Biological Control of Take-all by Phialophora radicicola Cain1

Biological control of take-all by Phialophora radicicola Cain and similar fungi is reviewed, and new evidence is presented on the possible role of hyper-parasites, like Pythium oligandrum Drechsler, to augment this. Phialophora radicicola var. graminicola Deacon is abundant in British grasslands. Its role in biological control of take-all has been demonstrated in the glasshouse with natural soils and natural population levels of this control agent. Also there is much circumstantial evidence for its beneficial role in agriculture, especially in cereal monoculture following grass crops, and in natural and amenity grasslands. Some other similar fungi control take-all in the glasshouse, but their roles in current agricultural practice are not known. The take-all fungus, itself, can reduce infection of roots by P. radicicola, so there is a dynamic interaction between these fungi. This is affected by host type, relative inoculum potentials of the fungi, and possibly by environmental conditions. By careful manipulation, therefore, it might be possible to control take-all under a wide range of field conditions. The chief role of P. radicicola and similar fungi is to delay establishment of severe take-all early in cereal monoculture, rather than to combat an existing high disease level. It may therefore be desirable to combine different biocontrols, and hyperparasites like Pythium oligandrum may be important in this respect. This fungus was tested against varieties of Gaeumannomyces graminis Arx & Olivier and Phialophora radicicola in the laboratory; the host responses differed greatly, from marked susceptibility (P. radicicola var. radicicola) to almost complete resistance (G. graminis var. graminis). Hence, P. oligandrum might be used to alter relative population levels of these fungi in the field, but first its behaviour in natural soils must be studied.     

Possibilités et limites de la monoculture en relation avec l'application de diverses mesures culturales1

La monoculture du blé d'automne entraîn des baisses de rendement qui ne semblent pas dues uniquement à des causes sanitaires. Ces diminutions de rendement peuvent être atténuées par l'application de différentes mesures culturales. Un renforcement de la fumure azotée et, dans les parcelles exposées au piétin-verse, un traitement au bénomyl au début de la montaison, constituent les mesures les plus efficaces. Les effets négatifs de la monoculture ont été plus marqués aprés labour qu'en semis direct.     

Erwinia carotovora (Jones) Bergey et al. var. atroseptica (Hellmers et Dowson) Dye. Seed Tuber Infection Versus Symptom Expression in the Field1

Based on the time that symptoms of blackleg become evident in the field and the various ways of inoculation, it is concluded that the spread of symptom expression is due to the depth at which the bacteria penetrate into the interior of the tubers. Moreover, it is demonstrated that it is not the closed lenticels which prevent penetration, but the absence of a waterfilm in the intercellular spaces of the tuber tissue.     

Experience of Ring Rot Caused by Corynebacterium sepedonicum(Spieck. et Kotth.) Skapt. et Burkh. in Sweden. Particularly Detection of the Disease in its Latent Form)1

As it is difficult to detect ring rot in its latent form as well as in badly decayed tubers and in potato haulm, a diagnostic technique has been developed. With the help of a Turmix blender and a little water, a suspension is made of the suspected material. The suspension is inoculated into eggplants. Gram-staining of bacteria in sap from petioles of leaves showing symptoms is used to confirm the diagnosis. Some results obtained with this method applied on potatoes and potato haulm are described.     

Chemotaxonomy of Compositae related to their host suitability for Pratylenchus penetrans

Experimental work and a survey of literature gave data on the effects of 175 Compositate on populations ofPratylenchus penetrans in the soil. Nearly 70 Compositae effectively suppress populations ofP. penetrans. It is shown that a close relationship exists between this suppressing feature and the chemotaxonomy of the Compositae.Samenvatting Eigen onderzoek aangevuld met gegevens uit de literatuur gaf informatie over de invloed van 175 Composieten op populaties vanPratylenchus penetrans in de grond. Bijna 70 soorten verlaagden deze dichtheden (Tabel 1). Het betreft soorten van de geslachtenGrindelia, Solidago, Coreopsis, Eclipta, Rudbeckia, Verbesina, Melampodium, Parthenium, Iva, Ambrosia, Milleria, Baeria, Schkuhria, Eriophyllum, Chaenactis, Helenium, Gaillardia, Tagetes, Arctotis, Gazania, Berkheya, Didelta, Echinops enUrospermum. Er is een duidelijk verband tussen de taxonomische indeling van Composieten en deze eigenschap. Bijna alle getoetste soorten van de subtribus Ambrosiinae, Heleniinae, Arctotinae, Gorteriinae en Echinopinae reduceerden populaties vanP. penetrans. In sommige geslachten zoalsSolidago, Coreopsis, Rudbeckia enMelampodium veroorzaakten slechts een of enkele getoetste soorten dit effect.Van de 16 Composieten, waarvan bekend is dat zij -terthienyl in hun wortels bevatten, verlaagden er 15 dichtheden vanPratylenchus. Vrijwel hetzelfde geldt voor Composieten met 5-(3-buteen-1-ynyl)-2,2-bithienyl in hun wortels (Tabel 1). Ook de aanwezigheid in een aantal andere Composieten van een groep rode dithio-acetyleen-verbindingen met waarschijnlijk nematicide eigenschappen in vitro, komt goed overeen met de eigenschap om dichtheden vanP. penetrans in de grond te verminderen.     

