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Evaluation of Lisianthus Cultivars for Resistance to Botrytis cinerea
Abstract
Lisianthus (Eustoma grandiflorum) is a high-value cut flower. However, major yield losses often result from gray mold caused by Botrytis cinerea. Various techniques were used to evaluate 12 lisianthus cultivars for resistance B. cinerea. Disease evaluations from detached leaf, leaf disc, cut stem, and in vivo growth chamber stem (GC) assays were correlated with those from an in vivo greenhouse stem (GH) assay, in which commercial greenhouse production of lisianthus was simulated. In all assays, stems or leaves were wounded before inoculation with spores or mycelia of B. cinerea. There was a significant (P <= 0.03) positive correlation between stem lesion length in the GH assay and disease incidence in the same assay (R = 0.74), stem lesion length from spore spray inoculation in the GC assay (R = 0.62), and percent necrosis from spore spray inoculation of detached leaves (R = 0.71). Correlations between stem lesion length in the GH assay and disease evaluations from spore drop and mycelial inoculation of detached leaves, leaf discs, and cut stems were not significant at P = 0.05. Considering only screening methods with significant correlations, 'Magic Champagne' was the most resistant cultivar (mean rank [mr] = 2 of 12). 'Echo White' and 'Echo Lavender' were the least resistant cultivars (mr = 11). The other cultivars were 'Magic White' (mr 4); 'Avila Ivory', 'Balboa Yellow', 'Echo Pink', and 'Magic Rose' (mr = 5); 'Balboa Blue' (mr 6); 'Avila Blue Rim' (mr = 8); and 'Avila Purple' and 'Catalina Purple' (mr = 9). The results from this study indicate that in vivo disease incidence, in vivo stem assays, and detached leaf assays, all initiated with wounding followed by spore spray inoculation, may be more reliable in evaluating lisianthus cultivars for resistance to B. cinerea than spore drop and mycelial inoculation of detached leaves, leaf discs, and cut stems. The results also indicate that lisianthus cultivars with moderate resistance to B. cinerea are commercially available. These cultivars have potential for use as germplasm in breeding lisianthus for resistance to the pathogen.
... These rejections result in immediate economic losses and make cooperation between growers and importers problematical. The problem is equally substantial for roses (Elad, 1988;Elad et al., 1993), gerberas (Salinas & Verhoeff, 1995) and Geraldton waxflowers (Joyce, 1993), although species such as chrysanthemum (Dirkse, 1982), narcissus (O'Neill et al., 2004), lisianthus (Wegulo & Vilchez, 2007), dianthus, ranunculus and cyclamen (Seglie et al., 2009) eventually suffer infections by B. cinerea, but to a lesser extend. ...
... Infection of lisianthus (Eustoma russellianum) flowers has been recently reported by Wegulo & Vilchez (2007). Significant (P ≤ 0.03) positive correlations between stem lesion length of naturally infected plants in the glasshouse (R = 0.74) and stem lesion length of artificially inoculated ones (R = 0.62) with the disease incidence score, and with the percent of necrosis (R = 0.71) of detached leaves were reported (Wegulo & Vilchez, 2007). ...
... Infection of lisianthus (Eustoma russellianum) flowers has been recently reported by Wegulo & Vilchez (2007). Significant (P ≤ 0.03) positive correlations between stem lesion length of naturally infected plants in the glasshouse (R = 0.74) and stem lesion length of artificially inoculated ones (R = 0.62) with the disease incidence score, and with the percent of necrosis (R = 0.71) of detached leaves were reported (Wegulo & Vilchez, 2007). From all the 12 lisianthus cultivars tested, 'Magic Champagne' was suggested as the most resistant and proposed as ideal for commercial cultivation. ...
... Cut flower lisianthus crops are grown in southern Israel for export during the winter. Botrytis cinerea causes gray mold on lisianthus flowers (48,50) and stem bases (49), but no research reports on the etiology and management of this disease in this crop are currently available. Lisianthus is planted from the end of August to mid-October in Israel and the crop grows as single-stem plants to form a dense canopy. ...
... Stem infection is the most devastating symptom of gray mold on lisianthus grown in greenhouses for cut flowers (49). Most stem infections result in plant death (50). ...
... A lisianthus plant has one stem, at the top of which flowers develop (49). Once harvest begins, the stems are removed and a 10-cm-long stem base is left along with the basal rosette leaves. ...
Gray mold, caused by Botrytis cinerea, severely affects the base of the stems of lisianthus (Eustoma grandiflorum) plants as well as the cut stems left after flowers are harvested. This study examined infection of lisianthus plants by B. cinerea under laboratory and commercial greenhouse production conditions typical for Israel and evaluated cultural methods for manipulating disease development in commercial greenhouses. Although the lower nodes of lisianthus stems are typically infected, in this study, the inherent susceptibility of these nodes was less than that of nodes midway up the stem. Greater light intensity (4,860 lux) was associated with significantly more severe stem wounds than lower light intensities of 140 to 1,020 lux. Lower light intensity (140 lux) was associated with significantly more severe leaf infection. The development of gray mold along leaves toward the stem was slower at 26 degrees C than at 18 to 20 degrees C and was fastest at relative humidity (RH) levels close to saturation (>99%). B. cinerea infection developed in all stem wounds exposed to 65 to 99% RH and at temperatures of 12 to 29 degrees C. Infection severity in stem wounds (measured as lesion length) on whole plants was significantly less at 26 degrees C than at 18 or 22 degrees C, and was significantly higher at 99% RH compared with 70 to 85 and 85 to 95% RH. Severity of gray mold was the greatest at 15 to 22 degrees C and 85 to 99% RH. Under commercial greenhouse conditions, supplemental calcium (Ca(NO3)2) applied in fertigation or as a spray led to moderate yet significant reduction in disease severity. In addition, polyethylene soil cover and the use of buried drip irrigation instead of surface drip irrigation suppressed gray mold significantly on cut stems following harvest. Covering the soil with polyethylene also suppressed gray mold significantly as compared with the common practice of growing lisianthus in bare soil.
