Gerbera Jamesonii Bolus Research Articles

Evaluation of hyperaccumulation potentials to cadmium (Cd) in six ornamental species (compositae)

Phytoremediation is considered as a promising soil remediation technique. In the present study, the growth responses, cadmium (Cd) accumulation and uptake capability of six popular compositae species, namely, Taraxacum mongolicum Hand.-Mazz., Tagetes erecta L., Tagetes patula L., Zinnia elegans Jacq., Centaurea cyanus L. and Gerbera jamesonii Bolus under Cd stress were investigated. Among the six compositae species, the growth of T. erecta L. and T. patula L. improved under 10 mg kg−1 Cd exposure in term of the total biomass and height increased along with the increased Cd concentration in soil, and the growth of the two plants had no significant differences at the high Cd concentration (100 mg kg−1), which indicated that they have good tolerance to Cd toxicity. At the same time, the two plants have higher biomass than four other plants. Furthermore, they can accumulate Cd above 100 μg g−1 dry tissue, which is the threshold value of a Cd-hyperaccumulator, and have higher Cd uptake ability, translocation factor (TF) and bioconcentration factor (BCF) values. According to these traits, it was shown that T. erecta L. and T. patula L. had strong tolerance and accumulation capability to Cd, therefore they can become potential hyperaccumulators in phytoremediation of Cd-contaminated soils.

Efficient TDZ-induced regeneration from capitulum explants of Gerbera jamesonii Bolus ex Hooker F. - an ornamental plant with high aesthetic value

Gerbera jamesonii Bolus ex Hooker F. (Asteraceae), a most prominent ornamental plant ranking fifth in the world cut flower market has gained huge demand across the globe for its high aesthetic value. In the present study, an efficient plant regeneration protocol was developed using capitulum explants from the field grown mature plants of G. jamesonii. A successful surface sterilization procedure was established using a series of sterilants without affecting explant regenerability. The culture of capitulum explants on Pre-culture Induction Medium [(PIM), Murashige and Skoog (MS) medium fortified with 0.5 mg/L thidiazuron (TDZ) in combination with low levels of auxins] for a period of 2 weeks in dark conditions was crucial for inducing morphogenetic response. Upon transfer onto Shoot Regeneration Medium [(SRM), MS +4.0 mg/L 6-benzyladenine (BA) and 0.2 mg/L NAA], explants has significantly produced highest number of shoots (16 ± 0.33). Incubation for 18–21 days on Shoot Multiplication and Elongation Medium [(SMEM), MS +2.0 mg/L BA +0.2 mg/L NAA] resulted in the highest number of multiple shoots (22.00 ± 0.93) with increased mean shoot length (3.49 ± 0.08). In vitro elongated shoots were rooted (95%) on ½ MS +1.0 mg/L indole-3-acetic acid (IAA) within 10–12 days and fully rooted plants were transferred to poly-house for hardening with 90% survival rate.

Callusing and regeneration response of in vitro derived leaf explants of gerbera (Gerbera jamesonii)

Gerbera (Gerbera jamesonii Bolus ex. Hookes F.) is one of the most popular commercial flowers worldwide used both as cut flower and potted plant. Conventionally, it is propagated through vegetative means such as divisions of clump which is very slow process and not commercially viable. Rapid multiplication of elite hybrids/genotypes with improved quality traits, has been achieved by using both direct and indirect tissue culture methods. Gerbera hybrid seeds obtained by half-sib mating were raised in half strength MS medium. The earliest days for seed germination(2.00), first leaf development (3.00 days) and rooting (3.00 days) was recorded line IIHR1-1, IIHR 5-4 and IIHR1-1, IIHR1-2, IIHR1-5, IIHR3-2 and IIHR5-4. The response of in vitro leaf explants to callusing and regeneration was recorded when cultured on full strength Murashige and Skoog's media supplemented with different concentrations of 2,4-D or BAP or IAA and Kinetin. Leaf explants cultured on MS medium fortified with equal concentration of BA (1 mg l-1) and 2, 4-D (1 mg l-1) produced green and greenish white granular callus within 25 days, however, leaf explants cultured on MS medium supplemented with 2,4-D produced yellowish callus. Plant regeneration was also found earliest in the same media within 14 days.

