Precocious Germination Research Articles

Current Insights into Weak Seed Dormancy and Pre-Harvest Sprouting in Crop Species.

During the domestication of crops, seed dormancy has been reduced or eliminated to encourage faster and more consistent germination. This alteration makes cultivated crops particularly vulnerable to pre-harvest sprouting, which occurs when mature crops are subjected to adverse environmental conditions, such as excessive rainfall or high humidity. Consequently, some seeds may bypass the normal dormancy period and begin to germinate while still attached to the mother plant before harvest. Grains affected by pre-harvest sprouting are characterized by increased levels of α-amylase activity, resulting in poor processing quality and immediate grain downgrading. In the agriculture industry, pre-harvest sprouting causes annual economic losses exceeding USD 1 billion worldwide. This premature germination is influenced by a complex interplay of genetic, biochemical, and molecular factors closely linked to environmental conditions like rainfall. However, the exact mechanism behind this process is still unclear. Unlike pre-harvest sprouting, vivipary refers to the germination process and the activation of α-amylase during the soft dough stage, when the grains are still immature. Mature seeds with reduced levels of ABA or impaired ABA signaling (weak dormancy) are more susceptible to pre-harvest sprouting. While high seed dormancy can enhance resistance to pre-harvest sprouting, it can lead to undesirable outcomes for most crops, such as non-uniform seedling establishment after sowing. Thus, resistance to pre-harvest sprouting is crucial to ensuring productivity and sustainability and is an agronomically important trait affecting yield and grain quality. On the other hand, seed color is linked to sprouting resistance; however, the genetic relationship between both characteristics remains unresolved. The identification of mitogen-activated protein kinase kinase-3 (MKK3) as the gene responsible for pre-harvest sprouting-1 (Phs-1) represents a significant advancement in our understanding of how sprouting in wheat is controlled at the molecular and genetic levels. In seed maturation, Viviparous-1 (Vp-1) plays a crucial role in managing pre-harvest sprouting by regulating seed maturation and inhibiting germination through the suppression of α-amylase and proteases. Vp-1 is a key player in ABA signaling and is essential for the activation of the seed maturation program. Mutants of Vp-1 exhibit an unpigmented aleurone cell layer and exhibit precocious germination due to decreased sensitivity to ABA. Recent research has also revealed that TaSRO-1 interacts with TaVp-1, contributing to the regulation of seed dormancy and resistance to pre-harvest sprouting in wheat. The goal of this review is to emphasize the latest research on pre-harvest sprouting in crops and to suggest possible directions for future studies.

Cryptovivipary: A rare phenomenon in monoecious species of Ficus L. (Moraceae)

Vivipary in Angiosperms refers to the precocious germination of offspring while they persist on the mother plant. True vivipary and pseudovivipary represent distinctive and adaptive strategies in plants. This phenomenon has never been documented in the genus Ficus (Moraceae family) before. The family Moraceae showcases a remarkable variety of floral structures, methods of pollination, and reproductive mechanisms. The present study is the first to document cryptovivipary in three monoecious fig species. The occurrence of this rare phenomenon could be plants' non-adaptive approach, as well as the influence of the microenvironment surrounding the seed of the species. Based on the observations made in this study, cryptovivipary in these three species appeared to be promoted by high levels of moisture, along with the microenvironment within the syconium that is encountered after seed maturation. Vivipary was documented predominantly during the heavy rainfall period in the monsoon season, spanning from late May to early August 2022, with July being the peak period. Nonetheless, it is important to acknowledge the limitations of this study in that it was not possible to investigate the survival and outcomes of viviparous offspring in comparison to non-viviparous seedlings, primarily due to resource limitations during the experimental period. Subsequent studies on reproductive biology, followed by seed setting and the effect of microenvironment inside syconia could advance our understanding of evolutionary factors and the influence of vivipary on seed production and survival in natural settings.

