Challenges, Future Prospects and Conclusions
The challenges in developing PGPR for commercial application include screening and selection of potential PGPR strain, microbial ecology and interaction, fermentation technology and shelf life of formulations, patent protection and prohibitive registration cost, awareness, training and education shortfalls and lack of multidisciplinary approach. Another challenge of using PGPR is natural variation. It is difficult to predict how an organism may respond when placed in the field (compared to the controlled environment of a laboratory). Another challenge is that PGPR are living organisms. They must be able to be propagated artificially and produced in a manner to optimize their viability and biological activity until field application. Technology challenges include delivery system and biopesticides quality.
PGPR-mediated agriculture is now gaining worldwide importance and acceptance for an increasing number of crops and managed ecosystems as the safe method of pest control. Biocontrol has untapped potential and is underused, underexploited, underestimated, often untried and therefore unproven. The new tools of recombinant DNA technology, mathematical modelling and computer technology combination with a continuation of the more classical approaches such as importation and release of natural enemies and improved germplasm, breeding and field testing should quickly move biocontrol research and technology into a new era. Although activity and effects of biocontrol have been reported for a number of antagonists, the underlying mechanisms are not fully understood. This deficiency in our knowledge often hinders attempts to optimize the biological activity by employing tailored application strategies. Biocontrol efficacy of PGPR may be improved by genetically engineering them to overexpress one or more of these traits so that strains with several different antiphytopathogen traits can act synergistically. New insights are certain to be gained from the recently published genomic sequence of Pseudomonas fluorescens Pf5, which already has revealed biosynthetic potential for many previously undetected compounds likely to contribute to the broad antifungal activity of this strain. More detailed studies are needed on the composition of the rhizosphere population, the effect of cultivar on bacterial population dynamics, the influence of inoculum density on antagonistic activity, the survival of inoculum under adverse conditions and the role of environmental conditions in altering the activity of rhizobacteria. An attempt to overcome problems of varying efficacy may be attained by strain mixing, improved inoculation techniques or gene transfer of active genetic source of antagonists to the host plant. The soil microbes are active elements for soil development and the basis of sustainable agriculture.
KeywordsBiocontrol Agent Pseudomonas Fluorescens Patent Protection Fermentation Technology PGPR Strain
- Gouws LM (2009) The molecular analysis of the effects of lumichrome as a plant growth promoting substance. Dissertation, University of Stellenbosch, South AfricaGoogle Scholar
- Holguin G, Glick BR (2001) Expression of the ACC deaminase gene from Enterobacter cloacae UW4 in Azospirillum brasilense. Microbial Ecol 41:281–288Google Scholar
- Larkin RP, Roberts DP, Gracia-Garza JA (1998) Biological control of fungal diseases. In: Hutson D, Miyamoto Y (eds) Fungicidal activity, chemical and biological approaches. Wiley, New York, pp 149–191Google Scholar
- Nakkeeran S, Fernando WGD, Siddiqui ZA (2005) Plant growth promoting rhizobacteria formulations and its scope in commercialization for the management of pests and diseases. In: Siddiqui ZA (ed) PGPR: biocontrol and biofertilization. Springer, Dordrecht, pp 257–296Google Scholar
- Sabitha D, Nakkeeran S, Chandrasekar, G (2001) Trichoderma – bioarsenal in plant disease management and its scope for commercialization. In: Proceedings of the Indian Phytopathological Society, Southern Zone meeting, 10–12 Dec 2001, Indian Institute of Spice Research, Calicut, pp 43–55Google Scholar