Grafting and Rootstock Effects on Pepper (Capsicum annuum L.) Fruit Morphological and Chemical Characteristics Grown Under Plastic House Conditions

The use of grafted plants to limit biotic and abiotic stress, extend production-market windows, and increase productivity is becoming more common worldwide. Still, it is important to verify that grafting does not result in deleterious changes in fruit quality through, for example, unwanted shifts in shoot physiology or the translocation of unwanted substances from root to shoot. Given the origin, makeup, and history of some rootstocks, careful rootstock-scion evaluation and selection and grafted plant management may be needed. The objective of this study was to document the effects of grafting and rootstock-scion combination on major fruit physical and chemical characteristics. Four pepper scions: a) two blocky varieties (‘Toronto’ - yellow and ‘Zedinca’ - red) and b) two elongated varieties (‘Kurtovszka Kàpia’ and ‘Eigman’) were splice-grafted onto five rootstocks (‘TAN TAN (NO: 12G076)’, ‘52-03 RZ’, ‘Budai csipős’, ‘NOURDINE’ and ‘CCA-4758’) varying in fruit shape, size, and other traits. Additionally, the four scion varieties were self-grafted and non-grafted as controls. Plants representing all rootstock-scion combinations and controls were arranged in a randomized complete block design with three replicates, pruned according to local practice, and grown in a passively-controlled, plastic-covered greenhouse in Kafr El-Sheikh, Egypt. All fruits were harvested when fully mature and three to five fruits per plant were randomly selected for further measurement (length, diameter, shape index, flesh thickness, soluble solids content, ascorbic acid content, total titratable acidity). The experiment was repeated in June 2013-May 2014 and June 2014-May 2015. Fruit yield, size, and thickness were larger and values of fruit chemical attributes tended to be greater in grafted than in ungrafted plants. Grafting onto rootstocks also tended to produce larger and thicker fruit with higher chemical attribute values (except titratable acidity) relative to fruit from self- and ungrafted control plants. For example, self-grafted ‘Toronto’ produced fruit with flesh thickness 5.6% higher and soluble solids content 16.6% higher compared to non-grafted plants. Overall, fruit thickness of all rootstock-scion combinations ranged from 0 to 22.4% higher in grafted than non-grafted plants whereas soluble solids content ranged from 22.9% to 35.1% higher in grafted than non-grafted plants.