High Trichome Density Research Articles

Dew Evaporation Amount and Its Influencing Factors in an Urban Ecosystem in Northeastern China

Dew is an important water input and promotes plant growth. Dew condenses on plant leaves at night, and a portion of this dew returns to the atmosphere through evaporation. The amount of dew that evaporates is not equal to the amount of condensation; however, the dew evaporation process has not received enough attention. By monitoring the dew condensation and evaporation processes associated with four typical shrubs (Syringa, Hemiptelea, Buxus, and Cornus) in northeast China, we found that dew condensation started approximately 30 min after sunset, finished approximately 30 min before sunrise, and then turned to the evaporation phase. Dew had completely depleted approximately 4 h after sunrise. The dew evaporation period was negatively correlated with the wind speed (p < 0.01) and positively correlated with temperature, solar radiation, and relative humidity (RH) (p < 0.01). The average evaporation periods of Syringa, Buxus, Cornus, and Hemiptelea were 282 ± 21 min, 255 ± 26 min, 242 ± 22 min, and 229 ± 17 min, respectively. The daily evaporation amounts in May and September reached the minimum and maximum values, respectively, and the evaporation intensity of dew was positively correlated with RH (p < 0.01). There was no significant difference in the daily evaporation amounts of Syringa, Hemiptelea, Buxus, or Cornus (p > 0.05), and the annual evaporation amounts of these four plants were 17.05 mm/y, 16.38 mm/y, 21.94 mm/y, and 16.15 mm/y, respectively. The microstructure of leaves affected both the rate and amount of evaporation. Dew evaporated faster on hydrophilic leaves, and leaves with high trichome and stomatal densities had lower proportions of the dew evaporation amount to the condensation amount. The proportions of the dew evaporation amount to the condensation amount derived for Syringa, Hemiptelea, Buxus, and Cornus were 60.38%, 46.07%, 57.24%, and 52.81%, respectively. This study supplements our understanding of dew evaporation amounts, providing information that was missing in the near-surface hydrological cycle and aiding in the assessment of the ecological significance of dew to plants.

Density, Orientation, and Distribution of Foliar Trichomes in Selected Philippine Traditional Rice Varieties with Resistance to Scirpophaga spp.

Pest infestation restricts rice productivity and, among rice pests, the stem borers (Scirpophaga spp.) caused substantial damage of > 20% yield loss. Host resistance is considered the most effective, economical, and environmentally friendly way for rice pest management, and Philippine traditional rice varieties (TRVs) are potential sources of genes useful in breeding for pest resistance. Leaf trichomes are the first physical barrier against any invading plant pests and to characterize the quantitative variations of foliar trichomes of six selected TRVs identified to have resistance – namely, Dinorado, Hinumay, Inarciaga, RED 18, C-4 Dinorado, and Mukol – these TRVs were evaluated using digital light microscopy. RED 18 consistently had the highest trichome density (5.374–9.390/mm2) in each and across the 2018 wet season (WS), 2019 WS, and 2020 dry season (DS) – even significantly higher (P > 0.05) than the resistant check TKM6 (4.489–5.783/mm2). For trichome orientation, Mukol (59.151–71.617°), and Inarciaga (57.395–72.464°) consistently had higher and/or statistically comparable angle values to the resistant TKM6 (59.654–71.617°), across each and 2018 WS, 2019 WS, and 2020 DS (P > 0.05). Within- and between-genotype variability showed that adaxial foliar trichomes have varying density and were not uniformly distributed across the leaf surface: densest (4.560–5.456/mm2) and mostly distributed (49.086–50.532%) in the apical zone of the leaf surface, and least dense (2.623–2.834/mm2) and rarely distributed (16.439–18.806%) in the basal zone. Based on desirable trichome traits and statistical similarities to TKM6, hierarchical cluster analysis delineated RED 18, Inarciaga, and Mukol as excellent sources of trichome traits that will improve plant structural defense against stem borers.

Overexpression of CsMIXTA, a Transcription Factor from Cannabis sativa, Increases Glandular Trichome Density in Tobacco Leaves.

