Germination Temperature Research Articles

Identification of No. 8 spoilage bacteria and study on biological properties of areca taro

You should leave 8 mm of space above the abstract and 10 mm after the abstract. The heading Abstract should be typed in bold 9-point Times. The body of the abstract should be typed in normal 9-point Arial in a single paragraph, immediately following the heading. The text should be set to 1 line spacing. The abstract should be centred across the page, indented 17 mm from the left and right page margins and justified. It should not normally exceed 200 words. In order to explore the effects of fungus infestation on areca taro during cold storage period, a black morphologic fungus (No. 8) was isolated and identified as Curvularia lunata by morphological observation and 18sRNA gene sequencing. The study on its biological properties showed that the growth and development temperature of Curvularia lunata were 15-40 ℃, the optimal temperature was 25-30 ℃, the optimal pH was 6-8, the optimal light condition was natural light, the optimal carbon source was sorbitol, maltodextrin and mannitol, and the optimal nitrogen source was glycine. The optimum germination temperature, pH and humidity of conidia were 25 - 40℃, 6 - 9 and 100% + water drop, respectively, under the promotion of 40% areca taro solution. The aim of this study was to provide a theoretical basis for the prevention and treatment of areca taro rotting in cold storage period.

Tibet The Seed Germination Characteristics Under Low Temperature and Spring Sowing Study of 8 Rapeseed Varieties

To explore the low temperature germination characteristics of rapeseed, 8 main cultivars were selected for germination experiments in incubators at 20℃, 16℃, 12℃ and 8℃, respectively, to measure and analyze the germination potential, germination rate, root length, bud length, etc. The results showed that there was significant difference in the germination potential of tested rapeseeds at temperatures. And the low temperature of 8℃ was significantly reduced the germination potential. With the decrease of germination temperature, the growth of roots and buds were inhibited significantly. There were significant differences both in temperatures and varieties. The germination potential, root length and bud length could be used as the main index to evaluate seed germination of rapeseed under low temperature. In addition, to screen varieties suitable for spring sowing as green manure, the spring sowing test was carried out. The study found that the fresh grass yield of “Huyouzao No.1” was 1712.53 kg/m 2 , which was much higher than other 7 varieties. Its relative root length was second only to “Huyou17” and its relative bud length next to “Huyoufei No.1” at 8℃, respectively. The results can provide a reference for early spring sowing of rapeseed as green manure.

Comparative study on the monocyclic components of plum rust with isolates from three growing regions in Brazil

AbstractThis study aimed to evaluate the effect of temperature and wetness period (WP) on urediniospore germination of Tranzschelia discolor and the influence of temperature in the latent period and the number of pustules/cm2 produced by isolates obtained from São Paulo (SP), Paraná (PR) and Santa Catarina (SC) states in Brazil. Spore germination was assessed under six temperatures (10–35°C) in combination with six WPs (3–48 hr). The latent period and the number of pustules were assessed in detached plum leaves inoculated with T. discolor at temperatures from 10 to 35ºC. In addition, the number of pustules produced by the three isolates was compared for 15 days at 23°C. The optimum temperatures for urediniospore germination estimated were 24.2, 24.4 and 24.3°C for isolates from PR, SC and SP, respectively, in the WP of 48 hr. The shortest latent periods estimated for PR, SC and SP isolates observed were 10.3, 8.9 and 10.6 days, at the optimal temperature of 21.9, 22.1 and 22.4°C, respectively. The greatest number of pustules/cm2 was 39.8, 158.5 and 63.1, for PR, SC and SP isolates, at the optimal temperature of 22.2, 22.2 and 22.7°C, respectively. Differences between isolates were observed for the latent period, which was shorter in leaves inoculated with the SC isolate. In addition, the number of pustules was greater in leaves inoculated with the SC isolate as compared to the latent periods and the number of pustules on leaves inoculated with the isolates from the other states. The highest rust progress rates were observed for isolates from the states of Santa Catarina and São Paulo. This information serves as a background study to better understand how plum leaf rust epidemics occur in the field under different environmental conditions, thus aiding in both the prevention of possible epidemics and the conception of more efficient control strategies.

