Field Evaluation of a Competitive Lateral-flow Assay for Detection of Alternaria brassicae in Vegetable Brassica Crops

On-site detection of inoculum of polycyclic plant pathogens could potentially contribute to management of disease outbreaks. A 6-min, in-field competitive immunochromatographic lateral flow device (CLFD) assay was developed for detection of Alternaria brassicae (the cause of dark leaf spot in brassica crops) in air sampled above the crop canopy. Visual recording of the test result by eye provides a detection threshold of approximately 50 dark leaf spot conidia. Assessment using a portable reader improved test sensitivity. In combination with a weather-driven infection model, CLFD assays were evaluated as part of an in-field risk assessment to identify periods when brassica crops were at risk from A. brassicae infection. The weather-driven model overpredicted A. brassicae infection. An automated 7-day multivial cyclone air sampler combined with a daily in-field CLFD assay detected A. brassicae conidia air samples from above the crops. Integration of information from an in-field detection system (CLFD) with weather-driven mathematical models predicting pathogen infection have the potential for use within disease management systems

Morphological, cultural, pathogenic and molecular variability amongst Indian mustard isolates of Alternaria brassicae in Uttarakhand

Alternaria blight (Alternaria brassicae) causes severe foliar damage to Indian mustard in Uttarakhand. Ten (10) isolates of A. brassicae were collected from different hosts and characterized for cultural, morphological, pathogenic and molecular variations. A. brassicae colonies varied in their cultural behaviour ranging from cottony, flurry to feathery, with smooth to rough margins. Colour of colonies ranged between white, off white to light brown. Colony growth varied from slow, medium to fast with fast growth in isolate KM and least in JD on the potato dextrose agar (PDA) medium. Significant morphological variations in conidia length, conidia width, and number of horizontal septa were observed in the isolates. Average conidial size ranged from 105 to 135 × 10 to 20 μm. Isolates exhibited variations in disease index, number and size of the lesions. The dendrogram analysis, based on molecular (random amplification of polymorphic DNA, RAPD) basis revealed two groups at 15% similarity coefficient. Group I was composed of seven isolates namely, VR, DV, P7, LM. P10, KR and ND with 18% similarity (82% dissimilarity) while group II was composed of only three isolates namely, JD, KA and AS with only 24% similarity (76% dissimilarity).Keywords: Pathogenic variability, Brassica, Alternaria brassicae, RAPD-PCRAfrican Journal of Biotechnology, Vol. 13(3), pp. 441-448, 15 January, 201

Effect of zeatin on the infection process and expression of MAPK-4 during pathogenesis of Alternaria brassicae in non-host and host Brassica plants

Recent studies have revealed an important role of hormones in plant immunity. Cytokinins are phytohormones that are involved in various regulatory processes including plant defense. Zeatin a cytokinin antagonizes the effect of Alternaria brassicae pathotoxin in cell culture of Brassica juncea. Phytohormones are also the inducers of MAP Kinase signaling pathways which are the important signaling modules in eukaryotic cells. In this paper, an attempt was made to study the exogenous application of zeatin on the disease score, infection behavior of A. brassicae, expression pattern of MAPK-4 in the non host Sinapsis alba, host B. juncea susceptible c.v Varuna, B. juncea moderately tolerant c.v. Divya and transgenic Brassica to confer its role in plant immunity. We observed that high concentration of zeatin led to increased defense responses by delaying the infection process as well as significantly reducing the disease score. Semi-quantitative RT-PCR reveals that zeatin also increases the expression of MAPK-4 at early hours of infection. Our result supports that zeatin up regulates plant immunity via an elevation of MAPK-4 and clearly reflects that it antagonizes the effect of A. brassicae. The crosstalk between zeatin and MAPK signaling pathway may help plants fine-tune defense responses against A. brassicae in the disease Alternaria blight.Keywords: Alternaria blight, Brassica, disease score, MAPK, pathogenesis, infection processAfrican Journal of BiotechnologyVol. 12(17), pp. 2164-217

Morphological, cultural and pathogenic variability in Alternaria brassicae, the causing agent of black spot of rapeseed and mustard

The study on pathogenic diversity of twenty isolates of Alternaria brassicae collected from different locations of Uttarakhand and Central Uttar Pradesh infecting Brassica species (Brassica rapa, Brassica juncea and Eruca sativa) revealed that there was a distinct difference among isolates in terms of mycelial growth, spore length, width, spore beak length and width. The average spore length varied from 21.23?m to 38.13?m with minimum of isolate AUA-19, AUA-43 i.e 21.23?m and maximum of AUA-47 i.e. 38.13?m . The isolates tested on Brassica juncea var.Varuna in green house conditions revealed that all the twenty isolates behaved differently. Among all the isolates, Brassica juncea isolates i.e. AUA-25, AUA-39, AUA-41, AUA-47, AUA-19, AUA-24, AUA-22, AUA-21, AUA-31, AUA-43 and AUA-45 from Uttarakhand, and AUP-29 from Central Uttar Pradesh can be grouped into highly pathogenic with range of Alternaria spot size i.e. 5.03-8.30mm in diameter, while isolate of Eruca sativa i.e. AUA-38 was found least pathogenic with 1.63mm in dia. and eight isolates AUA-18, AUA-20, AUA-23, AUP-28, AUA-32, AUA-33 and AUA-36 were found moderately pathogenic. This study will be useful in developing integrated management strategies of Alternaria leaf spot and breeding programs of oilseed crops (Brassica sp.)

