bluuebunny/crossref_metadata_2025_split huggingface dataset:
AN ANALYSIS OF COMPETITION BETWEEN BARLEY AND WHITE PERSICARIA: I. THE EFFECTS ON GROWTH
Authors: ASPINALL D. , MILTHORPE F. L. 
Published: February 2008

Barley and white persicaria (Polygonum lapathifolium L.) were grown in pure and mixed populations of varying density in sand culture in a glasshouse. The leaf areas and dry weights of leaves, stems and roots were determined at intervals. During the phase of vegetative growth the addition of dry matter by barley was unaffected, although tillering was reduced, by competition from dense stands of white persicaria, whereas the growth of white persicaria was reduced by low densities of barley. The decline in leaf area and reduction in root growth of barley with the onset of flowering was accompanied by increased growth of white persicaria with the production of branches from the upper axillary buds. These flowered and set abundant seed. This behaviour probably accounts for the persistence of this weed in arable rotations.The greater competitive ability of barley may be attributed to its larger embryo, giving much larger plants at emergence. The intrinsic relative growth rate of white persicaria is as high as, or higher than, that of barley and falls more slowly with time. This advantage is not sufficient to offset the initial differences in size while barley is vegetative. The larger embryo size of barley also determines the more intense competition that exists between plants of this species than between plants of white persicaria at similar densities and times from germination. With equal weights of produce per pot (or unit area) the intensity of competition within each species appears to be similar.It is emphasized that the course of growth with time, rather than weight‐density relationships at given points of time, must be followed in order to understand the influence of density. Two functions of the relative growth rate with time are examined.
STUDIES ON PLANT GROWTH‐REGULATING SUBSTANCES. XIII CHLORO‐ AND METHYL‐SUBSTITUTED PHENOXYACETIC AND BENZOIC ACIDS
Authors: PYBUS MARY B. , SMITH MARGARET S. , WAIN R. L. , WIGHTMAN F. 
Published: February 2008

The physiological activity of complete series of mono‐ and di‐substituted chloro‐and methyl‐phenoxyacetic and benzoic acids have been investigated using the wheat cylinder, pea segment and pea curvature tests. In the phenoxyacetic acids, high activity was associated with substitution in the 3‐, 4‐, 2:4‐, 2:5‐ and 3:4‐positions and in general, chlorine had a greater effect than methyl in conferring activity.With the benzoic acids, 2:3‐, 2:5‐ and 2:6‐, disubstitution gave active compounds, the chloro‐derivatives again being the more active. The 2:5‐compound was the most active in the dichloro‐ series, all members of which were less active than the 2:3:6‐trichloro‐ and 2:3:5:6‐tetrachloro‐acids. Benzoic acids substituted in the 4‐ position were either inactive or exhibited only weak growth‐promoting activity.The results are discussed in relation to recent theories which attempt to relate growth‐promoting activity with the position of substituents in the aromatic ring.
STUDIES IN THE BACTERIAL DISEASES OF SUDAN CROPS: III. ON THE OCCURRENCE, HOST RANGE AND TAXONOMY OF THE BACTERIA CAUSING LEAF BLIGHT DISEASES OF CERTAIN LEGUMINOUS PLANTS
Authors: SABET K. A. 
Published: February 2008

The bacterial leaf blights of dolichos bean (Dolichos lablab L.), soybean (Glycine soja Sieb. and Zucc.), catjang cowpea (Vigna unguiculata (L.) Walp.), lucerne (Medicago sativa L.) and three species of senna (Cassia L.) were investigated and found to be caused by Xanthomonas phaseoli (Smith) Dowson, X. phaseoli var. sojense (Hedges) Starr & Burkholder, X. vignicola Burkholder, X. alfalfae Riker, Jones & Davis and X. cassiae Kulkarni, Patel & Dhande, respectively. None of these diseases has been investigated before in the Sudan and the lucerne disease had not been previously reported from this country.A comparative study which included several strains of the above bacteria as well as X. phaseoli var. fuscans (Burkholder) Starr & Burkholder, X. cajani Kulkarni, Patel & Abhyankar, and X. tamarindi Patel, Bhatt & Kulkarni, showed that the organisms were indistinguishable by the usual bacteriological procedures and the minute differences in certain biochemical characters were considered of little or no diagnostic value. Cross‐inoculations revealed that the host ranges of these pathogens, with the exception of X. cajani and X. tamarindi overlapped. The latter two organisms infected only their original hosts, viz. Cajanus cajan (L.) Millsp. and Tamarindus indica L., respectively. Where a particular host was infected by more than one pathogen, the symptoms and effects they produced on that host were similar in every respect except in the case of X. vignicola when infecting Phaseolus vulgaris L. and Dolichos lablab. In this exceptional case the mature spots were dry and white, not conforming to the usual russet or dark‐brown, haloed spots produced by other bacteria. Infection in most cases first appeared as minute dark‐green more or less watersoaked spots which generally developed on all parts of the plants including the stems, leaves and pods.The systematic position of the pathogens under investigation was reconsidered and for the reasons discussed below all the bacteria included in the study were reduced to special forms of X. phaseoli with the exception of X. phaseoli var. fuscans, the varietal rank of which has been maintained.
STUDIES IN THE BACTERIAL DISEASES OF SUDAN CROPS
Authors: SABET K. A. 
Published: February 2008

