Abstract
A deep-rooting upland rice variety (Kinandang Patong) was evaluated for its growth response to bio-fertilization at early stages. Five non-native plant growth-promoting bacteria previously isolated from yams (Dioscorea spp.) were inoculated to upland rice under growth chamber and greenhouse conditions. Effects of the inoculation varied depending on bacterial strains and growing conditions. Growth of 14-day rice seedlings was improved by all tested bacterial strains. Under growth chamber, the strain S-333 increased plant length, shoot dry weight and nitrogen content as compared to the control, but total dry weight, nitrogen uptake, leaf chlorophyll content and number of tillers were higher with N fertilizer application. Under greenhouse conditions, most rice growth parameters were improved by inoculation with the strain S-7. The correlations between the bacterial plant-growth-promoting traits and rice growth parameters under growth chamber conditions were all negative for phosphate solubilization indexes. Our results suggest that bacterial inoculation can replace half (S-343 and S-611) of or the full (S-7) rate of chemical N fertilizer required, depending on bacterial strains and growing environments, although δ15N value in control plants was lower than in inoculated plants under growth chamber conditions, suggesting that the bacteria improve rice growth through mechanisms other than biological nitrogen fixation.
Highlights
Rice (Oriza sativa L.) is one of the world’s most important cereal crops
The identification of plant growth-promoting bacteria with a large host range is important and agronomically relevant to increase the use of bio-fertilizers in replacement of part of chemical fertilizers in the context of sustainable agricultural production
The current study tested the effects of cross inoculation with non-native bacteria on upland rice growth
Summary
Rice (Oriza sativa L.) is one of the world’s most important cereal crops. Plant growth-promoting bacteria (PGPB) include rhizospheric and endophytic bacteria that promote growth and yields of their host plants. PGPB have been isolated from various environments such as soil [2,3] and plants [4,5,6]. Several diverse PGPB were reported and found to increase biomass and grain yield as well as nutrients uptake and phytohormones production [7]. Bacteria genera such as Pseudomonas, Bacillus, Enterobacter, and Micrococcus, among which plant growth-promoting
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