The export oriented agricultural and horticultural crops depends on the export of residue free produce and has created a great potential and demand for the incorporation of biopesticides in crop protection. To ensure the sustained availability of biocontrol agent’s mass production technique and formulation development protocols has to be standardized to increase the shelf life of the formulation. It facilitates the industries to involve in commercial production of plant growth promoting rhizobacteria (PGPR). PGPR with wide scope for commercialization includes Pseudomonas fluorescens, P. putida, P. aeruginosa, Bacillus subtilis and other Bacillus spp. The potential PGPR isolates are formulated using different organic and inorganic carriers either through solid or liquid fermentation technologies. They are delivered either through seed treatment, bio-priming, seedling dip, soil application, foliar spray, fruit spray, hive insert, sucker treatment and sett treatment. Application of PGPR formulations with strain mixtures perform better than individual strains for the management of pest and diseases of crop plants, in addition to plant growth promotion. Supplementation of chitin in the formulation increases the efficacy of antagonists. More than 33 products of PGPR have been registered for commercial use in greenhouse and field in North America. Though PGPR has a potential scope in commercialization, the threat of certain PGPR (P. aeruginosa, P. cepacia and B. cereus) to infect human beings as opportunistic pathogens has to be clarified before large scale acceptance, registration and adoption of PGPR for pest and disease management.

Plant Growth Promoting Rhizobacteria Formulations and its Scope in Commercialization for the Management of Pests and Diseases

Vegetable crops are frequently infected by fungal pathogens, which can include seedborne fungi. In such cases, the pathogen is already present within or on the seed surface, and can thus cause seed rot and seedling damping-off. Treatment of vegetable seeds has been shown to prevent plant disease epidemics caused by seedborne fungal pathogens. Furthermore, seed treatments can be useful in reducing the amounts of pesticides required to manage a disease, because effective seed treatments can eliminate the need for foliar application of fungicides later in the season. Although the application of fungicides is almost always effective, their non-target environmental impact and the development of pathogen resistance have led to the search for alternative methods, especially in the past few years. Physical treatments that have already been used in the past and treatments with biopesticides, such as plant extracts, natural compounds and biocontrol agents, have proved to be effective in controlling seedborne pathogens. These have been applied alone or in combination, and they are widely used owing to their broad spectrum in terms of disease control and production yield. In this review, the effectiveness of different seed treatments against the main seedborne pathogens of some important vegetable crops is critically discussed.

https://www.d3a.univpm.it/sites/www.d3a.univpm.it/files/d3a/Lavori%20scientifici/Mancini%20and%20Romanazzi%2C%202014%20Pest%20Management%20Science.pdf

Seed treatments to control seedborne fungal pathogens of vegetable crops

Plant growth-promoting rhizobacteria (PGPR) colonize the roots of plants following inoculation onto seed before planting and enhance plant growth and/or reduce disease, nematode or insect damage. There has been much research interest in PGPR and there is now an increasing number of PGPR being commercialized for crops. Organic growers may have been promoting these bacteria without knowing it. The addition of compost and compost teas promote existing PGPR and may introduce additional helpful bacteria to the field. The absence of pesticides and the more complex organic rotations likely promote existing populations of these beneficial bacteria. However, it is also possible to inoculate seeds with bacteria that increase the availability of nutrients, including solubilizing phosphate, potassium, oxidizing sulphur, fixing nitrogen, and chelating iron and copper. PGPR such as Pseudomonas and Bacillus species have attracted much attention for their role in reducing plant diseases. The work to date is very promising and may offer organic growers with some of their first effective control of serious plant diseases. Some PGPR use scarce resources, and thereby prevent or limit the growth of pathogenic microorganisms. Even if nutrients are not limiting, the establishment of benign or beneficial organisms on the roots limits the chance that a pathogenic organism that arrives later will find space to become established. Numerous rhizosphere organisms are capable of producing compounds that are toxic to pathogens like HCN.

