Final Germination Percentage Research Articles

Annual Garden Rocket and Radish as Microgreens: Seed Germination Response to Thermal and Salt Stress

Temperature and salinity level of the imbibition medium play a crucial role in regulating seed germination and seedling emergence, which is also true in microgreen production, where temperature and water potential may influence seed germination alone and/or in combination. In this study, the effects of different temperatures and water potentials in NaCl, alone or in combination, upon germination and early radicle growth, were assessed in two species for microgreen production (Eruca sativa-rocket, and Raphanus sativus-radish). Seeds were germinated at eight constant temperatures (from 5 to 35 °C) and five water potentials (ψ) in NaCl (from 0 to −1.2 MPa). Final germination percentage (FGP) was maximized at 15–20 °C in rocket, and at 20–25 °C in radish. As the temperature increased or decreased, germination was reduced and became less uniform, to a greater extent, at suboptimal temperatures in both species. Across water potentials, FGP values exceeding 50% at the highest temperature in radish indicated a greater tolerance than rocket to supraoptimal temperatures during germination. Across temperatures, FGP and germination speed in both species were progressively depressed as the water potential decreased. The adverse effects of NaCl progressively increased as the temperature moved away from its optimal value. Overall, rocket seeds were able to germinate well (>80%) at 20 °C at salinity levels down to −0.9 MPa, while radish seeds were able to germinate well (≥90%) at 25 °C at salinity levels down to −0.9 MPa. Salt stress tolerance was higher in rocket and radish at low and high temperatures, respectively. Both thermal time and hydrotime requirements were higher in radish because its seeds took longer to germinate. Thermal time and hydrotime may help to predict the germination capacity and time, once the temperature or water potential of the imbibition substrate is known. The findings of this study have important implications for the large-scale industrial production of microgreens.

Rhizobium Inoculants Mitigate Corn Herbicide Residual Effects on Soybean Germination

Corn residual herbicides offer a practical approach to comprehensive weed management throughout the growing season. However, the use of residual pre-emergence herbicides can have a negative impact on crops grown in succession or within a rotation. A study was carried out to determine the effect of the residual activity of selected corn herbicides on soybeans. The objective of the study was to evaluate the impact of these herbicides on the germination of inoculated soybean seeds. Experiments were conducted in greenhouse conditions to check the carryover effect on soybean germination. Treatment combinations of two pre-herbicides and two inoculants were applied: atrazine (2241 g ai ha−1), mesotrione (105 g ai ha−1), and Bradyrhizobium japonicum, Bradyrhizobium japonicum + Bacillus subtilis, respectively. A randomized complete block design evaluated six treatment combinations, including the control. All treatments, except uninoculated treatments, presented efficacy in reducing the carryover effects of corn residual herbicides on the germination of soybeans. An increase in final germination percentage was observed with Bradyrhizobium japonicum + Bacillus subtilis co-inoculation plus atrazine (24% increase) and Bradyrhizobium japonicum plus mesotrione treatment combinations (19% increase). Inoculating soybean seeds with rhizobium bacteria can reduce the carryover effects on the germination of soybean seeds grown in soil applied with atrazine and mesotrione.

Effects of Green-Synthesised Copper Oxide–Zinc Oxide Hybrid Nanoparticles on Antifungal Activity and Phytotoxicity of Aflatoxin B1 in Maize (Zea mays L.) Seed Germination

Maize contamination with aflatoxin B1 (AFB1) is of significance on a global scale due to its major contribution to food security. It is very probable that substantial amounts of AFB1 may be absorbed by germinating seeds grown in contaminated soil and cause deleterious effects on the growth and development of maize. In this study, the effect of green-synthesised ZnO-CuO hybrid nanoparticles (NPs) on antifungal activity and reducing the toxic effects of AFB1 on seed germination was examined. A notable inhibitory effect of green-synthesised ZnO-CuO nanoparticles (NPs) on A. flavus was observed at a concentration of 0.5 ppm, resulting in 13.1% inhibition, which was more effective than the higher concentration of 1.0 ppm and the control. The results showed that the final germination percentage of the seeds that were inoculated with 320 ppb was significantly increased by the treatment with 125 mg/mL of green ZnO-CuO hybrid NPs. This study indicated the potential of green-synthesised ZnO-CuO hybrid NPs as alternative antifungal agents to control aflatoxin production in maize to improve food security and safety by supressing the threat posed by AFB1.

