Single Seeds Research Articles

Development and characterization of an EMS-mutagenized wheat population and identification of salt-tolerant wheat lines

BackgroundTriticum aestivum (wheat) is one of the world’s oldest crops and has been used for >8000 years as a food crop in North Africa, West Asia and Europe. Today, wheat is one of the most important sources of grain for humans, and is cultivated on greater areas of land than any other crop. As the human population increases and soil salinity becomes more prevalent, there is increased pressure on wheat breeders to develop salt-tolerant varieties in order to meet growing demands for yield and grain quality. Here we developed a mutant wheat population using the moderately salt-tolerant Bangladeshi variety BARI Gom-25, with the primary goal of further increasing salt tolerance.ResultsAfter titrating the optimal ethyl methanesulfonate (EMS) concentration, ca 30,000 seeds were treated with 1% EMS, and 1676 lines, all originating from single seeds, survived through the first four generations. Most mutagenized lines showed a similar phenotype to BARI Gom-25, although visual differences such as dwarfing, giant plants, early and late flowering and altered leaf morphology were seen in some lines. By developing an assay for salt tolerance, and by screening the mutagenized population, we identified 70 lines exhibiting increased salt tolerance. The selected lines typically showed a 70% germination rate on filter paper soaked in 200 mM NaCl, compared to 0–30% for BARI Gom-25. From two of the salt-tolerant OlsAro lines (OA42 and OA70), genomic DNA was sequenced to 15x times coverage. A comparative analysis against the BARI Gom-25 genomic sequence identified a total of 683,201 (OA42), and 768,954 (OA70) SNPs distributed throughout the three sub-genomes (A, B and D). The mutation frequency was determined to be approximately one per 20,000 bp. All the 70 selected salt-tolerant lines were tested for root growth in the laboratory, and under saline field conditions in Bangladesh. The results showed that all the lines selected for tolerance showed a better salt tolerance phenotype than both BARI Gom-25 and other local wheat varieties tested.ConclusionThe mutant wheat population developed here will be a valuable resource in the development of novel salt-tolerant varieties for the benefit of saline farming.

Determination of Moisture Content of Single Maize Seed by Using Long-Wave Near-Infrared Hyperspectral Imaging (LWNIR) Coupled With UVE-SPA Combination Variable Selection Method

Moisture content (MC) is one of the important factors to assess the quality of maize seeds. In this study, the feasibility of using long-wave near infrared (LWNIR) hyperspectral imaging (HSI) technique with the spectral range of 930-2548 nm for predicting MC of single maize seeds was observed. The averaged spectra extracted from whole and centroid regions in the embryo side of single maize seeds were pretreated by Savizky-Golay smoothing and first derivative (SG-D1). A combination of uninformative variable elimination (UVE) and successive projections algorithm (SPA) was proposed to select feature wavelengths (variables) from LWNIR hyperspectral data. The quantitative relationship between feature wavelengths and MC was established by partial least square (PLSR) and least square-support vector machine (LS-SVM), respectively. Results illustrated that the UVE-SPA-LS-SVM model established based on spectra of centroid region obtained the best performance for MC detection of the single maize seeds. The correlation coefficient of prediction (Rpre) and root mean square error of prediction (RMSEP) were 0.9325 and 1.2109, respectively. Finally, MC distribution of single maize seed was visualized by pseudo-color map. This study showed LWNIR HSI technique was feasible to measure MC of single maize seeds and a robust and accurate model could be established based on UVE-SPA-LS-SVM method with the spectra of centroid regions.

