that most of the genotypic variation is additive. There is a possibility of non allelic interactive effects but the evidence is not conclusive.

The possibility of heterokaryosis in G. graminis was investigated by comparing pathogenicity between hyphal tip cultures and internal cell cultures derived from individual field isolates. Some field isolates were shown to be heterogeneous. In addition, heterokaryotic hyphae were synthesised between the mutant isolate and its parental wild‐type isolate. These results showed that potentially G. graminis could grow as a heterokaryon although how widespread this is in nature is not clear.
III. Variation in plant viruses: Variation in ryegrass mosaic virus in relation to resistance
Authors: WILKINS P. W.
Published: February 2008

Some isolates of ryegrass mosaic virus are mild in all but a few plants, others are more severe. Infection with a severe isolate reduced the yield of a ryegrass population by 24% under field conditions and reduced survival following cold treatment by 85%. Field isolates from the short‐lived Italian ryegrasses are generally severe while those from the long‐lived late‐flowering perennial ryegrasses are generally mild. This variation appears to be adaptive in origin since in the case of perennial ryegrass proneness to infection by severe isolates would probably lead to the elimination of both host and virus whereas Italian ryegrass can escape infection readily by copious production of seed.
IV. Variation in fungicide tolerance: Variation in Erysiphe graminis f. sp. hordei in response to the fungicide ethirimol
Authors: HOLLOMON D. W.
Published: February 2008

The genotypic variation of Erysiphe graminis f. sp. hordei was examined using ethirimol in an in vitro bioassay. ED50 values of 45 isolates from untreated crops ranged from 0·002 μg/ml‐1to 20μg/ml1.

Less variation was encountered in isolates from ethirimol treated crops, where ED50 values ranged from 0·02 μg/ml‐1to 20μg/ml‐1. Crosses between isolates with intermediate levels of ethirimol sensitivity increased variation, and many progeny exceeded the sensitivity of either parent. The response of barley powdery mildew to ethirimol seems to be controlled by a complex genetic system, rather than by one or two major genes. Nevertheless, heritability was surprisingly high in two crosses analysed (0·596). Progeny virulent on the varieties Julia (vg) or Sultan (vas) were possibly more resistant to ethirimol than those with the alternative avirulent allele, but the differences were not significant (P= 0·05).
IV. Variation in fungicide tolerance: Comparisons between isolates of Erysiphe graminis f. sp. hordei tolerant and sensitive to the fungicide tridemorph
Authors: WALMSLEY‐WOODWARD DIANNE J. , LAWS F. , WHITTINGTON W. J.
Published: February 2008

Forty‐five single pustule isolates of barley powdery mildew taken at random from tridemorph treated and untreated plants were maintained in culture on leaf segments of barley cv. Golden Promise placed on agar containing benzimidazole. In repeated assays for tridemorph tolerance over a 10 month period, tolerance was found in 25 of 36 isolates from treated plants, and remained stable in all but four of the isolates wherein tolerance was lost after varying lengths of time. A negative correlation was found between pathogenicity and tolerance. The germination of tolerant isolates was less depressed than the sensitive on treated seedlings, but no differences between isolates were found on untreated seedlings. Colony growth of all isolates was slower on treated than untreated seedlings. On plants of several cultivars kept in growth rooms, mildew progressed more rapidly on treated barley when tolerant isolates were used as inoculum. Visible disease symptoms spread most rapidly on isolated, untreated plants, and most slowly on isolated treated plants, irrespective of the isolate. Disease on treated plants progressed more rapidly when untreated plants were adjacent, suggesting that interactions take place between pathogen populations on treated and untreated plants.
Studies on Entomophthora in populations of Aphis fabae on field beans
Authors: WILDING N. , PERRY J. N.
Published: February 2008

The population of Aphis fabae on field beans at a site in Highfield, Rothamsted in 1973 reached its peak 1 wk earlier than that at an equivalent site in Mill Dam Close, Woburn, 29 km NW of Rothamsted. Epizootics of Entomophthora caused weekly maximum mortalities of adult apterae of 71% at Highfield and 67% at Mill Dam Close. These epizootics and the periodicity of Entomophthora conidia in the air closely paralleled the development of the aphid population. There was little evidence of a consistent relationship between Entomophthora infection and any of the weather factors considered. At both sites most mortality was caused by E. planchoniana though many aphids were killed by E. aphidis and E. obscura. E. fresenii and E. virulenta killed very few aphids. Most conidia in the air were of the E. aphidis‐type. Up to 44% of alatae emigrating from bean crops were infected with Entomophthora, confirming that aphid migration is an important means of distributing the fungi. Aphid numbers rose to more than 1600/plant at both sites, in spite of the action of Entomophthora, and would probably have been less had the fungi been more abundant earlier in the season.
Studies on the spread of Gaeumannomyces graminis var. tritici in wheat.
Authors: PREW R. D.
Published: February 2008

