Growth enhancement and root colonization of sugarcane by plant growth-promoting bacteria
2008
Villegas, L.C., Philippines Univ. Los Baños, College, 4031 Laguna (Philippines). Inst. of Biological Sciences | Paterno, E S., Philippines Univ. Los Baños, College, Laguna (Philippines). Crop Science Cluster
Plant growth promoting bacteria were isolated from the sugarcane rhizosphere. They were found to posses growth enhancing activities which included indole acetic acid production, phosphate solubilization, siderophore production and nitrogen fixation. Physiological, biochemical and genomic characterizations indicated that the two selected isolates, designated as LV7 and LV10, belong to Pseudomonas genus. Plant growth promotion due to bacterial inoculation was evaluated at the in-vitro shoot multiplication and root development stages of sugarcane. LV10 significantly increased the number of tillers by 31% and the fresh shoot weight by 20% above the uninoculate control. LV7 significantly increased the fresh shoot weight by 17% and promoted the in-vitro rooting of the plantlets by 55% above the uninoculated control. Under nursery conditions, both isolates enhanced the growth of sugarcane. Inoculated plants were significantly taller and accumulated significant amounts of biomass. Shoot dry weight increased up to 61% and root dry weight up to 67%. Microbiological analyses revealed that both bacteria survived and persisted in the rhizosphere and within sugarcane tissues. The mode of invasion and extent of colonization of sugarcane roots was studied using LV7-tagged with GUS A gene. Microscopic examination of the x-gluc stained plants revealed that LV7 was an invasive colonizer capable of invading sugarcane root via root tips and fissures created by the emerging lateral roots. LV7 was found to colonize the root cortex and vascular bundles. Due to the growth promoting activities and invasive colonization of LV7 and LV10, these strains may be most suited as inoculants for sugarcane.
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