Effects of Pre-sowing Treatments and Abiotic Stress on the Germination of Ceratonia siliqua Seeds of Four Moroccan Biomes

In order to improve the germination rate of carob seeds (Ceratonia siliqua L.), we studied the morphological characteristics of the fruits (pod and seeds, integumentary hardness and tolerance to abiotic stress of the seeds) of seven ecotypes of carob trees from four regions of Morocco. The fruits of its seven populations were studied according to seven discriminative characteristics relating to the pods (length, width, thickness, total number of seeds, total weight of the pulp, seeds per pod and yield of pods per tree) and four discriminative characteristics relating to the seeds namely length, width, thickness and total fresh weight of seeds. Integumentary hardness was evaluated by pretreating the seeds with boiling water and 95% sulfuric acid. Similarly, we also followed the evolution of water absorption by the seeds during 4 days and we evaluated on these seeds pre-treated, effects of different incubation temperatures (10°C, 25°C and 40°C), their tolerance to different concentrations of NaCl, PEG6000 (0MPa, -0.5MPa, -1MPa and -1.5MPa ) and their reversibility. The morphological characterization of the fruits allowed us to group the populations studied into three groups. Soaking the carob seeds in sulfuric acid for 20 minutes improved the germination rate and time. The evolution of water absorption makes it possible to distinguish two phases. The first phase is obtained during the first 24 hours and characterized by a rapid penetration of water, and second phase which lasts over the last 72 hours and which is characterized by a slow entry of water. The optimum temperature for germination of seeds from all provenances is 25°C. The germination behavior of carob under conditions of osmotic stress demonstrated a highly significant treatment effect (concentration of PEG6000) on the rate and mean time of germination and revealed that this species is very resistant to drought. This study also showed that, salt has a depressive effect on the average germination rate, time and length of radicles. The results of the reversibility test showed that the germination of seeds transferred from osmotic stress and salt stress (-0.5, -1 and -1.5MPa) and from the temperature of 40°C. is totally inhibited. On the other hand, seeds transferred from a temperature of 15°C resume germination under optimal conditions. This study allowed us to select a variety with high yield and tolerant to various biotic constraints.

Seed germination ecology of meadow knapweed (Centaurea × moncktonii) populations in New York State, USA

AbstractThe introduced meadow knapweed (Centaurea × moncktonii C.E. Britton), a hybrid of black (Centaurea nigra L.) and brown (Centaurea jacea L.) knapweeds, is increasingly common in pastures, meadows, and waste areas across many U.S. states, including New York. We evaluated the effects of temperature, light, seed stratification, scarification, and population on percent germination in four experiments over 2 yr. Percent germination ranged from 3% to 100% across treatment combinations. Higher temperatures (30:20, 25:15, and sometimes 20:10 C day:night regimes compared with 15:5 C) promoted germination, especially when combined with the stimulatory effect of light (14:10 h L:D compared with continuous darkness). Under the three lowest temperature treatments, light increased percent germination by 15% to 86%. Cold-wet seed stratification also increased germination rates, especially at lower germination temperatures, but was not a prerequisite for germination. Scarification did not increase percent germination. Differences between C. × moncktonii populations were generally less significant than differences between temperature, light, and stratification treatments. Taken together, these results indicate that C. × moncktonii is capable of germinating under a broad range of environments, which may have facilitated this species’ range expansion in recent decades. However, C. × moncktonii also shows evidence of germination polymorphism: some seeds will germinate under suboptimal conditions, while others may remain dormant until the abiotic environment improves. Subtle differences in dormancy mechanisms and their relative frequencies may affect phenological traits like the timing of seedling emergence and ultimately shape the sizes and ranges of C. × moncktonii populations.

MAPK11 regulates seed germination and ABA signaling in tomato by phosphorylating SnRKs.