The autonomous spread of Gaeumannomyces graminis var. tritici from discrete sources of inoculum, consisting of naturally infected stubble and roots, was measured in three field experiments. Spread occurred from only half of the inoculum sources and when it did occur it averaged a distance of only 10 cm.
Studies on the spread of Gaeumannomyces graminis var. tritici in wheat.
Authors: PREW R. D.
Published: February 2008

The effect of cultivations on the spread of Gaeumannomyces graminis var. tritici from a line source of inoculum, consisting of naturally infected stubble and roots, was recorded in the field over 2 yr. With the aid of cultivations, spread in the first wheat crop occurred frequently to a distance of 0·9 m and occasionally to a distance of 2·5 m. However, the following wheat crop was uniformly infected, probably as a result of a rapid build‐up of background inoculum in the first wheat, so that any spread by cultivations was masked.
The influence of photoperiod on growth patterns of Erysiphe graminis f. sp. hordei
Authors: CARVER T. L. W. , WILLIAMS OLWEN
Published: February 2008

Detached seedling leaf segments of five spring barley genotypes were inoculated with an isolate of barley mildew to which they possessed different levels of resistance. Segments of each host genotype were then incubated under either continuous light or treatments with 2, 4, 8 or 16 h darkness per 24 h cycle. Macroscopic observation showed that the latent period of infection was reduced slightly in treatments with at least 4 h darkness/24 h. Yellowing of detached segments occurred fastest under continuous light and slowest under a 16 h dark/8 h light cycle. Microscope observation of segments fixed 4·5 days after inoculation showed that as the length of the dark period increased, so the number of haustoria formed per colony also increased. This increase in haustorial production appeared to be associated with an accentuation in the synchrony of production of the secondary and tertiary haustorial generations. Varietal differences in susceptibility were also more marked in segments incubated under short days. It is concluded that under the conditions of temperature and light intensity used, a 16 h dark/8 h light system is most desirable for quantifying mildew resistance because it allows confident identification of distinct haustorial generations, accentuates differences in varietal susceptibility and delays chlorophyll degradation in detached barley leaves infected with mildew.
The effect of defoliation on yield of radish
Authors: JACKSON T. A.
Published: February 2008

The effects of artificially defoliating radish at different times during growth were examined in pot experiments. Hypocotyl yields were negative linear functions of the level of defoliation irrespective of the stage at which this occurred as the plants were unable to compensate for loss of foliage. Yield was proportional to leaf area duration and greatest losses in yield followed the earliest defoliations.
Promotion of cone and seed production on Sitka spruce by gibberellin application
Authors: TOMPSETT P. B. , FLETCHER A. M. , ARNOLD GILLIAN M.
Published: February 2008

Gibberellin mixtures were applied to large, mature scions of Sitka spruce, growing in the open at Wauchope Tree Bank in 1975, 1976 and 1977. Large increases in coning and seed production, and in the numbers of clones producing seed, occurred in the year after treatment. Cone and seed yields varied with the timing and concentration of hormone treatment, and were greatest when applications were made in the top two branch whorls on the tree. Clonal differences in seed production were observed among gibberellin‐treated branches. Seed quality, judged by seed weight and percentage germination, appeared normal. Promotion of male strobili was greater in lower branch whorls than in the top branch whorl on the tree.

Ways in which these findings can be applied in breeding and seed production are discussed.
Comparative physiology of field‐grown tomatoes during ripening on the plant or retarded ripening in controlled atmospheres
Authors: GOODENOUGH P. W. , THOMAS T. H.
Published: February 2008

Tomato fruits of six cultivars were harvested at three different stages of maturity or were harvested when mature‐green and then stored in a modified gas atmosphere (2·5‐4% O2; 4% CO2) for 2 months. The fresh and stored fruits were analysed for their contents of sugars, organic acids and free amino acids, while proteins were separated by discontinuous electrophoresis on polyacrylamide gels. In general, the low molecular weight components decreased during storage. A comparison of mature‐green fruits before and after storage showed that although total protein was not decreased, a different electrophoretic pattern was obtained following controlled atmosphere (CA) storage. Thus, although controlled atmosphere storage repressed the loss of chlorophyll and synthesis of lycopene, carotenoids and xanthophylls, the biochemical parameters measured showed a controlled change towards the conditions exemplified by ripe fruits. This was not so marked in some cultivars as it was in others.
The production of toxins by Botrytis fabae in relation to growth of lesions on field bean leaves at different humidities
Authors: HARRISON J. G.
Published: February 2008