Genetic Variation in Growth and Cone Traits of Pinus Koraiensis Half-Sib Families in Northeast China

Genetic parameters were evaluated for growth and cone characteristics (tree height, diameter at breast height, volume, cone number, thousand seeds weight and single cone seeds weight) on 86 half-sib families of Pinus koraiensis aged 31 years. Analyses of variance revealed significant differences (p < 0.001) in all growth and cone traits among families while no significant differences were detected among blocks and the interaction between blocks and families. The average family values for growth traits were 17.22 m, 8.67 cm and 0.43 m3 for tree height, diameter at breast height and volume, respectively. The average cone number, thousand seeds weight and single cone seeds weight were 17.57, 748.91 g and 77.25 g, respectively. Genotypic additive variance and phenotypic variances ranged from 0.00009 to 3.820 and from 0.0005 to 23.066, while genotypic and phenotypic coefficients of variation ranged from 2.693% to 37.196% and 4.963% to 60.595%, respectively. Heritability at the individual and family level ranged from 0.152 to 0.215 and 0.611 to 0.862, respectively. Growth traits were significantly positively correlated with each other, but cone traits showed a weak correlation with growth traits. Based on 10% selection rate, nine families each were selected as elite materials in terms of high performance in volume and cone numbers, with 22.16% and 43.82% genetic gain in volume and cone number, respectively. These results provide beneficial information to select excellent families and establish orchards of P. koraiensis from improved seeds.

Effects of Different Treatments on Seed Germination and Improvement of &amp;lt;i&amp;gt;Vitellaria paradoxa&amp;lt;/i&amp;gt;

Shea butter (Vitellaria paradoxa) tree is one of the most important tree species in Africa owing to its high potential in reduction of poverty and hunger in rural areas and enhancing environmental sustainability. All parts of shea tree are important from bark to wood and from leaves to fruits. Despite all the uses and many more, shea is amongst the endangered species of trees because of over-utilization, low regeneration abilities and lack of efficient propagation methods. Consequently, this research seeks to determine the most efficient methods for propagating V. paradoxa. The experiment consists of three stages. In the first stage, complete fruits were planted without depulping; in the second experiment, the seeds were exposed to single seed treatments that were applied to the seeds and in the third experiment, the seeds were exposed to double seed treatments. It was observed that intact fruits did not germinate while the results showed the single seeds treatment to significantly have affected germination performance. De-shelled seeds germinated faster (43 days) than all other treatments but 48 hours soaking produced the highest germination percentage (91.7%). An even better result was recorded with double seeds treatments in which de-shelled plus 24 hours soaked seed germinated faster (39.3 days) than other treatments while sandpapered plus 24 hours soaked seeds had the best germination percentage (75%). Therefore, scarification using sandpaper plus soaking for 24 hours was identified as the best treatment for breaking seed dormancy in V. paradoxa.

The Role of Gas Fragmentation During the Formation of Supermassive Black Holes

Abstract We perform cosmological hydrodynamic simulations to study the effect of gas fragmentation on the formation of supermassive black hole seeds in the context of Direct Collapse. Our setup considers different UV background intensities, host halo spins, and halo merger histories. We observe that our low-spin halos are consistent with the Direct Collapse model when they are irradiated by a UV background of J 21 = 10,000. In these cases, a single massive object ∼105 M ⊙ is formed in the center of the halo. On the other hand, in our simulations irradiated by a UV background of J 21 = 10, we see fragmentation and the formation of various less massive seeds. These fragments have masses of 103–104 M ⊙. These values are still significant if we consider the potential mergers between them and the fact that these minor objects are formed earlier in cosmic time compared to the massive single seeds. Moreover, in one of our simulations, we observe gas fragmentation even in the presence of a strong UV intensity. This structure arises in a dark matter halo that forms after various merger episodes, becoming the structure with the highest spin value. The final black hole seed mass is ∼105 M ⊙ for this run. From these results, we conclude that fragmentation produces less massive objects; however, they are still prone to merge. In simulations that form many fragments, they all approach the most massive one as the simulations evolve. We see no uniqueness in the strength of the UV intensity value required to form a DCBH since it depends on other factors like the system dynamics in our cases.

