Effects of temperature on infection of French bean leaves (Phaseolus vulgaris L.) by lucerne mosaic virus

The effect of temperature on the number of lesions and the time of their appearance was studied by inoculating French bean leaves (Phaseolus vulgaris L. cv. Perli?ka) with lucerne mosaic virus either 24 or 48 h before or, 24 or 48 h after they were exposed to various temperatures. The temperatures tested were 23, 25, 27, 30, 33 and 36° C. Before and after such exposures the plants were kept in a constant temperature of 25° C. By increasing the temperature before inoculation the number of lesions increased in comparison with the control. The optimal temperature for the maximum number of lesions is between 27° and 30° C. There is no significant difference between those experiments when the exposure time was 24 h or 48 h before inoculation. The same temperatures applied for 24 or 48 h after inoculation have a decreasing effect upon the number of lesions formed by LMV on French bean leaves. The decrease is 30 to 75%. In this case the first necrotic local lesions appeared 42 h after inoculation when exposed to higher temperatures above 27° C for 24 h, and 60 h after inoculation when exposed to these temperatures for 48 h. The shape of lesions varied a little in both cases as the pictures show.     

Effects of Leaf Age, Inoculum Dose and Freezing on Development of Chocolate Spot (Botrytis fabae) Lesions on Field Bean (Vicia faba) Leaves

Botrytis fabae spore suspensions containing c. 1, 10, 10², 10³, 10⁴, 10⁵, or 10⁶ spores/ml were used to inoculate 5, 17 or 30-day-old field bean leaves. The percentages of the leaf areas covered by, chocolate spot lesions and the percentages of the leaf areas bearing conidiophores were assessed 1, 6, 12, 14, and 19 days after inoculation. The percentage of the area covered by lesions and the percentage of the area bearing conidiophores (logit-transformed) increased linearly with increasing spore concentration (log₁₀-transformed). The proportions of leaf areas covered by lesions and bearing conidiophores were both greater on 17 and 30-day-old leaves than on 5-day-old leaves. The rate of lesion growth increased with both increasing inoculum dose and increasing leaf age. Generally there was no interaction between the effects of leaf age and the effects of inoculum dose on either lesion growth or sporulation. Two days after inoculation with suspensions of either 10⁴ or 10⁶ spores/ml, 7-day-old leaves grown at 15°C were transferred to –16°C or 2.5°C or kept at 15°C for 4 days. Two days later more spores had been produced on leaves which had been frozen (–16°C) than on, leaves kept at 2.5°C.     

THE EFFECT OF TEMPERATURE ON INFECTION WITH STRAINS OF CUCUMBER MOSAIC VIRUS

Cucumber mosaic virus strains differed in their ability to multiply in plants at 37° C. Some strains multiplied in inoculated leaves and produced systemic symptoms in plants at this temperature; plants systemically infected with one such strain remained infected after prolonged treatment at 37° C. Other strains did not appear to multiply in inoculated leaves at 37° C. and heat treatment was successful in freeing plants from infection with these. Tests with one strain of each type showed both to be rapidly inactivated in expressed sap at 37° C.
Strains of cucumber mosaic virus forming small necrotic local lesions in leaves of french bean var. Canadian Wonder, produced many fewer lesions in plants kept after inoculation at 25° C. for 24 hr. and then at 15° C. than in plants kept continuously at the lower temperature.     

SOME EFFECTS OF TEMPERATURE AND OF VIRUS INHIBITORS ON INFECTION OF FRENCH-BEAN LEAVES BY RED CLOVER MOTTLE VIRUS

Keeping French-bean plants before inoculation at 36, 32 or 28°C. for 1–2 days increased their susceptibility to infection with red clover mottle virus, but longer exposures to 36 and 32°C. decreased susceptibility. Susceptibility increased most rapidly at 36°C. The number of infections was unaffected by changes in post-inoculation temperatures between 12 and 24°C., but decreased above 24°C. The rate virus multiplied increased with increase of temperature up to 28°C., but the maximum virus concentrations reached at 18, 24 and 28°C. were very similar and above the maximum reached at 30°C.
Thiouracil inhibited infection slightly but neither it nor azaguanine affected the multiplication of red clover mottle virus in French bean. Trichothecin inhibited infection and interfered with virus accumulation. Inhibition of infection was associated with macroscopic injury to the leaves, and washing leaves up to 1 hr. after inoculation prevented both inhibition and leaf damage. Virus multiplication was not resumed when leaves were transferred from trichothecin solutions to water.     

