Plantlet Stage Research Articles

Response of a Moroccan Abelmoschus esculentus L. ecotype originated from Tafilalet to salt stress at seed germination and plantlet stages

Response of a Moroccan Abelmoschus esculentus L. ecotype originated from Tafilalet to salt stress at seed germination and plantlet stages

A Global Screening Assay to Select for Maize Phenotypes with a High Tolerance or Resistance to Fusarium verticillioides (Sacc.) Nirenberg Rots

Fusarium verticillioides (Sacc.) Nirenberg (Fv) causes rots in maize around the world and produces mycotoxins that contaminate grains, making this species a significant health concern for both animals and humans. One of the best approaches to address rots is to identify highly tolerant or resistant genotypes that can be used for genetic improvement. The aim of the study was to evaluate dose-response assays to tolerance or resistance for Fv rots throughout the maize life cycle. These tests assessed the effects of Fv during post-germination development and the seedling (V2) stage by seed infection, the plantlet (V4) stage by substrate infection, and in the reproductive phase in maize stalks (R2 stage) and ears (R6 stage) by R1 stage inoculation. In all assays, the doses were effective at distinguishing contrasting phenotypes. Severity, root fresh weight, and aerial length were the most informative parameters at the V2 and V4 stages. Evaluation of the stalk necrosis area between and within the internodes of susceptible genotypes revealed significant differences among doses, and a positive correlation between necrosis and conidia concentration was observed in internodes. Injecting eight million conidia in the ear was sufficient for selecting different phenotypes. A total of 85% of the genotypes conserved their same capacity to respond to Fv infection throughout the maize life cycle, so that screening at the early vegetative stage (e.g., V2) could be useful for distinguishing contrasting phenotypes in the reproductive stage. Implementing these screening assays in a maize breeding program could be valuable for classifying the degrees of resilience of maize germplasms to Fv rots. This global screening has the potential to be employed to select against other Fusarium species.

Histological assessment of regenerating plants at callus, shoot organogenesis and plantlet stages during the in vitro micropropagation of Asparagus cochinchinensis

In this study, we developed a repeatable in vitro micropropagation protocol for the medicinal plant Asparagus cochinchinensis, based on indirect organogenesis using leaf segments cut from seedlings of in vitro-germinated seeds. We obtained 85% callus induction from the leaf segments within 4–5 weeks when grown on Murashige and Skoog (MS) medium supplemented with benzylaminopurine (BAP, 1.0 mg/L) and 1-naphthaleneacetic acid (NAA, 0.5 mg/L). We found that MS media supplemented with Kn (1.0 mg/L) in combination with NAA (1.0 mg/L) and BAP (1.0 mg/L) combined with NAA (0.5 mg/L) were the most effective in promoting shoot regeneration, yielding plantlets with 6.72 and 6.48 shoots per culture, respectively. When cultured on PGR-free half-strength MS medium, regenerated plants developed root systems with an average 11.0 roots per shoot cluster and an average length of 36.14 mm at 9 weeks. During acclimatization, regenerated plantlets showed 96.4% survival and exhibited normal growth characteristics and morphology. We also made an attempt to directly regenerate A. cochinchinensis from shoot apices but it was futile. Histological analyses revealed the presence of crystal idioblasts in young leaves from the early stages of leaf differentiation. The leaf-based plant regeneration technique developed herein could be employed for large-scale propagation of the plants over a short time period, thereby substantially contributing to the germplasm preservation and rapid propagation of A. cochinchinensis. A repeatable in vitro micropropagation protocol for Asparagus cochinchinensis was developed based on indirect organogenesis. Histological analysis revealed crystal idioblasts for the first time in leaf primordia of this species.