Seed germination is a critical stage in the plant life cycle and it plays an important role in the efficiency of agricultural production. However, our knowledge of the mechanisms that regulate seed germination remains limited. In this study, we identified a novel gene, MAPK11, that encodes mitogen-activated protein kinase 11; its expression was significantly higher in seeds of tomato varieties with a low optimum germination temperature than in those with a high optimum germination temperature. In tests at 25 °C, overexpression of MAPK11 in an accession with optimum germination at 25 °C resulted in a decrease in germination, whereas RNAi of MAPK11 in an accession with optimum germination at 15 °C resulted in increased germination. Furthermore, we found that lines overexpressing MAPK11 exhibited hypersensitivity to ABA during germination. These observations were at least partially explained by the fact that MAPK11 up-regulated both NCED1 expression and ABA biosynthesis, and that it also affected ABA signaling and negatively regulated germination by influencing the phosphorylation of SnRK2.2 in vivo. In addition, we found that MAPK11 interacts with and phosphorylates SnRK1 in vivo, thereby potentially inhibiting its activation. SnRK1 interacted with ABI5 and suppressed the transcription of ABI5, thereby affecting ABA signaling and the regulation of germination. Our results demonstrate that ABA signaling in tomato is affected by a mechanism that depends on MAPK11 phosphorylating SnRKs, and this ultimately influences seed germination.

Regulation of seed germination by diurnally alternating temperatures in disturbance-adapted banana crop wild relatives (Musa acuminata)

AbstractSeed conservation of banana crop wild relatives (Musa L. spp.) is limited because of lack of knowledge about their germination ecology. Musa acuminata Colla, the most important banana crop wild relative, is distributed in tropical and subtropical Asian and Pacific rainforests and colonizes disturbed sites. The role of temperature in stimulating/inhibiting germination to detect disturbance when canopy gaps are formed is not well known. We assessed seed germination thermal requirements of three subspecies of M. acuminata using nine seed accessions which had been stored in the Millennium Seed Bank. Diurnally alternating temperature cycles were almost completely essential for germination compared with constant temperatures. Germination was optimal when the upper temperature of a diurnal cycle was at 35°C; the lower temperature of the cycle was less important. Subspecies occurrence coordinates were used to extract climate temperature data which were then compared against the temperature requirements for germination from our experiment results. Maximum temperatures of the warmest month across subspecies ranges were close to but below optimal germination temperatures, as were diurnal ranges, suggesting soil-warming at the micro-climate level following gap creation is important for M. acuminata seed germination. Additionally, pre-treatment for 3 months at 60% relative humidity at constant 25°C improved germination from 14 ± 10 (mean, standard deviation) to 41 ± 29% suggesting a period in the soil seed bank under the canopy may increase sensitivity to alternating temperature cycles. Overall viability was low (49 ± 28%), and considerable variance was caused by the different accessions. Germination remained somewhat inconsistent.

Changes in chemical composition of germinated leguminous under abiotic stress conditions

The aim of this study was to evaluate the impact of abiotic stress conditions on the synthesis of compounds with antioxidant properties in germinating seeds. The seeds of edible lentils (Lens culinaris L.), alfalfa (Medicago sativa L.), and mung beans (Vigna radiata L.) were germinated for 120 hours. We studied the influence of abiotic stress on the amount of dry matter, vitamin C and phenolic compounds, as well as flavonoids, in germinated seeds. The use of higher than optimal germination temperatures led to a higher accumulation of dry matter in the mung bean, while the accumulation of phenolic compounds and flavonoids was higher in the alfalfa sprouted seeds. Oxidative stress substantially increased the content of dry matter in the seeds of mung bean, and more vitamin C was found in the lentils. The conditions of abiotic stress in lentil seeds during their sprouting reduced the amount of phenolic compounds in comparison to that in the control variant of the seeds. However, these same conditions (with the exception of oxidative stress) benefitted the accumulation of phenolic compounds in alfalfa seeds.

