bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of soil‐applied granular pesticides and irrigation on the yield of sugar beet in fields infested with Trichodorus viruliferus
Authors: COOKE D. A.
Published: February 2008

In field samples taken on a grid pattern during four winters over an 80 ha farm there were many Trichodorus viruliferus (up to 3000/litre soil) in light soils but few in heavier soils. Depth samples taken during the summer showed Trichodorus to be the only nematode genus which was more numerous below plough depth than in the plough layer. In field experiments in the most heavily infested part of the farm, soil‐applied granular pesticides did not increase sugar yields following the dry spring of 1982; aldicarb increased sugar yields in one experiment following the wet spring of 1983 although it, and other granular pesticides, did not affect yield in an adjacent experiment where T. viruliferus were fewer. Irrigation during the dry summer of 1983 maintained relatively large populations of T. viruliferus, whereas in unirrigated plots without aldicarb populations declined by over 50%. Economic thresholds for T. viruliferus in 1983 at Broom's Barn were about 700/litre in unirrigated soil and 300/litre in irrigated soil.
Senescence and net photosynthesis of the flag leaf and grain growth of wheat in response to fungicide
Authors: DAVIES W. P. , KETTLEWELL P. S. , GREEN HELEN J. , HOCKING T. J. , JARAI MARIANNA M.
Published: February 2008

Green leaf area and net photosynthesis of the flag leaves of Avalon and Maris Huntsman winter wheat crops were studied in relation to grain growth following the application of the fungicide propiconazole at flag leaf emergence. Disease levels were low during grain‐fill, and were not significantly affected by the fungicide. Propiconazole significantly maintained green leaf area and photosynthesis per unit area during the period of rapid flag leaf senescence, but it had no effect on stem weight, grain growth or yield.
Floral biology and pollen viability of parental lines of onion hybrids
Authors: ALI M. , DOWKER B. D. , CURRAH L. , MUMFORD P. M.
Published: February 2008

Parental lines (inbred and hybrid male‐sterile lines and inbred pollinators) of prospective F, hybrids from the NVRS spring‐sown bulb onion breeding programme were examined to study their floral biology and aspects of pollination under glasshouse conditions. Inbreeding depression occurred in both pollinator and male‐sterile inbreds in terms of reduced flower numbers per umbel and a greater proportion of defective pistils. Male‐sterile and male‐fertile lines differed in their stigma and style characteristics and pattern of development. At flower opening, the styles of male‐sterile lines were longer and the stigmatic knob became receptive relatively sooner. The inbred male‐sterile line II/3 ms appeared to have a reduced receptive area on its stigmatic knob and remained receptive for a relatively shorter period. Individual lines differed for time of flowering, nectar content and its sugar concentration, and in their effectiveness as male and female parents as judged from pollen tube growth down the style in specific pairings. Assessment of pollen viability using the fluorescein diacetate test did not correlate with assessments based on pollen grain germination and subsequent growth down the style, perhaps as a result of differential receptivity in the inbred lines tested.

These results are discussed in relation to future hybrid seed production.
Patterns of spread of the non‐persistently transmitted bean yellow mosaic virus and the persistently transmitted subterranean clover red leaf virus in Vicia faba
Authors: JAYASENA K. W. , RANDLES J. W.
Published: February 2008

Patterns of spread of two aphid borne viruses, the non‐persistently transmitted bean yellow mosaic virus (BYMV) and the persistently transmitted subterranean clover red leaf virus (SCRLV), were compared simultaneously in field plots of Vicia faba minor grown in a Mediterranean climate (winter‐spring growing season, and dry summer).

Spread from a primary source was mapped following the artificial introduction of virus alone, or virus with vector, at the centre of the plots. BYMV spread rapidly from the virus source whether or not vectors were introduced with the virus. By contrast, SCRLV spread from the source only when plants were also artificially infested with the vector Aulacorthum solani. An attempt was made to evaluate the importance of secondary spread of both viruses by assessing the degree of clumping of infected plants that occurred outside the primary sites of virus introduction. BYMV‐infected plants were clumped in each treatment irrespective of whether the virus was introduced alone or with vector, as well as in control plots. Clumping of SCRLV occurred only when the vectors were introduced on virus source plants at the beginning of the experiment.

Times of spread were determined both by exposing trap plants at 4‐weekly intervals throughout the 30 month trial period, and by analysing the rates of spread in experimental plots between June and November in one growing season. Both viruses spread in the spring when vectors were flying, but negligible spread of the viruses was observed in the autumn despite aphid flight activity.

Times of flight of the four main aphid vector species were continuously monitored with yellow water traps. A major spring and a minor autumn flight peak were observed for Aphis craccivora, Macrosiphum euphorbiae, Aulacorthum solani and Myzus persicae. Aphid flights occurred predominantly in weeks when the mean temperature was in the range 13–17°C. Rainfall above 7 mm per week appeared to affect flights only when mean weekly temperatures were outside the range 13–17°C.
Flowering of contrasting white clover varieties in relation to daylength in controlled environments and in the field
Authors: NORRIS I. B.
Published: February 2008

The effect of 12, 14 and 16 h photoperiods, given consecutively, on flower production in 10 varieties of white clover (Trifolium repens) in controlled environments, is described. The effect of natural daylengths from September to July on the same plants in the field was also studied in the following year. Relationships between morphological and physiological traits and flowering were examined.