Molecular Assisted Selection for Pollination-Constant and Non-Astringent Type without Male Flowers in Spanish Germplasm for Persimmon Breeding

Persimmon (Diospyros kaki Thunb) species is a hexaploid genotype that has a morphologically polygamous gyonodioecious sexual system. D. kaki bears unisexual flowers. The presence of male flowers resulted in the presence of seeds in the varieties. The fruits of persimmon are classified according to their astringency and the pollination events that produced seeds and modify the levels of astringency in the fruit. The presence of seeds in astringent varieties as pollination variant astringent (PVA), pollination variant non-astringent (PVNA) and pollination constant astringent (PCA) resulted in fruits not marketable. Molecular markers that allow selection of the varieties according to the type of flowers at the plantlet stage would allow selection of seedless varieties. In this study, a marker developed in D. lotus by bulk segregant analysis (BSA) and amplified fragment length polymorphism (AFLP) markers, named DlSx-AF4, has been validated in a germplasm collection of persimmon, results obtained agree with the phenotype data. A second important trait in persimmon is the presence of astringency in ripened fruits. Fruits non-astringent at the ripen stage named pollination constant non-astringent (PCNA) are the objective of many breeding programs as they do not need removal of the astringency by a postharvest treatment. Astringency in the hexaploid persimmon is a dominant trait. The presence of at least one astringent allele confers astringency to the fruit. In this paper we checked the marker developed linked to the AST gene. Our goal has been to validate both markers in germplasm from different origins and to test the usefulness in a breeding program.

Yield components in new pear cultivars and breeding forms in the Middle Urals

Sverdlovsk Horticultural Breeding Station specializes in the development of fruit and berry cultivars for the Middle Urals. One of its tasks is pear breeding for high winter-hardiness, high yield, and good fruit quality. Ten new pear cultivars and improved forms of local breeding were selected as the material for this study versus the reference cultivars ‘Talitsa’, ripening in summer, and ‘Berezhenaya’, ripening in late autumn. Observations were conducted across the decade of 2009–2019. The cultivars ‘Letnyaya zolotistaya’, ‘Chusovaya’, ‘Berezhenaya’ (ref.), ‘Sultan’, and breeding form DL-33-307 were found to possess resistance of flowers to late spring frosts. Cvs. ‘Letnyaya zolotistaya’, ‘Berezhenaya’ (ref.) and ‘Sultan’ were early-fruiting; cvs. ‘Talitsa’ (ref.) and ‘Chusovaya’, breeding forms ZS-IV-5-11, DL-33-307, DL-II-31n-207, ZS-II-15-18 and ZS-IV-5-19 were mid-fruiting; breeding form ZS-IV-15-38, late-fruiting. An early onset of full fructification at the age of 10–11 years or more, combined with high yield at the same age, was observed in cvs. ‘Berezhenaya’ (ref.), ‘Sultan’, ‘Letnyaya zolotistaya’, and breeding form ZS-II-15-18. New cultivars ‘Letnyaya zolotistaya’ and ‘Sultan’ were highlighted for a combination of valuable traits: earliness, high yield, and high growth rates in the plantlet stage. Cv. ‘Letnyaya zolotistaya’ had attractive good-tasting fruits, weighing 76 g, ripening in summer. Cv. ‘Sultan’ yielded nicelooking and good-tasting fruits, weighing 129 g, ripening in winter. Cv. ‘Chusovaya’ was identified for its nice-looking fruits with a very good taste.

Identification of Vietnamese Paphiopedilum Species Using Vegetative Morphology

Background: Discrimination of Paphiopedilum species using floral morphology has been used effectively and commonly due to distinct features of their reproductive parts. Most classification references also focus on description of flower morphology and structure. Nevertheless species preservation meets great problems when illegal trading plants are mostly at non-flowered or plantlet stages. Molecular approaches have been applied and obtained highly precise results but spent time and could not rate 100% of resolution over the genus. Thus, quickly identification using only vegetative characteristics would be an efficient support for other distinguishing methods and a remarkable contribution to the detection and prevention of Paphiopedilum ilicit sales.
 Aims: In this research we aimed to describe in details leaf features of Paphiopedilum species in Vietnam serving for quick and easy discriminating species without flower present or laboratory techniques.
 Study Design: Observed variables based on qualitative features of leaf shape, color, vein feature, thickness, toughness and quantitative features of leaf size were saved and organized using Microsoft Excel 2010.
 Place and Duration of Study: Tay Nguyen Institute for Scientific Research, Agricultural Genetics Institute, between November 2018 and November 2019.
 Methodology: We minutely analyzed the leaf morphology of nineteen species and two variants which belongs to Vietnamese Paphiopedilum population in an order manner from parameters that easiest to be realized to the less clearly traits for the most efficient recognition even to the one who is not botanist.
 Results: 16 out of 20 species were identified using leaf morphology. This rate was up to 100% when combining morphological and molecular methods without the present of their flowers. An artificial key to genus Paphiopedilum using the vegetative details was first time established.
 Conclusion: Leaf morphology can be effectively used as the first step for identifying Paphiopedilum species. Our results provided useful tool in severally or in combination with molecular methods in biodiversity and commercial management of these valuable species.

