Horticultural Plant Species Research Articles

Zucchini lineages with levels of resistance to ZYMV and SqMV viruses

Zucchini (Cucurbita pepo L.) is a horticultural plant species of great socioeconomic value in tropical countries such as Colombia and Brazil. The production of zucchini is qualitatively and quantitatively affected by many diseases, especially viruses belonging to the Potyvirus (Zucchini yellow mosaic virus - ZYMV) and Comovirus (Squash mosaic virus - SqMV) groups. The primary strategy to reduce the spread of potentially damaging plant viruses is the development of genotypes with genetic tolerance; however, there are not many zucchini genotypes with multiple tolerance. Therefore, this study evaluated 66 zucchini genotypes to find sources of tolerance to the ZYMV and SqMV viruses. This experiment was conducted in a completely randomized design using genotypes from the germplasm bank of the Federal University of Uberlândia, including the genotypes: Emanuela (common commercial genotype) ‘Tronco Caserta’ (susceptible genotype) and PX 13067051 (resistant genotype). Leaf extracts containing viral particles were used as inoculant, and the distribution of grades of tolerance was recorded at the seedling stage. The lineages UFU-C×UFU-A#18#3;1, UFU-C×UFU-F#19#11;3, UFU-F#4#9;1, and UFU-D×UFU-F#7#21;1 and the Emanuela cultivar are alternatives for the production of new zucchini genotypes or hybrids with tolerance to the viruses ZYMV and SqMV. More severe symptoms were observed, as well as a larger number of susceptible genotypes for the ZYMV virus, indicating that this virus has great potential for causing damage and losses to zucchini crops.

The Complete Plastid Genome of Rhododendron pulchrum and Comparative Genetic Analysis of Ericaceae Species

Background and Objectives: Rhododendron pulchrum Sweet (R. pulchrum) belongs to the genus Rhododendron (Ericaceae), a valuable horticultural and medicinal plant species widely used in Western Europe and the US. Despite its importance, this is the first member to have its cpGenome sequenced. Materials and Methods: In this study, the complete cp genome of R. pulchrum was sequenced with NGS Illumina HiSeq2500, analyzed, and compared to eight species in the Ericaceae family. Results: Our study reveals that the cp genome of R. pulchrum is 136,249 bp in length, with an overall GC content of 35.98% and no inverted repeat regions. The R. pulchrum chloroplast genome encodes 73 genes, including 42 protein-coding genes, 29 tRNA genes, and two rRNA genes. The synonymous (Ks) and nonsynonymous (Ka) substitution rates were estimated and the Ka/Ks ratio of R. pulchrum plastid genes were categorized; the results indicated that most of the genes have undergone purifying selection. A total of 382 forward and 259 inverted long repeats, as well as 221 simple-sequence repeat loci (SSR) were detected in the R. pulchrum cp genome. Comparison between different Ericaceae cp genomes revealed significant differences in genome size, structure, and GC content. Conclusions: The phylogenetic relationships among eight Ericaceae species suggested that R. pulchrum is closely related to Vaccinium oldhamii Miq. and Vaccinium macrocarpon Aiton. This study provides a theoretical basis for species identification and future biological research of Rhododendron resources.

First report of Phyllosticta capitalensis causing leaf spots on ornamental Magnolia grandiflora and Syringa reticulata in Iran

Magnolia grandiflora is a medicinal and horticultural plant species in the family Magnoliaceae which is native to North America (Li et al., 2013). Syringa reticulata is a tree in the family Oleaceae which is native to Japan (Green et…

Do horticultural tree plant species depend on mycorrhizal inoculation under marginal soil conditions?

Do horticultural tree plant species depend on mycorrhizal inoculation under marginal soil conditions?

Complete chloroplast genome of Rhododendron pulchrum, an ornamental medicinal and food tree

The semi-evergreen azalea, Rhododendron pulchrum, a valuable horticultural and medicinal plant species. Using next-generation sequencing, applying a combination of de novo and reference-guided assembly, we sequenced its complete chloroplast genome. Our study reveals that R. pulchrum have a typical cp genome of 136,249 bp in length, without inverted repeat regions. A total of 73 genes, 42 of which are protein coding genes, 29 tRNA genes, two rRNA genes were identified. The GC content of the whole genome is 35.98%. Phylogenetic analysis indicates that R. pulchrum is closely related to the species of Vaccinium oldhamii and Vaccinium macrocarpon.

