Prashant Swapnil

Alternaria Toxins: Potential Virulence Factors and Genes Related to Pathogenesis.

Alternaria is an important fungus to study due to their different life style from saprophytes to endophytes and a very successful fungal pathogen that causes diseases to a number of economically important crops. Alternaria species have been well-characterized for the production of different host-specific toxins (HSTs) and non-host specific toxins (nHSTs) which depend upon their physiological and morphological stages. The pathogenicity of Alternaria species depends on host susceptibility or resistance as well as quantitative production of HSTs and nHSTs. These toxins are chemically low molecular weight secondary metabolites (SMs). The effects of toxins are mainly on different parts of cells like mitochondria, chloroplast, plasma membrane, Golgi complex, nucleus, etc. Alternaria species produce several nHSTs such as brefeldin A, tenuazonic acid, tentoxin, and zinniol. HSTs that act in very low concentrations affect only certain plant varieties or genotype and play a role in determining the host range of specificity of plant pathogens. The commonly known HSTs are AAL-, AK-, AM-, AF-, ACR-, and ACT-toxins which are named by their host specificity and these toxins are classified into different family groups. The HSTs are differentiated on the basis of bio-statistical and other molecular analyses. All these toxins have different mode of action, biochemical reactions and signaling mechanisms to cause diseases. Different species of Alternaria produced toxins which reveal its biochemical and genetic effects on itself as well as on its host cells tissues. The genes responsible for the production of HSTs are found on the conditionally dispensable chromosomes (CDCs) which have been well characterized. Different bio-statistical methods like basic local alignment search tool (BLAST) data analysis used for the annotation of gene prediction, pathogenicity-related genes may provide surprising knowledge in present and future.

Antagonistic assessment of Trichoderma spp. by producing volatile and non-volatile compounds against different fungal pathogens

Abstract Trichoderma spp. are well-known biological agents that have significant antagonistic activity against several plant pathogenic fungi. In the present study, Trichoderma spp. were tested in vitro for their antagonistic activity against different spp. of Fusarium and Alternaria viz. Alternaria alternata, A. brassicae, A. solani, Fusarium oxysporum and F. solani using dual plate assay and by the production of volatile and non-volatile compounds. The results obtained revealed that Trichoderma harzianum and T. viride effectively inhibited the growth and spore production of different spp. of Fusarium and Alternaria. The highest growth inhibition was found in A. alternata 62.50% and 60.00% by non-volatile compounds of T. harzianum and T. viride, respectively. Similarly, the volatile compounds inhibit the maximum growth of A. alternata 40.00% and 35.00% by T. harzianum and T. viride, respectively. Volatile and non-volatile compounds of Trichoderma spp. were analysed by GC-MS technique and the properties of distinguished compounds showed antifungal, antimicrobial and antibiotic activities. Volatile compounds of T. harzianum and T. viride showed highest percent abundance for glacial acetic acid (45.32%) and propyl-benzene (41.75%), respectively. In case of non-volatile compounds, T. harzianum and T. viride showed D-Glucose, 6-O-α-D-galactopyranosyl- (38.45%) and 17-Octadecynoic acid (36.23%), respectively. The results of present study confirmed that T. harzianum can be used as a promising biological control agent against Alternaria and Fusarium spp. that cause diseases in various vegetables and crops.

Isolation, characterization and toxicological potential of Alternaria- mycotoxins (TeA, AOH and AME) in different Alternaria species from various regions of India

Alternaria species produce various sorts of toxic metabolites during their active growth and causes severe diseases in many plants by limiting their productivity. These toxic metabolites incorporate various mycotoxins comprising of dibenzo-α-pyrone and some tetramic acid derivatives. In this study, we have screened out total 48 isolates of Alternaria from different plants belonging to different locations in India, on the basis of their pathogenic nature. Pathogenicity testing of these 48 strains on susceptible tomato variety (CO-3) showed 27.08% of the strains were highly pathogenic, 35.41% moderately pathogenic and 37.5% were less pathogenic. Phylogenetic analysis showed the presence of at least eight evolutionary cluster of the pathogen. Toxins (TeA, AOH and AME) were isolated, purified on the basis of column chromatography and TLC, and further confirmed by the HPLC-UV chromatograms using standards. The final detection of toxins was done by the LC-MS/MS analysis by their mass/charge ratio. The present study develops an approach to classify the toxicogenic effect of each of the individual mycotoxins on tomato plant and focuses their differential susceptibility to develop disease symptoms. This study represents the report of the natural occurrence and distribution of Alternaria toxins in various plants from India.

