Trichome Density Research Articles

Exogenous application of stress-related signaling molecules affect growth and cannabinoid accumulation in medical cannabis (Cannabis sativa L.).

Medical cannabis (Cannabis sativa L.) is a source of bioactive phytochemicals with promising pharmacological and therapeutic applications. Enhancing the accumulation of valuable bioactive compounds is potentially a way of increasing the economic importance of this crop. Signaling molecules like salicylic acid (SA), jasmonic acid (JA), and γ-aminobutyric acid (GABA) are involved in the regulation of plant development and responses to biotic and abiotic stresses. Moreover, several phytohormones regulate plant trichome formation and elicit the synthesis of secondary metabolites in many plant species in both in vitro and in vivo systems. Therefore, exogenously delivered plant signaling molecules have the potential to modify the chemical profiles of medical cannabis. In this study, we found that the foliar application of SA, methyl jasmonate (MeJA), and GABA produces changes in the accumulation of the two major cannabinoids, cannabidiolic acid (CBDA) and Δ9- tetrahydrocannabinolic acid (THCA), in leaves and inflorescences of a medical cannabis variety. MeJA at 0.1 mM increased the CBDA content in inflorescences by 15.6%, while SA and MeJA at 0.1 mM increased CBDA and THCA accumulation in leaves by up to 57.3%. Treatments did not change the expression of genes participating in the final steps of the biosynthetic pathway of cannabinoids: olivetolic acid cyclase (CsOAC-1 and CsOAC-2), 2-acylphloroglucinol 4-prenyltransferase (CsPT4), cannabidiolic acid synthase (CsCBDAS), and tetrahydrocannabinolic acid synthase (CsTHCAS). Trichome density was not significantly different from the control plants in any treatment. Besides, we found strong correlations between several plant growth parameters and cannabinoid yields, showing a direct link between plant fitness and the production of cannabinoids.

Characterization of Solanum sp. Lycopersicon section for density and types of leaf trichomes and resistance to whitefly and tomato pinworm

Resistance genes to pests such as Bemisia tabaci and Tuta absoluta can be abundant in wild tomato genotypes. For breeding program initiatives, the characterization of the germplasm in terms of resistance to pests and related morphoanatomical characteristics is essential. Thus, the objective of this study was to evaluate the resistance of different accessions of species of Solanum sp., section Lycopersicon to B. tabaci and T. absoluta and establish a relationship with the types of trichomes present on the leaf surface. Whitefly oviposition, nymphs, and exuviae were investigated in 35 genotypes. On the leaf surface of the genotypes, glandular and non-glandular trichomes were identified and quantified. Based on the results, the genotypes were chosen for pinworm testing. Thirteen tomato genotypes were investigated, including Solanum lycopersicum var. cerasiforme, two accessions of S. lycopersicum, and ten wild accessions of Solanum sp., section Lycopersicon. At 7, 14, 21, and 28 days after infestation, eggs were counted on the abaxial surface of the leaflets, and the extent of damage caused by the tomato leafminer was determined using multivariate analysis and the area under the attack severity progress curve. Leaf trichomes of the 13 pre-selected genotypes were identified and quantified. The findings for the whitefly showed that wild genotypes were more resistant than the commercial ones due to the presence of trichomes, mainly glandular trichomes. According to principal component analysis, stronger materials in whitefly tests correlated more with the number of glandular trichomes. Finally, glandular trichomes positively correlate with the genotype's defense against pests. Solanum pennellii LA-716 and S. habrochaites var. hirsutum PI-127826 were the genotypes with the lowest number of oviposition and damage caused by the moth. This trait was also related to the higher density of glandular trichomes. The results show variability among accessions of the same species for trichome density and pest resistance. This information allows the choice of the best accessions among the species when defining the parents to be used in initial crosses of breeding programs.