To eat or not to eat: premature sprouting (vivipary) in cereal and fruit crops

Vivipary also known as the precocious germination of seeds while still attached to the mother plant or fruit, it’s a relatively common phenomenon in angiosperms. However, the proliferating seedlings though interesting to look at, deter customers from eating the fruits. Similarly, vivipary is an adverse phenomenon for the agroindustry because of the lowest quality and palatability of fruits as well as lower seed set and viability. This paper highlights the taxonomic occurrence of vivipary in cereal and crop plants and the detrimental effects of this phenomenon in agricultural crops. According to literature sources, there are 38 fruit crops in which vivipary has been reported. The families Cucurbitaceae, Poaceae, Rutaceae, and Solanaceae include the fruits with the highest incidence of vivipary in the markets.

An improved in-vitro regeneration protocol using scutellum of mature and immature embryos of wheat

Generally, conventional practices take a long time to improve agronomic traits in common wheat (Triticum aestivum L.). However, biotechnological tools provide the best opportunity to enhance crop potential within a limited time. A simple and repeatable protocol for wheat regeneration is the priority for transforming the genetic makeup of elite wheat cultivars. Among 10 types of callus induction media (CIM), CIM4 with supplemented Murashige and Skoog (MS) media+ dicamba (2 mg/l) has 98.22 and 97.33% callus induction efficiency (CIE) in immature and mature scutellum, respectively. Precocious germination, considered a key barrier during callus induction, was fully controlled by excising the embryonic axis. Among 29 different shoot induction media (SIM) assessed in the study, SIM 29 containing zeatin 5 mg/l, 6-benzylaminopurine (BAP) 5 mg/l, 2,4-dichlorophenoxyacetic acid (2,4-D) 0.25 mg/l,1-naphthaleneacetic acid (NAA) 0.25 mg/l, and copper sulfate (CuSO4) 20 mg/l was found most responsive for shoot induction. The combined effect of cytokinin and CuSO4 resulted in an improved wheat regeneration response in two popular Indian wheat varieties, namely HD2967 and HD3171. Rooting was observed at 100% using IAA and IBA @ 0.2 mg/l concentration in root induction media (RIM). The whole in-vitro regeneration protocol from embryo to transfer in the greenhouse took 8 to 9 weeks. The in-vitro regeneration protocol developed in the present study could further be utilized to improve the genetic makeup of elite wheat cultivars utilizing genetic engineering tools.

Contrasting responses to climate variability generate seasonal priority effects between native and invasive forest herbs

Abstract Invasive plants are often characterized by rapid germination and precocious phenology. Theory suggests that early germination may provide invaders with a competitive advantage over slower germinating natives, but the relative contribution of rapid germination versus other intrinsic competitive traits (e.g. rapid growth, high fecundity, broad environmental tolerance) to the success of invaders is poorly understood. Depending on the relationship between germination and competition, shifts in germination phenology due to climate change may increase the dominance of invaders or buffer communities against their impacts. We investigated the link between temperature variation, germination phenology and competitive interactions with a sequence of controlled environment experiments. First, we evaluated the relationships between temperature variation and germination phenology for two herbaceous species found in North American woodlands, the non‐native Hesperis matronalis and native Cryptotaenia canadensis. We then leveraged temperature‐response differences to manipulate the relative germination phenology of these taxa and quantified the effects of their phenological differences on competition. Seeds of the invasive H. matronalis germinated rapidly, reaching 50% germination in under 10 days in all treatment combinations. C. canadensis did not reach 50% germination with less than 7 weeks of cold stratification. However, with more than 10 weeks of cold stratification and low (20/10°C) incubation temperatures, the germination phenology of C. canadensis was well‐matched to that of H. matronalis. When grown together, we found that precocious germination phenology doubled the competitive impact of H. matronalis relative to its other intrinsic competitive traits. Phenological advantage of just 2–3 days relative to C. canadensis was enough to secure competitive dominance at the seedling stage. Synthesis. This study revealed that the mechanistic link between the germination phenology and competitive success of an invasive plant can be strongly mediated by climate sensitivity differences between introduced and native species. Climate change will likely exacerbate these differences, especially in regions where warming reduces cold stratification. Our findings suggest that phenological diversity in native plant communities is an important property of invasion resistance. The relationship between environmental variation, germination dynamics and competition provides a path forward for forecasting climate change impacts on seasonal community assembly and highlights the need to incorporate phenological diversity in restorations.

