Effects of Botanicals on Growth and Phytochemistry of the Nematode-Infected Pelargonium sidoides and GC–MS Profiling of Cucurbita maxima Seeds

Pelargonium sidoides (African geranium) is recognised by South African traditional healers and the pharmaceutical industry for its medicinal properties. Nonetheless, this medicinal herb is highly susceptible to root-knot nematodes ( Meloidogyne species), which limit its growth and medicinal values. Meloidogyne species over the years have been managed with synthetic chemicals. However, the continuous use of these nematicides poses health and environmental threats. Therefore, natural and environment-friendly nematode management strategies are required as alternatives. This study assessed the efficacy of ground or crude extracts of eight different botanicals on vegetative growth and phytochemical accumulation in P. sidoides and their ability to manage Meloidogyne incognita population density. The in vitro study revealed that Cucurbita maxima seed crude extract showed a 100% juvenile mobility inhibition after 72 h at 5 mgmL −1 . Furthermore, P. sidoides seedlings treated with either ground or crude extracts of C. maxima seeds significantly enhanced plant growth and reduced nematode infection. In addition, C. maxima seed extracts significantly increased the Chlorophyll a + b and carotenoid content, which might have improved the photosynthetic capacity of the plants at 10 g and 5 mgmL −1 . A reduction in total phenolics (68 and 64%), superoxide dismutase (1.33 and 1.45 fold) and carbohydrates (1.07 and 1.16 fold) content was recorded for both ground (10 g) and crude (5 mgmL −1 ) extracts. Whereas a significant enhancement (10 g; 1.02 fold) and reduction (5 mgmL −1 ; 1.06 fold) in total protein content was noted when compared to the untreated control. The nematicidal properties observed could be due to the bioactive compounds such as Octadec-9-enoic acid z ( cis ), Octadecanoic acid, 17 octadecynoic acid, octanoic acid, dodecanoic acid, tetradecanoic acid, pentadecanoic acid, hexaonoic acid, 1-octanol, 1-octanal, 2,4-decadienal, (E-E) and 2-decenal, (E) identified and quantified using Gas Chromatography–Mass Spectrometry (GC–MS) analysis.