... Flower production worldwide has always involved the control of pests and diseases due to the susceptibility of the different plant species grown, planting density, among other factors that favor the establishment and multiplication of pathogens that reduce yields (Wegulo and Vilchez, 2007) and generate productive and commercial restrictions. For this reason, pathogen management has focused mainly on the use of chemically synthesized agrochemicals (Radosevich et al., 2020;Solmaz et al., 2020). ...
... This included storage conditions and early virus detection to make early decisions in managing vectors such as aphids and aphids, using integrated strategies with mineral oil and pyrethroid-based insecticides. Likewise, Wegulo and Vilchez (2007) evaluated the resistance of lisianthus cultivars to the fungus Botrytis cinerea, by defining methods for resistance evaluation, and particularly for causing lesions of healthy Lisianthus stems. With this study, it was possible to obtain reliable results and select commercially available cultivars that can be used for the improvement of this crop. ...
The cut flower sector is an area of horticulture that generates great economic and academic interest worldwide, the production of flowers represents a market segment that has aesthetic and sentimental purposes in many regions of the world. In recent years, a large amount of research has been generated that has promoted this sector, therefore, in this work we have proposed to develop a systematic review in this field of knowledge, with the objective of consolidating knowledge, guiding future research, and supporting informed decisions, thus contributing to the efficient use of resources and the continuous advancement of the cut flower industry. The systematic review process was divided into six stages, starting with the definition of the search equation and the collection of information from the prestigious Scopus database. Subsequently, a detailed quality and technical analysis of the 532 documents collected was conducted. These documents were grouped into 13 topics that are related to the production system, ranging from propagation techniques, genome study, genetic improvement to topics of current interest such as sustainability. Each of these topics was examined and the results of this analysis led to the preparation of this technical document, which includes relevant aspects that have contributed to the improvement of productivity and productive diversity in species and under different climatic conditions
... (Wolcan et al., 1996;Vrind, 2005). The symptoms related to grey mould on E. grandiflorum comprise crown rot, damping off, stem cankers, and stem, leaf, and flower blight; grey mould can cause postharvest deterioration of flowers by damaging petals (Wegulo and Vilchez, 2007). Several studies have been performed on the lisianthus-grey mould pathosystem. ...
... Vrind (2005) found that E. grandiflorum was more susceptible to B. cinerea infection compared to rose and gerbera plants. Wegulo and Vilchez (2007) used various techniques to evaluate 12 lisianthus cultivars for resistance to grey mould and found that some commercial cultivars are moderately resistant to B. cinerea in growth chambers and greenhouse conditions. In another study, Shpialter et al. (2009) demonstrated that grey mould development was favoured by air temperatures between 15 and 20°C and 85 to 99% relative humidity (RH); they also observed significantly reduced disease severity at 26°C and 70-85% RH, and when calcium was supplied through fertigation. ...
Lisianthus is an important flower crop susceptible to Botrytis cinerea grey mould. Therefore we studied whether lisianthus plants could be protected with the use of alkamides from the herb Heliopsis longipes against artificially inoculated B. cinerea during pre- and postharvest. Grey mould symptoms on inoculated leaves of lisianthus were decreased three times by pre-treatment with alkamides, compared to untreated, greenhouse-cultured lisianthus. In postharvest stored shoots no protection was observed. Our results show that the exogenous application of alkamides promoted resistance in lisianthus plants against B. cinerea during preharvest but not postharvest storage.
... Es una planta de ciclo anual o bianual, que usualmente se destina a la producción comercial de flor cortada y crecimiento en maceta, es una de las especies con mayor potencial de comercialización a nivel nacional e internacional debido al alto precio de sus flores. Durante los últimos años, en países como Israel, Estados Unidos, Brasil, Argentina y Venezuela; principalmente en el estado Mérida, se ha incrementado la superficie cultivada con lisianto, pero simultáneamente han comenzado a manifestarse enfermedades que pueden convertirse en importantes limitantes para la explotación exitosa de ésta planta ornamental (Cedeño et al., 2007; Shpialter et al., 2007; Wegulo, 2007; Katz et al., 2006; Daughtrey et al., 2000). En junio de 2006, en lisiantos cultivados en invernaderos ubicados en sectores de Plan del Morro y La Pedregosa, localidades pertenecientes al municipio Libertador del estado Mérida, se detectó la presencia de una enfermedad de quema foliar que afectó el 90 % de las plantas de dos meses de edad en una población de 400. ...
... Las dimensiones de los conidios coincidieron con las reportadas por Daughtrey et al. (2000) (8-14 x 6 -9 μm) y Mirzaei et al. (2008) (4-20 x 2-12 μm), mientras que la longitud de los conidióforos se ubicó dentro del rango reportado por Mirzaei et al. (2008) (5274.334 Botryotinia fuckeliana (de Bary) Whetzel, causante de la enfermedad " Moho Gris " en una amplia diversidad de plantas ornamentales y hortalizas (Wegulo, 2007). ...