Temperature Effects on the Onset of Sporulation by Phytophthora ramorum on Rhododendron ‘Cunningham's White’

The effect of temperature and moist period on the onset of sporangia production by Phytophthora ramorum on Rhododendron ‘Cunningham's White’ was examined with misted detached leaves held in humid chambers. Following wound inoculation with sporangia, leaves were pre‐incubated at 20°C for either 24 or 72 h prior to placement at six different temperatures (4, 10, 15, 20, 25 and 30°C). The overall mean moist period required for first occurrence of sporulation over all six temperatures was 3.24 days with the 24‐h pre‐incubation time, compared with 1.49 days for the 72‐h pre‐incubation time. Following 24 h pre‐incubation at 20°C and at an incubation temperature of 15°C, sporangia were first collected from leaves following a 24 h incubation. At 10 and 20°C, sporangia were first collected after 48 h, whereas at 4, 25 and 30°C, sporangia were first collected after 3 days. Following 72 h pre‐incubation at 20°C, sporulation generally occurred within 1 day, even at temperatures such at 4 and 30°C that are suboptimal for sporulation. The highest levels of P. ramorum sporulation were observed at 20°C. P. ramorum formed sporangia on host tissue under moist conditions within the same time frame reported for P. phaseoli, P. palmivora and P. nicotianae, but substantially more slowly than certain other species such as P. infestans. Quantifying moisture and temperature conditions for initiation of sporangia production provides knowledge which leads to a greater understanding of the epidemic potential of P. ramorum.     

Effects of changes in environmental schedules on the penetration of leaves and epidermal strips of wheat seedlings by Puccinia graminis tritici

The frequency with which intact leaves and epidermal leaf strips of wheat seedlings were penetrated by Puccinia graminis tritici, strain 21 Anz 2, was observed following exposure of inoculated material to various regimes of illumination/darkness and temperature. Epidermal strips, at 24°C, were penetrated most frequently when continuous light (540 ft-c) was commenced at either 4 or 8,20 or 24, or 36 or 40 h after inoculation or when a 4 h period of light was applied at these times. With both treatments, the curve obtained when the length of the dark period preceding illumination was plotted against the frequency of penetration showed a series of alternate peaks and troughs and the periodicity of the curves was significant at the 1 % probability level. In the former curve the best form of regression was linear modified by a cosine function, while in the latter the linear term proved to be non-significant. When dark periods of different lengths were applied, penetration was more variable on intact leaves than on epidermal strips. Penetration of intact leaves was influenced by the light intensity to which the seedlings were exposed after the dark treatment. The time of day when intact leaves were inoculated influenced penetration when they were grown under controlled conditions. Greatest penetration of the variety Little Club occurred when leaves were inoculated at 1.30 a.m. The time of day when epidermal strips were inoculated did not influence penetration. The inhibitory effect of continuous light on penetration of epidermal strips was overcome by changing the temperature from 18·5 to 24°C. Greatest penetration was obtained when the change was made 24 or 28 h after inoculation.     

A model for blood meal digestion and fat metabolism in male tsetse flies (Glossinidae)

Abstract. Fat and haematin levels of mature male Glossina morsitans morsitans Westwood were estimated at different times after feeding at temperatures between 15 and 30°C. Flies were kept (largely inactive) in 7.5 × 2.5 cm tubes, or in actograph cages, where flight activity increased with time after feeding. Haematin excretion was modelled as a series of three first order reactions, all with the same rate parameter. The model accounted for > 98% of the variance in mean haematin in each of seven experiments; the rate parameter increased linearly with temperature and activity level. A similar approach was adopted for modelling fat metabolism. The rate coefficients of lipogenesis increased with temperature, and that for lipolysis with temperature, activity level and their interaction. All experiments were analysed simultaneously to provide equations predicting haematin or fat levels for all times, for active or inactive flies, and for temperatures between 15 and 30°C. Haematin exhibited large variations between individuals, but for active flies the expected haematin content at a given time varied little between flies kept at 25 and at 30°C. In inactive flies kept at 25°C, lipogenesis peaked at ≈ 24 h and lipolysis at ≈ 48 h. For active flies the times were 12 and 24 h, respectively; both rates were about twice as high as in inactive flies. Active flies produced (up to 1 mg) more fat out of a given size of blood meal than inactive flies. Curves of fat content against logarithm of haematin content differed little with temperature, and can therefore be useful for comparative studies of field populations of tsetse.     

