On a representative leaf, the average trichome density on the upper side was For an estimated leaf area of 7. The SEM pictures show a striking landscape Fig. The whole leaf blade is covered with menacing hooked trichomes. Although trichome measurements were not made, one can see at least two size classes with the same orientation Fig. Trichomes seem to be densely spread on the leaf blade see section on estimates of trichome density , both on the blade itself Fig.
The pictures in Fig. These fine lines are larval silk spun by the caterpillars as a support for movement, and cover most of the surface, including the trichomes. In fact, perhaps adding insult to injury, trichomes may be used as supports for laying down the silk thread Fig. One can also see that many trichomes have their tips removed Fig. Many trichomes present on the main vein from the lower surface, where the larvae H. The role of trichomes as effective mechanical barriers to herbivores is well established Levin , Valverde et al.
Many other studies have shown the negative effect of trichomes on herbivores e. In my study, trichome presence and shape affected larval movement of non specialist Heliconius , confirming its defensive role.
On the other hand, movements by the specialist H. My observations on free ranging caterpillars showed that they usually stay on the under surface of the leaf, where trichome density is lower, crawling along the main vein up to the tip of the leaf. The fact that many hookless trichomes were found in this area suggests that hook removal may be an important adaptation that enables H.
Moreover, the fact that the larval faeces contained trichome hooks and not the whole trichome suggests that trichome trimming may be needed in order to handle trichomes. Finally, the potential harm trichomes may incur on a specialist was unknowingly demonstrated when I dropped a H. Silk weaving may also be important because it provides a surface to which the crochets can connect that is independent of leaf anatomy e.
For example, I noticed that crawling larva of H. A preliminary inspection on the legs of several Heliconius larvae did not reveal any noticeable difference in crochet size, number or arrangement that would explain this ability. However, the lateral sclerotized proleg plate Fig.
Could this help these larvae avoid entrapment? This hypothesis clearly deserves further investigation. Although no specific characteristic can be pinpointed as to how H. It would be interesting to ascertain whether there are costs associated with the seemingly ample advantage of exploiting a host that is unavailable to all other Heliconius.
The herbivore offense by H. I would like to thank Larry Gilbert for enthusiastic discussions regarding the project and for collecting P. Riess for helping in leaf tissue preparation and SEM operation; J. MacDougal for providing publication and discussions on the hooked Passiflora ; G.
Sword for suggesting the fecal analysis and A. Almeida, A. Freitas and J. Vasconcellos-Neto for improvements to the manuscript. Butterflies and plants were collected under permits from the Costa Rican government to Larry Gilbert.
Abrir menu Brasil. Neotropical Entomology. Abrir menu. Cardoso About the author. Herbivory; mechanical defense; insect-plant interaction. Cardoso Depto. Alexander, A. A study on the biology and behavior of caterpillars, pupae and emerging butterflies of the subfamily Heliconiinae in Trinidad, West Indies. Part I. Some aspects of larval behavior. Zoologica Benson, W. Coevolution of plants and herbivores: Passion flower butterflies.
Evolution Dussourd, D. Foraging with finesse: Caterpillar adaptations for circumventing plant defenses, p. Casey eds. Fordyce, J. The role of plant trichomes and caterpillar group size on growth and defence of the pipevine swallowtail Battus philenor J.
Gilbert, L. Butterfly-plant coevolution: Has Passiflora adenopoda won the selectional race with heliconiine butterflies? Science Amphilophium parkerii , Bignonia prieurei had trichomes with morphology intermediate between the cupular and patelliform variants Fig.
These intermediate morphologies were also observed in a single species e. Adenocalymma pedunculatum , Fig. Adenocalymma impressum , Manaosella cordifolia , Periathomega vellozoi , Pyrostegia venusta and Tanaecium pyramidatum. Active trichomes secreted hyaline and viscous nectar, which accumulated in the concave surface of trichomes and was eaten by insects, mostly ants. Initially we used information of positional and structural similarity to generate hypotheses of common origin. Four similar structural trichome types were described see details before on different vegetative plant parts.
Thus, ML optimizations of the four trichome morphotypes i. Further details on each reconstruction are presented below. Table 1. Likelihoods are reported as negative logarithms and the ancestral character state is presented in the last column. Estimates of the rates of evolution are also presented.
