Significance Of Vegetables For Our Healthy Diet

Introduction

Vegetables are critical segments of human eating regimen since they give basic nutrients such as carbohydrate, vitamins etc that are required to run the greater of the metabolic responses of the human body (Pujeri et al. 2015). Among different vegetable creating countries, India is the second biggest maker of vegetables after China and records for 13.4% (in excess of 97 million tons) of world creation. Most importantly, vegetables create higher returns per unit region and time. In the year 2000, the vegetable production in India was 92.8 million tons, grown over an area of 6 million hectares, which is about 3% of the gross cropped area of the country (Pujeri et al. 2015). However, as the country’s populations is expanding at the rate of 1.8 per cent per year, the interest of vegetables will be 225 million tons by 2020 and 350 million tons by 2030

Vegetables are the inseparable components parts of world cooking and are expended in various forms and preparation. Vegetables fulfil the requirement of our balanced diet because they are the major source of vitamins and nutrients. The example of vegetables that contain elevated amounts of bioactive compound which include phenolics, glucosinolates, vitamin C, vitamin E, carotenoids and selenium are Brassica vegetables, e.g. broccoli, cauliflower, cabbage, brussels sprouts and kale. These vegetables are among the most important vegetables consumed all over the world owing to their availability at local markets, cheapness and consumer preference (Herr and Buchler 2010). Phytochemicals of vegetables have been reported to prevent oxidative stress, induce detoxification enzymes, stimulate immune system, decrease the risk of cancers and inhibit malignant transformation and carcinogenic mutations (Herr and Buchler 2010; Kestwal et al. 2011). Some authors suggest that addition of glucosinolates, obtained from Brassica, to the diet may decrease both oxidative stress and also inflammation (Wu et al. 2004; Noyan Ashraf et al. 2006).

Regardless of these health advantages, the generation of vegetables in various countries is extremely low. Likewise, the yield misfortune because of plant infections in vegetables developed in various agronomic districts is high. In order to produce more and more vegetables and to protect quality and to prevent losses due to plant diseases, various agrochemicals such as synthetic fertilizers and pesticides are used indiscriminately across the globe (Ngowi et al. 2007). However, when chemicals used beyond their prescribed level cause changes in soil fertility and can affect the creation of vegetables.

Vegetables are significant in human dietary system and therefore, researchers are hunting down a protected and practical option for manage the vegetable diseases because the danger caused by phytopahogens to vegetable production across the globe and sick impacts of agrochemicals used to control phtopathogens. In this context, the use of microbes has provided some solution to the expensive chemicals (Kanjanamaneesathian 2015). To better comprehend the mechanistic basis of ailment concealment by soil microbiota and to distinguish most appropriate organisms that could upgrade vegetables production while diminishing the reliance on agrochemicals utilized in the management of vegetables diseases, here, accentuation is given.

Soilborne Phytopathogenic Diseases of Vegetabls: A General Account

The noteworthy danger to numerous vegetables and other horticultural crops is soilborne plant pathogens including bacteria, fungi, viruses and nematodes. These pathogens represent a genuine challenge because intensive farming system with thin rotational crop practices as often as possible increment their populace in the soil. Further, such nuisance organisms can endure for a long time and cannot be annihilated fully from the soil. Thus, contamination from numerous pathogens in soil can cause in a disease complex which can additionally harm consequent crop grown in the same field. Of these, fungi are the most important and major group of pathogens which infect a wide range of host plants and cause destructive and economical losses of vegetables (Salau et al. 2015). Fusarium, Rhizoctonia, Vrticillium, etc are the most common fungal pathogens causing wilt and powdery scab of most of the vegetables and assume a noteworthy part in yield loss of vegetable crops. Fungal diseases account preharvest losses in crop production up to 12% or even more in developing countries (Kim et al. 2003), while postharvest diseases account for 10–30% yield losses in developing countries (Tripathi et al. 2008; Fatima et al. 2009).

Among vegetables, because of contamination by Fusarium spp. the world is confronting 70-100% yield losses of cucumbers. In India alone, the loss is estimated at above 70% of the yield by the soilborne diseases (Egel and Martyn 2007). Vegetables are highly liable to pathogenic fungi because of their higher moisture content, low pH and nutrient compositions. The infection is activated further by the improper handling, packaging, storage and transportation (Mari and Guizzardi 1998; Sharma and Tripathi 2006). The existence of development and colonization of fungi may unfavorably influence the quality and amount of vegetables. Some of the notable fungi like Aspergillus flavus, A. parasiticus, Penicillium spp. and Fusarium spp. in addition to causing the severe diseases in various vegetables also make the food unfit for human consumption due to mycotoxins secretion (Brewer et al. 2013). Over 25% of the world’s vegetables are sullied with known mycotoxins, and in excess of 300 parasitic metabolites are accounted for to be toxic to man and animals.

