Influence of day-length and isolates of Phytophthora infestans on field resistance to late blight of potato

Main and interaction effects of day-length and pathogen isolate on the reaction and expression of field resistance to Phytophthora infestans were analyzed in a sample of standard clones for partial resistance to potato late blight, and in the BCT mapping population derived from a backcross of Solanum berthaultii to Solanum tuberosum. Detached leaves from plants grown in field plots exposed to short- and long day-length conditions were independently inoculated with two P. infestans isolates and incubated in chambers under short- and long photoperiods, respectively. Lesion growth rate (LGR) was used for resistance assessment. Analysis of variance revealed a significant contribution of genotype × isolate × day-length interaction to variation in LGR indicating that field resistance of genotypes to foliar late blight under a given day-length depended on the infecting isolate. An allele segregating from S. berthaultii with opposite effects on foliar resistance to late blight under long- and short day-lengths, respectively, was identified at a quantitative trait locus (QTL) that mapped on chromosome 1. This allele was associated with positive (decreased resistance) and negative (increased resistance) additive effects on LGR, under short- and long day-length conditions, respectively. Disease progress on whole plants inoculated with the same isolate under field conditions validated the direction of its effect in short day-length regimes. The present study suggests the occurrence of an isolate-specific QTL that displays interaction with isolate behavior under contrasting environments, such as those with different day-lengths. This study highlights the importance of exposing genotypes to a highly variable population of the pathogen under contrasting environments when stability to late blight resistance is to be assessed or marker-assisted selection is attempted for the manipulation of quantitative resistance to late blight.     

Two recessive genes controlling thermophotoperiod-sensitive male sterility in wheat

Male sterility of wheat-breeding line 337S (Triticum aestivum L.) is sensitive to both short day-length/low temperature and long day-length/high temperature. 337S was crossed with the common wheat variety, Huamai No. 8 and the F₁ was highly fertile. The F₂ population segregated in a 15:1 ratio for fertility/sterility in 243 individuals under long day-length/high-temperature. The two thermophotoperiod-responsive male sterile genes were mapped to chromosomes 5B and 2B using Simple Sequence Repeat (SSR) markers and bulked segregant analysis. Partial linkage maps around the sterility loci of chromosomes 2B and 5B were constructed using the 243 individuals in the F₂ population. One gene (wptms1) for male sterility was flanked by the SSR markers Xgwm335 and Xgwm371 at a genetic distance in chromosome 5B of 4.1 and 24.4 cM, respectively. The second gene (wptms2) was mapped between markers Xgwm374 and Xgwm120 at a genetic distance of 6.6 and 20.9 cM, respectively. The closest linked markers Xgwm335 (wptms1) and Xgwm374 (wptms2) explained 53 and 38% of phenotypic variation for the fertility. The SSR markers provide a useful tool to transfer the male sterile genes into elite wheat germplasm.     

FIELD AND CULTURE STUDIES ON GROWTH AND REPRODUCTION OF CALLITHAMNION BYSSOIDES (RHODOPHYTA,CERAMIALES) IN NORTH CAROLINA1,2

The life history of Callithamnion byssoides Arnott ex Harv. in Hook. from North Carolina is shown to be of the Polysiphonia-type. Cross-gradient light-temperature culture in 8:16 and 14:10 LD cycles was utilized to investigate the effects of light intensity, temperature and day-length on growth and reproduction. Carposporophyte and tetrasporangium development were controlled by total light energy rather than photoperiod. Results of these studies explain the observed seasonal periodicity of growth and reproduction on the North Carolina coast. Variations between these results and previously published data for this species in Texas are explained in terms of ecotypic differentiation.     

Genetic and environmental sources of egg size, fecundity and body size in the migrant skipper, Parnara guttata guttata (Lepidoptera: Hesperiidae)

Genetic and environmental sources of egg size, fecundity and body size (forewing length) were examined in the butterfly, Parnara guttata guttata. Phenotypic and genetic correlation and heritability were estimated for these traits under different day-length and temperature conditions. Egg size and fecundity had relatively high heritabilities, and body sizes in males and females had moderate and high heritability, respectively. Negative phenotypic and genetic correlations between egg size and fecundity were estimated in treatments corresponding to the natural conditions during larval development of the first and second generations. Phenotypic and genetic correlations between body size and egg size differed considerably between insects reared under long and short day-lengths. Next, genotype–environment interactions were estimated by comparing reaction norms to day-length or temperature of these traits among families. ANOVA analysis revealed significant genotype–environment interactions in egg size and forewing length in both sexes for day-length and temperature. These results suggested that a large additive genetic variance for egg size might have been maintained by a genetic trade-off and/or by genotype–environment interactions in P. g. guttata.     