In controlled environments most plants flowered under the longest days, three times as many in the 16 h daylength as in the 12 h. Larger leaved types had a higher proportion of reproductive plants than did smaller leaved types.

Floral initiation was not observed in the field until daylengths were in excess of 15 h.

Increasing daylength increased flower production, floret and ovule numbers but did not appear to increase nectar production significantly.
A hand tool to assess the strength of flax and other fibrous materials
Authors: SEABY D. A. , MERCER P. C.
Published: February 2008

Flax fibres may become weakened during retting. A simple tool is described which can be used to assess their tensile strength. Other applications are also suggested.
Establishment and yield of three ryegrasses following aldicarb use, and changes in abundance of plant parasitic nematodes
Authors: SPAULL A. M. , MEWTON P. G. , CLEMENTS R. O.
Published: February 2008

Pure swards of Lolium multiflorum, L. multiflorum var. westerwoldicum and L. perenne sown in August had greater yields than autumn on areas treated with either 5 or 10 kg a.i./ha aldicarb than on untreated areas. Total annual dry matter yields increased by larger amounts where the greater rate of aldicarb was applied; throughout the trial, L. perenne was usually less affected by treatment than the other two grasses.

Plant‐parasitic nematodes were more numerous on untreated than treated plots and were fewest in areas receiving the larger application (except in the second harvest year). Numbers of Tylenchorhynchus and Helicotylenchus were affected most by treatments; abundance of Paratylenchus and Criconemella were little altered.

Stem‐boring Diptera invaded tillers of all three grasses but infection was least in L. perenne. Invasion occurred only on untreated plots in the establishment year and some yield benefit probably resulted from their control. In subsequent years invasion was similar on treated and untreated areas. Effects on other, non‐target organisms were not assessed.

Ectoparasitic nematodes multiplied more in L. multiflorum plots than in others during the first full‐harvest year. The next year numbers of Paratylenchus only were greater in plots of L. perenne than in other plots.

Sward persistence of L. multiflorum var. westerwoldicum was better on treated than untreated areas.

It was concluded a) that aldicarb use greatly decreased nematode numbers and yields from treated areas were larger than from those untreated; b) that sward persistence was similarly improved following aldicarb use and c) that ryegrasses differed in their suitability as hosts to ectoparasitic nematodes.
Problems in field selection for resistance to carrot fly (Psila rosae) in carrot cv. Long Chantenay
Authors: ELLIS P. R. , DOWKER B. D. , FREEMAN G. H. , HARDMAN J. A.
Published: February 2008

In field trials between 1973 and 1982 families of carrots of cv. Long Chantenay were assessed for their resistance to carrot fly (Psila rosae). In some but not all years, families selected for their observed resistance in earlier trials seemed more resistant than the parent line. In more than half the trials there was an association between carrot fly damage and root density, there being less damage on those families from which more roots were harvested. Thus, family selection within cv. Long Chantenay did not lead to a consistent improvement in resistance to carrot fly. Alternative strategies for achieving plant resistance to this pest are discussed.
Stem canker (Rhizoctonia solani) of maincrop potatoes.
Authors: HIDE G. A. , READ P. J. , SANDISON JANET P.
Published: February 2008

In two years, potato plants were sampled at 1 ‐ or 2‐weekly intervals from plots planted with seed tubers bearing sclerotia of Rhizoctonia solani (black scurf) and with seed without sclerotia either infested or not with cultures of R. solani at planting. Sprouted King Edward seed was used in 1981 and sprouted or non‐sprouted King Edward and Pentland Crown in 1982.

Stem canker decreased the number of aerial stems and decreased plant height by a constant amount throughout growth. The length but not the number of lateral stems (branches) was increased. Total fresh weight of foliage was decreased although few differences were significant, but the weight of foliage on main stems was decreased and the weight of laterals increased. Total leaf area was decreased by a constant amount throughout growth and the proportion of the leaf area on lateral stems increased. Infection increased % dry matter of main stems and dry weight per unit area of leaves and decreased total dry weights of stem bases and roots.

Tuber production was delayed on infected plants although more tubers were initiated later, and at harvest in 1981 infected plants had more tubers < 5 cm than healthy plants but similar numbers of larger tubers. Fresh weight of tubers increased at a similar rate on healthy and infected plants, but the infected plants yielded 50 g less than healthy throughout tuber bulking in 1981 and 20 or 80 g (King Edward, respectively sprouted and non‐sprouted seed) or 110 or 170 g (Pentland Crown) less than healthy in 1982. In both years, neither seed‐borne nor soil‐applied inoculum significantly decreased total or ware (>40 mm) tuber yields at harvest.

In both years soil‐applied inoculum had greater effects on plant growth and yield than seed‐borne inoculum.
A study of spatial distribution and population dynamics of two sympatric species of trichodorid nematodes
Authors: ALPHEY T. J. W.
Published: February 2008

The spatial distribution and population dynamics of Trichodorus primitivus and Paratrichodorus pachydermus were studied at a Scottish nursery site in replicated plots. Each plot was split and half was fumigated with dichloropropene. The numbers of males, females and juveniles under Scots pine (Pinus sylvestris), grass/clover (Lolium perenne/Trifolium repens) and fallow in non‐fumigated and fumigated subplots were recorded at 10 cm intervals to a depth of 50 cm every 4 months for 3 years.