Characterization of stomata on floral organs and scapes of cut ‘Real’ gerberas and their involvement in postharvest water loss

Stomata present on leaves are the main channels for water vapor exchange between the plant and atmosphere, and contribute to water loss of cut flowers. Although cut gerberas (Gerbera jamesonii Bolus) are commonly composed of a terminal composite floral head and a scape, and have no leaves, they are also prone to severe water deficits, presumably resulting from water loss exceeding water uptake. We have investigated the distribution and characteristics of stomata of cut ‘Real’ gerberas, and their response to light and abscisic acid (ABA) treatments, to increase understanding of their functionality in postharvest water loss. Stomata were widely distributed on various parts of floral organs and the scape in cut gerberas, including the lower epidermis of the ray floret petals, trans florets, disc florets, lower epidermis of sepals, and the uppermost and middle parts of scape surfaces. The highest stomatal density was observed on the lower epidermis of sepals. Cut gerberas had the largest stomata on the middle scape surface and the smallest on the surface of the uppermost scape. Nonetheless, the lower epidermis of sepals had the highest relative stomatal area, which was higher than that of the other parts. Additionally, the lower sepal epidermis had the highest maximum stomatal conductance of water vapor (gwmax), and which was higher than that of the lower and upper leaf epidermis. The opening of stomata on various parts of cut gerberas differed in their response to light, and the highest percentage of open stomata and largest aperture were found in the stomata on the lower epidermis of sepals. Changes in water loss in cut gerberas exhibited a distinct circadian rhythm over a four-day vase period with an alternating 12-h light/dark cycle. In the lower epidermis of sepals, ABA painting treatment significantly inhibited stomatal opening and reduced water loss in cut gerberas over a 6 h light period. These findings imply the critical involvement of stomata on the lower epidermis of sepals in water loss of cut gerberas, and improve our understanding of the mechanism underlying their water deficit symptoms.

Indirect Micropropagation of Gerbera jamesonii Bolus cv. Winter Queen through Callus Redifferentiation

Indirect Micropropagation of Gerbera jamesonii Bolus cv. Winter Queen through Callus Redifferentiation

Combination Effect of 1-Methylcyclopropene (1-MCP) with Ajowan Essential Oil and Silver Nanoparticles on Postharvest Life of Gerbera (Gerbera jamesonii) Cut Flowers

Gerbera (Gerbera jamesonii Bolus ex. Hook f.) is one of the most important cut flowers in floriculture industry with high economic value. Short postharvest life is the main barrier for gerbera marketing which is related to water relation disruption resulting from microbial population in preservative solution and exposure to ethylene. Therefore, an experiment was conducted to study the combination effect of an ethylene inhibitor, 1-methylcyclopropene (1-MCP) (0 and 1 μL·L−1), and two antimicrobial agents, ajowan [Carum copticum (L.) C. B. Clarke] essential oil (EO) (0 and 15 μL·L−1) and silver nanoparticles (AgNPs) (0 and 40 μL·L−1), on postharvest life of ‘Pink Power’ gerbera cut flowers. The results showed that stem diameter reduced in both cut stem-end (CSE) and below the flower head (BFH) but the amount of decrease in CSE was more than BFH, and applied treatments had no significant effect on the decrease rate. However, both ajowan EO and AgNPs treatments reduced the number of bacteria at the CSE; ajowan EO was more effective than AgNPs and induced more vase solution uptake. Stem-end electrolyte leakage (EL) was unaffected by 1-MCP treatment, whereas petal EL was lower in 1-MCP-treated flowers. The least wilting percentage and the longest vase life were observed in combination treatment of 1-MCP and either ajowan EO or AgNPs. It could be concluded that 1-MCP combined with ajowan EO or AgNPs, potentially can be used as a preservative solution to enhance postharvest life, delay flower senescence, and prolong vase life of gerbera cut flowers.