Field studies and growth experiments on Gelidium latifolium from Asturias (northern Spain)

Seasonal cycles of environmental factors (temperature, day-length, nutrient concentration) and changes in Gelidium latifolium biomass, percentage reproduction and size are given, and non-parametric correlation is used to quantify possible relationships. The results are compared with growth experiments, testing effects of total light dosage, agitation, temperature and Photon Flux Density (PFD). Results of total light dosage × agitation growth experiment show that maximum growth is obtained when plants are cultured at a long photoperiod (16 : 8 L/D) with agitation. Results of temperature × PFD experiment show that maximum growth is obtained at PFD values higher than 50 µE m^–2 s^–1 at temperatures between 20–25 °C. Possible applications of field studies and culture experiments in management of wild resources and industrial cultivation are proposed.     

Causes of Flowering of Long-Day Potato Species under Short-Day and Cold-Night Conditions

Flowering and tuber formation in high-mountain potato species Solanum sparsipilum Bitt., S. acaule Bitt., S. punae Juz., S. demissum Lindl., and a tuber crop Ullucus tuberosus Caldas. were investigated. All these species are characterized by absolute requirement of long day-length for flowering and short day-length for tuberization. Plants were grown under the following conditions: natural day-length with a photoperiod of 17 h or longer (treatment 1), short days with a photoperiod of 12 h and warm nights (15–20°C) (treatment 2), and short days with cold nights (5–6°C) (treatment 3). In the first treatment, plants produced flowers but no tubers. In the second treatment, plants produced tubers but no flowers. In the third treatment, plants produced both flowers and tubers. In leaves of S. acaule and U. tuberosus, the levels of gibberellins and ABA were determined. A high activity of gibberellins in the third treatment was similar to that in the first treatment, whereas high ABA activity in the third treatment was similar to that in the second treatment. It is supposed that cold nights retard the destruction of GA in plants during the dark period of diurnal cycle and ensure a permanently high level of gibberellins, which facilitates flowering of long-day species under short-day conditions. The high level of ABA is considered a plant response to short-day conditions, which is favorable for tuberization.     

Morph determination in the bird cherry-oat aphid, Rhopalosiphum padi L

Both crowding and poor nutrition induce the appearance of emigrants in Rhopalosiphum padi L. No emigrants developed when the aphid was reared in isolation for six successive generations on actively growing leaves of bird cherry. However, emigrants developed as soon as the leaves ceased to grow or when the aphids became crowded. Crowding of mothers and postnatal crowding of the nymphs of apterous exules both influenced the induction of alate exules. The highest proportion of alate exules developed when both mother and offspring were crowded. Short day-length induced the appearance of gynoparae and males. For 50% production of gynoparae and males, over the range of temperature 10–18d?C, a 1.75 h reduction in day-length is required for every 4d? increase in temperature. At 18 d?C, even at day-lengths as short as 6 h, exposure for three generations is required before all offspring become gynoparae or males. Low temperature and short day-length was ineffective in inducing the development of gynoparae or males in the first three generations developing from the fundatrix.     

Auxin level and regeneration of Begonia leaves

Summary As previously found, both the level of ether-extractable auxin (presumably indole-3-acetic acid) and the root-forming ability of B.xcheimantha leaves are increased under long-day conditions by high temperature, whereas the capacity for adventitious bud formation is reduced. However, this relation is present under relatively high light intensity only. Under the low light intensities in late fall neither auxin level nor regeneration ability were significantly affected by temperature.Dark treatment of detached leaves for 2 to 16 days greatly counteracted the inhibitory effect of high temperature on bud formation and reduced both the auxin level and the root-forming ability of the leaves.The great seasonal changes in the regeneration ability of Begonia leaves seem to be the result of a complex interaction of temperature, day-length, and daily light energy on the level of endogenous auxin and other growth regulators.     

Role of natural day-length and temperature in determination of summer and winter diapause in Pieris melete (Lepidoptera: Pieridae)

Under field conditions, the cabbage butterfly, Pieris melete, displays a pupal summer diapause in response to relatively low daily temperatures and gradually increasing day-length during spring and a pupal winter diapause in response to the progressively shorter day-length. To determine whether photoperiod is 'more' important than temperature in the determination of summer and winter diapause, or vice versa, the effects of naturally changing day-length and temperature on the initiation of summer and winter diapause were systematically investigated under field conditions for five successive years. Field results showed that the incidence of summer diapause significantly declined with the naturally increasing temperature in spring and summer generations. Path coefficient analysis showed that the effect of temperature was much greater than photoperiod in the determination of summer diapause. In autumn, the incidence of diapause was extremely low when larvae developed under gradually shortening day-length and high temperatures. The incidence of winter diapause increased to 60-90% or higher with gradually shortening day-length combined with temperatures between 20.0°C and 22.0°C. Decreasing day-length played a more important role in the determination of winter diapause induction than temperature. The eco-adaptive significance of changing day-length and temperature in the determination of summer and winter diapause was discussed.     