Study of the defensive mechanism against drought in French bean (<Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> L.) varieties

The response to drought of six green- and yellow-podded varieties of green bean was investigated in a phytotron. These varieties were also grown without irrigation in field experiments and analysis of leaf samples was carried out three times; before and under flowering and pod ripening, respectively. At first, the carotene and raffinose contents of leaves increase during mild drought (30/15°C). High temperature (35/25°C) combined with water deficiency resulted in a considerable decrease in leaf weight, chlorophyll b, maltose content, as well as the level of water-soluble antioxidants of the leaves, while the content of lipid-soluble antioxidants and raffinose content increased when compared with the control. The yellow-podded varieties of green beans responded to drought much more sensitively than the green-podded ones. The results suggested that a selection method based on the activity of antioxidants in the leaves can be used for testing the adaptability of numerous bean genotypes to drought.     

The development of Puccinia hordei on barley cv. Zephyr

Germination of uredospores of Puccinia hordei was similar on cover-slips and on the first leaves of barley seedlings (cv. Zephyr) at 100 % r.h. over the range 5–25 °C, being greatest at 20 °C. At 15, 20 and 25 °C maximum germination was attained in 6 h. No uredospores germinated on coverslips in humidities below saturation. The numbers of pustules which subsequently developed on plants incubated at 5, 10, 15 or 18 °C and 100 % r.h. for varying periods up to 24 h, were directly related to rise in temperature and length of incubation. The time from inoculation to eruption of pustules (generation time) was 6 days at 25 °C, 8 days at 20 °C, 10 days at 15 °C, 15 days at 10 °C and 60 days at 5 °C. Pustule production on inoculated plants which had been kept at 5 °C was rapidly accelerated when they were transferred to 20 °C. Data obtained at constant temperatures were used to predict generation times of the fungus in the field. The productivity of pustules, determined as weight of uredospores, was examined at 10, 15 and 20 °C. Significantly more spores were produced at 15 than at 10 °C and most were produced at 20 °C. The results are discussed in relation to those obtained by other workers and to the development of brown rust in the field.     

STUDIES ON THE EFFECT OF TEMPERATURE ON VIRUS MULTIPLICATION IN INOCULATED LEAVES

The rate at which the Rothamsted tobacco necrosis virus (RTNV) accumulates in inoculated French bean leaves increases with rising temperature to 22°C. and then decreases. Three days after inoculation, leaves at 22°C. contain 4000 times as much virus as at 10°C. and 1000 times as much as at 30°C. At all temperatures the rate of accumulation may depend on the balance between synthesis and inactivation of RTNV, but inactivation becomes increasingly important with rise of temperature above 22° C. and as the virus content of the leaves increases. Above 22°C. the rate of multiplication may increase but less rapidly than the rate of inactivation, and exposing inoculated leaves to ultra-violet radiation at various intervals after inoculation suggests that at 30°C. RTNV multiplies in and moves from the initially infected epidermal cells in slightly less than the 6 hr. needed at 22°C. Thirty hr. are needed at 10°C. Newly formed virus is rapidly inactivated at 30°C. Raising the ambient temperature also decreases the numbers of local lesions produced by RTNV, possibly by increasing the chances that the introduced virus particles will become inactivated. Increasing the virus content of the inoculum above the level giving one lesion per sq.cm. does not increase the subsequent virus content of inoculated leaves.
At temperatures of 30°C. and below, tomato aucuba mosaic virus produces necrotic lesions in leaves of tobacco and Nicotiana glutinosa whereas above 30°C. the lesions are chlorotic. In both hosts this virus multiplies more rapidly when the infected cells are killed.     

