New traits to identify physiological responses induced by different rootstocks after root-knot nematode inoculation (Meloidogyne incognita) in sweet pepper

Abstract

Root-knot nematodes (RKNs) are one of the major phytopathological problems that limit potential yields in intensive agriculture worldwide. Grafting with resistant rootstocks has been demonstrated to be a viable technique to manage Meloidogyne incognita in several crops (tomato, melon, watermelon, etc.). However, little research has been conducted on sweet pepper (Capsicum annuum L.) grown in greenhouses under Mediterranean-climate conditions. Therefore, we studied a susceptible scion variety (Gacela) grafted onto resistant rootstocks (C19, C25, and RT17), in comparison with ungrafted and self-grafted (GAL) plants. The RKN produced significant root galling in ungrafted and GAL plants; however, RT17 was unaffected. This differing response to infection is discussed from physiological and agronomic perspectives. Thus, following the inoculation of susceptible rootstocks, leaf photosynthesis was impaired by altered stomatal regulation and photochemical efficiency (chlorophyll a fluorescence), which led to unbalanced fruit nutrient concentrations (especially Ca) and to enhanced allocation of carbon from photosynthesis to the production of biochemical defense compounds. Consequently, total phenolics and carotenoids were significantly affected, as was the amino acid profile. These results provide new insights into the traits that can identify RKN-resistant rootstocks, and therefore new tools to induce resistance, while avoiding the use of disinfectants in the soil.