Dormancy and Flowering in Anemone coronaria L. as Affected by Photoperiod and Temperature

The effects of day-length and temperature on flowering and dormancyinduction were studied in Anemone coronaria L., with plantsraised either from corms or achenes. An Israeli hybrid sourcewas used (de Caen cv. Hollandia x Israeli wild type). Dormancy onset is characterized by the cessation of foliageleaf production, the appearance of leaf scales protecting theperennating bud, and leaf senescence. Dormancy was induced byhigh temperature and long days but increasing temperatures (from17/12 °C to 32/12 °C) induced earlier dormancy thanprolonging the photoperiod (range 8–16 h). A significant(P = 0.01) interaction was found between these factors, withsmaller photoperiodic effects the higher the temperature. At22/17 °C the critical day-length for dormancy inductionwas between 11 and 12 h. The transition from the vegetative to the reproductive stageappears to be an autonomous process that occurs with developmentin plants raised from either corms or achenes and does not requireenvironmental induction. Photo- and thermoperiodic effects onflowering were indirect, being mediated through their influenceon dormancy induction. Anemone coronaria L., dormancy, flowering, photoperiod, thermoperiod     

DORMANCY OF GLADIOLUS CORMS VI. EFFECTS OF TEMPERATURE TREATMENT ON BREAKING DORMANCY OF GLADIOLUS CORMS STORED IN A STORAGE ROOM AND OF THOSE GROWN UNDER DIFFERENT DAY-LENGTH

A high temperature treatment at 35? for 5 days followed by alow temperature treatment at 0-5? for 25 days was given at fifteen-dayintervals to five groups each of two varieties (White Gold andCardinal Prince) stored in a storage room from September 27to November 26. The temperature treatment was apparently effectivefor sprouting of corms of both varieties at earlier period,but rather inhibitory at later period of dormancy. The plants of two varieties (Early Red and Spot Light) grownunder short day-length (9 hr) showed slightly earlier floweringand corm-forming than those grown under natural long day-length.These plants were harvested from July 1 to Septmber 1 at twentydayintervals, and sprouting of their corms with and without temperaturetreatment similar to the previous method was investigated. SpotLight corms did not sprout irrespective of temperature treatment.Early Red corms always sprouted earlier in the temperature-treatedlots, whereas they sprouted a little later in the non-treatedlots. The temperature treated corms grown under the short day-lengthshowed delaying and low percentage of sprouting. On the contrary,in the non-treated lots, sprouting of corms grown under thelong day-length was slower than those grown under the shortday-length. ¹Contribution No. 24 from Laboratory of Horticulture (Olericultureand Floriculture), Kyoto University. (Received May 23, 1960; )     

Pathogenicity and identification of the lilac pathogen, Pseudomonas syringae pv. syringae van Hall 1902

Comparative in planta studies with Pseudomonas syringae pv. syringae have established optimum conditions for disease expression in lilac in terms of inoculum concentration, host age and post-inoculation conditions (temperature and day-length). Reproducible disease reactions required an inoculum concentration exceeding the ED⁵⁰, 5 × 10⁶ cfu/ml, and a temperature for post-inoculation incubation not exceeding 19°C. A revised host range of P. syringae pv. syringae, proposed on the basis of confirmation of pathogenicity of strains to lilac, comprises 44 species from monocotyledonous and dicotyledonous plants. Nine new hosts Abelmoschus esculentus, Bromus willdenowii, Camellia sinensis, Centrosema pubescens, Citrullus lanatus, Cotoneaster sp., Cucumis melo, Populus×euramericana and Triticum aestivum, are recorded. A comparative laboratory study was made of strains of P. syringae pv. syringae using more than 30 selected biochemical and nutritional tests. The pathovar could be characterised on the basis of 11 of these which may prove to be useful determinative tests.     