A bacterial disease of mahogany (Khaya senegalensis and K. grandifoliola) is reported for the first time. The disease causes rough or scabby leaf spots and small knob‐like cankers on the branches, which may die back as a result of infection. The symptoms of the disease differ to some extent with locality and host species. The causal organism is readily isolated from the leaves and young branches. Infection of the leaves takes place through the stomata at any time of the year. Several methods of inoculation into green shoots and woody branches were attempted but typical shoot infections were produced only when young green shoots were rubbed with the pathogen; the resulting blisters change to the typical knob‐like cankers when the shoots become woody.The disease is attributed to a new species of Xanthomonas, namely, X. khayae sp. nov., a description of which is given.
ANTIBACTERIAL SUBSTANCES IN SEED COATS AND THEIR ROLE IN THE INFECTION OF SWEET PEAS BY CORYNEBACTERIUM FASCIANS (TILFORD) DOWSON
Authors: JACOBS S. E. , DADD A. H. 
Published: February 2008

Antibacterial substances active against Corynebacterium fascians have been shown to be present in the coats of various seeds. There were considerable differences in activity between the seeds of different genera and species and between individual seeds of a single species. C. fascians also showed strain variation in sensitivity to the antibacterial substances of the seeds of any one species. An inverse relationship was demonstrated between the sensitivity of a strain to the sweet‐pea seed substances and its ability to infect sweet‐pea seedlings under laboratory conditions.
WILT OF LUCERNE CAUSED BY SPECIES OF VERTICILLIUM
Authors: ISAAC IVOR , LLOYD A. T. E. 
Published: February 2008

The incidence and symptoms of a disease of lucerne induced by Verticillium spp. are much less severe immediately after the crop has been first cut than later when the crop has matured. Infection becomes more marked as the season advances and the age of the ley increases, and cuts taken in the third harvest year are proving unprofitable.In cross‐inoculation studies the causal organisms of lucerne wilt, V. albo‐atrum and V. dahliae prove to be only mild pathogens to hop, potato, tomato and antirrhinum, and are not pathogenic to sainfoin and clover. The last two may therefore be cultivated as fodder crops in those areas most severely affected by lucerne wilt, but the cultivation of potatoes after lucerne should be discouraged, particularly if lucerne is to be sown in future years, since the potatoes might build up a reservoir of inoculum of the lucerne pathogen. In studies of host‐parasite relations it is shown that V. albo‐atrum and V. dahliae from lucerne, V. albo‐atrum from hop, V. tricorpus from tomato and V. nigrescens and V. nubilum from potato vary in their effects upon lucerne seedlings growing on agar media, V. albo‐atrum from lucerne being, as in the field, the most virulent and the only one to reach the xylem vessels under the conditions of the experiments.The dressings Agrosan‐GN (containing mercury) and Fernasan (containing thiram) are toxic both to spores of Verticillium on lucerne seed coats and to infected plant material carried with seed, and although they are also toxic in vitro to Rhizobium mellelotus this did not prevent dressed seeds which had been inoculated with the bacterium from developing into healthy seedlings bearing normal root‐nodules.
EXPERIMENTS ON THE CONTROL OF BOTRYTIS DISEASE OF LETTUCE
Authors: WAY J. M. , KEYWORTH W. G. 
Published: February 2008