In vitro propagation of Gerbera jamesonii Bolus ex Hooker f. in a temporary immersion bioreactor

In the global flower industry, gerbera (Gerbera jamesonii Bolus ex Hooker f.) is ranked within the top 10 cut ornamental flowers. Commercially, micropropagation is more important than seed or vegetative propagation. This study assessed the viability of using a temporary immersion bioreactor (TIB; BIT®) to propagate shoots in vitro. Factors such as immersion frequency (6, 8 and 12 h), additional ventilation (1 min every 2 h) and the length of duration of shoot culture (14, 21, 28 and 35 days) were tested. Immersion every 8 h with additional ventilation produced more shoots with better morphology than the control. The average multiplication rate was 9 shoots/explant across treatments. However, when shoots were immersed every 6 h, shoots had higher fresh and dry weight, but displayed hyperhydricity. No differences in shoots were found when immersion frequency was 8 or 12 h. Additional ventilation (12 min/day) reduced shoot hyperhydricity to 5.24% as compared to the ventilation-free control (31.37%). Shoots receiving additional air supply every 8 h had lower fresh and dry weight with an 89.8% decline in relative water content. The number of shoots/explant increased as culture time increased, 6.7 after 28 days, and 6.1 after 35 days (statistically equal). After 7 and 14 days, shoots were induced to root in the TIB using the same medium but supplemented with IAA. Plantlets were subsequently acclimatized. More than 87% of plantlets survived in a zeolite and sugarcane filter cake (1:1) substrate. This protocol allows for the mass production of gerbera shoots in a simple TIB, with effective rooting and acclimatization. This is the first documented TIB for gerbera.

Effects of foliar application of FeSO4 and ZnSO4 on leaf tissue nutrients of gerbera (Gerbera jamesonii) varieties under protected condition

The present study was conducted to evaluate the effects of foliar application of FeSO4 and ZnSO4 on leaf tissue nutrients of gerbera (Gerbera jamesonii Bolus) varieties under protected condition during 2010-11. The experiment was laid out in Factorial Completely Randomized Design with three replications and 18 treatment combinations, comprising three varieties of gerbera, viz. Faro (V1), Dana Allen (V2), Roselin (V3) and six levels of micronutrients, i.e. control (M1), FeSO4 @ 0.2% (M2), FeSO4 @ 0.3% (M3), ZnSO4 @ 0.2% (M4), ZnSO4 @ 0.3% (M5) and FeSO4 + ZnSO4 @ 0.2% each (M6). The present results have shown that the maximum increasing range of nutrients content in leaves as 45.00 to 69.71 ppm, 26.50 to 62.76 ppm, 2.60 to 4.83% and 3.36 to 5.45% of total Fe, Zn, N and K content in leaves, respectively was observed in variety V2 (Dana Allen) from 1st to 12th month of gerbera, while the minimum range of nutrients 43.53 to 67.50 ppm, 25.17 to 61.17 ppm, 2.49 to 4.61% and 3.22 to 5.26% of total Fe, Zn, N and K content in leaves, respectively was noted in variety V1; (Faro) from 1st to 12th month of gerbera. Similarly, variety V2 (Dana Allen) gave lowest decrease range (0.94 to 0.50%) of total P content in leaves and variety V1 (Faro) gave highest decreasing range (0.87 to 0.21%) of total P content in leaves from 1st to 12th month of gerbera plant. The treatment M6 (FeSO4 + ZnSO4 @ 0.2% each) was noted highest increasing range of nutrient content in leaves as 45.67 to 70.39 ppm, 27.00 to 62.78 ppm, 2.64 to 4.76% and 3.42 to 5.57% of Fe, Zn, N and K content in leaf during 1st to 12th month of gerbera plant.