The estimated parameters of the evolutionary model favoured are presented in bold. Likelihoods are reported as negative logarithms and the ancestral character state is presented in the last column, based on a one-rate model of evolution Mk1. Evolution of non-glandular trichomes. Losses of these characters and the detailed maximum likelihood ML ancestral character state reconstructions are presented in Supplementary Data Fig.
Black portions of each pie chart represent the proportional likelihood of the appearance of dendritic non-glandular trichomes. The scale on the right is millions of years ago. Evolution of peltate glandular trichomes. Right: ML ancestral state reconstructions of trichome density. Left: ML ancestral state reconstructions of the diameter of the trichome glandular heads. Evolution of stipitate glandular trichomes.
ML ancestral character state reconstruction indicated nine independent evolutions of this trichome morphotype in that lineage. Black portions of each pie chart represent the proportional likelihood of stipitate glandular trichome appearances.
Losses of these characters and the detailed ML ancestral character state reconstructions are presented in Supplementary Data Fig. In this study we encountered four main trichome morphotypes i. At least for some plant parts, we corroborate the hypothesis of a single evolutionary origin for the different trichome types e. Trichomes often demonstrate variable macro- and micromorphological features, making it difficult to determine the exact trichome type that is being referred to in the literature Theobald et al.
In the specific case of Bignoniaceae, a wide range of terms has been used to describe the same trichome type Fig. Below we summarize major morphoanatomical features and the evolutionary history of each trichome type. The Ng trichomes of representatives of Bignonieae have only rarely been described in detail e.
Ogundipe and Wujek, Instead of being described in terms of their structure, Ng trichomes have been traditionally described in terms of their density and overall appearance. However, no information is available on the anatomy and developmental sequence of Ng trichomes in Bignoniaceae or other plant groups e. Lamiaceae; Naidu and Shah, Even though Ng trichomes have generally been treated as morphologically homogeneous structures, the variable number of cells and size and variable patterns of distribution of this trichome morphotype on different plant parts indicate the need for more detailed morphoevolutionary studies of trichomes in general.
Ancestral state reconstructions of Ng trichomes in Bignonieae indicated that simple and unbranched trichomes were present in the ancestor of Bignonieae, with branching trichomes having evolved at least eight times. This transition from simple to branched trichomes was similar to that observed in Brassicaceae, in which the pattern of trichome evolution indicated numerous innovations of trichome branching Beilstein et al.
Furthermore, a hierarchical pattern of occupation of trichomes over different vegetative plant parts was also observed during the evolutionary history of Bignonieae. More specifically, the MRCA of the tribe probably already had Ng trichomes on the branches, prophylls of the axillary buds, and petioles. However, it was only later that trichomes covered the surfaces of leaflet blades. In most species, the density of trichomes remained low and Ng trichomes remained unbranched. A few lineages recently acquired higher trichome densities e.
The Pg trichomes were first recorded in representatives of Bignoniaceae in the 19th century in taxonomic treatments of the Prodromus Systematis Naturalis Regni Vegetabilis Candolle, and Flora Brasiliensis Bureau and Schumann, However, in Rutaceae, such structures are present in almost all members of the family and represent secretory cavities Engler, ; Kubitzki et al.
The study of Pg trichomes conducted here revealed that even though these trichomes are identical in structure in all studied species, they are much denser in Amphilophium.
All these structures are composed of a glandular convex or rounded head of a variable number of cells. Furthermore, this trichome type has a single origin in Bignonieae. The morphological similarity of Pg among species and the phylogenetic pattern indicated that this secretory structure is best treated uniformly under the same terminology. We here propose that these structures are best treated morphologically as peltate glandular trichomes.
Ancestral character state reconstructions indicate that Pg trichomes were already present on both sides of the leaflet blades and all other vegetative portions of the MRCA of Bignonieae. However, Pg trichomes probably originated prior to the origin of Bignonieae, given that this trait has been documented in other representatives of Bignoniaceae, in three clades defined by Olmstead et al.
This trichome morphotype is widely distributed in Bignonieae, but has only been reported in a few representatives of the family in general, probably reflecting the lack of detailed studies of trichome structure in other lineages of Bignoniaceae. The density and size of the glandular heads represent the most variable features of Pg trichomes, differently from the other trichome types studied here. Ancestral state reconstructions of the individual features of this trichome type indicate that the MRCA of all Bignonieae probably had high densities of Pg trichomes with intermediate head size on the abaxial portion of leaflet blades.