Filtrate extracts from liquid cultures of B. fabae and extracts from spreading chocolate spot lesions contained at least two heat‐stable, light‐labile phytotoxic compounds. Lesions similar in appearance to those of chocolate spot developed after injection of fractions containing these compounds into healthy bean leaves. Of 15 plant species injected with an extract from lesions, Vicia faba appeared to be the most susceptible to damage.

Evidence is presented to support the hypothesis that under conditions of low humidity the concentrations of toxic compounds in an infected leaf become high enough to kill healthy cells surrounding infected tissue. The dead tissue then dries out preventing further fungal growth and lesion spread. In saturated air, however, the toxic compounds diffuse throughout the lamina and become too dilute to kill uninfected tissue. Tissue does not become desiccated and the fungus continues to spread.
The disappearance of benomyl from mushroom casing
Authors: FLETCHER J. T. , CONNOLLY G. , MOUNTFIELD ELIZABETH I. , JACOBS L.
Published: February 2008

The failure of Benlate (50% benomyl) to control Mycogone perniciosa on mushroom farms where isolates of the organism were benomyl sensitive was investigated. A comparison was made of carbendazim levels, the major fungitoxic breakdown product of benomyl, in unsterilised casing, autoclaved casing and autoclaved casing mixed with a small proportion (1.7%) of casing previously treated with benomyl but from which all detectable levels of carbendazim had disappeared. Added benomyl was effective in controlling M. perniciosa in autoclaved casing, less effective in unamended casing and ineffective in the amended casing mixture. The recovery of carbendazim from these treatments was directly related to disease occurrence.

Studies on farms where benomyl or other carbendazim generating fungicides had been used indicated that a lack of control of M. perniciosa was associated with the disappearance of fungicide from the casing before cropping began. This was not so on a farm where carbendazim generating fungicides had not been used before these investigations. Thiabendazole, a fungicide closely related to the carbendazim generators showed only a slight decline in concentration in casing capable of degrading benomyl.

Bacteria isolated from the casing were examined in vitro for their ability to degrade benomyl. Five groups of bacteria were compared and three bacteria, Pseudomonas putida, Pseudomonas aeruginosa and an unidentified member of the Entero‐bacteriaceae were most able to degrade benomyl.
Genetic analysis of resistance to swede mildew
Authors: BRAIN P. J. , WHITTINGTON W. J.
Published: February 2008

The incidence of swede mildew (Erysiphe cruciferarum) was analysed on three occasions in five swede varieties Crifel, Doon Major, Harvester, Ne Plus Ultra and Ruta Øtofte and their F1 hybrids. Overall levels of infection were greater in Ne Plus Ultra and Harvester and least in Ruta Øtofte. Genetic analysis by the diallel method showed that initially resistance was recessive with Ruta Øtofte possessing most recessive genes but results from the final analysis showed partial dominance, with Ne Plus Ultra having most recessive and Harvester most dominant genes. The changing pattern of inheritance with time was due to variation in the rates of increase in disease incidence and diallel analyses of these rates, calculated by regression analyses over five observations, showed in almost entirely additive control. Although no variety was immune it was considered that except on soils of high pH or in the event of a marked change in the genetic composition of the pathogen the level of resistance in Ruta Øtofte was satisfactory.
Variation in germination and seedling emergence of sugar beet at sub‐optimal temperatures
Authors: BROWN S. J.
Published: February 2008

Patterns of germination and seedling emergence at different temperatures were determined for a wide range of sugar beet accessions. There was good differentiation among seed lots and a close relationship between germination and emergence in temperature regimes of 20 h at 5 °C: 4 h at 7 °C, and constant 5 °C. Failure to germinate at temperatures between 5°C and 7 °C was more often associated with suppression of germination than with death of embryos. Results indicated that tests of germination at low temperatures would lead to more accurate predictions of field emergence than standard tests at 20 °C. Furthermore, tests at 20 °C may not give accurate estimates of potential viability.
Comparison of laboratory infection of aphids by Metarrhizium anisopliae and Verticillium lecanii
Authors: HALL R. A.
Published: February 2008

