Purple Blotch Disease Of Onion Research Articles

Sustainable biocontrol of purple blotch disease in Allium cepa L. by biocontrol yeasts, Pichia kluyveri and Filobasidium wieringae

BackgroundPurple blotch disease is a devastating disease, resulting in significant yield losses in onion. Application of synthetic fungicides is a rapid approach for the control of this disease, but extensive use of synthetic fungicides results in resistance development in pathogen. Thus, it is mandatory to explore alternative approaches to overcome the fungicide resistance challenges. The present study focused on a sustainable biocontrolling approach by using biocontrol yeast. The objective was to develop a management strategy that offers an environmentally acceptable alternative to commonly used fungicides.ResultsA total of six pathogenic isolates were obtained from the infected onion leaves, out of all tested isolates, OP-4 recorded as highly virulent with disease incidence (75.2%). Filobasidium wieringae and Pichia kluyveri drastically reduced the in vitro mycelial growth of Alternaria porri (14 and 21 mm, respectively). In the greenhouse experiment, plant inoculated with P. kluyveri suspension was the most effective, resulting in considerable reduction (77.1%) in disease severity, before two days of pathogen inoculation. However, F. wieringae showed a considerable reduction (84.5%) in disease severity when applied in combination with P. kluyveri two days post-inoculation.ConclusionsThese findings highlighted the strong biocontrol potential of P. kluyveri and F. wieringae in managing the purple blotch disease of onion and can reduce the reliance on synthetic fungicides. Further research and field trials should be conducted to optimize the application methods and evaluate the long-term effectiveness of these bioagents.

Antagonistic potential of Trichoderma hamatum against Alternaria porri causing purple blotch disease of onion through Gas chromatography-mass spectrometry (GCMS) analysis

Alternaria porri causing purple blotch disease of onion is a destructive phytopathogen which causes severe loss in productivity. The present study aimed to unravel the antagonistic potential and efficacy of volatile organic compounds produced by various Trichoderma spp. against A. porri causing purple blotch disease of onion through Gas chromatography-mass spectrometry (GCMS) analysis. Ten isolates of Trichoderma species were isolated from the rhizospheric soil of healthy onion plants. Upon paired plate technique, the in vitro efficacy of ten Trichoderma isolates were tested against virulent isolate of Alternaria porri isolated from purple blotch disease infected onion plants. The Trichoderma isolate TIM2 showed 76.29 per cent inhibition on mycelial growth of pathogen. The effective Trichoderma isolate was identified as Trichoderma hamatum through the analysis of the rDNA of internal transcribed spacers (ITS) region and it was subjected to GC-MS analysis. The result of GCMS analysis indicated the highest peak area and retention time with major antimicrobial bioactive compounds like Tetradecane, 2,6,10-trimethy (20.327), (1.22) and Dodecane, 2-cyclohexyl (20.079), (2.14), Heptadecane (21.222), (9.50), Octadecane (22.379), (3.58), Eicosane, 9-cyclohexyl (22.578), (1.84), 2-Propenoic acid, pentadecyl ester (23.400), (10.37), 2,6,10,14-tetramethyl (23.567), (10.37), Eicosane (27.311), (2.34), Hexadecanoic acid, methyl ester (27.918), (4.43), n-Hexadecanoic acid (29.156), (3.59) and Tetrapentacontane, 1,54-dibromo (31.906), (3.33). These bioactive compounds identified through GCMS analysis from the crude extracts of Trichoderma hamatum exhibited a stronger antifungal activity against A. porri. Hence the application of T. hamatum for the management of purple blotch disease highly supress growth of the pathogen and reduce the disease incidence.

Molecular Characterization of Alternaria porri (Ellis) Cif., The Causal Agent of Purple Blotch Disease of Onion, With the Help of Simple Sequence Repeat Markers

Purple blotch disease of onion, caused by Alternaria porri (Ellis) Cif., causes extensive damage to the bulb and seed crops. The present study was aimed to assess the morpho-cultural variations and genetic diversity in 14 isolates of A. porri by simple sequence repeat (SSR) markers (selected on the basis of polymorphism pattern). Most isolates showed white fluffy colony growth and yellow to light orange pigmentation with circular, irregular and smooth margin along with clear-cut zonation. During the study period, 36 loci were obtained and the average expected gene diversity was found in the range of 0.0531-0.3707. Shan cluster analysis and unweighted pair-group method with arithmetic averages (UPGMA) analysis revealed that the isolates ‘A.p.B4’ and ‘A.p.B1' had maximum similarity coefficient (0.9166667), while isolates ‘A.p.B12’ and ‘A.p.B13’ had distant similarity coefficient (0.6111111). The SSR primers D.N.alt4 (200-720 bp) and D.N.alt10 (300-600 bp) represented unique bands for all isolates which were used for the identification of isolates. The polymorphic information content (PIC) value for primer D.N.alt-4 and D.N.alt-10 was 0.0, with maximum and minimum PIC value for D.N.alt14 (0.2978) and D.N.alt-5 (0.0495), respectively, thus represented the discriminatory power of a locus. The study revealed that the nine SSR markers tested were helpful in the isolation and molecular characterization of A. porri on the basis of polymorphism or genetic diversity.

