Leaf litter contributes to the obstacles of Cynanchum auriculatum Royle ex Wight continuous cropping

Abstract

Aims To test a hypothesis that fallen leaf litter results in the continuous cropping obstacle (CCO) in Cynanchum auriculatum Royle ex Wight (CA) via growth promotion and invasion reinforcement of soil-borne fungal pathogen. Methods Water extracts of leaf (LE) and root (RE) were compared for their effects on seed germination, seedling growth indices, and plant defense enzymes activities. Besides, the impacts of LE on a fungal pathogen were investigated under laboratory conditions following isolation and verification. Then, the effects of LE on soil microbial communities were determined by using high-throughput sequencing technology. Key Results A fungal strain D1 belonging to Fusarium solani causing root rot disease was isolated and confirmed for its potential contribution to CCO. Both LE and RE inhibited seed germination, seedling growth, and plant defense enzymes activities. Extracts especially LE coupled with D1 aggravated the impacts. Apart from the induction of propagation of D1 in soil, extracts could also promote hypha weight, spore number, and spore germination rate of D1 under the culture conditions. Compared with RE, LE showed more promoting-effects on the pathogenesis-related enzymes activities of D1. Moreover, caffeic acid and ferulic acid were the possible active substances contributing to the events. Besides, not bacterial but fungal community were shifted by LE especially by LE+D1. Conclusions These results suggested that water extract of leaf litter promoted the growth and propagation of strain D1, and enhanced its pathogenicity towards CA, which synthetically contributed to the CCO process.