The pathogenicity of the only documented ‘aphid’ strain of Metarrhizium anisopliae for the aphid, Macrosiphoniella sanborni, was established by experimental infection. Its aphicidal potential was assessed by conducting parallel experiments with Verticillium lecanii, a fungus of proven efficacy in controlling aphids. The spore germination, growth and sporulation rates of M. anisopliae were slower than V. lecanii and were most likely the principal factors determining the higher LC., values in bioassay and slower propagation of this fungus amongst aphid populations. It is concluded that M. anisopliae, except perhaps in the salt marsh habitat from which it was originally isolated, would not prove as useful an agent as V. lecanii in biological control of aphids.
Properties of a carlavirus causing a latent infection of pepino (Solanum muricatum)
Authors: THOMAS WAYNE , MOHAMED N. A. , FRY MARGARET E.
Published: February 2008

Pepino (Solanum muricatum) cuttings imported from Chile contained a latent virus which was transmitted by inoculation of sap to Chenopodium quinoa but not to 21 other species. The virus was transmitted by the aphid, Myzus persicae. In C. quinoa sap, the virus lost infectivity when diluted between 10‐3 and 10‐4, heated for 10 min between 65 and 70 °C, or stored at room temperature for 4 to 6 days.

The virus particles were straight or slightly flexuous filaments 660 to 680 nm long. Up to 15 mg virus per 100 g C. quinoa leaves was obtained by clarification with a mixture of chloroform and carbon tetrachloride. Purified preparations had Amax/Amin= 1.11, A260/A280= 1–30, A0.2601%= 2.8, and contained a single sedimenting component with a sedimentation coeficient of 149s and a buoyant density in CsCl of 1–318. The virus particles contained 5.5% of single‐stranded RNA of mol. wt 2.4×106 (estimated by gel electrophoresis of undenatured RNA) and sedimentation coefficient 38.5S, and a single polypeptide of mol. wt 33 000.

The virus is distantly serologically related to potato S and carnation latent viruses and is considered a new member of the carlavirus group. The name pepino latent virus is proposed. The cryptogram for this virus is R/1: 2.4/5–5: E/E: S/Ve/Ap.
Effects of aeration during cold storage of germinated vegetable seeds prior to fluid drilling on seedling viability
Authors: BROCKLEHURST P. A. , DEARMAN JANE , FINCH‐SAVAGE W.
Published: February 2008

Germinated seeds of cabbage, carrot, lettuce and onion were stored for 15 days at 1 °C either in water or humid air before being fluid drilled. In aerated water and humid air, seedling viability was maintained for cabbage, carrot and lettuce, and only slightly reduced for onion. Storage in unaerated water reduced seedling viability by 48%‐100%. Seeds continued to germinate in aerated storage, but radicle elongation occurred only with cabbage and lettuce.
Controlled atmosphere storage of winter white cabbage
Authors: GEESON J. D. , BROWNE K. M.
Published: February 2008

In four laboratory experiments and five commercial scale trials carried out between 1977 and 1979, five cvs of winter white cabbage were stored at 0–2 °C for 29–43 wk in controlled atmospheres (C A) consisting of c. 5–6% CO2, 3% O2 and the remainder N., or in air. The incidence of rots caused by Botrytis cinerea was reduced and the incidence of ‘pepper‐spotting’ (a non‐microbial leaf necrosis disorder) was reduced or eliminated by storage in CA. Storage and trimming weight losses were lower and the recoveries of trimmed cabbage suitable for marketing or processing up to 22% higher in cabbage stored in CA than in those stored in air. Sensory assessments of four cvs tested indicated that CA‐stored cabbages retained their green colour, crisp texture and fresh flavour better than the corresponding air‐stored samples.
Effect of temperature on growth of some avirulent fungi and cross‐protection against the wheat take‐all fungus
Authors: WONG P. T. W.
Published: February 2008

The linear growth rates of Gaeumannomyces graminis var. graminis, G. graminis var. tritici, Phialophora radicicola var. graminicola and a lobed hyphopodiate Phialophora sp. were studied on agar at various temperatures between 5 and 30 °C and on wheat roots at two temperature regimes (12 h at 7°/12 h at 13 °C and 12 h at 17°/12 h at 23 °C). On agar at 30 °C, the isolates of G. graminis graminis grew faster than those of G. graminis tritici and Phialophora sp. but three isolates of G. g. graminis grew more slowly than the other two fungi at 5 and 10 °C. Two other isolates of G. g. graminis were cold‐tolerant and had growth rates comparable to those of G. g. tritici and Phialophora sp. at 10 °C. The growth rates of Australian isolates of P. radicicola graminicolu were similar to that of a British isolate and were about a third to a half those of the other three fungi at most temperatures. The growth rates of the fungi on wheat roots at the low and high temperature regimes were correlated with the growth rates on agar at 10 and 20 °C respectively. The correlation was better at low temperatures r= 0.81) than at high temperatures (r = 0.62).