Trichomes with large heads and high densities were relatively rare in Bignonieae, with huge large heads being restricted to two lineages Pyrostegia and Stizophyllum , and huge high densities only present in 11 lineages, and being particularly common in Amphilophium. This is the first record of Sg trichomes on the vegetative portions of representatives of Bignonieae.
This kind of glandular trichome generally lacks a sticky secretion, and has been associated with alternative biotic defences or direct defence against herbivores. This trichome type has never been associated with ant attraction, which has more generally been associated with nectar-secreting trichomes.
For example, adhesive glandular trichomes, a kind of Sg trichome, have been associated with spider bodyguards that often feed on carcases of insects that adhere to these trichomes Morais-Filho and Romero, Ancestral character state reconstructions of this trichome morphotype indicate that Sg trichomes were not present in the MRCA of the group, independent of the plant portions analysed, and suggest that this trichome type has evolved at least nine times in the group.
These results indicate that even though there is general structural similarity between the Sg trichomes encountered in the various lineages of Bignonieae, these similarities are not based on a common ancestry, suggesting a homoplastic pattern of evolution of these secretory structures.
These trichomes are associated with nectar secretion in Bignoniaceae, and have been commonly called extrafloral nectaries EFNs as they are not thought to be involved in pollination Elias, This terminology EFNs was widely used in Bignoniaceae in spite of the lack of functional evidence for this structure, i. Notably, this trichome type has been the most widely reported in all previous anatomical studies conducted in Bignoniaceae Fig.
A mixture of terminologies has been used to designate these structures, obscuring the phylogenetic signal of this trichome type among species. On the other hand, terminologies that are more directly associated with the overall morphological structure of trichomes have also been proposed. Furthermore, this study also corroborates the observation that the patelliform and cupular trichomes have a uniform anatomical structure Rivera, In this case, the structural changes resulting in the evolution of these two trichome types would have occurred before the diversification of Bignonieae, since both types of trichomes were already present in the MRCA of the tribe.
However, this hypothesis remains to be tested in a broader systematic context, in combination with detailed ontogenetic and evolutionary studies of both trichome types. Ontogenetic studies conducted with other representatives of Lamiales demonstrated an ontogenetic resemblance between the patelliform glandular trichomes of the Acanthaceae McDade and Turner, and those of Bignoniaceae Inamdar, ; Subramanian and Inamdar, a , b.
In both cases, the trichomes are formed from a single initial protodermic cell, suggesting that the trichomes found in both families might have a common origin, which would imply a more ancient origin for this structure. Since these trichomes have been shown to be associated with ant attraction, and species with higher numbers of nectar-secreting trichomes had higher abundances of ants on the plants Nogueira et al.
Thus, the clustering of such secretory structures on particular plant regions, as observed on the prophylls of axillary buds and interpetiolar portions of stems, suggests that these trichomes could be indirect protecting plant tissues that are costly to produce i.
Despite the presumed functional importance of trichomes in different plant species and the importance for microevolutionary studies Levin, , little is still known about the macroevolutionary patterns of those structures in different plant families and on different plant organs.
Traditionally, trichomes have been thought to evolve multiple times in the history of angiosperms. Theobald et al. Only stipitate glandular trichomes seem to have evolved multiple times independently of the position of their occurrence on vegetative organs. Our results indicate that most trichomes found in representatives of Bignonieae had the same origin and were similar morphologically, and are thus best treated under the same name in each morphotype.
A standardization of trichome terminology greatly facilitates comparisons among taxa, allowing inferences on relationships as well as inferences on their eco-evolutionary consequences. Although we have improved the understanding of trichome evolution in a clade of angiosperms, it still remains unclear how trichomes interact ontogenetically and ecologically.
For example, trade-off between trichome types could explain patterns of evolution in some clades e. No information is available about the genetic basis of these trichome types and relationships with the patterns of position, density and size of trichomes. It is possible that putative heterotopic events as discussed by Baum and Donoghue, , with modifications of expression of some types of trichomes in specific plant parts, may have occurred during the evolutionary history of Bignonieae.
Data directly related to the function of different trichomes are of importance for understanding the role of selection agents such as herbivores, sunlight and water for the evolution of trichome types. Experimental approaches that test functional hypotheses of trichomes in Bignonieae may be able to address the interpopulation variation of trichome characters in the future. This paper is part of the doctoral thesis of A.