In the non‐fumigated subplots the population densities of T. primitivus under each crop and the fallow soil were similar at the beginning and end of the experiment but P. pachydermus responded differentially, decreasing in fallow soils and increasing under pine. The ratios of adult: juvenile and male: female for the two species were not significantly affected by crop or sampling depth. T. primitivus was the more numerous species except under pine where P. pachydermus gradually became dominant during the study. Both species were present in all the depth samples but showed an aggregated distribution with different modal depths. The depth at which most P. pachydermus were found was shallower than for T. primitivus. Differences in the distribution and behaviour of the two species were found indicating how the two species could co‐exist or succeed each other.

Fumigation with dichloropropene decreased the trichodorid populations to < 1 per 200 g soil to a depth of 50 cm. The relative development of the populations under the different crops and fallow soil were similar to those in non‐fumigated soils.
The effect of plant density, harvest date and method on the yield of seed and components of yield of parsnip (Pastinaca sativa)
Authors: GRAY D. , STECKEL JOYCE R. A. , WARD J. A.
Published: February 2008

Experiments conducted over four years (1980–1983) with parsnip cv. Avonre‐sister examined the effects of plant density, harvest date and method on seed yield and the components of yield. In 1980, using the root‐to‐seed method, the yield of seed increased by 50% for an increase in plant density from 5.6 to 35 plants m‐2; the maximum yield at the optimum harvest date was 3015 kg h‐1. In the other three years, using the seed‐to‐seed method, seed yield increased to a maximum with an increase in plant density from c. 1 to 10 plants m‐2 but at higher densities yields were lower. At c. 10 plants m‐2, seed yields were 1567, 4029 and 1040 kg ha‐1, in 1981, 1982 and 1983, respectively, when harvested at the optimum time. An increase in plant density increased the number of non‐seeding plants in the population, reduced the number of umbels per plant and reduced the number of seeds per umbel. Mean seed weight was, in general, unaffected by plant density and so effects of density on yield reflected changes in seed numbers. Increasing the plant density increased the proportion of primary‐umbel seed. Maximum yields of seed were obtained from crops harvested at a seed‐moisture content of 50 to 70%, which occurred 46 ± 2·4 days after flowering. Delay in harvesting after this date led to a loss of yield of 33, 35, 139 and 32 kg ha‐1wk‐1 in 1980, 1981, 1982 and 1983, respectively. Plants cut, placed in the windrow to dry and then threshed gave similar yields to those harvested at the same time but dried in bins.
The presentation of treatment responses from block experiments after analysis of variance of transformed data
Authors: MORRIS G. E. L.
Published: February 2008

Many types of data require transformation in order to satisfy the underlying assumptions of analysis of variance. When treatment responses are to be presented on the original measurement scale, and the experiment was arranged in blocks, there are at least two methods of doing so, namely the value that would have been expected if the treatment had been applied to all plots in the experiment and the value that would have been expected if there had been no block effects. These differ, because they correspond to different models, and the magnitude of their difference increases as the block‐to‐block variation increases. Examples are given to illustrate these differences for a range of commonly used transformations and the occasions on which the two methods should be used are discussed.
Reproductive biology and related host‐parasitoid interactions between the gypsy moth, Lymantria dispar and Glyptapanteles flavicoxis, a gregarious endoparasitoid*
Authors: HU CUI , BARBOSA P. , MARTINAT P.
Published: February 2008

The mean total progeny produced by female Glyptapanteles flavicoxis was significantly greater when the parasitoid attacked 4th instar gypsy moth rather than younger larvae. The development of parasitoids within older instars was faster than that in younger hosts. The proportion of female progeny was not altered by the host instar parasitised. The total reproductive output per female G. flavicoxis increased as the number of host larvae increased. However, since the reproductive output was spread among more available hosts, the reproductive output per host declined as the number of host larvae increased. There was no trend in the relationship between total progeny produced or the proportion of female progeny and the number of matings of parental females.
Mechanical aids to improve the speed and sensitivity of plant virus diagnosis by the biological test method
Authors: LAIDLAW W. M. R.
Published: February 2008

Modifications to a Pollahne leaf sap press are described which allow it to be used for bioassay purposes without risk of cross contamination. Constructional details are given for manual and automatic versions which utilise hot and cold water to sterilise and cool the working parts of the press. Two compressed air guns which are used together to inoculate indicator plants, are also described. The first incorporates carborundum powder into a jet of air and causes controlled wounding of plant epidermal cells to permit virus entry. The other applies sap inoculum as a finely divided spray to the wounded plants. The variables affecting the use of these guns are discussed. Improvements in sensitivity of 64 fold, compared to manual methods were obtained and potential to develop this to 500fold demonstrated.
Resistance in apple to shoot infection by Venturia inaequalis
Authors: JEGER M. J. , ALSTON F. H.
Published: February 2008