VIS-NIR wave spectrometric features of acorns (Quercus robur L.) for machine grading

The study is intended for engineers and small-scale forestry owners because it offers a simple solution for acorns quality improvement by machine grading before sowing. Visible diffuse reflectance spectra of single whole acorns (Quercus robur L.), damaged acorns, acorns pericarp, whole and damaged acorn seeds were scanned with spectrometer USB 4000 (Ocean Optics Inc., USA) from 450 to 900 nm at 1 nm intervals. Near infrared reflectance spectra of single acorns material were scanned with spectrometer NirQuest512 (Ocean Optics Inc., USA) from 900 to 2100 nm at 1 nm intervals. English oak acorns cannot be divided from damaged acorns and acorns pericarp in the visible wavelength range. Hard-to-release damaged acorns with shell cracks are eliminated in the NIR-reflectance at a wavelength range from 1400 to 1500 nm or from 1900 to 2000 nm. After the elimination of damaged acorns, good whole acorns can be grading from the acorns rotten seed and acorns pericarp (only one the inner side of a shell) at a wavelength range from 1600 to 1700 nm. The results of this study are limited to these specific samples and cannot be interpreted for acorns of all Quercus species.

Rapid and non-destructive evaluation of seed quality of Chinese fir by near infrared spectroscopy and multivariate discriminant analysis

Chinese fir (Cunninghamia lanceolata (Lamb) Hook) is a promising timber species for planting in the sub-tropical ecosystem. However, the germination rate of Chinese fir seed lots is low, and viability determination by conventional methods (germination test and tetrazolium test) is time-consuming and destructive. Therefore, the aim of this study was to investigate the potential of Near Infrared (NIR) spectroscopy for rapidly and non-destructively determining viability of Chinese fir seeds. A total of 450 seeds was first identified as viable, empty, or dead (n = 150 seeds per seed lot fraction) by digital X-ray and their viability was further confirmed by germination test. NIR reflectance spectra were collected from single seeds using XDS Rapid Content Analyzer from 780 to 2500 nm. Classification models were developed on calibration set (n = 300 seeds) by Orthogonal Projection to Latent Structures-Discriminant Analysis (OPLS-DA) using the entire or selected NIR regions, and the fitted models were validated using external test set (n = 150 seeds). The model’s ability to recognize members (sensitivity) while rejecting non-members (specificity) of a given class was 100% for viable and dead seeds and 98% for empty seeds, attesting to the model’s robustness. When the model was fitted in the shorter NIR region (780–1100 nm), the sensitivity and specificity reached 100% for all seed lot fractions. The mean classification accuracy was 99% in the full and longer NIR regions and 100% in the shorter NIR region. The spectral differences among seed lot fractions could be attributed to differences in seed coat chemical composition in empty and dead seeds, presumably tannin content, and major storage reserves in viable seeds, notably fatty acids, proteins, and carbohydrate. It can be concluded that NIR spectroscopy has a great potential to evaluate Chinese fir seed quality, which could be applied in the development of an on-line sorting system.

Methodology: ssb-MASS: a single seed-based sampling strategy for marker-assisted selection in rice

BackgroundIntegrated breeding approaches such as combining marker-assisted selection and rapid line fixation through single-seed-descent, can effectively increase the frequency of desirable alleles in a breeding program and increase the rate of genetic gain for quantitative traits by shortening the breeding cycle. However, with most genotyping being outsourced to 3rd party service providers’ nowadays, sampling has become the bottleneck for many breeding programs. While seed-chipping as prevailed as an automatable seed sampling protocol in many species, the symmetry of rice seeds makes this solution as laborious and costly as sampling leaf tissue. The aim of this study is to develop, validate and deploy a single seed sampling strategy for marker-assisted selection of fixed lines in rice that is more efficient, cost-effective and convenient compared to leaf-based sampling protocols without compromising the accuracy of the marker-assisted selection results.ResultsEvaluations replicated across accessions and markers showed that a single rice seed is sufficient to generate enough DNA (7–8 ng/μL) to run at least ten PCR trait-markers suitable for marker-assisted selection strategies in rice. The DNA quantity and quality extracted from single seeds from fixed lines (F6) with different physical and/or chemical properties were not significantly different. Nor were there significant differences between single seeds collected 15 days after panicle initiation compared to those harvested at maturity. A large-scale comparison between single seed and leaf-based methodologies showed not only high levels of genotypic concordance between both protocols (~ 99%) but also higher SNP call rates in single seed (99.24% vs. 97.5% in leaf). A cost–benefit analysis showed that this single seed sampling strategy decreased the cost of sampling fourfold. An advantage of this approach is that desirable genotypes can be selected before investing in planting activities reducing the cost associated with field operations.ConclusionThis study reports the development of a cost-effective and simple single seed genotyping strategy that facilitates the adoption and deployment of marker-assisted selection strategies in rice. This will allow breeders to increase the frequency of favorable alleles and combine rapid generation advancement techniques much more cost-effectively accelerating the process and efficiency of parental selection and varietal development.