Lisianthus (Eustoma grandiflorum) now represents one of the ornamental species with the greatest potential for commercialization in Venezuela, especially in the Andean region. In June of 2006, was detected for the first time the fungus Botrytis cinerea and was isolated from stems and leaves of lisianthus grown in areas of Plan del Morro and La Pedregosa, Libertador Municipality of Mérida State. Pathogenicity tests done under greenhouse conditions and subsequent reisolations of the pathogen from artificially infected lisianthus plants; this confirmed that B. cinerea was the causal agent of the foliar blight disease studied. Thirty five days after inoculation, the typical disease symptoms were expressed on all the plants infected experimentally. This is the first report of B. cinerea attacking lisianthus plants in Venezuela.
... y Column means with a letter in common are not statistically different (Fisher's protected LSD; P = 0.05). z Petunia cultivars not included in trial 1. consistency has been reported for B. cinerea on lisianthus (Wegulo and Vilchez 2007) and geranium cultivars (Uchneat et al. 1999) against B. cinerea. ...
Botrytis cinerea causes blight on the leaves, stems, and flowers of petunia (Petunia x hybrida), a popular annual bedding plant. Our objectives were to evaluate: (i) four standard and nine Wave ® petunia cultivars for resistance to Botrytis blight and (ii) ten biorational products compared to the standard fungicide fenhexamid and an untreated control to limit disease. According to the final disease assessment and AUDPC data, ‘Sophistica Blackberry’ had significantly less disease than ‘Tidal Wave ® Cherry’ in all trials. ‘Tidal Wave ® Cherry’ also had significantly more disease according to ratings and AUDPC data than ‘Easy Wave ® Red Improved’, ‘Wave ® Purple Classic’, ‘Tidal Wave ® Silver’, ‘Shock Wave ® Red’ and ‘Easy Wave ® Blue’ in trials 1 and 3, whereas in trial 2 these differences were not observed. When evaluated on ‘Shock Wave ® Red’ petunia, Prestop (Gliocladium catenulatum) provided significant B. cinerea control and was similar to the fungicide standard Decree (fenhexamid) in both trials. According to the final disease severity assessment, treatment with Botector (Aureobasidium pullulans), Zio (Pseudomonas chlororaphis) or LifeGard (Bacillus mycoides) also provided control similar to the fungicide standard but was significantly different from the untreated control in one trial only. Results from this study illustrate that certain biorational products can limit B. cinerea when used in conjunction with a cultivar that has disease resistance that limits the impact of the pathogen. Keywords: Petunia x hybrida, gray mold, fenhexamid, fungicide
... Inconsistencies among the geranium cultivars were observed in this research when the experiment was repeated using similar procedures. Inconsistencies among cultivars in disease caused by B. cinerea were noted in other studies including petunia (Krahl and Randle 1999), lisianthus (Wegulo and Vilchez 2007), and cut roses (Hammer and Evensen 1994;Muñoz et al. 2019). In our research, Multibloom Lavender and Nano Deep Rose had relatively high levels of disease in trial 1 but not in trial 2. Similarly, BullsEye Red and Pinto Pink became more diseased in trial 2 than in trial 1. ...
Botrytis blight caused by the fungus Botrytis cinerea is an important disease of geranium, affecting leaves, stems, and flowers, and decreasing the crop’s marketability. Our objectives were to evaluate (i) susceptibility of geranium cultivars to B. cinerea and (ii) efficacy of biorational products for control of Botrytis blight on geranium. Disease assessment included the number of blighted leaves, foliar lesions, and leaves with B. cinerea sporulation. The area under the disease progress curve (AUDPC) was calculated. Among the ten geranium cultivars evaluated, ‘Pinto Premium Orange’, ‘Horizon Coral Spice’ and ‘Ivy Tornado White’ had significantly less disease than ‘Ringo 2000 Violet’, and ‘Maverick Scarlet Picotee’ for all measured parameters. When eleven treatments were compared in the efficacy trial of biorational products, Botector (Aureobasidium pullulans) and Prestop (Gliocladium catenulatum) effectively controlled the disease according to AUDPC for blighted leaves and leaves with sporulating B. cinerea in both ‘Ringo 2000 Violet’ and ‘Pinto Premium Orange’. Zio (Pseudomonas chlororaphis), Serifel (Bacillus amyloliquefaciens), Serenade Opti (B. subtilis) and LifeGard (B. mycoides) were also effective when combined with the geranium cultivar Pinto Premium Orange, one of the least susceptible cultivars in our study based on AUDPC values for all measured parameters. AUDPC for leaves with sporulating B. cinerea showed that all biorational products included in the study effectively limited B. cinerea except Actinovate (Streptomyces lydicus) in ‘Pinto Premium Orange’ geranium. A sustainable management approach could combine one of the least Botrytis susceptible geranium cultivars identified with biorational controls for effective Botrytis blight control.
... From each treatment, 4 representative leaves of each crop and treatment were taken. Four discs were extracted from each leaf and taken to a controlled environment for their corresponding inoculation (if applicable), measurement and evaluation of the growth of B. cinerea following the procedure described by Wegulo and Vilchez (2007) and (Pozo et al., 2015). The discs extracted from + Si and -Si plants were deposited in Petri dishes boxes. ...
