Solanum palinacanthum Dunal as a potential eggplant rootstock resistant to root-knot nematodes

Eggplant (Solanum melongena) is susceptible to root-knot nematodes (RKN, Meloidogyne spp.), which parasitizes host roots and intakes nutrients from nursing cells called 'giant cells'. Grafting with RKN-resistant rootstock is an effective way to reduce the damage caused by RKN. However, commercially available cultivars of RKN-resistant rootstock for eggplant are limited, and resistance in RKN-resistant plants is sometimes ineffective. A wild eggplant relative, Solanum palinacanthum, was recently found to be resistant against a wide range of Meloidogyne spp. In this study, we assessed the suitability of S. palinacanthum as an eggplant rootstock. First, we checked the grafting compatibility of S. palinacanthum rootstock to scions of commercial cultivars of eggplant. The scions of the eggplants and the rootstock of S. palinacanthum united well, and the grafted plants grew stably, whereas S. palinacanthum was seemingly incompatible with tomato. The grafting of eggplants on S. palinacanthum rootstock significantly suppressed the reproduction of Meloidogyne incognita in a pot experiment. The grafted plants also reduced the population densities of RKN infesting the experimental fields, whereas the grafting did not significantly change the yields. In addition, we measured the contents of representative alkaloids in the fruits of the grafted eggplant, which can be toxic if consumed in large amounts. The results show that the grafting did not make any difference in the contents of alpha-solasonine and alpha-solamargine in the fruit. These results support that S. palinacanthum is a promising eggplant rootstock for Integrated Pest Management (IPM) against RKNs.