Genetic diversity and population structure of Rhododendron simsii (Ericaceae) as revealed by microsatellite markers

Rhododendron simsii Planch. (Ericaceae) is a valuable horticultural and medicinal plant species. In this study, the genetic diversity of eight wild R. simsii populations from the Dabie Mountains (central China) was investigated with 29 microsatellite markers. The results showed that R. simsii harbored a high level of genetic diversity (HE: 0.64–0.79; HO: 0.71–0.94; I = 1.917; h = 0.826), and 84.34% of this genetic variation was maintained within populations, while variation among populations only accounted for 15.66%. The number of alleles ranged from 6 to 11, with an average of 9.069. Heterozygote excess was found, with the mean FIS and FIT values of −0.1739 and 0.0092, respectively. The average value of gene flow (Nm) was 1.3525. Within‐population, genetic diversity (I) ranged from 1.131 to 1.681. Cluster analyses divided the eight populations into two clades: the ‘Ltjiuzihe’ population formed its own cluster, while the other seven populations clustered together. There was a weak negative correlation between genetic and geographic distance. The results are highly relevant for the conservation and sustainable utilization of wild R. simsii germplasm resources in central China.

How applicable are dormant buds in cryopreservation of horticultural woody plant crops? TheMaluscase

Using dormant buds (DB) for germplasm cryopreservation was published few decades ago and since then, dormant buds have been used to preserve genetic resources of selected horticultural woody plant species. The advantages of employing DB in preservation are widely known; the most relevance is no requirements of aseptic cultures, high processing throughput and involvement of a relatively low skilled technical support; but the method has also shortcomings, such as seasonality of processing and lack of procedural modifications that might support preservation of all accessions in a collection. The US, NLGRP cryopreserved DB of 2168 unique Malus (Mill.) accessions (among 51 species) with a ≥40% post cryo viability. The method worked well for all accessions in 20 species, for ≥90% of accessions in six species and at a various percent (0-89%) in the remaining 25 species. For species with the largest number of processed accessions, the M. domestica, Borkh., M. hybrid and M. sieversii (Ledeb.) M. Roem. (1355, 326 and 128 cryopreserved accessions, respectively), the percent of accessions responding favorable to the DB method was high (96, 96 and 82%). The results indicated variability in Malus DB response to liquid nitrogen exposure; similar results were recorded in the Pyrus L. collections. Procedural refinements of the DB cryopreservation method could increase the method applicability to a much higher number of Malus species and its use in other collections of horticultural woody plants like Prunus L. and Pyrus L.

Biostimulants research in some horticultural plant species—A review

AbstractDifferent substances from the natural origin which have beneficial effects on plant growth and development, stress resistance, and crop yield and quality can be called biostimulants or biostimulators. Their physiological effects depend on their composition as they contain various organic and mineral compounds which plants can use as metabolites, growth regulators, and nutrients; however, biostimulants cannot be considered biofertilizers. Biostimulants applied in plant production have been widely considered as an environment‐friendly agricultural practice—and so are now among tools used in sustainable agriculture. Here, we discuss the results of the biostimulants’ effect investigations performed in Croatia, focused on horticultural crops, with edible plant species, such as tomato, garlic, bell pepper, lettuce, strawberry, garden cress, and basil, as well as ornamentals, such as wild rose, wax begonia, Mexican and French marigold, moss rose, everlasting flower, common zinnia, English primrose, and scarlet sage. The investigated biostimulants were applied at all plant growth stages, from germination to full plant and fruit or flower commercial maturity, using the seed treatment, foliar application, or irrigation. To evaluate biostimulant effectiveness, various morphological, physiological, and quality traits were analyzed. In this wide array of studies, the evaluated biostimulants mostly enhanced seed and transplant vigor, stimulated vegetative growth, improved nutrient acquisition and distribution within the plant, increased antioxidative capacity of plant tissues, contributing to higher stress tolerance, and improved plant yield and fruit/flower quality. In general, the research reviewed here implies possible benefits of biostimulant application in horticultural production, especially in stressful growth conditions, such as the transplant stage, reduced fertilization, or incidence of other abiotic stress. Considering possible interactions among the contained physiologically active compounds, the effects on plants may depend on dose, time of treatment, growth conditions, and plant species. Therefore, further research of biostimulant applications in horticultural production is suggested.

