a b s t r a c tThere is a growing body of evidence that demonstrates the potential of various microbes to enhance plant productivity and yield in cropping systems. Realizing the potential of beneficial microbes requires an understanding of the role of microbes in growth promotion, particularly in terms of fertilization and disease control, the underlying mechanisms and the challenges in application and commercialization of plant growth-promoting (PGP) microbes. This review focuses specifically on the use of PGP microbes in the cotton industry and summarizes the commercial bioinoculant products currently available for cotton; highlighting factors that must be considered for future development of PGP microbial products for the cotton industry. Given the paucity of information on beneficial microbes for cotton production systems in comparison to those for other cropping systems (e.g. legumes and grains), a snapshot of the current research is critical in light of the increased interest in cotton inoculants, mainly in developing countries such as India, and the overall increased interest in PGP applications as part of promoting sustainable agriculture.

Azospirillum brasilense is a nitrogen fixing bacterium that has been shown to have various beneficial effects on plant growth and yield. Under normal conditions A. brasilense exists in a motile flagellated form, which, under starvation or stress conditions, can undergo differentiation into an encapsulated, cyst-like form. Quantitative RT-PCR can be used to analyse changes in gene expression during this differentiation process. The accuracy of quantification of mRNA levels by qRT-PCR relies on the normalisation of data against stably expressed reference genes. No suitable set of reference genes has yet been described for A. brasilense. Here we evaluated the expression of ten candidate reference genes (16S rRNA, gapB, glyA, gyrA, proC, pykA, recA, recF, rpoD, and tpiA) in wild-type and mutant A. brasilense strains under different culture conditions, including conditions that induce differentiation. Analysis with the software programs BestKeeper, NormFinder and GeNorm indicated that gyrA, glyA and recA are the most stably expressed reference genes in A. brasilense. The results also suggested that the use of two reference genes (gyrA and glyA) is sufficient for effective normalisation of qRT-PCR data.

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Each of these two factors may provide valuable information regarding the vulnerability of PCa patients to anxiety, depression, or chronic stress. Suggestions are made for their inclusion in clinical settings.