Rando, Luciano P. Izzo, Thomas M. Lewinsohn, Robin Burnham and one anonymous reviewer for fruitful discussions and comments on this manuscript. Google Scholar. Google Preview. Evolution of oil-producing trichomes in Sisyrinchium Iridaceae : insights from the first comprehensive phylogenetic analysis of the genus Annals of Botany Fahn A Structural and functional properties of trichomes of xeromorphic leaves Annals of Botany 57 Annals of Botany Stellfeld var.
Inamdar JA Structure and ontogeny of foliar nectaries and stomata in Bignonia chamberlaynii Proceedings of the Indian Academy of Sciences 70 Kaplan I Dively GP Denno RF The costs of anti-herbivore defense traits in agricultural crop plants: a case study involving leafhoppers and trichomes Ecological Applications 19 Eudicots: Sapindales, Cucurbitales, Myrtaceae the families and genera of vascular plants Hamburg Springer Lohmann LG Phylogeny, classification, morphological diversification and biogeography of Bignonieae Bignoniaceae.
Botanical Journal of the Linnean Society Mauricio R Ontogenetics of QTL: the genetic architecture of trichome density over time in Arabidopsis thaliana Genetica 75 Ness JH Catalpa bignonioides alters extrafloral nectar production after herbivory and attracts ant bodyguards Oecologia Plant Ecology a Payne WW A glossary of plant hair terminology Brittonia 30 Stephenson AG The role of the extrafloral nectaries of Catalpa speciosa in limiting herbivory and increasing fruit production Ecology 63 Mapping quantitative trait loci in multiple populations of Arabidopsis thaliana identifies natural allelic variation for trichome density Genetics Oxford University Press is a department of the University of Oxford.
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Close mobile search navigation Article Navigation. Volume Trichome structure and evolution in Neotropical lianas. Anselmo Nogueira , Anselmo Nogueira. E-mail anselmoeco yahoo. Oxford Academic. Juliana Hanna Leite El Ottra. Silvia Rodrigues Machado.
Revision requested:. Antixenosis refers to the plants having certain characteristics, including morphological and chemical, that are non-preferable to the pest Pedigo and Rice, With morphological antixenosis, plants have structures that physically impede the normal behaviors of the pest, as is the case for non-glandular leaf trichomes Pedigo and Rice, Morphological antixenosis provides a first line of defense that is not easily overcome by the pest as opposed to most chemical-based resistance Pedigo and Rice, Thus, trichomes are one of the potential durable resistance targets for plant breeders.
Trichomes have been a target for breeding programs in a range of crop species. Trichomes have been studied in several dicot species including Brassica spp. Glabrous mutants were found to be unfavorable to whitefly in cotton Gossypium arboreum and favorable to larvae of a white butterfly and a cabbage fly in Arabidopsis halleri Sato and Kudoh, ; Grover et al.
Previous work on the glabrous cotton mutant suggests that a single recessive gene was responsible for absence of trichomes Baljinder et al. In Arabidopsis spp. In Vitis , Barba et al. However, the QTL for trichome density on chromosomes 1 and 15 found by Barba et al. Phylloxera, Daktulosphaira vitifoliae Fitch , is especially a problem on foliage of cold-hardy hybrid wine grapes, which dominate Vitis species grown in the Midwest Yin et al. We hypothesized that high trichome density was associated with resistance to foliar phylloxera.
The phylloxera-resistant parent, MN, showed more trichomes than the susceptible parent, MN Dormant, two-node cuttings were made and moved to water or perlite to induce budbreak. Leaves were kept in plastic bags and maintained on ice until trichome scoring. Ribbon and simple types of trichomes Figure 1 were scored for their density using a 0—6 rating scale Figure 2 under When the first mature leaf was too small or the first node died, measurements were taken on the next available leaf or the lower node.
Several density traits not recorded in were added in ; only trichomes on leaf and vein were scored in field samples Supplementary Table 1. Figure 2. A representative visual scale to rate ribbon trichome density on adaxial petiole on first mature leaf samples. Figure 3. Leaf positions where trichomes were scored: leaf blade L , vein V , petiole P , and margin M; only on the adaxial side on both sides of the leaf.
A comprehensive score was assigned to each of L, V, P, and M by evaluating these multiple areas. Pearson correlations were calculated between trichome density traits across all three experiments and foliar phylloxera traits measured previously by Clark et al.
