Weed Suppression by Deleterious Rhizobacteria is Affected by Formulation and Soil Properties

Abstract

Deleterious rhizobacteria (DRB) suppress weed growth in field tests and are considered potential weed biological control agents. This study compared the relative inhibitory action of the DRB Pseudomonas fluorescens strain G2-11 in different formulations, corn gluten meal (CGM), and semolina flour, toward wheat (Triticum aestivum L.), green foxtail (Setaria viridis (L.) Beauv.), and velvetleaf (Abutilon theophrasti Medik) seeds and seedlings in soil assays. Strain G2-11 successfully established in semolina flour as an inoculum formulation but was incompatible with CGM presumably because of antibacterial factors present. The effect of DRB and plant products on seed germination and plant growth were influenced by soil, with the strongest effects seen in fine sandy loam. Semolina flour alone reduced root growth of all target plants except for velvetleaf in silt loam. Green foxtail seed germination was greatly reduced by strain G2-11. With the exception of wheat seedling growth, strain G2-11 enhanced growth-suppressive qualities of semolina flour. Results suggest that natural plant products such as CGM and semolina flour alone and formulated with

Biological control of great brome (Bromus diandrus) in durum wheat (Triticum durum): specificity, physiological traits and impact on plant growth and root architecture of the fluorescent pseudomonad strain X33d

“…2 Root systems of great brome and durum wheat: great brome (a), great brome inoculated with P. trivialis X33d (b), great brome co-seeded with durum wheat (c), great brome coseeded with durum wheat inoculated with P. trivialis X33d (d), durum wheat (e), durum wheat inoculated with P. trivialis X33d (f), durum wheat co-seeded with great brome control (g), durum wheat co-seeded with great brome inoculated with P. trivialis X33d (h) Values are means ± standard error TRL: total root length, TSA: total root surface area, TV: total root volume, T: number of tips and T/TL: root branching degree inhibited significantly the growth of great brome and promoted the development of four out of seven tested crops, thus resulting in a highly specific great brome growth suppression and non-specific plant growth promotion. Similar behavior has been shown by P. fluorescens D7, which reduced downy brome (Bromus tectorum) growth by 40% and slightly stimulated winter wheat (Triticum aestivum) (Kennedy et al 1991) and seed rape (Brassica rapa L.) (Kennedy et al 2001) and by P. fluorescens G2-11, able to suppress growth of several weeds and to enhance the growth of soybean (Glycine max L.) and winter wheat (Triticum aestivum) (Li and Kremer 2006;Zdor et al 2005). Nevertheless, the dual function (growth suppression and stimulation) may not be present in the same strain.…”

“…The efficacy of our bacterial strain to inhibit the growth of the weed and to promote the durum wheat growth varied according to the substrate used in the two experiments (the specificity test and of the plant growth and root architecture experiment). Such a substrate-effect on the effectiveness of fluorescent pseudomonads to suppress weed growth or promote plant growth has been previously shown in relation to the soil type (Horwath et al 1998), fertility conditions (Gamalero et al 2002) and clay content (Zdor et al 2005).…”

Enhanced Efficiency of Medicinal and Aromatic Plants by PGPRs

“…However, inhibition of seed germination has also been recorded when Ambrosia artemisiifolia seeds were inoculated with P. fluorescens (Vrbnicanin et al 2011). Moreover, P. fluorescens has been classified as either deleterious rhizobacteria (DRB) (Zdor et al 2005) or PGPR (Jaleel et al 2007), depending on the experimental conditions in which bacterial cultures develop. Growth promotion and beneficial effects conferred by PGPRs may involve various mechanisms of action.…”

Microbial Weed Control and Microbial Herbicides

“…Zdor et al (2005) studied effects of DRB (Pseudomonas fluorescens strain G2-11) in combination with corn gluten meal and semolina flour in soil assays using weed and crop species. Zhang et al (2010) studied the stability of pyoluteorin, a polyketide metabolite produced by fluorescent pseudomonads that has shown potential to control weeds, among other pests.…”