Cannabinoids are synthesized in glandular stalked trichomes on the female flowers of Cannabis sativa (cannabis). The regulation of glandular trichome development has not been characterized in cannabis. We recently identified an R2R3-MYB transcription factor, CsMIXTA, which could be involved in trichome morphogenesis in cannabis. Some homologous genes of CsMIXTA are known to function in glandular trichome initiation in other plant species. CsMIXTA is highly expressed in flower tissue compared to vegetative tissues. Interestingly, CsMIXTA is also highly expressed in trichomes isolated from female flower tissue. In addition, CsMIXTA is upregulated during the peak stages of female flower maturation in correlation with some cannabinoid biosynthetic genes. Transient expression in Nicotiana benthamiana showed that CsMIXTA is localized in the nucleus. Furthermore, yeast transcriptional activation assay demonstrated that CsMIXTA has transactivation activity. Overexpression of CsMIXTA in Nicotiana tabacum resulted in higher trichome density, larger trichome size, and more branching on stalked glandular trichomes. The results indicate that CsMIXTA not only promotes glandular trichome initiation in epidermal cells, but also regulates trichome development in tobacco leaves. In this report, we characterized the novel function of the first cannabis transcription factor that may be critical for glandular trichome morphogenesis.

Leaf trait association in relation to herbivore defense, drought resistance, and economics in a tropical invasive plant

Exploring how functional traits vary and covary is important to understand plant responses to environmental change. However, we have limited understanding of the ways multiple functional traits vary and covary within invasive species. We measured 12 leaf traits of an invasive plant Chromolaena odorata, associated with plant or leaf economics, herbivore defense, and drought resistance on 10 introduced populations from Asia and 12 native populations from South and Central America, selected across a broad range of climatic conditions, and grown in a common garden. Species' range and climatic conditions influenced leaf traits, but trait variation across climate space differed between the introduced and native ranges. Traits that confer defense against herbivores and drought resistance were associated with economic strategy, but the patterns differed by range. Plants from introduced populations that were at the fast-return end of the spectrum (high photosynthetic capacity) had high physical defense traits (high trichome density), whereas plants from native populations that were at the fast-return end of the spectrum had high drought escape traits (early leaf senescence and high percentage of withered shoots). Our results indicate that invasive plants can rapidly adapt to novel environmental conditions. Chromolaena odorata showed multiple different functional trait covariation patterns and clines in the native and introduced ranges. Our results emphasize that interaction between multiple traits or functions should be considered when investigating the adaptive evolution of invasive plants.

Resistance of chickpea cultivars to Chloridea virescens (Lepidoptera: Noctuidae)

Chickpea is a legume with nutrient-rich grains important for human feeding. Tobacco budworm, Chloridea virescens (Lepidoptera: Noctuidae), is one of the most major pests of chickpea (Cicer arietinum) in Brazil. This pest damages leaves, flowers, pods, and grains. Plant resistance to insects is an important tactic of pest management, which usually facilitates and reduce costs of implementing an Integrated Pest Management for farmers. Thus, this study aimed to evaluate the resistance in chickpea cultivars to C. virescens. Six chickpea cultivars were evaluated for antixenosis, initial antibiotic parameters, and behavior under field conditions. The cultivars BRS Kalifa and BRS Cícero were less attractive in a free-choice test, while Jamu 96 and BRS Kalifa were less attractive in a no-choice test. BRS Kalifa and BRS Toro leaves had a higher trichome density. Jamu 96 and BRS Toro had higher contents of oxalic and malic acids. C. virescens larvae in BRS Cícero, BRS Toro, and BRS Kalifa showed the lowest weights. Jamu 96 pods were the least damaged, and BRS Aleppo and Jamu 96 had the highest yields. The chickpea cultivars Jamu 96 and BRS Aleppo, which had resistance levels and mechanisms, can be used in integrated pest management programs to control C. virescens.

The transcription factors TLR1 and TLR2 negatively regulate trichome density and artemisinin levels in Artemisia annua.