Eight apple genotypes, including cultivars and breeding selections resistant and susceptible to Venturia inaequalis on foliage, were screened for shoot infection and the development of wood pustules following inoculation of shoot tips of 1–year maiden trees in the greenhouse. Where genotypes were highly resistant in terms of foliar symptoms (cvs Prima and Gavin), no shoot infection was observed. Where genotypes were highly susceptible in terms of foliar symptoms, then shoot tissue was either resistant (cv. Shinko) or susceptible (cv. Starking). In one experiment, shoot tips were inoculated sequentially as shoots extended. No pustules developed where inoculations were made later than May. In a further experiment, two leaf internode positions were inoculated on one occasion. Pustules were only observed where inoculations were made above the youngest unrolled leaf. The results suggested that shoot tips were more susceptible during early extension growth of the shoot. Pustules were noted in abundance on petioles of susceptible cultivars, and these probably contributed to early leaf abscission.
The effects of the foliar fungicide pyrazophos on beneficial arthropods in barley fields
Authors: SOTHERTON N. W. , MOREBY S. J. , LANGLEY M. G.
Published: February 2008

The insecticidal properties of the foliar fungicide pyrazophos were investigated in autumn‐ and spring‐sown barley crops using several methods to estimate the density of non‐target arthropods and by using manipulative experiments. In autumn‐sown crops, pyrazophos significantly reduced densities of cereal aphid natural enemies relative to pre‐treatment levels compared to areas of crop that were left unsprayed. These significant differences persisted in most groups for over 45 days after treatment. Groups most affected were aphid‐specific predators, polyphagous predators, (Carabidae, Staphylinidae but not Araneae) and parasitoids. Insects known to be preferred food items of wild gamebird chicks and other non‐target groups such as the Collembola were also significantly reduced in density on plots sprayed with pyrazophos, the effects again persisting for over 45 days. Densities of beneficial and non‐target insects were also reduced in plots of spring barley sprayed with pyrazophos. However, the experimental design meant that levels of reductions were not significant for most arthropod groups.

Removal of prey items (Drosophila pupae) placed in sprayed and unsprayed spring barley plots showed that the proportion predated was significantly lower on pyrazophos‐treated plots compared to those remaining unsprayed, the difference persisting for at least 7 wk after treatment. Removal of cereal aphids from colonies introduced to sprayed and unsprayed plots was also significantly lower on plots treated with pyrazophos. Difficulties of data interpretation associated with experimental design are discussed together with the consequences of the use of broad‐spectrum pesticides in I.P.M. programmes in cereals.
Effect of dodecanoic acid on the colonisation of sugar beet by aphids and the secondary spread of virus yellows
Authors: HERRBACH E.
Published: February 2008

The effect of dodecanoic acid, a behaviour‐controlling chemical which alters aphid feeding behaviour and virus transmission efficiency, was studied under field conditions. In a first experiment, dodecanoic acid reduced the level of natural colonisation of sugar beet by Aphis fabae. A second experiment revealed no significant influence of dodecanoic acid on the secondary spread of the semi‐persistent beet yellows virus and the persistent beet mild yellowing virus.
A comparison of inbred lines derived by doubled haploidy and single seed descent in spring barley (Hordeum vulgare)
Authors: CALIGARI P. D. S. , POWELL W. , JINKS J. L.
Published: February 2008

Samples of Fx inbred lines, derived by doubled haploidy (DH) and single seed descent (SSD) from five spring barley crosses were compared for agronomic characters. It was shown that, over this range of diverse crosses, inbreds derived by either technique could surpass the better parent or even the heterotic F1. The means of the DH and SSD were, however, different for a number of characters, as well as differing from the mid‐parent value. It was concluded that these differences stemmed from the presence of interacting genes showing linkage disequilibrium, although there was no unambiguous test to distinguish this from differential survival during the production of inbreds. This view was further supported by the finding that the DH sample, which tends to preserve existing linkages, produced a higher proportion of lines exceeding the better scoring parent when compared with the SSD population.
Observations on the distribution of potato cyst‐nematodes, Globodera rostochiensis and G. pallida on two fenland potato farms
Authors: WHITEHEAD A. G. , WESTERDIJK C. E.
Published: February 2008

The distribution of potato cyst‐nematodes, Globodera rostochiensis and G. pallida was surveyed in two widely separated fenland potato farms in Eastern England. Evidence was obtained of the suppression of G. rostochiensis and increase of G. pallida populations when Maris Piper and other potatoes with the same gene (H1) for resistance to G. rostochiensis are grown. Numbers of G. rostochiensis and/or G. pallida in the soil could not be related directly to recent potato cropping histories of the fields. Identification of the two species of Globodera by the presence and colour of females on the roots of Désirée, Maris Piper, Cromwell (A27/20) and A25/11 potatoes were confirmed by agarose gel isoelectric focussing of general proteins. Cromwell exhibited little or no resistance to G. pallida at Woodwalton. A25/11 was more resistant to this species at Woodwalton but was susceptible to G. rostochiensis. The results of these surveys emphasise the need for carefully planned and integrated control programmes based on the use of resistant cultivars of potato, crop rotations and appropriate nematicide use to combat the growing problem of G. pallida, especially in organic soils.
Within‐cultivar differences in relative leaf growth rates at low temperature of onion seedlings are not heritable
Authors: BREWSTER J. L. , BUTLER HEATHER A.
Published: February 2008

