Dark septate endophytic fungi of Neolamarckia cadamba (Roxb.) Bosser and their potency for improving the seedling morphophysiological traits

Neolamarckia cadamba is a fast-growing tropical tree species increasingly cultivated in community and industrial plantation forests. However, its growth on many sites is less than optimal, especially in marginal drylands. Dark septate endophytes (DSEs) may offer a viable solution to improve seedling quality and enhance adaptation to marginal environments. The research aimed to isolate, identify, and characterize the DSEs species associated with N. cadamba, and to test their effect on improving its seedling quality. The six DSEs symbionts of N. cadamba successfully isolated and identified were CPGS-1, CPGS-3, CPPS-9, CKKS-3, CKKS-5, and CGKR-9. Phylogenetic analyses revealed that the identified isolates CPGS-1 and CPPS-9 were closely related to Dothideomycetes sp. (69%). Isolates CPGS-3, CKKS-3, and CKKS-5 were closely related to the genus Knufia (99%). CGKR-9 was closely associated with Exophiala spinifera (similarity 99.51%). The molecular analysis indicates that the six DSEs isolates from N. cadamba are new species that have never been identified. The effect of DSEs on the N. cadamba seedlings growth was tested using three isolates (CPGS-1, CKKS-3, and CKKS-5) in the green house. CKKS-5 isolate gave the best N. cadamba seedling growth, with increased seedling height and diameter over the control of 11.6%-20.4% and 8.8%-51.8%, respectively. CKKS-5 increased the seedling biomass of Gowa and Pomalla provenances by 89.1% and 35.8%, respectively, compared to the control. The DSEs inoculant, especially CKKS-5, can positively affect seedling morphophysiological traits. These findings can serve as a basis for developing DSE-based biofertilizer applications to establish plantation forest and restore degraded forests and landscapes.