Streamlining Agroecological Management of Invasive Plant Species: The Case of Solanum elaeagnifolium Cav

The increased demand for the adoption of sustainable practices to protect agroecosystems is challenged by the introduction and dominance of invasive plant species (IPS). The management of IPS requires a direct response from farmers and policy makers and is often associated with the adoption of practices that have negative ecological impacts. Solanum elaeagnifolium Cav. (silverleaf nightshade) is a noxious IPS posing a serious threat to agriculture and the environment. The increased resistance to the biotic and abiotic stress factors caused by high phenotypic plasticity, dense trichomes, and spines allow the weed to adapt to many habitats, rendering several herbicides ineffective. If an early detection and eradication fails, multiple management strategies should be adopted to mitigate a further dispersal. Herbicides should be applied before or during flowering to prevent the formation of berries and the production of seeds. Precision agriculture tools, such as decision support systems, can be exploited to reduce the herbicide input. Soil tillage should be avoided to prevent clonal reproduction. Mowing is an effective tool to prevent the setting of seeds. Biological agents should be carefully released as a part of an agroecological weed management framework. Future research should focus on the development of cross-boundary protocols and actions to monitor the introduction pathways for the early detection and agroecological management of S. elaeagnifolium.

Morphological traits of wheat (Triticum aestivum L.) associated with resistance to shoot fly, Atherigona approximata Malloch

• Shoot fly caused 26 % of crop damage in wheat. • UAS BW-12417 and UAS BW-11110 genotypes recorded least oviposition and dead heart. • Correlation between crop damage and biophysical factors was significant. • All the biophysical parameters are independent and affect the crop damage in wheat. Shoot flies ( Atherigona spp.) are the members of muscidae family which have got economic importance as pest of several crops of Gramineae family mostly cereals and millets. One of the most effective management strategies for controlling shoot fly is the use of resistant wheat cultivars carrying specific resistant traits. Among thirty wheat genotypes screened at the University of Agricultural Sciences, Dharwad-Karnataka (India), two advanced germplasms UAS BW-12417 and UAS BW-11110 recorded least oviposition and dead heart due to shoot fly and found to be less preferred by Atherigona approximata Malloch. The morphological traits of different wheat genotypes revealed a significant negative correlation of shoot fly oviposition and dead heart with leaf length, leaf length to breadth ratio, seedling height, average seedling growth rate, seedling vigour, leaf glossiness and trichome density of wheat leaves, which indicated the enhanced shoot fly infestation as decrease in the values of above-mentioned morphological traits. Meanwhile, increase in leaf breadth and leaf area of wheat genotype aggrandised the oviposition and dead heart damage by shoot fly. Under the changing climate where, the minor insect pests attaining major pest status, the present investigation would pave way for breeders to tailor future breeding programmes to evolve shoot fly resistant hybrids with high yielding traits.

Variation in leaf characters and agronomical traits of Yard-long bean genotypes between Dimocarpus longan and Psidium guajava stand

Abstract. Putra FP, Kusmiyati F, Anwar S, Widaryati, Sas MGA. 2022. Variation in leaf characters and agronomical traits of Yard-long bean genotypes between Dimocarpus longan and Psidium guajava stand. Biodiversitas 23: 5752-5758. Yard-long bean (Vigna unguiculata subs. sesquipedalis) is one of the most familiar horticulture crops. Leaf characteristics such as trichomes, stomata, and chlorophyll content correlated to other traits that influenced tolerance under sub-optimum conditions and component production traits. This study aimed to evaluate the leaf characters and agronomical traits variations of the Yard-long bean genotypes. The study was conducted by Split-plot design, with the primary factor were shading between Psidium guajava and Dimocarpus longan Lour. stand. The sub-plot was seven genotypes of Yard-long beans. Analyses were performed of multiple components, including the density of trichome, density of stomata, chlorophylls, carotenoids, nitrate reductase activity, flowering times, harvesting times, and production components under shading conditions between D. longan and P. guajava stands. The density of trichome, density of stomata, total chlorophyll, carotenoid, and Nitrate reductase activity showed the variability responses for each genotype in different shading conditions. One genotype showed early flowering in shaded conditions between D. longan than in shaded conditions between P. guajava. Two genotypes have the potential to adapt under shade conditions between D. longan. The morpho-agronomic characters that have been characterized may be used as potential donors for future hybridization programs to develop superior yard-long bean varieties.