Two-sided t -tests with unequal variances of foliar phylloxera traits Clark et al. Analysis of variance ANOVA was conducted on trichome density through fitting a linear model of genotype as a fixed effect and replication as a random effect. Error normality of the linear model and variance homogeneity among GE genotypes were examined using plot.
Natural log and square root transformations were performed on density traits that did not have residual normality. If a transformation improved the error variance to normal or nearly normal, that transformation was used. If a trichome density trait had a non-normal error distribution or unequal variances, no ANOVA results were reported.
Up to five replications of greenhouse-grown except MN was field-grown MN, MN, and grandparents were scored in the fine mapping experiment described below. Mean scores of ribbon and simple types on leaf and vein were compared using TukeyHSD function in R after fitting a linear model of effects of genotype by experiment , , field, and fine mapping experiment and replication. Maternal and paternal linkage maps were constructed in JoinMap 4. For trichome density traits with approximately normal residuals, a multiple imputation method was performed with imputations and a step size of 1.
For trichome density traits with non-normal residual distributions, the Haley—Knott HK method was performed with a step size of 1. Effect plots were examined for each marker at the peak of a QTL, and the high trichome density allele and low trichome density allele were recorded. Based on preliminary QTL results of experiment 1, recombinant genotypes from population GE within Because the QTL on chromosome 1 10— Due to the young vine age of GE plants, available leaf materials for replication were variable.
Those leaves were kept in plastic bags and maintained on ice until digital images were acquired through scanning. Replications of the same genotype were scanned together under 1, dpi, flipped to the other side of the leaves, scanned, and cropped around the leaves. Each scanned image was viewed in Windows Photo Viewer, zoomed in, and scored using the same density scale Figure 2.
A sex-averaged consensus genetic map was constructed from 1, quality-controlled haplotype markers in LepMap3 Rastas, as previously described Zou et al.
To fine map the trichome QTL regions that were repeatedly detected in experiment 1, rhAmpSeq data of recombinant genotypes at each locus of interest were associated with phenotypes collected in experiment 2. Genotypes were organized into graphical haplotype classes with high H or low trichome density L haplotypes spanning the QTL region.
The genetic region where the presence or loss of the H or L haplotype was associated with the high or low density phenotype was determined as the fine mapped region. For ribbon trichome density, an additional rater effect was included. For traits with non-normal residuals, natural log or square root transformations were performed, and their residuals were re-examined for improvement in normality.
ANOVA was not conducted if the assumption of residual normality was not met. Although outside of our fine mapped region, three candidate genes from Barba et al. For long-range PCR, primers were designed with sample-specific barcodes targeting these candidate genes at 8. For two of the regions 9. For the third region 8.
To confirm the presence and approximate size of the PCR products, samples were visualized on 1. Samples were demultiplexed in minibar Krehenwinkel et al. Residual normality and variance equality were also checked. TukeyHSD was conducted to separate means of these genotypes, and results were visualized using ggplot2 Wickham, Phenotypic correlations r ranged from 0. The checks, including the parents, were consistent across all evaluations , , field, and fine mapping experiment.
The hirsute V. In general, MN had numerically higher trichome density than MN for ribbon trichome density on abaxial vein, adaxial leaf, and adaxial vein and simple trichome density on abaxial vein in all evaluations Supplementary Figure 2. The exception was for simple trichome density on adaxial vein where MN had numerically higher value than MN Supplementary Figure 2. The sources of high ribbon trichome density of MN likely came from MN on adaxial leaf and vein.
The equal variances assumption was also not met for simple density on adaxial leaf. We observed only one interaction between the QTL on chromosomes 1 and 5 for abaxial leaf ribbon trichome density in and field data not shown. Figure 4. Multiple bars of the same color and pattern suggest that the trait has been detected in multiple experiments , , or field.
Table 1. Table 2. For genetic regions on chromosomes 1, 5, 10, and 17, we detected coincident QTL for multiple trichome density traits. Due to the number of traits measured, we will discuss ribbon and simple trichome separately. Four ribbon trichome density traits were mapped to The chromosome 1 QTL for adaxial leaf and vein positions was repeatedly detected in two experiments Table 1.
Six simple trichome density traits were mapped to the chromosome 1 QTL region 10— QTL for abaxial leaf, abaxial vein, and adaxial vein positions has been detected in two or more experiments Table 2. The associations between trichomes and foliar phylloxera severity were non-significant except that trichomes on leaf blade and vein were significantly negatively correlated with phylloxera severity.