Unbalanced historical phenotypic data from seed regeneration of a barley ex situ collection

The scarce knowledge on phenotypic characterization restricts the usage of genetic diversity of plant genetic resources in research and breeding. We describe original and ready-to-use processed data for approximately 60% of ~22,000 barley accessions hosted at the Federal ex situ Genebank for Agricultural and Horticultural Plant Species. The dataset gathers records for three traits with agronomic relevance: flowering time, plant height and thousand grain weight. This information was collected for seven decades for winter and spring barley during the seed regeneration routine. The curated data represent a source for research on genetics and genomics of adaptive and yield related traits in cereals due to the importance of barley as model organism. This data could be used to predict the performance of non-phenotyped individuals in other collections through genomic prediction. Moreover, the dataset empowers the utilization of phenotypic diversity of genetic resources for crop improvement.

Salicylic acid loaded chitosan microparticles applied to lettuce seedlings: Recycling shrimp fishing industry waste

Shrimp fishing industry wastes are still a main problem with high environmental impact worldwide. In this study, chitosan with ultra-high molecular weight and deacetylation degree ≥85% was obtained from shrimp fishing industry waste from Argentinean Patagonia. Chitosan based microparticles capable to entrap salicylic acid, a phytohormone known to play major role in the regulation of plant defense response against various pathogens, were prepared using TPP as crosslinker. Unloaded microparticles and microparticles loading several salicylic acid amount were fully characterized exhibiting a size between 1.57 μm and 2.45 μm. Furthermore, a good PDI, entrappment efficiencies from 59% to 98% and salicylic acid sustained release over 24 h were achieved.Chitosan based microparticles were non toxic in most of the doses applied in lettuce seedlings. Instead, microparticles can positively modulate plant growth and have the potential to improve plant defense responses. In particular salicylic acid loaded microparticles effect was very promising for its application as activators of salicylic acid dependent plant defense responses in lettuce as a model of horticultural plant species.

Changes in gas exchange, root growth, and biomass accumulation of Platycladus orientalis seedlings colonized by Serendipita indica

Serendipita indica (formerly known as Piriformospora indica), a root endophytic fungus, exhibits multiple functions in some agricultural, horticultural, and medicinal plant species. We studied colonization of the roots of Platycladus orientalis, a forest tree species, by S. indica to improve the quality of the seedlings in seedbeds and survival rates in sylviculture. At 20 days after inoculation, S. indica colonized the root cortex of P. orientalis seedlings. Root colonization by S. indica significantly increased net CO2 assimilation, light use efficiency, and biomass accumulation by both roots and shoots, whereas it did not affect the biomass allocation between roots and shoots. In addition, the symbiosis significantly increased root total length, surface area, and volume. In view of the two specific traits of S. indica, i.e., axenic culture and wide colonization in plants, the fungus might be used for improving quality of P. orientalis seedlings and increasing their survival after transplanting.

Flow cytometry – a modern method for exploring genome size and nuclear DNA synthesis in horticultural and medicinal plant species

Abstract Flow cytometry (FCM) has been used for plant DNA content estimation since the 1980s; however, presently, the number of laboratories equipped with flow cytometers has significantly increased and these are used extensively not only for research but also in plant breeding (especially polyploid and hybrid breeding) and seed production and technology to establish seed maturity, quality and advancement of germination. A broad spectrum of horticultural and medicinal species has been analyzed using this technique, and various FCM applications are presented in the present review. The most common application is genome size and ploidy estimation, but FCM is also very convenient for establishing cell cycle activity and endoreduplication intensity in different plant organs and tissues. It can be used to analyze plant material grown in a greenhouse/field as well as in vitro. Due to somaclonal variation, plant material grown in tissue culture is especially unstable in its DNA content and, therefore, FCM analysis is strongly recommended. Horticultural species are often used as internal standards in genome size estimation and as models for cytometrically studied cytotoxic/anticancer/allelopathic effects of different compounds. With the growing interest in genome modification, increased application of FCM is foreseen.