Oil Palm Phytochrome-Interacting Factor4 (PIF4) Gene is Conserved and Highly Expressed During Somatic Embryogenesis

Oil palm is used in food, fuel and cosmetic industries. Tissue culture is the best way to propagate oil palm; unfortunately the somatic embryogenesis during tissue culture takes long time. The molecular mechanism of somatic embryogenesis in oil palm remains unknown. Recent research reported that auxin plays an important role in early and post-embryogenic plant. PHYTOCHROME-INTERACTING FACTOR4 (PIF4) regulates levels of auxin and the expression of key auxin biosynthesis genes. Our research aims to characterize oil palm PIF4 gene. Thus, we cloned EgPIF4, analyzed the domain using bioinformatic and examined the expression of EgPIF4 during somatic embryogenesis at different tissue including callus and somatic embryo stages; globular, torpedo, cotyledon, and plantlet stage using real-time PCR method. The result showed that EgPIF4 gene comprised 1,737 bp with 9 exons, which encode 578 amino acid residuals. It contains a conserved domain called basic helix-loop-helix domain. EgPIF4 has high level of expression at somatic embryogenetic stage specifically globular and torpedo stage suggested that EgPIF4 plays an important role during somatic embryogenesis. The future characterization of EgPIF4 function in oil palm will help to understand somatic embryogenesis process and facilitate the improvement of the oil palm tissue culture.

Oil Palm Phytochrome-Interacting Factor4 (PIF4) Gene is Conserved and Highly Expressed During Somatic Embryogenesis

Oil palm is used in food, fuel and cosmetic industries. Tissue culture is the best way to propagate oil palm; unfortunately the somatic embryogenesis during tissue culture takes long time. The molecular mechanism of somatic embryogenesis in oil palm remains unknown. Recent research reported that auxin plays an important role in early and post-embryogenic plant. PHYTOCHROME-INTERACTING FACTOR4 (PIF4) regulates levels of auxin and the expression of key auxin biosynthesis genes. Our research aims to characterize oil palm PIF4 gene. Thus, we cloned EgPIF4, analyzed the domain using bioinformatic and examined the expression of EgPIF4 during somatic embryogenesis at different tissue including callus and somatic embryo stages; globular, torpedo, cotyledon, and plantlet stage using real-time PCR method. The result showed that EgPIF4 gene comprised 1,737 bp with 9 exons, which encode 578 amino acid residuals. It contains a conserved domain called basic helix-loop-helix domain. EgPIF4 has high level of expression at somatic embryogenetic stage specifically globular and torpedo stage suggested that EgPIF4 plays an important role during somatic embryogenesis. The future characterization of EgPIF4 function in oil palm will help to understand somatic embryogenesis process and facilitate the improvement of the oil palm tissue culture.

Seed osmopriming with PEG solutions in seeds of three infraspecific taxa of Pinus nigra: Impacts on germination, mitosis and nuclear DNA

A phenological characterisation of the Portuguese Pinus nigra stands performed in the 1980s considered them as belonging to subspecies laricio, salzmanni and nigra. Recently, six allochthonous P. nigra populations that represent the actual species distribution in Portugal were molecularly characterised and showed high genetic similarity to subsp. laricio vars. corsicana and calabrica, and genetic distance to subsp. salzmanni. P. nigra has a hard natural regeneration, and this problem will be enhanced under the more severe and frequent drought episodes projected to Europe. In this work, seeds of the P. nigra infraspecific taxa previously assigned to Portugal were osmoprimed with 10% and 20% polyethylene glycol (PEG) solutions to mimic water stress, and to analyse its impacts on germination, mitosis, and nuclear DNA of young needles. Hydroprimed seeds and resulting plantlets were used as controls. The osmotic stress imposed to the seeds delayed the germination in most of the cases, induced cell cycle anomalies, and caused DNA damage in needles. These impacts were more pronounced in subsp. laricio var. corsicana. The detection of osmotic stress effects from germination to the juvenile plantlet stage suggested a stress memory transmission between plant tissues. The 20% PEG osmopriming performed in var. corsicana seeds was lethal. Globally, this preliminary work suggested a differential water stress tolerance among the three P. nigra infraspecific taxa that should be exploited further, and provided probable explanations for their reduced natural regeneration and early mortality of pine seedlings that compromise afforestation/reforestation programs in Portugal and abroad.

