Potential of herb crude extracts against Thai isolates of Fusarium wilt pathogens

Abstract

Fusarium has damaged a wide host range and economically impacted on many important vegetables and plants in Thailand such as tomato. The goals of this study were to isolate and identify Fusarium spp. from local soil and plant diseased samples, and to study the efficacy of plant crude extracts against Fusarium for sustainable and environmentally friendly control. Forty-four Fusarium isolates from soil and diseased plants from selected agricultural fields in Thailand were characterized by using morphological and phylogenetical analyses. The isolates were assigned to clades with Fusarium reference isolates, and representative eight species were selected including F. chlamydosporum (3 isolates), F. decemcellulare (8), F. falciforme (2), F. incarnatum (7), F. longipes (4), F. proliferatum (3), F. solani (13) and F. verticillioides (4). In 7-day greenhouse experiments, all the Fusarium isolates were pathogenic to cucumber, chili pepper and tomato plants. Plant crude extracts from roselle, clove, turmeric and lemongrass were evaluated for their abilities to inhibit the mycelial growth of 8 representative isolates of Fusarium plant pathogens. Inhibition of all Fusarium isolates was observed at a concentration of 10 g L for both clove and roselle crudes, absolutely. Whilst turmeric crude extract could completely inhibit growth of F. decemcellulare, F. falciforme, F. incarnatum and F. verticillioide. However, lemongrass crude extract was a less potent, showing about 60-80% inhibition. The results indicated that these herb crude extracts deserve further study singly or in combination towards development of natural biofungicides for management of agricultural plant diseases caused by Fusarium.