Effect of Composition on the Growth of Single Crystals of (1-x)(Na1/2Bi1/2)TiO3-xSrTiO3 by Solid State Crystal Growth.

The (1−x)(Na1/2Bi1/2)TiO3-xSrTiO3 (NBT-100xST) system is a possible lead-free candidate for actuator applications because of its excellent strain vs. electric field behaviour. Use of single crystals instead of polycrystalline ceramics may lead to further improvement in piezoelectric properties but work on single crystal growth in this system is limited. In particular, the effect of composition on single crystal growth has yet to be studied. In this work, single crystals of (NBT-100xST) with x = 0.00, 0.05, 0.10 and 0.20 were grown using the method of Solid State Crystal Growth. [001]-oriented SrTiO3 single crystal seeds were embedded in (NBT-100xST) ceramic powder, which was then pressed to form pellets and sintered at 1200 °C for 5 min–50 h. Single crystal growth rate, matrix grain growth rate and sample microstructure were examined using scanning and transmission electron microscopy. The results indicate that the highest single crystal growth rate was obtained at x = 0.20. The mixed control theory of grain growth is used to explain the single crystal and matrix grain growth behaviour.

Genome-Wide Association Study Reveals Candidate Genes for Flowering Time Variation in Common Bean (Phaseolus vulgaris L.).

The common bean is one of the most important staples in many areas of the world. Extensive phenotypic and genetic characterization of unexplored bean germplasm are still needed to unlock the breeding potential of this crop. Dissecting genetic control of flowering time is of pivotal importance to foster common bean breeding and to develop new varieties able to adapt to changing climatic conditions. Indeed, flowering time strongly affects yield and plant adaptation ability. The aim of this study was to investigate the genetic control of days to flowering using a whole genome association approach on a panel of 192 highly homozygous common bean genotypes purposely developed from landraces using Single Seed Descent. The phenotypic characterization was carried out at two experimental sites throughout two growing seasons, using a randomized partially replicated experimental design. The same plant material was genotyped using double digest Restriction-site Associated DNA sequencing producing, after a strict quality control, a dataset of about 50 k Single Nucleotide Polymorphisms (SNPs). The Genome-Wide Association Study revealed significant and meaningful associations between days to flowering and several SNP markers; seven genes are proposed as the best candidates to explain the detected associations.

Phylogenetic and population structural inference from genomic ancestry maintained in present-day common wheat Chinese landraces.

Hexaploid common wheat is one of the most important food crops worldwide. Common wheat domestication began in the Fertile Crescent of the Near East approximately 10000years ago and then spread west into Europe and eastward into East Asia and China. However, the possible spreading route into and within China is still unclear. In this study, we successfully extracted DNA from single ancient wheat seeds and sequenced the whole genome of seven ancient samples from Xiaohe and Gumugou cemeteries in Xinjiang, China. Genomic inference and morphological observation confirmed their identity as hexaploid common wheat grown in prehistoric China at least 3200years before present (BP). Phylogenetic and admixture analyses with RNA-seq data of modern hexaploid wheat cultivars from both China and Western countries demonstrated a close kinship of the ancient wheat to extant common wheat landraces in southwestern China. The highly similar allelic frequencies in modern landraces of the Qinghai-Tibetan plateau with the ancient wheat support the previously suggested southwestern spreading route into highland China. A subsequent dispersal route from the Qinghai-Tibetan plateau margins to the Yangtze valley was proposed in this study. Furthermore, the common wheat populations grown in the Middle and Lower Yangtze valley wheat zones were also proposed to be established by population admixture with the wheat grown in the Upper Yangtze valley. Our study reports ancient common wheat sequences at a genome-wide scale, providing important information on the origin, dispersal, and genetic improvement under cultivation of present-day wheat landraces grown in China.