Effect of abiotic factors in seed germination of the medicinal aromatic plant Ziziphora hispanica L.

Summary Ziziphora hispanica L. (Lamiaceae) is a medicinal aromatic plant which is native to Algeria in semi-arid regions, Morocco and southern Spain. Despite the medicinal and economic interests as well as the uncertain future that this species may encounter in its natural habitats, various aspects of the biology of its seeds have not been recognized up to date. To fulfill these gaps, seed germination has been studied under the effect of different incubation temperatures, and under the influence of defer-ential concentrations of water stress and saline stress. The seeds were first incubated at different temperatures (15, 20 and 25°C). Then, at 20°C, germination studies were carried out at various sodium chlo-ride concentrations (0, 25, 50, 75 and 100 Mmol /l) and various solutions of polyethylene glycol (PEG6000) (0, -0.2, -0.4, and-0.6 Mpa). The results showed that Z. hispanica seeds were not dormant, and the optimal temperature of germination was 20°C, at which the maximum final germination percentage occurred (94%). A high negative correlation was obtained between the germination percentage and the various concentrations of NaCl. In comparison to other plant species that share its habitats, the results of the water stress impact tests indicate that Z. hispanica is very sensitive to water stress, indicating difficulties in germinating in semi-arid and arid regions and that climate change may restrict its natural habitats. The results of this study can serve as guidelines for propagation protocols of this species to support its conservation and cultivation.

Breaking seed dormancy in Searsia pentaphylla(Anacardiaceae)

Seeds (true seed plus endocarp) of Searsia pentaphylla, a species with significant medicinal, ecological and horticultural importance, have an extremely hard and water impermeable endocarp. Hence, effective dormancy- breaking techniques are crucial for enhancing its cultivation and ensuring successful establishment in both natural and managed environments. This study evaluated the effects of mechanical scarification, chemical scarification (sulphuric acid soaking for 30, 60, 90 and 120 minutes, hydrogen peroxide soaking for 10 minutes), hot water soaking for 10 minutes, and heat treatment for three minutes at 200°C on final germination percentage (FGP), mean germination time (MGT), time to 50% germination (T50), coefficient of velocity of germination (CVG) and mean daily germination (MDG). Compared to the control group (untreated seeds), the most effective treatment was 120 minutes of sulphuric acid soaking, achieving a FGP of 92%, a MGT of 7.28 days, a CVG of 13.7%, a T50 of 6.67 days and a MDG of 6.57%. Mechanical scarification yielded a FGP of 36.5%, with poorer MGT, CVG, T50 and MDG values. Other methods, including hydrogen peroxide and heat, were less effective. These results highlight the importance of aggressive scarification techniques to enhance germination in S. pentaphylla.

Underdeveloped embryo and dormancy type in seeds of the Cyananthus formosus, an endemic species of alpine scree habitat in the Hengduan Mountains region of southwest China

We investigated the seed dormancy and germination characteristics of Cyananthus formosus, an endemic species of Hengduan Mountains in China that is narrowly distributed in alpine scree habitats. The mean embryo length (E) to seed (S) length ratio was determined for fresh and cold stratified (CS) seeds, and for seeds at the time the seed coat split but before radicle emergence. Germination of freshly matured seeds was tested in light and dark at six constant (1, 5, 10, 15, 20 and 25°C) and three alternating (5/1, 15/5 and 25/15°C) temperatures and again, after six months of dry CS and after-ripening (DAR). Embryos grew inside the seed prior to germination (123% increase in E:S ratio). Fresh seeds germinated to > 90% at 20, 25 and 25/15°C within four weeks in light, but germination was significantly lower at 1, 5, 10, 5/1 and 15/5°C. CS increased final germination percentage, germination rate and widened the temperature range for germination from high to low, regardless of light conditions. DAR significantly increased the final germination percentage, particularly at 15 and 15/5°C, while it had no effect on the germination rate. The germination characteristics described herein hindered seed germination during autumn dispersal under low temperatures, while facilitating germination following snowmelt in spring. We concluded that the majority of C. formosus seeds had nondeep simple morphophysiological dormancy, while a minority of seeds exhibited morphological dormancy. To the best of our knowledge, this is the first report on embryo growth and dormancy type in Cyananthus species.