QTL mapping and improvement of pre-harvest sprouting resistance using japonica weedy rice.

The stability of cultivation and production in terms of crop yield has been threatened by climate change due to global warming. Pre-harvest sprouting (PHS) is a threat to crops, especially staple foods, including rice, because of reductions in yield and quality. To address the problem of precocious germination before harvest, we performed quantitative trait loci (QTL) analysis for PHS using F8 RILs populations derived from japonica weedy rice in Korea. QTL analysis revealed that two stable QTLs, qPH7 and qPH2, associated with PHS resistance were identified on chromosomes 7 and 2, respectively, explaining approximately 38% of the phenotypic variation. The QTL effect in the tested lines significantly decreased the degree of PHS, based on the number of QTLs included. Through fine mapping for main QTL qPH7, the region for the PHS was found to be anchored within 23.575-23.785 Mbp on chromosome 7 using 13 cleaved amplified sequence (CAPS) markers. Among 15 open reading frames (ORFs) within the detected region, one ORF, Os07g0584366, exhibited upregulated expression in the resistant donor, which was approximately nine times higher than that of susceptible japonica cultivars under PHS-inducing conditions. Japonica lines with QTLs related to PHS resistance were developed to improve the characteristics of PHS and design practical PCR-based DNA markers for marker-assisted backcrosses of many other PHS-susceptible japonica cultivars.

Cannabis Synthetic Seeds: An Alternative Approach for Commercial Scale of Clonal Propagation and Germplasm Conservation

Indoor cannabis (Cannabis sativa) cultivation has been rapidly increasing in many countries after legalization. Besides conventional propagation through cuttings, synthetic seed production provides a competent system for mass propagation, germplasm conservation and international exchange of genetic materials. The present study developed a reliable protocol for cannabis synthetic seed production using encapsulation of nodal segments derived from in vitro or in vivo sources. Synthetic seeds were produced in 3% sodium alginate and 75 mM calcium chloride in Murashige and Skoog (MS) medium and stored under various environmental conditions for up to 150 days. The plantlets regrowth efficiency was monitored on culture media up to 30 days after the storage period. Regrowth rates of 70% and 90% were observed in synthetic seeds from in vitro and in vivo-derived sources, respectively, when stored in 6 °C under 50 μmol s-1 m-2 light for 150 days. Furthermore, addition of acetylsalicylic acid (ASA) to the encapsulation matrix not only postponed precocious germination of synthetic seeds at 22 °C, but also improved the regrowth rate of in vivo-derived synthetic seeds to 100% when they were stored in 6 °C under light. Exposure to light during storage significantly increased shoot length of regrown synseeds when compared to those stored in darkness. This difference in shoot growth disappeared when synseeds were treated with 25 µM ASA. All regenerated plantlets were rooted and acclimatized in sterile rockwool plugs without morphological changes.

Seed dormancy 4 like1 of Arabidopsis is a key regulator of phase transition from embryo to vegetative development.

Seed dormancy is an adaptive trait that enables plants to survive adverse conditions and restart growth in a season and location suitable for vegetative and reproductive growth. Control of seed dormancy is also important for crop production and food quality because it can help induce uniform germination and prevent preharvest sprouting. Rice preharvest sprouting quantitative trait locus analysis has identified Seed dormancy 4 (Sdr4) as a positive regulator of dormancy development. Here, we analyzed the loss-of-function mutant of the Arabidopsis ortholog, Sdr4 Like1 (SFL1), and found that the sfl1-1 seeds showed precocious germination at the mid- to late-maturation stage similar to rice sdr4 mutant, but converted to become more dormant than the wild type during maturation drying. Coordinated with the dormancy levels, expression levels of the seed maturation and dormancy master regulator genes, ABI3, FUS3, and DOG1 in sfl1-1 seeds were lower than in wild type at early- and mid-maturation stages, but higher at the late-maturation stage. In addition to the seed dormancy phenotype, sfl1-1 seedlings showed a growth arrest phenotype and heterochronic expression of LAFL (LEC1, ABI3, FUS3, LEC2) and DOG1 in the seedlings. These data suggest that SFL1 is a positive regulator of initiation and termination of the seed dormancy program. We also found genetic interaction between SFL1 and the SFL2, SFL3, and SFL4 paralogs of SFL1, which impacts on the timing of the phase transition from embryo maturation to seedling growth.