Epistatic gene control on the yield of tomato at medium elevation in the tropical agroecosystem

Abstract. Mawasid FP, Syukur M, Trikoesoemaningtyas. 2019. Epistatic gene control on the yield of tomato at medium elevation in the tropical agroecosystem. Biodiversitas 20: 1880-1886. Cultivation of tomatoes on the middle-low plain generally decreases the quantity and quality of the yield due to high-temperature stress. Increasing the size and weight of lowland tomatoes is needed to enhance national production. Information on the action and genetic model of target characters is needed in the preparation of the assembly program, especially for selection needs. This study aims to obtain genetic information and heritability of tomato yield characters, as a basis for assembling large tomato varieties for the lowlands. The study was conducted using six populations (P1, P2, F1, BCP1, BCP2, and F2) resulting from two different crosses of 99D x Tora (C-I) and 97D x Tora (C-II). The results show that the action of non-additive genes and non-allelic interactions has a large value, with duplicate epistasis being more dominant than complementary epistasis. Duplicate epistasis was found in the character of harvest time, fruit length, fruit diameter, fruit weight in cross I and flowering time, harvest time, fruit length, fruit diameter, and number of fruits in cross II, while complementary epistasis was found in flowering time, fruit weight per plant, number of fruits in cross I, and fruit weight, fruit weight per plant in cross II. Moderate to high heritability was found in the character of fruit length, fruit diameter, fruit weight, and fruit weight per plant. The values are higher in population from the cross I (99D x Tora) for each character, indicating that the cross I has a higher potential for genetic progress than cross II. Selection is recommended when the homozygosity has increased, using the Bulk method or Single Seed Decent. The two methods above can maintain variability in the next generation, so epistasis genes that control target characters are not drastically eliminated.

Are all patches worth exploring? Foraging desert birds do not rely on environmental indicators of seed abundance at small scales

BackgroundConsumers should show strong spatial preferences when foraging in environments where food availability is highly heterogeneous and predictable. Postdispersal granivores face this scenario in most arid areas, where soil seed bank abundance and composition associates persistently with vegetation structure at small scales (decimetres to metres). Those environmental features should be exploited as useful pre-harvest information, at least to avoid patches predicted to be poor. However, we did not find the expected spatial association in the algarrobal of the central Monte desert by observing foraging seed-eating birds, a field technique influenced by how much they exploit visited patches. In this work we tested if the first stage of foraging by granivorous birds (patch visit, encounter or exploration) is positively associated with environmental indicators of patch quality by recording the removal of single seeds from 300 scattered experimental devices during seasonal trials. Spatial selectivity was analysed by comparing the structural characteristics of used vs. available microhabitats, and evaluated against bottom-up and top-down hypotheses based on our previous knowledge on local seed bank abundance, composition and dynamics. Their foraging activity was also explored for spatial autocorrelation and environmental correlates at bigger scales.ResultsPostdispersal granivorous birds were less selective in their use of foraging space than expected if microhabitat appearance were providing them relevant information to guide their search for profitable foraging patches. No microhabitat type, as defined by their vegetation structure and soil cover, remained safe from bird exploration. Analyses at bigger temporal and spatial scales proved more important to describe heterogeneity in seed removal.ConclusionsCloseness to tall trees, probably related to bird territoriality and reproduction or to their perception of predation risk, seemed to determine a first level of habitat selection, constraining explorable space. Then, microhabitat openness (rather than seed abundance) exerted some positive influence on which patches were more frequently visited among those accessible. Selective patterns by birds at small scales were closer to our predictions of a top-down spatial effect, with seed consumption creating or strengthening (and not responding to) the spatial pattern and dynamics of the seed bank.

Multivariate Discriminant Analysis of Single Seed Near Infrared Spectra for Sorting Dead-Filled and Viable Seeds of Three Pine Species: Does One Model Fit All Species?