Responses of Bunias orientalis to Short-term Fungal Infection and Insect Herbivory are Independent of Nutrient Supply

Plants have to allocate their resources in both growth and defense under different environmental challenges. Several plant species have become invasive particularly in disturbed fertile habitats, which may influence their resource allocation. We studied the effects of nitrate fertilization (low versus high) on various plant responses towards a pathogenic fungus, Alternaria brassicae, and a herbivorous insect species, Mamestra brassicae, in a population of Bunias orientalis, which is invasive in parts of central Europe. Aboveground biomass and leaf trichome density were enhanced in plants under high fertilization. In contrast, the short-term fungal infection and herbivory had no effect on aboveground biomass. Leaf water, nitrogen content and glucosinolate concentrations were neither affected by fertilization nor in response to antagonist attack. The total soluble sugar content, especially fructose, as well as leaf peroxidase activity increased significantly in leaves upon fungal infection, but independent of fertilization. Larval biomass gain and herbivore survival were likewise unaffected by fertilization. Our findings highlight that under conditions of high fertilization, B. orientalis plants allocate more resources into growth and morphological defenses than chemical defenses. In contrast, induced responses to short-term antagonist attack seem independent of nitrate availability in this population.

Registration of Arkot 1005, Arkot 1015, and Arkot 1019 cotton germplasm lines

AbstractArkot 1005 (Reg. no. GP‐1127, PI 700852), Arkot 1015 (Reg. no. GP‐1128, PI 700853), and Arkot 1019 (Reg. no. GP‐1129, PI 700854) are conventional cotton (Gossypium hirsutum L.) germplasm lines released by the Arkansas Agricultural Experiment Station in April 2022. The lines were compared with UA48 and UA222 (check cultivars) in replicated field tests at four Arkansas sites over 5 yr. Over these tests, lint yields of the three lines did not differ from each other and were greater than UA48. Lint yield of Arkot 1015 was greater than UA222, while lint yields of Arkot 1005 and Arkot 1019 were equal to UA222. Performance in regional tests indicates that the lines have wide adaptation. The lint yields of Arkot 1015 and Arkot 1019 were attributed to producing more (and smaller) seed per area and less lint per seed (lint index) than UA222. Arkot 1005 produced higher lint index than the other two lines and the two check cultivars. Seed per area for Arkot 1005 was higher than UA48, equal to UA222, and lower than Arkot 1015 and Arkot 1019. Leaf pubescence, stem pubescence, and bract trichome density of the three lines were intermediate between UA222 and UA48. All three lines displayed high resistance to bacterial blight and were similar to UA222 and UA48 in their response to other diseases. Arkot 1015 was more resistant to tarnished plant bug (TPB) than Arkot 1005, Arkot 1019, and UA48, but all were more susceptible to TPB than UA222. Compared with the other lines and check cultivars, Arkot 1005 and Arkot 1019 displayed higher and lower, respectively, resistance to seed deterioration. Fiber quality of Arkot 1019 was superior to UA48, UA222, and the other lines. Fiber quality of Arkot 1005 and Arkot 1015 was superior to UA222.

Does Domestication Affect Structural and Functional Leaf Epidermal Traits? A Comparison between Wild and Cultivated Mexican Chili Peppers (Capsicum annuum).

During domestication, lineages diverge phenotypically and genetically from wild relatives, particularly in preferred traits. In addition to evolutionary divergence in selected traits, other fitness-related traits that are unselected may change in concert. For instance, the selection of chili pepper fruits was not intended to change the structure and function of the leaf epidermis. Leaf stomata and trichome densities play a prominent role in regulating stomatal conductance and resistance to herbivores. Here, we assessed whether domestication affected leaf epidermis structure and function in Capsicum annuum. To do this, we compared leaf stomata and trichome densities in six cultivated varieties of Mexican Capsicum annuum and their wild relative. We measured stomatal conductance and resistance to herbivores. Resistance to (defense against) herbivores was measured as variation in the herbivory rate and larvae mortality of Spodoptera frugiperda fed with leaves of wild and cultivated plants. As expected, the different varieties displayed low divergence in stomatal density and conductance. Leaf trichome density was higher in the wild relative, but variation was not correlated with the herbivory rate. In contrast, a higher mortality rate of S. frugiperda larvae was recorded when fed with the wild relative and two varieties than larvae fed with four other varieties. Overall, although domestication did not aim at resistance to herbivores, this evolutionary process produced concerted changes in defensive traits.

