Antibody-mediated response of pigeons to Argas polonicus larval feeding and characterization of larval antigen

Circulating antibodies to larval Argas polonicus antigen detected in the blood of pigeons by means of ELISA reach their highest level 3-6 days post-tick attachment. During 6-8 days post infestation when most larvae detach from their host, there is an abrupt drop of the antibody level in blood followed by second peak at day 10-15. During the secondary and subsequent infestations the dynamics of the antibody production is analogous, but the maximum absorbance values found are higher with each following infestation. This is in direct correlation with the growth of immune resistance of hosts. The transfer of immunoglobulins of resistant pigeons produces in naive hosts a partial resistance in a statistically significant (P less than 0.01) reduction of the number of engorged larvae, in the shortening of larval feeding period and in the decrease of their mean weight after feeding. However this resistance was significantly (P less than 0.01) less expressed than in naturally resistant pigeons during secondary infestation. The protracted effect on the duration of premoulting period and the percentage of moulted larvae manifested in larvae after secondary infestation was not apparent in molecular weight of approximately 19, 21, 23, 27, 45 and 165 kilodaltons, were recognized by serum of resistant pigeons.     

Effects of temperature,relative humidity and age of conidia on the incidence of spotting on gerbera flowers caused by Botrytis cinerea

In recent years, spotting of ray florets of gerbera flowers has become an important problem. This type of small necrotic lesions may occur before, but especially shortly after harvesting the flowers.Botrytis cinerea was easily isolated from such lesions. Inoculation withB. cinerea only gave typical necrotic lesions, when dry conidia were dusted on the flowers with a short period of high rh after inoculation. At 18–25 °C a high rh for at least 5 hours was necessary. Rotting of ray florets and receptacles byB. cinerea occurred when inoculated flowers were kept wet for a few days. Spots consist of one to several necrotic, usually epidermal cells. A single conidium could give rise to a necrotic lesion after germination. Germination of conidia and lesion formation occurred between 4 and 25 °C; at 30 °C, germination and lesion formation did not occur. Between 18 and 25 °C, many lesions became visible within 1 day after inoculation; at 4 °C it took 2 to 3 days before lesions could be seen. If kept dry, conidia ofB. cinerea remained ungerminated on ray florets of gerbera flowers and could be removed from the ray florets. Within 1 day at high rh, germination occurred and lesions were produced. Conidia ofB. cinerea, stored dry, were able to survive much longer than the lifetime of a gerbera flower. Even after storage at room temperature for up to 14 months, some conidia were able to germinate in vitro and on ray florets and induce the formation of lesions. Addition of gerbera pollen diffusate stimulated germination and lesion formation.     

The pyrethrins and related compounds. Part XXXV. Esters of aryl-substituted cyclopentane alcohols and analogues

Synthesis of a range of 1-, 2-and 3-phenyl, benzyl and phenethyl substituted cyclopentanols and cyclopentylmethyl alcohols and related unsaturated compounds is reported. Results of bioassays of their esters with known pyrethroidal acids against two species of insect lead to recognition of some structure-activity relationships in this series. The distance and relative orientation between the alcoholic and aryl functions appears crucial, but in other respects the nature of the spacer group between them is less important. The most effective alcoholic components are based on cyclopentenes.     

Virus elimination by meristem-tip culture from a range of Alstroemeria cultivars

A technique for virus elimination by meristem culture was developed for a range ofAlstroemeria cultivars. Meristems were excised from the rhizome tips and placed on a medium with indole-3-butyric acid, the required concentration of which was cultivar dependent: Six to eight weeks after dissection a shoot had formed which was transferred to a medium without growth regulators. On filter paper bridges, in a liquid medium, root formation was better than on a solid medium. In many cases a new rhizome developed. If not, the plantlet eventually died. Transfer into soil was more successful with the plantlets rooted in liquid medium than with those rooted in solid medium. Virus elimination was cultivar dependent, but in most cultivars plants resulting negatively in serological tests could be obtained. After repeated testing and selection for horticultural properties these plants may be used to start high quality mother plots.Samenvatting Een techniek werd ontwikkeld om door middel van meristeemcultuur virus te elimineren uit een aantalAlstroemeria cultivars. De meristemen werden uit de toppen van de rhizomen geprepareerd en op een voedingsbodem met IBA als auxine geplaatst. De IBA-concentratie nodig voor scheutvorming was afhankelijk van de cultivar. Na een periode van zes tot acht weken had het meristeem zich ontwikkeld tot een scheutje, dat vervolgens werd overgebracht op een voedingsbodem zonder groeistoffen. In ongeveer twee maanden vormden zich dan wortels. Deze wortelvorming was beter op een vloeibare voedingsbodem met papieren bruggetjes dan op een vaste voedingsbodem van agar. In veel, maar niet in alle gevallen, vormde zich ook een nieuw rhizoom. Indien geen rhizoom werd gevormd stierf de plant. Gewortelde plantjes groeiden beter in grond indien de beworteling op papieren bruggetjes had plaatsgevonden. Het succes van het elimineren van hetAlstroemeria-mozaïek virus hing af van de cultivar. Na herhaalde toetsing kunnen de negatief reagerende planten worden gebruikt voor de opbouw van een partij gezonde moederplanten. Op deze manier kan de kwaliteit van het uitgangsmateriaal vanAlstroemeria worden verbeterd.     