Seasonal Abundance of Brevipalpus phoenicis (Acari: Tenuipalpidae) and Its Predators and Their Effects on Gerbera jamesonii Morphology

The objective of this research was to study the abundance and prevalence of Brevipalpus phoenicis and its predators on Gerbera jamesonii Bolus and its relation with different weather variables during a one-year study 2015 at Ismailia Governorate, Egypt. The abundance of B. phoenicis life stages was monitored monthly. The effects of mite's infestation on G. jamesonii morphology represented in leaf, flower, bud and flower deformity numbers during spring was considered, in addition to the photosynthetic pigments. Our results revealed great variations in mite population throughout the year. The highest density ofB. phoenicis adults, eggs, larvae, nymphs were recorded in January (50.25±6.08), May (71.85±8.57), January (31.40±4.71), July (74.43±8.73), respectively while the minimum density were recorded in October (4.10±0.83), September (10.30±2.09), August (1.95±0.46) and (16.10±2.50), respectively. Three predacious mites: Amblyseius cucumeris, Hemicheyletia wellsina, Tydeus sp. and one predacious insect Scolothrips longicornis were recorded.Negative correlations was recorded between B. phoenicis eggs or larvaewith S. longicornis (-0.122, -0.168), respectively. Significant negative correlations were observed between different B. phoenicis life stages, Tydeus sp. and S. longicornis with temperature and relative humidity. There were significant negative or positive correlations between life stages of B. phoenicis and the morphological characteristics of the plant. Highly significant negative correlation was recorded between mite infestation and photosynthetic pigments. In conclusion, G. jamesonii is recorded as a new host for B. phoenicis with a marked deformation in the plant morphology. In addition environmental factors had a great effect on its abundance.

Effect of growing media on growth and flowering of gerbera (Gerbera jamesonii) cultivars under naturally ventilated polyhouse

The performance of gerbera (Gerbera jamesonii Bolus ex Hooker F.) cultivars were evaluated in different growing media in naturally ventilated polyhouse during 2012-13 to 2013-14. Three varieties, viz. Batavia, Faith and Antibes were grown on five different growing media, i.e. partially decomposed rice husk, vermicompost, enriched compost, soil based biofertilizer and control. Growth, flowering and physiological characters were evaluated. The cultivar Antibes was found to be superior with respect to number of leaves/plant (34.57), leaf area index (1.73), net assimilation rate (0.059mg/cm2/day), leaf area duration (55.98 LAI days) and vase life (9.37 days). Among the five growing media evaluated; growth, flowering and physiological characters were better in enriched compost. Number of leaves/plant (36.74), leaf area index (1.86), total chlorophyll content (0.246 mg/g), net assimilation rate (0.064 mg/cm2/day), leaf area duration (58.94 LAI days), days to flower bud visibility (79.18 days), days to full bloom (17.41 days), number of flowers/plant (12.05), diameter of flower (10.29 cm), length of flower stalk (57.47 cm), diameter of flower stalk (0.75 cm) and vase life (10.89 days) of flower were found to be highest for enriched compost.

Organic Composition Analysis and Anatomical Observation in Cut Gerbera (Gerbera jamesonii Bolus) during the Peduncle Elongation Stages

Organic Composition Analysis and Anatomical Observation in Cut Gerbera (Gerbera jamesonii Bolus) during the Peduncle Elongation Stages

Effect of foliar application of Fe and Zn on growth, flowering and yield of gerbera (Gerbera jamesonii) under protected condition