Experiments were made during 1955‐57 on the fungicidal control of Botrytis attack on lettuce, cv. May Queen, matured in frames from November to April, and cv. Trocadero Improved, grown as seedlings in frames from November to March and then matured in the field from March to June. The frame lettuce were treated during their whole period of growth and the field lettuce in the seedling stage only.On both types, 0.33% thiram sprays applied on up to five occasions gave the best control of disease: 5% tecnazene dust was effective on the frame crop, in 2 out of 3 years when applied to the plants and also when incorporated in the top soil at the rate of 15 g. per sq.yd. Tecnazene applications did not give a good control of the disease on the field crop. Sprays with 0.25% captan were almost as effective as the thiram treatments on the field lettuce but not on the frame crop.
FURTHER STUDIES OF TOBACCO ANTHRACNOSE IN SOUTHERN RHODESIA*
Authors: COLE J. S. 
Published: February 2008

Results of laboratory tests in Southern Rhodesia indicate that Colletotrichum tabacum, Böning, the causal organism of tobacco anthracnose, could survive in dry soil for 13–17 weeks and therefore might survive from one season to the next in dry soil in the absence of tobacco‐plant residue. The most favourable conditions for survival arose when soils of high organic content dried out fairly soon after being infected; soils which remained moist were the least favourable.Chemical control of soil infection with methyl bromide gas at 1 lb./100 sq.ft. was effective and not phytotoxic. Of the wettable powders used as soil disinfectants, thiram was more effective than zineb or maneb, but all were phytotoxic at certain concentrations. Phytotoxicity to tobacco, which took the form of stunting and poor root growth, varied with different commercial preparations of thiram and zineb.
METHODS OF CONTROLLING BLACK‐POD DISEASE (CAUSED BY PHYTOPHTHORA PALMIVORA) OF THEOBROMA CACAO IN NIGERIA
Authors: THOROLD C. A. 
Published: February 2008

Supplementary methods of controlling black‐pod disease (Phytophthora palmivora) of cocoa in Nigeria are considered, because fungicide application is not always economic.There is no evidence that resistance occurs within the local population of Amelonado‐type trees.Although the percentage of diseased pods was greater with trees closely spaced (5 times 5 ft. to 8 times 8 ft.), than with widely spaced trees (10 times 10 ft. to 15 times 15 ft.), the closer spacings often gave more healthy pods per acre.Loss of pods from black‐pod was decreased when trees were inspected frequently (alternate days) and infected pods were removed when showing the earliest symptoms. However, this procedure may not be economic, except when potential yields are relatively small (fewer than twelve pods per tree).Satisfactory control of black‐pod was obtained with copper fungicides, applied with either hand‐sprayers or a power‐sprayer. The monetary return depends on yield level, rather than on disease incidence or on spraying costs. It is recommended that spraying should be practised when the potential yield is twelve or more pods per tree.
THE BIOLOGY OF LETTUCE ROOT APHID
Authors: DUNN J. A. 
Published: February 2008

Lettuce root aphid, Pemphigus bursarius L., is a pest which sometimes causes considerable and widespread damage to crops of summer lettuce.Its favourite primary host is Lombardy poplar. On hatching in spring, from eggs that have overwintered on this host, the fundatrices cause the development of hollow, flask‐shaped galls on the leaf petioles. A fundatrix becomes enclosed within a gall, where it matures, and gives rise to between 100 and 250 young. These fundatrigeniae are all potential alatae and on developing wings leave the gall and migrate to lettuce and other secondary hosts; they reproduce rapidly.Lettuce sown between mid‐April and the end of May is most severely attacked, while lettuce sown in July escapes attack. The alternative secondary hosts belong to the Compositae, subfam. Liguliflorae, and although lettuce is preferred by the fundatrigeniae, Lapsana communis L. and Sonchus asper (L.) Hill often have big colonies of Pemphigus bursarius on their roots. The size of the mature apterae varies between hosts and is largest on lettuce and Sonchus asper.All winged alienicolae are sexuparae and fly back to poplar. Thus alternative secondary hosts are not reservoirs for lettuce‐infesting alatae.The sexuparae begin appearing on lettuce from about the last week in August. They generally come up to the soil surface and settle around the ‘collar’ of the host plant, to mature and develop wings. Having flown back to the primary host, the sexuparae seek out crevices in the bark where they produce arostrate sexuales. The ovipara contains one egg, and after mating she crawls as far into the bark crevice as possible and oviposits.
STUDIES ON THE PROPERTIES OF SOIL‐BORNE VIRUSES OF THE TOBACCO‐RATTLE TYPE OCCURRING IN SCOTLAND
Authors: CADMAN C. H. , HARRISON B. D. 
Published: February 2008