Effects of growth stage, leaf position and temperature on adult-plant resistance of wheat infected by Puccinia recondita f.sp. tritici

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

Effect of MBC fungicide tolerance on the fitness of Ophiostoma ulmi

Isolates of Ophiostoma ulmi with mutations conferring high or low levels of tolerance to MBC-generating fungicides were selected in the laboratory. Comparisons between these tolerant forms and their wild type equivalents indicated that the acquisition of a mutation in the tol locus was associated with decreased growth on agar medium. Pathogenicity and bark-colonizing ability were also found to be significantly reduced, indicating that the fitness of tolerant individuals was impaired.     

Relative importance of root rots of subterranean clover caused by Aphanomyces euteiches and Phytophthora clandestina

In a growth-cabinet experiment, Aphanomyces euteiches caused more severe root disease and greater reductions in root and shoot weights of subterranean clover cv. Mount Barker than Phytophthora clandestina in pasteurized sandy loam flooded with water for a 24-h period each week. A. euteiches also reduced plant growth more than P. clandestina in untreated sandy loam. In a similar experiment, both fungi caused the same amount of disease and reduction in growth of cv. Yarloop in pasteurized clay loam flooded for 24 h each week, and P. clandestina caused more disease and a greater decrease in plant growth than A. euteiches when the soil was flooded for 4 h each week. The pathogens did not interact positively in either soil. In an irrigated pasture, soil drenches with the fungicides metalaxyl and fenaminosulf together reduced both root rots to low levels and increased subterranean clover dry matter by 1 96, 0.50 and 1 20 t/ha in the autumn, winter and spring of 1985, respectively, and by 0.59 t/ha in the autumn of 1986. Results suggest that P. clandestina caused most of these losses in yield.     

Polygalacturonase isoenzymes and oxalic acid produced by Sclerotinia sclerotiorum in soybean hypocotyls as elicitors of glyceollin

The polygalacturonases (PG) and oxalic acid produced by Sclerotinia sclerotiorum in infected soybean hypocotyls were investigated as elicitors of the phytoalexin glyceollin I.Purification to homogeneity through isoelectrofocusing and ion-exchange fast protein liquid chromatography revealed three endo-PG isoenzymes (PG-I, PG-II and PG-IV) and one exo-PG (PG-III) in 6-day-old etiolated soybean hypocotyls infected with the B-24 isolate of S. sclerotiorum.PG-I and PG-III, in the range of concentrations tested (0·15–1·2 reducing units ml⁻¹), did not act as elicitors of glyceollin I synthesis. Some elicitor activity was shown by PG-II at 0·6–1·2 reducing units ml⁻¹. PG-IV, at lower doses (0·038–0·30 reducing units ml⁻¹), was even more effective in inducing phytoalexin synthesis. However higher concentrations of PG-IV induced tissue softening and decreased phytoalexin accumulation.PG-II and PG-IV released heat-stable elicitors from purified soybean cell walls supporting the evidence that uronides are intermediate inducers in elicitation by endo-PGs. Oxalic acid was an active elicitor of glyceollin I over the range of concentrations tested (0·31–20 m ) with the maximum at a concentration of 5 m . The inability of oxalic acid to release uronides from purified cell walls makes it unlikely that uronide intermediate elicitors are involved in elicitation by oxalic acid.     

The pyrethrins and related compounds. Part XXXIV. Optimisation of insecticidal activity in non-esters

Optimisation of activity within the structural constraints defined by the preceding work, by varying the substituents on phenyl in the acid fragment (10 variations), the nature of the group fulfilling the dimethyl function (three variations), the central linking group (four variations) and the presence or absence of a 4-fluoro substituent in the alcohol fragment, has led to achiral compounds as active as bioresmethrin against houseflies and mustard beetles. Statistical analysis of the effects has shown that particular combinations, for instance the cyclopropyl form of dimethyl with a central E-alkene group (but not a central ether group), lead to higher activity than expected. 4-Fluoro substitution enhances activity more strongly against mustard beetles. Difluorocyclopropyl compounds are on average slightly more active than cyclopropyl analogues.     

Leaching potential and decomposition of fluroxypyr in Swedish soils under field conditions

The mobility and decomposition of the herbicide fluroxypyr (4-amino-3,5-dichloro-6-fluoro-2-pyridyloxyacetic acid) was studied under field conditions in a sandy soil and a clay soil. Leachate was collected in lysimeters with undisturbed soil (sand) and in tile-drained plots (clay). Soil samples to a depth of one metre were also collected in both soils to characterize the temporal depth distribution of fluroxypyr in the profiles. The herbicide was applied as the I-methylheptyl ester of fluroxypyr at two rates, 187.5 and 375.0 g a.e. ha^?1, representing the normal and double the dose of the compound used for spring cereals. Some lysimeters received supplementary watering. Only two leachate samples (one from each soil) had concentrations of fluroxypyr above the detection limit (1 μg litre^?1), i.e. 2 and 5 μg litre^?1. Both samples were collected within two months after application, when less than 2 mm of drainage had been collected. The methylheptyl ester of fluroxypyr was not found in any of the samples. Fluroxypyr levels above the detection limit in soil (5 μg kg^?1 dry soil), were never found below the topsoil (0.2 m) in the clay profile, while, in the sandy profile, levels just above the detection limit were found occasionally in deeper soil layers. Concentrations were reduced to undetectable or very low levels within three months after spraying.