Evaluation of different fungicides in the control of purple blotch [Alternaria porri (Ellis) Cif] of onion

A field experiment was carried out to evaluate the effect of different fungicides on purple blotch [Alternaria porri (Ellis) Cif] of onion (Allium cepa L.) experimental farm during Rabi 2015-16 and 2016-17 in the Department of Plant Pathology, College of Agriculture, Swami Keshwanand Rajasthan Agricultural University, Bikaner. The experiment was laid-out in randomized block design with three replications during Rabi 2015-16 and 2016-17. The effective management of purple blotch of onion through application of different fungicides was appraised under field conditions. Among the nine treatments evaluated, the seed treatment with Tebuconazole @ 1g/kg + two spray Tebuconazole @ 0.1% was found significantly minimum per cent disease index of 17.75% and bulb yield 26.83 t/ha which was superior over other treatments and control. However, the result shows that the application of Tebuconazole was found superior and maximum inhibited the mycelial growth of Alternaria porri at 100 and 200 ppm concentrations and Azadirachta indica (Neem leaf extract) was found least effective at all concentrations against Alternaria porri. Moreover, the seed treatment with Difenoconazole @ 1g/kg + two spray of Difenoconazole @ 0.1% was recorded second best (PDI 29.03% and bulb yield 22.60 t/ha) but it was found statistically significant with the application of seed treatment with Tebuconazole + Trifloxystrobin @ 0.5g/kg + two spray Tebuconazole + Trifloxystrobin @ 0.05% (PDI 32.87% and Bulb yield 22.33 t/ha) followed by seed treatment with Propiconazole @ 1g/kg + two spray of Propiconazole @ 0.1% (PDI 33.83% and bulb yield 21.97 t/ha) in pooled analysis, respectively. The maximum PDI (74.00%) and minimum bulb yield (5.03 t/ha) was observed in control. Field observations of the different fungicides are very useful to effective control of purple blotch disease of onion as well as in-vitro technique for efficiently inhibit the mycelial growth of the test fungi.

Management of purple blotch of onion caused by Alternaria porri by using some novel fungicides under field condition in western Odisha

A field experiment was conducted at Regional Research and Technology Transfer Station, OUAT, Chiplima, Sambalpur, Odisha, India for the management of purple blotch of onion. From the experiment it was found that all the treatments were effective to reduce the severity of the disease as compared to untreated control. Among the treatments, seed treated with Carboxin 37.5%+Thiram 37.5%@ 2g/kg and three foliar sprays of Trifloxystrobin + Tebuconazole @0.4g/l of water at 10 days interval starting from initiation of the disease was most effective in reducing the purple blotch disease of onion (69.5% disease control) and was closely followed by seed treated with Carboxin 37.5%+Thiram 37.5% @ 2 g/kg and three foliar sprays of Tebuconazole @ 1.0ml/l of water (62.3% disease control). A maximum increase of yield (83.4%) with highest cost benefit ratio (1.97) was also achieved with the same treatment.

In vitro Evaluation of Fungicides and Plant Extracts to Control Purple Blotch Disease of Onion in Pakistan

In vitro Evaluation of Fungicides and Plant Extracts to Control Purple Blotch Disease of Onion in Pakistan

Evaluation of different newer chemical pesticides through on farm testing (OFTs) against major pests and diseases of vegetable crops