Seed lots of pine species are composed of viable, dead-filled and empty seeds, and the success of complete sorting of dead-filled seeds using the conventional method (Incubation, Drying and Separation in water) is difficult to achieve; leaving a considerable scope for upgrading the sorting efficiency. The objective of this study was to evaluate the prospect of sorting viable and dead-filled seeds of pine species using Near Infrared (NIR) spectroscopy. To demonstrate this, dead-filled and viable seeds of Mason’s pine, slash pine and loblolly pine were incubated in moist medium for three days, dried for six hours and scanned by XDS Rapid Content Analyzer from 780–2500 nm. Orthogonal Projection to Latent Structure-Discriminant Analysis was used to develop discriminant models for each species separately and for all species combined. The results showed that the sensitivity (the model’s ability to correctly classify members of a given class) and the specificity (the model’s ability to reject non-members of a given class) were 100% for each species model and 98%–99% for combined species model. The overall classification accuracy was 100% and 99% for individual species and combined species models, respectively. The absorption band in the 1870–1950 nm with a major peak at 1930 nm, which is related to water, was responsible for discrimination as dead-filled seeds dried quicker than viable seeds during the drying process. Our study is the first attempt to simultaneously discriminate dead-filled and viable seeds of pines by NIR spectroscopy. The results demonstrates that a global calibration model of seed lots of several pine species can be equally effective as the individual species model to discriminate viable and dead-filled seeds by NIR spectroscopy, thereby ensuring precision sowing (also known as single seed sowing) in nurseries.

Cotton (Gossypium hirsutum L.) mutants with reduced levels of palmitic acid (C16:0) in seed lipids

The objective of this study was to identify mutants of upland cottonseed (Gossypium hirsutum L.) with reduced levels of palmitic acid (C16:0) in the seed. The five parental populations that had been exposed to Ethyl MethaneSulfonate in 1997 or 2002 were initially screened for either herbicide tolerance or divergent fiber quality. Fatty acid composition were determined for five seed bulks from 140 M5 mutant lines in 2009 and 100 M6 partial seeds in 2010. Mutants with reduced levels of palmitic acid levels were isolated from TAM 94L-25 (PI 631440), Acala 1517-99 (Reg. No. CV-115, PI 612326) and TTU SCM3-7-3 (Reg. No.GS-4, PI 657942). Thirteen M6 single seeds with reduced levels of palmitic acid (17.9–19.6%) were intercrossed in the greenhouse. Ten of the single seed selections were designated as potential male parents and randomly crossed to three potential female parents to generate F1 plants and 21 F2 populations for allele testing. Based on these tests, five F2 populations with reduced levels of low palmitic acid, were selected for further evaluation. The development of mutant lines with reduced levels of palmitic acid in upland cotton was submitted for proprietary protection under U.S. Patent No. 20160222399.

A calibration transfer optimized single kernel near-infrared spectroscopic method.

Single kernel near-infrared spectroscopy (SKNIRS) could aid in the quality screening of early-generation seeds, to improve the efficiency of seed breeding. However, the application of SKNIRS is limited due to the irregular physical characteristics, the heterogeneous constituent distributions of individual seeds, and the insufficient detection accuracy of the reference method. The reported near-infrared detection results of single seeds are often less accurate than those of dehusked seeds and seed flour. In this paper, a calibration transfer-optimized single kernel near-infrared spectroscopic method is proposed. This method aims to accurately detect the chemical composition of single seeds by using the calibration model of the corresponding dehusked seeds or seed flour. The proposed method was applied to the analysis of the protein content of a single rice kernel. The near-infrared transmission spectra of three forms of rice (single rice kernel (SRK), single brown rice kernel (SBK) and rice flour (RF)) of 201 individual rice seeds and the corresponding protein content values were obtained. By comparing different pretreatment methods and spectral ranges, the spectral range 950-1250 nm, the standard normal variate transformation (SNV) pretreatment, and 9 PLS factors were selected to construct the optimal partial least squares (PLS) regression models. Then, the protein content of single rice kernels were determined through two different methods: (i) the direct method, in which single rice kernels were analyzed using the single rice kernel model directly; and (ii) the proposed method, in which the spectra of single rice kernels were transferred into the spectra of single brown rice kernels and rice flours with a calibration transfer algorithm, spectral space transformation (SST), and were analyzed by the respective calibration models. The external validation coefficient correlation (R) value of the direct method was 0.971, and the R values of the proposed method were 0.962 (SBK) and 0.975 (RF). The root mean square error of prediction (RMSEP) value of the direct method was 0.423, and the RMSEP of the proposed method were 0.480 (SBK) and 0.401 (RF). In addition, the transfer results among the spectra of three forms of rice were compared. By comparison, the results of the proposed method are fairly close to the results of the direct method. The results indicate that the spectra generated from one individual rice seed can be transferred freely among the three forms by means of calibration transfer. The proposed method is a promising way to overcome the challenges associated with analyzing individual seeds and to improve SKNIRS.