Onion seedlings of two open‐pollinated cultivars were grown either at a constant 10°C or outdoors in spring and were selected for high, medium or low relative leaf growth rate, RL. Flowering plants within each RL group were crossed using controlled pollination for the 10°C selections and as a fly‐pollinated polycross for the outdoor selections. The pollen donors of the 10°C selections were also selfed. Despite the wide variation of RL in the parent populations, there was no indication of heritability of RL. Mean RL was significantly lower for the progeny from self‐rather than cross‐pollinations as was initial leaf area and rate of seedling emergence.
The use of protein A‐sandwich ELISA as a means for quantifying serological relationships between members of the tobamovirus group
Authors: HUGHES J. d‘A. , THOMAS B. J.
Published: February 2008

Indirect protein A sandwich ELISA (PAS‐ELISA) was used to determine the serological relationship between eight tobamoviruses with antisera to 26 viruses and virus strains within the group. Very distant relationships were determined by trapping virus with heterologous antiserum and detecting it with homologous antiserum, while near and close relationships were differentiated by using heterologous antiserum each time. The results were esssentially consistent with previously recorded relationships determined by tube precipitin and other serological tests.

Since PAS‐ELISA requires much less antiserum than many conventional tests and does not require the purification of IgG or virus, it may offer many advantages in the detection of serological relationships.
The effect of augmenting grain aphid (Sitobion avenae) numbers in a field of winter wheat in spring on the aphid's abundance in summer and its relevance to the forecasting of outbreaks
Authors: ENTWISTLE J. C. , DIXON A. F. G.
Published: February 2008

Sitobion avenaewas introduced into areas within a field of winter wheat in Norfolk in mid‐May 1985, when the indigenous population was negligible. Aphid numbers in these areas increased for the first 3 wk and declined for the next 4. A secondS. avenueintroduction into the same areas and into previously uninfested areas was carried out 5 wk after the first introduction, when the crop was at ear emergence complete (G.S. 59). This increased aphid numbers in the previously uninfested areas, but numbers in the previously infested areas continued to decline to below the level in control areas during the subsequent 2 wk. Populations in all areas then increased rapidly to a maximum, followed by a rapid final decline. Monitoring of the aphid and natural enemy populations, and caging aphids onto the crop, revealed that the principal cause of the population decline around G.S. 59 was predation by syrphids. The relevance of these findings to the problem of forecastingS. avenaeoutbreaks is discussed, and a general explanation for cereal aphid outbreaks is put forward.
Distribution and infectivity of yellowing viruses in field‐grown sugar‐beet plants
Authors: SMITH HELEN G.
Published: February 2008

Beet yellows virus (BYV) and beet mild yellowing virus (BMYV) are introduced to sugar‐beet root crops in spring by winged aphids, and are spread within the crops from these foci of infection. The rate of spread is likely to be influenced by the speed with which the initially inoculated plants become sources of infection. Studies reported in this paper showed that when field‐grown sugar beet were inoculated at the 2–4 leaf stage with BYV, the virus was detected in the youngest leaves after 1 wk, in all leaves after 2 wk and was readily acquired and transmitted by Myzus persicae from these infected leaves. In contrast BMYV multiplied and spread more slowly in plants inoculated at the 2–4 leaf stage, and was not acquired and transmitted by M. persicae very efficiently early in the season. When plants were inoculated at the 15–20 leaf stage there was less difference between the two viruses. The consequences of the observations in relation to aphid control are discussed.
Glucosinolates in oilseed rape (Brassica napus) and the incidence of pollen beetles (Meligethes aeneus)
Authors: MILFORD G. F. J. , PORTER A. J. R. , FIELDSEND JANE K. , MILLER CLAIRE A. , LEACH J. E. , WILLIAMS INGRID H.
Published: February 2008

During an early stage of migration into a field of oilseed rape in the spring of 1988, more pollen beetles were observed on the double‐low variety, Ariana, than on the adjacent single‐low varieties, Bienvenu and Mikado. More beetles were found on open flowers on terminal racemes than on yellow and green flower buds on lateral racemes.

Five alkenyl, three indolyl and two aromatic glucosinolates were identified in the floral tissues of oilseed rape. The major compounds were progoitrin (2‐OH, 3‐butenyl) and glucobrassicanapin (4‐pentenyl). There were no differences in the types and concentrations of glucosinolates present in the terminal and lateral racemes of any variety, and only small differences between single‐ and double‐low varieties. Concentrations of glucosinolates in floral tissues of crops grown with a little nitrogen were twice those of well‐fertilised crops. There was no association between the number and distribution of pollen beetles on plants and the amounts or types of glucosinolates present in floral tissues.
Inheritance pattern of downy mildew resistance in advanced generations of sorghum*
Authors: REDDY BELUM V. S. , MUGHOGHO L. K. , NARAYANA Y. D. , NICODEMUS K. D. , STENHOUSE J. W.
Published: February 2008

In a project aimed to incorporate downy mildew resistance into sorghum hybrid seed parents, we screened F4 and F5 families for resistance to the ICRISAT Centre isolate of the pathogen using a greenhouse seedling screening technique. The families originated from a cross of 296B (susceptible) and IS 18757 [(QL‐3) resistant]. The F4s were obtained from agronomic selection in F2s and F3s, and the F5 families from advancing plants identified as resistant in segregating F4 families.