Alternaria blight of oilseed brassicas: A review on management strategies through conventional, non-conventional and biotechnological approaches

Oilseed Brassicas are contributing approximately 28 percent of the India’s total oilseed production. This crop is gaining wide acceptance among t he f a rme r s b e ca u s e of adaptability for both irrigated as well as rainfed areas and suitability for sole as well as mixed cropping. Besides, it offers higher return with low cost of production and low water requirement. The production and productivity of oilseed brassicas are comparatively lower as compared to the world average due to the biotic and abiotic constraints. Among the biotic constraints, alternaria blight disease caused by Alternaria spp. has been reported from all the continents of the world, causing up to 70% yield losses in India. This disease was found on leaves, stems and siliquae and dark spots on the leaves and siliquae reduce the photosynthetic capacity and induce immature ripening, which causes reduced amount of quality seed and oil content. The severity of this disease depends upon weather conditions, varieties, age of host plants and virulence of the pathogens. Efforts are being done throughout the world for the management of alternaria blight of rapeseed-mustard. This paper comprehensively reviews the research of alternaria blight of rapeseed-mustard with special reference to management strategies through conventional, non conventional and biotechnological approaches that leads to planning the future research. The present scenario demands the traditional and modern biotechnological techniques bringing together for integrated disease management according to the need and availability at farmers level for sustainable management of alternaria blight disease of oilseed brassicas

In vitro and in vivo effect of eco-friendly chemicals on alternaria blight disease (Alternaria brassicae) and yield attributes in Indian mustard (Brassica juncea)

The present investigation was done to evaluate the effect of different concentrations of five eco-friendly chemicals in vitro and in vivo, on the management of alternaria blight and yield attributes in Indian mustard (Brassica juncea cv. Varuna). Out of five eco-friendly chemicals, K2SO4 1000 ppm (64.28%) followed by ZnSO4 1000 ppm (63.88%) showed maximum inhibition of mycelial growth in comparison to check. 0.5% concentration of KCl (57.06%) followed by CaSO4 (59.50%) and K2SO4 (62.20%) showed significantly maximum effect on spore germination in comparison to check (74.60%). Spore intensity significantly increased by all the treatments except CaSO4 at 0.5% (40.18%) followed by K2SO4 at 0.5% (29.86%) and ZnSO4 0.75% (5.11% reduction) in comparison to check. The significantly minimum disease index on leaf over check was found by foliar spray of CaSO4 at 0.5%(23.58%) followed by CaSO4 at 1.5% (24.00%) and Na2B4O7.10H2O at 1.5% (24.08%). Na2B4O7.10H2O at 0.75% showed significantly lowest disease index (23.91%) on pod followed by K2SO4 at 1.5% (25.75%) and KCl at 1.5% (26.00%) in comparison to check. CaSO4 at 1.0% showed maximum number of primary branches (7.00), number of secondary branches (13.00) and total yield/ha (1917.30 kg/ha) in comparison to check. The results obtained from the present study suggested that K2SO4 showed maximum in vitro effect on Alternaria brassicae and CaSO4 and Na2B4O7.10H2O are providing maximum reduction of disease and increase in seed yield/ha that leads to efficient alternaria blight disease management strategies in field condition. These eco-friendly chemicals can protect the crops from alternaria blight diseases and increase the production and productivity of the Indian mustard crop

Studies on the population dynamics, photoperiodism, and flight behaviour of the cabbage whitefly, Aleyrodes brassicae (WLK) Homoptera: Aleyrodidae

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Population studies of the Cabbage aphid Brevicoryne brassicae (L.) and its parasites, with special reference to synchronisation

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Interactions of Bunias orientalis plant chemotypes and fungal pathogens with different host specificity in vivo and in vitro

Tewes L-J, Müller C. Interactions of Bunias orientalis plant chemotypes and fungal pathogens with different host specificity in vivo and in vitro. Scientific Reports. 2020;10(1): 10750.Within several plant species, a high variation in the composition of particular defence metabolites can be found, forming distinct chemotypes. Such chemotypes show different effects on specialist and generalist plant enemies, whereby studies examining interactions with pathogens are underrepresented. We aimed to determine factors mediating the interaction of two chemotypes of Bunias orientalis (Brassicaceae) with two plant pathogenic fungal species of different host range, Alternaria brassicae (narrow host range = specialist) and Botrytis cinerea (broad host-range = generalist) using a combination of controlled bioassays. We found that the specialist, but not the generalist, was sensitive to differences between plant chemotypes in vivo and in vitro. The specialist fungus was more virulent (measured as leaf water loss) on one chemotype in vivo without differing in biomass produced during infection, while extracts from the same chemotype caused strong growth inhibition in that species in vitro. Furthermore, fractions of extracts from B. orientalis had divergent in vitro effects on the specialist versus the generalist, supporting presumed adaptations to certain compound classes. This study underlines the necessity to combine various experimental approaches to elucidate the complex interplay between plants and different pathogens