The preconditioning effect of day-length and light intensity on adult plant resistance to powdery mildew in oats

Oat genotypes with partial resistance to mildew exhibited a higher level of adult plant resistance (a.p.r.) when grown in 16 h compared with 8 h day-length. This increased resistance was expressed in the upper leaves, and to some extent in the lower, earlier-developed leaves. The expression of increased resistance coincided with floral initiation in Maldwyn, but preceded it in CC4761. The development of a.p.r. and floral initiation were thus not inherently linked, but conditions which accelerated the plants' ontogeny also caused earlier expression of resistance. For the most efficient testing of breeding material, plants should be grown at long day-length and high light intensity. When plants are grown at 16 h day-length and constant temperature of 15 ^oC, the leaf segments should be inoculated at the 6 to 8 leaf stage because normally susceptible genotypes showed marked resistance when inoculated later.     

Plant resistance to cold stress: Mechanisms and environmental signals triggering frost hardening and dehardening

This introductory overview shows that cold, in particular frost, stresses a plant in manifold ways and that the plant’s response, being injurious or adaptive, must be considered a syndrome rather than a single reaction. In the course of the year perennial plants of the temperate climate zones undergo frost hardening in autumn and dehardening in spring. Using Scots pine (Pinus sylvestris L.) as a model plant the environmental signals inducing frost hardening and dehardening, respectively, were investigated. Over 2 years the changes in frost resistance of Scots pine needles were recorded together with the annual courses of day-length and ambient temperature. Both act as environmental signals for frost hardening and dehardening. Climate chamber experiments showed that short day-length as a signal triggering frost hardening could be replaced by irradiation with far red light, while red light inhibited hardening. The involvement of phytochrome as a signal receptor could be corroborated by respective night-break experiments. More rapid frost hardening than by short day or far red treatment was achieved by applying a short period (6 h) of mild frost which did not exceed the plant’s cold resistance. Both types of signals were independently effective but the rates of frost hardening were not additive. The maximal rate of hardening was − 0.93°C per day and frost tolerance of < − 72°C was achieved. For dehardening, temperature was an even more effective signal than day-length.     

In Vitro Propagation of Potato (Solanum tuberosum L.)

Potato shoots were propagated in vitro by placing nodes fromsprouted tubers on Murashige and Skoog type medium without hormones.The vigour of growth and the rate of node production increasedwith both day-length and temperature over the ranges 8–24h and 15–25 °C respectively. Propagation rates ofup to x 10 per month were obtained. In vitro plantlets spontaneouslyformed roots either in agar or liquid cultures. Plantlets leftin the culture jars for 3–4 months eventually senescedand formed small tubers in 16 and 24 h day-lengths. In a day-lengthof 8 h vegetative growth continued by branching and no tuberswere formed. Solanum tuberosum L., potato, tissue culture, propagation, temperature, day-length     

An attempt to predict the start,peak and end of a pollen season

The different phases, start, peak and end of the pollen season were predicted using a cumulated activity method. This procedure is a development of the temperature sum method. The temperature was transformed to activity (A):

A = 2**[(T+g)/(10*h)] - k.

T = daily mean temperature over the treshold.

g,h,k = coefficients.

Other weather parameters are also to be included in the future.

The activity is cumulated day by day and the sum is used as an indicator of a specific phase. A cumulated activity model is defined by the above formula with specified values of the three coefficients g, h and k. Four conditions stating criteria for valid cumulation days and the cumulated target sum for the phase in question are to be defined. The model was based on pollen and weather data in Stockholm 1973–1988. The cumulated activity method was found to be best applicable to Ulmus, Betula and Pinus, but less useful for Alnus, Corylus and Quercus. The model was not satisfactory for Poaceae and Artemisia.     

Primi Dati Sull'andamento Stagionale delle Temperature del Troneo di Olivo

Abstract

Temperatures recorded in a olive-tree stem in 1961–1962. — In the Botanical Garden of Bari a temperature recorder has been placed, bearing 6 electrothermometers with platinum resistences having a sensitivity of 2,4 mm/C[ddot], with a recording approximation of 0,1 C[ddot].

The olive tree under examination is a grown-up tree, which has been pruned according to the local methode, and it belongs to a local breed named « Ogliarola leccese ».

— Five thermometers have been employed as follows: 1^rst in the air, hanging from the stem, m. 1,30, high; 2^nd into the outer bark, cm, 0,5 deep; 3^rd into the cambium, cm. 1,5 deep; 4^th into the sap-wood, cm. 6 deep; 5^th into the hearth-wood, cm. 22 deep.

— The thermometers were all placed on the east side of the stem.