Impact of organic and inorganic growth regulators with two soaking time duration on germination indices and seedling vigor of Pigeon pea (Cajanus Cajana (L) Millspaugh) seeds

A two factor pots experiment was conducted during winter season of 2018/2019 investigate effects of two growth regulator and soaking time on germination indices and seedling vigor of Pigeon pea seeds. The experiment was laid out according RCBD with three replications. Parameters studied include germination indices; Final germination percentage FGP, Mean daily germination MDG, Daily germination speed DGS and vigor index. Also, seedling dry weight, length and root length were measured. The results indicated that soaking seeds of pigeon pea enhanced germination behaviors and seedling characters. Application of GA or lemon at medium level concentration increased all characters measured in this study particularly under longer time of soaking. The positive effected of soaking with water with combination of GA significantly increased germination indices and seedlings growth characters. In conclusion, as a result, soaking seeds of pigeon pea with application of medium growth regulator concentrations could increase the seed germination indices and seedling growth characters.

Principal Component Analysis in Kodo Millet (Paspalum scrobiculatum) under Salt Stress Conditions

The study was carried out in a polyhouse using germination trays to examine the impact of salt stress on seedling growth and germination across 42 Kodo Millet genotypes. Conducted at the Research Farm of RVSKVV, Gwalior, the experiment followed a Completely Randomized Design (CRD) with three replications. To minimize variability and maintain uniform conditions, a standardized growing medium composed of compost, vermiculite, and cocopeat in a 1:1:1 ratio was employed. Salt stress levels were assessed using NaCl solutions at concentrations of 50 mM, 100 mM, 250 mM, and 500 mM. In this study, two principal components with eigen values greater than one collectively accounted for 72.2% of the total variability among the analyzed traits. The first principal component (PC1) contributed the most, explaining 63.05% of the variation, while the second principal component (PC2) explained 9.15%. PC1 was primarily associated with traits such as days to emergence, final germination percentage, shoot length, seedling length, shoot fresh weight, root fresh weight, total fresh weight, total dry weight, and proline content. In contrast, PC2 was dominated by traits such as root length, vigor index, chlorophyll a, and chlorophyll b. The scores for PC1 ranged from 0.002 to 3.795 for positive values and -7.521 to -0.034 for negative values, while PC2 scores ranged from 0.061 to 2.894 for positive values and -2.687 to -0.089 for negative values. Scree plot and biplot collectively highlighted the major contributors to variability and their interrelationships under the salt stress condition in kodo millet genotypes.

Orchid embryo-to-seed (E:S) ratio as an indicator of germination behaviour and its ecological implications

Abstract Although the seeds of various Orchidaceae members can be readily germinated on sterile nutrient media, numerous species exhibit complete asymbiotic germination failure. Also, while seed morphology in orchids has been previously linked to dispersal, associations with germinability have not been widely explored. We compiled seed morphometric and germination data for 203 orchid species globally, drawing from international literature and our lab's unpublished findings. Based on (a) final germination percentage and (b) pre-treatment duration, two distinct groups of asymbiotic germination behaviour emerged – termed compliant and defiant, respectively. Additionally, a statistically significant relationship between germinability and the embryo-to-seed (E:S) length ratio was observed. E:S values tended to be lower in species with defiant germination and higher in those with compliant germination. We further correlated seed morphometric and germination data with phylogenetically and ecologically significant parameters (subfamily, growth form, mycoheterotrophy level, climatic zone and habitat shadiness). Notably, lower E:S values and defiant germination predominate in orchids of shaded habitats, while compliant germination is more prevalent in open habitats. Lastly, considering the mycoheterotrophy continuum, we propose that the reduction in the E:S ratio is linked to the adaptation of various orchid lineages to shaded habitats through both an increased dispersal ability and their greater reliance on fungal symbiosis.

