Thesis (BS Biology) -- University of the Philippines Mindanao, 2007

The effect of three local rhizospheric strains of bacteria, Rh1_MS-CO, Rh2-MS-CO and Rh3-MS-CO on seed germination and root growth in Bt and conventional corn (NK5447) was investigated. The effect of gibberellic acid (GA3) on seed germination was also explored. Regardless of treatment, Bt seeds tended to show a higher percent germination (97.22%-100%) and germination rate (0.62-0.72) than conventional seeds (44.44% to 52.78%), (0.21-0.29). The lower germination response in conventional corn may was accounted to the low physical vigor of seeds used. For each treatment, radicle lengths of Bt seeds were significantly higher than those of conventional seeds except those seeds treated with Rh1-MS-CO and Rh3-MS-CO filtrates. For Bt corn, radicle length was highest among seeds treated with 0.005 mg/mL GA3 but decreased at higher GA concentrations of 0.05 and 0.5 mg/mL. Radicle length of seed treated with Rh2-MS-CO filtrate was significantly higher than those treated with filtrates with GA3. A Rh3-MS-CO and untreated seeds but significantly lower than those treated with 0.05 mg/mL. a similar trend was observed among conventional seeds except the seeds treated with 0.05 mg/mL. GA3 did not differ significantly with those treated with 0.5 mg/mL. Various factors influence bacterial production of substances influential to plant growth. Thus, optimization of cultural conditions as well as concentrations of hormone precursors to be amended on growth medium in needed to further assess the ability of the isolates to influence germination and root growth in corn. For root growth experiment, cell suspensions were used as plant inocula. Root length and root dry weight of bacteria treated seedlings did not differ from each other for both Bt and conventional varieties. Such finding, however, does not dismiss the ability of the three isolates to promote plant growth as other PGPR parameters have not yet been characterized. Optimal levels of bacterial inocula should also be determined as the concentration used in the study may be inhibitory to corn root growth