Bioprospecting of Saprobe Fungi from the Semi‐Arid North‐East of Brazil for the Control of Anthracnose on Sorghum

Anthracnose, caused by the hemiotrophic fungus Colletotrichum sublineolum, is one of the most important diseases affecting sorghum production worldwide. The main goal of this study was to select saprobe fungi from the semi‐arid north‐east of Brazil that could increase sorghum resistance to anthracnose and investigate this increased resistance at both physiological and biochemical levels. Plants were sprayed with Curvularia inaequalis, Gonytrichum macroladum, Memnoniella levispora, Pithomyces chartarum, Periconia hispidula, Phaeoisaria clematidia, Dictyochaeta heteroderae, Sarcopodium circinatum, Periconia byssoides, Moorella speciosa, Stachybotrys chartarum, Pseudobotrytis terrestres, Memnoniella echinata, Stachybotrys globosa and Gonytrichum clamydosporium 24 h before inoculation with C. sublineolum. Plants sprayed with water served as the control treatment. The area under the anthracnose progress curve was significantly reduced in comparison with the control treatment only for plants sprayed with C. inaequalis. Therefore, C. inaequalis was selected for physiological and biochemical evaluations. The peroxidases, chitinases and β‐1,3‐glucanases activities were significantly higher for plants sprayed with C. inaequalis and inoculated with C. sublineolum than for plants not sprayed with C. inaequalis and inoculated with C. sublineolum. There was no apparent decrease in the values of net carbon assimilation rate, stomatal conductance to water vapour or transpiration rate for plants sprayed with C. inaequalis and infected by C. sublineolum in comparison with plants not sprayed with C. inaequalis and infected by C. sublineolum. In conclusion, sorghum resistance against C. sublineolum infection was greatly potentiated by C. inaequalis without any apparent change in the photosynthetic capacity of the infected plants.     

Leaf gas exchange and chlorophyll a fluorescence in soybean leaves infected by Phakopsora pachyrhizi

Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, is one of the most important foliar diseases affecting soybean production worldwide. This study aimed to investigate the photosynthetic performance (leaf gas exchange, chlorophyll (Chl) a fluorescence images and photosynthetic pigment pools) of soybean plants sprayed with Acibenzolar‐S‐Methyl (ASM) and the fungicide epoxiconazole + pyraclostrobin (Epo+Pyr) and further inoculated with P. pachyrhizi. The ASR symptoms progressed much faster on the leaves of plants from the control treatment (water spray) in comparison with the ASM and Epo+Pyr treatments. In general, the values for the leaf gas exchange parameters net carbon assimilation rate (A), stomatal conductance to water vapour (g_s), internal CO₂ concentration (C_i) and transpiration rate (E) increased for the infected plants sprayed with ASM or Epo+Pyr in comparison with plants from the control treatment. The values for the initial fluorescence (F_o), maximal fluorescence (F_m), maximal photosystem II quantum efficiency (F_v/F_m), effective photosystem II quantum yield (Y(II)) and quantum yield of regulated energy dissipation (Y(NPQ)) were consistently higher for the ASM and Epo+Pyr treatments in comparison with the control treatment at advanced stages of fungal infection. By contrast, the values for quantum yield of non‐regulated energy dissipation (Y(NO) were significantly lower for the ASM and Epo+Pyr treatments. The concentrations of total Chl a+b and carotenoids significantly increased for infected plants sprayed with ASM and Epo+Pyr in comparison with plants from the control treatment. The results of this study demonstrated that the spray of soybean plants with either ASM or Epo+Pyr contributed to reduce the negative effect of ASR on the photosynthesis of soybean plants.     