Drought tolerance assessment of melon germplasm searching for adaptation to climate change

Shortage of irrigation water at critical melon growth stages can be the most important limiting factor in the future due to climate change, especially in the Mediterranean region. Apart from the improvement of irrigation systems and crop management, the development of drought tolerant cultivars by genetic breeding is the best solution to achieve stable yields. Screening germplasm collections is a prerequisite for that. A melon core collection was evaluated in the current work in two assays. Seven morphological traits were assessed at plantlet stage and compared under drought and standard conditions imposed. Significant differences for all traits were recorded among the sixty accessions evaluated. Clustering analysis also grouped the accessions according to their response to drought, detecting some landraces and wild types of interest, mainly of Indian and African origin, although the best behavior under drought was found in a flexuosus melon from Irak. Some Spanish inodorus landraces also showed better response than the average behavior of commercial types. The employment of this set of traits has allowed screening a large germplasm collection in an easy and non-expensive way, in one of the most sensitive developmental stages. Key words: Cucumis melo germplasm, morphological seedling traits, abiotic stress, response to drought, variability

Water use and photosynthesis of Dendrobium Sonia ‘Earsakul’ under water deficit stress

Dendrobium Sonia ‘Earsakul’ orchids in three developmental stages (plantlet, mature, flowering) were exposed to water deficit stress for 7 d. The average daily evapotranspiration rate (ET) ± SD under the well-watered condition was lowest in the plantlet stage (10.51 ± 1.96 mL/d). The ET of the mature and flowering stages was 45.80 ± 6.90 mL/d and 50.97 ± 7.23 mL/d, respectively. However, the ET was not significantly different between the mature and flowering stages. Under the water-limited condition, the ET values of all stages for the orchid were continuously depleted from the well-watered control at the 2nd day in the plantlet stage and the 3rd day of the mature and flowering stages after withholding water. The CO2 exchange rate (CER) of the water-stressed plant substantially decreased compared to the control due to strong decreases in the stomatal conductance (gs) and the transpiration rate (TR) in all developmental stages. In addition, water deficit stress led to a substantial decline in the water use efficiency (WUE) in the plantlet stage while the WUE of the mature and flowering stages remained similar to the control. However, the water deficit stress induced increased Ci/Ca in the plantlet stage. Moreover, shrinking of the stressed pseudobulb was seen in the plantlet and flowering stages but leaf wilting occurred only in the stressed plant of the plantlet stage. These results demonstrated that water deficit stress led to decreased photosynthesis in Den. Sonia ‘Earsakul’ due to stomatal limitation.

Identification and characterization of glycoproteins during oil palm somatic embryogenesis

The objective of this experiment was to characterize differentially expressed glycoprotein in a somatic embryogenesis process during oil palm tissue culture. Embryogenic callus in the somatic embryo acquisition stages (globular, torpedo and cotyledonary) and oil palm plantlets were collected to extract total protein and isolated glycoprotein using a concanavalin A N-linked affinity column. Tryptic glycoproteins were isolated using nano-liquid chromatography-tandem mass spectrometry. In total, 383 glycoproteins were identified and analyzed. The percentages of existence of glycoprotein were observed, from highest to lowest amounts, in the metabolic process, binding and nuclear components, respectively. Different glycoproteins were involved in membrane trafficking machinery, signaling to stress and in hormonal and environmental response for plant growth and development. PREDICTED: protein TIC 40, chloroplastic-like was expressed in the globular, torpedo and plantlet stages. The protein can be further developed into a glycoprotein biomarker, as a biological indicator of the somatic embryo maturation stage. This study should assist deeper understanding of the important role of glycoprotein specificity in somatic embryogenesis that controls plant cell response and growth development during oil palm tissue culture.