The benefits of silicon for different plant species have been described in many studies in both soilless and traditional soil culture systems. The aim of this work was to quantify the effect of Si on leaf cuticles under different fertigation regimes and the relationship of this effect to water, potassium and nitrate absorption, vegetative growth and plant protection. Cucumber, melon and pepper plants were transplanted into coconut fiber containers with Si in the nutrient solution at 0.6 mM (+Si) and without Si (-Si) under optimal fertigation (OF) and moderate deficit fertigation (DF) conditions. Absorption of water, nitrate and potassium, vegetative growth, leaf firmness, loss of water through cuticle transpiration, cuticle thickness, number of trichomes and Si content in the epidermis and trichomes were measured. Trichome numbers, cuticle thickness and Si content were examined using light and SEM microscopes equipped for X-ray microanalysis. Resistance to two pathogens, Botrytis cinerea and Erysiphe cichoracearum, was also measured. The results show a loss of growth in the three cv. under DF that was alleviated when Si was supplied in the nutrient solution. +Si significantly improved water absorption and decreased leaf loss, which may explain the improvement shown in the growth parameters. +Si showed clear and significant growth increases in both the epidermis and the cuticle, which could justify both the observed greater resistance to diseases and the lower rates of water loss from the leaves. The three cv. showed high concentrations of Si in the trichomes, even under-Si treatments with a mean Si concentration lower than that in the +Si treatments.
... In 2005, the total wholesale value of Lisianthus in the United States for operations with sales worth $ 100,000 or more was $ 4.89 million, with California accounting for 89.4 % of those sales [8]. Most cut flower cultivars of Lisianthus are multiplied by F1 hybrid seeds and sold for cultivation. ...
Lisianthus [Eustoma grandiflorum (Raf.) Shinn.], a member of the family Gentianaceae, is native to the central and southern part of United States. Lisianthus is a relatively new floral crop to the international market, quickly rankes in the top ten cut flowers worldwide due to its garish flowers and excellent post-harvest life. Due to its importance there are several tissue culture studies working on the micropropagation of this plant by using a variety of plant growth regulators (PGRs). With the aim of contribution to these works in the present study we aimed to investigate the effect of Gibberellic acid (GA3) at different concentrations (0.0, 0.5, 1.0, 2.0 and 4.0 mg l-1) on morphometric parameters of Lisianthus during 30 and 80-day of incubation periods. In sum, our findings revealed that according to the results, there was no significant change for shoot number, shoot length and root number but very slight increase in number of leaves (1.0 mg l-1) and root length (0.5 mg l-1) of GA3 during 30-day incubation period. On the other hand, for 80-day incubation period, the highest root length and number of leaves were obtained (respectively, 2.48 ± 1.25 cm and 14.17 ± 4.59) for 2.0 mg l-1 concentration. In addition, shoot length to be found at the highest rate for 1.0 mg l-1 (3.32 ± 0.34 cm). 80-day incubation period was found to be more effective than in comparison to 30-day incubation period in terms of number of leaves, shoot and root length.
... Symptoms of gray mold on lisianthus are reported as crown rot, damping off, stem cankers, and stem, leaf, and flower blights. Gray mold also can cause postharvest deterioration of flowers (Wegulo and Vilchez 2007). Botrytis blight can be a very destructive disease for growers of cut liliums (L. ...
Pre- and postharvest disease control for ornamental plants is mainly provided via fungicide or bactericide application. However, disease control with conventional chemical compounds carries the risk of resistance development by new pathogen races. Additionally, there is increasing public concern over fungicide usage in terms of human and environmental risk. For this reason, and over the past 20 years, researchers developed novel postharvest disease management strategies for cut flowers and other ornamentals. For example, the generally recognized as safe host defense inducers may provide an alternative solution to socially and environmentally less desirable control using conventional fungicides. There are also various biological agents and microorganisms that affect disease development via antagonism and, in many cases, help in integrated disease management (IDM) strategies. However, most of those biotic and/or abiotic agents have not yet been put into practice by growers, who merely rely on chemical control. The current chapter offers an overview on postharvest disease management of various pathogens infecting ornamental plants and cut flowers.
... Inconsistency in cultivar reaction to pathogens in various pathosystems has been reported in previous studies. Wegulo and Vilchez (2007) found rankings of lisianthus (Eustoma grandiflorum) cultivars to fluctuate between evaluation methods when the cultivars were screened for resistance to Botrytis cinerea. In a separate study, Wegulo et al. (1998) similarly found rankings of soybean (Glycine max) cultivars to fluctuate between evaluation methods when screened for resistance to Sclerotinia sclerotiorum. ...
Powdery mildew caused by Erysiphe aquilegiae var. ranunculi is one of the major diseases affecting field-grown delphiniums (Delphinium spp.). Two lath house and two field experiments were conducted in 2003 and 2004 to evaluate nine delphinium cultivars for resistance to the disease. 'Blue Bird', 'King Arthur', 'Cameliard', and 'Galahad' were consistently more resistant [0-1.1 disease severity (ds) on a 0-5 scale] than 'Casa Bianca', 'Blue Shadow', 'Belladona', and 'Bellamosum' (2.9-5.0 ds). Oriental Blue' was moderately resistant (0-3.3 ds). Spearman's coefficients of rank correlation were significant for all pairs of experiments (0.70 ≤ rs ≤ 0.98; P ≤ 0.0354) except for the 2003-04 field experiments (rs = 0.66; P = 0.0525). Pearson correlation coefficients between experiments (0.86 ≤ r ≤ 0.99) were highly significant (P ≤ 0.0027). Disease severity values from lath house evaluations were almost identical to those from field evaluations.
... Lisianthus ( Eustoma grandifl orum ) is a cut fl ower crop that is susceptible to infection by B. cinerea (Shpialter et al. 2009 ), which causes grey mould on the harvested fl owers and stem bases and on the stem stubs after harvest (Shpialter et al. 2009 ;Wegulo and Vilchez 2007 ), especially in unheated greenhouses. The lower leaves of lisianthus plants are often in close contact with the wet soil. ...