The important antimalarial drug artemisinin is biosynthesized and stored in Artemisia annua glandular trichomes and the artemisinin content correlates with trichome density; however, the factors affecting trichome development are largely unknown. Here, we demonstrate that the A. annua R2R3 MYB transcription factor TrichomeLess Regulator 1 (TLR1) negatively regulates trichome development. In A. annua, TLR1 overexpression lines had 44.7%-64.0% lower trichome density and 11.5%-49.4% lower artemisinin contents and TLR1-RNAi lines had 33%-93.3% higher trichome density and 32.2%-84.0% higher artemisinin contents compared with non-transgenic controls. TLR1 also negatively regulates the expression of anthocyanin biosynthetic pathway genes in A. annua. When heterologously expressed in Arabidopsis thaliana, TLR1 interacts with GLABROUS3a, positive regulator of trichome development, and represses trichome development. Yeast two-hybrid and pull-down assays indicated that TLR1 interacts with the WUSCHEL homeobox (WOX) protein AaWOX1, which interacts with the LEAFY-like transcription factor TLR2. TLR2 overexpression in Arabidopsis and A. annua showed that TLR2 reduces trichome development by reducing gibberellin levels. Furthermore, artemisinin contents were 19%-43% lower in TLR2-overexpressing A. annua plants compared to controls. These data indicate that TLR1 and TLR2 negatively regulate trichome density by lowering gibberellin levels and may enable approaches to enhance artemisinin yields.

Morphological and biochemical screening of upland cotton (Gossypium hirsutum L.) hybrids for jassid (Amrasca devastans Dist.) resistance

The current experiment was carried out in the field in a Randomized Block Design (RBD) for parents viz., MCU5, MCU7, CO14, and CO17, which were utilized as lines (high yield) and KC2, KC3, NDLH1755 and NDLH1938, which were used as testers throughout the summer season of 2021. From the mean values among all parents calculated, KC 2 had lowest jassid population of mean 4.13 numbers per leaf, highest amount of phenol (3.72 mg/g), low amount of reducing sugars (1.22 mg/g) and high chlorophyll index (58.73). Among other hybrids the hybrid MCU 5 × KC 3 outperformed for highest phenol content (3.72 mg/g), highest chlorophyll index (58.73) with lowest Jassid count (4.13 numbers/ plant). Hence from the correlation results, number of jassids per plant would be lower for high phenolic content, low reducing sugar, lower soluble proteins, higher chlorophyll index and higher trichome density. Hence breeding could be made for resistance to jassids by insight into this biochemical analysis and trichome density of the cultivar which would help reduce use of insecticides and pest load from the fields thereby enhancing the yield of the population.

Variability in leaf morphological traits of an endemic Mexican oak ( Quercus mexicana Bonpl.) along an environmental gradient

Background: Phenotypic and functional traits of plant populations vary with environmental conditions at local and regional scales. The analysis of these traits along environmental gradients provides information on the differential response of populations to climate changes.
 Objective: We analyzed the leaf morphological variation of an endemic oak to identify the degree of population differentiation along an environmental gradient.
 Study species: Quercus mexicana Bonpl. (Fagaceae).
 Study site and dates: Samples were collected from 39 populations in the Sierra Madre Oriental and east of the Trans-Mexican Volcanic Belt from 2014 to 2016.
 Methods: We measured eight macromorphological traits in 5,507 leaves and three micromorphological traits in 228 leaves. We performed univariate and multivariate statistical analyses to assess the morphological differentiation among populations, and the relationship between variation in leaf traits and environmental variables related to temperature and water availability.
 Results: Populations of Q. mexicana showed leaf morphological differentiation along its distribution. Significant linear correlations were found between leaf traits and environmental variables. Smaller and thicker leaves with lower density of trichomes and smaller stomata were found in populations located in more arid regions. In contrast, larger and thinner leaves with higher trichome density and larger stomata occurred in more humid places.
 Conclusions: Populations of Q . mexicana are adapted to a wide range of climatic conditions. Considering the predictive future climatic changes for the region ( i.e ., warmer and drier conditions), Q . mexicana populations with traits better adapted to a more humid and cooler environments could be negatively affected.

Performance of Tetranychus urticae (Acari: Tetranychidae) on six cotton varieties with varying degree of leaf pubescence

