Evaluation of the use of Myracrodruon urundeuva heartwood extracts to protect Moringa oleifera seeds against Nasutitermes corniger attack and improve sanity

Abstract

Moringa oleifera seeds contain several biotechnologically-relevant molecules but are susceptible to termite attack. On the other hand, Myracrodruon urundeuva is strongly resistant to deterioration and it was previously reported the termiticidal activity of preparations from its heartwood against Nasutitermes corniger. This work evaluated whether methanolic (ME) and saline (SE) extracts from M. urundeuva heartwood would be able to protect M. oleifera seeds against N. corniger and improve seed sanity. Nuclear magnetic resonance (NMR) spectroscopy analysis was used to identify the chemical profile of the extracts. Seeds were sprayed for 5 days with ME (SME), SE (SSE), or positive control 1% (v/v) sodium hypochlorite (SSH) and then infested by workers and soldiers. Controls were also performed using seeds not treated with the extracts and infested (ST control) or not (S control). After death of all termites, the seeds were analyzed for vigor (by measurements of electric conductivity in the exudates) and sanity. The representative 1H NMR spectra showed phenolic compounds among the main components of the extracts. Mortality rate of workers and soldiers after 7 days was 100% in SME, SSE, and SSH while it was 50% in ST control. Perforations made by termites were observed in seeds from ST control and SME treatment but not in seeds treated with SE. Analysis of vigor revealed that seeds from control ST or those treated with ME or sodium hypochlorite were damaged by termites while SE promoted protection against N. corniger. Fusarium spp., Penicillium spp. and Trichoderma harziamum were identified in treatments and controls, revealing that the extracts did not improve seed sanity. In conclusion, SE from M. urundeuva heartwood conferred protection against N. corniger attack when sprayed on M. oleifera seeds and this effect can be related with lectin presence.