Investigating the effects of temperature on seed germination of cutleaf geranium (Geranium dissectum L.) and determination of its cardinal temperatures

Cutleaf geranium is a weed infesting crop fields in various parts of the world. The present study was conducted to determine the cardinal temperatures of germination for its seeds to have a better understanding about temperature needs of this species. Since the seeds were dormant after being harvested, they underwent different dormancy breaking methods. Then, cardinal temperatures were estimated. Among dormancy breaking methods including constant and alternating temperatures, gibberellic acid, H2SO4 and gibberellic acid+ H2SO4 treatments, pre-chilling and after-ripening, after-ripening was the most successful one. Dent and segmented models were the most suitable models for determination of cardinal temperatures. Base, optimum, and ceiling temperatures for dent model were estimated 0.02, 18.97 to 25.32, and 27.00 °C, respectively. These values for segmented model were 0.01, 24.3 and 27.08 °C. The seeds showed high germination uniformity at 15 and 20 °C, but they entered into a state of thermo-dormancy as temperature reached about 27 °C. According to the temperature conditions of the studied region, early sowing of canola will result in the weed being faced with higher than ceiling temperatures. Thus, generalizing, the proper sowing date may be regarded as a feasible management practice in controlling this weed in any given area. This was the first report on estimation of cardinal temperatures in cutleaf geranium.

Evaluating process-based sugarcane models for simulating genotypic and environmental effects observed in an international dataset

Crop modelling has the potential to assist plant breeding by identifying favourable genotypic (G) traits for specific environments (Es). Sugarcane crop models have not been rigorously evaluated against a factorial GxE dataset. It is imperative that models are evaluated in this way before they are applied to plant breeding problems. Our objectives were to (1) calibrate, (2) assess, and (3) identify weaknesses and recommend improvements to, three sugarcane models, DSSAT-Canegro, Mosicas and APSIM-Sugar, in relation to their predictions of observed E, G and GxE interaction effects in response to abiotic factors (temperature and solar radiation). Data from an international GxE growth analysis trial were used; these consisted of five irrigated experiments at four sites (Belle Glade, Florida, USA; Chiredzi, Zimbabwe; La Mare, Reunion Island; and Pongola, South Africa), with cultivars N41, R570 and CP88-1762. Observed G and E effects on final above-ground dry mass (ADM) yields were explained in terms of seasonal radiation interception (FIPARa) and seasonal average radiation use efficiency (RUEa). Calibration was undertaken where possible by translating phenotypic parameters derived from observations into model input trait parameter values representing genetic traits. E and G effects on FIPARa were generally simulated satisfactorily, while GxE interaction effects were poorly predicted due to inadequate responses to temperature. E, G and GxE effects on RUEa were poorly predicted by all models, although data shortcomings (arising from uncertainty regarding date of primary shoot emergence and impacts of lodging) prevented us from making strong conclusions in this regard. Models accurately predicted G differences in RUEa during mid-season biomass sampling periods where data confidence was greater. Although the models were able to predict final ADM yield per G and per E reasonably well, none of the models predicted GxE interaction effects well. All models also under-estimated the variation in RUEa and ADM. Recommendations for experimental protocols for exploring RUEa are made. Our key recommendations for future work to improve models for sugarcane breeding applications are to explore G-specific thermal time base temperatures for germination and canopy development processes, and to improve linkages between carbon availability and canopy development.

Enhancing Conservation of a Globally Imperiled Rockland Herb (Linum arenicola) through Assessments of Seed Functional Traits and Multi-Dimensional Germination Niche Breadths.

Humans currently face an extraordinary period of plant biodiversity loss. One strategy to stem further losses involves the development of species-level recovery plans that guide conservation actions. Seeds represent an important component in the life history of plants and are crucial for conservation activities. Yet, most recovery plans contain meager seed biology information. We set out to examine seed functional traits and germination niche breadth of Linum arenicola seeds exposed to a range of thermal, photoperiodic, and salinity gradients to gain perspectives on the seed biology of this endangered species that may inform conservation decision making and assist recovery plan development. We found that fresh seeds possess non-deep physiological dormancy, which may be alleviated via a four-week dry after-ripening treatment. The germination response of non-dormant seeds is subsequently promoted by constant rather than alternating temperatures. The optimum germination temperature range is 20–22 °C. Non-dormant seeds do not possess an absolute light requirement for germination, but are sensitive to low levels of salinity (EC50 = 6.34 ppth NaCl). The narrow thermal and salinity germination niche breadths reported here suggest a specialized reproductive strategy that may require careful consideration when planning ex and in situ conservation activities.