In this study, we investigated the effect of leaf hairiness, based on non-glandular trichome density, of six cotton varieties (Gloria, Lima, Carla, DP-396, Edessa and ST-468) on the development, reproduction and population parameters of Tetranychus urticae (Acari: Tetranychidae) under controlled conditions. According to trichome densities (mean number/cm2) on the abaxial surface of cotton leaves: Edessa (583.8) and ST-468 (569.9) were grouped as high density; DP-396 (394.9) and Carla (367.5), medium density; Lima (20.4) and Gloria (13.3), low density. As a result, total development periods of T. urticae in Gloria, Lima, Carla, DP-396, Edessa and ST-468 varieties were 9.7, 9.8, 10.6, 10.6, 11.9 and 11.8 days, respectively. The developmental periods of immature stages and total preadults increased significantly with increasing leaf trichome density. The longest oviposition period of T. urticae was detected in Gloria (27.5 days) and Lima (25.1 days) and the shortest was in Edessa (16.4 days) and ST-468 (17.4 days). The highest total fecundity was determined in Gloria (135.6 eggs) and Lima (131.4 eggs) varieties. The highest intrinsic rate of increase (r), finite rate of increase (l) and net reproductive rate (R0) were obtained in Gloria, Lima, Carla and DP-396, the lowest in Edessa and ST-468 varieties. The longest mean generation time (T) was detected in Edessa (19.0 days) and ST-468 (18.6 days). The result of this study showed that cotton varieties with high trichome density negatively affected the development, reproduction and population parameters of T. urticae.

Antixenosis in cotton genotypes (Gossypium hirsutum var. marie galante) to Spodoptera frugiperda (Lepidoptera: Noctuidae) mediated by trichome and gossypol densities

Cotton (Gossypium hirsutum L.) is one of the most important crops in Brazil and pest incidence limits its yields. The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), native to tropical and subtropical America, spread and rapidly became an invasive pest worldwide. It is a polyphagous pest that feeds on up to 353 plant species including cotton. The objective of this study was to evaluate the antixenosis to S. frugiperda in 27 cotton genotypes, comparing varieties with non- commercial genotypes. The attractiveness was estimated in no-choice and free-choice tests, offering leaf discs of the 27 cotton genotypes to S. frugiperda, and counting the number of caterpillars feeding at 3, 5, 10, 15, and 30 minutes and 1, 2, 6, 12, and 24 hours after their release. The numbers of trichomes and gossypol glands per cm2 were measured on abaxial and adaxial surface. The free-choice test was performed in a randomized block design with the 27 genotypes (treatments) and 20 arenas (replicates). The no-choice assay was conducted as a completely randomized design with 18 genotypes and 20 replicates. The non-commercial genotypes PI0440, CE0467, PI0416, BA0512 and MA0425 presented antixenosis against S. frugiperda. In the free-choice test the cultivar BRS Buriti and the genotype PI0429 were the most attractive to S. frugiperda, while in no-choice test, the genotype PI0429 was the most attractive. High trichome density and gossypol glands did not influence the attractiveness of S. frugiperda in cotton genotypes, while the absence of trichomes was repellent to the caterpillars. There is polymorphism among cotton genotypes to attractiveness to the pest, and the genotypes with antixenosis can be used in future study in plant breeding program as donor source of resistance to S. frugiperda

Spot blotch disease of wheat as influenced by foliar trichome and stomata density

Spot blotch, caused by Bipolaris sorokiniana, is a potent biotic constraint to wheat crop leading to substantial yield abatement in warm humid South Asia (e.g. India, Nepal and Bangladesh) and other major wheat-growing countries such as Canada, the United States, Brazil and Australia. A set of 98 bread wheat genotypes were evaluated over two growing seasons to investigate the relationship among foliar trichome, stomata density, and susceptibility to the spot blotch pathogen. The higher density of trichomes (90-140 mm −2 ) on the adaxial surface of flag leaves entrapped 32-74 mm −2 pathogen spores. It restricted the dew droplets size (0.15–0.3 mm 2 ) on the flag leaves and thus prevented direct contact between the spores and the leaf epidermis. Trichome density was negatively associated with the disease development and spore germination but positively associated with grain size and the number of spores entrapped on trichomes per mm 2 . Conversely, stomata density was positively associated with the development of the disease. Cluster and principal component analyses divided trichome density, the number of spores trapped on trichome per mm 2 , and thousand grain weight into one group and stomata density, the area under disease progress curve, percent spore germination, and dew scale into another group. The results from this study provided a novel insight to breeders where the selection of bread wheat genotypes with high trichome (90-140 mm −2 ) and low stomata density (72-90 mm −2 ) on foliage could enhance spot blotch resistance in wheat. • Spot blotch of wheat reduces up to 30% yield in the Indian subcontinent. • The relationship among foliar trichome, stomata density, and susceptibility to the spot blotch pathogen was studied. • The higher density of trichomes (90-140 mm −2 ) entrapped 32-74 mm −2 spores prevented direct contact between the spores and the leaf epidermis. • This study assists breeders for the selection of bread wheat genotypes with high trichomes and low stomata density on foliage could enhance spot blotch resistance.

