Phytohormones Producing Fungal Endophytes Enhance Nutritional Status and Suppress Pathogenic Fungal Infection in Tomato

Two endophytic fungi, namely, Curvularia lunata and Nigrospora sphaerica, were isolated from Melia azedarach, an exotic tree introduced in Egypt from Asia. The fungal endophytes were identified by microscopic examination and molecular identification of nucleotide sequence by DNA sequencing of the purified PCR product. Their antagonistic activities against phytopathogenic fungi and their ability to produce important growth hormone and providing some necessary nutrients for plant growth were also evaluated. Both endophytes exhibited antagonistic activities: C. lunata caused 56 and 50% growth inhibition of Alternaria solani and Fusarium oxysporum, while N. sphaerica suppressed both pathogenic fungi by 63.4 and 56.6%, respectively. N. sphaerica was able to dissolve insoluble phosphorus, produce ammonia, and secrete 40 μg mL-1 of IAA. In contrast, C. lunata failed to dissolve phosphorus, secreted less amount of IAA (3 μg mL-1), but produced ammonia. A greenhouse pot experiment was conducted using phosphorus deficient soil to find out the ability of both endophytes to improve growth of tomato plants. N. sphaerica significantly increased shoot fresh weight by 13 and 22% over C. lunata and the control, respectively. Concerning the nutritional status of tomato plants, both endophytes led to significant increase in nitrogen concentration in shoots when applying 50% of the recommended mineral fertilizer. N. sphaerica enhanced phosphorus concentration in shoots by 13% over the control. Finally, the antifungal activities of both endophytes against F. oxysporum in tomato plants were tested under glasshouse conditions. N. sphaerica was more potent than C. lunata in suppressing 40% of F. oxysporum infection and had positive impact on tomato plant growth. Our study results highlight the potential use of N. sphaerica endophytic fungi as plant biofertilizers and biocontrol agent under glasshouse conditions.