Tracking optimum temperature for germination and seedling characterization of three millet (Setaria italica) accessions

The research was conducted at the Plant Physiology Laboratory of Research Center for Biology LIPI. The study aimed to provide information about the prediction of millet plant distribution based on temperature for germination. The experiment was arranged based on factorial RCBD. The treatment consisted of two factors, namely accession (Polman, Gambirmanis, and Enggano) and germination temperature (10, 20, 30, and 40°C), with three replications. The seeds were germinated in Petri dish. Each millet accession had distinctive characters. The color of the de-husked grain affected the color of flour, influencing the quality of end-products. The grains color of Accession Polman was white, Gambirmanis had grey color, and Enggano seeds were yellowish. The optimum germination temperature for three millet accessions was: Polman seeds obtained optimum temperature at 40°C, Gambirmanis possessed optimum temperature at 20 – 30°C, and Enggano had the optimum temperature at 10°C. Millet seeds produced a high percentage of germination and the best in seedlings grown at optimum temperature. At this temperature, accession Polman had the best sprout performance overall. Millet seed germinated at the higher temperature (40°C) appeared to be seized, with a low growth rate, except for Polman. It is assumed that millet would be adapted well in the lowlands to highland based on its germination temperature requirement. However, this plant grew optimally in the lowlands with a germination temperature of 30 - 40°C. Conservation of millet species could be done through seed storage with low temperature and humidity.

Comparative Study on Low Temperature Germination Ability of Overwintering Green Manure

Green manure is a biological fertilizer source with complete nutrients, which provides reference for the selection of green manure resistant to low temperature germination. Six green manure crops including Brassica napus L., Orychophragmus violaceus (L.) O. E. Schulz, Medicago sativa L., Lolium perenne L., Melilotus officinalis (Linn.) Pall. and Vicia villosaRoth were selected as experimental materials to study the effects of low temperature stress on germination and seedling growth of different green manure through low temperature germination experiments. The results showed that there were significant differences in cold tolerance of the seeds of 6 medium green manure crops during germination. The germination potential, germination rate, germination index, vitality index, seedling height, root length, seedling fresh weight, soluble protein content and chlorophyll content of Brassica napus L. and Vicia villosaRoth seeds were all better than those of other green manure crops, which provided theoretical basis for the actual production of green manure.

The Candidate Genes Underlying a Stably Expressed QTL for Low Temperature Germinability in Rice (Oryza sativa L.)

BackgroundDirect seeding is an efficient cultivation technique in rice. However, poor low temperature germinability (LTG) of modern rice cultivars limits its application. Identifying the genes associated with LTG and performing molecular breeding is the fundamental way to address this issue. However, few LTG QTLs have been fine mapped and cloned so far.ResultsIn the present study, the LTG evaluation of 375 rice accessions selected from the Rice Diversity Panel 2 showed that there were large LTG variations within the population, and the LTG of Indica group was significantly higher than that of Japonica and Aus groups (p < 0.01). In total, eleven QTLs for LTG were identified through genome-wide association study (GWAS). Among them, qLTG_sRDP2–3/qLTG_JAP-3, qLTG_AUS-3 and qLTG_sRDP2–12 are first reported in the present study. The QTL on chromosome 10, qLTG_sRDP2–10a had the largest contribution to LTG variations in 375 rice accessions, and was further validated using single segment substitution line (SSSL). The presence of qLTG_sRDP2–10a could result in 59.8% increase in LTG under 15 °C low temperature. The expression analysis of the genes within qLTG_sRDP2–10a region indicated that LOC_Os10g22520 and LOC_Os10g22484 exhibited differential expression between the high and low LTG lines. Further sequence comparisons revealed that there were insertion and deletion sequence differences in the promoter and intron region of LOC_Os10g22520, and an about 6 kb variation at the 3′ end of LOC_Os10g22484 between the high and low LTG lines, suggesting that the sequence variations of the two genes could be the cause for their differential expression in high and low LTG lines.ConclusionAmong the 11 QTLs identified in this study, qLTG_sRDP2–10a could also be detected in other three studies using different germplasm under different cold environments. Its large effect and stable expression make qLTG_sRDP2–10a particularly valuable in rice breeding. The two genes, LOC_Os10g22484 and LOC_Os10g22520, were considered as the candidate genes underlying qLTG_sRDP2–10a. Our results suggest that integrating GWAS and SSSL can facilitate identification of QTL for complex traits in rice. The identification of qLTG_sRDP2–10a and its candidate genes provide a promising source for gene cloning of LTG and molecular breeding for LTG in rice.