The On farm testing (OFTs) for evaluation of different chemical pesticides were carried out in five locations against shoot and fruit borer in brinjal, fruit borer in tomato, purple blotch disease in onion, shoot and fruit borer in okra and whitefly in capsicum during 2016-17 and 2017-18. The result of on farm testing indicated that Indoxacarb @ 0.5ml per litre water against shoot and fruit borer of brinjal, Lambda chalothrin @ 0.5ml per litre water for tomato fruit borer, Difenconazole @ 0.5 ml per litre water for management of purple blotch disease of onion, Lambda chalothrin @ 0.5ml per litre water against shoot and fruit borer of okra and Thiamethoxam + Lambda chalothrin @ 0.4 ml per litre water for whitefly in capsicum have been found most effective during both the years of investigation. The production, net return and BC ratio have also been found effective as compared to rest of the treatments. The insecticides and fungicides used in farmers practices showed poor performance during both the years of on farm testing, which may be due to very old in use and many of them lost their efficacy, as compared to the insecticides and fungicides that showed excellent performance in present on farm testing. In the changing pest and disease scenario, such effective insecticides and fungicides need to be used judiciously to reduce the number of application of chemical pesticides and for effective management of various pests and diseases.

<i>In-Vivo</i> Management of Purple Blotch of Onion Caused by <i>Alternaria porri</i> (Ellis) Cif. through Fungicides

An experiment was carried out to study the outcome of environmental factors (Temperature, Relative Humidity, Rainfall) and management of the purple blotch disease of onion using five treatments (Rovral + Ridoil gold with 3,4,5,6 sprays and control). The Taherpuri variety was used during the 2015-2016 cropping seasons at BARI, Gazipur, Bangladesh. In the experiment, the purple blotch disease surfaced at the end of January 2016 and was severe in late February to March (PDI 76.12%) due to temperature and RH above 24°C and 95%, respectively. As for the chemical control, the PDI for the treatments ranged from 50.66% to 83.33%. Significantly higher stem height was recorded by T4 (68.06 cm), where six sprays of Rovral + Ridomil were applied. The minimum stem height was recorded in T5 (59.23 cm). The maximum stem number per hill was recorded in T4 (2.30) numerically but differed significantly with T5 (2.00), where fungicides were not applied. The maximum lesion area was measured in T5 (25.26 mm2). Regarding PDI (Percent disease index), there was a significant difference among the treatments. The PDI value on purple blotch of onion ranged from 34.00 to 83.33. The lowest PDI was assessed in T4 (34.00). Statistical analysis revealed that a significant decrease of PDI on purple blotch was recorded under treatments of T1, T2, T3, and T4 (39.20%, 45.60%, 49.59%, and 59.19%) on controlling the disease and giving the optimum yield but all of them significantly differed with T5 (83.33%) where no fungicides were sprayed.

Synergistic effect of plant extracts and fungicide against purple blotch disease of onion

Onion is widely cultivated crop and attacked by different fungi. Purple blotch of onion caused by Alternaria porri is a continuous threat to Pakistan agriculture industry for the last few years. Generally, fungicides give satisfactory control but due to the environmental concerns, their use should be restricted. In integrated disease management program, cost effective and eco-friendly approach is used to cope with plant pathogens. Therefore, the present study was planned to evaluate the antifungal efficacy of different plants extracts such as Pongamia pinnata, Polyalthia longifolia, Cassia fistula, and Citrus sinensis against A. porri alone as well as synergistically with different concentrations of Mancozeb under in vitro conditions. Methanolic leaves extracts of these plants were mixed with different concentrations (25, 50, and 75%) of fungicide and screened via poisoned food technique to measure percent inhibition of fungal growth. The results indicated that plant extracts alone gave appreciable amount of fungal reduction but when used in combination with fungicide, performed best. Among them P. longifolia gave 73%inhibition, C. sinensis 49%, P. pinnata 70%and Cassia fistula showed46% inhibition respectively. In combination with fungicide, 25% of recommended dose, P. longifolia gave 82.93%, P. pinnata gave 77.07 %, C. sinensis 73.17% and C. fistula gave 62.92% inhibition as compared to control against A. porri. With the increase of fungicide in combination, more reduction in the fungal growth was observed. It is concluded that extracts can be used synergistically with fungicides. The combinations will protect the environment by reducing the amount of fungicide

Fungicidal activity of extracellular products of cyanobacteria against Alternaria porri