Effects of elevated carbon dioxide (CO2) on flowering traits of three horticultural plant species

Carbon dioxide (CO) has been increasing homogeneously worldwide since industrial revolution. Current CO concentrations are around 400 ppm, which may increase over this century to 430 ppm (best scenario) to > 1000 ppm (worst scenario) (IPCC, 2013). Species-level responses of plant traits to elevated carbon dioxide (eCO), especially those that affect interactions with pollinators, could potentially have flow-on effects to both ecological communities and horticultural industries. The impacts of eCO on flowering traits in pepper (Capsicum annuum - Giant Bell), tomato (Lycopersicon lycopersicum- var. Tomato Roma) and zucchini (Cucurbita pepo - Zucchini Blackjack), all economically important horticultural species, were investigated. Twenty plants of each species were grown under two treatments: 1) two glasshouses with ambient CO (400 ppm), and 2) two with eCO (555 ppm). For both treatments, we measured the number of flowers, flower longevity and dry biomass for all species; pollen diameter and number of pollen grains for tomato and zucchini and the sucrose concentration and nectar production in zucchini. Elevated CO had few significant effects on the measured traits, the main exceptions being in zucchini, which produced more male flowers, fewer pollen grains per plant and fewer female flowers under this treatment. Pepper also produced fewer flowers at eCO while tomato was the least sensitive species. Future studies could be aimed at testing sensitivity of different varieties of these important commercial species to eCO.

Growth chambers on the International Space Station for large plants

The International Space Station (ISS) now has platforms for conducting research on horticultural plant species under LED lighting, and those capabilities continue to expand. The 'Veggie' vegetable production system was deployed to the ISS as an applied research platform for food production in space. Veggie is capable of growing a wide array of horticultural crops. It was designed for low power usage, low launch mass and stowage volume, and minimal crew time requirements. The Veggie flight hardware consists of a light cap containing red (630 nm), blue, (455 nm) and green (530 nm) LEDs. Interfacing with the light cap is an extendable bellows/baseplate for enclosing the plant canopy. A second large plant growth chamber, the Advanced Plant Habitat (APH), is will fly to the ISS in 2017. APH will be a fully controllable environment for high-quality plant physiological research. APH will control light (quality, level, and timing), temperature, CO2, relative humidity, and irrigation, while scrubbing any cabin or plant-derived ethylene and other volatile organic compounds. Additional capabilities include sensing of leaf temperature and root zone moisture, root zone temperature, and oxygen concentration. The light cap will have red (630 nm), blue (450 nm), green (525 nm), far red (730 nm) and broad spectrum white LEDs (4100K). There will be several internal cameras (visible and IR) to monitor and record plant growth and operations. Veggie and APH are available for research proposals.

Transcriptome Sequencing and Analysis of Wild Pear (Pyrus hopeiensis) Using the Illumina Platform

