Efficacy of Bacillus spp. Isolates for Application as Biofertilizer in Tomato (Solanum lycospersicum L.) Cultivation

Abstract

Certain species of Bacillus are considered rhizobacteria that promote plant growth, inhibit the growth of plant pathogens and deleterious rhizospheric microorganisms. The aim of this study was to determine the stimulatory effect of Bacillus subtilis KBM1 and Bacillus venezensis KBM1 on the growth and disease reduction of tomato plants in Côte d'Ivoire. In this respect, three substrates consisting of soil only, sawdust only and a mixture of soil and sawdust were inoculated with the two bacteria, then left to ferment for twenty-four (24) hours. The biofertilizers obtained after fermentation were used to assess their effects on the development of potted tomatoes. Growth parameters, infection rate and mortality rate of tomato plants were measured regularly during 6 weeks of cultivation. A search for tomato pathogenic fungi was carried out to demonstrate the efficacy of Bacillus strains isolates on plant health. The results obtained showed that Bacillus subtilis KBM1 and Bacillus venezensis KBM1 had a positive impact on plant growth of tomato plants grown. Infection and mortality rates of 0% were observed for tomato plants grown on the three substrates inoculated with these two bacteria. No pathogenic fungi were isolated from the organs of tomato plants grown on the three substrates fermented with the bacteria. However, on untreated control plants, a variety of pathogenic fungi, namely Fusarium sp, Phytophtora sp, Cladosporium sp, Rhizoctonia sp, Colletotrichum sp, Penicillium sp, Rhizopus sp and Trichoderma sp were observed. However, the Bacillus subtilis KBM1 treatment stood out from Bacillus venezensis KBM1 with the best results for the growth parameters measured. In view of these results, these two bacteria could be used to produce an effective biofertilizer for tomato cultivation in Côte d'Ivoire.