Effect of seed size on germination in three species from arid Arabian deserts

In many species, seeds with different sizes show diverse responses in their requirements for temperature and light for optimal germination. In this study, the effect of seed size (i.e., small and large) on germination was tested in seeds of Brassica tournefortii Gouan, Lotus garcinii DC., and Salvadora persica L. from arid Arabian Desert habitats. The mean seed size of all three study species differs significantly between small and large-sized seeds. Differences were observed in seed germination between large and small seeds of B. tournefortii and L. garcinii. We found that the large seeds of B. tournefortii and L. garcinii showed a higher germination percentage at all tested temperatures than that displayed by the small seeds. However, both small and large seeds of S. persica germinated equally (100%) well under all tested incubation conditions. Our results show significant differences in germination percentage between the small and large seeds of B. tournefortii at 25/35 °C under a 12 h light regime. However, seeds of L. garcinii showed a significant difference in germination percentage at low temperatures (15/25 °C) under a 12 h light regime.

Study of the storage conditions of Portulaca oleracea L. seeds

The results of optimization of storage conditions of Portulaca oleracea L. seed material is given in thearticle. It is determined that at low positive temperatures germination of seeds decreases by 3 times by the end of thesecond year of storage. The effect of extremely low temperatures on the viability of Portulaca oleracea’s seed material isstudied; optimal cryopreservation conditions are selected: freezing in plastic cryo tubes, slow thawing at room temperature22 °C. It is studied the influence of cryoprotectors on the degree of viability of Portulaca oleracea’s seed material inliquid nitrogen. The optimal cryoprotector is 15 % sucrose solution.

Thermal niche for germination and early seedling establishment at the leading edge of two pine species, under a changing climate

Pines are the most popular species for reforestation in Mexico, however reforestation programs have little success due to a high mortality of pine seedlings. Shifts in the distribution range due to climate change has been predicted for many species specially at their distribution borders. Understanding the thermal limits of germination and early seedling growth at the leading edge population in current and future climates could enable the development of suitable propagation practices and conservation strategies. Seeds of Pinus douglasiana and Pinus maximinoi, from their northern distribution range in a temperate sub humid region, were germinated and seedlings were grown across a range of temperatures from 10 to 35 °C. A cardinal temperature model was then employed to obtain the thermal coefficients for seed germination, seedling growth and survival. Projected temperature increase by 2090 according to IPCC scenarios RCP 2.6 and RCP 8.5 were used to predict the germination and early establishment behaviour of both species. Thermal requirements were similar between species and in different developmental stages showing base temperatures of 9.4−10 °C for germination, 9.8 °C for root growth, 9.6 °C for shoot appearance and 8.4 °C for shoot growth; and thermal time requirements of 65−69 °C d for germination, 107 °C d for root growth, 103−107 °C d for shoot appearance and 140−141 °Cd for shoot growth. However, seedling survival was higher at 20 and 25 °C. Different sensitivities to low temperatures for germination and seedling establishment could be factors that drive ecological divergence between these species and explain their altitudinal tolerances. As timing of germination and seedling growth are expected to be accelerated under climate change scenarios, seedling establishment and survival in both species could be altered .