Natural genetic variation in the HAIRS ABSENT (H) gene increases type-VI glandular trichomes in both wild and domesticated tomatoes

Glandular trichomes produce and exude secondary metabolites, conferring insect resistance in many crop species. Whereas some of its wild relatives are insect-resistant, tomato (Solanum lycopersicum) is not. Identifying the genetic changes that altered trichome development and biochemistry during tomato domestication would contribute to breeding for insect resistance. A mutation in the HAIRS ABSENT (H) gene, which encodes a C2H2 zinc finger protein (ZFP8), leads to reduced trichome density. Several geographic accessions of S. pimpinellifolium, the wild ancestor of domesticated tomato, have glabrous organs that resemble the phenotype caused by h. Here, we investigated allelic diversity for H in tomato and S. pimpinellifolium accessions and their associated trichome phenotypes. We also evaluated how the developmental stage can affect trichome development in glabrous and non-glabrous plants. We found that glabrous accessions of S. pimpinellifolium have different ZFP8 nucleotide sequence changes, associated with altered trichome development and density. We also found that while the glabrous appearance of h mutants is caused by a lower density of long trichomes, the density of type-VI glandular trichomes is increased, particularly in the adult stages of plant development. These insights on the genetic control of trichome development may contribute to breeding for insect resistance in tomatoes and other crops.

Paclobutrazol Improves The Agronomic Performance and Micromorphological Profile of Five Local Black Rice ( Oryza sativa L.) Varieties in Central Java Indonesia

Local black rice (Oryza sativa L.) is one of the biodiversity of rice in Indonesia, which has tall stature and long cultivation period, easy to lodge, and requires more intensive care. Paclobutrazol (PBZ) is a plant growth inhibitor compound that could reduce plant height and accelerate plants entering the generative phase. This study aimed to determine the effects of PBZ concentration on the agronomic character and micromorphological profile of five local black rice varieties. This research was conducted experimentally using a completely randomized factorial design. The first factor was the local black rice variety (Brebes, Klaten, Magelang, Pati, and Pekalongan ), while the second was PBZ concentration (0, 100, 200, and 300 ppm) with three replications. PBZ spraying was conducted in the fourth week after planting. The data obtained were analyzed using ANOVA and HSD test (α=5%). The results showed that the concentrations of PBZ 300 ppm produced the heaviest 100 grains. The Klaten variety had wide abaxial stomata, the Magelang variety had high abaxial stomata density, while the Pati variety had long abaxial stomata and heaviest 100 grains. The interaction between Brebes variety and PBZ 0 ppm produced high adaxial stomatal density, Klaten variety, and PBZ 100 ppm have vast adaxial stomatal and high abaxial trichome density. Pati variety and PBZ 0 ppm had the most tillers, while Pati variety and PBZ 100 ppm had long adaxial stomata and the most grains per panicle. The study's critical findings are that PBZ gives different micromorphology improvements and increases agronomic performance in local black rice.

Composition and abundance level of pest mites in jasmine gambier (Jasminum officinale) plantation of Purbalingga, Central Java, Indonesia affected by some abiotic factors

Abstract. Budianto BH, Sasongko ND. 2022. Composition and abundance level of pest mites in jasmine gambier (Jasminum officinale) plantation of Purbalingga, Central Java, Indonesia affected by some abiotic factors. Biodiversitas 23: 5227-5232. The decline in productivity of gambier jasmine flowers is not only caused by the reduction of gambier jasmine land area but also insect, caterpillar and pest mite attacks. Types of pest mites and their population dynamics are closely related to abiotic factor conditions such as temperature, humidity, rainfall, season, an abundance of predatory mites and types of plant cultivars. The study aimed to determine the types of pest mites and some abiotic factors that affect their abundance in gambier jasmine plants. The research method was a survey with a purposive sampling technique. Sampling locations were in Cipawon village, Bukateja sub-district, Purbalingga district, and Central Java Province, Indonesia. The obtained data were analyzed by analysis of variance at an error rate of 0.05. The types of pest mites that were identified consisted of 8 species, namely Brevipalpus phoenicis, B. californicus, B. papayensis, B. obovatus, Tetranychus urticae, T. kanzawai, T. cinnabarinus and Tyrophagus putrescentiae. The type of pest mite always found at each sampling point was B. phoenicis, with an abundance range of 0.027 to 0.067. The results of the analysis of the variance of pest mite abundance in gambier jasmine plantations showed that abundance of individuals between pest mite species did not significantly differ at all sampling points. Based on multivariate analysis, it was noted that trichome density had the most influence on pest mite abundance with a population model of Y = 0.399 + 0.043a + 0.012b.

