Evaluation of lettuce and tomato varieties-plant growth promoting rhizobacteria (PGPR) interaction under upland and lowland conditions

Field trials were conducted to evaluate the response of different lettuce and tomato varieties to inoculation with plant growth promoting bacteria (PGPR). BioGroe inoculant developed at BIOTECH was used in the trial. Nine commercial lettuce varieties were evaluated during dry season in a split-plot designed field experiment. Significant variety-treatment interaction was obtained only in terms of average plant weight and P content. Nitrogen and potassium uptake were not significantly influenced by inoculation. For tomato, two trials were conducted under upland condition to determine the response of open-pollinated (OP) and hybrid varieties to PGPR inoculation at two fertilization rates. For dry season trial, inoculation significantly increased the number of branches formed from 7 to 9 when only half of the recommended fertilizer rate was applied. Increase was not observed under full fertilizer rate. Similar observation was observed in terms of the number of flower clusters formed in which inoculation increased the number of floral clusters by 30% when half of the recommended fertilizer was applied. On the other hand, the OPs responded to inoculation in terms of the significantly high number of floral clusters than the hybrids. Nitrogen and P content were not significantly influenced by inoculation and fertilization. Interaction between fertilizer rate, inoculation and variety was also observed in terms of flower dry weight and root dry weight. The field data obtained however did not reflect the beneficial effect of PGPR inoculation because of poor plant stand due to bacterial wilt and virus infestations. Significant variety-inoculation treatment interaction in terms of total yield per plant was obtained in the wet season trial. PGPR inoculation significantly increased the total yield of open-pollinated variety, Rossana compared to the other varieties. On the other hand, the average fruit weight of tomato variety Caraibo was significantly enhanced by inoculation under full fertilizer rate. The number of branches of varieties, Rossana, Discovery and Atlas were also significantly increased by inoculation across fertilizer rates. The tomato trial conducted under lowland condition showed significant variety-inoculation interaction in terms of dry matter yield and flower dry weight. Only two varieties, Assunta and Atlas showed positive response to inoculation in terms of the above parameters evaluated. Yield data were not obtained from the trial due to the heavy rains in May which terminated the trial prematurely as a result of waterlogging.