Effect of salt stress on the germination of Silene hicesiae (Caryophyllaceae), an insular endemic from the Tyrrhenian hot-spot

The increase in soil salinity, being a global trend in the actual scenario of environmental changes, may represent a threat to the conservation of endangered plant species. The effect of salt stress is stronger during earlier stages of plant life and to study its effect on seed germination is crucial when planning seed-based restoration of endangered plant populations. Silene hicesiae is a threatened endemic species of the Aeolian Islands (Italy). The effect of salt stress on seed germination was evaluated using NaCl and its alleviation by KNO3 was tested in two factorial experiments, investigating, respectively, the interactive effect of salt stress, KNO3 and temperature and the interactive effect of NaCl, KNO3 and seed size. To assess the recovery ability of seeds, non-germinated seeds were re-sown in water-agar. Final germination percentage of S. hicesiae decreased with increasing NaCl concentration and temperature. KNO3 did not alleviate salt stress. Seed size did not influence germination as main effect but in interactions with NaCl and KNO3. Seed viability was not excessively compromised by salinity but recovery was lower for seeds incubated at 20 °C and for small seeds. These findings should be considered when planning in-situ reinforcement action by direct seed sowing.

Seed dormancy and germination in Sophora secundiflora (Fabaceae)

Given the ecological and horticultural significance of Sophora secundiflora (Ortega) DC., effective dormancy-breaking techniques are crucial for enhancing its cultivation and ensuring successful establishment in both natural and managed environments. Seeds have an extremely hard and water impermeable testa. This study evaluated the effects of mechanical scarification (MS), sulphuric acid (SA) soaking for 30, 60, and 90 minutes, and hydrogen peroxide (HP) soaking for 10 and 20 minutes on final germination percentage (FGP), mean germination time (MGT), time to 50% germination (T50), and coefficient of velocity of germination (CVG). Mechanical scarification and 60-minute sulphuric acid treatments were the most effective, achieving FGPs of 95% and 93%, respectively, and showing efficient germination processes as indicated by T50 and CVG metrics. Mechanical scarification resulted in the fastest and most consistent germination. Sulphuric acid treatments showed time-dependent efficacy, with the 60-min treatment optimizing both germination speed and percentage, whereas the 90-min treatment caused potential seed damage, reflected in a lower FGP. Hydrogen peroxide treatments were less effective overall, with a maximum FGP of 33% for the 20-minute soaking. Statistical analysis highlighted significant differences among treatments, particularly for FGP (p < 0.0001), T50 (p = 0.0020), and CVG (p = 0.0348). These findings align with existing research on Fabaceae species, supporting the importance of physical and chemical scarification methods in breaking seed dormancy. This study provides critical insights into optimizing germination protocols for S. secundiflora, with wider applications for other hard-seeded Fabaceae species.

Proline and Glycine Betaine: A Dynamic Duo for Enhancing Salt Stress Resilience in Maize by Regulating Growth, Stomatal size, and Oxidative Stress Responses

Proline and Glycine Betaine: A Dynamic Duo for Enhancing Salt Stress Resilience in Maize by Regulating Growth, Stomatal size, and Oxidative Stress Responses

Response of sweet pepper (Capsicum annuum) to different priming treatments on germination and early growth