Seasonal Dynamics of Black Leaf Mould (Pseudocercospora fuligena) on Greenhouse‐Grown Fresh Market Tomatoes

Black leaf mould (BLM), caused by Pseudocercospora fuligena, is a major fungal foliar disease of greenhouse‐grown tomatoes in the humid tropics. Quantifying the disease and yield loss from seasonal plantings will help mitigate the heavy reliance on frequent sprays of curative fungicides. In this study, severity of BLM was investigated in sequential plantings of tomatoes in two 50‐mesh BioNet greenhouses in central Thailand from June 2005 to January 2007. Each planting consisted of a block of six plants that received two applications of mancozeb and another block of six plants with no fungicide application at all. Two BLM peak epidemic periods were identified, that is, from plantings that were started in August–September and in January. On average, a yield loss of 30.6% was recorded from the two peak epidemic periods based on comparison of fungicide‐sprayed and non‐sprayed plants. Two sprays of mancozeb resulted in 71.6% reduction in disease severity during these peak epidemic periods. Mean disease severity (DS*) was highly correlated with a favourability index of relative humidity (RH), which was quantified on a scale of 0 (<85%, non‐favourable) to 1 (≥85%, extremely favourable). A three‐parameter logistic function explained the data well (R² = 0.81, P < 0.0001). Marketable yield (MY) was positively correlated with maximum plant height (PH_max) but negatively correlated with DS*. In addition, MY was higher from plantings during October to December. It was predicted well (R² = 0.60; P < 0.0001) using the model MY = (a + b × PH_max) × (1‐c × DS*), which combined both PH_max and DS*. Using this model, a reduction of 1.05% in marketable yield was predicted for each 1% increase in mean disease severity. The outcomes of this study implicated the need for management of RH and critical relevance of protecting tomato plants against BLM when they are grown during the peak epidemic periods.     

Silicon and Fungicide Effects on Anthracnose in Moderately Resistant and Susceptible Sorghum Lines

This study aimed to evaluate the effect of silicon (Si) and its interaction with fungicide on the management of sorghum anthracnose. The experiments were carried out in Si‐deficient soil in the 2008/2009 and 2009/2010 growing seasons in a randomized, complete block, split‐split plot design with four replications. Calcium silicate (CS) and lime (L), at the rates of 6 and 5 ton/ha, respectively, were randomly assigned to the main plot. Two sorghum lines, BR‐008 (resistant) and BR‐009 (susceptible), were assigned to the split plots. The split‐split plots corresponded to with or without the fungicide Opera® (epoxiconazole + pyraclostrobin). The residual effect of CS and L from the 2008/2009 growing season was evaluated in the 2009/2010 growing season. For the 2008/2009 growing season, the area under anthracnose progress curve (AUAPC) was reduced by 39 and 42% for lines BR‐008 and BR‐009, respectively, with the application of CS. In the presence of the fungicide, the AUAPC was reduced by 35 and 42% for the CS and L treatments, respectively. Calcium silicate with and without fungicide contributed to decreasing the AUAPC by 44 and 37%, respectively. The fungicide spray decreased the AUAPC by 50 and 39% for lines BR‐008 and BR‐009, respectively. Without fungicide, the AUAPC decreased by 88% for line BR‐008 compared with line BR‐009; however, with fungicide, the reduction reached 90%. The Si leaf tissue concentration significantly increased with the CS application (5.9 g/kg) compared with the L application (0.3 g/kg), regardless of the sorghum line. The yield increased by 0.6 ton/ha with the CS compared to the L application. The fungicide increased yield by 0.48 ton/ha compared with the non‐fungicide spray treatment. The residual effect of CS in the soil increased Si leaf tissue concentration and yield as well as reduced the intensity of anthracnose in the 2009/2010 growing season.     

Potassium phosphites in the protection of common bean plants against anthracnose and biochemical defence responses

The aim of this study was to investigate the effectiveness of potassium phosphites for the control of anthracnose and the mode of action of these products on common bean plants against Colletotrichum lindemuthianum, comparing it with the standard resistance inducer acibenzolar‐S‐methyl. The protection of plants against anthracnose was evaluated in greenhouse after treatment with potassium phosphites (Phosphite A and B, 5.0 ml/L), acibenzolar‐S‐methyl (0.25 g/L), or no treatment (control). Two sprayings of the treatments were performed, respectively, at V4 stage (three trifoliate leaves) and at the R5 stage (flower buds present). The inoculation with C. lindemuthianum was performed 5 days after the first spraying. Phosphite formulations A and B reduced the severity of anthracnose by 68.7% and 55.6%, respectively, and the presence of phosphites in the leaf tissues were detected at concentrations between 1 and 3 mm by 7 days after spraying. These same concentrations of phosphites reduced the mycelial growth of C. lindemuthianum in vitro by 15.0% to 25.7%. In addition, the activities of defence enzymes and the levels of phenolic compounds and lignin were assessed. Phosphite treatments enhanced the activity of various enzymes, including superoxide dismutase, peroxidase, chitinase, and β‐1,3‐glucanase, and increased the lignin and a small increase in the levels of soluble phenolics. This study provides evidence that phosphite treatments control anthracnose by acting directly on C. lindemuthianum and by inducing the production of defence responses.     