Effects of Temperature and Photoperiod on Winged Beans [Psophocarpus tetragonolobus (L.) D.C.]

The effects of temperature and photoperiod on winged beans werestudied using 15 University of New Guinea (UPS) selections andfive Sri Lanka (SL) selections. They were grown at 25/20 or30/25 °C day/ night temperature at 11 or 14 h photoperiodwith 12 h thermoperiod. Differences in stomatal density wereobserved among selections and between photoperiods. Higher densitiesoccurred at 14 h photoperiod than at 11 h photoperiod. Whenstomatal density was high due to a photoperiod or temperatureeffect, there was a corresponding increase in leaf area andd. wt of plants. Total chlorophyll content at 25/20 °C was higher at 11 hphotoperiod than at 14 h photoperiod in all selections whilethe total chlorophyll content at 30/25 °C varied with thephotoperiod and selection. Leaf area of SL selections was greater than that of UPS selections.Also greater leaf area was observed at 14 h photoperiod thanat 11 h photoperiod, irrespective of the growing temperature. Temperature was as important as photoperiod in controlling floweringof winged beans. All the UPS selections and two SL selectionsflowered at 11 h photoperiod at 25/20 °C but failed to flowerat the same photoperiod at 30/25 °C indicating an interactionbetween temperature and photoperiod. It is likely that wingedbeans have a narrow photoperiodic range, particularly the SLselections. Psophocarpus tetragonolobus (L.) D.C., winged bean, stomatal density, leaf area, flowering, temperature, photoperiod     

Effect of Temperature of the Culture Medium on Growth and Nitrogen Fixation of Inoculated Legumes and Rhizobia

Two pea (Pisum sativum L.) cultivars and a kidney bean (Phaseolus vulgaris L.) cultivars were grown in water cultures at different diurnal temperatures (15, 20, 24, 27, 30°C) or at 10°C night temperature combined with various day temperatures (20, 24, 27, 33 or 35°C) in the root medium. The inoculated plants were, more sensitive to the extreme temperatures than the plants supplied with combined nitrogen (KNO₃). The middle-European pea cv. Violetta was adapted to somewhat higher root temperatures than the northern one cv. Torsdag II, the latter showing better growth at lower temperatures, when the plants were inoculated with the same Finnish Rhizobinm strain (HA1). Especially at optimum day temperatures the nitrogen fixation and consequently the dry weights of the inoculated plants were greatly increased when the night temperature was lowered. The optimum temperature for the growth of free-living Rhizobium strains (HA1 and H43) for peus was found to be 25°C and that of a strain (P103) for beans somewhat higher. Effective nitrogen fixation by nodulated legumes without a supply of combined nitrogen is achieved only when the optimum temperature range for root function is very close to the optimum for the rhizobia.     

Thermotolerance of the photosynthetic light reactions in two <Emphasis Type="Italic">Phaseolus</Emphasis> species: a comparative study

The common bean (Phaseolus vulgaris L.) is sensitive to high temperature, while an ecologically contrasting species (Phaseolus acutifolius A. Gray) is cultivated successfully in hot environments. In this study, the two bean species were respectively acclimated to a control temperature of 25 °C and a moderately elevated temperature of 35 °C in order to compare the thermotolerance capabilities of their photosynthetic light reactions. Growth at 35 °C appeared to have no obvious adverse effect on the photosynthetic activities of the two beans, but changed their thermotolerance. After a short period of heat shock (40 °C for up to 4 h), the photosynthetic activities of 25 °C-grown P. vulgaris declined more severely than those of P. acutifolius grown at 25 °C, implying that the basal thermotolerance of P. vulgaris is inferior to that of P. acutifolius. But after acclimating to 35 °C, the thermotolerances of the two species were both greatly enhanced to about the same level, clearly demonstrating the induction of acquired thermotolerance in their chloroplasts, and P. vulgaris could be as good as P. acutifolius. Temperature acclimation also changed plants’ resistance to photoinhibition in a manner similar to those toward heat stress. In addition, acquisition of tolerance to heat and strong irradiance would reduce the dependency of the two beans on xanthophyll pigments to dissipate heat, and also seemed irrelevant to the agents with antioxidant activities such as SOD.     