Production of pepper (Capsicum annuum) is reduced by poor stand as a result of poor germination due to physiological dormancy of the seed. Therefore, a laboratory experiment was carried out to evaluate the response of sweet pepper to pre-sowing treatments, with the objective of improving seed germination and growth. The experiment used Completely Randomised Design (CRD) with four treatments replicated four times. The treatments were pre-soaking in water for 24 hours before planting; pre-chilling at 100C for 7 days before planting; pre-soaking in Potassium nitrate (KNO3) at 2.4g per 1.2 liters distilled water for 24 hours and; untreated seed (control). The parameters measured were days to 50% germination, final germination % (FG%), speed of germination, mean germination time (MGT), radicle, plumule, seedling length, and seedling vigor index. The results showed that the pre-sowing treatment of seed with KNO3 and pre-soaking in water significantly (p < 0.01) increased germination percent of sweet pepper seeds. Pre-chilling and no treatment of sweet pepper seed resulted in significant reduction of final germination percentage, radicle, plumule and seedling lengths and seedling vigor index. Results also showed an increase in number of abnormal and dead seed were pre-chilling and no treatments were used. Basing on these findings, farmers are recommended to pre-soak sweet pepper seed in KNO3 and water before sowing to enhance seed germination.

Machine Learning Insights into Ascorbic Acid-Enhanced Germination of Black Cumin (Nigella sativa L.) under Cadmium Stress

AbstractThe objective of the present work is to study the impact of seed priming with varying concentrations of ascorbic acid (vitamin C) on the germination process of black cumin (Nigella sativa) under cadmium (Cd) stress. As expected, Cd had a great effect on germination rates and seedling growth. However, the application of ascorbic acid during seed priming effectively alleviated Cd stress and significantly increased seed vigor. Primed seeds exhibited markedly elevated final germination percentage, germination index, mean germination time, seedling length, seedling vigor index, and reduced abnormal seedling percentage. Additionally, vitamin priming reduced membrane lipid peroxidation, in treated seeds. Moreover, seed priming elicited a considerable increase in peroxidase and catalase activity, thus mitigating stress effects and augmenting seed vitality. Our experimental data allowed us to establish 100–150 mg/L as the optimal concentration range for ascorbic acid in seed priming of black cumin. These insights were further corroborated through modeling techniques based on supervised machine learning. Notably, XGBoost emerged as a proficient tool for predicting final germination percentage, mean germination time, seedling vigor index, abnormal seedling percentage, and peroxidase activity, while SVR demonstrated aptitude in forecasting catalase activity and germination index. The Gaussian method exhibited superior performance in predicting malondialdehyde content. These comprehensive findings substantiate the premise that vitamin priming with ascorbic acid serves as a promising strategy to ameliorate germination outcomes under Cd-induced stress conditions.

NaCl salt stress and PEG water stress differentially affect germination and early seedling growth of two sesame (Sesamum indicum L.) cultivars

Drought stress and salt stress are serious challenges to crop productivity in the arid lands. This work investigates the impact of NaCl-salt stress and PEG-water stress on germination and embryo growth of two sesame (Sesamum indicum L.) cultivars: Sohag 1 (Sohg) and Shandaweel 3 (Shnd). Seed dimensions, volume and weight were measured. The red Sohg seeds were larger with oblong appearance and lower density relative to the white Shnd seeds. Seeds were germinated in isosmotic solutions of NaCl and PEG-6000 at 0, − 0.103, − 0.205, − 0.410 and − 0.615 MPa. The time-based parameters (velocity, uniformity and synchrony of germination) were more reliable measures of germination efficiency than the final germination percentage. The impact of PEG was more severe than that of NaCl particularly on Sohg. The peak of daily germination was lowered and delayed under stress. The genotypic variability in germinability became evident under stress in favor of Shnd. Radicle length–a reliable measure of seedling growth–was subjected to stronger impact of NaCl than PEG. Although Na+ mobilization from seeds to embryos was indifferent in the two cultivars in PEG solutions, Shnd seedlings exhibited higher Na+ uptake from NaCl solutions. Whereas K+ mobilization was restricted by NaCl only in Sohg, it was hastened by PEG equally in the two cultivars. The stress-vulnerable Sohg recovered from stress with higher magnitude than did Shnd, particularly from the more stressing osmoticum (PEG). The indices of germination recovery were highest in PEG-pretreated Sohg while the biomass of recovered seedlings was highest in NaCl-pretreated Sohg.

