Diversity and importance of culturable endophytic fungi of tobacco (Nicotinana tabacum) cultivated in southwestern China

Abstract

Tobacco (Nicotiana tabacum) is one of the most important economic crops in China; however, black shank caused by Phytophthora parasitica is major threat to its cultivation. So far, little is known regarding potential antagonistic effects of endophytes on plant pathogens. A total of 109 culturable endophytic fungal strains were recovered from various tissues of six tobacco cultivars that are commonly cultivated in southwestern China. Morphological and molecular identification showed that these isolates belonged to 18 different genera, including Aspergillus, Chaetomium, Gibellulopsis and Penicillium as predominant genera, which were frequently observed in stem, leaf and root tissues. Among them, only 17 endophytic fungal strains exerted antagonistic effects on P. parasitica in the dual-culture test, and the highest inhibition rate of 73% was produced by a Penicillium janthinellum strain isolated from stem tissue of a cultivar HD. Nevertheless, a field trial revealed that Shannon-Wiener indices were negatively correlated with the disease index and with the incidence of tobacco blank shank in cultivars K326, YUN85, D101 and GUI1, which was further supported by the evaluation of endophytic community similarity. Our results contribute to the understanding of functions and diversity of endophytic fungi, and culturable endophytic fungal strains may be considered potential libraries for screening novel bioactive and effective metabolites to control P. parasitica in crops which requires further research.