Transcriptional regulation of flavonoid biosynthesis in Artemisia annua by AaYABBY5

Artemisia annua is a medicinal plant rich in terpenes and flavonoids with useful biological activities such as antioxidant, anticancer, and antimalarial activities. The transcriptional regulation of flavonoid biosynthesis in A. annua has not been well-studied. In this study, we identified a YABBY family transcription factor, AaYABBY5, as a positive regulator of anthocyanin and total flavonoid contents in A. annua. AaYABBY5 was selected based on its similar expression pattern to the phenylalanine ammonia lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), and flavonol synthase (FLS) genes. A transient dual-luciferase assay in Nicotiana bethamiana with the AaYABBY5 effector showed a significant increase in the activity of the downstream LUC gene, with reporters AaPAL, AaCHS, AaCHI, and AaUFGT. The yeast one-hybrid system further confirmed the direct activation of these promoters by AaYABBY5. Gene expression analysis of stably transformed AaYABBY5 overexpression, AaYABBY5 antisense, and control plants revealed a significant increase in the expression of AaPAL, AaCHS, AaCHI, AaFLS, AaFSII, AaLDOX, and AaUFGT in AaYABBY5 overexpression plants. Moreover, their total flavonoid content and anthocyanin content were also found to increase. AaYABBY5 antisense plants showed a significant decrease in the expression of flavonoid biosynthetic genes, as well as a decrease in anthocyanin and total flavonoid contents. In addition, phenotypic analysis revealed deep purple-pigmented stems, an increase in the leaf lamina size, and higher trichome densities in AaYABBY5 overexpression plants. Together, these data proved that AaYABBY5 is a positive regulator of flavonoid biosynthesis in A. annua. Our study provides candidate transcription factors for the improvement of flavonoid concentrations in A. annua and can be further extended to elucidate its mechanism of regulating trichome development.

Assessment of phenotypic diversity in the USDA, National Plant Germplasm System (NPGS) guayule germplasm collection

Phenotypic characterization on historical breeding lines and wild genetic resources from the 1950′s to 1990′s of the rubber-bearing plant guayule (Parthenium argentatum A. Gray) and hybrids was conducted. Variation among germplasm on seed weight and germination was determined along with leaf traits and trichomes using image analyses. Flow cytometry was performed to estimate diversity in ploidy levels. Tetraploid guayule was the predominant type in the germplasm collection (64%), followed by triploids (34%), pentaploids (1.5%), and hexaploid (1%). No plants with octaploid or higher ploidy level were observed. Guayule 100-seed weight averaged 57.5 mg and was determined to have significant positive correlation to 7 and 14-day seed germination and seed size for this seed lot. Phenotypic similarity among germplasm was determined from quantitative analysis of leaf traits and trichomes. Measurements of other traits on young leaves were highly correlated to those on mature leaves. Most leaf traits within each development stage were found to be positively correlated. Guayule leaves averaged 6.85 cm long and 2.06 cm wide, with 1–6 serrations. Leaf serration height ranged from 2.9 to 6.4 mm. Germplasm lines AZ-2, AZ-3, and N566 had the greatest number of serrations, while R1093 and W6–429 with the least number. Trichome density was consistent between young and mature leaves with average density of 17 trichomes per 0.04 mm2. Accessions R1100, AZ-3, and CAL-4 had the highest trichome density (>21 trichomes per 0.04 mm2). The results from analyzing the relatively high number of plants for seed parameters, leaf traits and ploidy are useful for optimizing germplasm collection and to better aid agronomic management practices and utilization of guayule germplasm for crop improvement activities.

Micropropagation of Rare Scutellaria havanensis Jacq. and Preliminary Studies on Antioxidant Capacity and Anti-Cancer Potential.