Red Light Increases Suppression of Downy Mildew in Basil by Chemical and Organic Products

Basil is an economically important herb in the United States and in the world. Recent epidemics of basil downy mildew, caused by Peronospora belbahrii, have significantly affected basil production in the United States. ProPhyt (potassium phosphite), Actigard (acibenzolar‐S‐methyl) and Organocide (sesame oil) were evaluated in the greenhouse in the presence or absence of red light for their effects on the severity of downy mildew and sporangial production by P. belbahrii. Red light at intensity of 12 μmol photons/m²/s significantly (P < 0.05) reduced severity of downy mildew in basil. ProPhyt‐treated basil plants had the lowest disease severity irrespective of red light exposure. Basil plants treated with Actigard and Organocide under red light had significantly lower disease severity compared to plants under dark conditions with the same fungicide treatments 14 and 13 days after inoculation (DAI) in experiments 1 and 2, respectively. Red light significantly reduced AUDPC in the treatments of Actigard and Organocide in both experiments. Basil plants treated with Actigard and Organocide under red light had significantly reduced number of P. belbahrii sporangia than those under dark conditions receiving the same fungicide treatments. This is the first report demonstrating red light in combination with Actigard and Organocide for improved management of downy mildew in greenhouse‐grown basil.     

The effect of phosphite on the sexual reproduction of some annual species of the jarrah (Eucalyptus marginata) forest of southwest Western Australia

Phosphite is a cost-effective fungicide used to control the pathogen Phytophthora cinnamomi which is damaging the diverse flora of the southwest of Western Australia. Three annual species of the southwest jarrah (Eucalyptus marginata) forest of Western Australia (Pterocheata paniculata, Podotheca gnaphalioides and Hyalosperma cotula), were studied to determine the effect of the fungicide phosphite on the species’ reproduction. Phosphite at concentrations of 2.5, 5 and 10 g L^–1 reduced pollen fertility of Pt. paniculata when plants were sprayed at the vegetative stage. Pollen fertility of all three species was reduced when plants were sprayed at anthesis with 10 g L^–1 phosphite. Seed germination was reduced by phosphite in Pt. paniculata and H. cotula when plants were sprayed in the vegetative stage. Phosphite when sprayed at anthesis at a concentration of 5 g L^–1 reduced seed germination of H. cotula. Phosphite at concentrations of 5 and 10 g L^–1 killed a proportion of plants from all three species and up to 90% of Po. gnaphalioides plants. The frequent application of phosphite, therefore, may reduce the abundance of annual plants in this ecosystem. Received: 14 December 2000 / Revision accepted: 10 March 2001     

Immunoassay‐based Techniques for Early and Specific Detection of Latent Postharvest Anthracnose in Mango

