UPLC-MS/MS analysis and biological activity of the potato cyst nematode hatching stimulant, solanoeclepin A, in the root exudate of Solanum spp

Solanoeclepin B, a hatching factor for potato cyst nematode

The potato cyst nematode (PCN) causes extensive crop losses worldwide. Because the hatching of PCN requires host-derived molecules known as hatching factors (HFs), regulating HF production in host plants may help to control this harmful pest. Solanoeclepin A (SEA), isolated from potato, is the most active HF for PCN; however, its biosynthesis is completely unknown. We discovered a HF called solanoeclepin B (SEB) from potato and tomato root exudates and showed that SEB was biosynthesized in the plant and converted to SEA outside the plant by biotic agents. Moreover, we identified five SEB biosynthetic genes encoding three 2-oxoglutarate-dependent dioxygenases and two cytochrome P450 monooxygenases in tomato. Exudates from tomato hairy roots in which each of the genes was disrupted contained no SEB and had low hatch-stimulating activity for PCN. These findings will help to breed crops with a lower risk of PCN infection.

Plant specialized metabolites in the rhizosphere of tomatoes: secretion and effects on microorganisms

Plants interact with microorganisms in the phyllosphere and rhizosphere. Here the roots exude plant specialized metabolites (PSMs) that have diverse biological and ecological functions. Recent reports have shown that these PSMs influence the rhizosphere microbiome, which is essential for the plant's growth and health. This review summarizes several specialized metabolites secreted into the rhizosphere of the tomato plant (Solanum lycopersicum), which is an important model species for plant research and a commercial crop. In this review, we focused on the effects of such plant metabolites on plant-microbe interactions. We also reviewed recent studies on improving the growth of tomatoes by analyzing and reconstructing the rhizosphere microbiome and discussed the challenges to be addressed in establishing sustainable agriculture.

A Combination of Metabolomics and Machine Learning Results in the Identification of a New Cyst Nematode Hatching Factor

Potato Cyst Nematodes (PCNs) are an economically important pest for potato growers. A crucial event in the life cycle of the nematode is hatching, after which the juvenile will move toward the host root and infect it. The hatching of PCNs is induced by known and unknown compounds in the root exudates of host plant species, called hatching factors (HFs, induce hatching independently), such as solanoeclepin A (solA), or hatching stimulants (HSs, enhance hatching activity of HFs). Unraveling the identity of unknown HSs and HFs and their natural variation is important for the selection of cultivars that produce low amounts of HFs and HSs, thus contributing to more sustainable agriculture. In this study, we used a new approach aimed at the identification of new HFs and HSs for PCNs in potato. Hereto, root exudates of a series of different potato cultivars were analyzed for their PCN hatch-inducing activity and their solA content. The exudates were also analyzed using untargeted metabolomics, and subsequently the data were integrated using machine learning, specifically random forest feature selection, and Pearson’s correlation testing. As expected, solA highly correlates with hatching. Furthermore, this resulted in the discovery of a number of metabolite features present in the root exudate that correlate with hatching and solA content, and one of these is a compound of m/z 526.18 that predicts hatching even better than solA with both data methods. This compound’s involvement in hatch stimulation was confirmed by the fractionation of three representative root exudates and hatching assays with the resulting fractions. Moreover, the compound shares mass fragmentation similarity with solA, and we therefore assume it has a similar structure. With this work, we show that potato likely produces a solA analogue, and we contribute to unraveling the hatch-inducing cocktail exuded by plant roots.

Review of nematode interactions with hemp (Cannabis sativa)

The many decades during which the cultivation of Cannabis sativa (hemp) was strongly restricted by law resulted in little research on potential pathogenic nematodes of this increasingly important crop. The primary literature was searched for hemp-nematode papers, resulting in citations from 1890 through 2021. Reports were grouped into two categories: (i) nematodes as phytoparasites of hemp, and (ii) hemp and hemp products and extracts for managing nematode pests. Those genera with the most citations as phytoparasites were Meloidogyne (root-knot nematodes, 20 papers), Pratylenchus (lesion nematodes, 7) and Ditylenchus (stem nematodes, 7). Several Meloidogyne spp. were shown to reproduce on hemp and some field damage has been reported. Experiments with Heterodera humuli (hop cyst nematode) were contradictory. Twenty-three papers have been published on the effects of hemp and hemp products on plant-parasitic, animal-parasitic and microbivorous species. The effects of hemp tissue soil incorporation were studied in five papers; laboratory or glasshouse experiments with aqueous or ethanol extracts of hemp leaves accounted for most of the remainder. Many of these treatments had promising results but no evidence was found of large-scale implementation. The primary literature was also searched for chemistry of C. sativa roots. The most abundant chemicals were classified as phytosterols and triterpenoids. Cannabinoid concentration was frequently reported due to the interest in medicinal C. sativa. Literature on the impact of root-associated chemicals on plant parasitic nematodes was also searched; in cases where there were no reports, impacts on free-living or animal parasitic nematodes were discussed.