Disruption of the mce operon from Streptomyces affects spore resistance and results in precocious germination

Streptomyces coelicoloris a non-pathogenic soil saprophytic bacterium and is a model organism for antibiotic production. This species contains a single copy of a nine gene cluster known as the mammalian cell entry (mce) operon. This operon was originally characterised in Mycobacterium tuberculosisas an important virulence factor acting in invasion and survival within macrophages and encodes an ABC transporter for cholesterol import. As the function of the mceoperon in S. coelicoloris currently unknown, this study aims to characterise the operon through deletion of the mcelocus and resulting impact on bacterial morphology and survival. SEM images demonstrate that spores of a mcedeletion mutant (Δmce) display a wrinkled, and ‘fragile’ phenotype, with spores appearing to germinate whilst on the spore chain. Germination assays show that spores of Δmcegerminate earlier than WT S. coelicolor, and impression mounts indicate spore chains emerge earlier in the Δmcestrain. As spores of Δmce possess an altered spore coat, it was hypothesised they might show reduced resistance to stressors. Heat kill assays show that deletion of the mce operon results in S. coelicolor spores which are less tolerant to temperatures of 60, 70, 80, 90 and 100°C compared to WT S. coelicolor spores. Heat activation of Δmce spores was also consistently absent at all temperatures tested. Spores of the Δmcestrain are also less resistant to triclosan, and sulfobetaines. Preliminary results indicate that the mce operon of S. coelicolor may be a cholesterol importer, as Δmce shows reduced growth in the presence of cholesterol, compared to WT S. coelicolor.

Existence of Vivipary in Mango (Mangifera indica cv. ‘Amrapali’) – A Report

Aim: The Amrapalii cultivar of mango is known for its dwarf stature, high productivity and ability to capture the market late when mango from other regions of the country gets over. Vivipary is of unusual occurrence in mango. The aim of the study is to report the occurrence of vivipary in mango especially in cultivar Amrapali under the sub-Himalayan subtropics of India.
 Materials and Methods: Incidental occurrence of vivipary in mango has been reported from the Hamirpur district of Himachal Pradesh during the growing season of the year 2021. Upon observance of abnormal protuberances from the fruit surface, the harvesting was commenced at the weekly intervals and the per cent proportion of viviparous fruits was ascertained by cutting the fruits longitudinally and confirming the viviparous germination of the seeds. Weather data of the fruit development state were analysed for the accumulation of heat units and rainfall distribution. Efforts have been made for ascertaining the reason behind the viviparous seed development.
 Results and Discussion: The proportion of viviparous seeds increased with the progression of time and by the mid of September, more than 12% of seeds were found viviparous. The weather data show that there was an early accumulation of heat units. Also, the rainfall during the period of fruit development was high particularly at the time when fruits were advancing toward maturity.
 It has been observed that the seed maturity has preceded the fruit pulp maturity and ripening may be due to the early accumulation of heat units and high rainfall. This coincidence might have resulted in precocious germination of seed inside the fruit, leading to vivipary.
 Conclusion: The development of vivipary in Amrapali mango has been found to be associated with the early accumulation of heat units and high rainfall. Under the current changing climatic scenario, a need has been projected for strategic research for curtailing vivipary incidences and saving economic losses to the growers of late mango varieties in the sub-Himalayan subtropics.

Precocious germination of a pine cone in Eocene Baltic amber

ABSTRACT Seed germination is a crucial stage in the development of all plants. It normally occurs in the soil after the seed has fallen from the mother plant. In some infrequent instances, precocious germination (a type of viviparity or vivipary) occurs when the seed sprouts while still within the fruit. The present paper describes the first case of precocious germination of a fossil plant involving a number of seeds that have germinated in a pine cone embedded in Eocene Baltic amber. At the tips of the emerging hypocotyls are clusters of needles in fascicles of 5, associating the fossil with the extinct pine species Pinus cembrifolia Caspary described earlier from Baltic amber. Environmental implications of this discovery are discussed.