The presence of simple trichome on leaf and vein, independent of the adaxial or abaxial surface, significantly affected the number of galls, percent leaves with galls, galls per leaf, visual rating, and area under the disease-progress curve AUDPC; Supplementary Table 3.
We found correlation coefficient r of In addition to the weak phenotypic associations, QTL of trichome density and incidence was in different chromosomes from those found for phylloxera severity traits that were on chromosome 14 of the MN map Clark et al. Figure 5. Pearson correlation coefficients between foliar phylloxera traits Clark et al.
Blank cells: non-significant correlation coefficient; black lines divide the matrix into phylloxera traits, ribbon trichome density traits, and simple trichome density traits; forced dormant cuttings, forced dormant cuttings, 19F: field-grown leaves. The QTL from We found residual normality and a significant haplotype class effect of ANOVA for ribbon density on adaxial leaf, adaxial vein, and abaxial vein and simple density on adaxial vein and abaxial vein Table 3.
Individuals with L haplotypes at For QTL on chromosome 10, we were not able to determine clear graphical genotypes segregating for ribbon trichome density after controlling for the chromosome 1 QTL data not shown. For QTL on chromosome 1 for simple trichome density on adaxial vein, the graphical genotypes showed that the region Table 3.
Analysis of variance p -values for trichome density in October fitting a linear model of effects of haplotype Hap , replication Rep , rater Rater , and number of genotypes within each haplotype Hap:NoGeno. The whole-genome shotgun coverage of MN and MN at the fine mapped region containing these genes is shown in Figure 6.
Figure 6. Marker positions, gene annotation, and reads coverage for the whole-genome shotgun sequencing of MN and MN at the fine mapped trichome density region, MN and MN are parents of the cold-hardy hybrid grape population. The gene annotation is illustrated in the upper panel. The read depth is plotted in the middle panel. The markers significantly associated with trichome density are in red, and the closest flanking markers are in gray. The three candidate genes suggested by Barba et al.
Sequence variations at candidate genes WER and SCR-LIKE 21 were obtained from nanopore sequencing, whereas variations at candidate gene ZFP5 were obtained from whole-genome shotgun sequencing because of the low read depth of nanopore sequencing at this gene. The long-range PCR nanopore sequencing results show a polymorphism at the end of the exon of the first candidate gene transcription factor WER between the parents.
MN had an 8 bp homozygous deletion, and MN had an 8 bp heterozygous deletion Supplementary Figure 3. For example, upstream of the exon of ZFP5, MN had homozygous deletions at two sites where MN had a heterozygous deletion or no variation; MN had a 10 bp heterozygous deletion at a third site with no insertion—deletion polymorphism in MN data not shown. For the third candidate gene SCR-LIKE 21 , MN had a 16 bp heterozygous insertion, and MN had an 8 bp heterozygous deletion around this region at the beginning of the coding sequence data not shown.
The QTL on chromosome 1 found in this study was previously identified by Barba et al. They reported QTL on chromosome 1 from 8. We validated their QTL in a different genetic background using a Minnesota hybrid grape population with genomic contributions from six Vitis species Teh et al.
Due to different populations studied and the different phenotyping methods used, our QTL 10— We further fine mapped the QTL for three traits: ribbon density on adaxial vein, ribbon density on adaxial leaf, and simple density on abaxial vein to a kb region The high correlations between trichome density on forced cuttings in 2 years and on field-grown leaves suggested repeatability of the experiment.
Phenotyping resolution, such as scanner resolution, can be improved for simple trichomes on adaxial surfaces. This likely led to QTL mapping difficulties and potentially contributed to the low correlation with phylloxera resistance. Alternative methods of trichome scoring should be investigated, such as scoring on multiple leaves as done by Barba et al.
The fine mapping experiment was not replicated, and our results serve as a starting place for future validation studies. Even though the QTL mapping experiment was replicated, we saw relatively high variability within each genotype Supplementary Figures 2 , 4.
It might be due to the variability in trichome scores between the last tender and first mature leaves. Future work should look at developmental regulation in trichome within a single genotype. Another possible limitation was the high SNP error rate of nanopore technology, limiting the analysis to only insertion, and deletion variants Chaisson et al. We investigated whole-genome shotgun sequencing data on the parents.
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