Physiological dormancy in seeds of tropical montane woody species in Hawai`i

AbstractWorldwide, there is relatively little information on seed dormancy and germination of tropical montane species. Our aim was to help fill this knowledge gap by conducting seed dormancy/germination studies on woody species from this vegetation zone in Hawai`i. All species had water‐permeable seeds with a fully developed embryo. Seeds of 29 species (23 genera) were incubated in light/dark at 15/6, 20/10 and 25/15°C and germination monitored at 2‐week intervals for 16–128 weeks. Seeds of Chenopodium oahuense, Dubautia menziesii and Silene lanceolata were non‐dormant (ND) and those of 26 other species had physiological dormancy (PD); 10 of the 26 species had conditional PD. The optimum germination temperature regime(s) was (were) 25/15°C, 17 species; 25/10 and 20/10°C, 2; 20/10°C, 6; 20/10 and 15/6°C, 2; and 15/6°C, 2. Worldwide, PD in the woody genera included in our study is more common than ND. In addition to its contribution to the world biogeography of seed dormancy/germination, this study will be useful to conservation biologists who need to germinate seeds of tropical montane species.

Seed germination requirements of Hypericum scruglii, an endangered medicinal plant species of Sardinia (Italy)

Hypericum scruglii Bacch., Brullo &amp; Salmeri is an endangered endemic plant of Sardinia, and the phloroglucinol compounds identified in this species have been reported to inhibit the activity of the Human Immunodeficiency Virus. Seed banks are a genetic repository that effectively preserve taxa of conservation interest, and they hold knowledge about the biology and germination ecophysiology of the taxa they preserve. The main goals of this study were to investigate the germination requirements for H. scruglii, to evaluate the seed viability after eight years of long-term conservation and to suggest an efficient protocol for germination. Seeds stored at –25 °C in the seed bank were tested at temperatures from 5 to 30 °C and 25/10 °C. Base temperature (Tb) and thermal time (θ50) for germination were estimated. Seeds of H. scruglii germinated over a wide range of temperatures, responding positively to high temperatures and 25/10 °C. Tb was estimated at 4.92 °C, and θ50 was estimated at 198.27 degree days. The high viability detected in seeds of H. scruglii allows us to suggest the use of seeds stored in a seed bank when fresh material for plant propagation is scarce. Our results provide new and useful baseline information for implementing conservation and multiplication strategies for this endangered medicinal plant.

Effects of temperature and leaf age on conidial germination and disease development of powdery mildew on rubber tree

AbstractPowdery mildew is an important disease of rubber trees worldwide. To assess the effects of temperature and leaf age on conidial germination and disease development, conidia were inoculated onto rubber tree seedlings with leaves at three phenological stages (copper bronze, colour‐changing, and light green) and then incubated at six constant temperatures (10, 15, 20, 25, 30, and 35°C). Leaf age did not affect conidial germination (p = .296) whilst temperature did (p &lt; .0001), although conidia were able to germinate at all tested temperatures. The estimated optimal temperature for conidial germination was 23.2°C. Leaf age, temperature, and their interactions had significant effects on conidial infection and hypha number (p &lt; .0001). At 10 and 35°C, more than 2 and 4 days were needed for infection to complete, respectively, compared to &lt;2, 1, 0.5, and 0.5 days for 15, 20, 25, and 35°C, respectively. Sporulation and mildew symptoms were only observed on those inoculated leaves of all stages at 20 and 25°C, and at the copper bronze stage only at 15°C. The latent period on the copper bronze leaves at 15°C was longer (9 days) than at 20 and 25°C (4 days). The latent period at 20 and 25°C increased from 4 to 7 days as the leaf development stage increased from copper bronze to light green. Therefore, temperature affected germination and postgermination growth of rubber tree powdery mildew, whereas leaf age primarily affected postgermination growth of the pathogen.