The Arabidopsis AGC kinases NDR2/4/5 interact with MOB1A/1B and play important roles in pollen development and germination.

Pollen formation and pollen tube growth are essential for the delivery of male gametes into the female embryo sac for double fertilization. Little is known about the mechanisms that regulate the late developmental process of pollen formation and pollen germination. In this study, we characterized a group of Arabidopsis AGC kinase proteins, NDR2/4/5, involved in pollen development and pollen germination. The NDR2/4/5 genes are mainly expressed in pollen grains at the late developmental stages and in pollen tubes. They function redundantly in pollen formation and pollen germination. At the tricellular stages, the ndr2 ndr4 ndr5 mutant pollen grains exhibit an abnormal accumulation of callose, precocious germination and burst in anthers, leading to a drastic reduction in fertilization and a reduced seed set. NDR2/4/5 proteins can interact with another group of proteins (MOB1A/1B) homologous to the MOB proteins from the Hippo signaling pathway in yeast and animals. The Arabidopsis mob1a mob1b mutant pollen grains also have a phenotype similar to that of ndr2 ndr4 ndr5 pollen grains. These results provide new evidence demonstrating that the Hippo signaling components are conserved in plants and play important roles in sexual plant reproduction.

Changes in abscisic acid metabolism in relation to the maturation of grapevine (Vitis vinifera L., cv. Menc\xeda) somatic embryos

BackgroundSomatic embryogenesis in grapevines is a complex process that depends on many physiological and genetic factors. One of its main limitations is the process of precocious germination of the somatic embryos in differentiation medium. This process lowers plant conversion rates from the somatic embryos, and it is probably caused by a low endogenous abscisic acid (ABA) content.ResultsPrecocious germination of the somatic embryos was successfully avoided by culturing grapevine cv. Mencía embryogenic aggregates over a semipermeable membrane extended on top of the differentiation medium. The weekly analysis of the endogenous ABA and ABA-glucosyl ester (ABA-GE) contents in the aggregates showed their rapid accumulation. The expression profiles of 9-cis-epoxycarotenoid dioxygenase (VvNCED1), 8′-hydroxylase (VvHyd2), UDP-glucosyltransferase (VvUGT) and β-glucosidase (VvBG2) genes in grapevine revealed that the occurrence of a first accumulation peak of endogenous ABA in the second week of culture over the semipermeable membrane was mainly dependent on the expression of the VvNCED1 gene. A second increase in the endogenous ABA content was observed in the fourth week of culture. At this point in the culture, our results suggest that of those genes involved in ABA accumulation, one (VvNCED1) was repressed, while another (VvBG2) was activated. Similarly, of those genes related to a reduction in ABA levels, one (VvUGT) was repressed while another (VvHyd2) was activated. The relative expression level of the VvNCED1 gene in embryogenic aggregates cultured under the same conditions and treated with exogenous ABA revealed the significant downregulation of this gene.ConclusionsOur results demonstrated the involvement of ABA metabolism in the control of the maturation of grapevine somatic embryos cultured over a semipermeable membrane and two important control points for their endogenous ABA levels. Thus, subtle differences in the expression of the antagonistic genes that control ABA synthesis and degradation could be responsible for the final level of ABA during the maturation of grapevine somatic embryos in vitro. In addition, the treatment of somatic embryos with exogenous ABA suggested the feedback-based control of the expression of the VvNCED1 gene by ABA during the maturation of grapevine somatic embryos.

The aquatic carnivorous plant Aldrovanda vesiculosa (Droseraceae) exhibits altered developmental stages in male gametophyte.