Sensitivity of the common bean (Phaseolus vulgaris L.) symbiosis to high soil temperature

Summary Experiments were done to test whether N fixation is more sensitive to high soil temperatures in common bean than in cowpea or soybean. Greenhouse experiments compared nodulation, nitrogenase activity, growth and nitrogen accumulation of several host/strain combinations of common bean with the other grain legumes and with N-fertilization, at various root temperatures. Field experiments compared relative N-accumulation (in symbiotic relative to N-fertilized plants) of common bean with cowpea under different soil thermal regimes. N-fertilized beans were unaffected by the higher temperatures, but nitrogen accumulation by symbiotic beans was always more sensitive to high root temperatures (33°C, 33/28°C, 34/28°C compared with 28°C) than were cowpea and soybean symbiosis. Healthy bean nodules that had developed at low temperatures functioned normally in acetylene reduction tests done at 35°C. High temperatures caused little or no suppression of nodule number. However, bean nodules produced at high temperatures were small and had low specific activity. ForP. vulgaris some tolerance to high temperature was observed among rhizobium strains (e.g., CIAT 899 was tolerant) but not among host cultivars. Heat tolerance ofP. acutifolius andP. lunatus symbioses was similar to that of cowpea and soybean. In the field, high surface soil temperatures did not reduce N accumulation in symbiotic beans more than in cowpea, probably because of compensatory nodulation in the deeper and cooler parts of the soil.     

Development of Ramularia Leaf Spot on Sugar Beet as Influenced by Temperature and the Age of the Host Plant

A method of inoculating sugar beet plants (Beta vulgaris L.) with Ramularia beticola Faut. & Lamb, is described. Following inoculation, disease development in relation to temperature and plant age was studied for more than a month. The incubation period was 18 days at 10°C compared to 14 days at 17°C. At 25°C no symptoms appeared. Both temperature and plant age significantly influenced disease level and rate of disease development. Plants incubated at 17°C were more severely diseased 33 days after inoculation than plants incubated at 10°C. Young plants (3 weeks at inoculation) Were more susceptible than older plants (5 and 8 weeks at inoculatson) under growth chamber conditions. In the field, symptoms of Ramularia leaf spot appear relatively late in the season and young leaves are rarely attacked. The inconsistency of these observations is discussed.     

Virus Free Garlic (Allium Sativum L.) Plants Obtained by Thermotherapy and Meristem Tip Culture

Virus infection in garlic considerably reduces yield and quality in Argentina. The production of virus free “seed” was attempted by means of thermotherapy and meristem tip culture. A hot water treatment was employed to determine the lethal temperature/time combination for clonal type (c.t.) Blanco cloves. It was established that 50°C × 20 min, 50°C × 15 min and 55°C × 5 min were the limit thermal/time combinations which garlic could withstand. Those treatments were employed followed by meristem tip culture, however, none of the successfully developed plants after culture (only 13 %) were virus-free. Hot air treatments in a growth chamber at 36°C lasting for 30, 40 and 60 days, and at 25°–32° for 30 days in a greenhouse were tested on c.t. Blanco. Cloves kept at room temperature throughout the experiment were employed as controls. In the 25°–32°C treatment, 73% of meristems produced plants and, of these, 33 % were virus free. After 30 and 40 days at 36 °C, 62 % and 67 % of the meristems developed into plantlets, of which respectively 51 % and 50 % were virus-free. Very few meristems (10 %) developed into plants when cloves had been kept at 36°C for 60 days but the resulting plantlets were all virus free. Controls produced 78 % of plants, of which 14 % were virus free. Results of hot air treatments of 36 °C for 40 days performed on c.t. Colorado, Rosado, Paraguayo, Espaol and Hilario Ascasubi were similar to those obtained with c.t. Blanco. In Espaol and Hilario Ascasubi, no virus-free plants were detected among control specimens (no thermotherapy treatment). The only virus (from up to 3 that infected the plants) that persisted in some plants after themotherapy and meristem tip culture was garlic yellow streak.     