Evaluation of Germination and Early Seedling Growth of Different Grasses Irrigated with Treated Mine Water

Coal mining is known to have negative impacts on the environment, necessitating land rehabilitation after mining activities. Amongst the problems associated with coal mining is the accumulation of acid mine drainage characterized by large amounts of heavy metals and high acidity. The impact of these environmental problems on the ecosystem around mining areas underscores a need to devise strategies that will ensure sustainable restoration of the ecosystem integrity to ensure environmental protection. Of these, treatment of acid mine drainage using calcium sulfate dihydrate, which is subsequently used for irrigation during phytoremediation, holds great promise for restoration of open-cast mines. However, although grasses are used for rehabilitation of coal mined areas, the impacts of treated mine water on the germination, seedling emergence, and plant growth of grasses are not well known. The aim of the study was to evaluate the germination and early seedling growth responses of different forage grasses to treated mine water. Seven forage grass species were selected, with four species represented by two varieties while others were represented by one variety, totaling 11 forage grasses. For each plant entry, 100 seeds were placed in J.R. Petri’s dishes lined with Whatman No. 2 filter paper and watered with distilled and mine water to assess germination. For the seedling establishment experiment, only five species were studied, in which twenty seeds per species were sown in pots containing mine soil and irrigated using distilled and treated mine water. The final germination percentage (FGP), germination rate index (GRI), corrected germination rate index (CGRI), and T50 were determined for the germination trail and total biomass was assessed for the seedling growth trail. The highest FGP for all grasses was attained under controlled conditions, using distilled water, ranging from 38–94%. All grasses germinated when watered using treated mine water and had a FGP ranging from 20–91%. Relative to distilled water, GRI and CGRI were highest only for L. multiflorum cv AgriBoost when seeds were watered using the treated mine water. All grasses watered with treated mine water produced high biomass for the first two weeks, after which biomass production started to decline. Two grasses, Eragrostis curvula cv Ermelo and Lolium multiflorum cv Archie, showed tolerance to treated mine water irrespective of its high electrical conductivity (557 mS∙m−1). Therefore, these grasses could be used in the rehabilitation of coal-mined areas irrigated with treated mine water.

Copper mitigates salinity stress by regulating water status, photosynthetic pigments and ion homeostasis and increases the yield of Eggplant (Solanum melongena)

Eggplant (Solanum melongena) is moderately sensitive to salinity. Seed priming and exogenous supplementation are technique that enhances germination, growth, and crop yield by overcoming salt stress. Therefore, this study was designed to understand the role of seed priming and copper (Cu) supplementation in modulating salt tolerance in eggplant. When exposed to salt stress, eggplant seedlings showed significantly higher Na+ content, an increased Na/K ratio, prolonged mean germination time, higher relative water loss, more days to flower bud initiation and first flowering, along with decreased germination rate, growth factors, water content, photosynthetic pigments, ionic contents (K+, Ca2+, Mg2+), and yield. The results demonstrated that the germination rate, final germination percentage, germination index, germination energy, and seed vigor index significantly improved, while the mean germination time decreased in Cu-primed seeds. The results also revealed that Cu supplementations increased seedling traits, leaf water content, photosynthetic pigment contents, ionic contents (K+, Ca2+, and Mg2+), and yield while decreasing the contents of Na+, and Na/K ratio, mean germination time, relative water loss, days to flower bud initiation, and days to 1st flowering under salt stress. Germination of seeds, seedlings growth traits, plant water status, plant pigments, yield, and ionic contents with the NaCl and Cu treatments were found to substantially interact with each other according to both hierarchical clustering and PCA. Overall, Cu seed priming and exogenous supplementation emerged as a promising strategy to enhance salt tolerance and promote germination, growth, and yield by regulating water status, photosynthetic pigments, and ion homeostasis in eggplant seedlings under NaCl stress. These findings provide valuable insights into the mechanisms of Cu-mediated stress alleviation in eggplant, with implications for sustainable crop production in saline environments.