The postharvest anthracnose pathogen Colletotrichum gloeosporioides inciting latent or quiescent infection of mango was detected in early stages using immunoassay methods. Twenty‐five pathotypes isolated from different agroclimatic zones of Tamil Nadu, Karnataka and Pondicherry, India, revealed the variation in protein profile analysis (SDS‐PAGE). The polyclonal antibodies (PCA) were raised against the unfractioned mycelial protein (UMP) and a 40‐kDa polypeptide present in all pathotypes. Standardization of antigen and antiserum dilutions revealed that an antigen dilution of 1 : 200 (protein concentration of 20 μg/ml) and antiserum dilution of 1 : 100 (protein concentration of 40 μg/ml raised against UMP) and 1 : 200 (protein concentration of 20 μg/ml raised against 40 kDa polypeptide) was found to be optimum for the detection of anthracnose pathogen. Both antisera detected the C. gloeosporioides antigen in enzyme‐linked immunosorbent assays (ELISAs), dot immunobinding assays (DIBAs) and Western blots. The specificity in reaction was compared by isolating other Colletotrichum spp. from various hosts viz., C. lindemuthianum (beans), C. falcatum (sugarcane), C. musae (banana), C. capsici (chillies) and Botryodiplodia theobromae (mango). The antisera generated against UMP revealed the cross‐reaction with other host isolates and mango stem end rot pathogen (B. theobromae). The PCA raised against 40‐kDa polypeptide exhibited the specific reaction with C. gloeosporioides isolates in all the immunoassay techniques. By utilizing both PCA, the presence of latent infection was observed in healthy‐looking leaves, flowers and fruits in orchard conditions. The fruit tissues recorded high absorbance values followed by flowers and leaves in all the detection methods. The ELISA technique was also useful in assessing the pathogen inoculum at various biocontrol formulations sprayed mango trees under field conditions. The fluorescent pseudomonad strains mixture (KFP1 + FP7) amended with chitin sprayed at 30‐day intervals revealed the significant reduction in pathogen load than other formulations and unsprayed control.     

Water-soluble granules containing <Emphasis Type="Italic">Bacillus megaterium</Emphasis> for biological control of rice sheath blight: formulation,bacterial viability and efficacy testing

Endospores of B. megaterium were formulated in granule formulations with sodium alginate, lactose and polyvinylpyrrolidone (PVP K-30) by the wet granulation technique. The granule formulation exhibited good physical characteristics, such as high-water solubility and optimal viscosity, that would be suitable for spray application. The bacteria remained viable in the dry granule formulation at 10⁹ c.f.u./g after 24 months storage at room temperature. Under laboratory conditions, aqueous solutions of the formulation showed high activity against mycelial growth of R. solani (99.64 ± 0.14% mycelial inhibition). High viability of the bacterial antagonist on leaf sheath and leaf blade at day 7 after spraying with the formulation was observed (approximately 10⁶ c.f.u./g of plant). Application of an equivalent number of un-formulated endospores resulted in much loss of the bacterial endospores even 1 day after application. In a small pilot field study, an aqueous solution of the formulation (3%w/v) applied by spraying at days 1, 5 and 10 after pathogen inoculation of the rice plants was more effective in suppressing rice sheath blight disease than one application of a fungicide (Iprodione) at day 1. Additionally, rice plants sprayed with the aqueous solution of the granule formulation had higher panicle and whole kernel weights than those of fungicide-treated and control (untreated) plants.     

A Strobilurin Fungicide Relieves Bipolaris oryzae‐Induced Oxidative Stress in Rice

Although strobilurins are one of the most effective and broad spectrum classes of systemic fungicides, they may also increase plant stress tolerance by modulating the activity of antioxidant enzymes. To address this issue, the effect of azoxystrobin (Az) on the activity of antioxidant enzymes and on the concentrations of antioxidant metabolites and oxidative stress‐related compounds was studied in rice plants (cv. Metica‐1) either inoculated or not with Bipolaris oryzae, the causal agent of brown spot (BS). The Az minimally affected the enzyme activities, but consistently increased the glutathione reduced (GSH) concentrations in the noninoculated plants. The activities of superoxide dismutase, peroxidase, ascorbate peroxidase, glutathione peroxidase, glutathione reductase and glutathione‐S‐transferase were increased upon B. oryzae infection, but such increases were greatly limited in the Az‐sprayed plants. Catalase activity decreased in the inoculated plants compared to the noninoculated plants regardless of fungicide treatment. The GSH concentration increased in response to the B. oryzae infection, and the Az‐sprayed plants sustained higher levels of GSH at advanced stages of fungal infection than did the nonsprayed plants. The inoculated plants exhibited an extensive oxidative stress as evidenced by higher concentrations of hydrogen peroxide and malondialdehyde compared to the noninoculated plants, but lower and later increases were recorded in the Az‐sprayed plants than in the nonsprayed plants. Therefore, Az greatly reduces B. oryzae‐induced oxidative stress by limiting BS development rather than by activating antioxidant enzymes. The GSH, however, seems to be Az‐modulated, and this may partially explain the constrained oxidative stress observed in the Az‐sprayed plants.     

