The survival of plant growth promoting microorganisms in peat inoculant as measured by selective plate counting and enzyme-linked immunoassay

Abstract

Achieving specific counting of plant growth promoting (PGP) microorganisms maintained at high numbers in inert carriers such as peat is an important objective for the inoculation of field crops such as cereals. In this paper, methods based on selective media together with strain-specific counting using enzyme-linked immunoassay (ELISA) were examined. Selective plate counting was developed by screening four commercial PGP biofertiliser strains for resistance to antibiotics. ELISAs for each strain were developed and calibrated by purifying polyclonal antibodies, testing sample pre-treatment strategies, and investigating the effect of culture age on standard curves. Selective plate counting proved to be more accurate than the ELISA methodology, confirming that all microbial strains survived for at least 1 month in sterile peat without loss in viable numbers, and further demonstrated growth inhibition of the strain Candida tropicalis HY when co-inoculated with the other strains Pseudomonas fluorescens 1 N, Bacillus amyloliquefaciens E19 and Bacillus subtilis B9. This is the first known study to have investigated the dynamics of PGP microorganisms in multi-strain inoculants and demonstrates the utility and hitherto unmentioned drawbacks of two different low-cost counting methods for biofertiliser quality control. Such information is vital for the adoption and success of non-rhizobial PGP biofertilisers for sustainable agriculture.

Effects of plant growth promoting bacterial isolates from Kavango on the vegetative growth of Sorghum bicolor

“…Therefore, combination treatments were made up of one phosphate solubilizing isolate (P. stutzeri ACM2-32), a N 2 -fixer and an isolate with antifungal capability. The inoculum treatments were prepared according to Rose et al (2011) with slight modifications. Treatments (Table 2) consisted of 50 g palm peat and 20 ml of bacteria solution, that is, 3 ml bacteria-0.85% NaCl suspension + 17 ml sterile distilled water for single bacterial treatments and 3 ml bacteria-0.85% NaCl suspension (×3 different isolates) + 11 ml sterile distilled water for combination bacterial treatments, whereas 3 ml 0.85% NaCl + 17 ml sterile distilled water was the control.…”

Bioencapsulation of microbial inoculants for better soil–plant fertilization. A review

“…The carrier is usually a convenient and economical material, which is able to release slowly viable cells in highquality physiological condition, containing one or more beneficial bacteria (Bashan 1998). There are a number of alternative carriers and formulations for delivery of bacteria: talc (Kloepper and Schroth 1981), vermiculite, perlite (Temprano et al 2002), polyacrylamide (Dommergues et al 1979), carrageenan (Cassidy et al 1996), alginate (Bashan 1986), alginate-starch (Schoebitz et al 2012), alginate-humic acid (Young et al 2006), and powder formulations (Amiet-Charpentier et al 1999;Denton et al 2009), although the most practical carriers used worldwide on commercial crops are peats (Rose et al 2011), liquids (Albareda et al 2008;Diaz-Zorita and Fernandez-Canigia 2009), and clays (Goss et al 2003).…”

Biological alternates to synthetic fertilizers: efficiency and future scopes

“…Bacillus edaphicus stimulates potassium uptake in cotton, rape and wheat (Basak and Biswas, 2009), Paenibacillus glucanolyticus enhanced the dry weight of black pepper by increasing potassium uptake (Han and Lee, 2005), Bacillus mucilaginosus enhance potassium mobilization in Sudan grass (Goss et al 2003). Bacillus mucilaginosus coinoculation with the phosphate-solubilizing Bacillus megaterium promoted the growth of eggplant, pepper and cucumber (Rose et al 2011).…”