The experiment on effect of foliar application of Fe and Zn on growth, flowering and yield of gerbera (Gerbera jamesonii Bolus) under protected condition was carried out during 2010-2011. The experiment was laid out in Completely Randomized Design (CRD) with three replications comprising six levels of micronutrients, i.e. control (M1), FeSO4 @ 0.2% (M2), FeSO4 @ 0.3% (M3), ZnSO4 @ 0.2% (M4), ZnSO4 @ 0.3% (M5) and FeSO4 + ZnSO4 @ 0.2% each (M6). Growth, flowering, yield and quality attributes influenced by different levels of micronutrients, viz. highest plant height (20.11 and 28.56 cm), plant spread (35.56 and 42.00 cm1) and number of leaves/plant (10.44 and 15.22) at first flower appearance and at full bloom stage, respectively. The number of suckers/plant (3.89) at last harvest, fresh (128.11g) and dry weight (44.11g), flowering span (275.70 days), number of flowers/plant (15.70) and per square meter (157.40) and yield of flowers (15.70 lacs/ha), diameter of flower (11.64 cm), length of flower stalk (54.00 cm) and thickness (6.22 mm), number of florets/ flower (213.33), longevity (16.44 days) and vase life (10.28 days) of flower were significantly highest when micronutrient was sprayed at level of FeSOZnSO4 + ZnSOZnSO4 @ 0.2% each (MZnSO6). Whereas, minimum days to the appearance of first flower bud (48.11) and days to opening the first flower (54.67) were also recorded in MZnSO6 (FeSOZnSO4 + ZnSOZnSO4 @ 0.2% each) level of micronutrient. It is concluded that for the application of FeSOZnSO4 + ZnSO4 @ 0.2% each (M6) at monthly intervals up to 12 months. From economic point of view, it was observed that this treatment was also most profitable as it recorded the highest net returns.

An improvised low cost hardening protocol for in vitro raised plantlets of Gerbera jamesonii

The present investigation comprised two experiments comparing media and containers for optimization of hardening protocol of in vitro raised plantlets of Gerbera jamesonii Bolus. cultivars Rejiko and South Pacific. In one experiment six different media formulations, viz. cocopeat, cocopeat + perlite (1:1), cocopeat + perlite + vermiculite (1:1:1), perlite, perlite + vermiculite (1:1) and vermiculite were tried in six replication completely randomized design. Days to establishment (13.60 and 12.97 in cultivars Rejiko and South Pacific respectively) was significantly lower in in vitro raised plantlets hardened in perlite + vermiculite (1:1) media formulation. Hundred percent (100%) survival of in vitro raised plantlets was achieved in the same media. In the second experiment traditional 500 ml wide mouthed glass bottle was compared with an improvised module devised out of two 250 ml polypropylene glasses-one inverted over the other and joint sealed with a strip of para film. Mean survival rate of 90% in vitro raised plantlets was achieved in polypropylene hardening module as against 70 % in glass bottle containers. Field survival of polypropylene module hardened gerbera plants after 4 and 8 weeks was significantly higher (above 95%) compared to around 70% in plants previously hardened in glass bottles. Vegetative growth in terms of leaf area and leaf number/plant was significantly higher in plants derived from polypropylene hardening modules. The hardening module developed in our study is low cost and can be employed in a variety of crops in low budget tissue culture units that cannot afford expensive hardening facilities.

Vase-life of Gerbera jamesonii Bolus cut flowers depending upon; media, mineral nutrition, their morphological attributes and treatment with flower preservative

The correlations among different media, mineral nutrition and morphological features of gerbera flowers in relation to their vase-life period investigated. The bast medium for longevity of cut gerbera flowers was the mixture of composted pine bark and peat moss fertilized with N – 250 mg/1 and Mg – 150 mg/1. It was found that cut gerberas lasted longer when they were the Alkemade type, i.e. with wide petals. Yellow flowers remained fresh longer than red and pink ones. It was also found that the vase-life period of gerberas directly correlated with the length of floral stalk, its ability to grow and the inflorescence diameter. The solution of flower preservative Proflovit-72 was effective 'in extending life at room temperature and improved the quality and longevity of flowers which were previously in coldstorage for 1 to 3 weeks.

Some pathogenic fungi responsible for the dying of Gerbera jamesonii Bolus

The object of our studies were plants of <i>Gerbera jamesonii</i> Bolus wilting away in a greenhouse of the Botanical Garden in Wrocław. The investigations show that the plants had been destroyed mostly due to a disease caused by <i>Fusarium oxysporum</i> Schl. f. sp. <i>gerbarae</i> Gordon.