Plant Growth-Promoting Rhizobacteria (PGPR)

Biological disease control is an attractive alternative strategy for the control of plant diseases. Meanwhile, it also provides practices compatible with the goal of a sustainable agricultural system. Understanding the mechanisms of biological control of plant diseases through the interactions between antagonists and pathogens may allow us to select and construct the more effective biocontrol agents and to manipulate the soil environment to create a conducive condition for successful biocontrol. Many factors have to be considered in deciding whether a biological system is feasible for the control of a particular pathogen. Of prime importance is the availability of a suitable antagonist capable of maintaining itself on the host plant. The environment under which the crop is grown will play a significant part in determining whether effective population levels of an antagonist can be established in competition with the existing microflora. Environment may also govern the choice of antagonist; for example, yeasts can survive on leaves more readily than non-spore-forming bacteria under adverse humidity conditions. It is essential that the primary mechanism by which antagonism is brought about should be known. A variety of biological controls are available for use, but further development and effective adoption will require a greater understanding of the complex interactions among plants, people and the environment. With people turning more health conscious Biological control seem to the best alternative to disease suppression. Bio-agents bring the disease suppression with no environmental hazards. Research has proved that the bio agents trigger the growth of plants. Bio agents themselves being non-pathogenic to plants need to be formulated in a way that favours the activity and survival of microbe it contains. Moreover, the organism that suppresses the pathogen is referred to as the biological control agent (BCA). More broadly, the term biological control also has been applied to the use of the natural products extracted or fermented from various sources. These formulations may be very simple mixtures of natural ingredients with specific activities or complex mixtures with multiple effects on the host as well as the target pest or pathogen. And, while such inputs may mimic the activities of living organisms, non-living inputs should more properly be referred to as biopesticides or biofertilizers, depending on the primary benefit provided to the host plant. Over the past few years, the novel applications of molecular techniques have broadened our insight into the basis of biological control of plant diseases. New molecular approaches have been available for assessment of interaction between the antagonist and pathogen, ecological traits of antagonists in rhizosphere and improving the efficacy of bacterial, fungal and viral biocontrol agent. Currently, biological control will thus be an alternative strategy for the control of plant diseases given the history of fungicides in the near future. However, other methods in IPM for crop disease control are still necessary in various environmental conditions, because an agro-ecosystem is a variable and functioning system that includes several factors that influence disease and crop development. Consequently, for economic threshold, other control strategies of IPM besides biological control should be also considered and applied to effectively reduce the disease development and the yield loss of crops in the different crop systems. Keywords: Biocontrol, biofumigation, microbial antagonism, natural compounds, pathogen.

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Review on Concepts in Biological Control of Plant Pathogens

The long-term activity of some antagonistic fungal and bacterial agents against the incidence of faba bean root rot incidence was evaluated when applied as a bio-priming seed treatment. The inhibitory effect of antagonistic fungi and bacteria against the linear growth of root rot pathogenic fungi was evaluated in vitro. The tested inhibitor factor in this study was the antagonistic agents applied as either growth culture discs or bio-primed faba bean seeds. The inhibitor effect of Trichoderma viride, T. harzianum, Bacillus subtilis and Pseudomonas fluorescens was significantly higher than T. hamatum and B. cereus, respectively. Similar results were also obtained when the antagonistic agents were applied as bio-primed seeds. Under greenhouse conditions, all the tested fresh and 2 months-stored, bio-primed faba bean seeds showed a highly significant effect causing complete reduction of root rot incidence at both pre — and post-emergence stages of plant growth compared with the control treatment. Stored seeds at 4 and 6 months showed a less protective effect against the incidence of disease. After 3 months of storage under field conditions, the antagonistic agents could protect seeds against infection by root rot pathogens at both pre- and post-emergence stages. However, after 6 months of storage, a lower protective effect was observed. No significance was observed between seeds primed only with adhesive agents and the untreated control. Promising applicable techniques could be suggested in light of the results obtained in the present study. The use of bio-primed seeds might be considered as a safe, cheap and easily applied biocontrol method against these soilborne plant pathogens.

Long-term activity of bio-priming seed treatment for biological control of faba bean root rot pathogens

Five microbial plant growth promoters or biocontrol agents (Pseudomonas fluorescens CHA0, Pseudomonas sp. AB842, Bacillus subtilis MBI600, Trichoderma harzianum T22 and T. virens G20) were assessed for ability to proliferate on seeds of carrot, parsnip and leek. In small-scale priming systems, both pseudomonads and MBI600 (when applied as cells) at levels between 105 and 106 cfu g−1 seed were able to colonise all seeds at the end of priming (240 h) despite initial poor recovery after addition of the cells in some cases. Pf CHA0 was a particularly aggressive seed coloniser often comprising the total pseudomonad population at the end of priming. Drying the seed after priming resulted in <1 log10 cfu g−1 seed loss for the pseudomonads but greater losses for MBI600 on carrot and leek seed. Application of spores of MBI600 resulted in little loss in cfu g−1 seed following addition of the cells and these levels were maintained throughout the priming period and after drying back. Both T22 and G20 were recovere...

B. Wright

Papers

Application of Beneficial Microorganisms to Seeds during Drum Priming