The main toxic effects of mycotoxins are carcinogenicity, genotoxicity, teratogenicity, nephrotoxicity, hepatotoxicity and reproductive disorders causing damages such as toxic hepatitis, haemorrhage, oedema, immunosuppression and hepatic carcinoma (Makun 2013). Some of the common field and storage fungi in India include Alternaria alternata, Cladosporium cladosporioides, Curvularia spp., Phoma spp., Fusarium spp., Aspergillus flavus, A. niger, A. parasiticus, A. tamarii, A. nidulans, A. candidus and Penicillium spp. that cause severe diseases on a number of vegetables (Reddy et al. 2009). Fusarium spp. is imperative soilborne plant pathogens that seriously diminishes the vegetable’s production. Symptoms such as cortical decay of roots, root decay, wilting, yellowing, rosette and incomplete death on contaminated plants are the causes by a few types of Fusarium. Late blight disease, caused by Phytophthora infestans, is one of the most genuine dangers to the tomato production around the world.

Chemical Control Of Vegetables Phytopathogens

Agrochemicals play an important role in vegetables production by protecting them from different diseases (Ogundana and Dennis 1981). Chemicals are used to control phytopathogens, nonetheless, considered secure only when they are used not beyond regulatory restricts and are practiced accurately. Among agrochemicals, pesticides including fungicides are used frequently worldwide to protect crops including vegetables (Aktar et al. 2009) before and after harvest from insect pests in order to increase food security despite the fact that pesticides can have negative health effects on consumers via food chain (Damalas and Eleftherohorinos 2011). For the production of vegetables in India, about 13–14% pesticides are used due to heavy pest infestation throughout the cropping season of horticultural crops (Agnihotri 1999).

Biomanagement Of Vegetable Diseases

Among different phytopathogens, fungal pathogens by and large contribute fundamentally to the yield misfortunes in agriculture. However, so as to diminish such misfortunes and to improve crop production, fungicides have been utilized in agricultural practices worldwide. But, the environmental threats of fungicides (Thabet et al. 2016) have forced the scientists to look for alternate disease control strategies. Other than toxic effect on valuable soil microflora, rise of obstruction to fungicide among pathogens, cost and absence of suitable application/conveyance technologies to resource-poor farmers further supports the requirement for recognizing back up strategies for insect pest control. Considering these factors, the concentrate in recent times has been moved towards the use of some biological resources which are thought about naturally sheltered, cheap and effectively relevant. The answer for costly and environmentally toxic chemicals is the use of biological materials particularly non-pathogenic soil microbiota to control plant pathogens frequently called “biological control” method. Extensively, the term “biological control” include the utilization of at least one organism in isolating or combination to take out destructive microbes.

Mechanism of Disease Suppression by Biocontrol Bacteria Antibiosis

Antibiotics discharged by PGPR assume a vital part in disease suppression. The antibiotics commonly produced by different antagonistic bacteria include butyrolactones, DAPG (2,4-diacetylphloroglucinol) (Lanteigne et al. 2012), kanosamine, oligomycin A, oomycin A, phenazine-1-carboxylic acid, pyoluteorin, pyrrolnitrin, viscosinamide, xanthobaccin, and zwittermicin A (Whipps 2001). Moreover, other antibiotics such as phenazine-1-carboxamide, aerugine, rhamnolipids, cepaciamide A, pseudomonic acid, azomycin, antitumor antibiotics FR901463, caspofungins and antiviral antibiotic karalicin have also known to be antiviral, antimicrobial, insecticidal, antihelminthic, phytotoxic, antioxidant and cytotoxic effects and can also produce a plant growth-promoting effect (UlloaOgaz et al. 2015). Many of these antibiotics possess a broad-spectrum activity (Raaijmakers et al. 2002).

Conclusion

Vegetables are a standout among the most imperative segments of regular nourishment propensity. Since they provide essential micro- and macronutrients, proteins, antioxidants and vitamins to the human body. Use of artificial pesticides has been the conventional strategy for the management of phytopathogenic diseases of vegetables. However, the development of alternative strategies for the control of disease of vegetables is necessitated. The use of microbial biocontrol agents which are both cheap and naturally safe is one of the emerging but promising strategies for overseeing diseases of vegetables crops. The practice of such microbial preparations in disease management has to be sure discovered exceptionally powerful and reasonable by the growers, yet at the same time it requires greater understanding of the mechanistic basis of disease concealment. Also, there is a need to create mindfulness among growers so its utilization under various agronomic regions is expended, and the advantage of this low-cost innovation is accomplished by the vegetable’s cultivators. However, the reports/results introduced in this chapter on use of biocontrol specialists in vegetable production are probably going to profit vegetables producers bigly while decreasing the reliance in chemicals use in vegetable development. Therefore, commercialization of some of these opponents to control loss of vegetables gives off an impression of being possible and may exhibit an option in contrast to engineered pesticides.

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