Differential metabolic response of narrow leafed lupine (Lupinus angustifolius) leaves to infection with Colletotrichum lupini

Flavones and isoflavones are a major group of phenolic secondary metabolites which occur in leaves of narrow leafed lupine (Lupinus angustifolius) either as free aglycones or in a form of glycosides and malonyl-glycosides. Profiles of phenolic compounds in leaves of seedlings infected with anthracnose causing fungus Colletotrichum lupini were compared to those of healthy plants. A HPLC with diode array UV detector was used as the analytical method and identification of these secondary metabolites was confirmed with a HPLC/MSⁿ instrument. Isomers of several target compounds differing in the glycosilation and/or malonylation pattern were detected in the studied samples. However, the application of standard HPLC with C18 columns resulted in the co-elution of several glyconjugates in single chromatographic peaks whereas for isoflavonoid aglycones complete resolution was achieved. Lupine plants grown in a greenhouse were either sprayed with the C. lupini spore suspension or the suspension was spotted on to wounded leaves. Profiles of the isoflavones were altered in result to infection with both methods. In particular, the concentration of isoflavone free aglycones detected in extracts from diseased plants was substantially increased in all of the studied samples. However, the pattern of these compounds depended on the age of lupine leaves as well as on the method of infection. Synthesis of luteone and 2′-hydroxygenistein was enhanced in the youngest leaves of plants sprayed with spores as well as in wound-infected leaves. Wighteone synthesis was induced mainly in older leaves of plants sprayed with the spore suspension.     

Efficacy of Acibenzolar‐S‐Methyl and β‐Aminobutyric Acid for Control of Downy Mildew in Greenhouse Grown Basil and Peroxidase Activity in Response to Treatment with these Compounds

Downy mildew, caused by the oomycete pathogen Peronospora belbahrii, is a devastating foliar disease of basil in the United States and worldwide. Currently there are very few chemistries or organic choices registered to control this disease. In this study, two systemic acquired resistance (SAR) inducers, acibenzolar‐S‐methyl (ASM) and β‐aminobutyric acid (BABA), were evaluated for their in vitro effects on the pathogen, for their potential to control basil downy mildew in greenhouses, and for changes in peroxidase activity in basil plants treated with these two SAR inducers. No significant inhibition of sporangial germination was detected in water agar amended with ASM at concentrations lower than 100 mg/l or with BABA at concentrations lower than 500 mg/l. Efficacy of ASM and BABA in greenhouses varied depending on the rate, method and timing of application. The area under the disease progress curve (AUDPC) of disease severity was significantly reduced compared to the non‐treated control when ASM was sprayed (in all experiments) or drenched (in one out of two experiments) pre‐, or pre‐ + post‐inoculation at rates of 25–400 mg/l. Three weekly post‐inoculation sprays of ASM at the rate of 50 mg/l reduced AUDPC by 93.0 and 47.2% when started 3 and 7 days after inoculation (DAI), respectively. The AUDPC of disease severity was also significantly reduced when BABA was sprayed pre‐ + post‐inoculation at rates of 125–500 mg/l. According to the prediction using a log‐logistic function, 50% maximum disease protection was achieved at a concentration of 27.5 mg/l of ASM. Basil plants treated with these two SAR inducers and challenged with the pathogen showed significantly higher peroxidase activity than the non‐treated control at 8 DAI. Temporally, the highest activity of peroxidase was detected at 8 DAI, decreased at 15 DAI and waned further at 23 DAI.     