Using Polyvinylpyrrolidone and Citrate Ions To Modify the Stability of Ag NPs in Ethylene Glycol

Silver nanoparticles (Ag NPs) can serve as seeds in the polyol synthesis of silver nanostructures. However, when heating suspensions of Ag NP seeds up to commonly employed reaction temperatures (e.g., 90 °C or higher for reactions in ethylene glycol), the size distribution of the product Ag NPs can broaden dramatically through a combination of oxidative dissolution, aggregation, and ripening. Results demonstrate that judicious selection of capping agent and pH can protect Ag NP seeds from these reactions, which prevents broadening of the size distribution. Further, polycrystalline seeds can be selectively dissolved, leaving single crystal seeds largely unaltered.

Clark’s Nutcrackers (&lt;i&gt;Nucifraga columbiana&lt;/i&gt;) caching Whitebark Pine (&lt;i&gt;Pinus albicaulis&lt;/i&gt;) seeds in trees

On 17 September 2017, I observed two Clark’s Nutcrackers (Nucifraga columbiana) from 8–10 m distance as they cached seeds in a stand of dead Whitebark Pines (Pinus albicaulis) at 2500 m elevation on Saint Mary Peak in the Bitterroot Mountains of Ravalli County, Montana. Over 5 minutes, the nutcrackers created 14 caches in seven different multi-trunk tree clusters in an area of about 50 m2. All caches appeared to be single Whitebark Pine seeds, positioned 2–5 m (mostly 3–4 m) above ground in dead trees. Of the 14 caches, three were placed under loose pieces of bark on a trunk (one) or large limb (two), and the remaining 11 were in encrustations of American Wolf Lichen (Letharia columbiana) growing on branches of the dead trees. Nutcrackers are known to sometimes cache seeds above ground in trees during the late summer and autumn harvest of pine seeds, but usually not to the exclusion of other microsites. The ground at the Montana site was covered by 7–9 cm of fresh snow that fell the previous day, which may have encouraged the nutcrackers to place all of their seed caches above ground in trees.

Which frugivory‐related traits facilitated historical long‐distance dispersal in the custard apple family (Annonaceae)?