Epidemics of Botrytis-incited grey mould are common in open fields, orchards and greenhouses. These infections are promoted by high humidity and the presence of a film of water on susceptible plant organs and those conditions may be manipulated to prevent infection. Traditionally, heating greenhouses was a popular means of controlling the humidity in those structures and this practice remains popular in some temperate regions. However, the cost of active heating has forced farmers in some regions to abandon this disease-management strategy, which has led to the increased incidence and severity of grey mould, as susceptible organs of the crop plants remain wet for longer periods of time. Cultural methods for controlling Botrytis-incited disease include reducing the planting density, managing the crop canopy to allow for the aeration of the crop or susceptible organs via passive and active ventilation, fertigation with increased levels of potassium and calcium and reduced amounts of nitrogen, the use of soil mulch and passive solar heating of unheated greenhouses, avoiding harvesting on rainy days, and timing fungicide applications for the optimal protection of fresh harvest wounds and so that the crop remains wet for shorter periods of time. Row and field positioning and direction can affect grey mould as these factors affect local air movement and temporal temperature changes. A combination of treatments can provide better grey mould suppression than individual treatments and appropriate integration of control measures can provide sufficient disease control with minimal use of chemical fungicides.
Ornamental production systems are complicated to manage due to the many species and genera that may be grown and handled together on a single production site. Ornamentals are threatened by various phytopathogenic fungi in greenhouse and field production. Among these, Botrytis cinerea is one of the most notorious pathogens of ornamentals, specifically cut flowers. B. cinerea is responsible for causing Botrytis blight disease in both pre- and post-harvest conditions. The pathogen infects leaves, stems, flowers, etc., and causes petal specking, flower blight, sepal yellowing, and peduncle bending, among other symptoms. The ability of B. cinerea to cause disease in greenhouses and fields, as well as in subsequent handling, storage, and transportation, makes this fungus an important pathogen due to its potential negative economic effects on the cut flower industry. For the management of B. cinerea, the routine application of fungicides is considered a major tool in commercial production. However, fungicide resistance, phytotoxicity, application residues, environmental concerns, and health issues have forced growers to seek alternative management approaches. In this review paper, we discuss the different approaches (classic to novel strategies) used for B. cinerea management, including chemical methods and their modes of action. The integration of new practices with existing management strategies (sanitation, nutrition, plant regulators, botanical extracts, biological control, fungicides) could provide effective results in ornamental production systems. Understanding the ecology of pathosystems, disease epidemiology and the integration of all possible management measures as a system approach may also provide adequate disease suppression in both pre- and post-harvest conditions.
Nematode parasitism is a yield limiting factor in many cropping systems, including potato production, which can translate into substantial economic losses. These impacted financial returns are simply calculated by subtracting the cost of production from total revenue (yield times the price per yield of potatoes). The production costs can include, but are not limited to, chemical and biological control agents. To assess economic returns associated with different nematode management strategies, we evaluated complete cost estimations for a representative commercial potato farm in central Michigan, USA. Economic returns were calculated using stochastic parameters for two biological control agents (MeloCon and Majestene), six chemical controls (Mocap, Movento, Nimitz, Velum and Vydate), and two soil amendments (poultry and dairy manure). Evaluated costs included stochastic estimations for price per unit weight of potatoes, fuel, labour and production land rent. Yield data from three field trials were used to create empirical distributions. Using yield data and stochastic cost estimations, we generated 500 simulations of net returns per treatment. The top three average returns were obtained from the use of Mocap, Nimitz and poultry manure. Velum, Movento, dairy manure and Vydate also gave returns significantly higher than no treatment at all; however, the biological nematicide, Majestene, showed negative returns. This simple financial model is a crucial layer of analysis on the performance of nematicides that can be adapted to advise growers through Agricultural Extension activities and needs to include the evaluation of biological control agents.
Lisianthus, Eustoma grandiflorum (Raf.) Shinn., is an important cut and potted flower that has been in increasing demand over the last three decades. Its profitability can be decreased by failure to maintain demanding propagation and production requirements and by numerous diseases. Particularly challenging lisianthus diseases are caused by Botrytis cinerea, Fusarium spp., and an ever increasing number of viruses, especially the tospoviruses. Management strategies for lisianthus diseases recently studied include chemical, biological, cultural, and physical control, host resistance, and their integration.
The silicon (Si) percentage in the dry matter of plants is between 0.1% and 10%,and even though its role in the metabolism of plants is not absolutely clear, Si’s positive effects on plant nutrition and plant protection against both biotic and abiotic stress are well documented. However, Si is not considered to be an essential element, so it is not always present in nutrient solutions. In this paper, an experiment was carried out in the University of Almeria’s greenhouse with hydroponic lettuce, tomato, pepper, melon, and cucumber plants. A standard nutrient solution was used as a control sample and was fertigated with Si. During the four-true-leaf seedling stage, various plant growth parameters were measured, including the dry weight and the wet weight as well as the
foliar surface and the cuticle thickness of both the leaf and the stem. Additionally, in the lettuce, tomato, and pepper plants, the effect of the use of Si in the nutrient solution on the protection against the pathogen Botrytis cinerea was determined by measuring the penetration of the pathogen through the cuticle and the extension of the fungal infection by using leaf discs. The results suggest that all of the studied parameters, and both the
cuticle thickness and the epidermis thickness, were increased by more than 10% on average for all of the plants. In the lettuce, tomato, and pepper plants, a beneficial effect against B. cinerea was observed when the nutrient solution containing Si was used.