Potassium partitioning and redistribution as a function of K-use efficiency under K deficiency in sweet potato (Ipomoea batatas L.)

Interactions exist between environmental factors and potassium use efficiency (KIUE) in crops, while controversy exists on the relationship between KIUE and other crop characteristics. In field experiments conducted during 2012–2014, genotypes ‘Xu28’ (high KIUE) and ‘Ji22’ (low KIUE) were identified and analyzed under conditions of K deficiency (K0) and adequate K supply (K1). Variation in KIUE at different growth years and correlations between KIUE and other parameters were studied in field trials in 2013 and 2014, combined with a greenhouse experiment in 2015. ‘Xu28’ and ‘Ji22’ showed a consistent ranking in terms of traits involving K-use efficiency, but marked variations in KIUE were observed between field trials and greenhouse experiments, as well as at different stages of plant development in the field experiments. KIUE exhibited a significant negative correlation with whole-plant K concentration under both field and greenhouse conditions, while KIUE was significantly positively correlated with the potassium harvest index in the field experiments, although no significant correlation was observed between root tuber yield and biomass production. ‘Xu28’ exhibited faster K concentration declines than did ‘Jin22’ from plantlet stage to harvest in both the 2014 field experiment and the 2015 greenhouse experiment. In the 2014 field experiment, under K0 conditions, ‘Xu28’ shoot and root K concentrations declined from plantlet stage to harvest by 178% and 142%, respectively. In contrast, ‘Ji22’ shoot K concentration declined from plantlet stage to harvest by 86%, while root K concentration remained stable. The percentage of fallen litter K content to whole-plant K content varied from 4.5% (‘Ji22’ K0) to 8.9% (‘Xu28’ K1) under greenhouse conditions, and ‘Xu28’ exhibited significantly higher fallen litter K (as a percentage of the whole plant) than did ‘Ji22’ under K0 and K1 conditions. The root:shoot ratio of K accumulation at harvest in ‘Xu28’ was significantly higher than that in ‘Ji22’ in both the 2014 field experiment and the greenhouse trial. KIUE was positively correlated with whole-plant K concentration at harvest of sweet potato, whereas root tuber yield was not significantly correlated with KIUE. The high-KIUE ‘Xu28’ had a more optimal partitioning of K at harvest than did the low-KIUE ‘Ji22’, as well as better K translocation in the shoots and roots at different growth stages, and these traits were of crucial importance for achieving high KIUE.

Detection of lethal yellowing phytoplasma in coconut plantlets obtained through in vitro germination of zygotic embryos from the seeds of infected palms

AbstractLethal yellowing (LY) is a disease caused by 16SrIV phytoplasmas that has devastated coconut plantations in the Americas. An alternative means of phytoplasma spread is through seeds. Therefore, we used a novel approach based on plumules from the embryos of LY‐diseased coconut palms. We cultured the plumules in vitro to determine the presence of phytoplasma DNA in the plantlets. In the first assay, 185 embryos were obtained. The results showed positive detection in 20 samples (11%) with the nested PCR and in 59 samples (32%) with the TaqMan real‐time PCR. A second assay was designed to trace plumules to their respective embryos and haustorial tissues to determine whether they had derived from an embryo with positive LY detection; a total of 124 embryos were obtained. The results showed no positive detection with the nested PCR and positive detection in 42 of the haustorial tissue samples (32%) with the TaqMan real‐time PCR. The 124 plumules isolated from the embryos were cultivated under in vitro conditions and divided into two groups. Group A was followed for shoot formation and Group B was followed to the plantlet stage. After 3 months of cultivation, 33 cultures (50%) within Group A became necrotic; the rest were analysed to evaluate LY phytoplasma DNA with the TaqMan real‐time PCR assay and 14 (42%) tested positive. After 18 months of cultivation, 20 cultures (34%) within Group B became necrotic. The rest were analysed for the detection of the LY phytoplasma DNA, and 15 and 11 (39% and 29%) of the samples tested positive with the TaqMan real‐time PCR and nested PCR assays, respectively. Blast analysis of the sequenced products revealed that the sequences showed 99% homology with LY‐phytoplasma subgroup 16SrIV‐A. The results presented here demonstrate, for the first time, the occurrence of the transmission of LY phytoplasmas from coconut embryos to plantlets.