We report the development of in vitro propagation protocols through an adventitious shoot induction pathway for a rare and medicinal Scutellaria havanensis. In vitro propagation studies using nodal explants showed MS medium supplemented with 10 µM 6-Benzylaminopurine induced the highest number of adventitious shoots in a time-dependent manner. A ten-day incubation was optimum for shoot bud induction as longer exposures resulted in hyperhydricity of the explants and shoots induced. We also report preliminary evidence of Agrobacterium tumefaciens EHA105-mediated gene transfer transiently expressing the green fluorescent protein in this species. Transformation studies exhibited amenability of various explant tissues, internode being the most receptive. As the plant has medicinal value, research was carried out to evaluate its potential antioxidant capacity and the efficacy of methanolic leaf extracts in curbing the viability of human colorectal cancer cell line HCT116. Comparative total polyphenol and flavonoid content measurement of fresh and air-dried leaf extract revealed that the fresh leaf extracts contain higher total polyphenol and flavonoid content. The HCT 116 cell viability was assessed by colorimetric assay using a 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide, showed a steady growth inhibition after 24 h of incubation. Scanning electron microscopy of leaf surface revealed a high density of glandular and non-glandular trichomes. This research provides a basis for the conservation of this rare plant and future phytochemical screening and clinical research.

↵​Study of Morpho-physiological and Biochemical Traits for Resistance to Yellow Mosaic Virus (YMV) in Blackgram [Vigna mungo (L.) Hepper] Varieties

Background: Blackgram is one of the most important pulse crop in India and it is being affected by a number of insect pests from seedling stage to maturity. Among them whitefly is an important insect pest that transmit the viral disease, yellow mosaic virus (YMV), which is a major disease resulting in severe yield losses accounting for about 70% and infection at early stages may result in complete failure of the crop causing huge loss to the farmers economically. To overcome the losses due to this important disease in blackgram, study of host plant resistance to whiteflies, thereby minimizing the losses due to YMV disease is of great importance. The trichome density plays an important role as a morphological anti-feedant which reduces the pest attack and subsequently lowers the disease incidence and the plants with high trichome density showed less YMV symptom. The morpho-physiological and biochemical traits play an important role in host plant resistance against YMV disease through insect vector resistance and hence, the study was undertaken. Mathods: A field experiment was conducted during rabi 2017-18 and 2018-19 at RARS, Lam, Guntur in a randomized block design with eight blackgram varieties and replicated thrice under receding soil moisture condition. The experiment was conducted using eight blackgram varieties (LBG 787, GBG 1, TBG 104, LBG 884, LBG 806, LBG 808, LBG 623 and LBG 752) obtained from RARS Lam, Guntur and the variety LBG 623 was considered as a susceptible check. The estimation of sugars, phenols, tannins, trichome density and SCMR was done at vegetative and reproductive stages of crop growth. Result: A significant variation was observed among the varieties for all the traits observed at vegetative and reproductive growth stages during both rabi 2017-18 and 2018-19. The total sugar content of the blackgram varieties varied from 25.16 to 49.82 mgg-1 FW; the leaf phenolic content values ranged from 10.26 to 23.55 mg g-1 FW and the tannins content of the dried leaf samples ranged from 0.014 to 0.052 mgg-1 DW. The trichome density of the blackgram varieties varied from 12.91 to 74.59/cm2 of leaf area and the SCMR values ranged from 24.21 to 55.17. Higher seed yield was recorded in the variety LBG 884 followed by GBG1 and the lower seed yield was recorded in the variety LBG 623 during rabi 2017-18 and 2018-19. The YMV resistant varieties showed relatively higher phenolic, tannins content and trichome density and lower total sugar content in the leaf. The total sugar content showed a significant negative correlation with the seed yield. The SCMR value was significantly lower in the susceptible varieties of blackgram with higher disease scores.

Tomato transcriptomic response to Tuta absoluta infestation

BackgroundThe South America pinworm, Tuta absoluta, is a destructive pest of tomato that causes important losses worldwide. Breeding of resistant/tolerant tomato cultivars could be an effective strategy for T. absoluta management but, despite the economic importance of tomato, very limited information is available about its response to this treat. To elucidate the defense mechanisms to herbivore feeding a comparative analysis was performed between a tolerant and susceptible cultivated tomato at both morphological and transcriptome level to highlight constitutive leaf barriers, molecular and biochemical mechanisms to counter the effect of T. absoluta attack.ResultsThe tolerant genotype showed an enhanced constitutive barrier possibly as result of the higher density of trichomes and increased inducible reactions upon mild infestation thanks to the activation/repression of key transcription factors regulating genes involved in cuticle formation and cell wall strength as well as of antinutritive enzymes, and genes involved in the production of chemical toxins and bioactive secondary metabolites.ConclusionsOverall, our findings suggest that tomato resilience to the South America pinworm is achieved by a combined strategy between constitutive and induced defense system. A well-orchestrated modulation of plant transcription regulation could ensure a trade-off between defense needs and fitness costs. Our finding can be further exploited for developing T. absoluta tolerant cultivars, acting as important component of integrated pest management strategy for more sustainable production.