Hybrid lisianthus [ Eustoma grandiflora (Raf.) Shinn.] was evaluated as cut flower and flowering pot plants. Lisianthus is a day neutral summer blooming plant blooming earlier at high growing temperatures (18°/26°C night/day) than at low temperatures. It is a slow growing plant, requiring about 5 to 6 months from sowing to flowering. Forcing period is about 2 months. Three color variants are available: blue, pink, and white. Only the blue and white are suitable as cut flowers. About 3 cut flower stems are produced per plant in the 1st harvesting cycle, and retaining the plant for a 2nd crop is considered uneconomical. Keeping quality of the cut flowers can be improved by pulsing for 24 hr with a solution containing 5% to 10% sugar, and desirable blue and pink pot plants were obtained by spraying with butanedioic mono-2.2-dimethylhydrazide (daminozide, B-Nine). The white cultivar did not respond to daminozide but did respond to soil application of a-cyclopropyl-a-(p-methyoxyphenyl)-5-pyrimedine methyl (ancymidol). Flowering pot plants should be grown in the greenhouse until about half of the flower buds on the plants open, since buds do not develop properly under home conditions.
Twenty-five strawberry cultivars and advanced selections were ranked according to their field susceptibility to fruit rot caused primarily by Botrytis cinerea Pers. ex Fr. it was apparent that the resistant cultivars, ‘Shuksan’, ‘WSU 1140’ and ‘WSU 1142% derived their resistance from ‘Columbia’ and ‘Molalla’. Among the most susceptible cultivars were ‘Cheam’, ‘Cambridge Vigour’, ‘Northwest’ and ‘Marshall’. There was no apparent relationship between the incidence of fruit rot and yielding ability although 3 cultivars, ‘Shuksan’, ‘WSU 1140’ and ‘WSU 1142’, combined fruit rot resistance with high yields.
A detached leaf disk assay for screening sweet cherry (Prunus avium L.) genotypes for susceptibility to powdery mildew (PM) [Podosphaera clandestina (Wallr.:Fr.) Lev.] was developed by evaluating the effects of photoperiod (24 hours light, 0 hours light, 14 hours light/10 hours dark), substrate nutrient content (sterile distilled water, 1% sucrose), leaf age (old, young, emergent), and leaf explant size (intact leaf, 30 mm, 20 mm) on PM growth on leaves from the susceptible cultivar Bing. The only parameter described that had a significant (P ≤ 0.001) effect on PM growth was leaf age. Old leaves, designated as the third fully expanded leaf from the basal end of current-year's shoot growth, were never infected with PM under controlled inoculations. In the absence of significant differences between treatments, those parameters with the highest treatment means were selected for subsequent evaluation. To test the leaf disk assay, 14 sweet cherry cultivars were screened in two experiments, and rated according to level of PM susceptibility. Rank sum comparison of results from cultivars used for leaf disk screening agreed with earlier field rankings of the same cultivars. The developed leaf disk assay greatly reduced the space required to screen sweet cherry cultivars, and was a repeatable and objective predictor of field resistance that may be useful for screening germplasm or breeding populations.
Three methods to identify levels of resistance to Sclerotinia sclerotiorum in soybean (Glycine max) and dry bean (Phaseolus vulgaris) were compared using multiple data analyses. The three methods were mycelial plug inoculations of cotyledons, cut stems, and detached leaves. Six S. sclerotiorum isolates of known relative aggressiveness were inoculated on each of three soybean and dry bean cultivars with varied response to S. sclerotiorum. For soybean, all three inoculation methods accurately identified isolate aggressiveness irrespective of cultivar, but identification of susceptible and partially resistant soybean cultivars was influenced by isolate. For dry bean, the cotyledon and cut stem methods accurately identified isolate aggressiveness, but identification of susceptible and partially resistant dry bean cultivars was influenced by isolate and inoculation method. The cut stem method had the smallest coefficient of variation and was more precise for detecting interactions. When considering root mean square residual error combined over species and experiments, coefficient of variation based on residual error, significance of isolate-by-cultivar interaction from ANOVA, rank correlation between pairs of methods, and sensitivity ratio for the three resistance screening methods under controlled environmental conditions, the cut stem method was statistically better than the cotyledon and detached leaf methods for evaluating resistance in soybean and dry bean cultivars.
Fusarium crown and stem rot, caused by Fusarium avenaceum (Fr.:Fr.) Sacc., is a serious disease of lisianthus (Eustoma grandiflorum Raf. (Shinn)). While more than 80 new cultivars of lisianthus have been released for sale in the United States in the last decade, there is a lack of information on their susceptibility to this pathogen. Forty-six cultivars of lisianthus were evaluated for their response to infection by F. avenaceum. Cultivars were grouped according to blue/purple, pink, or white flower colors and evaluated within their color class. Although some plants of all cultivars were susceptible to F. avenaceum, partial resistance was observed as indicated by differences in the length of time to symptom express and in the frequency of diseased plants within each color group. In 21 of the 46 cultivars, 80 to 100% of the plants expressed symptoms within 55 days after inculcation. The lowest frequencies of diseased plants 55 days after inoculation were found in 'Ventura Deep Blue' and 'Hallelujah Purple' (25%), 'Bridal Pink' (23%), and 'Heidi Pure White' (53%) for the blue/purple, pink, and white flower color groups, respectively. Screening cultivars for resistance to F. avenaceum is the first step in breeding resistant cultivars. The methods we developed for these studies should be useful in screening for resistance. These results also ay help growers select cultivars that are less susceptible to F. avenaceum, which should aid in the management of this disease. Fusarium crown and stem rot is one of the most damaging diseases of lisianthus. It has been reported as a disease of lisianthus produced as potted plants and cut flowers (Koike et al., 1996; Ozaki, 1992), but has been especially devastating in cut flower production.