Cross‐protection experiments using two G. g. graminis isolates which grow poorly at temperatures below 15 °C and a cold‐tolerant isolate each of G. g. graminis and Phialophora sp. showed that, while all four fungi protected wheat against take‐all at high temperatures (17/23 °C) as evidenced by less severe disease and significantly greater dry weights, only the cold‐tolerant fungi were effective at low temperatures (7/13 °C). The use of cold‐tolerant isolates of avirulent fungi in field experiments may result in better protection in the early stages of wheat growth when Australian soil temperatures are mostly below 15 °C.
The effect of iprodione on sclerotium germination, root infection and mycelial spread of Sclerotium cepivorum in salad onions
Authors: ENTWISTLE A. R. , MUNASINGHE H. L.
Published: February 2008

Iprodione seed treatment at 125 g a.i./kg seed and stem base sprays at 0–3 and 0.125 g a.i./m row delayed the appearance and reduced the incidence of stem base symptoms and root infection with Sclerotium cepivorum in autumn‐ and spring‐sown salad onions. Viability of sclerotia was unaffected by the treatments but their germination was delayed. The spread of mycelium between plants was suppressed but growth of hyphae within infected roots was much less affected.
Glycine mosaic virus: a comovirus from Australian native Glycine species
Authors: BOWYER J. W. , DALE J. L. , BEHNCKEN G. M.
Published: February 2008

Two strains of a virus designated Glycine mosaic virus (GMV) were found in Glycine clandestina and G. tabacina, legumes indigenous to Australia and the western Pacific region. When transmitted by sap inoculation, GMV infected mostly leguminous species, and caused mosaic and mottling symptoms. The virus was not found naturally in soybean G. max, but it infected all of the 21 cultivars tested.

GMV has isometric particles of c. 28 nm diameter, and produces three components with sedimentation coefficients of 60 S (top), 103 S (middle), and 130 S (bottom). Both middle and bottom components are required for infectivity. The virions contain two major proteins with molecular weights of c. 21 500 and 42 000. GMV produces large aggregates of particles in the cytoplasm of the mesophyll cells of pea Pisum sativum, and also induces amorphous membrane‐bound bodies and cytoplasmic vesicles. The type strain (from New South Wales) reacts with antisera to Echtes Ackerbohnenmosaik, broad bean stain, and a Californian isolate of squash mosaic virus. The GW strain (from Queensland) reacts with all of the latter antisera, as well as with antisera to cowpea mosaic virus (Sb and Ark strains), bean pod mottle, and red clover mottle viruses, and is serologically related to, but not identical with, the type strain. These properties clearly establish GMV as a new member of the comovirus group.
Effect of plant density and nitrogen on wheat F1 hybrids and their parents
Authors: DONE A. A. , WHITTINGTON W. J.
Published: February 2008

In two field experiments (1973, 1974) the effects of increasing plant density (17.25, 34.5, 69.0, 138.0, 276.0 kg seed ha‐1 in Expt 1 and 23.5, 47.0, 94.0, 141.0 188.0, 282.0 kg seed ha‐ in Expt 2) and nitrogen levels (0. 39, 78, 117, 156 kg N ha‐ and 45, 67, 89 kg N ha‐1) were studied. Increased grain yields in both experiments only occurred from the lowest to the second lowest seed rate. Increased seed rate increased tiller density but decreased the number of grains per spikelet and spikelets per ear. In the first experiment yield and thousand‐grain weight were reduced by increased nitrogen whilst in the second experiment these characters were increased. Mildew was prevalent in the first experiment especially at the higher nitrogen levels. In both experiments the inbred and F1 hybrid genotypes tended to behave similarly and the grain yields of the hybrids did not exceed either those of their parents or the highest inbred at any plant density or nitrogen level. The F1 hybrids had greater mean grain weights than the inbreds, probably as compensation for a reduced number of grains per ear or decreased tiller density.