Mortality fecundity and longevity of parasitoids of the spotted tentiform leafminer,Phyllonorycter blancardella [Lep.: Gracillariidae] at constant temperatures in the laboratory

The results of laboratory tests showed that mortality of adult eulophids, primarily,Sympiesis sericeicornis (Nees),S. marylandensis Girault andPnigalio flavipes (Ashmead), was significantly (P<0.05) lower than that of adultPholetesor ornigis (Weed) when exposed to temperatures between 20° and 36°C for 48 h. However, adultP. ornigis lived longer than those of the eulophids at 15°C, but were shorter liver at 33°C. The fecundity ofP. ornigis was little affected at temperatures of 15°, 20°, 24° and 33°C. Exposure of adultP. ornigis to 30°C for 16 h resulted in reduced longevity of both sexes but did not affect fecundity or the proportion of females ovipositing. Mortality of pupae of the eulophids was significantly lower than that of pupae ofP. ornigis at temperatures of 20°, 30° and 33°C. The sex ratio of surviving adults was not affected by temperature.      

Effect of hypoxia and its repercussions in packing pupae of the parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae) for shipment

Hypoxia periods of 6, 12, 24, 48, and 72?h combined with temperatures of 15°C, 20°C and 25°C were applied to Diachasmimorpha longicaudata pupae in packaging conditions. Alternating temperatures of 26–20–26°C were applied to pupae in three sequential 4-h periods less than 12?h of hypoxia, and the effect of hypoxia on the pupae was evaluated under ambient conditions in commercial shipping. The emergence, longevity, fecundity and flight ability of adult parasitoids were recorded. The duration of hypoxia (>24?h) and the higher temperature (25°C) significantly reduced the emergence and longevity of adults. The different temperatures, including the variation in temperature combined with hypoxia, showed no significant effect on fecundity or flight ability. The temperature and humidity recorded during commercial shipping under hypoxia did not show any effect on the emergence of parasitoids. As a consequence, hypoxia was only notably significant after 24?h, which occasionally occurs in practical packaging processes. The use of hypoxia for shipping D. longicaudata pupae can be widely recommended, but long shipping periods and high temperatures should still be avoided.     

Effects of environmental factors on growth of lesions on field bean leaves infected by Botrytis fabae

Chocolate spot lesions increased in size only slowly when the relative humidity of the air was below 66%. Following a lag phase immediately after infection the rate of increase was linear and proportional to humidity between c. 70% and 100% r.h. Lesions on leaflets kept at 70% r.h. for 8 h and at 100% r.h. for 16 h/day increased in size at only 27% of the rate of those at continuous 100% r.h. The optimum temperature for lesion growth was between 15 and 22 °C, the minimum <4 °C and the maximum c. 30 °C. Humidity did not interact with temperature between 10 and 20 °C. Neither light intensity nor a film of water over the leaves affected lesion growth. These findings are discussed in relation to meteorological data and field observations. The possible mechanisms whereby humidity affects lesion growth did not appear to be related to CO₂ and O₂ concentrations nor to the overall water potential of the leaf. Preliminary evidence is presented for the production of phytotoxins within lesions.     

Density dependence depends on scale; at larval resource patch and at whole population

A previous study (Tuda and Shimada, 1993) has shown that the equilibrium population size of the azuki bean beetle was lower at 32°C than at 30°C and that this difference was due to a reduced maximum population size of emerged progeny through inside-bean process. In this paper, these results were analyzed further on the scale of the individual bean where interaction among larvae took place. Per-bean numbers of deposited eggs, hatched eggs, and emerged adults have been recorded at seven different parental densities under the two temperature conditions. Three individual-bean-scale process hypotheses that may explain the reduced maximum emergence density on the whole population scale are suggested: (1) a lower maximum emergence per bean at 32°C than at 30°C, if the bean scale and the wholepopulation scale share the same density-dependent pattern in adult emergence, (2) a limited range of hatched egg number per bean at 32°C, resulting from the adult oviposition process outside beans, and (3) different patterns of density-dependent emergence between the two different scales. This study showed that the inside-bean pattern of responses on the bean scale was a simple saturated curve at 30°C, but one with a discontinuous decline at higher hatched egg densities at 32°C. On the contrary, during outside-bean process, the peak number of hatched eggs decreased on this scale as observed on the wholepopulation scale. I discuss why the extracted factor of inside-bean process on the whole-population in the previous study could not be applied to the bean-scale pattern.