The resistant plants were more than double the number of susceptible plants in the F4 and almost so in the F5 suggesting that resistance to downy mildew was dominant. Of the four genetic models examined (a single‐locus model and three two‐locus models with complementary, inhibitory, and a combination of complementary and inhibitory interactions), the two‐locus model with independent segregation and a combination of complementary and inhibitory inter‐allelic interaction appeared to be most appropriate in explaining the segregation patterns within and among F4 and F5 families. Accordingly, for resistance to P. sorghi, the suggested genotypes for IS 18757 is PlaPlaPlbPlb and for 296B is PlaPlaPlbPlb.
A simulation model of Avena fatua L. (wild‐oat) growth and development
Authors: WEAVER S. E. , KROPFF M. J. , COUSENS R.
Published: February 2008

An eco‐physiological simulation model of the growth and development of Avena fatua was parameterised and tested. The model simulates growth ofA. fatua, in kg dry matter ha‐1 day‐1 from sowing to maturity as a function of irradiance, temperature and various species characteristics. Parameter values were derived from the literature and from field experiments, including both autumn and spring sowings of A. fatua over three years at two sites in southern England. With two exceptions, a single set of parameter values was sufficient to accurately simulate the emergence, growth and development of both autumn and spring cohorts over all years and sites. The two exceptions were the result of differences between autumn and spring cohorts of A. fatua in the rate of early leaf area growth and in the relationship between specific leaf area and developmental stage.
Dissemination and detection of peanut clump virus in groundnut seed
Authors: KONATE G. , BARRO N.
Published: February 2008

Experiments were done to assess the role of seed‐transmission in the dissemination of peanut clump virus (PCV) in groundnut (Arachis hypogea L.), and the usefulness of enzyme‐linked immunosorbent assay (ELISA) for detecting the virus in infected groundnut seed. The virus was present in 7.5% of seedling progeny from infected plants and could be detected in 16.5% of the seeds by ELISA. When groundnut seeds were grown in a field contaminated by the virus, it was shown that by roguing the infected plants, only 0.1% of the seeds from the remaining plants contained the virus. It was also established that the level of contamination of seeds by the virus was inversely proportional to the seed size.
A rapid serological test for detecting Fusarium oxysporum f.sp. narcissi in Narcissus
Authors: LINFIELD CHRISTINE A.
Published: February 2008

Polyclonal antiserum was elicited against a strain of Fusarium oxysporum f.sp. narcissi (GCRI80/26) and a specific and sensitive enzyme‐linked immunosorbent assay developed. Antiserum raised to cell wall fractions gave better recognition than that to cytoplasmic fractions. Recognition was equally good in artificially and naturally infected bulbs. Little cross‐reactivity in bulb tissue was shown by three other bulb‐rotting fungi. Nine isolates of F. oxysporum f.sp. narcissi from a wide geographic area gave similar results in an indirect ELISA of mycelial extracts, although some cross‐reactivity was observed with two other Fusarium spp. Four Fusarium spp. and four other fungi showed little cross‐reactivity. Ten days after inoculation the pathogen was readily detected in the base plate area of three Narcissus cultivars and points remote from the inoculation site in the most susceptible cultivar. A direct correlation was observed between positive results in the enzyme‐linked immunosorbent assay and recovery of the pathogen on selective medium.
The influence of temperature on the susceptibility of vine weevil, Otiorhynchus sulcatus (Fabricius) (Coleoptera: Curculionidae), larvae to Metarhizium anisopliae (Deuteromycotina: Hyphomycetes)
Authors: MOORHOUSE E R , GILLESPIE A T , CHARNLEY A K
Published: February 2008

Mortality of Otiorhynchus sulcatus (Fabricius) larvae at 10oC, 15oC, 20oC and 25oC following treatment with 107conidia ml“1suspensions of six Metarhizium anisopliae (Metschnikoff) Sorokin isolates was temperature dependent. In all cases, the LT50s were inversely related to temperature, but the nature of this response varied between isolates. Strain 101‐82 was the most virulent isolate at 25oC with an LT50 of 3.7 days, but it was the least virulent isolate at 15oC and it failed to kill any O. sulcatus larvae at 10oC. In contrast, strain 159‐83 had the lowest virulence at both 20oC and 25oC, whereas it was the most virulent isolate at 10oC with an LT50 of 20.0 days. The mortality rates followed a similar pattern and were positively related to temperature in all cases with the exception of strain 159‐83 at 25oC. Mycosis development was examined on larvae treated with strain 275‐86 and significant differences were obtained between all four temperatures. Sporulation commenced after approximately 2.75 days at 25oC, but took nearly 11 days at 10oC. The infection rates also varied between temperatures; sporulation occurred on 98% of the treated larvae at 25oC, but only on 93%, 87% and 49% of the larvae at 20oC, 15oC and 10oC, respectively. The results of these bioassays demonstrate that temperature has a significant effect on the virulence of M. anisopliae. The differences between fungal strains also emphasises the importance of selecting isolates for specific situations on the basis of their temperature profiles.
Controlling potato tuber blemish diseases on cv. Estima with chemical and non‐chemical methods
Authors: HIDE G A , BOORER KATHRYN J , HALL SHARON M
Published: February 2008

In 3 years, seed tubers were treated or not with imazalil in March or April, sprouted and planted in field experiments. Tubers were harvested on several dates and cured under different conditions for 2 wk, or not cured, before storage for 6 months. In some years effects of irrigation, seed tuber size and seed stock were tested.