Soil‐borne viruses of the tobacco‐rattle type occur in sandy and peaty soils in many parts of Scotland, and infect many species of crop and weed plants, often only in the roots. They also occur in potato plants that have diseases of the stem‐mottle type. The viruses can be distinguished from other soil‐borne viruses occurring in Britain by the symptoms they cause in tobacco, Chenopodium amaranticolor and French bean.Some virus cultures (M types) multiplied readily and were easily transmitted by mechanical inoculation, whereas others (NM types) were transmitted mechanically only with difficulty. The behaviour of NM types remained constant during twenty successive subcultures. Only slight differences were noted between the symptoms caused by M and by NM types. A proportion of the single‐lesion isolates made from cultures of the M type behaved in every way like NM types: this proportion differed with different parent cultures. Single‐lesion isolates that were of the M type mostly caused somewhat different symptoms from their parent culture. All M types that were tested, including one from the Netherlands, were serologically related: however, different cultures, and different samples of the same culture propagated on different occasions, varied in antigenic constitution. Belladonna mosaic virus, described by Smith (1943) from England, was serologically related to tobacco rattle virus. Infection with each of several M types (including the Dutch culture), protected Nicotiana sylvestris plants from the effects of each of the others. NM types also protected N. sylvestris from the effects of the Dutch culture, but the latter was subsequently isolated from the tip leaves of such plants. Sap from plants infected with cultures of the M type contained characteristic rod‐shaped particles, but none was seen in sap from plants infected with NM types.In tobacco sap, M types had the following properties: thermal inactivation point, 80–85°C.; dilution end‐point, 10‐5‐10‐6; longevity in vitro, over 6 weeks; infectivity survived freezing and precipitation by ammonium sulphate, but not exposure to pH 3. In many of its properties, including the unusual one of failing to show photoreactivation after ultra‐violet irradiation, tobacco rattle virus resembles tobacco mosaic virus.Soil‐borne viruses occurring in Britain are classified into three groups, exemplified by tobacco necrosis, tomato black ring and tobacco rattle viruses.
THE PATTERN OF FIELD INFECTION OF POTATO BY THE BEET RINGSPOT STRAIN OF TOMATO BLACK‐RING, A SOIL‐BORNE VIRUS
Authors: HARRISON B. D. 
Published: February 2008

The potential importance of the beet ringspot strain of tomato black‐ring, a soil‐borne virus, was assessed by growing stocks of Kerr's Pink potato for 1 year on infested land and subsequently on uninfested land. The incidence of infection in two stocks was 39 and 8% in the first year on uninfested land, and 29 and 5% after 2 years.The virus was usually restricted to the roots of plants in the first year of infection, but a few plants showed black rings and spots in their leaves. In the second year, 20–55% of the plants grown from tubers set by symptomless, but infected, mother plants were infected: many of these showed leaf necrosis, others had stunted shoots, and cupped and distorted leaves; some were symptomless although systemically infected. In the third and fourth years, most of the progeny from plants which had symptoms or which were symptomless but systemically infected, contained the virus: nearly all such infected plants were stunted and distorted or were symptomless. Infection decreased the weight of tubers produced by plants with severe necrotic spotting but not the yield of plants with less necrosis. The number and weight of tubers per plant were decreased by 15 and 20% respectively, in symptomless systemically infected plants, and by 20 and 30% in stunted plants.
STUDIES ON PLANT CUTICLE: THE CUTIN COMPONENT OF THE CUTICLES OF LEAVES
Authors: ROBERTS MARGARET F. , BATT R. F. , MARTIN J. T. 
Published: February 2008

Methods are described for the chemical separation from leaf material of the ventral and dorsal surface cuticular membranes and for the determination of cutin in the membranes and leaf tissues.The cutin contents of the cuticular membranes separated from leaves of laurel, rhododendron, and Euonymus, and of leaf tissues of cauliflower, red beet, banana, tomato, strawberry and blackcurrant are reported. The relationship between the cutin and waxy components of the leaf cuticle is discussed, and earlier work on the development, structure and chemistry of the cuticle is reviewed.
STUDIES ON PLANT GROWTH‐REGULATING SUBSTANCES: CHLORO‐SUBSTITUTED PHENYLACETIC ACIDS
Authors: PYBUS MARY B. , WAIN R. L. , WIGHTMAN F. 
Published: February 2008