Connaissances récentes concernant la faune des pruneaux dans les stockages traditionnels

L'étude faunistique des ravageurs des pruneaux stockés a permis de faire l'inventaire des différentes espèces présentes et d'établir une évaluation quantitative de leurs populations à partir de 2 méthodes de prélévement (piégeage, tri d'échantillons).
Par ordre d'importance on peut citer: les acariens: Carpoglyphus lactis L. (Glycyphagidae), les coléopteres: Carpophilus ligneus Murr., C. hemipterus L. (Nitidulidae) et Henoticus californicus Mann. (Cryptophagidae) et les lépidopteres Nemapogon granella L. (Tineidae), Plodia interpunctella Hübn. (Pyralidae).
Les ravageurs primaires s'attaquent aux pruneaux sains: ils sont responsables des principaux dégáts et comprennent Carpophilus ligneus, C. hemipterus et N. granella . L'autre groupe est formé des ravageurs secondaires, qui s'installent sur des pruneaux déjá attaqués par des insectes ou des micro-organismes. On trouve dans cette catégorie Carpoglyphus lactis et H. calilornicus .
Les conditions optimales au développement de ces insectes et de ces acariens sont réunies, lorsque la teneur en eau de la pulpe du pruneau est égale ou supérieure à 20 %, la température ambiante clans l'entrepôt supérieure à 15°C et l'hygrometrie relative variant suivant Ies espéces entre 50 et 85 %.     

Biology of the Gaeumannomyces graminis Arx & Olivier/Phialophora radicicola Cain Complex on Roots of the Gramineae

Biological characteristics of the varieties of Gaeumannomyces graminis Arx & Olivier and Phialophora radicicola Cain are reviewed. They include: 1) pathogenicity to roots of cereals; 2) growth on living stem tissues; 3) type of fungal growth-cessation structure formed on or in the host. Together, these provide a simple means of characterizing isolates and standard methods for assessing them are presented.
The role of pigmented cells and tissues (growth-cessation structures) in host penetration is questioned, since they are seldom associated with a progressive infection by G. graminis or P. radicicola . However, they are a taxonomic aid, especially as they are now known to form on cellophane overlying agar.
New evidence is presented on factors affecting conidiation by these fungi. Flooding colonies with distilled water induced formation of conidia by G. graminis var. tritici Walker, P. radicicola var. radicicola (British isolates but not the type) and P. radicicola var. graminicola Deacon, whereas none formed on corresponding unflooded agar plates. Conidia were usually much larger and germinated readily when they formed in response to flooding; many of these fungi therefore have 2 conidial types, distinct in both morphology and behaviour. Preliminary results suggest that biotin and the form of nitrogen also affect the type of conidium formed by P. radicicola var. radicicola .     

Method of colostomy and cannulation of the chicken

1. A procedure for colostomising birds from 3 weeks to 5 months of age is described.

2. A plastic cannula was inserted into the fistula 10 d after surgery to keep it open.

3. Provided that the cannula was changed regularly at 10‐d intervals there was no constipation or dilation of the intestine.     

The hen's egg: Shell cracking at impact on a heavy,stiff body and factors that affect it

1. Eggs from hens of three strains were dropped on to a heavy, stiff, smooth, plane body with impact at the equator of the shell; the height of drop, h_c, just sufficient to produce shell failure was measured and the corresponding impact velocity, v_c, calculated.

2. A small but commercially important percentage of the well‐formed eggs of one strain cracked when h_c was as low as 3–3 mm and v_c 250 mm/s.

3. Characteristics of the egg found to affect h_c and v_c included the overall thickness of its shell, thickness of its weak inner shell layer and average shell curvature, all measured at the point of impact, and its weight; its age also had a small effect (additional to that mediated through loss of weight); so did the degree of shell ridging.

4. No effect of shell colour was found.

5. Shell damage was typically a single hair‐crack that ran either round the equator or towards a pole.     

Identification of immunoglobulins associated with complement fixation, agglutination, and low pH buffered antigen tests for brucellosis.

Serums from infected cattle, cattle with persistent postvaccinal antibody, and serologically "positive" noninfected cattle were fractionated into major immunoglobulin classes by diethylaminoethyl (DEAE)-cellulose chromatography and by sucrose density gradient centrifugation. Each fraction was assayed for anti-Brucella activity by standard tube-agglutination test (STT), buffered tube-agglutination test (BTT), and complement-fixation test (CF). In the serums from experimentally infected cattle, anti-Brucella antibody could be found by all tests in 6 DEAE fractions and in slow, fast, and sediment regions of the density gradient. Serums from cattle with persistent postvaccinal titers had STT activity in all 6 DEAE fractions, BTT activity in 5 fractions, and CF activity in only 1 fraction. The STT and BTT activities were found in the slow and the sediment regions of the gradient, whereas the CF activity was found only in the slow region. Serums from a chronically infected animal had STT and BTT activities in 2 DEAE fractions and CF activity in only 1. The STT, BTT, and CF activities were found in the slow and the sediment regions of the gradient. The principal antibody in serums from noninfected cattle was immunoglobulin M, which had all of the CF activity and most of the STT and BTT activities. Low levels of STT and BTT activities were found in 3 other DEAE fractions. Only STT and BTT activities were found in the fast and the sediment regions of the gradient.