Benzyladenine Promotes Flowering in <Emphasis Type="Italic">Doritaenopsis</Emphasis> and <Emphasis Type="Italic">Phalaenopsis</Emphasis> Orchids

Two experiments were performed to determine how application of the cytokinin benzyladenine (BA) influenced flowering in Doritaenopsis and Phalaenopsis orchid clones. In the first experiment, two vegetative orchid clones growing in 15-cm pots were transferred from a 28°C greenhouse that inhibited flowering to a 23°C greenhouse for flower induction (day 0). A foliar spray (0.2 L m⁻²) containing BA at 100, 200, or 400 mg L⁻¹ or 25, 50, or 100 mg L⁻¹ each of BA and gibberellins A₄ + A₇ (BA+GA) was applied on days 0, 7, and 14. Plants treated with BA alone at 200 or 400 mg L⁻¹ had a visible inflorescence 3–9 days earlier and had a mean of 0.7–3.5 more inflorescences and 3–8 more flowers per plant than nontreated plants. The application of BA+GA had no effect on inflorescence number and total flower number at the rates tested. In the second experiment, three orchid clones received a single foliar spray of BA at 200 mg L⁻¹ at six time points relative to time of transfer from 29°C to 23°C (−1, 0, +1, +2, +4, or +6 weeks). A separate group of plants received a BA application at week 0 but was maintained at 29°C. Inflorescence number was greatest in all three orchid clones when plants were treated with BA 1 week after the temperature transfer. Plants that were sprayed with BA and maintained at 29°C did not initiate inflorescences. The promotion of flowering by the application of BA suggests that cytokinins at least partially regulate inflorescence initiation of Doritaenopsis and Phalaenopsis, but its promotion is conditional and BA application cannot completely substitute for an inductive low temperature.     

Development of sequence-specific PCR markers associated with a polygenic controlled trait for marker-assisted selection using a modified selective genotyping strategy: a case study on anthracnose disease resistance in white lupin (<Emphasis Type="Italic">Lupinus albus</Emphasis> L.)

Selection for anthracnose disease resistance is one of the top priorities in white lupin (Lupinus albus) breeding programs. A cross was made between a landrace P27174 (resistant to anthracnose) and a cultivar Kiev Mutant (susceptible). The progeny was advanced to F₈ recombinant inbred lines (RILs). Disease tests on the RIL population from field trials over 2 years indicated that the disease resistance in P27174 was polygenic controlled. A modified selective genotyping strategy was applied in the development of molecular markers linked to quantitative loci conferring anthracnose diseases resistance. Eight individual plants representing high level of anthracnose resistance (HR), eight plants representing susceptibility (S), together with eight lines representing medium level of anthracnose resistance (MR), were subjected to DNA fingerprinting by Microsatellite-anchored Fragment Length Polymorphisms (MFLP). Six MFLP polymorphisms, which had the banding pattern matching the HR plants and the S plants, were identified as candidate markers linked to quantitative loci conferring anthracnose resistance. The six candidate MFLP markers were delineated into three groups based on their banding variation on the eight MR plants. One candidate MFLP marker each from the three groups was selected, cloned, sequenced, and converted into co-dominant, sequence-specific PCR markers. These three markers, designated as WANR1, WANR2 and WANR3, were tested on a segregating population containing 189 F₈ RILs. The disease phenotyping data and the marker genotyping data on the F₈ RILs were merged and analysed by the JMP software using the ‘fit-model’ function, which revealed that 71% of the phenotypic variation was controlled by genetic factors, while the other 29% of the phenotypic variation was due to environmental factors and environment × genotype interactions. On individual marker basis, marker WANR1 conditioned 39% of phenotypic variations of anthracnose resistance, followed by marker WANR2 with 8%, and WANR3 with 12%. Further analysis showed that WANR2 and WANR3 were on the same linkage group with a genetic distance of 15.3 cM. The combination of the two markers WANR1 and WANR3 explained 51% out from the 71% of the genetic controlled variations for disease resistance, indicating that the two QTLs working additively for anthracnose disease resistance. A simulation of marker-assisted selection on the F₈ RIL population using the two markers WANR1 and WANR3 identified 42 out of the 189 RILs being homozygous for resistance-allele bands for both markers, and 41 of them showed disease severity below 3.0 on the 1 (highly resistant) to 5 (susceptible) scale. The two markers WANR1 and WANR3 have now been implemented for marker-assisted selection for anthracnose resistance in the L. albus breeding program in Australia.     