Cloning of StHD1 and StHD8 from Schizonepeta tenuifolia and function of regulating glandular trichome development

Hd-Zip, a unique transcription factor in plant kingdom, influences the growth, development, and secondary metabolism of plants. Hd-zip Ⅳ is thought to play an important role in trichome development of Schizonepeta tenuifolia. This study aims to explore the functions of StHD1 and StHD8 in Hd-zip Ⅳ subfamily in peltate glandular trichome development. To be specific, the expression patterns of the two genes and interaction between the proteins encoded by them were analyzed based on transcriptome sequencing and two-hybrid screening. The subcellular localization was performed and functions of the genes were verified in tobacco and S. tenuifolia. The results showed that StHD1 and StHD8 had high similarity to HD-Zip Ⅳ proteins of other plants and they all had the characteristic conserved domains of HD-Zip Ⅳ subfamily. They were located in the nucleus. The two genes mainly expressed in young tissues and spikes, and StHD1 and StHD8 proteins interacted with each other. The density and length of glandular trichomes increased significantly in tobacco plants with the overexpression of StHD1 and StHD8. Inhibiting the expression of StHD1 and StHD8 by VIGS(virus-induced gene silencing) in S. tenuifolia resulted in the reduction in the density of peltate glandular trichomes, the expression of key genes related to mono-terpene synthesis, and the relative content of limonene and pulegone, the main components of monoterpene. These results suggested that StHD1 and StHD8 of S. tenuifolia formed a complex to regulate glandular trichomes and affect the biosynthesis of monoterpenes.

Physiological and chemical changes induced by transparent polythene + green net shed on Pelargonium graveolens L. mother plants during monsoon season

Pelargonium graveolens L. or rose scented geranium is an essential oil-bearing plant with extended economic value. It has strong pharmacological and aromatic properties along with its frequent application in perfumery, food, cosmetics, and pharma industries. Seasonal fluctuations in northern India have a detrimental effect on the survival of P. graveolens. Due to its male sterility, the plant is unable to propagate by sexual reproduction, so, vegetative propagation is the only option to grow and protect the mother plant for the next season. To protect the plant in adverse conditions our researchers had developed a protective shed i.e. transparent polythene + green net shed (S) but the reason for the increased survival and growth of the plant in the shed was not well understood. In the present research, approximately 91% of P. graveolens mother plants were protected under the shed compared to open conditions (O). The current study also reported high humidity, increased air temperature and increased microbial infection in open condition, exerting various physiological and chemical changes which further have detrimental effects on plant growth and survival. In shed conditions, a decreased level of antioxidant enzymes, antioxidant metabolites, and elevated level of photosynthetic pigments were observed. Further, an increased density of glandular and non-glandular trichomes and an improved quality and quantity of essential oil were observed in shed conditions. Considering the above observations, polythene + green net shed can be used as an auspicious approach for protecting the P. graveolens mother plant in monsoon season due to its effect on soil moisture, soil microbial biomass carbon (SMBC), trichome morphology/density and yield of essential oil.

The foliar trichomes of Combretum apiculatum subsp. apiculatum (Combretaceae): Morphoanatomy and histochemistry

Combretum apiculatum Sond. subsp. apiculatum is an important plant used in the traditional medicinal treatment of many diseases including gastrointestinal disorders, conjunctivitis, aches and leprosy. The plant's medicinal properties are putatively associated with secondary metabolites present in trichomes found on the leaf surfaces. This study aimed to investigate the distribution and morphology of the glandular trichomes of C. apiculatum at various stages of leaf development (emergent, young and mature) using stereo-, compound-light- and scanning electron microscopy, as well as to determine the leaf phytochemical constituents and to correlate the plant's medicinal properties at the cellular level by histochemical analyses. The microscopical studies revealed multicellular subsessile/sessile peltate, glandular trichomes and unicellular to multicellular non-glandular trichomes at all leaf developmental stages. Emergent leaves consisted of dense distributions of trichomes located in epidermal depressions, suggesting emergence during the early stages of leaf development. Trichome density decreased with leaf maturation, potentially attributable to the leaf expansion theory. Histochemical analyses on the leaves and trichomes detected alkaloids, phenolic compounds, lignin, terpenoids, resin acids, pectins, mucilage, carboxylated and hydroxylated polysaccharides, polyphenols, total lipids, total proteins and nucleic acids, indicating cell viability. These compounds possess medicinal properties, thereby providing supporting evidence for the plant's traditional medical use.

