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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. • RKN differentially affected photosynthesis in grafted and ungrafted plants. • RKN altered leaf gas exchange, disturbing the fruit nutrient composition. • RKN resistance modulated total phenolics and carotenoids, but not total amino acids. • The yield advantage due to grafting was effective only for RKN-infested soils. • New traits are provided that reveal physiological processes that confer RKN tolerance. [ABSTRACT FROM AUTHOR]

Rootstock breeding for vegetable crops includes desirable traits such as compatibility with the scion, increased productivity and quality under stressful environments and improved use of soil, water and fertilizer resources. The effects of three commercial rootstocks (Atlante, Creonte and Terrano) on the agronomical and physiological responses of a commercial sweet pepper variety (cv Herminio) to deficit irrigation (50% of optimal) have been studied. Although the three rootstocks increased total and marketable yield under control and deficit irrigation, Creonte produced the most productive and water use efficient plants, with until 25% more marketable yield than the ungrafted cv Herminio, and about 10% more than the other rootstocks, although in detriment of some chemical fruit quality traits. Moreover, the plants grafted onto Creonte registered the highest photosynthetic activity and leaf water content and more stable leaf area and biomass under water stress, while those parameters were more reduced in the other graft combinations. These Creonte-mediated effects were not related to root biomass (since it was more affected by the stress in this rootstock) but rather to the capacity of maintaining a high reproductive/vegetative ratio, while Atlante is a vigorous vegetative rootstock and Terrano is rather a dwarfing-reproductive rootstock that produces efficient compact plants without negative effects on fruit quality. [ABSTRACT FROM AUTHOR]

Plant growth regulators (PGRs) may have an important role in regulating both yield and fruit quality during the production of sweet pepper in controlled-environment greenhouses, but the uncertainly of results – due to the specificity of the plant response – could limit their use and potential benefits. Therefore, we investigated the effect of the foliar spraying of abcisic acid (ABA), gibberellic acid (GA 3 ) and indole-3-acetic acid (IAA) on fruit colour, concentrations of carbohydrates, ions and amino acids, plant growth and total fruit yield. Although yield was decreased by the GA 3 and ABA treatments, GA 3 augmented plant height and the levels of tyrosine, phosphate, sulphate, iron and phosphorus while decreasing the amounts of glucose and fructose. The foliar applications of IAA did not produce any change when compared with the control plants, while plants treated with ABA had decreased levels of sucrose but higher levels of iron. GA 3 , applied fortnightly, produced a significant improvement in the fruit quality of sweet pepper but did not significantly increase total yield. Further studies will be necessary to determine the best GA 3 concentration and frequency of application, to obtain greater benefits for human consumption this important crop. [ABSTRACT FROM AUTHOR]