Many cut flower growers in Florida produce crops directly in the field, subjecting them to soil-borne diseases and root-knot nematode infection. Seven cultivars of cut flowers were tested for their susceptibility to two races of the southern root-knot nematode (Meloidogyne incognita) in a greenhouse. Cultivars evaluated were 'Potomac Royal' snapdragon (Antirrhinum majus), 'Madonna Blue' blue lace flower (Didiscus caeruleus), 'Green Mist' and 'Queen of Africa' white dill (Ammi majus), 'Qis White Cut' larkspur (Consolida ajacis), and 'Avila Rose Rim' and 'Echo Pink' lisianthus (Eustoma grandiflorum). Cultivars of lisianthus and larkspur tested were relatively poor hosts to M. incognita races 1 and 2 as compared to the known susceptible host, snapdragon (P < 0.05). Based on number of nematodes extracted per gram of root tissue, 'Madonna Blue' blue lace flower was more susceptible, 'Green Mist' white dill was equally susceptible, and 'Queen of Africa' white dill was less susceptible than snapdragon (P < 0.05). Numbers of nematodes per gram of root were not different for M. incognita races 1 and 2 (P > 0.05) on any plant cultivar. Despite differences in nematode susceptibility, numbers of flowers, and shoot and root weights of all cultivars tested except 'Madonna Blue' were not affected by nematode inoculation. Meloidogyne incognita race 1 reduced the number of flower buds and shoot weight of 'Madonna Blue' compared to the control, indicating that this blue lace flower cultivar is intolerant to this nematode.
Sclerotinia stem rot of soybean [Glycine max (L.) Merr.], caused by the fungal pathogen Sclerotinia sclerotiorum (Lib.) de Bary, recently has increased in importance in the northern U.S. soybean production area. The objective of our study was to determine the effectiveness of three different inoculation techniques in predicting the field reactions of cultivars to sclerotinia stem rot. Eighteen soybean cultivars were field tested in six Michigan environments from 1994 to 1996 and tested in the greenhouse or laboratory with three inoculation methods. The cultivars were inoculated by placing infested oat (Avena sativa L.) seed or mycelial plugs on cotyledons or by placing mycelial plugs on detached leaves. There were significant (P < 0.05) differences in resistance to sclerotinia stem rot among cultivars at all but one field environment and for all inoculation methods. The disease severity ratings based on the inoculations were significantly correlated with the field results, with the exception of one method. Disease severity ratings for the three inoculation methods were significantly correlated with only two exceptions. Cultivars such as Novartis S19-90 and Corsoy 79 consistently had the lowest disease severity ratings in the field tests and for the inoculation methods. Similarly, a number of cultivars were rated as susceptible in all tests. Ratings for cultivars with intermediate reactions were not consistent across tests. The inoculation methods tested can provide some useful information on the resistance of soybean genotypes to sclerotinia stem rot. However, resistance identified by inoculation methods should be confirmed with field tests, since these methods can misclassify the resistance of some cultivars.
The responses of 12 soybean cultivars to Sclerotinia sclerotiorum were evaluated under field and controlled environment conditions. The 12 cultivars were planted in fields naturally or artificially infested with S. sclerotiorum and evaluated for disease incidence. In controlled environment studies, the cultivars were compared with respect to lesion size on detached leaves and stems inoculated with mycelial disks, incidence of stem rot following mycelial inoculation of foliage, lesion lengths on stems discolored by oxalic acid, and levels of soluble pigment(s) in stems. Significant differences (P less than or equal to 0.05) in disease incidence, lesion sizes, and levels of soluble pigment(s) were detected among the 12 cultivars in all evaluations, but ranking of cultivars varied among methods and experiments within methods. Corsoy 79 and S19-90 were consistently most resistant in all methods; whereas Kenwood, A2242, Bell, and Williams 82 were least resistant. Pearson correlation coefficients (R) for disease incidence between location years in field experiments (FE) ranged from 0.86 to 0.95. R values between FE and controlled environment experiments (CEE) ranged from 0.01 to 0.62 for detached leaf assays (DLA), -0.20 to 0.47 for lesion lengths on stems inoculated with mycelial disks (LLM), 0.38 to 0.45 for incidence of stem rot from mycelial inoculation of foliage (MIF), 0.08 to 0.66 for lesion lengths on stems discolored by oxalic acid (LLO), and -0.55 to -0.37 for levels of soluble stem pigment(s) (SSP). Absolute values of R between FE and CEE were 0.40 or greater in 40, 17, 33, 29, and 83% of all correlation analyses for DLA, LLM, MIF, LLO, and SSP, respectively. Spearman's coefficients of rank correlation (r(s)) between FE and CEE based on average performance were 0.55, -0.20, 0.40, 0.42, and -0.44 for DLA, LLM, MIF, LLO, and SSP, respectively. Disease development was slow when foliage was inoculated with a mycelial suspension. Based on experiment (E) by cultivar (C) interaction and r(s) values between replicate experiments within each method, determination of soluble stem pigment levels (0.86 less than or equal to r(s) less than or equal to 0.97; P < 0.001 for 100% of six analyses; P = 0.98 for E x C interaction) and measurement of lesion lengths on stems discolored by oxalic acid (0.27 less than or equal to r(s) less than or equal to 0.85; r(s) greater than or equal to 0.58 and P less than or equal to 0.05 for 68% of 28 analyses; P = 0.07 for E x C interaction) were the most repeatable methods. The results from this study suggest that determination of levels of soluble pigments in stems, measurement of lesion lengths on stems discolored by oxalic acid, and the detached leaf assay may be better than mycelial inoculation of stems or foliage in evaluating soybean cultivars for field resistance to S. sclerotiorum.