Fungicide seed treatment decreased silver scurf, and was most effective in 1989 when the seed had little infection and the season was dry, but the treatment increased black dot. Silver scurf and black dot were decreased by harvesting early and also by drying tubers before storage (dry curing), and these practices also sometimes decreased black scurf and skin spot. The effects of fungicide seed treatment and of dry curing were greater the earlier the tubers were harvested. Irrigation decreased silver scurf and in one year decreased black scurf but greatly increased black dot. Silver scurf, black dot and skin spot were more common on tubers from large than small seed whereas black scurf was most common on tubers from small seed.

In 2 years tubers were affected with a brown superficial blemish (golding blotch). This developed on the undersides of tubers in soil and was decreased by irrigation. Its cause is not known.
Sitona weevils (Coleoptera: Curculionidae) as agents for rapid transfer of nitrogen from white clover (Trifolium repens L.) to perennial ryegrass (Lolium perenne L.)
Authors: MURRAY P J , HATCH D J
Published: February 2008

The effects of root feeding by larvae of Sitona hispidulus (F.) (a common weevil pest of white clover) on the rate of transfer of nitrogen between plants of white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.) were investigated using a nutrient slant board technique. Clover plants, labelled with 15N were grown adjacent to ryegrass plants and were either infested with Sitona larvae or not infested. Ryegrass plants associated with the infested clover plants had a significantly higher dry matter yield and nitrogen content (75% and 74% respectively) than the uninvested plants, after 33 days exposure to insect herbivory. It was concluded that root feeding insects could play an important role in the cycling of nitrogen in grass/clover swards.
Movement of barley mild mosaic and barley yellow mosaic viruses in leaves and roots of barley
Authors: SCHENK P M. , ANTONIW J F. , BATISTA M deF , JACOBI V. , ADAMS M J. , STEINBISS H H.
Published: February 2008

Leaves of barley plants were mechanically inoculated with barley mild mosaic virus (BaMMV) and roots were inoculated using viruliferous zoospores of the fungus vector Polymyxa graminis. At intervals after inoculation, leaves and roots were tested by different methods to detect virus coat protein (ELISA or Western blot) or nucleic acid (slot‐blot or reverse transcriptase‐PCR). Following inoculation with zoospores, virus could be detected in roots after 1 wk (Western blot or PCR) but not until 3–4 wk by ELISA. Virus moved to leaves in 5–6 wk but, except at temperatures of about 20°C, plants had to be cut back close to soil level to stimulate virus movement. Following mechanical inoculation, virus could be detected in leaves of a susceptible cultivar within 5 days by ELISA and 3 days by the other methods. Western blots and PCR showed that virus was present in the roots by 5 days. BaMMV was not detected by any method in leaves or roots of a resistant cultivar, indicating that the virus did not multiply in it. When leaves were mechanically inoculated on a small area only, BaMMV capsid protein was detected below the inoculated site at 4 days and in young growing leaves and roots at 13 days after inoculation but never above the inoculation site or in older leaves. After stem extension began, new leaves of infected plants were free of symptoms. The results are compared to observations of plants infected with barley yellow mosaic virus (BaYMV). It is proposed that movement of BaMMV and BaYMV is strongly related to the phloem transport and to the source‐sink pattern of winter barley plants.
Evaluation of an enzyme‐linked immunosorbent assay for detection of Mycosphaerella pinodes in pea seeds
Authors: Faris‐Mokaiesh S. , Corbiere R. , Lyons N F. , Spire D.
Published: February 2008

A polyclonal antiserum was raised against soluble mycelial extracts of Mycosphaerella pinodes aiming at pathogen detection in infected pea seeds by ELISA. When tested against the homologous antigen, it allowed the detection of 5 ng fungal soluble protein ml‐1 buffer, by double‐antibody sandwich ELISA (DAS‐ELISA). Positive reactions were obtained with isolates of M. pinodes of wide geographical origins but also with all tested isolates of Ascochyta pisi and Phoma medicaginis var. pinodella, two closely related pathogens forming with the target organism the Ascochyta complex. Out of the 11 other genera of pea seed‐borne fungi tested, only two (Alternaria sp. and Stemphylium sp.) cross‐reacted strongly by both antigen‐coated plate (ACP‐ELISA) and DAS‐ELISA. Cross‐absorption of the crude antiserum could not lead to a species‐specific antiserum; however, a combination of P. medicaginis var. pinodella and Stemphylium sp. antigens resulted in an antiserum preferentially recognising A. pisi and M. pinodes. The cross‐absorbed antiserum detected 50 and 500 ng of fungal protein ml‐1 buffer and healthy seed extracts respectively. DAS‐ELISA proved suitable for the detection and quantification of M. pinodes in infected pea seeds tested singly.
The effect on yield in courgette and marrow of the mild strain of zucchini yellow mosaic virus used for cross‐protection
Authors: SPENCE N J , MEAD A. , MILLER A. , SHAW E D , WALKEY D G A
Published: February 2008