Loss of Karma transposon methylation underlies themantled somaclonal variant of oil palm.

Somaclonal variation arises in plants and animals when differentiated somatic cells are induced into a pluripotent state, but the resulting clones differ from each other and from their parents. In agriculture, somaclonal variation has hindered micropropagation of elite hybrids and genetically modified crops, but the mechanism remains a mystery1. The oil palm fruit abnormality, mantled, is a somaclonal variant arising from tissue culture that drastically reduces yield, and has largely halted efforts to clone elite hybrids for oil production2–4. Widely regarded as epigenetic5, mantling has defied explanation, but here we identify the MANTLED gene using Epigenome Wide Association Studies. DNA hypomethylation of a LINE retrotransposon related to rice Karma, in the intron of the homeotic gene DEFICIENS, is common to all mantled clones and is associated with alternative splicing and premature termination. Dense methylation near the Karma splice site (the Good Karma epiallele) predicts normal fruit set, while hypomethylation (the Bad Karma epiallele) predicts homeotic transformation, parthenocarpy and dramatic loss of yield. Loss of Karma methylation and small RNA in tissue culture contributes to the origin of mantled, while restoration in spontaneous revertants accounts for non-Mendelian inheritance. The ability to predict and cull mantling at the plantlet stage will facilitate the introduction of higher performing clones and optimize environmentally sensitive land resources.

Epigenetics: The karma of oil palms.

Despite their clonal origin, some oil palm trees develop fruits that give almost no oil. It emerges that the number of methyl groups attached to a DNA region called Karma determine which plants are defective. See Letter p.533 A flower and fruit abnormality known as 'mantled' can develop in some agricultural oil palm cultivars derived from tissue culture and the resulting mantled palms can become unproductive. Mantling is widely regarded as an epigenetic trait, but has not been fully explained. Meilina Ong-Abdullah et al. have undertaken a genome-wide, unbiased, DNA methylation analysis to look for loci epigenetically associated with the mantled phenotype. They find that hypomethylation of a single Karma family retrotransposon embedded in the intron of a homeotic gene is common to all mantled clones and associated with aberrant splicing and termination of the gene transcript. Loss of methylation — dubbed the Bad Karma epiallele — predicts a loss of oil palm yield and this property should enable screening for higher-performing clones at the plantlet stage.

Microsatellite markers linked to the locus of the watermelon fruit stripe pattern.

Agronomic performance and external and internal appearance of watermelon (Citrullus lanatus) fruit are important traits that should be taken into consideration during the development of a new cultivar, as well as being the principal identification elements used by the consumer, which are based on the external appearance and quality of the fruit. Externally, the fruit can be characterized in terms of the shape, the color of the lower rind, and the presence of grooves and stripes, the stripes can be classified as clearly defined or diffuse. The objective of this study was to identify microsatellite markers linked to the stripe pattern of watermelon fruit to support watermelon improvement programs, with the selection of this characteristic in the plantlet stage. F1 and F2 populations, result of a cross between the cultivars BRS Opara (clearly defined stripes) and Pérola (diffuse stripes), were phenotyped for their fruit stripe pattern. The CTAB 2X protocol was used for DNA extraction and 116 microsatellite markers were examined in a group of F2 plants that had fruit with well-defined stripes and fruit with diffuse stripes. The microsatellite loci MCPI_05 and MCPI_16 exhibited a linkage to the stripe pattern at a distance of 1.5 and 1.8 cM, respectively, with LOD scores of 39.28 and 38.11, respectively, which were located on chromosome six of the watermelon genome. These markers can be used in marker-assisted selection in watermelon improvement programs, by various research institutions.

The Choline Oxidase Gene codA Confers Salt Tolerance to Transgenic Eucalyptus globulus in a Semi-Confined Condition

The performance of tree species is influenced by environmental factors and growth stages. To evaluate the practical performance of transgenic tree species, it is insufficient to grow small, young trees under controlled conditions, such as in a growth chamber. Three transgenic Eucalyptus globulus lines, carrying the choline oxidase gene, were investigated for their salt tolerance and expression of the transgene at the young plantlet stage in a special netted-house. To clarify the characteristics at the young as well during the later stages, salt tolerance and the properties of the transgenic lines at large juvenile and adult stages were evaluated in the special netted-house. All transgenic lines showed high glycinebetaine content, particularly in young leaves. Trees of the transgenic line 107-1 showed low damage because of salinity stress based on the results from the chlorophyll analysis and malondialdehyde content, and they survived the high-salt-shock treatment at the large juvenile and adult stages. Only this line showed salt tolerance at all stages in the special netted-house. In this evaluation in the special netted-house, the tolerant line among young plantlets might perform better at all stages. Since evaluation in these special netted-house mimics field evaluation, line 107-1 is a potential tolerant line.