Fine Mapping of Leaf Trichome Density Revealed a 747-kb Region on Chromosome 1 in Cold-Hardy Hybrid Wine Grape Populations.

Segregation for leaf trichome density was observed in a cold-hardy hybrid grape population GE1025 (N = ∼125, MN1264 × MN1246) that was previously used to detect a quantitative trait locus (QTL) underlying foliar phylloxera resistance on chromosome 14. Our hypothesis was that high trichome density was associated with resistance to phylloxera. Existing literature found trichome density QTL on chromosomes 1 and 15 using a hybrid grape population of “Horizon” × Illinois 547-1 and suggested a few candidate genes. To validate the reported QTL and our hypothesis, interval mapping was conducted in GE1025 with previous genotyping-by-sequencing (GBS) single nucleotide polymorphism (SNP) genotype data and phenotypic scores collected using a 0–6 trichome density scale at several leaf positions. Evaluations were done on replicated forced dormant cuttings in 2 years and on field-grown leaves in 1 year. There was no strong relationship between trichome density and phylloxera resistance except for a Pearson’s correlation (r) of about -0.2 between a few trichome density traits and phylloxera severity traits at 2 and 3 weeks after infestation. Two genetic regions were repeatedly detected for multiple trichome density traits: from 10 to 20.7 Mbp (∼10 Mbp) on chromosome 1 for ribbon and simple density traits and from 2.4 to 8.9 Mbp on chromosome 10 for ribbon density traits, explaining 12.1–48.2 and 12.6–27.5% of phenotypic variation, respectively. To fine map, we genotyped a larger population, GE1783 (N = ∼1,023, MN1264 × MN1246), with conserved rhAmpSeq haplotype markers across multiple Vitis species and phenotyped 233 selected potential recombinants. Evaluations were conducted on field-grown leaves in a single year. The QTL for ribbon trichome density on adaxial vein and adaxial leaf and simple density on abaxial vein was fine mapped to 12.63–13.38 Mbp (747 kb) on chromosome 1. We found variations of MN1264 and MN1246 at candidate genes NAC transcription factor 29, EF-hand protein, and MYB140 in this region and three other surrounding candidate genes proposed previously. Even though no strong relationship between foliar phylloxera resistance and trichome density was found, this study validated and fine mapped a major QTL for trichome density using a cold-hardy hybrid grape population and shed light on a few candidate genes that have implications for different breeding programs.

Resistance and tolerance of ten carrot cultivars to the hawthorn-carrot aphid, Dysaphis crataegi Kalt., in Poland.

Damage caused to cultivated carrots by the hawthorn-carrot aphid, Dysaphis crataegi Kalt. (Hemiptera: Aphididae) is one of the factors limiting carrot production in Poland. Planting resistant and tolerant cultivars could reduce yield losses due to the damage caused by this pest. This study was conducted to evaluate the resistance and/or tolerance of 10 carrot genotypes to hawthorn-carrot aphid. Their field resistance was determined under field conditions based on five indicators, namely, mean number of alates (migrants) per plant and mean percentage of plants colonized by them, mean seasonal number of aphids per plant, mean number of aphids per plant and mean percentage of infested plants at peak abundance. Antibiosis experiments were conducted under laboratory conditions and pre-reproductive, reproductive time, fertility, and demographic parameters, represented by the net reproduction rate (Ro), intrinsic rate of increase (rm) and mean generation time (T), were calculated. Five cultivars, Afro F1, Nipomo F1, Samba F1, White Satin F1, and Yellowstone showed field resistance. Antibiosis experiments revealed significant differences among the carrot cultivars in the length of the reproductive period, female fecundity in the time equal to the pre-reproduction time, and total progeny of hawthorn-carrot aphid. The intrinsic rate of natural increase (rm) for apterous aphids varied significantly, ranging between 0.181 (Nipomo F1) and 0.343 females/female/day (White Satin F1). Additionally, the estimated net reproductive rate (R0) was the lowest on Nipomo F1, and this genotype was determined to be resistant. Our results suggest that a very high density of trichomes on the leaf petioles (71.94 trichomes/cm2) could adversely affect the feeding, bionomy, and demographic parameters of hawthorn-carrot aphid on the cultivar Nipomo F1. In addition, Napa F1 and Kongo F1 demonstrated high tolerance. Considering all the results collectively, four genotypes, Afro F1, Kongo F1, Napa F1 and Nipomo F1, were relatively resistant/tolerant to the hawthorn-carrot aphid.