— The figures and the graphs of the paper show that:

a) The whole stem of the specimen under examination has a mean temperature which is higher than that of the surrounding air.

b) The outer bark gets warmer than the air, during the day-time; during the night it gives up heat outside and inside, namely towards the stem tissues, particularly to the bark-cambium-sapwood zone, and also as far as the hearth wood zone.

c) The whole living zone of the stem (bark-cambium-sapwood) generally keeps temperature values intermediate between those of the outer bark and those of the air. The temperature values vary along the year.

d) In spring the cambium is warmer than the outer bark.

e) In winter cambium and sapwood generally have the same temperature. The temperature values recorded in this season are much lower than those of the outer bark and almost the same of those of the air.

f) The behaviour of temperature in cambium and sapwood is probably ruled by biological factors.

g) The hearth-wood keeps generally warmer than the air and cooler than other outer tissues. Its thermic rhytm is almost reversed in comparison with that of the outer tissues.

Il seems that hearth wood acts as an useful heat collector and distributor towards the living outer tissues during the diurnal and seasonal temperature remissions, at least in mild climates as that of Bari.     

Natural variation in the regulation of leaf senescence and relation to other traits in Arabidopsis

Leaf senescence results in the recycling of nutrients, thereby providing resources required for growth and reproduction. In this study, the effect of day-length on leaf senescence in eight different Arabidopsis thaliana ecotypes was determined and the relationship between senescence and other morphological and life history traits was analysed. A significant variation in the start and extent of leaf senescence depending on the genetic background and the response to day-length was found. Whereas senescence of early flowering ecotypes was accelerated by long days, no effect of day-length on senescence could be found in late flowering Kas-1 plants. Senescence in the different ecotypes was associated with other traits, such as floral transition, the total number of fruits, the total number of leaves and the maximum chlorophyll content. Plants that bolted early also senesced early, produced fewer leaves, accumulated less chlorophyll, but produced more fruits. The present results indicate that senescence may be a key component in the trade-off between investment in photosynthetic capacity and reproduction. The relationship between senescence and other traits was maintained independent of whether differences in senescence were caused by genetic (ecotype) or environmental (day-length) variation, suggesting that genetic and environmental factors affect these traits through common regulatory pathways.     

Effects of 6-benzylamino-purine and 1-naphthaleneacetic acid on the epiphyllous bud formation in Bryophyllum

Summary The effects of the kinin 6-benzylamino-purine and of 1-naphthaleneacetic acid (NAA) on the epiphyllous bud formation in Bryophyllum were studied under controlled environment.In B. daigremontianum which requires long days for epiphyllous budding, buds were formed under continuous short days after application of the kinin. Similarly, such a treatment caused budding in attached non-aging leaves of B. calycinum which normally form buds only after detachment from the plant. This stimulatory effect of the kinin was strictly bound to the treated leaves (or leaf parts), which also showed an increased growth compared with the opposite non-treated leaves. Root formation in the developing buds was inhibited by the kinin.In both species NAA inhibited the epiphyllous budding under inductive conditions. A similar inhibitory effect was exerted by terminal and axillary buds.The results are discussed in the light of other investigations in this and related fields. It is concluded that epiphyllous bud formation is under the control of a correlative inhibition similar to apical dominance. It is further concluded that even though day-length controls both flowering and epiphyllous budding in B. daigremontianum the two processes must be affected through different biochemical systems.     

Winter low temperature disturbance in the southern subtropics of China promotes the competitiveness of an invasive plant

Winter low temperature disturbance in the southern subtropics has important effects on the weed community structure, but the role of uniquely low temperatures in biological invasions is unclear. Here, we examined the competitive effects of an invasive plant, Bidens pilosa L., and its native congener, Bidens biternata (Lour.) Merr. et Sherff, during high and low temperature seasons to determine whether low temperatures promote the competitiveness of B. pilosa in the southern subtropics of China. The growth and physiological responses of the two Bidens species to low (10/5 °C) and optimum (30/25 °C) temperatures were examined to determine how the invasive B. pilosa responds to low temperature stress. Our results showed that the competitive balance index values of B. pilosa in low temperature seasons were significantly higher than those in high temperature seasons, which implied that low temperatures may be more beneficial to the competitiveness of B. pilosa than high temperatures in the southern subtropics. The smaller decline in the relative growth rate and the photosynthetic ability of B. pilosa compared with B. biternata under low temperature stress indicated that the former was less negatively affected by low temperature than the latter. A higher DPPH^· (1.1-diphenyl-2-picrylhy-drazyl) scavenging rate and greater heat-stable protein content in B. pilosa under low temperatures might help the invasive plant to maintain more effective physiological functions and thus a higher growth rate. Overall, the uniquely low temperature in the southern subtropics of China is expected to promote the invasiveness of the exotic B. pilosa.