Pears are cultivated worldwide as an economically valuable fruit of the Rosaceae. Because of the lack of genomic resources, few molecular biology studies have focused on wild pear, which are less abundant than partially cultivated pear species. However, high-throughput transcriptome sequencing technologies enabled the advent of genomic studies requiring shorter time and minimal costs, allowing efficient wild pear research. Pyrus hopeiensis is an endangered and valuable horticultural plant species, and its transcriptome was sequenced in this study. Overall, 25,877,477 high-quality reads and 48,278 unigenes were generated with the Illumina platform from four different tissue samples. A total of 27,005 (55.94 %) unigenes were successfully annotated. Of these, 26,941 and 19,248 unigenes were annotated in the National Center for Biotechnology Information non-redundant (Nr) protein database and the Swiss-Prot protein database, respectively. In addition, 18,590 and 7505 unigenes were assigned to Gene Ontology and Cluster of Orthologous Groups classifications, respectively, and a total of 5104 unigenes were mapped to 123 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Furthermore, 4301 simple sequence repeat markers were identified in P. hopeiensis, which will be used in future research of the genetic diversity of Pyrus. Finally, the results indicated that lignin biosynthesis, secondary metabolism and suberin/cutin/wax biosynthesis were involved in the russet pericarp formation process of P. hopeiensis. Detailed examination of these pathways revealed 54 candidate genes were predicted based on the KEGG pathways, which encoded 10 key enzymes involved in lignin biosynthesis; moreover, 33 additional regulatory genes for pigmentation of wild pear russet pericarp were also summarized. In summary, this effective RNA-Seq study provides comprehensive genetic and genomic insight into the endangered P. hopeiensis species, which will improve future studies on the molecular mechanism of the appearance and quality of this fruit.

Transcriptome Sequencing and Analysis of Wild Pear (Pyrus trilocularis) using the Illumina Platform

Pears are cultivated worldwide as an economically valuable fruit of family Rosaceae. Because of the lack of genomic resources, few molecular biology studies have been focused on wild pear which are less abundant than partially cultivated pear species. However, high-throughput transcriptome sequencing technologies enabled the advent of genomic studies requiring shorter time and minimal costs, allowing efficient wild pear research. Pyrus trilocularis is an endangered and valuable horticultural plant species, and its transcriptome was sequenced in this study. Overall, 21860128 high-quality reads and 42879 unigenes were generated with the Illumina platform from 4 different tissue samples. A total of 26059 (60.77%) unigenes were successfully annotated. Of these, 26029 and 18467 unigenes were annotated in the NCBI Nr protein database and the Swiss-Prot database, respectively. In addition, 18872 and 7199 unigenes were assigned to GO and COG classifications, respectively, and a total of 4993 unigenes were mapped to 129 KEGG pathways. Furthermore, 3864 SSR markers were identified in P. trilocularis, which will be used in future research of the genetic diversity of Pyrus. Finally, 100 candidate genes were predicted on the basis of KEGG pathways, which may encode key enzymes involved in plant hormone signal transduction. In summary, this effective RNA-Seq study provides comprehensive genetic and genomic insight into the endangered P. trilocularis species, which may improve future studies on the molecular mechanism of the pear tree resistance.

Role of salicylic acid in phosphite-induced protection against Oomycetes; a Phytophthora cinnamomi - Lupinus augustifolius model system

Phosphite is used to control Oomycetes in a wide range of horticultural and native plant species worldwide. However, phosphite can be phytotoxic, and some pathogens have exhibited a reduction in the effectiveness of phosphite due to prolonged use. In this study, salicylic acid (SA) was investigated as an alternative, or supplementary, treatment to be used to protect plant species. With the use of aeroponics chambers, foliar application of phosphite, SA, and phosphite/SA to Lupinus augustifolius was assessed in relation to root tip damage, in planta phosphite and SA concentration and lesion development. Both phosphite and SA were measurable at the root tip within 24 h of application, and all treatments significantly (P ≤ 0.05) reduced the lesion length at 7 days. However, while phosphite and SA application increased the in planta SA concentration, phosphite caused significantly more damage to the root tip by reducing root cap layers and length than the SA, or phosphite/SA application. This study supports the notion that phosphite-induced sensitivity may be SA-dependent, as both phosphite and SA were found to control P. cinnamomi and stimulate SA accumulation. A combination of phosphite and SA may be more beneficial to plants if it can reduce phytotoxic effects and reduce the chance of pathogen sensitivity to phosphite.

