Screening rhizobacteria for improving the growth, yield, and oil content of canola (Brassica napus L.)

Abstract

One hundred rhizobacteria previously isolated from the rhizospheres of Brassica species were screened for their growth promoting activity in Brassica napus L. under gnotobiotic conditions. Results revealed that 58% of the rhizobacteria increased root length (up to 139%), 39% enhanced shoot length (up to 78%), and shoot weight (up to 72%) of Brassica napus L. Based upon growth promotion of B. napus seedlings under gnotobiotic conditions, 10 promising plant-growth-promoting rhizobacteria (PGPR) were selected and tested for their effectiveness in growth promotion, yield, and oil content of B. napus grown in pots. The pot trials revealed that inoculation with selected PGPR increased plant height, root length, number of branches per plant, stem diameter, number of pods per plant, 1000-grain weight, grain yield, and oil content over a range of 7–57% above the uninoculated control. These isolates were then assayed for their ability to produce auxins in vitro in the presence and absence of L-tryptophan. Regression analysis showed that in vitro auxin production by these bacteria was significantly related to the number of branches and oil content of B. napus. It is highly likely that improvement in growth and yield of the inoculated plants is due to an increase in the number of branches per plant, since there was a positive correlation of this growth parameter with the number of pods per plant, 1000-grain weight, grain yield, and seed oil content. Results indicated that simultaneous screening of rhizobacteria for growth promotion under gnotobiotic conditions and in vitro production of auxins could be a useful approach for selecting effective PGPR.

ACC-deaminase and/or nitrogen-fixing rhizobacteria and growth response of tomato (Lycopersicon pimpinellfoliumMill.)

“…auxin) and ability to hydrolyze the ACC in plant roots . Asghar et al (2004) reported a 3.5-fold increase in auxin production by rhizobacteria with L-TRP than without L-TRP. It has been reported that other traits, e.g.…”

Screening rhizobacteria for biological control of Fusarium root and crown rot of sorghum in Ethiopia

“…A strain of Bacillus cereus UW85 has previously been reported to suppress plant diseases caused by Oomycetes (Silo-Suh et al, 1994 andStabb, 1996) due to the production of the antibiotics Zwittermicine (Milner et al, 1996a) and Kanosamine (Milner et al, 1996b). Indirect promotion of plant growth occurs when PGPR lessen or prevent the deleterious effects of phytopathogens through mechanisms such as antibiosis against the pathogens (Asghar et al, 2004). Elizabeth and Handelsman (1999) suggested that the effect of Bacillus cereus on the microbial community in the rhizosphere is perhaps exerted by stimulating growth of other bacteria that stimulate root growth, antagonize the pathogen or induce resistance in the host.…”

Evaluation of Biological Control Traits in Some Isolates of Fluorescent Pseudomonads and flavobacterium

“…Mechanisms of biological control of plant pathogens by fluorescent pseudomonads generally involve production of bacterial metabolites such as siderophores, hydrogen cyanide, extra cellular lytic enzymes and induced systemic resistance (O,Sullivan and O,Gara, 1992). Furthermore, Flavobacterium is an efficient rhizosphere genus in promotion of plant growth (Asghar et al, 2004). Nevertheless, to our knowledge, no report has been published on biological control ability of this genus.…”