Synergistic Effects of Plant Growth-Promoting Microorganisms on Growth and Development of Terap (Artocarpus odoratissimus Blanco) Seedlings

Artocarpus odoratissimus Blanco, or terap, is an indigenous fruit of Borneo that is popular for its strong fruity aroma and sweet juicy flesh, which is gaining visibility in the local fruit industry. Due to increasing demands and attributes of this fruit in recent years locally and internationally, the species has great potential to be commercialized. Selecting an appropriate substrate is one of the most pivotal stages in producing quality seedlings in a nursery. Consequently, the present study focuses on evaluating the synergistic effects of the substrate composition with effective microorganisms, i.e., Trichoderma harzianum, Bacillus subtilis, and Arbuscular mycorrhizal fungi (AMF), and in all possible combinations, on the growth and development of the A. odoratissimus seedlings. The pot experiment was designed following the Completely Randomized Design (CRD) with eight replications per treatment. Among the substrates, significantly higher (p<0.05) plant height was recorded in the seedlings treated with combined inoculants, T7 (Soil + AMF + T. harzianum + B. subtilis) at 47.13±10.80 cm or in a single inoculant, T3 (Soil + B. subtilis) at 46.83±2.63 cm. Subsequently, T7 and T3 have significantly improved the collar diameter and leaf area of A. odoratissimus seedlings. Concerning the physiological parameters, the synergistic triple treatment (T7) improved the underground fresh and dry biomass production at 32.33±3.21 g and 11.66±1.08 g, respectively. The same combination exhibited a more significant (p<0.05) Dickson’s Quality Index (0.72±0.03), improving the original development of A. odoratissimus seedlings. Microbial application tended to mitigate ion imbalances in plants and significantly affected the soil total nitrogen, available P, and available K and pH. These effects were most prominent in the treatments comprising triple inoculations of T7. Results suggest that the combination of T. harzianum, B. subtilis, and AMF leads to interactions that may potentially improve seedling development and crop productivity in A. odoratissimus.