ABSTRACTAlthough cyanobacteria are recognized as renewable sources of biomass for bioactive compounds, they have received little attention as potential biocontrol agents of foliar plant diseases. The purpose of this study was to evaluate the fungicidal efficacy of cyanobacterial extracellular products against Alternaria porri, which causes onion purple blotch disease, in vitro and under greenhouse conditions. Among the tested cyanobacteria (Anabaena oryzae, Arthrospira sp., Nostoc minutum, N. muscorum and Oscillatoria sp.), extracellular metabolites of N. muscorum and Oscillatoria sp. reduced the linear growth of A. porri by 20.37 and 36.34%, respectively. Culture filtrates of both Oscillatoria sp. and N. muscorum contained high concentrations of phenolic compounds (104.33 and 145.0 mg l−1, respectively), and alkaloids (473.31 and 378.12 mg l−1, respectively). GC-Mass analysis revealed that the most prevalent component in culture filtrates of N. muscorum and Oscillatoria sp. was beta ionone (7.21 and 7.17% of total analytes, respectively). Norharmane and α-iso-methyl ionone constituted 7.08 and 6.83% in N. muscorum and Oscillatoria sp., respectively. Components identified in the two culture filtrates included piperazine derivatives, isocyclocitral, α-trans-seequicyclocitral, phytol, oleic acid, fatty acids esters (methyl palmitate and linoleic acid mythyl ester), myristic alcohol and palmityl chloride. Application of culture filtrates of N. muscorum and Oscillatoria sp. under greenhouse conditions reduced disease severity by 55.1–66.5%. In conclusion, extracellular metabolites of N. muscorum and Oscillatoria sp. have potential as effective fungicides to control purple blotch disease of onion.

Evaluation of entomopathogenic fungus against Alternaria porri (Ellis) causing purple blotch disease of onion

Biological control through the use of antagonistic micro-organisms is a potential and non-chemical means of managing plant diseases. Alternaria porri causes purple blotch disease mostly in onion. In this study, three different entomopathogenic fungi, viz. Beauveria bassiana, Metarhizium anisopliae and Verticillium lecanii, were tested against A. porri. All the three entomopathogenic fungi showed inhibitory effect against A. porri subjected to in vitro studies under dual culture technique, spore (conidial) germination, food poisoning (mycelia germination) and seed germination. The percentage inhibition of mycelial growth (PIMG) of A. porri (69.24, 56.17, and 45.81%) and the percentage inhibition of conidial germination (CG) (97.81, 42.11, and 67.69%) were observed for B. bassiana, V. lecanii and M. anisopliae, respectively. Seed germination index was found to be maximum with M. anisopliae (5557 ± 107.7) and B. bassiana (4390 ± 129.9). B. bassiana exhibited efficient antagonism against A. porri showing the highest PIMG and CG with moderate seed germination index. Microscopic examination showed the disintegrated edge of conidia which had turned black and also stopped the growth of germ tube. Hence, these entomopathogenic fungi were found to be more effective antagonistic organisms and also moderately promote seed vigour index (4390 ± 129.9) as well as plant growth. The present study indicated that the entomopathogenic fungi evaluated have shown significant inhibition of A. porri. Thus, there is a possibility of exploiting them in the management of the disease.

Field evaluation of fungicides againstAlternaria porri(Ellis) Cif., causing purple blotch of onion (Allium cepaL.)

Field evaluation of several fungicides including new molecules was undertaken for the management of purple blotch disease of onion caused by Alternaria porri(Ellis) Cif. The experiments were conducted during kharif of 2012 and 2013 using susceptible variety Arka Nikethan. Cymoxanil 8% + Mancozeb 64% WP @ 2500 ppm and Mancozeb 70% WP @ 2500 ppm were effective in reducing the disease severity by 54.86 and 52.88% over untreated control. However, Mancozeb 70% WP and Cymoxanil 8% + Mancozeb 64% WP recorded the maximum yield of 39.71 and 37.06 t/ha and obtained benefit cost ratio of 33.85 and 20.67. Thus these two fungicides can be recommended for the effective and economical management of the disease.

Cultural practices in relation to purple blotch disease of onion

Transplanting onion on 1 December gave the highest percentage of purple blotch infection. Percentage and severity decreased significantly by decreasing plant density. ‘Behairy’ onion was more resistant than ‘Giza 6’. Nitrogen fertilization at twice the normal level increased the percentage and severity of infection, while a double dose of calcium superphosphate reduced infection. On the other hand, percentage of infection decreased by adding potassium chloride at twice the normal level, while severity of infection increased significantly. Application of fungicides reduced percentage and severity of infection. Bavistin gave the best control.

Purple blotch disease of onion in punjab

Purple blotch disease of onion is a serious trouble in onion-producing countries of the world. In the Punjab State of India, a number of fields have been observed totally destroyed by this disease. Field trials with eleven different fungicides, to check this disease, have indicated that Bordeaux mixture (4:4:50) is the best spray for controlling this disease in the Punjab, and onion variety 53–5 is a potential source for evolving resistant varieties.

Purple blotch disease of onion in Punjab

Purple blotch disease of onion in Punjab