Morpho-physiological and Biochemical Variability in Greengram [Vigna radiata (L.) Wilczek] Varieties for Mungbean Yellow Mosaic Virus (MYMV) Resistance under Natural Field Conditions

Background: Mungbean yellow mosaic virus (MYMV) is economically most important disease of greengram reducing grain yields by 20-70%. Whiteflies and thrips are the most important insect pests which transmit the viral diseases MYMV and LCV respectively. The host plant resistance to MYMV disease in greengram genotypes has a great importance. The morpho-physiological and biochemical traits play an important role in host plant resistance against MYMV disease through insect vector resistance.Methods: A field experiment was conducted during rabi 2017-18 and 2018-19 at RARS Lam Guntur in a randomized block design with eight greengram genotypes and replicated thrice under receding soil moisture condition. The experiment was conducted using eight greengram varieties (WGG 42, Pusa Vishal, LGG 607, LGG 630, LGG 601, LGG 610, LGG 460 and LGG 450) obtained from RARS Lam Guntur and the genotype LGG 450 was considered as a susceptible check. The estimation of sugars, phenols, tannins, trichome density and SCMR was done at vegetative and reproductive stages of crop growth.Result: A significant variation was observed among the varieties for all the traits observed at vegetative and reproductive growth stages during both rabi 2017-18 and 2018-19. The total sugar content of the greengram varieties varied from 25.55 to 47.32 mgg-1 FW; the leaf phenolic content values ranged from 12.09 to 26.83 mg g-1 FW and the tannins content of the dried leaf samples ranged from 0.020 to 0.055 mgg-1 DW. The Trichome density of the greengram varieties varied from 75 to 162/cm2 of leaf area and the SCMR values ranged from 35.12 to 58.67. Higher seed yield was recorded in the variety LGG 630 followed by WGG 42 and the lower seed yield was recorded in the variety LGG 450 during rabi 2017-18 and 2018-19. The MYMV resistant varieties showed relatively higher phenolic, tannins content and trichome density and lower total sugar content in the leaf. The total sugar content showed a significant negative correlation with the seed yield. The SCMR value was significantly lower in the susceptible varieties of greengram with higher disease scores.

Individual effects of trichomes and leaf morphology on PM2.5 dry deposition velocity: A variable-control approach using species from the same family or genus

Abstract Urban green infrastructure is closely linked to the alleviation of pollution from atmospheric particulate matter. Although particle deposition has been shown to depend on leaf characteristics, the findings from earlier studies are sometimes ambiguous due to the lack of controlling variables. In this study, we investigated the impact of leaf morphological characteristics on PM2.5 dry deposition velocity by employing a control-variable approach. We focused on four indices: trichome density, petiole length, aspect ratio (width-to-length ratio), and fractal deviation. For each index, tree species were chosen from the same family or genus to minimize the influence of other factors and make a group of treatments for an individual index. The dry deposition velocities of PM2.5 were determined through application of an indirect method. The results revealed that the presence of leaf trichomes had a positive effect on PM2.5 dry deposition velocity, and a higher trichome density also led to a greater particle deposition velocity. Lower leaf aspect ratio, shorter petioles, and higher leaf fractal deviation were associated with greater PM2.5 dry deposition velocity. The control-variable approach allows to investigate the correlation between deposition velocity and a certain leaf characteristic independently while minimizing the effects of others. Thus, our study can clarify how a single leaf characteristic affects particle deposition velocity, and expound its potential mechanism more scientifically than the published studies. Our research points out the importance of controlling variables, and also provides ideas for future researches on related factors to be found. Meanwhile the results would help provide insight into design improvements or adaptive management for the alleviation of air pollution.