Aldrovanda vesiculosa (Droseraceae) is a rare aquatic carnivorous plant, distributed in Europe, Asia, Africa, and Australia. Aldrovanda populations can flower prolifically under favourable conditions, but seed set is very limited. We studied the structure of Aldrovanda pollen collected from flowers in different developmental stages (opened and non-opened anthers) from both European and Australian populations to elucidate pollination traits and the basis of poor seed set on the basis of microscopic observation of pollen and anther structure. Microscopic analyses of Aldrovanda pollen showed that this plant has pollen arranged in tetrads like other species in the Droseraceae family. In hydrated pollen, cytoplasmic protrusions originate from pores located along the equatorial wall of monads, and can develop into pollen tubes. Interestingly, pollen development from microspores occurs in open anthers, suggesting a delay of the developmental stages. In addition, pollen development displays altered sperm cell formation and precocious pollen germination. Precocious germination may characterize recalcitrant pollen, which naturally do not undergo dehydration before anthesis and remain partially hydrated, particularly in aquatic and wetland plants. These alterations of male gametophyte development could affect fertilization processes, and be the reason for the low reproductive capability of Aldrovanda observed both in the field and in cultures. Generally, reduced pollen longevity and very quick germination are considered an adaptation to aquatic or wet environments.

Germination responses to winter warm spells and warming vary widely among woody plants in a temperate forest.

Winter underpins key ecological processes, such as dormancy loss and seedling emergence. Enhanced warm spells, together with warming are occurring and will continue in the future. The consequences of these climate phenomena on germination were investigated among co-occurring woody plants, whose seeds are bird-dispersed in autumn and require cold stratification for spring emergence. Seeds from nine common southeastern USA plants were collected in autumn. We verified that seeds of the study species required cold stratification for dormancy loss. We then examined the following aspects in the laboratory or field: effect of warm spells during cold stratification on germination, effect of a warm spell during winter on seed survival and germination phenology, and effect of warming from autumn dispersal through winter dormancy loss on timing of germination. While no consistent effects of warm spells were found in the laboratory on quantity of germination, warm spells advanced spring field germination for several species. Some species germinated during cold stratification and during warm spells, especially extreme spells, in the laboratory. In the field, about half of Lonicera maackii seedlings that emerged with a warm spell died by late winter. With warming from autumn through spring, laboratory germination shifted from spring to predominately autumn for some species. With precocious germination during warm spells or germination phenology shifts, two scenarios are possible. Seedlings may die during winter, reducing the size of the soil seed bank and number of emergents, or they would survive in warmer winters, which would give them a competitive advantage over spring-emerging seedlings.

Floral Biology of Mitreola petiolata and M. sessilifolia (Loganiaceae): Chasmogamous Flowers with Massive Post-Anthesis Precocious Pollen Germination

Mitreola petiolata and M. sessilifolia in the Loganiaceae are similar wetland annuals occurring in tropical, subtropical, and temperate regions in the southeastern U.S., Africa, Asia, and Oceania. The flowers of both species have previously been described to open briefly with an apparent window for outside pollination, followed by flower closure and massive pollen germination within the anthers with pollen tubes covering the adjacent stigma. The phenomenon was documented with field observations, floral dissections, and light and scanning electron microscopy. Both species open their flowers for a brief 6–8 hour window. Subsequently, pollen germinates within the closed or closing flower with pollen tubes completely covering the stigma. The prevalence and importance of selfing by precocious pollen germination are discussed.

Incidence of In Situ Pollen Germination in Three Species of Viola L. of Uttarakhand

We studied in situ pollen germination in natural populations of Viola canescens Wall., V. biflora L. and V. patrinii Ging., where a part of pollen grains shows a precocious germination while in the anther. In situ germinated pollen tube showed some abnormality in structure that may be due to non-availability of microenvironment. Rest of pollens exhibits the normal dispersal after anther dehiscence and germination on compatible stigma. This phenomenon may contribute to the reproductive efficiency.

Expression Patterns of Key Hormones Related to Pea (Pisum sativum L.) Embryo Physiological Maturity Shift in Response to Accelerated Growth Conditions.