The effect of carbendazim-generating fungicides with and without a mineral oil additive on tomato stem lesions caused by carbendazim-sensitive and tolerant strains of Botrytis cinerea

Isolates of Botrytis cinerea were obtained from tomatoes in several localities in the West Scotland. Some isolates grew on agar containing 100 mg/1 benomyl (carbendazim-tolerant), while others did not (carbendazim-sensitive). Pot-grown tomato plants treated with benomyl and other carbendazim-generating fungicides, applied either as sprays or soil drenches, were inoculated on the leaf scars with some of these isolates. On treated plants the carbendazim-tolerant isolates formed lesions which were about as large as those on untreated plants. Sensitive isolates formed much smaller lesions on treated plants. There was evidence that the increase in lesion size during the period 7–14 days after inoculation with a carbendazim-sensitive isolate was less on plants sprayed with benomyl or carbendazim with added mineral oil (2% Actipron) than on plants to which the fungicides alone had been applied. No such effect was recorded with thio-phanate-methyl. There was also an indication that the addition of Actipron to a benomyl spray improved the effect of the fungicide against two tolerant isolates, though there was no effect on the relative increase in lesion size during the second week after inoculation. In two tests the addition of 2% and 4% Actipron to benomyl soil drenches did not improve the level of leaf scar lesion control.     

Biochemical aspects of bean resistance to anthracnose mediated by silicon

This study investigated the effect of silicon (Si) on resistance of bean plants (cv. ‘Peróla’) to anthracnose, caused by Colletotrichum lindemuthianum, grown in a nutrient solution containing 0 (?Si) or 2 mmol Si L^?1 (+Si). The concentration of Si in leaf tissue and the incubation period increased by 55.2% and 14.3%, respectively, in +Si plants in relation to ?Si plants. The area under anthracnose progress curve and the severity estimated by the software QUANT significantly decreased by 32.9% and 27%, respectively, for +Si plants. Si did not affect the concentration of total soluble phenolics. Chitinases activity was higher in the advanced stages of infection by C. lindemuthianum for leaves of ?Si plants. β‐1,3‐Glucanase activity increased after C. lindemuthianum infection, but it was not enhanced by Si. Peroxidase and polyphenoloxidase activities had no apparent effect on the resistance of bean plants to anthracnose, regardless of the presence of Si. The increase in lignin concentration as well as on the phenylalanine ammonia‐lyase and lipoxygenase activities were important for the resistance of +Si plants against anthracnose. The results of this study suggest that Si may increase resistance to anthracnose in bean plants by enhancing certain biochemical mechanisms of defence as opposed to just acting as a physical barrier to penetration by C. lindemuthianum.     

Suppression of Rust and Brown Eye Spot Diseases on Coffee by Phosphites and By‐products of Coffee and Citrus Industries

The rust and brown eye spot, caused by Hemileia vastatrix and Cercospora coffeicola, respectively, are the most important fungal diseases on coffee in South America. Their management is mainly by chemical treatment, and there is no genetic resistance to brown eye spot known so far. Considering the need for developing alternative products for their control, the goal of this work was to evaluate the effects of phosphites and by‐products of coffee and citrus industries on rust and brown eye spot. Formulations of coffee and citrus industry by‐products, phosphites and their combination with fungicide were evaluated in field experiments, and their effect on fungal urediniospores and conidia was evaluated in vitro. In the field, treatments were applied individually or in combination and the in vitro assays were performed with manganese phosphite (Reforce Mn), potassium phosphite and citrus industry by‐product (Fortaleza), copper phosphite and coffee industry by‐product (Fitoforce Full), and fungicide. The severity and incidence of rust and brown eye spot on coffee leaves, yield, and leaf retention were evaluated in the field. Percentage of spore germination was evaluated in vitro for both fungi, whereas mycelial growth was evaluated for C. coffeicola only. The treatments Fortaleza, Reforce Mn and Fitoforce Full suppressed both diseases with a reduction in defoliation. In the year 2012, the plants treated with Reforce Mn and Reforce Mn + Fortaleza showed a yield increase of 72 and 88%, respectively, which was similar to the results shown by the fungicide treatment. In vitro inhibition of germination of H. vastatrix urediniospores and of C. coffeicola conidia was observed and suggests that the products exert some toxic effects to both fungi. Finally, the results observed indicate that the combined use of by‐products of plant‐processing industries and phosphites is an alternative and can be added efficiently to the management of coffee diseases.     