Helicoverpa armigera preference and performance on three cultivars of short-duration pigeonpea (Cajanus cajan): the importance of whole plant assays.

Helicoverpa armigera is a major pest of pigeonpea (Cajanus cajan). Efforts to develop pigeonpea varieties resistant to H. armigera attack have been met with limited success, despite reports of high levels of resistance to H. armigera in wild relatives of pigeonpea and reports of low to moderate levels of resistance in cultivated varieties. Here we examined H. armigera oviposition preference and larval performance on whole plants of three cultivars of short-duration pigeonpea: a susceptible control (ICPL 87) and two cultivars with purported host-plant resistance (ICPL 86012 and ICPL 88039). In our no-choice oviposition experiment, H. armigera laid similar numbers of eggs on all three cultivars tested, but under choice conditions moths laid slightly more eggs on ICPL 88039. Larval growth and development were affected by cultivar, and larvae grew to the largest size (weight) and developed fastest on ICPL 86012. Moths laid most of their eggs on floral structures, sites where subsequent early instar larvae overwhelmingly fed. Experimentally placing neonate larvae at different locations on plants demonstrated that larvae placed on flowers experienced greater survival, faster development, and greater weight gain than those placed on leaves. The type and density of trichomes (a potential resistance trait) differed among cultivars and plant structures, but larvae selected to feed at sites where trichomes were absent. Future work examining host-plant resistance against H. armigera should incorporate the behavioural preference of moths and larvae in experiments using whole plants as opposed to bioassays of excised plant parts in Petri dishes. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The Molecular, Morphological and Genetic Characterization of Glyphosate Resistance in Conyza bonariensis from South Africa.

Six Conyza bonariensis (L.) Cronquist populations were screened in a pot experiment at the University of Pretoria's Hatfield experimental farm to evaluate and confirm the degree of glyphosate response. Resistance factors ranged from 2.7- to 24.8-fold compared to the most susceptible biotype. Partial sequencing of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene found no mutation at the Thr102, Ala103 or Pro106 positions. EPSPS mRNA expression levels in glyphosate-resistant biotypes (Swellendam and Piketberg seed sampling sites) were comparable or lower than those in susceptible biotypes (George and Fauresmith sites). Additionally, the highest expression level was reported in the susceptible Fauresmith biotype. These results indicate that glyphosate resistance in the tested resistant biotypes is not caused by target-site mutations and EPSPS gene amplification. Leaf surface characteristics can influence the spread and subsequent absorption of glyphosate. The study established non-significant results in the amount of leaf wax and insufficient mean separations in cuticle thickness and trichome density data. Therefore, the observed differences in response of biotypes to glyphosate treatment could not be attributed conclusively to differences in the leaf morphological characteristics investigated. Results from the inheritance study were consistent with glyphosate resistance being inherited in an incompletely dominant manner when plants were treated with glyphosate herbicide at 900 g ae ha-1.

Screening of advanced sugarcane genotypes against rust mite

In the screening trial, among the nineteen sugarcane genotypes screened for the reaction to sugarcane rust mite, Abacarus sacchari, only 2 genotypes (009-64 and 0961-07) harboured >1 mites /2 cm2 leaf area while remaining all the genotypes harboured <2 mites/2 cm2 leaf area for the entire crop duration. Morphological characters of genotypes revealed that interveinal distance, leaf area and trichome density were found to influence the A. sacchari negatively. The genotype with high phenol and lower amount of total sugar, reducing sugar, crude protein was found with the lower level of incidence of mites. The study on the role of leaf nutrient on the mite population revealed that genotype with higher potassium content and lower nitrogen levels were found with the minimum incidence of A. sacchari.