To evaluate resistance to stem rot, commercial soybean cultivars were grown in a greenhouse without fertilizer for 5 wk, then cut apices of excised plants with leaves and stem apices removed were inoculated with mycelial disks from cultures of Sclerotinia sclerotiorum grown for 5 days on millet seed agar. The inoculated stems were incubated on moist vermiculite in trays at 2022C. The trays were covered with aluminum foil for 3 days, then exposed to ambient light on a laboratory bench. Lesion lengths were measured after 7 days. Commercial soybean cultivars of maturity groups 0, I, II, and III differed in their responses to stem rot with the laboratory method, but results of different experiments often were not consistent. The same cultivars also were tested in an infested field. Disease incidence ranged from 2.2 to 40% in 1984 and from 0 to 52% in 1985. The disease reactions of 13 cultivars tested in both years were significantly correlated (r = 0.72) with each other. Seed yields of 16 cultivars in 1985 were inversely correlated with stem rot incidence (r = 0.94). For every 10% increase in disease from 0 to 52%, yield was reduced by 7.8% of the maximum yield of 3,024 kg/ha (45 bu/acre). Lesion lengths in commercial cultivars assessed by the laboratory method showed varying correlations with disease incidence in the field experiments (r = 0.170.86). Ten cultivars of field-grown plants subjected to the laboratory assay gave reactions significantly correlated (r = 0.68) with field reactions of those cultivars.
Erysiphe pisi is the widely distributed causal organism of powdery mildew of pea (Pisum sativum), an economically important disease in western Canada. This study was conducted to examine the variability for virulence in naturally occurring populations of E. pisi. In 1995, 31 single-colony isolates of E. pisi were isolated and tested on a set of 14 pea lines using a detached leaf assay. Some variability was evident, as isolates PUI-2 and LAI-1 were slightly virulent on the resistant lines Highlight and JI 82, respectively. Other isolates caused similar reactions in all the tested lines. Ten of the 14 pea lines were evaluated in Manitoba, Canada; New York and California, USA; Norwich, UK; and Kathmandu, Nepal. Disease reaction of the tested lines in Nepal exhibited some differences compared to other test locations, indicating variability in virulence of the pathogen. Seven pea cultivars/lines, Highlight, JI 2480, JI 1559, JI 210, JI 82, Radley, and JI 1758 are suggested for use as differential lines for future studies.
The feasibility of using a detached leaflet assay for disease assessment of ascochyta blight on chickpea was examined by comparing disease severity values for inoculated plants with disease severity and disease incidence values for inoculated detached leaflets floating on water in petri plates. Three isolates of Ascochyta rabiei, collected in Turkey, and representing races 1, 4, and 6, were tested on six chickpea cultivars. For young detached leaflets (most recent fully expanded leaves), there was a high positive correlation of disease severity, or disease incidence, values with disease severity values for intact plants. The resistant or susceptible category for each cultivar in relation to each race was not changed by assay on young detached leaflets, but for older leaflets (from the first or second oldest leaves) a susceptible rating sometimes was altered to a resistant rating.
A detached leaf disk assay was developed for screening sour cherry (Prunus cerasus) cultivars for resistance to cherry leaf spot (Blumeriella jaapii). This assay was used to characterize the events occurring in cv. Montmorency (susceptible) and cv. GiSelA 6 [GI 148-1] (resistant) host-pathogen interactions, and to develop a disease scoring scheme to categorize disease severity in sour cherry trees. Forty-three seedlings grown from seeds collected in Russia were screened for resistance using the scoring scheme. Cross infection studies were also carried out with leaf spot isolates from four other Prunus species. These studies were made possible by the development of a new method of culturing B. jaapii isolates, using cherry fruit agar. This method enabled large amounts of inoculum to be produced within 2 weeks rather than a couple of months as required previously. In 'Montmorency', disease symptoms were first observed 4 days postinoculation (dpi), with the appearance of small white spots on the undersides of inoculated leaves. These spots gradually grew, producing erumpent spore masses in acervuli approximately 7 dpi. In 'GI 148-1', disease symptoms were also first observed 4 dpi, with the appearance of small transparent lesions. In the majority of cases, these lesions did not increase in size; however, acervuli occasionally were formed approximately 8 dpi. These contained small cirrhi and were often surrounded by an abscission zone. Of the sour cherry seedlings tested, only 'Almaz' open pollinated (o.p.) R1(1) was rated as resistant. 'Almaz' o.p. R1(1) and 'GI 148-1' were also rated as resistant to leaf spot isolates from other Prunus species. These results and the implications for breeding resistant sour cherry cultivars are discussed.
A simple method was developed to screen apple cultivars for resistance to Venturia inaequalis using detached leaves from in vitro-propagated shoots. Leaves of 6 cultivars either susceptible or resistant to V. inaequalis were placed on Petri plates containing water agar or wet Whatman filter paper, and were inoculated with non-axenic conidial suspensions. Light microscopy studies indicated that the reaction of resistant and susceptible cultivars in vitro mimicked reactions in the greenhouse and field. Susceptible cultivars showed chlorosis 3 weeks after inoculation, and became necrotic after 5 weeks. Leaves from resistant cultivars showed no symptoms. On susceptible cultivars grown in vitro, multiple appressoria formed per spore, the mycelia proliferated above the cuticle on the surface of the leaf, and sporulation occurred 3–4 weeks after inoculation. The simplicity of this detached leaf assay allows not only selection from much larger plant populations than is currently possible with greenhouse and field techniques, but also makes possible the preservation of the mother plant during identification of resistant apple clones. This assay could be useful for studies of host-pathogen interactions.
A Manual of Assessment Keys for Plant Diseases. Canada Department of Agriculture Publication No
- C James