The plant growth‐regulating activity of all the mono‐ and di‐ chloro‐substituted phenylacetic acids, together with the 2:3:6‐trichloro‐ derivative, has been determined in the wheat cylinder, pea segment and pea curvature tests. Each of these compounds showed activity, the 2:3‐dichloro‐ and the 2:3:6‐trichloro‐ derivatives being extremely active. The 3:5‐dichloro‐ acid was inactive in the wheat test but showed moderate activity in the pea tests.All these findings are discussed in relation to the plant growth‐regulating activity of corresponding benzoic and phenoxyacetic acids.
THE INCIDENCE OF CERTAIN SEED‐BORNE DISEASES IN COMMERCIAL SEED SAMPLES
Authors: MARSHALL GILLIAN M. 
Published: February 2008

Commercial samples of celery seed have been submitted to the Official Seed Testing Station, Cambridge, from 1926 to 1958, for tests to determine the percentage infection by Septoria leaf spot (Septoria apii‐graveolentis and S. apii). The disease test and a method for estimating the viability of Septoria spores is described. The percentage of samples with less than 1% infection increased from 6.1% in 1926‐31 to 46.2% in 1953‐8 and the percentage of heavily infected samples decreased. But celery samples submitted since 1949 for purity and germination only were more heavily infected (in 1953‐8 only 26.3% had less than 1% infection). In 1957‐8, 78.8% of all celery seed samples tested showed evidence of infection with Septoria spp.No effect of variety or season on the incidence of disease was found during the survey.Six out of thirty samples were found to carry viable Septoria as estimated by germination of pycnidiospores.The similarity between the percentage germination of healthy seeds and those bearing Septoria pycnidia confirmed the general belief that Septoria spp. do not affect germination.
THE COLIFORM BACTERIA ASSOCIATED WITH POTATO BLACK‐LEG AND OTHER SOFT ROTS
Authors: GRAHAM D. C. , DOWSON W. J. 
Published: February 2008

Twelve glasshouse trials using twenty‐five isolates of coliform soft‐rot bacteria obtained from various countries showed that all the isolates produced typical black‐leg of potato at temperatures of 76° F. (24.5° C.) or over, while some of them could also produce the disease at temperatures below 66° F. (19° C.).Thus the isolates fall into two main groups of which the high‐temperature group originates mostly from tropical or subtropical countries or from plants grown in heated glasshouses, whereas the low‐temperature group is indigenous in the north temperate regions. The high‐temperature group comprises Pectobacterium carotovorum (Erwinia carotovora), P. carotovorum var. chrysanthemi (E. chrysanthemi) and P. carotovorum var. aroideae (E. aroideae). The low‐temperature group consists of one variety, P. carotovorum var. atrosepticum (E. atroseptica).This temperature relation provides a possible means of discovering the origin of the black‐leg pathogen in crops grown from Scottish seed in certain tropical or subtropical countries.As a result of this investigation it is considered that all soft‐rot coliform bacteria are varieties of a single species, P. carotovorum (Jones) Waldee.
COPPICING EXPERIMENTS ON THE SPREAD AND CONTROL OF CACAO SWOLLEN‐SHOOT DISEASE IN NIGERIA
Authors: THRESH J. M. , LISTER R. M. 
Published: February 2008

A coppicing technique was used to determine the incidence and distribution of latent and unrecognized infection around naturally occurring outbreaks of cacao swollen‐shoot virus disease in Western Nigeria. All the apparently healthy trees within 30 yards of eighty outbreaks of various sizes were coppiced and most of the infected stumps which regenerated showed symptoms within a year.The distribution of the infected stumps around thirty‐five outbreaks studied in detail is expressed by the equation log10I=a+bx. I is the estimated intensity of infection in the coppiced stumps at distance x from the nearest infected tree removed at the time of coppicing. The constant a determines the height of the peak of the infection gradient and increases with outbreak size, whereas the slope of the gradient, determined by the negative constant b, is similar around all outbreaks.The results are consistent with information on the movement of the mealybugs and spread of cacao swollen‐shoot virus in outbreaks. Moreover, they indicate that outbreaks are controlled most economically by removing all obviously infected trees and adjacent apparently healthy ones. Control does not require the destruction of all the trees around outbreaks up to a distance of 30 yards as done previously, but can be achieved by felling fewer trees, the actual number depending on the size of the outbreak.