AbstractAimLong‐distance dispersal has contributed to the disjunct biogeographical distribution of rain forest plants—something that has fascinated biogeographers since Humboldt's time. However, the dispersal agent for these tropical plant lineages remains puzzling. Here, we investigate which frugivory‐related traits may have facilitated past intercontinental long‐distance dispersal in the custard apple family (Annonaceae), a major vertebrate‐dispersed tropical plant family. We hypothesize that long‐distance dispersal was associated with the evolution of traits related to dispersal by large‐bodied mammals (e.g., large, dull‐coloured, “megafaunal” fruits) and strong‐flying, ocean‐crossing birds and bats (e.g., dehiscent, moniliform or cauliflorous fruits).LocationGlobal.TaxonAnnonaceae.MethodsWe used a fossil‐calibrated phylogenetic framework to infer the biogeographic history of 234 Annonaceae species (10%, covering nearly all genera) in relation to the evolution of 15 frugivory‐related traits, using maximum likelihood and Bayesian inferences. Furthermore, we used linear and generalized linear models and phylogenetic simulations to test whether ancestral fruit traits during intercontinental dispersal were different from those of other lineages not involved in long‐distance dispersal.ResultsWe inferred the ancestral Annonaceae fruits to be small with a single or few small seeds and a small number of fruitlets. These fruits were most probably apocarpous, indehiscent and/or moniliform (i.e., long beads of fruitlets). Furthermore, most of the long‐distance dispersal events in Annonaceae occurred via the expanded tropical forests in the Early Cenozoic (“geodispersal”), and were significantly associated with large (c. 3 cm long), dull‐coloured fruits and short stipes. Additionally, long‐distance dispersal was also facilitated by dehiscent, moniliform and non‐cauliflorous fruits.Main conclusionsWe suggest that the evolution of frugivory‐related traits associated with dispersal by frugivores that frequently move across large distances and/or barriers, such as large‐bodied mammals and strong‐flying birds, has contributed to the disjunct tropical biogeographical distribution of Annonaceae, and probably of tropical rain forest plants more generally.

ارزیابی تنوعپذیری ژنوتیپهای گندم نان تحت شرایط مختلف رطوبتی با استفاده از روشهای متنوع آماری

از بین تنش‌های محیطی، تنش خشکی مهم‌ترین عامل کاهش تولیدات گیاهان در سراسر جهان است. جهت مطالعه تنوع ژنتیکی و ارتباط بین صفات مختلف با عملکرد دانه در 17 ژنوتیپ (شامل ارقام و لاین‌های مختلف) گندم نان، آزمایشی در قالب طرح بلوک‌های کامل تصادفی با سه تکرار تحت دو شرایط عدم تنش خشکی و شرایط دیم در سال زراعی 90-1389 در مزرعه آموزشی-پژوهشی دانشگاه پیام‌نور اسدآباد اجرا گردید. در این آزمایش صفات عملکرد دانه، تعداد دانه در سنبله، طول سنبله، طول برگ پرچم، عرض برگ پرچم، وزن صد دانه، ارتفاع بوته، محتوی نسبی آب برگ، میزان نسبی آب ازدست‌رفته، درصد سبزینگی برگ (میزان کلروفیل) و مساحت برگ پرچم اندازه‌گیری شدند. نتایج تجزیه واریانس ساده تنوع بالا و معنی‌داری را در هر دو شرایط رطوبتی (مکان) نشان داد. نتایج تجزیه واریانس مرکب اثر ژنوتیپ را برای اکثر صفات معنی‌دار نشان داد. نتایج تجزیه همبستگی نیز بیانگر این بود که بین عملکرد دانه و درصد سبزینگی برگ (اسپاد) در شرایط دیم و بین عملکرد دانه و میزان آب ازدست‌رفته برگ در شرایط عدم تنش خشکی همبستگی مثبت و معنی‌داری (P<0.05) مشاهده گردید. نتایج تجزیه خوشه‌ای ژنوتیپ‌های موردمطالعه را در هر دو شرایط محیطی در سه گروه مجزا و متفاوت قرار داد. به‌طوری‌که بیشترین فاصله ژنتیکی در هر دو شرایط رطوبتی بین خوشه اول و سوم مشاهده گردید. تجزیه به مؤلفه‌های اصلی در شرایط عدم تنش خشکی و شرایط دیم به ترتیب 71% و 76% از تنوع موجود را توجیه نمودند. با توجه به مقایسه میانگین عملکرد دانه، ژنوتیپ‌های 7 (3790 کیلوگرم در هکتار)، 8 (3525 کیلوگرم در هکتار) و 13 (3305 کیلوگرم در هکتار) در شرایط عدم تنش خشکی و ژنوتیپ‌های‌ 13 (2147 کیلوگرم در هکتار)، 14 (2440 کیلوگرم در هکتار) و 17 (2254 کیلوگرم در هکتار) در شرایط دیم بیش‌ترین عملکرد دانه را تولید کردند.