English

Genetic diversity within Gerbera jamesonii Bolus is the key to genetic improvement of this important ornamental species. In the present study, genetic diversity of 12 accessions of gerbera was assessed through random amplified polymorphic DNA (RAPD) markers. A total of 40 RAPD primers belonging to OPD, OPE, OPF and OPG series of universal primers set were used out of which, only 10 primers produced clear, reproducible and scorable bands. Ten (10) decamer RAPD primers produced a total of 49 scorable bands from 12 genotypes of G. jamesonii Bolus, out of which 42 were polymorphic and seven were monomorphic. The percentage of polymorphism ranged from a maximum of 100.00% by OPE-02, OPE-14, OPF-18, OPG-18, OPG-16 and OPG-17 to a minimum of 50.00% by OPE-08. The RAPD profiles generated were further evaluated for studying the Jaccard’s similarity coefficient. The average genetic similarity coefficient for the 12 accessions evaluated by Jaccard index was 0.66 ranging from 0.35 to 0.86. The RAPD amplification data were used to obtain similarity matrix and for generation of dendrogram using unweighted pair group method with arithmetic averages (UPGMA) method. Based on the dendrogram, all 12 genotypes could be distinctly divided into two clusters and the accession CF Orange was found most dissimilar from other accessions. This study shows that DNA based molecular marker RAPD is a powerful, less time consuming and cost effective molecular technique for assessment of genetic diversity among different genotypes of G. jamesonii Bolus. The availability of these gerbera RAPD markers would facilitate the use of molecular markers in gerbera breeding and genetic studies.   Key words: Gerbera jamesonii Bolus, molecular markers, genetic diversity, RAPD.

Effect of mulching on growth and flowering of gerbera (Gerbera jamesoniiBolus) cv. Red Gem under Assam Condition

A field experiment was carried out in the Experimental Farm, Department of Horticulture, Assam Agricultural University, Jorhat during 2010–11 and 2011–12 in order to study the effect of mulching on growth and flowering of gerbera (Gerbera jamesonii Bolus) cv. Red Gem under Assam condition. The experiment was laid out in randomized block design (RBD) with seven treatments (viz. black polyethylene mulch, paddy straw, dried leaves, dried banana leaves, water hyacinth, rice husk and control without mulch) replicated thrice. The results showed that black polyethylene mulch produced tallest plant with maximum number of leaves per plant and number of suckers per clump. Same treatment showed earlier flower bud visibility, maximum flower size, flowers per clump and highest length of flower stalk. From the results of this experiment, it can be concluded that black polyethylene much triggers plant growth and development (vegetative growth) and also encourages flower production both quantitatively or qualitatively in gerbera plant.

Evaluation of Commercial Cultivars of Cut Gerbera (Gerbera jamesonii Bolus Ex Hooker F.) under Polyhouse in Shevaroy Condition of Eastern Ghats

An investigation was carried out to evaluate performance of 36 cultivars of cut gerbera (Gerbera jamesoniiBolus ex Hooker F.) in a polyhouse at Horticultural Research Station, Tamil Nadu Agricultural University, Yercaud, during 2008-2010. Significant differences were observed for all the characters studied. Maximum plant-spread (78.02cm) was observed in cv. Robusta. Higher number of leaves was recorded in cv. White Tibet (41.54). Maximum Leaf length and leaf width was recorded in cvs. Golden Gate and Yanara. Maximum number of suckers produced was recorded in cv. Junkfru (7.60). Maximum stalk length was observed in cv. White Tibet (62.62cm), while flower diameter, cut flower production and vase-life were higher in cv. Rosalin. Correlation and path coefficient analysis showed that plant height, number of leaves per plant and number of suckers per plant were the important components of cut-flower yield in gerbera. It may be concluded that cultivars Rosalin, White Tibet, Junkfru and Golden Gate were found to be the best for floral quality and yield, and are recommended for cut-flower production under Shevaroy condition of Eastern Ghats.

