Arthrobotrys oliogospora BCC 3847 and A. javanica BCC 7879 for management of root-knot nematode (Meloidogyne incognita) in chili pepper

Abstract

Root-knot Nematodes (RKN) is a damaging pest in several crops, including chili pepper, and leads to a severe loss of crop products. Past managements include crop rotation to a different crop such as sunn hemp to limit the spread of RKNs. Biological control using microorganisms is an alternative to control the pest in the field, consequently promoting existing and future markets of organic products.  This study focused on two nematophagous fungi feeding specifically on nematodes, Arthobotrys oligospora BCC 3847 and A. javanica BCC 7879. Scanning electron and compound microscopy showed that both fungi formed various trapping structures, including adhesive net, adhesive knob, constricting ring and adhesive loop. The latter structure is particularly unique for A. oligospora BCC 3847, and has 3-4 hyphal rings arranged in a knot type. Arthobotrys oligospora and A. javanica having these trapping structures caused 34 and 17% mortality of RKNs after 7 days post-inoculation (dpi), respectively. Similar structures were also found in in vitro soil experiment. Viability test indicated that A. oligospora and A. javanica were found in the soil at 1,395 and 92.5 CFU/g during 15-30 dpi. Greenhouse trials demonstrated that inoculation of the two Arthobotrys isolates in the soil 15 days before RKN inoculation decreased the number of root galls by 63-66%, compared with a RKN-infested treatment. Utilization of A. oligospora BCC 3847 can be a preventive protocol for reducing the occurrence of root galls in chili pepper.