The effects on yield in courgette and marrow (Cucurbita pepo) crops resulting from inoculation with the mild strain of zucchini yellow mosaic virus (ZYMV:WK), have been determined in polythene‐house trials and in three years of outdoor, commercial field trials. In polythene‐house trials ZYMV:WK inoculated plants were up to 10 days later in flowering than uninoculated plants and their cumulative yields were between 5% and 26% less than uninoculated plants depending on the cultivar. In most field trials cumulative yields from inoculated plants were between 4% and 38% less than uninoculated plants depending on the site and cultivar, but in one trial the yield was 7% higher from inoculated plants. In all experiments, courgette and marrow fruits harvested from ZYMV:WK inoculated plants were symptomless and indistinguishable from fruit harvested from uninoculated plants. The mild leaf symptoms induced by ZYMV:WK infection did not intensify to severe leaf symptoms and where there were natural outbreaks of severe ZYMV infection, fruits from inoculated plants remained symptomless whilst those from uninoculated plants were severely affected and unmarketable.
Gene transfer between canola (Brassica napus L. and B. campestris L.) and related weed species
Authors: BROWN JACK , BROWN ANGELA P
Published: February 2008

Brassica species are particularly receptive to gene transformation techniques. There now exists canola genotypes with transgenic herbicide resistance for glyphosate, imidazolinone, sulfonylurea and glufosinate herbicides. The main concern of introducing such herbicide resistance into commercial agriculture is the introgression of the engineered gene to related weed species. The potential of gene transfer between canola (Brassica napus and B. campestris) and related weed species was determined by hand pollination under controlled greenhouse conditions. Canola was used as both male and female parent in crosses to the related weed species collected in the Inland Northwest region of the United States. Weed species used included: field mustard (B. rapa), wild mustard (S. arvensis) and black mustard (B. nigra). Biological and cytological aspects necessary for successful hybrid seed production were investigated including: pollen germination on the stigma; pollen tube growth down the style; attraction of pollen tubes to the ovule; ovule fertilisation; embryo and endosperm developmental stages. Pollen germination was observed in all 25 hybrid combinations. Pollen tubes were found in the ovary of over 80% of combinations. About 30% of the hybrid combinations developed to the heart stage of embryo development or further. In an additional study involving transgenic glufosinate herbicide resistant B. napus and field mustard it was found that hybrids occurred with relatively high frequency, hybrids exhibited glufosinate herbicide resistance and a small proportion of hybrids produced self fertile seeds. These fertile plants were found to backcross to either canola or weed parent.
Field and laboratory studies on the effects of temperature on the development of the carrot fly (Psila rosae F.)
Authors: COLLIER ROSEMARY H. , FINCH STAN
Published: February 2008

The thermal requirements for the pre‐oviposition period, egg, larval, pupal and adult stages of the carrot fly were measured under field conditions and at a range of constant temperatures in the laboratory.

In the laboratory, the pre‐oviposition period lasted from 4 days at 24oC to 28 days at 9oC. In general, female carrot flies laid about 20–40 eggs in each batch. Once the first eggs had been laid, subsequent batches were laid after an average of 3 days at 24oC to 7 days at 11.5oC. The numbers of days required for egg, larval and pupal development ranged from 5, 31 and 24 days respectively at 21.5oC to 25, 145 and 84 days respectively at 9oC. Under laboratory conditions, complete development from egg to adult required from 60 days at 21.5oC to 254 days at 9oC.

Newly‐formed carrot fly pupae were exposed to temperatures of 22–30oC for various 5–10 day periods during pupal development. Exposure to temperatures of 24oC and 26oC caused some, and exposure to 28oC and 30oC caused all, of the pupae to delay development. Pupae were sensitive to high temperatures only for approximately 4–10 days after pupation.

Under field conditions between mid‐May and early September, full carrot fly development (egg‐adult) took 84–100 days. The numbers of day‐degrees required (base temperatures of 2oC and 4oC) for carrot fly development in the laboratory and in the field were similar for egg hatching but not for the pre‐oviposition period or for egg‐adult development. The thermal requirement for fly development in the field varied between inoculation dates, fewest day‐degrees being required when development was rapid.
Selection of Cassida spp. from southern Africa for the biological control of Chrysanthemoides monilifera in Australia
Authors: KLEINJAN C A. , SCOTT J K.
Published: February 2008

Four species of tortoise beetle (Chrysomelidae, Cassidinae)(Cassida spatiosaSpaeth and three undescribedCassidaspecies, labelled 1. 2 and 3) from South Africa, were assessed as potential biological control agents againstChrysanthemoides monilifera monilifera(L.) T. Norl. andC. m. rotundata(DC.) T. Norl. These southern African plants are important weeds of conservation areas in Australia. In South Africa,Cassida spatiosawas found feeding onC monilifera subcanescens(DC.) T. Norl.,Cassidasp. 1 onChrysanthemoides monilifera pisifera(L.) T. Norl. andC m. monilifera, Cassidasp. 2 onC m. pisiferaandChrysanthemoides incana(Burm.f.) T. Norl. andCassidasp. 3 on C.m. rotundata.The life cycle of each species was completed in about three months on the leaves of the host.Cassidaspecies 1, 2 and 3 were tested against eight species of plant and only fed and completed development onChrysanthemoidesspecies and the related species.Calendula officinalisL.Cassidaspecies 1 and 3 showed no preference betweenCalendula officinalisandChrysanthemoidesspecies for oviposition.Cassidaspecies 3 was selected for further assessment as a biological control agent based on match to the host subspecies and target climate in Australia.