First Report of Downy Mildew Caused by Plasmopara halstedii on Gerbera jamesonii in Brazil.

African daisy (Gerbera jamesonii Bolus ex Hook. f.) is an important species for both the cut flower and potted plant industries worldwide (4). Since the winter of 2009, plants showing severe downy mildew symptoms have been observed in a greenhouse located in an experimental area of the Universidade Federal de Viçosa (state of Minas Gerais, Brazil). The disease appeared as ill-delimited adaxial chlorosis of lamina; tissues became yellow and then brown with age with intense blighting of leaves of entire plants, leading to their death, when untreated. Dense, whitish sporulation was observed on the lower surfaces since early stages. A representative sample was dried in a plant press and deposited in the local herbarium under accession number VIC 32070. Slides were prepared with fungal structures mounted in lactofuchsin and observed under a light microscope (Olympus BX 51). Fungus morphology: Sporangiophores hypophyllous, emerging through stomata, cylindrical, up to 650 μm long and 5 to 10 μm wide, with slightly swollen base from 6.5 to 13 μm, hyaline, aseptate, straight, with up to 6 monopodial ramifications occurring mainly at right angles, the final branch ending in 3 or 4 ultimate branchlets; sporangia globose to ovoid, from 20 to 28 μm long and 13 to 18 μm wide, hyaline, smooth. Oospores were not observed. In order to further clarify the identity of the fungus on G. jamesonii, genomic DNA was extracted directly from the plant tissue and part of cytochrome c oxidase subunit 2 was amplified with the primers COX2 (3). The generated sequence was submitted to GenBank (Accession No. KC690148) and when compared with other entries revealed a high sequence similarity (99%) with Plasmopara halstedii (Farl.) Berl. & De Toni (EU743813) from Helianthus annuus L. This was also supported by the morphological data as compared with published descriptions (2) and it was then concluded that the chromistan fungus involved in downy mildew of African daisy was P. halstedii. Two different downy mildew genera, Bremia and Plasmopara, cause downy mildew disease on G. jamesoni. Bremia lactucae has been recorded in Argentina, Brazil, Germany, and Poland (4). There is only one record of a Plasmopara on this host in the United States (1), but this is an obscure report with no identification at the species level. Although P. halstedii has been commonly recorded on numerous hosts belonging to the Asteraceae worldwide, it has never been reported on G. jamesoni. To our knowledge, this is the first report of P. halstedii on G. jamesoni in Brazil. This disease has the potential to become important and cause significant losses because of a combination of the high severity to untreated plants and the increasing importance of African daisy in the flower market in Brazil.

Nonpreference Among Gerbera Cultivars by the Leafminer Liriomyza trifolii (Agromyzidae: Diptera)

The leafminer, Liriomyza trifolii (Burgess) is a key pest of gerbera daisies (Gerbera jamesonii Bolus), which are among the most preferred cut flowers in the world. While insecticides often fail to control this pest, parasitoids have proven to be effective. To maintain the parasitoids in the system, pesticide applications should be avoided. However, the influx of secondary pests like mites, thrips, whiteflies, and aphids during the growing season necessitates chemical sprays, which are effective in controlling the secondary pests, but are often toxic to the natural enemy and hence disrupt biological control. Since chemicals are not easily avoided in this system, an alternative method to avoid leafminers was sought, using host plant resistance, which can be an important component of integrated pest management (IPM) programs. Sixty gerbera cultivars were evaluated for potential resistance to L. trifolii. A range in susceptibility measured as leaf punctures and developing mines was evident for the first five weeks of a six-week exposure period. Gerberas ‘Jaguar Pink’, ‘Jaguar Rose Deep’, ‘Jaguar Salmon Pastel’, and ‘Revolution Spring Pastel’ were the least damaged, exhibiting less than 20% of the highest damage on at least two observation dates. However, consistent exposure to high numbers of leafminers resulted in similar expression of damage among all cultivars after five weeks. Differences among cultivars in force required to puncture leaves could not be consistently associated with damage due to leafminers