Protocols have been proposed for rapid generation turnover of temperate legumes under conditions optimized for day-length, temperature, and light spectra. These conditions act to compress time to flowering and seed development across genotypes. In pea, we have previously demonstrated that embryos do not efficiently germinate without exogenous hormones until physiological maturity is reached at 18 days after pollination (DAP). Sugar metabolism and moisture content have been implicated in the modulation of embryo maturity. However, the role of hormones in regulating seed development is poorly described in legumes. To address this gap, we characterized hormonal profiles (IAA, chlorinated auxin [4-Cl-IAA], GA20, GA1, and abscisic acid [ABA]) of developing seeds (10–22 DAP) from diverse pea genotypes grown under intensive conditions optimized for rapid generation turnover and compared them to profiles of equivalent samples from glasshouse conditions. Growing plants under intensive conditions altered the seed hormone content by advancing the auxin, gibberellins (GAs) and ABA profiles by 4 to 8 days, compared with the glasshouse control. Additionally, we observed a synchronization of the auxin profiles across genotypes. Under intensive conditions, auxin peaks were observed at 10 to 12 DAP and GA20 peaks at 10 to 16 DAP, indicative of the end of embryo morphogenesis and initiation of seed desiccation. GA1 was detected only in seeds harvested in the glasshouse. These results were associated with an acceleration of embryo physiological maturity by up to 4 days in the intensive environment. We propose auxin and GA profiles as reliable indicators of seed maturation. The biological relevance of these hormonal fluctuations to the attainment of physiological maturity, in particular the role of ABA and GA, was investigated through the study of precocious in vitro germination of seeds 12 to 22 DAP, with and without exogenous hormones. The extent of sensitivity of developing seeds to exogenous ABA was strongly genotype-dependent. Concentrations between 5 and 10 µM inhibited germination of seeds 18 DAP. Germination of seeds 12 DAP was enhanced 2.5- to 3-fold with the addition of 125 µM GA3. This study provides further insights into the hormonal regulation of seed development and in vitro precocious germination in legumes and contributes to the design of efficient and reproducible biotechnological tools for rapid genetic gain.

Disruption of the mce operon from Streptomyces affects spore resistance and results in precocious germination

Streptomyces coelicolor is a non-pathogenic soil saprophytic bacterium and is a model organism for antibiotic production. This species contains a single copy of a nine gene cluster known as the mammalian cell entry (mce) operon. This operon was originally characterised in Mycobacterium tuberculosis as an important virulence factor acting in invasion and survival within macrophages and encodes an ABC transporter for cholesterol import. As the function of the mceoperon in S. coelicoloris currently unknown, this study aims to characterise the operon through deletion of the mcelocus and resulting impact on bacterial morphology and survival. SEM images demonstrate that spores of a mcedeletion mutant (Δmce) display a wrinkled, and ‘fragile’ phenotype, with spores appearing to germinate whilst on the spore chain. Heat kill assays show that the deletion of the mce operon result in S. coelicolor spores which are less tolerant to temperatures of 60, 70, 80, 90 and 100°C compared to WT S. coelicolor spores. Heat activation of Δmce spores was also consistently absent at all temperatures tested. The spores of a Δmce mutant also exhibit a precocious germination phenotype seen on SEM images confirmed with germination assays.

Basalt Milkvetch Responses to Novel Restoration Treatments in the Great Basin

The restoration of native forbs in the Great Basin and similar dryland ecosystems remains a great challenge for land managers. Variable soil water, precocious germination and emergence, and the presence of soil fungal pathogens often reduce plant establishment. Novel restoration treatments that increase soil water during early forb life stages, delay germination and emergence to coincide with favorable spring conditions, and reduce mortality from soil fungal pathogens may benefit native forb restoration. We compared the efficacy of three novel treatments—snow fencing, plant protection fabric, and seed coatings—to improve establishment of a forb species native to the Great Basin, basalt milkvetch (Astragalus filipes Torr. ex A. Gray). We replicated treatments plus a no-treatment control at three sites in the Great Basin in a randomized complete block design over 2 yr. To evaluate the efficacy of our restoration treatments, we measured germination, seedling emergence, establishment, and second-yr survival. The effects of snow fencing and plant protection fabric varied by site and life stage and were likely influenced by the wet spring conditions across sites, particularly the two northern sites. Snow fencing increased establishment and second-yr survival at one site. Plant protection fabric did not benefit any life stage at any site. Seed coatings increased seedling emergence at all sites but did not affect establishment or survival. Overall, second-yr survival remained low across all sites and treatments. Our study indicates that our treatments can positively affect basalt milkvetch emergence, establishment, and survival, but additional management actions are needed to improve long-term restoration success of native forbs.