Phenotyping Olive Cultivars for Drought Tolerance Using Leaf Macro-Characteristics

This work investigates the relationships between leaf traits and olive response to water stress through two complementary field experiments in order to screen genotypes for drought tolerance. The first experiment consisted of the phenotyping of 32 olive varieties for 11 leaf morpho-physiological traits during a fruit set phase under well-watered conditions. In the second experiment, the yield and vegetative responses of five representative varieties to the withholding of irrigation during the whole fruit growth period were assessed to identify leaf traits that are associated with olive resilience plasticity and that could be used as drought tolerance markers. The results highlighted large phenotypic variability for leaf area (LA, 2.9–9.5 cm2), petiole elasticity (8.0–36.0°), water loss in detached leaves (WLDL, 3.6–11.6%), stomatal density (222.6–470.1 no mm−2), stomatal length (11.4–18.7 µm), trichome density (120.5–204.4 no mm−2), trichome width (103.6–183.4 µm), leaf contents in cuticular wax (CWC, 44.7–606.2 µg cm−2), and soluble sugars (SSC, 15.8–536.9 mg gdw−1). Among these leaf traits, WLDL displayed a significant correlation with the yield stability index (r = −0.973) and water use efficiency (r = −0.939), suggesting its use as relevant drought tolerance phenotypic marker. Likewise, LA, SSC, and CWC were singled out as second-level drought tolerance markers, being strongly correlated with stability of leaf size and leafing intensity in response to water stress. Cluster analysis highlighted 12 distinct levels of drought tolerance within the studied olive collection. Based on the four identified phenotypic markers, “Lechin de Sevilla” alongside “Picholine Marocaine” were found to be the most drought-tolerant varieties, while Frantoio was the most sensitive. This study provides the first, unprecedented, insights into the usefulness of leaf phenotyping in olive drought tolerance screening, with a focus on structural and functional leaf traits.

Structural Disparity of Avocado Rootstocks In Vitro for Rooting and Acclimation Success

Improving clonal rootstock propagation of avocado has been a major industry/research challenge globally for many decades. Tissue culture has been a focus for clonal propagation with substantial advancements in recent years. In the process of tissue culture, avocado rootstocks display differences in rooting and acclimation capacity. Such differences may relate to the specific structural characteristics of the rootstock. This study aimed to investigate the structural difference during tissue culture in two rootstocks ‘Reed’ and ‘Velvick’, with differing rooting and acclimation capacity. Histological investigations were carried out of stem vasculature, leaves and roots of tissue cultured plantlets. Quantitative parameters; stomatal index, stomatal density, trichome density, vein-islet density and vein termination density were also analysed. Prominent fascicular cambium and fewer phloem fibres in stems positively correlated with rooting capacity. Acclimation success positively correlated to the presence of fully differentiated secondary xylem in root. Presence of smaller epidermal cells, high stomatal density and reduced vein termination density was associated with reduced acclimation success. These findings will support optimisation strategies for micropropagation of not only difficult-to-root and difficult-to-acclimate avocado rootstocks, but also, other woody perennials experiencing similar problems.

Effect of Organic Matter Fertilizers on the Composition of Volatiles, Morphometrical and Anatomical Parameters of Essential Oil-Bearing Thymus × citriodorus Cultivated in an Open Field Conditions

Thymus × citriodorus (Lamiaceae) is medicinal, essential oil-bearing hybrid, synthesizing significant amounts of geraniol. This hybrid is suitable for cultivation in an open ground in the Baltic region; therefore, increasing the yield and amounts of bioactive compounds by organic matter fertilization during organic farming is realized. The aim of the present study was to evaluate the effect of fertilization with liquid cattle dung and humus on the quantitative and qualitative composition of essential oils as well as on biomass for some morphometrical and anatomical parameters of Thymus × citriodorus that were grown in open ground for two years. Each fertilization treatment was carried out on four replications, and four separate experimental plots were used as control plots. For anatomical investigations, the impress method and light microscopy were used. The essential oils were isolated by hydrodistillation and analyzed by GC-FID and GC-MS. The results showed somewhat different effects of liquid cattle dung and humus on the investigated parameters of hybrid in the first (warmer and drier) and second (rainier and cooler) experimental years. Liquid cattle dung had positive effects on biomass, height and the area covered by plants and on the number and length of inflorescences as well as on the density of stomata in the lower epidermis in the first year, but in the second experimental year, effects were observed on the length of inflorescences only. The effect of humus on the density of glandular trichomes in the upper epidermis of leaves was positive in the first year, but negative in the second experimental year. Moreover, in the second experimental year, humus affected negatively the height of plants and the percentage of the essential oil. The conclusion was that although it is fertilized with the same organic fertilizers, different climatic conditions in different years can influence chemical, anatomical and morphometrical parameters of plants growing in an open ground.