Effect of seed priming and seed rate on the performance of wheat (Triticum aestivum)

A field experiment was carried out to determine the impact of different seed rates and priming strategies on germination percentage, growth attributes and yield of wheat. The experiment comprised of twelve treatments i.e. dry seed surface seeding; 12 hour soaked seed surface seeding; seed priming with 1% KNO3 and seed priming with 1% CaCl2 at 100, 125 and 150 kg/ha seed rate. The results indicated that highest final germination percentage (84 %) at 10 DAS was found with seed priming with 1% CaCl2 at 100 kg/ha seed rate. The tallest plant was observed with seed priming with 1% CaCl2 at 150 kg/ha seed rate. However, number of tiller/m2 and dry matter accumulation was recorded maximum with seed priming with 1% CaCl2 at 150 kg/ha seed rate, which was 7.27% and 20% higher compared to number of tillers/m2 and dry matter accumulation under dry seed surface seeding with 100 kg/ha seed rate respectively. Among different treatments, highest grain yield (4662 kg/ha) and straw yield (5694 kg/ha) were found with seed priming with 1% CaCl2 at 150 kg/ha seed rate. Similarly, maximum gross (₹114851/ha) and net (₹76884/ha) returns were obtained in seed priming with 1% CaCl2 at 150 kg/ha seed rate but highest B: C ratio (3.09) obtained with seed priming with 1% CaCl2 at 125 kg/ha seed rate. Hence, adopting seed priming strategies at different seed rates can improve growth and yield of wheat.

Intrapopulation germinability may help the Mediterranean plant species Poterium spinosum L. to cope with climate changes and landscape fragmentation.

Poterium spinosum L. is a key plant species forming typical shrub communities, distributed across the Mediterranean eastern coasts. The conservation of P. spinosum is thus of the utmost importance, especially due to the ever-increasing environmental pressures like climate changes and habitat fragmentation. This study, in particular, investigated for the first time the germination variability of P. spinosum at intrapopulation level, by analysing the germination behavior of five different subpopulations growing along the coasts of Sicily. For a more exhaustive picture of the main drivers of biodiversity loss affecting the distributional area of P. spinosum, the trends of climate and land-cover changes were also studied over the periods 1931-2020 and 1958-2018, respectively. The results found significant intrapopulation variability in P. spinosum, whose germination parameters showed that fruits and seeds from distinct subpopulations respond differently to diverse temperatures. Seeds showed generally higher values of final germination percentage (FGP) compared to fruits, and at higher temperatures: the highest FGP in seeds was 70% at 20°C, whereas in fruits was 58.2% at 15°C. The environmental threats showed worrying trends across the study area: during 1931-2020, the average temperature increased by 1.5°C, whereas the average rainfall declined from 710 to 650mm. Similarly, in the period 1958-2018, the analysis of the CORINE land-cover changes showed a highly fragmented agricultural landscape, where natural areas were reduced to 2.5-5.0%. Germination variability at intrapopulation level should be considered as a fundamental adaptation strategy, which can increase the reproductive success of P. spinosum under climate and land-cover changes.

Characterization of Bipolaris bicolor germination: effects of a physical factor on fungal adaptability.

Studies on physiological responses to stimuli from physical factors are essential for understanding the dynamics of the microorganisms and higly important for the management of plant diseases. Besides, the development of an epidemiological model for pathogen populations requires studying their physiological responses to physical stimuli. The objective of this study was to evaluate the germination dynamics of spores from six isolates of Bipolaris bicolor under effects of light at 25°C. Suspensions of 1.6 × 105 conidia mL- 1 from the B. bicolor isolates were inoculated onto Petri dishes containing agar-water culture medium and incubated in a BOD chamber under two physical conditions: (a) constant darkness and (b) constant light for five hours. The study was conducted in a completely randomized design, with a 6 × 2 factorial arrangement (six B. bicolor isolates and two physical conditions) and five replications. The length of the germ tube was measured hourly. The constant darkness resulted in higher mean germ tube growth for the pathogen; however, differences in the final germination percentage were found among the isolates. The isolate F-24-02 exhibited the highest germination adaptability to constant darkness, presenting the longest germ tube length.