Abstract
Capsicum chinense (Jacq.) cv. Scotch Bonnet pepper was inoculated with either Pseudomonas putida NCIMB-9571 or Bacillus sp. UWI-3. Each isolate was evaluated for its ability to promote plant growth and to act as biocontrol agent against tobacco etch virus (TEV). Plant growth promoting parameters examined included the ability of the isolates to produce 1-aminocyclopropane-1-carboxylate (ACC) deaminase, enhance germination efficiency and seedling vigour, stimulate root elongation, and increase shoot growth, nutrient uptake, and shoot and root dry weight. Pseudomonas putida NCIMB-9571 and Bacillus sp. UWI- 3 produced ACC deaminase and were able to promote root elongation under gnotobiotic conditions. In virus-free Scotch Bonnet pepper seedlings, Bacillus sp. UWI-3 enhanced both germination and increased seedling vigour, whereas P. putida NCIMB-9571 only increased seed germination. Pseudomonas putida NCIMB-9571 and Bacillus sp. UWI-3 significantly increased shoot length by 22 and 24%, respectively. Pseudomonas putida NCIMB-9571 and Bacillus sp. UWI-3 significantly increased shoot dry weight by 28 and 33%, respectively, and root dry weight by 51 and 42%, respectively. Pepper plants treated with P. putida NCIMB-9571 and Bacillus sp. UWI-3 and infected with TEV had significantly greater shoot growth and shoot dry weight and showed delayed viral symptom expression compared to non-plant growth promoting bacteria (PGPB) inoculated plants. Plant growth promoting bacteria inoculation of non-infected TEV pepper seedlings did not increase the levels of shoot nitrogen, phosphorus, or potassium. However, inoculation did significantly increase the levels of phosphorus in the shoots of pepper infected with TEV. Both P. putida NCIMB-9571 and Bacillus sp. strain UWI-3 were able to delay the development of TEV disease in Scotch Bonnet pepper 11 days after being infected with the virus. Of the two bacteria tested, Bacillus sp. UWI-3 had greater disease suppressive activity and plant growth promoting ability.