Beneficial Microbes for Disease Suppression and Plant Growth Promotion

Plant growth-promoting microorganisms (PGPMs) constitute the microbes that are intricately associated with the plant system and may consist of rhizospheric bacteria, fungi, mycorrhiza, endophytic fungi, actinomycetes, or those having the mutualistic relationship or nonsymbiotic relationship with plants. One of the most remarkable features of these microbes is the adoption of certain ecological niches or may be occupied with multiple niches at a time in the soil ecosystem that makes way for other species to establish the mutual interactions (physical or biochemical) with other microbes (bipartite) or with plants (tripartite). The plant growth promotion by these microbes involves common mechanisms such as nitrogen fixation, siderophore production, phytohormone production, solubilization of mineral phosphates and secretion of novel secondary metabolites having positive effect on plant health. Some beneficial fungi have been found to promote plant growth through increased photosynthetic rate with improved mineral use efficiency and nutrient uptake, as inoculating these microbes with plants lead into increased chlorophyll content and biomass. These indigenous microbes have been also reported to counteract the different abiotic and biotic stress conditions. The mutual interaction observed between beneficial fungi and pathogenic microbes has been investigated at microscopic level which involves certain physical changes such as coiling of beneficial hyphae around the pathogenic hyphae and some cellular changes such as dissolution of host cytoplasm or secretion of antimicrobial compounds or lytic enzymes in the nearby localities that check the growth and reproduction of pathogenic species. The comprehensive knowledge of the functional mechanism of plant growth promotion by these microbes will help to develop strategies against damages covered by various abiotic and biotic stress conditions, and therefore will help in increasing the agricultural production at a global scale.

Effect on lycopene, β-carotene, ascorbic acid and phenolic content in tomato fruits infected by Alternaria alternata and its toxins (TeA, AOH and AME)

Abstract Tomato is considered as one of the most important sources of nutrients such as lycopene, β-carotene, flavonoids, ascorbic acid (vitamin C) and hydroxyl-cinnamic acid derivatives. The quality and quantity of nutrients in tomato fruits were decreased during the severe infection of Alternaria alternata. The present study deals with the estimation of lycopene, β-carotene, phenolic and ascorbic acid content in tomato fruits which were infected with A. alternata and its toxins such as tenuazonic acid (TeA), alternariol (AOH) and alternariol monomethyl ether (AME). The lycopene, β-carotene, ascorbic acid and phenolic content were found lowest in pathogen-infected fruits i.e. (0.66 ± 0.03 mg/g), (0.14 ± 0.01 mg/g), (1.89 ± 0.2 mg/g) and (0.58 ± 0.05 mg/g), respectively, followed by toxins-treated samples as compared to the control. The results concluded that A. alternata mostly affects the nutritional values of tomato fruits due to the combined effect of the toxins.

The Yellow Fever Outbreak in Global Perspective is Serious and of Great Concern

Yellow fever virus (YFV) is belonging to flaviviridae family which was identified as the causative agent of Yellow fever (YF), acute viral hemorrhagic disease which was first time notified by International health regulation (IHR), globally. Initially YF considered to partial control for decades but now increasing globally with the risk of local epidemic outbreaks. This review represented the occurrence of YF diseases in the 21th century and the remotely sensed satellite data are used to define climatic limits within a discriminant analytical model frame work. The study also showed the potentially co-occurrence and global epidemiology of risk maps for this disease in Africa and South East Asia in the framework of the ecological and historical forces. The aim of this study is to portray attention to this rising epidemic and to provide force for the necessary public health response.