The effect of chemical and biological treatment on root and crown rot disease caused by Phytophthora cryptogea Pethybr. & Lafferty in Gerbera

Phytophthora root and crown rot (Phytophthora cryptogea) on gerbera is difficult to manage because most gerbera cultivars are susceptible to P. cryptogea. This study was conducted in order to determine the in vivo (pot experiment) efficacy of some fungicides and biofungicides. In pot experiments, fungicides were applied 7 days after inoculation with P. cryptogea, while biofungicide was applied 7 days before inoculation. In this study, soil drenches of five fungicides were tested. “Ametoctradin+dimethomorph (100 ml/day),” “mandipropamid+difenoconazole (60 ml/day),” “propamocarb+fosetyl‐Al (200 ml/day),” “mancozeb+metalaxyl‐M (250 g/day)” and “azoxystrobin+difenoconazole (100 ml/day)” active substances were used. Similarly, one biofungicide Bacillus amyloliquefaciens syn. MBI 600 (50 g/100 L) was applied by soil drenching. Efficacy of treatments was assessed according to the percentage of the root system which was visibly rotten at the end of the experiment. Root and crown rot severity was rated on a scale of 0 = 0% root system necrotic, 1 = 1%‐25% necrotic, 2 = 26%‐50% necrotic, 3 = 51%‐75% necrotic and 4 = 76%‐100% necrotic from 12 to 21 days. In this experiment, “azoxystrobin 200 g/L + difenoconazole 125 g/L” exhibited the highest efficacy against P. cryptogea with a ratio of 43.75%. The other fungicides and biofungicides ametoctradin 300 g/L + dimethomorph 225 g/L, mandipropamid 250 g/L + difenoconazole 250 g/L, propamocarb 530 g/L + fosety‐Al 310 g/L, mancozeb 64%+metalaxyl‐M 4% and Bacillus amyloliquefaciens syn. MBI 600 11% were ineffective. Importance should be given to management strategies of P. cryptogea of and more experiments should be carried out for a better understanding of the use of registered fungicides and biofungicides.     

Efficacy of some biorational insecticides against Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) under laboratory and greenhouse conditions in Kuwait

The tomato leafminer, Tuta absoluta, is one of the most destructive pests of tomato worldwide. Management of the pest is mainly based on chemical insecticides. Reliance on insecticides is difficult to sustain because of unintended long‐term adverse effects on the environment and human health. Consequently, there is a need to develop pest management strategies that ensure the production of high‐quality products, while at the same time ensuring environmental sustainability and maximum consumer protection. We evaluated the efficacy the biopesticides: Azadirachtin, Bacillus thuringiensis, Steinernema feltiae and Beauveria bassiana individually and in combination against T. absoluta under laboratory and greenhouse conditions. When second instar larvae were exposed to tomato leaf discs treated with Azadirachtin (3 g / L), B. thuringiensis (0.5 g/L) or B. bassiana (1.5 g/L), 70%–86%, 55%–65%, and 45.5%–58.5% mortality was observed, respectively. Steinernema feltiae (1,000 IJs/ml) was the least effective biopesticide, with 26%–42% mortality. In the greenhouse trials on tomato, pest infestation (mines/10 leaves/plant) and fruits damaged were significantly lower on plants treated with Azadirachtin  +  B. thuringiensis or Azadirachtin  +  B. bassiana compared to plants treated with Azadirachtin, B. thuringiensi, B. bassiana or S. feltiae alone. Azadirachtin  +  B. thuringiensis and Azadirachtin  +  B. bassiana resulted in 90% and 81% reduction in fruits damaged in the summer experiments, respectively, and 96% and 91% in winter. The most severe pest infestation was observed on plants treated with S. feltia. The results indicate that the biopesticides, except S. feltia, can contribute to T. absoluta control in greenhouse tomato crops. In particular, the combined use of Azadirachtin with B. thuringiensis or B. bassiana provided the highest level of control of the pest. The potential for including these biopesticides in an overall sustainable integrated pest management programme for T. absoluta is discussed.