Corrigendum to: Metabolomic characterisation of the functional division of nitrogen metabolism in variegated leaves

Many horticultural and natural plant species have variegated leaves, that is, patchy leaves with green and non-green or white areas. Specific studies on the metabolism of variegated leaves are scarce and although white (non-green) areas have been assumed to play the role of a 'nitrogen store', there is no specific studies showing the analysis of nitrogenous metabolites and the dynamics of nitrogen assimilation. Here, we examined the metabolism of variegated leaves of Pelargonium × hortorum. We show that white areas have a larger N : C ratio, more amino acids, with a clear accumulation of arginine. Metabolomic analyses revealed clear differences in the chemical composition, suggesting contrasted metabolic commitments such as an enhancement of alkaloid biosynthesis in white areas. Using isotopic labelling followed by nuclear magnetic resonance or liquid chromatography/mass spectrometry, we further showed that in addition to glutamine, tyrosine and tryptophan, N metabolism forms ornithine in green area and huge amounts of arginine in white areas. Fine isotopic measurements with isotope ratio mass spectrometry indicated that white and green areas exchange nitrogenous molecules but nitrogen export from green areas is quantitatively much more important. The biological significance of the metabolic exchange between leaf areas is briefly discussed.

Parameters for Selecting Efficient Arbuscular Mycorrhizal Fungi for Plants Under Microcosm Conditions

Arbuscular mycorrhizal (AM) fungi are mutualistic symbionts imparting a number of benefits to plants and are being advocated for being potential biofertilizer in the agriculture and forestry sectors. Superior AM fungi for forestry tree species (Acacia nilotica var. cupressiformis, Albizzia lebbeck and Eucalyptus tereticornis) and horticultural plant species (Capsicum annum, Allium cepa and Fragaria ananassa) were evaluated in a completely randomized design microcosm trial involving AM species of native and exotic origin. Out of ten AM fungal species used with forest species, G. intraradices (AM-1004) and mixed indigenous AM fungi (AM-1209) were found to give the highest P uptake in shoots, whereas in horticultural plants AM-1004 and AM-1207 (commercial inoculum, Mycorise) followed by mixed indigenous AM fungi (AM-1209) gave the highest P uptake in shoots. The shoot dry weight in these superior AM-mediated plants also indicated greater response and were highly correlated with P uptake (r = 0.53–0.88) and to a lesser extent with root colonization (r = 0.41–0.81). P uptake in the early growth stage (6–8 weeks) of AM-inoculated plants can be used as an indicator to evaluate superior AM fungi for growth promotion of forestry and horticultural plant species.

Efficacy of Pesticide Mixtures Against the Western Flower Thrips (Thysanoptera: Thripidae) Under Laboratory and Greenhouse Conditions

Western flower thrips, Frankliniella occidentalis Pergande is a commonly encountered and economically important insect pest of greenhouses. Greenhouse producers typically apply pesticides as mixtures to mitigate western flower thrips populations; however, there is limited information available on the compatibility and efficacy of commonly used pesticide mixtures. This study assessed nine binary and three tertiary pesticide mixtures used in greenhouses which included pesticides containing abamectin, acephate, azadirachtin, bifenazate, bifenthrin, fenpropathrin, imidacloprid, novaluron, pymetrozine, and spinosad. Compatibility was determined for the binary pesticide mixtures using jar tests. In addition, the binary mixtures were applied to nine horticultural plant species to determine phytotoxicity based on visual appearance assessed 7 d after treatment. Bean-dip bioassays were performed in a laboratory using green bean (Phaseolus vulgaris L.) to determine LC50 values for each individual pesticide and the mixtures to establish whether the mixtures were synergistic, antagonistic, or there was no effect. The mortality of western flower thrips was assessed after 24 h, and LC50 values were calculated. Furthermore, semifield bioassays were performed in greenhouses for binary and tertiary mixtures to evaluate the efficacy (based on percent mortality) of the pesticide mixtures against western flower thrips. Results indicated that all binary mixtures were visibly compatible, and not phytotoxic to any of the plant species evaluated. Combination index calculations based on laboratory results indicated most of the binary mixtures were synergistic; however, the mixture containing spinosad + bifenazate appeared to be antagonistic against western flower thrips. The semifield bioassays demonstrated significantly reduced efficacy associated with mixtures containing azadirachtin, however, all binary mixtures provided approximately 80% western flower thrips mortality.