Évaluation de la tolérance à la salinité du myrte (Myrtus communis) aux stades germinatif et plantule

The salinity tolerance and development of diverse myrtle ecotypes were evaluated in relation to salinity, at the germination and plantlet stages. Six myrtle ecotypes (Tébaba, Jbel Abderahmane, Diar Ferjan, Ain Bacouche, Ain Dhebla, and Ouchetata) were used to conduct germination tests, as well as cultivation to the plantlet stage. Disinfected seeds were germinated in a controlled growth chamber (RH, 80%; temperature, 25 °C) using different saline treatments (0, 2, 4, 6, 8, 10, and 12 g·L–1 NaCl. Seedlings were cultivated in a greenhouse, in boxes filled with perlite. The seedlings were given Knop’s nutrient solution, up to the four-leaf stage. Thereafter, the saline stress treatments were applied as increasing concentrations of NaCl added to the Knop solution. The effects of salinity on germination varied with ecotype and concentration of NaCl. A progressive decrease in the rate of germination for myrtle was observed with increasing concentration of NaCl. Moreover, germination was delayed by salinity, especially with susceptible ecotypes. Ecotypes from Ouchetata and Diar Ferjan germinated better in presence of salt than did the Jbel Abderahmane ecotype. The growth of myrtle plantlets cultivated under salt stress was also variable according to ecotype and salt concentrations. Growth of aerial, as well as root parts, was reduced by NaCl concentrations higher than 6 g·L–1. The number of leaves was also affected by salinity; a reduction of five leaves was observed for most ecotypes when increasing NaCl from 0 to 12 g·L–1. It is concluded that development of myrtle under saline stress differs according to the development stage (germination, plantlet), and that the ecotypes tested can germinate and grow in the presence of 12 g·L–1 NaCl. This salt tolerance, observed at early stages, remains to be confirmed for the adult plants. This work was conducted as an essential preliminary step in preparing to cultivate myrtle in saline soils or soils irrigated with salt water, for prospective commercial exploitation of the essential oils of this species.

Induced Resistance by β-Aminobutyric Acid in Artichoke against White Mould Caused by Sclerotinia sclerotiorum

β-aminobutyric acid (BABA) was assessed for the ability to protect two artichoke cultivars, C3 and Exploter, against white mould caused by Sclerotinia sclerotiorum, which represents a major problem in the cultivation of this crop in many growing areas of Central Italy. Changes in the activity and isoenzymatic profiles of the pathogenesis-related (PR) proteins β-1,3-glucanase, chitinase and peroxidase in plantlets upon BABA treatment and following inoculation of the pathogen in plantlets and leaves detached from adult plants were also investigated as molecular markers of induced resistance and priming. BABA treatments by soil drenching induced a high level of resistance against S. sclerotiorum in artichoke plantlets of both cultivars C3 and Exploter with a similar level of protection and determined a consistent increase in peroxidase activity paralleled with the differential induction of alkaline isoenzyme with a pI 8.6. A consistent change was found in Exploter in the peroxidase activity following BABA treatments and pathogen inoculation and was paralleled with the expression of an anionic band in plantlets and both anionic and cationic bands in leaves. Our results showed a correlation between BABA-induced resistance (BABA-IR) and a augmented capacity to express basal defence responses, more pronounced in cultivar C3 and associated β-1,3-glucanase accumulation in both plantlets and leaves inoculated with the pathogen, whereas chitinase resulted affected only at plantlet stage. The present results represent the first one showing the effect of BABA in inducing resistance in artichoke and associated accumulation of selected PRs. If confirmed in field tests, the use of BABA at early plant stages may represent a promising approach to the control soilborne pathogens, such as the early infection of S. sclerotiorum.